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NFPA 820Standard for

Fire Protection inWastewater Treatment

and CollectionFacilities

1999 Edition

National Fire Protection Association, 1 Batterymarch Park, PO Box 9101, Quincy, MA 02269-9101An International Codes and Standards Organization

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820–1

Copyright © 1999 NFPA, All Rights Reserved

NFPA 820

Standard for

Fire Protection in Wastewater Treatmentand Collection Facilities

1999 Edition

This edition of NFPA 820, Standard for Fire Protection in Wastewater Treatment and CollectionFacilities, was prepared by the Technical Committee on Wastewater Treatment Plants andacted on by the National Fire Protection Association, Inc., at its May Meeting held May 17–20,1999, in Baltimore, MD. It was issued by the Standards Council on July 22, 1999, with an effec-tive date of August 13, 1999, and supersedes all previous editions.

This edition of NFPA 820 was approved as an American National Standard on August 13,1999.

Origin and Development of NFPA 820

The Committee on Wastewater Treatment Plants was organized in 1983 to have primaryresponsibility for documents on safeguarding against the fire and explosion hazards specificto wastewater treatment plants and associated collection systems. This document includes thehazard classification of specific areas and processes. The need to develop NFPA 820 was basedon fire or explosion incidents that, while infrequent, are relatively severe when they do occur.Initial work on the document was begun early in 1985 and resulted in the first edition beingissued in 1990. Extensive changes were made between the first edition and the 1992 edition,with the most notable revision being the document title, which was changed from Recom-mended Practice for Fire Protection in Wastewater Treatment Plants to Recommended Practice for Fire Pro-tection in Wastewater Treatment and Collection Facilities. In addition, the document scope wasrevised to include storm sewer systems and their appurtenances.

In 1995 the document was changed from a recommended practice to a standard, whichcontains mandatory requirements. This was done because NFPA 820 was widely referencedby various jurisdictions.

The 1999 edition of NFPA 820 was changed to include some editorial corrections and tomake the document more enforceable. The definitions were also modified to conform toNFPA’s Manual of Style.

820–2 FIRE PROTECTION IN WASTEWATER TREATMENT AND COLLECTION FACILITIES

1999 Edition

Technical Committee on Wastewater Treatment Plants

Garr M. Jones, Chair Brown and Caldwell, CA [SE]

Alphonse A. Abadir, U.S. Dept. of Labor (OSHA), DC [L]Rep. Sporting Arms & Ammunition Mfrs. Inst., Inc.

John R. Anderson, Marshfield, MA [SE]Alonza W. Ballard, Crouse-Hinds, NY [M]

Rep. Nat’l Electrical Mfrs. Assn.Richard D. Gottwald, Society of the Plastics Industry, DC [M]John N. Harrell, Wilson & Co. Engr & Architects, MO [SE]Gary Hewitt, The Gorman-Rupp Co., OH [M]

Rep. Water & Wastewater Equipment Mfrs. Assn., Inc.

James Retzloff, The Viking Corp., MI [M]Rep. Nat’l Fire Sprinkler Assn.

Joseph P. Sheahan, Metro Water Reclamation District of Greater Chicago, IL [U]

Rep. Assn. of Metropolitan Sewerage AgenciesEdward Sikora, Nat’l Clay Pipe Inst., WI [M]Dao T. Ton, Metropolitan Waste Control Commission, MN [U]James F. Wheeler, U.S. Environmental Protection Agency, DC [E]

Alternates

Josiah W. Beakley, American Concrete Pipe Assn., TX [M](Vot. Alt. to ACPA)

Mark Kreinbihl, The Gorman-Rupp Co., OH [M](Alt. to G. Hewitt)

Ralph S. Thomas, Metropolitan Waste Control Commis-sion, MN [U]

(Alt. to D. T. Ton)

Richard P. Bielen, NFPA Staff Liaison

This list represents the membership at the time the Committee was balloted on the text of this edition. Since that time,changes in the membership may have occurred. A key to classifications is found at the back of this document.

NOTE: Membership on a committee shall not in and of itself constitute an endorsement of the Associationor any document developed by the committee on which the member serves.

Committee Scope: This Committee shall have primary responsibility for documents on criteria for safe-guarding against the fire and explosion hazards specific to wastewater treatment plants and associated col-lection systems, including the hazard classification of specific areas and processes.

CONTENTS 820–3

1999 Edition

Contents

Chapter 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . 820– 41-1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820– 41-2 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820– 41-3 Application . . . . . . . . . . . . . . . . . . . . . . . . . . . 820– 41-4 Metric Units of Measurement . . . . . . . . . . . . 820– 51-5 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . 820– 5

Chapter 2 Collection Systems . . . . . . . . . . . . . . . . . . 820– 92-1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820– 92-2 Design and Construction . . . . . . . . . . . . . . . . 820– 9

Chapter 3 Liquid Stream Treatment Processes . . . 820–173-1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820–173-2 Design and Construction . . . . . . . . . . . . . . . . 820–17

Chapter 4 Solids Treatment Processes . . . . . . . . . . 820–264-1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820–264-2 Design and Construction . . . . . . . . . . . . . . . . 820–26

Chapter 5 Fire and Explosion Prevention andProtection. . . . . . . . . . . . . . . . . . . . . . . . . . 820–34

5-1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820–345-2 Fire Protection Measures . . . . . . . . . . . . . . . 820–345-3 Fire Detection and Alarm Systems . . . . . . . . 820–355-4 Combustible Gas Detection . . . . . . . . . . . . . 820–355-5 Ventilation Monitoring and Signaling

Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820–355-6 Laboratories . . . . . . . . . . . . . . . . . . . . . . . . . . 820–355-7 Special Fire Protection Measures . . . . . . . . . 820–35

Chapter 6 Materials of Construction . . . . . . . . . . . . 820–366-1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820–366-2 Materials Selection . . . . . . . . . . . . . . . . . . . . 820–366-3 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . 820–36

Chapter 7 Ventilation . . . . . . . . . . . . . . . . . . . . . . . . 820–377-1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820–37

7-2 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . 820–387-3 Ventilation Criteria . . . . . . . . . . . . . . . . . . . . 820–38

Chapter 8 Administrative Controls . . . . . . . . . . . . . . 820–408-1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820–408-2 Management Policy and Direction . . . . . . . 820–408-3 Fire Risk Evaluation . . . . . . . . . . . . . . . . . . . 820–408-4 Fire Prevention Program . . . . . . . . . . . . . . . 820–408-5 Water-Based Fire Protection Systems . . . . . 820–408-6 Other Fire Protection and Detection

Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820–408-7 Impairments . . . . . . . . . . . . . . . . . . . . . . . . . 820–408-8 Fire Emergency Plan . . . . . . . . . . . . . . . . . . 820–408-9 Fire Brigades . . . . . . . . . . . . . . . . . . . . . . . . . 820–408-10 Polychlorinated Biphenyls . . . . . . . . . . . . . . 820–408-11 Fire and Explosion Prevention . . . . . . . . . . 820–41

Chapter 9 Referenced Publications . . . . . . . . . . . . . 820–41

Appendix A Explanatory Material . . . . . . . . . . . . . . . 820–42

Appendix B Wastewater Treatment Processes . . . . 820–51

Appendix C Selection of CollectionSystem Materials . . . . . . . . . . . . . . . . . . 820–53

Appendix D Chemical and Fuel Fire/ExplosionHazards . . . . . . . . . . . . . . . . . . . . . . . . . 820–54

Appendix E List of Associations andAbbreviations . . . . . . . . . . . . . . . . . . . . 820–58

Appendix F Referenced Publications . . . . . . . . . . . 820–59

Appendix G Informational Publications . . . . . . . . . 820–59

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820–60


1999 Edition

NFPA 820

Standard for

Fire Protection in Wastewater Treatmentand Collection Facilities

1999 Edition

NOTICE: An asterisk (*) following the number or letter des-ignating a paragraph indicates that explanatory material onthe paragraph can be found in Appendix A.

Information on referenced publications can be found inChapter 9 and Appendix F.

Chapter 1 Introduction

1-1 Scope.

1-1.1 General.

1-1.1.1* This standard provides minimum requirements forprotection against fire and explosion hazards in wastewatertreatment plants and associated collection systems, includingthe hazard classification of specific areas and processes.

1-1.1.2 This standard shall apply to the following:

(1) Collection sewers(2) Trunk sewers(3) Intercepting sewers(4) Combined sewers(5) Storm sewers(6) Pumping stations(7) Wastewater treatment plants(8) Sludge-handling facilities(9) Chemical-handling facilities(10) Treatment facilities(11) Ancillary structures (see definition in Section 1-5)

1-1.1.3 This standard shall not apply to the following:

(1) Collection, treatment, or disposal of industrial wastes ormanufactured by-products that are treated on-site andnot discharged to a publicly or privately operated munic-ipal facility

(2) On-site treatment systems (see definition in Section 1-5)(3) Pressure sewer systems (see definition of Sewer, Pressure in Sec-

tion 1-5)(4) Building drain systems and appurtenances (see definition

in Section 1-5)(5) Industrial sewer systems and appurtenances (see definition

of Sewer, Industrial in Section 1-5)(6) Personnel safety from toxic and hazardous materials or

products of combustion(7) Separate nonprocess-related structures (see definition in

Section 1-5)

1-1.2 Alternative Methods. Nothing in this standard shallprevent or discourage the use of alternative methods, materi-als, practices, or devices, provided technical data are submit-ted to the authority having jurisdiction to demonstrate thatthe alternative method, material, practice, or device is equiva-lent to or superior to the requirements of this standard.

1-1.3 Fire Risk Evaluation. A fire risk evaluation shall be initi-ated early in the facility design or alteration to integrate the

fire prevention and fire protection requirements described inthis document.

1-2 Purpose.

1-2.1 General. The purpose of this standard is to provide areasonable degree of fire and explosion protection for life,property, continuity of mission, and protection of the environ-ment. The intent of this standard is to reduce or eliminate theeffects of fire or explosion by maintaining structural integrity,controlling flame spread and smoke generation, preventingthe release of toxic products of combustion, and maintainingserviceability and operation of the facility.

1-2.2 Toxicity and Biological Hazards. This standard shallapply to the fire and explosion hazards of various substancesassociated with wastewater treatment and conveyance. Thisstandard shall not apply to toxicity and biological hazards.

CAUTION

It is recognized that, from a personnel safety standpoint,toxicity and biological hazards can be present in life-threatening concentrations while no threat of fire or ex-plosion exists.

1-2.3 Ventilation Practices. Ventilation rates required by thisstandard are intended to minimize fire and explosion hazards,which could be insufficient to protect personnel from expo-sure to toxic and biological hazards.

1-2.4 Materials Selection. The fire risk evaluation shall includeevaluation of flame spread, smoke generation, and the impactthat a fire or explosion will have on the structural integrity of thefacility when conditions or applications warrant the selection ofcombustible, limited-combustible, or low flame spread materials.

CAUTION

Since many of the corrosion-resistant materials andcoatings are combustible or limited-combustible andcould represent a considerable fuel load during fireevents, the design and fire risk evaluation shall considerany additional hazards imposed by the use of these ma-terials.

1-3 Application.

1-3.1* New Installations. The requirements of this standardshall apply to new installations. When additions or modifica-tions are made to existing facilities, the modifications shallreflect the requirements of this document. In any event, therequirements of this standard shall be used by owners in a riskassessment to identify the areas of a treatment plant that arevulnerable to fire or other loss.

1-3.2 Document Organization. This document is divided into9 chapters. Chapters 1, 5, 6, 7, 8, and 9 shall apply generally.Chapters 2, 3, and 4 shall apply to specific processes and func-tions. The appendixes provide explanatory information.Appendix A provides explanatory information that is tied toparagraphs in Chapters 1 through 8. Appendix B provides ageneral overview and layout of the unit processes found at atypical wastewater treatment plant, although the arrangementof the unit processes varies from plant to plant.

1-3.3* National Electrical Code® Criteria. This standard is basedon the criteria established by Article 500 of NFPA 70, NationalElectrical Code®, but is not intended to supersede or to conflict

INTRODUCTION 820–5

1999 Edition

with the requirements therein. Once an area is properly classi-fied, NFPA 70 specifies the types of equipment and the wiringmethods that are required.

1-4 Metric Units of Measurement. Metric units of measure-ment used within this standard are in accordance with themodernized metric system known as the International Systemof Units (SI). Values of measurement are followed by anapproximate equivalent value in SI units. For metric conver-sion practices, see ANSI/IEEE 268, Metric Practices.

1-5 Definitions.

Activated Carbon. Adsorptive carbon particles or granulesusually obtained by heating carbonaceous material in theabsence of air or in steam and possessing a high capacity toselectively remove trace and soluble components from solution.

Activated Sludge. A microbial mass grown in aerationtanks, subsequently separated from treated wastewater by sed-imentation, and wasted or returned to the process as needed.

Adjacent. Sharing a common wall, partition, or barrier.

Advanced (Tertiary) Wastewater Treatment. Any physical,chemical, or biological treatment process used to accomplisha degree of treatment greater than that achieved by secondarytreatment. (See also definition of Secondary Wastewater Treatment.)

Anaerobic Digestion. A unit process designed to biologi-cally convert organic matter (sludge) through the action ofmicroorganisms in the absence of elemental oxygen. Processby-products include a gas containing methane, carbon diox-ide, and small quantities of hydrogen sulfide. The digestiontank can have a fixed or floating roof system.

Anaerobic Waste Treatment. A unit process providingtreatment of the liquid stream by action of microorganisms inthe absence of elemental oxygen. Process by-products includea gas containing methane, carbon dioxide, and small quanti-ties of hydrogen sulfide.

Ancillary Structure. An integral part of the wastewater treat-ment or collection process.

Approved.* Acceptable to the authority having jurisdiction.

Authority Having Jurisdiction.* The organization, office, orindividual responsible for approving equipment, materials, aninstallation, or a procedure.

Belt Filter. A sludge-dewatering or -concentrating devicehaving continuous bands or belts of filtering media that passaround rollers and from which the material caught on themedia is usually removed by gravity and pressure.

Building. A structure used or intended for supporting orsheltering any use or occupancy. Personnel could occupybuildings continuously or intermittently.

Building Drain. In plumbing, the part of the lowest hori-zontal piping of a drainage system that receives the dischargefrom soil, waste, and other drainage pipes inside the walls ofthe building and conveys it to the building sewer (house con-nection or lateral).

Centrifuge. A mechanical device in which centrifugal forceis used to separate solids from liquids or to separate liquids ofdifferent densities.

Combustible. Any material that does not comply with the def-initions of either noncombustible material or limited-combustiblematerial.

Combustible Gas Detector. A device used to detect thepresence of flammable vapors and gases and to warn whenconcentrations in air approach the explosive range.

Combustible Liquid.* A liquid having a flash point at orabove 100°F (37.8°C).

Combustible or Explosive Dust. A dust capable of sponta-neous combustion or of exploding or burning when subjectedto a source of ignition.

Compost. The product of thermophilic biological oxida-tion of sludge or other organic materials.

Digester Gas. See definition of Sludge Gas.

Dissolved Air Flotation. A separation process in which airbubbles emerging from a supersaturated solution becomeattached to suspended solids in the liquid undergoing treat-ment and float to the surface.

Domestic Wastewater. Wastewater derived principally fromdwellings, commercial establishments, institutions, and soforth, that could or could not contain small amounts ofgroundwater, surface water, or storm water.

Dry Well. That portion of a pumping station designed toprovide isolation and shelter or accommodations for controlsor equipment associated with pumping of wastewater. Drywells are designed to completely and permanently excludewastewater or wastewater-derived atmospheres. Dry wells cancontain accidental leakage of wastewater from shaft seals oroccasional spills. A dry well could contain equipment such aspumps, motors, fans, wiring, controls, lights and associatedwiring devices, and other accessories.

Drying Beds. Confined, underdrained, shallow layers ofsand or gravel structures on which digested sludge is distrib-uted for draining and air drying. Also applied to underd-rained, shallow, diked earthen structures used for dryingsludge.

Enclosed Space. The interior of any tank or unit processthat is closed to the atmosphere, excluding vents or pressurerelief, or the area around any open tank or unit process sur-rounded by a building or other structure constructed with aroof and solid walls.

Equipment. A general term, including material, fittings,devices, appliances, fixtures, apparatus, and so forth, used aspart of, or in connection with, a mechanical, instrumentation,or electrical installation.

Equipment Enclosure. The housing that covers, protects,or guards a piece of equipment and is not intended for per-sonnel occupancy, but can provide for access to the equip-ment.

Explosionproof Apparatus. Apparatus enclosed in a casethat is capable of withstanding an explosion of a specified gasor vapor that may occur within it and capable of preventingthe ignition of a specified gas or vapor surrounding the enclo-sure by sparks, flashes, or explosion of the gas or vapor within,and that operates at such an external temperature that a sur-rounding flammable atmosphere will not be ignited thereby.

Explosive Limits. The minimum concentration of a gas–airor vapor–air mixture that supports flame, if ignited, is knownas the lower explosive limit (LEL) and the maximum concen-tration of a gas–air or vapor–air mixture that, if ignited, sup-ports flame is known as the upper explosive limit (UEL).Above the UEL and below the LEL, ignition cannot take place.


1999 Edition

(These values might change in oxygen-enriched atmo-spheres.)

Filter (Pressure or Gravity). A device used to pass liquidthrough a medium to remove suspended solids.

Filter Press. A unit process, using a plate and frame press,that is operated hydraulically and mechanically to produce asemisolid sludge cake from a slurry.

Fire Barrier. A continuous vertical or horizontal mem-brane, such as a wall or floor assembly, that is designed andconstructed with a specified fire resistance rating to limit thespread of fire and that also will restrict the movement ofsmoke. Such barriers might have protected openings.

Fire Loading. The amount of combustibles present in agiven area, expressed in Btu/ft2 (kJ/m2).

Fire Prevention. Measures directed toward avoiding theinception of fire.

Fire Protection. Methods of providing for fire control orfire extinguishment.

Fire Resistance Rating. The time, in minutes or hours, thatmaterials or assemblies have withstood a fire exposure asestablished in accordance with the test procedures of NFPA251, Standard Methods of Tests of Fire Endurance of Building Con-struction and Materials. This definition applies to the materialsused in the construction of buildings but does not apply to fur-nishings or the contents of buildings or to the fire hazard eval-uation of materials.

Fire-Rated Penetration Seal. An opening in a fire barrierfor the passage of pipe, cable, duct, and so forth, that has beensealed so as to maintain a barrier rating.

Flammable Liquid.* A Class I liquid having a flash pointbelow 100°F (37.8°C) and having a vapor pressure not exceed-ing 40 psia (2068 mm Hg) at 100°F (37.8°C).

Flash Dryer. A device for vaporizing water from partly dewa-tered and finely divided sludge through contact with a current ofhot gas or superheated vapor that includes a squirrel-cage mill forseparating the sludge cake into fine particles.

Flash Mixer. A device for quickly dispersing chemicals uni-formly throughout a liquid or semisolid.

Flocculator. A unit process for the formation of floc inwastewater.

Fluidized Bed Reactor. A pressure vessel or tank that isdesigned for liquid–solid or gas–solid reactions; the liquid or gasmoves upward through the solids’ particles at a velocity sufficientto suspend the individual particles in the fluid. Applicationsinclude ionexchange, granular activated carbon adsorbers, andsome types of furnaces, kilns, and biological contactors.

Force Main (Pressure Main). A pressure pipe connectingthe pump discharge of a wastewater pumping station underpressure to a point of discharge.

Fuel Gases.* Any gas used as a fuel source, including natu-ral gas, manufactured gas, sludge gas, liquefied petroleumgas–air mixtures, liquefied petroleum gas in the vapor phase,and mixtures of these gases.

Galleries. Long tunnels or walkways connecting separatebuildings or structures. Galleries are generally underground,without windows, and with limited entrances and exits. Galleriesfrequently contain gas or other hazardous material transport sys-

tems, water, wastewater, sludge piping, electrical wiring, andmechanical or electrical equipment.

Gas-Handling Equipment. Equipment, including gas com-pressors, sediment traps, drip traps, gas scrubbers, and pressure-regulating and control valves, used in the removal of gas evolvedfrom the anaerobic digestion process and the compression, con-ditioning, or treatment of this gas. Gas-handling equipmentdoes not include equipment or devices for the utilization of thegas, such as boilers, engines, and waste gas burners.

Grit Chamber. A detention chamber or an enlargement ofa sewer designed to reduce the velocity of flow of the liquid topermit the separation of mineral from organic solids by differ-ential sedimentation.

Hazardous (Classified) Location. Locations are classifieddepending on the properties of the flammable vapors, liquids,or gases, or combustible dusts or fibers that might be presentand the likelihood that a flammable or combustible concen-tration or quantity is present. Each room, section, or area isconsidered individually in determining its classification.

Hazardous Waste. Any waste that is potentially damaging tothe environment or human health because of toxicity, ignitibility,corrosivity, chemical reactivity, or other reason.

Heat Treatment. A sludge-conditioning process combininghigh temperature, time, and pressure to improve the dewater-ability of organic sludge.

Hydrogen Sulfide (H2S). A toxic and lethal gas producedin sewers and digesters by anaerobic decomposition of waste-water solids or other anaerobic wastewater or sludge treatmentprocesses.

Identified. As applied to equipment, recognizable as suit-able for the specific purpose, function, use, environment,application, and so forth, where described in a particular coderequirement. (See definition of Equipment.)

Imhoff Tank. A deep, two-story wastewater treatment tank,consisting of an upper continuous-flow sedimentation cham-ber and a lower sludge digestion chamber. The upper cham-ber floor slopes steeply to trapped slots through which solidscan slide into the lower chamber. The lower chamber receivesno fresh wastewater directly but is provided with gas vents andwith means for drawing digested sludge from near the bottom.

Incineration. Combustion or controlled burning of volatileorganic matter in sludge and solid waste that reduces the vol-ume of the material while producing heat, dry inorganic ash,and gaseous emissions.

Industrial Waste. Generally liquid, solid, or gaseous wastesoriginating from the manufacture of specific products. Suchwastes are usually more concentrated, are more variable incontent and rate, and require more extensive or differenttreatment than municipal waste.

Inspection. A visual examination of a system or portionthereof to verify that it appears to be in operating conditionand is free of physical damage.

Intrinsically Safe. Equipment and wiring that are not capa-ble of releasing sufficient electrical or thermal energy undernormal or abnormal conditions to cause ignition of a specificflammable or combustible atmospheric mixture in its mosteasily ignitible concentration. Abnormal conditions includeaccidental damage to any field-installed wiring, failure of elec-trical components, application of overvoltage, adjustment andmaintenance operations, and other similar conditions. (See

INTRODUCTION 820–7

1999 Edition

ANSI/ISA RP 12.67, Installation of Intrinsically Safe InstrumentSystems in Class I Hazardous Locations.)

Labeled. Equipment or materials to which has been attached alabel, symbol, or other identifying mark of an organization that isacceptable to the authority having jurisdiction and concerned withproduct evaluation, that maintains periodic inspection of produc-tion of labeled equipment or materials, and by whose labeling themanufacturer indicates compliance with appropriate standards orperformance in a specified manner.

Limited-Combustible Material. A building construction mate-rial not complying with the definition of noncombustible materialthat, in the form in which it is used, has a potential heat value notexceeding 3500 Btu/lb (8141 kJ/kg), where tested in accordancewith NFPA 259, Standard Test Method for Potential Heat of BuildingMaterials, and complies with (a) or (b): (a) Materials having astructural base of noncombustible material with a surfacing notexceeding a thickness of 1/8 in. (3.2 mm) that has a flame spreadindex not greater than 50; and (b) Materials, in the form andthickness used, other than as described in (a), having neither aflame spread index greater than 25 nor evidence of continuedprogressive combustion and of such composition that surfacesthat would be exposed by cutting through the material on anyplane would have neither a flame spread index greater than 25nor evidence of continued progressive combustion. Materials sub-ject to increase in combustibility or flame spread index beyond thelimits herein established through the effects of age, moisture, orother atmospheric condition shall be considered combustible.

Listed.* Equipment, materials, or services included in a listpublished by an organization that is acceptable to the authorityhaving jurisdiction and concerned with evaluation of productsor services, that maintains periodic inspection of production oflisted equipment or materials or periodic evaluation of services,and whose listing states that either the equipment, material, orservice meets appropriate designated standards or has beentested and found suitable for a specified purpose.

Low Flame Spread. A material with a flame spread rating of25 or less when classified in accordance with NFPA 255, Stan-dard Method of Test of Surface Burning Characteristics of BuildingMaterials.

Maintenance. Work performed to keep equipment opera-ble or to make repairs.

Maintenance Hole. A structure atop an opening in a gravitysewer, or an opening in the top or side of an enclosed vessel topermit personnel entry. Also referred to as manhole or manway.

Methane (CH4). A colorless, odorless, flammable gaseoushydrocarbon present in natural gas and formed by the anaer-obic decomposition of organic matter. (See also definition ofAnaerobic Digestion.)

Nitrification Tank. A unit process for the oxidation of ammo-nia and nitrogen into nitrates through biochemical actions.

Noncombustible Material. A material that in the form inwhich it is used and under the conditions anticipated will notaid combustion or add appreciable heat to an ambient fire.Materials, when tested in accordance with ASTM E 136, Stan-dard Test Method for Behavior of Materials in a Vertical Tube Furnaceat 750°C (1382°F), and conforming to the criteria contained inChapter 7 of the referenced standard, shall be considered asnoncombustible. This definition applies to the materials usedin the construction of buildings but does not apply to furnish-ings or the contents of buildings or to the fire hazard evalua-tion of materials.

Nonenclosed. Any tank or unit process open to the atmo-sphere or the area around any open tank or unit process housedin a building or other structure constructed with a roof and hav-ing at least 50 percent of the wall area open to the atmosphere.Fixed open louvered panels with effective openings greater than50 percent of the wall area and evenly distributed over the wallarea are considered open to the atmosphere.

On-Site Treatment System. A self-contained system, includ-ing pumping equipment, that provides both treatment anddisposal of wastewater on or immediately adjacent to a singleresidence or group of residences or small commercial estab-lishments.

Oxygen-Enriched Atmosphere. Any atmosphere with anoxygen concentration greater than ambient by volume at nor-mal atmospheric pressure.

Ozonation. The process of contacting wastewater or airwith ozone for the purpose of disinfection, oxidation, or odorcontrol.

Physically Separated. A gastight partition between two adja-cent spaces, or two nonadjacent spaces, with no means of gascommunication between the spaces. Personnel entry to theseparate spaces is by individual, grade-level exterior accessports with no physical connection between the two.

Primary Wastewater Treatment. The first major treatmentin a wastewater treatment plant, generally consisting of one ormore of the following unit processes: screening, comminutionor grinding, grit removal, sedimentation, and skimming.

Pumping Station. A structure that contains pumps andappurtenant piping, valves, and other mechanical and electri-cal equipment for pumping wastewater or other liquid. Alsocalled lift station.

Pyrolysis. The destructive distillation of organic com-pounds in an oxygen-free environment that converts theorganic matter into gases, liquids, and char.

Residential Wastewater. Wastewater derived from areasconsisting of single- and multiple-family residences.

Rotating Biological Contactor (RBC). A unit process forwastewater treatment that is composed of large, closely spacedplastic discs that are rotated about a horizontal shaft (usuallya secondary biological treatment process).

Screening Chamber. A chamber or enlargement of a sewerwhere large suspended or floating solids or material isremoved from raw wastewater by a screen.

Scum or Skimmings. Grease, solids, liquids, and other float-able material removed from settling tanks.

Secondary Wastewater Treatment. Wastewater treatmentunit processes usually consisting of primary treatment and bio-logical oxidation using activated sludge or trickling filtrationfollowed by clarification.

Sedimentation. The unit process of subsidence of sus-pended matter carried by water, wastewater, or other liquidsby gravity. It is usually accomplished by reducing the velocityof the liquid below the point at which it can transport the sus-pended material. Also called settling, it can be enhanced bychemical addition, coagulation, and flocculation.

Separate Nonprocess-Related Structures. Structures thatare physically separated and do not contain any process-related equipment associated with the collection and treat-


1999 Edition

ment of wastewater and solids derived from wastewater treat-ment processes.

Sewer. A single pipe or system of pipes or conduits that car-ries wastewater or drainage water.

Sewer, Branch. A sewer that receives wastewater from a rel-atively small area and discharges into a main sewer servingmore than one branch sewer area.

Sewer, Building. In plumbing, the extension from thebuilding drain to the public sewer or other place of disposal(also called house connection or lateral).

Sewer, Collector. A pipe or conduit that receives wastewa-ter from a relatively small area from two or more lateral sewersand that subsequently discharges into a trunk sewer.

Sewer, Combined. A sewer intended to receive both waste-water and storm or surface water.

Sewer, Industrial. A sewer intended to receive only indus-trial wastewater or other liquid or water-carried wastes. (See alsodefinitions of Sewer, Sanitary; Sewer, Storm; and Sewer, Combined).

Sewer, Interceptor. A sewer that receives dry-weather flowand frequently additional predetermined quantities of stormwater (if from a combined system) from a number of trans-verse sewers or outlets and conducts such waters to a point fortreatment or disposal (also called main sewer).

Sewer, Outfall. A sewer that receives wastewater from a col-lecting system or from a treatment plant and carries it to apoint of final discharge.

Sewer, Pressure. A collection sewer that incorporates awastewater grinder pump or septic tank effluent pump to con-vey wastewater from a single residence or group of residencesor small commercial establishments to a private or publicsewer system or on-site disposal system.

Sewer, Private. A sewer privately owned and used by one ormore properties or owners.

Sewer, Relief. A sewer built to carry the flows in excess ofthe capacity of an existing sewer. Also, a sewer intended tocarry a portion of the flow from a district in which the existingsewers are of insufficient capacity.

Sewer, Residential. A sewer intended to receive only resi-dential wastewater. (See also definitions of Sewer, Combined; Sewer,Sanitary; and Sewer, Storm).

Sewer, Sanitary. A sewer that carries liquid and water-carriedwastes from residences, commercial buildings, industrial plants,and institutions together with minor quantities of storm water, sur-face water, and groundwater that are not admitted intentionally.

Sewer, Storm. A pipe or conduit that carries storm waterand surface water, street wash, and other wash water, or drain-age, but excludes domestic wastewater and industrial wastes(also called storm drain).

Sewer, Trunk. The principal pipe or conduit to which oneor more collector sewers or branch sewers are tributaries (alsocalled main sewer).

Sewer Gas. Gas resulting from decomposition of organicmatter in wastewater in sewers and from the incidental, uncon-trolled release of hydrocarbons or decomposition of organicmatter in stagnant liquid and septic sludge in wastewater treat-ment plants. The gas could contain trace quantities of meth-ane and hydrogen sulfide and could be low in oxygen. It couldbe both a fire and life safety hazard.

Shall. Indicates a mandatory requirement.

Sludge. A semiliquid mass of accumulated settled solidsdeposited from wastewater, raw or treated, in tanks or basins.Also referred to as biosolids.

Sludge Cake. A semisolid product of a sludge-dewateringprocess.

Sludge Dewatering. The process of removing a part of thewater in sludge by any physical or mechanical method withoutheat, such as draining, pressing, vacuum filtration, centrifug-ing, or passing between rollers.

Sludge Gas. Gas obtained as a by-product of the anaerobicsludge digestion unit process from the decomposition oforganic matter. It has a high content of methane, varyingamounts of carbon dioxide and hydrogen sulfide, and a smallamount of nitrogen. It can be both a fire and life safety hazard.

Sludge Gas Vent. A passage to permit the controlledrelease of gases from anaerobic treatment processes or gasstorage facilities.

Sludge Thickening. A sludge treatment process designed toconcentrate wastewater sludges by gravity, mechanical means,or air flotation.

Sludge Treatment. The processing of wastewater sludges torender them stable. This can be done by aerobic or anaerobicdigestion followed by drying on sand beds, filtering and incin-eration, filtering and drying, or wet-air oxidation.

Sludge-Drying Systems. Sludge processes using physical ormechanical evaporation techniques with or without the appli-cation of heat to achieve solids concentrations greater than 85percent.

Standard. A document, the main text of which containsonly mandatory provisions using the word “shall” to indicaterequirements and which is in a form generally suitable formandatory reference by another standard or code or for adop-tion into law. Nonmandatory provisions shall be located in anappendix, footnote, or fine-print note and are not to be con-sidered a part of the requirements of a standard.

Structure. All construction designed to contain or conveywastewater, sludge, sludge gas, piping, or equipment. Struc-tures can provide access but are not intended for continuouspersonnel occupancy.

Through-Penetration Firestop. A specific construction con-sisting of the materials that fill the opening around penetrat-ing items such as cables, cable trays, conduits, ducts, and pipesand their means of support through the wall or floor openingto prevent spread of fire. Its rating is established in accordancewith test procedures in ASTM E 814, Standard Test Method forFire Tests of Through-Penetration Fire Stops.

Trickling Filter. A treatment unit process consisting ofstone, plastic, redwood, or similar media over which wastewa-ter is distributed and through which wastewater trickles to theunderdrains and is treated by the microbial slimes formed onthe surface of the media.

Tunnel. See definition of Galleries.

Utilization Equipment. Equipment that utilizes electricenergy for electronic, electromechanical, chemical, heating,lighting, or similar purposes.

Vacuum Filter. A unit process, used to dewater wastewatersludge, consisting of a cylindrical drum mounted on a hori-

COLLECTION SYSTEMS 820–9

1999 Edition

zontal axis, covered with a media, and subjected to an internalvacuum.

Vault. An enclosed structure, usually underground, used topermit personnel access to various types of equipment andinstrumentation.

Ventilation Rate. Ventilation rate, as used in this docu-ment, is based on air changes per hour and is calculated by theuse of 100 percent outside air for the supply air that isexhausted. Air changes per hour is calculated on the basis ofthe maximum aggregate volume (under normal operatingconditions) of the space to be ventilated.

Volatile Liquid. A liquid that evaporates readily at normaltemperature and pressure.

Wastewater. The spent water of a community. Combinationof the liquid and water-carried wastes from residences, com-mercial buildings, industrial plants, and institutions, togetherwith any groundwater, surface water, and storm water thatmight be present.

Wet Well. That portion of the pumping station that receivesand temporarily stores wastewater for the purpose of pump-ing. A wet well might or might not contain electrical equip-ment such as pumps, motors, fans, wiring and wiring devices,controls, lights, and other accessories.

Chapter 2 Collection Systems

2-1* General. This chapter provides minimum criteria forprotection against fire and explosion hazards in the collectionand transportation of municipal wastewater. This chaptershall not apply to on-site systems, force mains, or those sewersthat principally convey industrial wastes. Table 2-2 summarizesthe various components associated with wastewater collectionand transport systems.

2-2* Design and Construction. The design and constructionof collection system facilities shall conform to Table 2-2.

Table 2-2 Collection Systems

A B C D E F G

Location andFunction

Fire and Explosion

Hazard VentilationExtent of

Classified Area

NEC-Area Electrical Classification

(All Class I, Group D)

Material of Construction for

Buildings or Structures

Fire Protection Measures

1

MATERIALS USED IN REHABILITA-TION, RECON-STRUCTION, OR SLIP-LINING OF SEWERS

NA NA NA NA In accordance with 6-3.1

NA

2

INDUSTRIAL SEWERSewer transporting industrial wastewa-ter only (no sanitary wastewater)

Not included within the scope of this standard

3

STORM SEWERSewer transporting storm water only (no sanitary wastewater)

Possible igni-tion of flamma-ble gases and floating flam-mable liquids

NNV Inside of sewer Division 2 In accordance with 6-3.1

NR

Note: The NR designation in column C indicates that no ventilation requirements are established for the space and,therefore, Table 7-3.1 also has no requirements.A — No ventilation or ventilated at less than 12 air changes per hourB — Continuously ventilated at 12 changes per hour or in accordance with Chapter 7C — Continuously ventilated at 6 air changes per hour or in accordance with Chapter 7CGD — Combustible gas detection systemD — No ventilation or ventilated at less than 6 air changes per hourFDS — Fire detection systemFE — Portable fire extinguisherLC — Limited-combustible materialLFS — Low flame spread materialNA — Not applicableNC — Noncombustible materialNEC — In accordance with NFPA 70, National Electrical CodeNNV — Not normally ventilatedNR — No requirement


1999 Edition

4

STORM WATER PUMPING STA-TION WET WELLSLiquid side of pump-ing station serving only a storm sewersystem


NNV Entire room or space

Division 2 NC, LC, or LFS CGD if enclosed

5

a STORM WATER PUMPING STA-TION DRY WELLSDry side of a pump-ing station serving only a storm sewersystem and physically separated from wet well

Buildup of vapors from flammable or combustibleliquids

D Entire dry well Division 2, or unclassified, if space provided with pressurization in accordance with NFPA 496

NC, LC, or LFS FE

b C Unclassified

6

PRESSURE SEWER (Force main) Sewer under pressure (flooded discharge pipe from pump or tank)


7

BUILDING SEWER (Lateral sewer or drain) Sewer serving a house or single building (plumbing)


8

INDIVIDUAL RESI-DENTIAL SEWER Sewer serving one but not more than five dwellings

NA NNV Within enclosed space

Unclassified NR NR

Table 2-2 Collection Systems (Continued)

A B C D E F G


Fire and Explosion


Classified Area








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9

INDIVIDUAL RESI-DENTIAL PUMP-ING UNITSPumping units serv-ing one but not more than five dwell-ings (e.g., grinder pumps, septic tank effluent pumps, ejec-tor pumps)

NA NNV Within enclosed space

Unclassified NR NR

10

a RESIDENTIAL SEWERSewer transporting primarily residential wastewater


NNV Within enclosed space

Division 2 In accordance with 6-3.1

NR

b B Unclassified

11

a RESIDENTIAL WASTEWATER PUMPING STA-TION WET WELLPumping station transporting prima-rily residential waste-water


A Entire room or space

Division 2 NC, LC, or LFS CGD

b B Unclassified

12

a RESIDENTIAL WASTEWATER PUMPING STA-TION DRY WELLDry side of a pump-ing station transport-ing primarily residential wastewa-ter

Buildup of vapors from flammable or combustible liquids

D Entire room or space

Division 2 NC, LC, or LFS FE

b C Unclassified

13

OUTFALL SEWER Final discharge pipe from a treatment plant, transporting treated wastewater

NA NNV NA Unclassified NR NR


A B C D E F G


Fire and Explosion


Classified Area








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14

a SANITARY SEWER Sewer transporting domestic, commer-cial, and industrial wastewater



NR

b B Division 2

15

a COMBINED SEWER Sewer transporting domestic, commer-cial, and industrial wastewater and storm water



NR

b B Division 2

16

a WASTEWATER PUMPING STA-TION WET WELLSLiquid side of a pumping station serving a sanitary sewer or combined system


A Entire room or space

Division 1 NC, LC, or LFS CGD

b B Division 2

17

a BELOWGRADE OR PARTIALLY BELOWGRADE WASTEWATER PUMPING STA-TION DRY WELL Pump room physi-cally separated from wet well; pumping of wastewater from a sanitary or com-bined sewer system through closed pumps and pipes

Buildup of vapors from flammable or combustible liquids

C Entire space or room

Unclassified NC, LC, or LFS FE

b D Division 2, or unclassified, if spaceprovided withpressurization in accordance with NFPA 496


A B C D E F G


Fire and Explosion


Classified Area








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18

ABOVEGRADE WASTEWATER PUMPING STA-TIONPump room physi-cally separated with no personnel access to wet well; pumping of wastewater from a sanitary or com-bined sewer system through closed pumps and pipes

NA NR NA Unclassified NC, LC, or LFS FE

19

a ABOVEGRADE WASTEWATER PUMPING STA-TIONPump room not physically separated from wet well; pump-ing of wastewater from a sanitary or combined sewer sys-tem through closed pumps and pipes


A Entire space or room

Division 1 NC FE

b B Division 2 NC, LC, or LFS

20

a ODOR-CONTROL SYSTEM AREASAreas physically sep-arated from wet well that house systems handling wet well gases

Leakage and ignition ofsewage gases

D Entire area if enclosed

Division 2 NC, LC, or LFS CGD and FDS

b C, or out-doors

Areas within 3 ft (0.9 m) of leakage sources such as fans, damp-ers, flexible connections, flanges, pres-surized unwelded ductwork, and odor-control vessels

Division 2

c Areas beyond 3 ft (0.9 m)

Unclassified


A B C D E F G


Fire and Explosion


Classified Area








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21

a MAINTENANCE HOLESAccess to sewer for personnel entry


NNV Inside Division 1 In accordance with 6-3.1

NR

b B Division 2

22

a JUNCTION CHAM-BERSStructure where sew-ers intersect


NNV Inside Division 1 In accordance with 6-3.1

NR

b B Open and above grade or inside and ventilated

Division 2

23

INVERTED SIPHONSDepressed section of gravity sewer


NNV Interior of inlet and out-let structures

Division 1 NC NR

24

CATCH BASINS (Curb inlet) Inlet where street water enters a storm or combined sewer


NNV Enclosed space


NR

25

a RESIDENTIAL DIVERSION STRUCTURESEnclosed structures where residential wastewater can be diverted


NNV Enclosed space

Division 2 In accordance with Chapter 6

NR

b B Unclassified

26

a RESIDENTIAL BELOWGRADE VALVE VAULT With an exposed res-idential wastewater surface

Possible igni-tion of gases and floating flammable liq-uids

NNV Enclosed space


NR

b B Unclassified


A B C D E F G


Fire and Explosion


Classified Area








1999 Edition

27

a RESIDENTIAL CONTROLSTRUCTURESEnclosed structures where residential wastewater flow is regulated


A Enclosed space


NR

b B Unclassified

28

a RESIDENTIAL BELOWGRADE METERING VAULT With an exposed res-idential wastewater surface


NNV Enclosed space


NR

b B Unclassified

29

a DIVERSION STRUCTURESEnclosed structures where wastewater can be diverted


NNV Enclosed space


NR

b B Division 2

30

ABOVEGRADE VALVE VAULTPhysically separated from the wet well; valves in vault in closed piping system

NA NR NA Unclassified NC, LC, or LFS NR

31

a BELOWGRADE VALVE VAULTPhysically separated from the wet well and with closed pip-ing system


NNV Enclosed space

Division 2 NC, LC, or LFS NR

b C Unclassified

32

a BELOWGRADE VALVE VAULTWith an exposed wastewater surface

Possible igni-tion of gases and floating flammable liq-uids

NNV Enclosed space

Division 1 NC NR



A B C D E F G


Fire and Explosion


Classified Area








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33

a CONTROL STRUC-TURESEnclosed structures where wastewater or storm water flow is regulated


A Enclosed space


NR

b B Division 2

34

a WASTEWATER HOLDING BASINS Enclosed structures temporarily holding untreated or par-tially treated waste-water


A Enclosed space

Division 1 NC NR


35

WASTEWATER HOLDING BASINS, LINED OR UNLINEDOpen structures holding storm water, combined wastewa-ter, untreated or par-tially treated wastewater

NR NR NR NR NR NR

36

a BELOWGRADE METERING VAULT Physically separated from the wet well and with closed pip-ing system


NNV Enclosed space

Division 2 NC, LC, or LFS NR

b C Unclassified

37

a BELOWGRADE METERING VAULT With an exposed wastewater surface


NNV Enclosed space

Division 1 NC NR


38

COARSE AND FINE SCREEN FACILI-TIES (See Coarse and Fine Screen Facilities in Table 3-2.)


A B C D E F G


Fire and Explosion


Classified Area







LIQUID STREAM TREATMENT PROCESSES 820–17

1999 Edition

Chapter 3 Liquid Stream Treatment Processes

3-1* General. This chapter provides minimum criteria forprotection against fire and explosion hazards associated withliquid stream treatment processes. This chapter shall notapply to treatment systems serving individual structures or

treatment systems principally that treat industrial wastes.Table 3-2 summarizes the various components associated withliquid stream treatment processes.

3-2* Design and Construction. The design and constructionof liquid stream treatment processes shall conform to Table 3-2.

Table 3-2 Liquid Stream Treatment Processes

A B C D E F G

Location and Function

Fire and Explosion

Hazard Ventilation

Extent of Classified

Area1

NEC-Area Electrical Classification (All Class I, Group D)




1

a COARSE AND FINE SCREEN FACILITIESRemoval of screen-ings from raw wastewater


A Enclosed — entire space

Division 1 NC FE, H, and CGD if

enclosedb B Division 2 NC, LC, or LFS

c Not enclosed, open to atmosphere

Within a10-ft (3-m) envelope around equipment and open channel2,3

2

PUMPINGSTATIONS(See CollectionSystems, Table 2-2.)

3

a FLOW EQUAL-IZATION TANKSStorage of raw or partially treated wastewater






Within a10-ft (3-m) envelope around equipment and open channel2,3

Note: The NR designation in column C indicates that no ventilation requirements are established for the space and, therefore, Table 7-3.1 also has no requirements.1Open channels and open structures upstream from the unit processes are to be classified the same as the downstream processes they supply.2The area beyond the envelope is unclassified.3Where liquid turbulence is not induced by aeration or other factors, the following criteria apply: interior of the tank from the minimum operating water surface to the top of the tank wall; envelope 18 in. (0.46 m) above the top of the tank and extending 18 in. (0.46 m) beyond the exterior wall; and envelope 18 in. (0.46 m) above grade extending 10 ft (3 m) horizontally from the exterior tank walls.A — No ventilation or ventilated at less than 12 air changes per hourB — Continuously ventilated at 12 changes per hour or in accordance with Chapter 7C — Continuously ventilated at 6 air changes per hour or in accordance with Chapter 7CGD — Combustible gas detection systemD — No ventilation or ventilated at less than 6 air changes per hourFDS — Fire detection systemFE — Portable fire extinguisherH — Hydrant protection in accordance with 5-2.4LC — Limited-combustible materialLFS — Low flame spread materialNA — Not applicableNC — Noncombustible materialNEC — In accordance with NFPA 70, National Electrical CodeNNV — Not normally ventilatedNR — No requirement


1999 Edition

4

a GRIT REMOVAL TANKSSeparation of grit from raw wastewa-ter






Within a 10-ft (3-m) envelope around equipment and open channel2,3

5

a PRE-AERATION TANKSConditioning of wastewater prior to further treatment



Division 1 NC H and CGD if enclosed



Within a 10-ft (3-m) envelope around equipment and open channel2,3

Table 3-2 Liquid Stream Treatment Processes (Continued)

A B C D E F G


Fire and Explosion

Hazard Ventilation


Area1







1999 Edition

6

a PRIMARY SEDI-MENTATION TANKSSeparation of float-ing or settleable solids from raw wastewater



Division 1 NC H and CGD if enclosed



Interior of the tank from the minimum operating water sur-face to the top of the tank wall; envelope 18 in. (0.46 m) above the top of the tank and extending 18 in. (0.46 m) beyond the exterior wall; enve-lope 18 in. (0.46 m) above grade extending 10 ft (3 m) horizon-tally from the exterior tank walls


A B C D E F G


Fire and Explosion

Hazard Ventilation


Area1







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7

AERATION BASIN, POND, LAGOON, OXI-DATION DITCH, AEROBIC SUS-PENDED GROWTH SYS-TEMS, SEQUENC-ING BATCH REACTORSAerobic treatment of wastewater open to the atmosphere

NA Unclassified (If process is not pre-ceded by primary sedimentation, see Primary Sedimen-tation Tanks in Table 3-2 for classi-fication.)

NR H

8

a ENCLOSED AER-ATION BASIN OR AEROBIC SUS-PENDED GROWTH SYS-TEMSAerobic treatment of wastewater not preceded by pri-mary treatment

Possible igni-tion of flamma-ble gases or floating flam-mable liquids

A Entire enclosed space not routinely entered by personnel

Division 1 NC NR


9

ENCLOSED AER-ATION BASIN OR AEROBIC SUS-PENDED GROWTH SYS-TEMSAerobic treatment of wastewater pre-ceded by primary treatment

NA NR Entire enclosed space

Unclassified NC, LC, or LFS NR


A B C D E F G


Fire and Explosion

Hazard Ventilation


Area1







1999 Edition

10

TRICKLING FIL-TER, BIO-TOWER, AERO-BIC FIXED-FILM SYSTEMSAerobic biological treatment of waste-water

Not normally a significant haz-ard; however, these processes might contain materials that are combustible under certain conditions

NA Unclassified (If unit process is not preceded by pri-mary sedimenta-tion, see Primary Sedimentation Tanks in Table 3-2 for classification.)

NR H

11

a ANAEROBIC TOWERS, ANAER-OBIC FIXED-FILM SYSTEMAnaerobic biologi-cal treatment if sealed from atmo-sphere

Normally pro-duces combusti-ble gas as treatment pro-cess by-product

NA Tank interior Division 1 NC FE and H

b NA 10-ft (3-m) envelope around tank

Division 2 NC, LC, or LFS

12

a GAS-HANDLING SYSTEMS FOR LIQUID TREAT-MENT PRO-CESSES

Combustible gas, often under pressure


Division 1 NC FE and H



Within a 10-ft (3-m) envelope around equipment2

13

OXYGEN AERA-TION TANKSTanks for aerobic treatment of waste-water using high-purity oxygen rather than air

Ignition of flammable gases and float-ing flammable liquids in an oxygen-enriched envi-ronment

NA Enclosed space

Division 2 (If unit process is not pre-ceded by primary sedimentation, see Primary Sedi-mentation Tanks in Table 3-2 for classification.)

Any equip-ment or mate-rial within the reactor space shall be safe for exposure to volatile hydro-carbons in an oxygen-enriched atmo-sphere

Special provi-sion for LEL monitoring and auto-matic isola-tion of equipment and oxygen supply


A B C D E F G


Fire and Explosion

Hazard Ventilation


Area1







1999 Edition

14

INTERMEDIATE, SECONDARY, OR TERTIARY SEDI-MENTATION TANKSSeparate floating and settleable sol-ids from wastewa-ter at various treatment stages

NA NA Unclassified (If unit process is not preceded by pri-mary sedimenta-tion, see Primary Sedimentation Tanks in Table 3-2 for classification.)

NR H

15

FLASH MIXER OR FLOCCULATION TANKSTanks for mixing various treatment chemicals with wastewater


NR H

16

NITRIFICATION AND DENITRIFI-CATION TANKSTertiary treatment of wastewater to reduce or remove nitrogen


NR H


A B C D E F G


Fire and Explosion

Hazard Ventilation


Area1







1999 Edition

17

BREAKPOINT CHLORINATION TANKS AND CHLORINE CON-TACT TANKSApplication of chlorine in aque-ous solution to wastewater

NA NA Unclassified NR (These unit processes use corrosive chemicals that require the use of specific materials of construction. Special consid-eration shall be given to these materials of construction.)

H

18

AMMONIA STRIP-PING TOWERS

(See Trickling Fil-ter in Table 3-2.)

NA NA Unclassified NR (These unit processes use corrosive chemicals. Spe-cial consider-ation shall be given to these materials of construction.)

H

19

INTERMEDIATE OR FINAL PUMP-ING STATIONS Pump(s) at inter-mediate stage or end of the treat-ment process

NA NA Unclassified NR H

20

GRAVITY AND PRESSURE FIL-TERSFiltering of treated wastewater through sand or other media



A B C D E F G


Fire and Explosion

Hazard Ventilation


Area1







1999 Edition

21

CARBON COL-UMN OR TANKSVessels containing carbon for tertiary treatment of waste-water

Significant haz-ard from com-bustible carbon material


22

ON-SITE OZONE GENERATION SYSTEM AND OZONE CON-TACT TANKS Ozone generation and purification for disinfection of wastewater

Similar to oxy-gen generation with addition of being highly corrosive (see Table D-1.1)

NA NA Not covered in this standard

NR NR

23

BACKWASH WATER AND WASTE BACK-WASH WATER HOLDING TANKSTanks for tempo-rary storage of backwash water

NA NA NA Unclassified NR H

24

ULTRAVIOLET DISINFECTION UNIT Disinfection of wastewater by ultraviolet radia-tion


25

EFFLUENT STRUCTURESVarious structures conveying treated wastewater away from treatment processes



A B C D E F G


Fire and Explosion

Hazard Ventilation


Area1







1999 Edition

26

a ODOR-CON-TROL SYSTEM AREAS Areas phys-ically separated from processes that house systems handling flamma-ble gases

Leakage and ignition of flam-mable gases


Division 2

b C Areas within 3 ft (0.9 m) of leakage sources such as fans, dampers, flexible con-nections, flanges, pressurized unwelded ductwork, and odor-control ves-sels

Division 2 NC, LC, or LFS CGD, FDS, and FE


Unclassified


A B C D E F G


Fire and Explosion

Hazard Ventilation


Area1







1999 Edition

Chapter 4 Solids Treatment Processes

4-1* General. This chapter provides minimum criteria forprotection against fire and explosion hazards associated withsolids treatment processes. This chapter shall not apply to thetreatment of solids from industrial waste treatment processes.

Tables 4-2(a) and 4-2(b) summarize the various componentsassociated with solids treatment processes.

4-2* Design and Construction. The design and constructionof solids treatment processes shall conform to Tables 4-2(a) and4-2(b).

Table 4-2(a) Solids Treatment Processes

A B C D E F G


Fire and Explosion

Hazard Ventilation


Area






1

COARSE AND FINE SCREENINGS–HANDLING BUILDINGS Stor-age, conveying, or dewatering of screen-ings (no exposed flow of wastewater through building or area)

NA NR NA Unclassified NC, LC, or LFS H, FE, and FAS

2

GRIT-HANDLING BUILDINGStorage, conveying, and dewatering of heavy small screen-ings and grit (no exposed flow of wastewater through building or area)

NA NR NA Unclassified NC, LC, or LFS H, FE, and FAS

Note: The NR designation in column C indicates that no ventilation requirements are established for the space and, therefore, Table 7-3.1 also has no requirements.1The area beyond the envelope is unclassified.2See NFPA 54, National Fuel Gas Code; NFPA 82, Standard on Incinerators and Waste and Linen Handling Systems and Equipment; NFPA 8501, Standard for Single Burner Boiler Operation; and NFPA 8502, Standard for the Prevention of Furnace Explosions/Implosions in Multiple Burner Boilers.A — No ventilation or ventilated at less than 12 air changes per hourB — Continuously ventilated at 12 air changes per hour or in accordance with Chapter 7C — Continuously ventilated at 6 air changes per hour or in accordance with Chapter 7CGD — Combustible gas detection systemD — No ventilation or ventilated at less than 6 air changes per hourFAS — Fire alarm systemFDS — Fire detection systemFE — Portable fire extinguisherFSS — Fire suppression system (e.g., automatic sprinkler, water spray, foam, gaseous, or dry chemical)H — Hydrant protection in accordance with 5-2.4LC — Limited-combustible materialLFS — Low flame spread materialNA — Not applicableNC — Noncombustible materialNEC — In accordance with NFPA 70, National Electrical CodeNR — No requirement

SOLIDS TREATMENT PROCESSES 820–27

1999 Edition

3

a SCUM-HANDLING BUILDING OR AREAHolding, dewater-ing, or storage

Possible grease or flammable liquids carry-over

A Enclosedspace

Division 2 NC, LC, or LFS H, FE, and CGD if enclosedb B Unclassified


NA

4

a SCUM PITS Buildup of vapors from flammable or combustible liq-uids

A Enclosed —entire space

Division 1 NC H, FE, and CGD if enclosedb B Division 2 NC, LC, or LFS


Within a 10-ft(3-m) envelope around equip-ment and open channel1

5

a SCUM-PUMPING AREASPumping of scum, wet side ofpumping station

Carryover of floating flam-mable liquids


Division 1 NC H, FE, and CGD if enclosedb B Division 2 NC, LC, or LFS


Within a 10-ft(3-m) envelope around equip-ment and open channel1

6

a SCUM-PUMPING AREASPumping of scum, dry side of pumping station

Notsignificant

D Enclosed space Division 2 NC, LC, or LFS FE

b C Unclassified


NA

Table 4-2(a) Solids Treatment Processes (Continued)

A B C D E F G


Fire and Explosion

Hazard Ventilation


Area








1999 Edition

7

SCUM INCINERATORS2 Elimination of scum through burning

Firebox explo-sion from possi-ble carryover of flammable scum

NR Incinerator area if separated from scum storage

Unclassified NC, LC, or LFS FSS (if indoors), H, and FE

8

a SLUDGE THICK-ENER (CLARIFIER) Sludge concentra-tion and removal, gravity, or dissolved air flotation

Possible genera-tion of methane from sludge; carryover of floating flam-mable liquids


Division 1 NC

b B Division 2 NC, LC, or LFS H, FE, and CGD if enclosed


Envelope 18 in. (0.46 m) above water surface and 10 ft (3 m) hori-zontally from wet-ted walls1

9

a SLUDGE PUMPING STATION DRY WELLS Dry side of a sludge pumpingstation

Buildup of methane gas or flammable vapors

D Entire dry well when physically separated from a wet well or sepa-rate structures

Division 2 NC, LC, or LFS H and FE

b C Entire dry well when physically separated from a wet well or sepa-rate structures

Unclassified

10

a SLUDGE STORAGE WET WELLS, PITS, AND HOLDING TANKSRetaining of sludge

Possible genera-tion of methane gas in explosive concentrations; carryover of floating flam-mable liquids


Division 1 NC CGD, H, and FE if tank enclosed in struc-ture




NR


A B C D E F G


Fire and Explosion

Hazard Ventilation


Area








1999 Edition

11

a SLUDGE-BLEND-ING TANKS AND HOLDING WELLS Retaining of sludge with some agitation

Possible genera-tion of methane gas in explosive concentrations; carryover of floating flam-mable liquids


Division 1 NC H, FE, and CGD if tank enclosed in struc-ture




NR

12

DEWATERING BUILDINGS CON-TAINING CENTRI-FUGES, GRAVITY BELT THICKEN-ERS, BELT AND VACUUM FILTERS, AND FILTER PRESSES Removal of water from sludge and the conveyance of sludge or sludge cake

NA NR NA Unclassified NC, LC, or LFS FE, FDS, and FAS

13

INCINERATORS2 AND INCINERA-TOR BUILDINGS Conveying and burn-ing of sludge cake

Firebox explo-sion

NR NA Unclassified NC, LC, or LFS FSS (if indoors), H, and FE

14

HEAT TREAT-MENT UNITS, LOW- OR HIGH-PRESSURE OXIDA-TION UNITS Closed oxidation of sludge

None, other than in high-pressure sys-tems

NR NA Unclassified NC, LC, or LFS H and FE


A B C D E F G


Fire and Explosion

Hazard Ventilation


Area








1999 Edition

15

a ANAEROBIC DIGESTERS, BOTH FIXED ROOF AND FLOATING COVERGeneration of sludge gas from digesting sludge

Leakage of gas from cover, pip-ing, emergency relief valves, and appurte-nances

Not enclosed, open to atmosphere

Tank interior; areas above and around digester cover; envelope 10 ft (3 m) above the highest point of cover, when cover is at its max-imum elevation, and 5 ft (1.5 m) from any wall

Division 1 NC H and FE

b Envelope 15 ft (4.6 m) above Division 1 area over cover and 5 ft (1.5 m) beyond Division 1 area around tank walls

Division 2

c A For digester tanks enclosed in a building: tank inte-rior; entire area inside building

Division 1 NC CGD if enclosed

d B For digester tanks enclosed in a build-ing: tank interior; areas above and around digester cover; envelope10 ft (3 m) above highest point of cover, when cover is at its maximum elevation, and 5 ft (1.5 m) from any wall of digester tank

Division 1 NC CGD if enclosed

e Remaining space in enclosed area



A B C D E F G


Fire and Explosion

Hazard Ventilation


Area








1999 Edition

16

a ANAEROBIC DIGESTER CON-TROL BUILDING Storage, handling, or burning of sludge gas

Leaking and ignition of sludge gas

A Entire building Division 1 NC CGD, H, and FEb B Enclosed areas

that contain gas-handling equip-ment


c C Physically sepa-rated from gas-handling equip-ment

Unclassified

17

a DIGESTER GAS–PROCESSING ROOMSGas compression, handling, andprocessing

Sludge gas igni-tion

A Entire room Division 1 NC CGD, H, and FE


c B Within 5 ft(1.5 m) of equip-ment


18

ANAEROBIC DIGESTER GAS STORAGEStorage of sludge gas

Gas storage pip-ing and han-dling

NNV Within a 10-ft(3-m) envelope of tanks, valves, and appurtenances

Division 1 NC, LC, or LFS H, FE, and CGD

19

CHLORINE OXIDA-TION UNITSChlorine reaction with sludge

Chlorine is a very strong oxi-dizing agent

NR NA Unclassified NR (These unit processes use corrosive chemi-cals that require the use of spe-cific materials of construction. Special consider-ation shall be given to such materials of con-struction.)

H and FE


A B C D E F G


Fire and Explosion

Hazard Ventilation


Area








1999 Edition

20

a UNDERGROUND (PIPING) TUN-NELS CONTAIN-ING NATURAL GAS PIPING OR SLUDGE GASPIPINGTransmission of gas, sludge, water, air, and steam via piping; also might contain power cable and conduit

Ignition of nat-ural gas or sludge gases

D Within 10 ft(3 m) of valves and appurte-nances

Division 1

b D Entire tunnel Division 2 NC, LC, or LFS CGD, FDS, and

FEc C Areas within 10 ft

(3 m) of valves, meters, gas check valves, conden-sate traps, and other piping appurtenances

Division 2

d C Areas beyond10 ft (3 m)

Unclassified

21

UNDERGROUND (PIPING) TUN-NELS NOT CON-TAINING NATURAL GAS PIP-ING OR SLUDGE GAS PIPING Trans-mission of sludge, water, air, and steam piping; also might contain power cable and conduit

NA NR NA Unclassified NC, LC, or LFS FDS and FE

22

a COMPOSTING PILESAerobic sludge reduction

Liberation of ammonia and toxic gas (com-posting materi-als can self-ignite)

D Enclosed area Division 2 NC, LC, or LFS H and FDSb C Unclassified


A B C D E F G


Fire and Explosion

Hazard Ventilation


Area








1999 Edition

23

a IN-VESSEL COM-POSTINGAerobic sludge reduction

Liberation of ammonia and toxic gas (com-posting materi-als can self-ignite)

As required by process

If enclosed, inte-rior of reactor vessel plus a 10-ft (3-m) envelope around reactor vessel

Division 2 NC H and FDS

b Areas beyond10 ft (3 m)

Unclassified

24

a ODOR-CONTROL SYSTEM AREAS Areas physically separated fromprocesses that house systems handling flammable gases

Leakage and ignition of flam-mable gases


Division 2 NC, LC, or LFS CGD, FDS, and

FEb C Areas within 3 ft (1.5 m) of leak-age sources such as fans, dampers, flexible connec-tions, flanges, pressurized unwelded duct-work, and odor-control vessels

Division 2


Unclassified

25

PUMPING OF DRAINAGE FROM DIGESTED SLUDGE-DEWATERINGPROCESSES Pump-ing of centrate, fil-trate, leachate, drying beds, and so forth

NA NR NA Unclassified NC, LC, or LFS H


A B C D E F G


Fire and Explosion

Hazard Ventilation


Area








1999 Edition

Chapter 5 Fire and Explosion Prevention and Protection

5-1* Scope. This chapter establishes minimum requirementsfor overall protection against fire and explosion hazards inwastewater facilities and associated collection systems. The con-ditions created by the existence of gases, liquids, and solids aregrouped into the following two categories:

(1) Flammable/combustible hazards

(2) Safety and health hazards

This standard deals with the flammability aspects of a par-ticular substance, process, or area within wastewater and col-lection facilities. Additional requirements to protect againstsafety and health hazards are contained in NFPA 70E, Standardfor Electrical Safety Requirements for Employee Workplaces, andNFPA 101®, Life Safety Code®.

5-2 Fire Protection Measures.

5-2.1 General.

5-2.1.1 Collection systems, liquid stream treatment processes,and solids-handling processes shall be provided with fire protec-tion for the fire hazards, as described in Tables 2-2, 3-2, 4-2(a),and 4-2(b).

5-2.1.2 Enclosed spaces classified as an explosion hazard areaunder this document shall be physically separated from allunclassified enclosures.

5-2.1.3 In addition to the fire protection specified in Chapter6, buildings, structures, and process elements, under someconditions, shall be provided with automatic-extinguishingsystems in accordance with this chapter.

5-2.2 Automatic Sprinkler Systems. An automatic sprinklersystem where required by this standard or by referenced pub-lications shall conform to NFPA 13, Standard for the Installationof Sprinkler Systems, and shall be approved by the authority hav-ing jurisdiction.

Exception: In certain areas of the wastewater treatment plant, such aschemical storage, underground tunnels or structures, areas where electri-cal hazard is a principal concern, or where water damage would seriouslyimpair the integrity of the treatment plant, other automatic-extinguishingsystems shall be permitted.

5-2.3 Other Automatic-Extinguishing Systems. Where requiredor used in place of automatic sprinkler systems, special hazard–extinguishing systems and nonwater automatic-extinguishingsystems shall be designed, installed, and maintained in accor-dance with the following standards, as applicable:

(1) NFPA 11, Standard for Low-Expansion Foam

(2) NFPA 11A, Standard for Medium- and High-Expansion FoamSystems

(3) NFPA 11C, Standard for Mobile Foam Apparatus

(4) NFPA 12, Standard on Carbon Dioxide Extinguishing Systems

(5) NFPA 12A, Standard on Halon 1301 Fire ExtinguishingSystems

(6) NFPA 15, Standard for Water Spray Fixed Systems for FireProtection

(7) NFPA 16, Standard for the Installation of Foam-Water Sprinklerand Foam-Water Spray Systems

(8) NFPA 17, Standard for Dry Chemical Extinguishing Systems

(9) NFPA 2001, Standard on Clean Agent Fire ExtinguishingSystems

Table 4-2(b) Solids Treatment Processes — Sludge Drying

A B C D E F G


Fire and Explosion


Classified Area


(All Class II, Group G)




1

SLUDGE-DRYING PROCESSES1

Potential for ignition of dust

NR Entire room2 Division 13 NC (Construc-tion in accor-dance with NFPA 68 and NFPA 69)

H, FAS, and FSS (See NFPA 61 and NFPA 69.)

Note: The NR designation in column C indicates that no ventilation requirements are established for the space and,therefore, Table 7-3.1 also has no requirements.1See NFPA 54, National Fuel Gas Code; NFPA 82, Standard on Incinerators and Waste and Linen Handling Systems and Equipment; NFPA 8501, Standard for Single Burner Boiler Operation; and NFPA 8502, Standard for the Prevention of Furnace Explosions/Implosions in Multiple Burner Boilers.2The area beyond the envelope is unclassified.3If acceptable to the authority having jurisdiction, it shall be permitted to be determined in accordance with classifications in NFPA 499, Recommend-ed Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas.FAS — Fire alarm systemFSS — Fire suppression system (e.g., automatic sprinkler, water spray, foam, gaseous, or dry chemical)H — Hydrant protection in accordance with 5-2.4NEC — In accordance with NFPA 70, National Electrical CodeNC — Noncombustible materialNR — No requirement

FIRE AND EXPLOSION PREVENTION AND PROTECTION 820–35

1999 Edition

5-2.4 Water Supplies, Standpipes, Hose Systems, and Hydrants.

5-2.4.1 Water supplies shall be capable of delivering the totaldemand of sprinklers, hose streams, and foam systems. Inareas where there is no public water supply or where the sup-ply is inadequate, treatment plant effluent shall be permittedfor fire protection use. Where connections are made frompublic water supplies, it might be necessary to guard againstpossible contamination of the public supply. The require-ments of the public health authority having jurisdiction shallbe determined and followed.

5-2.4.2 Water supplies and hydrants shall be installed in accor-dance with the following standards, as applicable:

(1) NFPA 22, Standard for Water Tanks for Private Fire Protection(2) NFPA 24, Standard for the Installation of Private Fire Service

Mains and Their Appurtenances(3) NFPA 1142, Standard on Water Supplies for Suburban and

Rural Fire Fighting

5-2.4.3 Standpipes and hose systems shall be installed andinspected in accordance with NFPA 14, Standard for the Instal-lation of Standpipe and Hose Systems.

5-2.4.4 Where fire pumps are used as a separate and solesource of supply, the system shall provide capacity to meetsimultaneous fire water flow requirements for both manualand automatic fire suppression systems. A standby power sup-ply shall be provided. Pumps shall be automatic starting andmanual shutdown. Pumps shall be installed in accordancewith NFPA 20, Standard for the Installation of Centrifugal FirePumps.

5-2.5 Portable Fire Extinguishers. Portable fire extinguishersshall be installed, located, and maintained in accordance withNFPA 10, Standard for Portable Fire Extinguishers.

Exception: With the concurrence of the authority having jurisdiction,the requirement for portable fire extinguishers shall be permitted to bewaived where areas are not commonly occupied.

5-3 Fire Detection and Alarm Systems.

5-3.1 Fire detection and alarm systems for each treatment andcollection facility area shall be provided as identified in Tables2-2, 3-2, 4-2(a), and 4-2(b) or by referenced publications.

5-3.2 Fire detection and alarm systems shall be installed andmaintained in accordance with NFPA 72, National Fire AlarmCode®.

5-4 Combustible Gas Detection.

5-4.1* Combustible gas detectors shall be located in accor-dance with Tables 2-2, 3-2, and 4-2(a).

5-4.2* The selection of combustible gas detector types andtheir placement shall be determined by a qualified person.

5-4.3 Combustible gas detectors shall be listed. The installationof combustible gas detectors shall be in accordance with theirlisting requirements and the manufacturers’ instructions.

5-4.4 Combustible gas detection equipment located in haz-ardous (classified) locations, as defined in accordance withNFPA 70, National Electrical Code, shall be listed for use in suchatmospheres. The detectors shall be set to alarm at 10 percentof the lower explosive limit (LEL) in accordance with the man-

ufacturers’ calibration instructions and shall be connected toalarm signaling systems.Exception: Alarm limits shall be permitted to be set at a higher percent-age of the explosive limit where experience indicates ambient levels aretoo high and spurious alarms are probable.

5-5 Ventilation Monitoring and Signaling Systems.

5-5.1 All continuous ventilation systems shall be fitted withflow detection devices connected to alarm signaling systems toindicate ventilation system failure.

5-5.2 Local and remote alarms for both ventilation system fail-ure and combustible gas detection shall be provided for allhazardous areas classified in accordance with the following:

(1) Article 500 of NFPA 70, National Electrical Code(2) Any space pressurized in accordance with Chapters 2, 3,

and 4(3) Chapter 7 and NFPA 496, Standard for Purged and Pressur-

ized Enclosures for Electrical Equipment

5-5.3* The alarms required in 5-5.2 shall be displayed in accor-dance with Table 5-5.3.

5-5.4 Signaling systems shall be in accordance with therequirements for supervised signaling systems as set forth inNFPA 72, National Fire Alarm Code.

5-6 Laboratories. Fire protection for laboratories shall be inaccordance with NFPA 45, Standard on Fire Protection for Labora-tories Using Chemicals.

5-7 Special Fire Protection Measures.

5-7.1 Fire Protection During Construction. Fire protection mea-sures during construction at both new and existing wastewaterfacilities shall be provided in accordance with NFPA 241, Standardfor Safeguarding Construction, Alteration, and Demolition Operations,and NFPA 395, Standard for the Storage of Flammable and CombustibleLiquids at Farms and Isolated Sites.

5-7.2 Lightning Protection. Lightning protection shall beprovided in accordance with NFPA 780, Standard for the Instal-lation of Lightning Protection Systems.

Table 5-5.3 Ventilation System Alarm Devices for Areas Indicated in 5-5.2

Location/SupervisionAlarm Devices and

Supervision

Entrance(s) to such spaces1 Visual and audible alarms

Within such spaces Visual and audible alarms

Local (within treatmentplant or building)

Visual and audible alarms

Remote (for distantsuper-vision)2

1Where locations are not constantly attended, the use of a nonaudible signal is permissible if a dual light system is used. A dual light system shall include a “go”/“no go” or green light/red light type of warning system instead of the audible alarm.2In situations where this is impractical, a telephone dialer shall be al-lowed to meet the intent of this portion of the table.

Visual and audible alarms


1999 Edition

5-7.3 Drainage.

5-7.3.1 Provisions shall be made in all fire areas of the plantfor removal of all liquids for containment in the fire area with-out flooding of equipment and without endangering otherareas.

5-7.3.2 The provisions for drainage and any associated drain-age facilities shall be sized to simultaneously accommodate allof the following:

(1) The spill of the largest single container of any flammableor combustible liquids in the area

(2) The maximum expected number of fire hose lines [500gal/min (31.5 L/sec) minimum] operating for a mini-mum of 10 minutes

(3) The maximum design discharge of fixed fire suppressionsystems operating for a minimum of 10 minutes

Chapter 6 Materials of Construction

6-1 General.

6-1.1 This chapter provides minimum criteria for selectingmaterials of construction for buildings, structures, and pro-cess elements for protection against fire and explosion inwastewater treatment plants and associated collection systems.In general, materials of construction and interior coatings andfinishes shall provide a maximum degree of fire resistancewith the minimum amount of flame spread and smoke gener-ation associated with a particular application.

6-1.2 Materials shall be selected that reduce or eliminate theeffects of fire and explosion by maintaining structural integ-rity, controlling flame spread and smoke generation, minimiz-ing the release of toxic products of combustion, andmaintaining the serviceability and operation of critical pro-cesses. The criteria for selecting materials of construction isnot intended to provide protection of personnel from the riskof exposure to an asphyxiating or toxic atmosphere generatedduring a fire.Exception: In general, criteria for selecting materials of constructiondo not apply to nonprocess contents of the building, structure, or as-sembly where such contents are not a part of the building, structure, orassembly, including, but not limited to, equipment or equipment enclo-sures, grating, walkways, ladders, railings, weirs, process piping andappurtenances, process media, aeration devices, slide and sluice gates,pump packing and seal material, electrical conduit, hardware, linersfor basins that are open to the atmosphere, or materials used in reha-bilitation or for lining existing sewer pipes.

6-1.3 In areas where corrosive environments are present,including classified areas, special attention shall be given tothe mitigation of corrosion problems in the selection and useof materials for nonstructural assemblies, including the use ofcorrosion-resistant metallic or nonmetallic grating, railings,steps and stairs, conduit, and electric equipment enclosures.

6-2 Materials Selection.

6-2.1 Materials shall be selected based on the criteria for aparticular application. Selection criteria shall include thefollowing:

(1) Structural requirements(2) Location and operating environment(3) Fire rating(4) Flame spread value

(5) Smoke density generation factors(6) Products of combustion(7) Corrosion resistance

6-2.2 For the purpose of this document, materials of construc-tion are divided into the following four basic categories:

(1) Combustible (2) Noncombustible (3) Limited-combustible (4) Low flame spread

6-2.3 Materials of construction used for unit processes locatedin areas with an NFPA 70, National Electrical Code, classificationof Class I, Division 1 or Division 2, and Class II shall be selectedbased on an overall evaluation, including the fire risk of thematerial attributes, the economic impact of replacing the unitprocess, and the potential environmental dangers caused byhaving the unit process out of service for an extended periodof time due to fire or explosion.

6-3 Applications.

6-3.1* Sewers and Appurtenances. Materials of constructionfor sewers and appurtenances such as maintenance holes,junction chambers, and catch basins shall be based on theresults of a written materials risk assessment.

6-3.2 Pumping Facilities. Materials selected for wastewaterpumping facilities shall be in accordance with Table 2-2.

Exception No. 1: When conditions or applications warrant the selec-tion of combustible materials for pumping facilities, consideration toflame spread, smoke generation, corrosion resistance, products of com-bustion, and the impact that a fire or explosion will have on the struc-tural integrity, operability of the pumping facility, and the economicand environmental consequences of having the pumping facility out ofservice shall be included in the fire risk evaluation.Exception No. 2: Small aboveground pumping facilities with a floorarea of 100 ft2 (9.3 m2) or less and physically separated from the wetwell and that do not present a fire hazard to other buildings or struc-tures shall be permitted to be constructed of any appropriate materials.

6-3.3 Buildings and Structures.

6-3.3.1 General. Buildings and structures, including domesand covers, shall be constructed of materials in accordancewith Tables 2-2, 3-2, 4-2(a), and 4-2(b).

Exception No. 1: When conditions or applications warrant the selec-tion of combustible materials for buildings and structures, consider-ation to flame spread, smoke generation, corrosion resistance, productsof combustion, and the impact that a fire or explosion will have on thestructural integrity, operability of the facility, and the economic andenvironmental consequences of having the facility out of service shallbe included in the fire risk evaluation.Exception No. 2: Small aboveground buildings and structures, includ-ing domes and covers, with a floor or surface area of 100 ft2 (9.3 m2) orless and physically separated from other buildings or structures and thatdo not present a fire hazard to other buildings or structures shall be per-mitted to be constructed of any appropriate materials.Exception No. 3: Materials other than those required by Tables 2-2, 3-2,4-2(a), and 4-2(b) shall be permitted in buildings or structures that arefully sprinklered in accordance with NFPA 13, Standard for the Installa-tion of Sprinkler Systems.

6-3.3.2 Critical Unit Processes.

6-3.3.2.1 Buildings and structures, including domes and cov-ers, containing unit processes that are critical to maintaining

VENTILATION 820–37

1999 Edition

the integrity of the treatment plant (e.g., headworks, mainpumping facility, primary clarifiers, etc.), and that if out of ser-vice for even a few hours could permanently or unacceptablydamage the environment or endanger public health by allow-ing the release of raw wastewater or sludge, shall be constructedof materials meeting the definition of noncombustible.Exception: Except as indicated by the Exceptions to 6-3.3.1.

6-3.3.2.2 Where structural assemblies and partitions arerequired in these areas for fire separation in accordance withthe fire risk evaluation, they shall have a minimum 3-hour firerating.

6-3.3.2.3 Nonstructural assemblies such as ventilation ductsand piping shall be constructed of noncombustible, limited-combustible, or low flame spread materials.

6-3.3.3 Essential Unit Processes.

6-3.3.3.1 Buildings or structures, including domes and covers,containing unit processes that are essential to maintaining theintegrity of the treatment plant (e.g., secondary biologicaltreatment, secondary clarifiers, disinfection facilities, etc.),and that if out of service for short periods of time would notpermanently or unacceptably damage the environment orendanger public health but would become critical if contin-ued for several days, shall be constructed of materials meetingthe definitions of noncombustible, limited-combustible, orlow flame spread.Exception: Except as indicated by the Exceptions to 6-3.3.1.

6-3.3.3.2 Where structural assemblies and partitions are usedin these areas for fire separation, they shall have a minimum2-hour fire rating.

6-3.3.3.3* Nonstructural assemblies such as ventilation ductsand piping shall be constructed of noncombustible, limited-combustible, or low flame spread materials.

6-3.3.4 Other Unit Processes.

6-3.3.4.1 Buildings and structures containing unit processes,including sludge-processing operations, that are not critical oressential to maintaining the integrity of the treatment plant,and where being out of service for long periods of time (i.e., aweek or more) would not permanently or unacceptably dam-age the environment or endanger public health, shall be con-structed of materials considered applicable by the authorityhaving jurisdiction.Exception: Except as indicated by the Exceptions to 6-3.3.1.

6-3.3.4.2 Where structural assemblies and partitions are usedin these areas for fire separation, they shall have a minimum1-hour fire rating.

6-3.3.4.3 Nonstructural assemblies such as ventilation ductsand piping shall be constructed of materials meeting the defi-nitions of noncombustible, limited-combustible, or low flamespread.

6-3.3.5 Combustible Gas Generation and Combustion Pro-cesses. Buildings and structures containing unit processesthat generate, process, or utilize combustible gases (e.g.,anaerobic wastewater treatment processes, anaerobic digest-ers, compressors, storage spheres, piping, waste gas burners,gas-fired equipment including sludge incinerators, etc.) shallbe constructed of materials meeting the definition of noncom-bustible.Exception: Except as indicated by the Exceptions to 6-3.3.1.

6-3.3.6 Air Supply and Exhaust. Noncombustible, limited-com-bustible, or low flame spread materials shall be used for air supplyand exhaust systems. Systems supplying or exhausting air at a rategreater than 2000 ft3/min (56.6 m3/min) shall include listedsmoke dampers, listed fire dampers, and smoke detection andshall cause the ventilation system to shut down upon detection ofsmoke. Separate smoke ventilation systems shall be used whereapplicable.

Exception: Smoke venting shall be permitted to be integrated into in-stalled ventilation systems using automatic or manually positioneddampers and motor speed control in accordance with NFPA 90A,Standard for the Installation of Air-Conditioning and VentilatingSystems. Also NFPA 204, Guide for Smoke and Heat Venting, shall bereviewed for further information. Smoke venting also shall be permittedto be accomplished through the use of portable smoke ejectors.

6-3.3.7 Miscellaneous Materials. Cellular or foamed plasticmaterials shall only be used in accordance with NFPA 101, LifeSafety Code. Roof coverings shall be Class A in accordance withNFPA 256, Standard Methods of Fire Tests of Roof Coverings. Metalroof deck construction shall be Class I or shall be fire classified.

Exception: Class II metal roof deck construction shall be permitted inbuildings or structures that are fully sprinklered in accordance withChapter 5.

Chapter 7 Ventilation

7-1 General.

7-1.1 Scope.

7-1.1.1 The minimum criteria for ventilation for protectionagainst fire and explosion of wastewater treatment and pump-ing facilities shall be in accordance with Chapters 2, 3, and 4for the designated electrical classifications. Where this stan-dard requires certain ventilation practices, they are intendedto minimize fire and explosion hazards; these ventilation stan-dards are not intended to protect personnel from the toxiceffects of exposure to gases present. This chapter is limited tothe ventilation of enclosed wastewater pumping and process-related areas. It does not establish criteria applicable to spacesdevoted to administrative areas, laboratories, or other ancil-lary spaces. Because of the unpredictable nature of materialsand events encountered in the operation of wastewater sys-tems, the ventilation criteria established in this standard mightnot be adequate for protection against all hazards that mightbe encountered.

7-1.1.2 Ventilation criteria not addressed by Chapters 2, 3,and 4 shall meet the requirements of Table 7-3.1.

7-1.1.3 This chapter does not apply to at-grade or abovegradeunroofed structures less than 2 ft (0.6 m) deep or 2 ft (0.6 m)to the in-service waterline or to at-grade or abovegrade roofedstructures where the following applies:

(1) The roof is at least 10 ft (3 m) above surrounding finishedgrade

(2) The structure is open on at least three sides

7-1.2 Hazardous classifications as established in Tables 2-2, 3-2,4-2(a), and 4-2(b) shall be permitted to be reduced to a lowerclassification, including unclassified, with positive pressurizationas provided under Article 500 of NFPA 70, National Electrical Code.Positive pressurization shall be as specified in NFPA 496, Stan-dard for Purged and Pressurized Enclosures for Electrical Equipment.


1999 Edition

7-2 Installation.

7-2.1 Ventilation systems serving spaces governed by this stan-dard shall be designed in accordance with NFPA 90A, Standardfor the Installation of Air-Conditioning and Ventilating Systems.

Exception: NFPA 90A shall not apply where superseded by a more re-strictive provision of this standard.

7-2.2 Ventilation systems serving hazardous areas classifiedunder the provisions of Article 500 of NFPA 70, National Elec-trical Code, shall incorporate fans fabricated in accordancewith Air Moving and Control Association (AMCA) Type A orType B spark-resistant construction.

7-2.3 All mechanically ventilated spaces shall be served byboth supply and exhaust fans.

Exception No. 1: For covered process facilities that are not routinelyentered by personnel and where mechanically ventilated, the space ispermitted to be ventilated by exhaust fans only. In determining the areaclassification, the induced supply (outside) air shall meet the ventila-tion rate specified in the applicable chapter.

Exception No. 2: Abovegrade spaces with floor areas of 100 ft2 (9.3 m2)or less meeting the requirements of Exception No. 2 to 6-3.3.1 shall be per-mitted to be ventilated by a supply fan only.

7-2.4 Ventilation systems serving unclassified areas adjacentto classified areas shall maintain a differential pressure relativeto ambient air pressure of 0.1 in. water column (25 Pa) underall operating conditions.

7-2.5 Ventilation systems serving classified areas shall maintaina differential pressure relative to ambient air pressure of −0.1 in.water column (−25 Pa) under all operating conditions.

7-2.6 Ventilation systems for hazardous areas that aredesigned to operate intermittently or only when the space isoccupied shall not be permitted for the purpose of downgrad-ing the electrical classification of areas. (See Chapters 2, 3, and4 for further information.)

7-2.7 Air shall be introduced into and exhausted from suchspaces in a manner that will encourage scavenging of all por-tions of the spaces to prevent short-circuiting and to promotethe effective removal of both heavier- and lighter-than-airgases and vapors.

7-2.8 Ventilation systems shall not transfer air between unclas-sified interior spaces and classified interior spaces.

7-2.9 Ventilation systems serving areas governed by this stan-dard shall receive power from electrical equipment thatreceives power from a primary power source and that also has

the means to accept power from alternate power sources. Mini-mum requirements for the means to accept the alternate sourceof power include connectors that are designed to connect todevices such as standby generators, portable generators, unin-terruptible power supplies, and so forth. Automatic or manualswitching to a permanent alternate source of power is also per-mitted. Power failure of the primary source shall be alarmed.

7-3 Ventilation Criteria.

7-3.1 Ventilation rates are based on air changes per hour andshall be calculated on the basis of the maximum aggregate vol-ume — under normal operating conditions — of the space tobe ventilated. Air changes per hour shall be based on 100 per-cent outside supply air, which shall be exhausted. Ventilationrates shall conform to those listed in Table 7-3.1 in order toobtain the lowest area electrical classification possible inaccordance with NFPA 70, National Electrical Code.

7-3.2 Dual ventilation rates for NFPA 70, National ElectricalCode, Class I, Division 1 and Division 2 areas shall be permittedunder the provisions of this standard, provided the following.

(a) The low ventilation rate is not less than 50 percent ofthat specified in Table 7-3.1.

(b) The low ventilation rate is in operation only if the sup-ply air temperature is 50°F (10°C) or less.

(c) The high ventilation rate is not less than that specifiedin Table 7-3.1.

(d) The high ventilation rate is in operation whenever thesupply air temperature is above 50°F (10°C), whenever theventilated space is occupied, or whenever activated byapproved combustible gas detectors set to function at 10 per-cent of the lower explosive limit (LEL). The high ventilationrate is in operation whenever the supply air temperature isabove 50°F (10°C), whenever the ventilated space is occupied,or whenever activated by approved combustible gas detectorsset to function at 10 percent of the lower explosive limit.

7-3.3* Recirculation of up to 75 percent of the exhaust airflowrate for unclassified areas shall be permitted provided the fol-lowing.

(1) The recirculated air and outside airflow rate total is notless than 6 air changes per hour.

(2) Recirculation does not occur during occupancy.(3) Recirculation does not occur whenever a combustible gas

detector senses a lower explosive limit of 10 percent orgreater.

VENTILATION 820–39

1999 Edition

Table 7-3.1 Minimum Ventilation Rates

Ventilation Rate, Air Changes per Hour, or Velocity

Description Class I, Division 1 Class I, Division 2 Unclassified

1 Wet wells, screen rooms, and other enclosed spaces with wastewater exposed to the room atmosphere

<12 air changes per hour ≥12 air changes per hour

2 Belowgrade spaces such as dry wells, equipment rooms, tunnels, orgalleries:

(a) With equipment using or processing flammable gas

<12 air changes per hour or <74-ft/min (22.2-m/min) velocity in tunnels or gal-leries

≥12 air changes per hour or ≥74-ft/min (22.2-m/min) velocity in tunnels orgalleries

(b) With gas piping <6 air changes per hour or <37-ft/min (11-m/min) velocity in tunnels orgalleries

≥6 air changes per hour or ≥37-ft/min (11-m/min) velocity in tunnels orgalleries

(c) Without gas piping NR for tunnels and galleries <6 air changes per hour for dry wells. NR for tunnels and galleries

≥6 air changes per hour for dry wells. NR for tunnels and galleries

3 Abovegrade spaces such as equipment rooms and galleries:

(a) With equipment using or processing flammable gas

<12 air changes per hour or <74-ft/min (22.2-m/min) velocity for galleries

≥12 air changes per hour or ≥74-ft/min (22.2-m/min) velocity in galleries

(b) With gas piping <6 air changes per hour or <37-ft/min (11-m/min) velocity in galleries

>6 air changes per hour or >37-ft/min (11-m/min) velocity in galleries

(c) Without gas piping NR for galleries NR for galleries NR for galleries

Note: NR — No requirement.


1999 Edition

Chapter 8 Administrative Controls

8-1 General. This chapter establishes procedures and con-trols necessary for the execution of the fire prevention and fireprotection activities and practices for wastewater treatmentand collection facilities.

8-2 Management Policy and Direction.

8-2.1* Management shall establish a policy and institute a fireprevention and protection program at each facility.

8-2.2 Combustible materials shall not be stored in areas usedfor the storage of toxic or reactive chemicals.

8-3* Fire Risk Evaluation. A complete fire risk evaluationshall be performed during the initial design process.

8-4 Fire Prevention Program. Each plant shall establish afire prevention program. This program shall include all ofthe following:

(1) Fire safety information for all employees and contractors.This information shall include, as a minimum, familiar-ization with fire protection equipment and procedures,plant emergency alarms and procedures, and how toreport a fire.

(2) Documented plant inspections, including provisions forhandling remedial actions to correct conditions thatincrease fire hazards.

(3) Description of the general housekeeping procedures andthe control of transient combustibles, including controlof such materials stored in areas containing toxic or reac-tive chemicals.

(4) Control of flammable and combustible liquids and gasesin accordance with NFPA 30, Flammable and CombustibleLiquids Code, and NFPA 54, National Fuel Gas Code.

(5) Control of ignition sources to include smoking, grinding,welding, and cutting in accordance with NFPA 51B, Stan-dard for Fire Prevention During Welding, Cutting, and OtherHot Work.

(6) Fire prevention surveillance in accordance with NFPA601, Standard for Security Services in Fire Loss Prevention.

(7) *Fire report, including an investigation and a statementon the corrective action to be taken.

8-5 Water-Based Fire Protection Systems.

8-5.1 Water-based fire protection systems include fire sprin-kler systems, standpipe and hose systems, water spray fixed sys-tems, and foam–water sprinkler systems. Also included are thewater supplies that are part of these systems, such as privatefire service mains and appurtenances, fire pumps and waterstorage tanks, and valves that control system flow.

8-5.2 All water-based fire protection systems shall be installedin accordance with the manufacturers’ specifications and theNFPA standards referenced throughout this document assummarized in Chapter 9.

8-5.3 All water-based fire protection systems shall be inspected,tested, and maintained in accordance with NFPA 25, Standard forthe Inspection, Testing, and Maintenance of Water-Based Fire ProtectionSystems.

8-6 Other Fire Protection and Detection Systems.

8-6.1 All other fire protection and detection systems shall beinstalled in accordance with the manufacturers’ specifications

and the NFPA standards referenced throughout this docu-ment as summarized in Chapter 9.

8-6.2* All other fire protection and detection systems shall beinspected, tested, and maintained in accordance with theNFPA standards in Chapter 9.

8-6.3 Other fire protection system equipment that is notaddressed by an NFPA standard as referenced in Chapter 9(e.g., combustible gas detectors, radio communications equip-ment, and flame arresters or flame checks) shall be inspected,tested, and maintained in accordance with the manufacturers’specifications.

8-7* Impairments.

8-7.1 A written procedure in accordance with NFPA 25, Stan-dard for the Inspection, Testing, and Maintenance of Water-Based FireProtection Systems, shall be established to address impairmentsof all water-based fire protection systems.

8-7.2 A written procedure shall be established to addressimpairments to other fire protection systems and plant systemsthat have an impact on the level of fire hazard (e.g., dust col-lection systems, HVAC systems). These procedures shallinclude the following:

(1) Identify equipment not available for service(2) Identify personnel to be notified (e.g., plant fire brigade

chief, public fire department)(3) Increase fire surveillance as needed [See 8-4(6) for further

information.]

8-7.3 Following repairs, tests shall be conducted on allaffected systems to ensure proper operation.

8-7.4 Following restoration, all parties previously notified ofthe impairment shall be notified of the completion of repairs.

8-8 Fire Emergency Plan. A written fire emergency plan shallbe developed. This plan shall include the following:

(1) Response to fire alarms and fire system supervisoryalarms

(2) Notification of personnel identified in the plan(3) Evacuation from the fire area of employees not directly

involved in fire-fighting activities(4) Coordination with security forces or other designated

personnel to admit the public fire department and tocontrol traffic and personnel

(5) Fire extinguishment activities(6) Operators’ duties during fire emergencies in critical

areas(7) Approved breathing apparatus to be provided in critical

areas

8-9* Fire Brigades.

8-9.1* If a fire brigade is provided, its organization and train-ing shall be identified in written procedures.

8-9.2 Arrangements shall be made to allow rapid entry intothe plant by the municipal fire department, police depart-ment, or other authorized personnel in the case of fire orother emergency. Plant emergency organizations, where pro-vided, shall be instructed and trained in accordance withNFPA 600, Standard on Industrial Fire Brigades.

8-10* Polychlorinated Biphenyls. If polychlorinated biphe-nyls (PCBs) are contained within the wastewater treatmentplant, the owner and the local fire officials shall prepare a con-

REFERENCED PUBLICATIONS 820–41

1999 Edition

tingency plan to protect the plant and the collection systemfrom possible contamination in the event that the PCBs orcombustion products are leaked or washed into the drainsduring a fire.

8-11 Fire and Explosion Prevention. The principal controlprocedures used to minimize potential fire and explosion inci-dents at wastewater treatment plants shall include the following:

(1) Ventilation (See Chapter 7 for further information.)(2) Education (See NFPA 1, Fire Prevention Code, for further infor-

mation.)(3) Risk management and property conservation programs(4) Procedures for permitting hotwork(5) Selection of materials of construction (See Chapter 6 for fur-

ther information.)(6) Selection of equipment

8-11.1 Control of Hazardous Source. In-house training pro-grams [e.g., plant emergency organizations (PEO) and house-keeping or maintenance] that will provide information tounderstand, identify, prevent, and handle hazardous sourcesand situations related to potential fire, explosion, and toxicityproblems shall be established for all personnel. Close liaisonshall be implemented between the local fire department,including other authorized emergency personnel, and waste-water treatment plant safety personnel, so that mutuallyapproved emergency procedures, including familiarity withthe plant, are established.

8-11.2 Control of Ignition Sources.

8-11.2.1 Personnel involved shall be educated in the condi-tions for and sources of ignition of special hazards and shall betrained for the safe operation of processes. [See 8-4(6) for furtherinformation.]

8-11.2.2 All personnel shall be trained to report faulty equip-ment, worn static bonding lines, improperly stored chemicals,and other items needing correction.

8-11.3 Hotwork Permits. Welding, cutting, and similar spark-producing operations shall not be permitted until a writtenpermit authorizing such work has been issued. The permitshall be issued by a person in authority following inspection ofthe area to ensure that the precautions have been taken andwill be followed until the job is completed. (See NFPA 51B, Stan-dard for Fire Prevention During Welding, Cutting, and Other HotWork, for further information.)

Chapter 9 Referenced Publications

9-1 The following documents or portions thereof are refer-enced within this standard as mandatory requirements andshall be considered part of the requirements of this standard.The edition indicated for each referenced mandatory docu-ment is the current edition as of the date of the NFPA issuanceof this standard. Some of these mandatory documents mightalso be referenced in this standard for specific informationalpurposes and, therefore, are also listed in Appendix F.

9-1.1 NFPA Publications. National Fire Protection Associa-tion, 1 Batterymarch Park, P.O. Box 9101, Quincy, MA 02269-9101.

NFPA 1, Fire Prevention Code, 1997 edition.NFPA 10, Standard for Portable Fire Extinguishers, 1998 edition.NFPA 11, Standard for Low-Expansion Foam, 1998 edition.

NFPA 11A, Standard for Medium- and High-Expansion FoamSystems, 1999 edition.

NFPA 11C, Standard for Mobile Foam Apparatus, 1995 edition.NFPA 12, Standard on Carbon Dioxide Extinguishing Systems,

1998 edition.NFPA 12A, Standard on Halon 1301 Fire Extinguishing Sys-

tems, 1997 edition.NFPA 13, Standard for the Installation of Sprinkler Systems,

1999 edition.NFPA 14, Standard for the Installation of Standpipe and Hose

Systems, 1996 edition.NFPA 15, Standard for Water Spray Fixed Systems for Fire Protec-

tion, 1996 edition.NFPA 16, Standard for the Installation of Foam-Water Sprinkler

and Foam-Water Spray Systems, 1999 edition.NFPA 17, Standard for Dry Chemical Extinguishing Systems,

1998 edition.NFPA 20, Standard for the Installation of Centrifugal Fire

Pumps, 1999 edition.NFPA 22, Standard for Water Tanks for Private Fire Protection,

1998 edition.NFPA 24, Standard for the Installation of Private Fire Service

Mains and Their Appurtenances, 1995 edition.NFPA 25, Standard for the Inspection, Testing, and Maintenance

of Water-Based Fire Protection Systems, 1998 edition.NFPA 30, Flammable and Combustible Liquids Code, 1996 edition.NFPA 45, Standard on Fire Protection for Laboratories Using

Chemicals, 1996 edition.NFPA 51B, Standard for Fire Prevention During Welding, Cut-

ting, and Other Hot Work, 1999 edition.NFPA 54, National Fuel Gas Code, 1999 edition.NFPA 61, Standard for the Prevention of Fires and Dust Explo-

sions in Agricultural and Food Products Facilities, 1999 edition.NFPA 68, Guide for Venting of Deflagrations, 1998 edition.NFPA 69, Standard on Explosion Prevention Systems, 1997 edition.NFPA 70, National Electrical Code®, 1999 edition.NFPA 70E, Standard for Electrical Safety Requirements for

Employee Workplaces, 1995 edition.NFPA 72, National Fire Alarm Code®, 1999 edition.NFPA 82, Standard on Incinerators and Waste and Linen Han-

dling Systems and Equipment, 1999 edition.NFPA 90A, Standard for the Installation of Air- Conditioning

and Ventilating Systems, 1999 edition.NFPA 101®, Life Safety Code®, 1997 edition.NFPA 204, Guide for Smoke and Heat Venting, 1998 edition.NFPA 241, Standard for Safeguarding Construction, Alteration,

and Demolition Operations, 1996 edition.NFPA 251, Standard Methods of Tests of Fire Endurance of Build-

ing Construction and Materials, 1999 edition.NFPA 255, Standard Method of Test of Surface Burning Charac-

teristics of Building Materials, 1996 edition.NFPA 256, Standard Methods of Fire Tests of Roof Coverings,

1998 edition.NFPA 259, Standard Test Method for Potential Heat of Building

Materials, 1998 edition.NFPA 395, Standard for the Storage of Flammable and Combusti-

ble Liquids at Farms and Isolated Sites, 1993 edition.NFPA 496, Standard for Purged and Pressurized Enclosures for

Electrical Equipment, 1998 edition.NFPA 499, Recommended Practice for the Classification of Com-

bustible Dusts and of Hazardous (Classified) Locations for ElectricalInstallations in Chemical Process Areas, 1997 edition.

NFPA 600, Standard on Industrial Fire Brigades, 1996 edition.


1999 Edition

NFPA 601, Standard for Security Services in Fire Loss Prevention,1996 edition.

NFPA 780, Standard for the Installation of Lightning ProtectionSystems, 1997 edition.

NFPA 1142, Standard on Water Supplies for Suburban andRural Fire Fighting, 1999 edition.

NFPA 2001, Standard on Clean Agent Fire Extinguishing Sys-tems, 1999 edition.

NFPA 8501, Standard for Single Burner Boiler Operation, 1997edition.

NFPA 8502, Standard for the Prevention of Furnace Explosions/Implosions in Multiple Burner Boilers, 1999 edition.

9-1.2 Other Publications.

9-1.2.1 ANSI Publications. American National Standards Insti-tute, Inc., 11 West 42nd Street, 13th floor, New York, NY 10036.

ANSI/IEEE 268, Metric Practices, 1992.ANSI/ISA RP 12.67, Installation of Intrinsically Safe Instru-

ment Systems in Class I Hazardous Locations, 1967.

9-1.2.2 ASTM Publications. American Society for Testing andMaterials, 100 Barr Harbor Drive, West Conshohocken, PA19428-2959.

ASTM E 136, Standard Test Method for Behavior of Materials ina Vertical Tube Furnace at 750°C (1382°F), 1994.

ASTM E 814, Standard Test Method for Fire Tests of Through-Penetration Fire Stops, 1988 (Rev. B-94).

Appendix A Explanatory Material

Appendix A is not a part of the requirements of this NFPA docu-ment but is included for informational purposes only. This appendixcontains explanatory material, numbered to correspond with the appli-cable text paragraphs.

A-1-1.1.1 Other NFPA standards should be consulted for addi-tional requirements relating to wastewater treatment and col-lection facilities.

A-1-3.1 In existing facilities, it is not always practical to strictlyapply the provisions of this standard. Physical limitationscould necessitate disproportionate effort or expense with littleincrease in fire protection. In such cases, the authority havingjurisdiction should be satisfied that reasonable fire protectionis ensured.

In existing facilities, it is the intent that any condition thatrepresents a serious threat to fire protection should be miti-gated by application of appropriate safeguards. It is not theintent to require modification for conditions that do not rep-resent a significant threat to fire protection, even though suchconditions are not literally in conformance with the fire pro-tection requirements.

A-1-3.3 For additional information, see NFPA 497, Recom-mended Practice for the Classification of Flammable Liquids, Gases, orVapors and of Hazardous (Classified) Locations for Electrical Instal-

lations in Chemical Process Areas, and NFPA 499, RecommendedPractice for the Classification of Combustible Dusts and of Hazardous(Classified) Locations for Electrical Installations in Chemical ProcessAreas. While some of these recommended practices are notapplicable to wastewater treatment facilities, both documentsprovide useful information.

A-1-5 Approved. The National Fire Protection Associationdoes not approve, inspect, or certify any installations, proce-dures, equipment, or materials; nor does it approve or evalu-ate testing laboratories. In determining the acceptability ofinstallations, procedures, equipment, or materials, the author-ity having jurisdiction may base acceptance on compliancewith NFPA or other appropriate standards. In the absence ofsuch standards, said authority may require evidence of properinstallation, procedure, or use. The authority having jurisdic-tion may also refer to the listings or labeling practices of anorganization that is concerned with product evaluations and isthus in a position to determine compliance with appropriatestandards for the current production of listed items.

A-1-5 Authority Having Jurisdiction. The phrase “authority hav-ing jurisdiction” is used in NFPA documents in a broad manner,since jurisdictions and approval agencies vary, as do their respon-sibilities. Where public safety is primary, the authority havingjurisdiction may be a federal, state, local, or other regionaldepartment or individual such as a fire chief; fire marshal; chiefof a fire prevention bureau, labor department, or health depart-ment; building official; electrical inspector; or others having stat-utory authority. For insurance purposes, an insurance inspectiondepartment, rating bureau, or other insurance company repre-sentative may be the authority having jurisdiction. In many cir-cumstances, the property owner or his or her designated agentassumes the role of the authority having jurisdiction; at govern-ment installations, the commanding officer or departmentalofficial may be the authority having jurisdiction.

A-1-5 Combustible Liquid. See NFPA 30, Flammable and Com-bustible Liquids Code.

A-1-5 Flammable Liquid. See NFPA 30, Flammable and Com-bustible Liquids Code.

A-1-5 Fuel Gases. See NFPA 54, National Fuel Gas Code.

A-1-5 Listed. The means for identifying listed equipmentmay vary for each organization concerned with product evalu-ation; some organizations do not recognize equipment aslisted unless it is also labeled. The authority having jurisdictionshould utilize the system employed by the listing organizationto identify a listed product.

A-2-1 Additional information on sources of hazards, sourcesof ignition, and mitigation measures associated with the col-lection and transmission of municipal wastewater is containedin Appendix D.

A-2-2 See Figures A-2-2(a) through (g), which provide exam-ples for Table 2-2.

APPENDIX A 820–43

1999 Edition

Figure A-2-2(a) Wet well or basin serving a storm sewer; illustration of Table 2-2, row 4.

Figure A-2-2(b) Wet well or basin serving a residential sewer; illustra-tion of Table 2-2, row 11.

Figure A-2-2(c) Wet well or basin serving separate or combined sani-tary sewer; illustration of Table 2-2, rows 16 and 34.

Wet well or basinVentilation NNV

3-ft (0.9-m) radius from vent (Div. 2)

Grade

Division 1 Division 2 Unclassified


Wet well or basinVentilation B

Grade

Wet well or basinVentilation A


3-ft (0.9-m) radiusfrom vent (Div. 1)


3 ft(0.9 m)

1.5 ft (0.5 m)

Grade

Wet well or basinVentilation A or NNV


Wet well or basinVentilation A or NNV


Grade

3 ft(0.9 m)





3-ft (0.9-m) envelopearound opening



1999 Edition

Figure A-2-2(d) Abovegrade equipment housing or vault physically separated from wet well or basin; illustration of Table 2-2, rows 18and 30.

Figure A-2-2(e) Belowgrade or partially belowgrade equipment hous-ing or vault physically separated from wet well or basin; illustration of Table 2-2, rows 5, 12, 17, 31, and 36.

Abovegradepump station or vault

Ventilation NR

Grade

Physicallyseparated


Dry well or vaultVentilation C

Dry well or vaultVentilation D

Dry well or vaultVentilation C

Dry well or vaultVentilation D

Grade

Grade




APPENDIX A 820–45

1999 Edition

Figure A-2-2(f) Abovegrade equipment housing or vault not physical-ly separated from wet well or basin; illustration of Table 2-2, row 19.

Figure A-2-2(g) Odor-control system location physically separated from wet well; illustration of Table 2-2, row 20.


Ventilation A

5-ft (1.5-m) radius from vent (Div. 2) 3-ft (0.9-m) radius

from vent (Div. 1)


3-ft (0.9-m)envelopearoundopening


Ventilation B

Grade


3-ft (0.9-m) radius around equipment (Div. 2)

3-ft (0.9-m) radius around equipment (Div. 2)


3-ft (0.9-m) radius from vent



See Note

Note:

Location of envelope if gas source is Class I, Div. 1

Location of envelope if gas source is Class I, Div. 2

Outdoor locationVentilation CVentilation D

GradeGradeGrade



1999 Edition

A-3-1 Additional information on sources of hazards ignition,sources of, and mitigation measures associated with liquidstream treatment processes is contained in Appendix D.

A-3-2 See Figure A-3-2, which provides an example for Table 3-2.

A-4-1 Additional information on sources of hazards, sourcesof ignition, and mitigation measures associated with solidstreatment processes is contained in Appendix D.

A-4-2 See Figures A-4-2(a) through (g), which provide exam-ples for Table 4-2(a).

Figure A-3-2 Primary sedimentation tank; illustration of Table 3-2, row 6.

Figure A-4-2(a) Anaerobic digester with fixed or floating cover above grade not enclosed in a building; illustration of Table 4-2(a), rows 15a and 15b.

Figure A-4-2(b) Anaerobic digester control building containing sludge gas piping and with ventilation A; illustration ofTable 4-2(a), row 16a.

Minimumoperatingwaterlevel

Grade

1.5 ft (0.5 m)

10 ft (3.1 m)


Sludgegaspiping

Cover

Gas dome at highest elevation

Tank interior

5 ft(1.5 m)

5 ft(1.5 m)

10 ft(3.1 m)

15 ft(4.6 m)

Grade


5 ft(1.5 m)

5 ft(1.5 m)

Control building

Grade

Anaerobic digester

Sludgegaspiping

5 ft(1.5 m)

5 ft(1.5 m)5-ft (1.5-m) envelope

from door (Div. 1)

Gas dome at highest elevaiton

5-ft (1.5-m) envelope (Div. 2)

5 ft(1.5 m)

5 ft(1.5 m)

5 ft(1.5 m)

5 ft(1.5 m)

5 ft(1.5 m)

5 ft(1.5 m)

10-ft (3.1-m)radius (Div. 2)


10 ft(3.1 m)

15 ft(4.6 m)


APPENDIX A 820–47

1999 Edition

Figure A-4-2(c) Anaerobic digester control building containing sludge gas piping and with ventilation C; illustration ofTable 4-2(a), row 16c.

Figure A-4-2(d) Anaerobic digester control building containing sludge gas–processing equipment physicallyseparated and with ventilation B for the processing room and ventilation C for the control building; illustration ofTable 4-2(a), rows 16c and 17b.

Supplyfan

Inside entire building

Exhaustfan

Control building

Grade

Anaerobic digester

Sludge gas piping

Physically separated

5 ft(1.5 m)

5 ft(1.5 m)

5 ft(1.5 m)

5 ft(1.5 m)

Gas domeat highestelevation

10 ft(3.1 m)

15 ft(4.6 m)


Anaerobicdigestercontrolbuilding

Ventilation C

Digester gas-

processingroom

Ventilation B

Grade

Anaerobic digester

Physicallyseparated Sludge

gaspiping

5 ft(1.5 m)

5 ft(1.5 m)

5 ft(1.5 m)

5 ft(1.5 m)

5 ft(1.5 m)

10 ft(3.1 m)

Supplyfan

Supplyfan

Exhaustfan

Gas-processingequipment


Supply fanfrom outsideof classifiedarea

Gas domeat highestelevation

10 ft(3.1 m)

15 ft(4.6 m)



1999 Edition

Figure A-4-2(e) Anaerobic digester control building containing sludge gas–processing equipment not physicallyseparated and with ventilation A; illustration of Table 4-2(a), row 16.

Figure A-4-2(f) Underground tunnel containing natural gas or sludge gas piping with ventilation D; illustration of Table 4-2(a), rows 20aand 20b.

Figure A-4-2(g) Underground tunnel containing natural gas or sludge gas piping with ventilation C; illustration of Table 4-2(a), rows 20cand 20d.

Sludge gas-processingequipment

Control building Anaerobic digester

Sludgegaspiping

5 ft(1.5 m)

5 ft(1.5 m)

10 ft(3.1 m)

15 ft(4.6 m)

5 ft(1.5 m)

5 ft(1.5 m)

5 ft(1.5 m)

5 ft(1.5 m)

5 ft(1.5 m)

5 ft(1.5 m)

Grade

5-ft (1.5-m)envelope (Div. 2)

5-ft (1.5-m) envelope from door (Div. 1)

Gas dome at highestelevation



Exhaustfan


Digester gaspiping

Natural gaspiping

Grade

Valve

Drain

10-ft (3.1-m) radius (Div. 1)



Digester gaspiping

Natural gaspiping

Grade

Valve

Drain




APPENDIX A 820–49

1999 Edition

A-5-1 Additional information is contained in Appendix D.

A-5-4.1 For further information, see NFPA 328, RecommendedPractice for the Control of Flammable and Combustible Liquids andGases in Manholes, Sewers, and Similar Underground Structures.

A-5-4.2 Other types of detectors, such as heat and smokedetectors, have standards recommending spacing usuallybased on a certain area per detector. There are no known rec-ognized standards or guidelines for the locating or spacing ofcombustible gas detectors.

Whether natural or mechanical, air movement is a veryimportant consideration in installing combustible gas detec-tors. This aspect should be carefully investigated, includingthe effect of doors, windows, vents, and other openings. Itcould be necessary to conduct a ventilation study that couldinvolve a nontoxic smoke movement analysis.

Dispersion characteristics can also affect detector place-ment. Vapors and gases will disperse inversely proportional totheir specific density in a quiescent environment. Vapors andgases with densities less than that of air will diffuse quickly atfirst until the vapor or gas becomes diluted. Heavier-than-airvapors and gases will tend to settle at a low area and not diffuseinto the atmosphere unless dispersed by ventilation or temper-ature currents. Vapors with densities close to that of air willexhibit little mixing effect and will be transported largely byair currents.

There are various types of sensing devices. It is importantto select the proper sensing device for each application andfor the environment in which it will be placed. Most organicand inorganic compounds can be safely monitored with a cat-alytic combustion–type sensor. However, organic and metallicsolvents containing lead, silicones, plasticizers, or halogenscan poison the catalytic element.

A-5-5.3 In all cases, standard “Danger” signs identifying thepurpose of the lights and audible alarms and warning againstentry when there is an alarm condition should be posted asnear as practical to the warning devices.

A-6-3.1 See Appendix C of this document and NFPA 328, Rec-ommended Practice for the Control of Flammable and Combustible Liq-uids and Gases in Manholes, Sewers, and Similar UndergroundStructures.

A-6-3.3.3.3 Plastic or fiberglass-reinforced plastic products areoften used as materials of construction in unit processes such as

rotating biological contactors (RBC), bio-towers, trickling filters,inclined plate (tube) settlers, ventilation ducts, and other equip-ment that might be subject to corrosion. Under normal operat-ing conditions, these plastic or fiberglass-reinforced plasticmaterials might be submerged. However, during maintenanceor repair they can become exposed. During maintenance andrepair operation, extreme care should be taken with open flamesuch as cutting torches, as these exposed plastic or fiberglass-reinforced plastic materials might present a considerable fuelload if ignited.

A-7-3.3 Ventilation rates and procedures established by thisstandard might not be sufficient to protect personnel fromexposure to toxic gases that might be present in enclosedspaces.

A-8-2.1 Proper preventive maintenance of operating and fireprotection equipment, as well as operator training, are impor-tant aspects of a viable fire prevention program.

A-8-3 A fire risk evaluation of the plant should result in recom-mendations to integrate the fire prevention and fire protec-tion required in this document into the plant specificconsiderations regarding design, layout, and anticipated oper-ating requirements. The evaluation should result in a list ofrecommended fire prevention features to be provided basedon acceptable means for the separation or control of commonand special hazards, the control or elimination of ignitionsources, and the suppression of fires.

This evaluation should focus on materials of constructionin ventilation systems and in processes that normally operatein a wet condition — for example, plastic media trickling fil-ters, bio-towers, and rotating biological contactors. These sys-tems and process units can represent a considerable fuel loadif ignition occurs during operation. Maintenance, fire spread,and smoke production should be considered in the selectionof materials.

Consideration should also be given to locating processareas — for example, screen room, areas containing gas man-agement equipment, and so forth — that represent a signifi-cant explosion hazard remote from other process areas toreduce the risk of consequent damage should an explosionoccur.

A-8-4(7) For an example of a fire report, see Figure A-8-4(7).


1999 Edition

Figure A-8-4(7) Sample fire report.

Fire Report

Name of company

Date of fire Time of fire Operating facility

Under construction?

Plant or location where fire occurred

Description of facility, fire area, or equipment (include nameplate rating) involved:

Cause of fire, such as probable ignition source, initial contributing fuel, equipment failure causing ignition, etc.

Description of fire and events and conditions preceding, during, and after the fire

Types and approximate quantities of portable extinguishing equipment used

Fire extinguished with portable equipment only? Public fire department called?

Employee fire brigade at the location? Qualified for incipient fires?

Qualified for interior structural fires?

Fixed fire-extinguishing equipment installed?

Type of fixed extinguishing system

Automatic operation Manually actuated Both

Specific types of detection devices

Did fixed extinguishing system control fire? Extinguish fire? Control and extinguish fire?

Did detection devices and extinguishing system function properly?

If not, why not?

Estimated direct damage due to fire $ , or between $ and $

Estimated additional (consequential) loss $ Nature of additional loss

Estimated time to complete repairs/replacement of damaged equipment/structure

Number of persons injured Number of fatalities

What corrective or preventive suggestions would you offer to other utilities with similar equipment, structures,

or extinguishing systems?

Submitted by Title

APPENDIX B 820–51

1999 Edition

A-8-6.2 Once a detection system is installed, a preventivemaintenance program is essential. A detection system is onlyas good as the care and maintenance it receives, which is espe-cially true in harsh environments. When installing instru-ments, ease of calibration and maintenance should beconsidered. Periodic calibration, checks, and adjustments arenecessary for detection to remain accurate. If instruments areinaccessible, it is more likely that maintenance procedures willnot be followed. Detectors should be located to prevent expo-sure to physical damage from normal activities in the area.

Consideration should be given to the scope and limitationsof the listing for combustible gas detectors. For example, theHazardous Location Equipment Directory by Underwriters Labora-tories Inc. offers guidance in maintaining and using combus-tible gas detectors. The following is extracted from thedirectory’s product category guide for listed gas detectors(JTPX).

Gas or vapor detectors should be calibrated andinspected by the operator in compliance with the man-ufacturer’s instructions, as performance of the instru-ments will depend on proper maintenance. Theinstruments should be calibrated with known gas– orvapor–air mixtures at intervals and particularly afterreplaceable sensors incorporated in the detecting unitare replaced. Certain gases or vapors can adverselyaffect (poison) the sensors and limit the use of theinstruments. Sampling atmospheres containing gases orvapors for which they have not been previously cali-brated should, therefore, be avoided.

A-8-7 Impairments to fire protection systems should be asshort in duration as practicable. If the impairment is planned,all necessary parts and manpower should be assembled priorto removing the protection system from service. When animpairment is not planned, the repair work should be expe-dited until repairs are completed.

A-8-9 The size of the plant and its staff, the complexity of fire-fighting problems, and the availability of a public fire depart-ment should determine the requirements for a fire brigade.The organization of a fire brigade is encouraged for wastewa-ter treatment facilities located in remote areas.

If a fire brigade is provided, its organization and trainingshould be identified in written procedures. The recommenda-tions of NFPA 600, Standard on Industrial Fire Brigades, andOSHA, 29 CFR 1910.156, should be consulted for additionalinformation.

The following items discuss special fire-fighting conditionsunique to wastewater facilities. This information might be use-ful in fire brigade training and fire preplanning.

(a) Cable tray fires should be handled like any fire involv-ing energized electrical equipment. It might not be practicalor desirable to de-energize the cables involved in the fire.Water is the most effective extinguishing agent for cable insu-lation fires, but it should be applied with an electrically safenozzle. Some cable insulations [for example, polyvinyl chlo-ride (PVC), neoprene, or Hypalon™] can produce dense

smoke in a very short time. In addition, PVC liberates hydro-gen chloride (HCl) gas. Self-contained breathing apparatusshould be used by personnel attempting to extinguish cabletray fires.

(b) Some sludge-drying and -composting processes (espe-cially solvent extraction drying, sludge-drying kilns, and in-vesselcomposting systems) might produce a product that might be sub-ject to spontaneous combustion. Generally, water will be the mosteffective fire-fighting agent in these areas. However, fires might bedeep-seated in stockpiled products, which might have to be dis-persed with front-end loaders or similar equipment to fully extin-guish smoldering and burning material.

(c) Some chlorinated hydrocarbon products commonlyused as foam suppressants or flocculation agents in wastewatertreatment might cause spontaneous combustion when in con-tact with powdered disinfectants. These chemicals should bestored separately and care should be exercised in their use.

(d) Plastic or fiberglass-reinforced plastic materials used inprocess units or ventilation systems might represent a consid-erable fuel load if ignited during operation or maintenanceand might necessitate special response techniques.

A-8-9.1 NFPA 600, Standard on Industrial Fire Brigades, andOSHA, 29 CFR 1910.156, should be consulted.

A-8-10 Federal regulations (40 CFR 761.30) specify that thelocal fire department should be notified of the location of allPCB-filled transformers and other electrical equipment.

Appendix B Wastewater Treatment Processes

This appendix is not a part of the requirements of this NFPA doc-ument but is included for informational purposes only.

B-1 General.

B-1.1 Wastewater. Wastewater is principally the spent watersupply of the community. It is used to flush and transporthuman wastes and the liquid wastes of commerce, industry,and institutions. Groundwater, surface water, and storm watermight also be present. The primary purposes of wastewatertreatment are to protect the health and well-being of the com-munity and the quality of the receiving waterway. The extentor completeness of wastewater treatment to accomplish thesepurposes is governed by legislation and regulations and willvary from jurisdiction to jurisdiction.

B-1.2 Elements of Wastewater Treatment. The principal ele-ments of wastewater treatment are as follows:

(1) Preliminary treatment(2) Primary treatment(3) Secondary treatment(4) Tertiary treatment(5) Disinfection(6) Sludge treatment

A typical schematic flow and process diagram for a wastewa-ter treatment plant is shown in Figure B-1.2.


1999 Edition

Figure B-1.2 Typical schematic flow and process diagram of a wastewater treatment plant.

B-2 Preliminary Treatment. Preliminary treatment is theconditioning of wastewater as it enters the wastewater treat-ment plant. Preliminary treatment removes materials thatmight be harmful to or might adversely affect the operation ofthe treatment plant. Such material might include lumber,cardboard, rags, stones, sand, plastic, grease, and scum. Themethods and equipment used to remove these materialsinclude bar racks, bar screens, and gravity or aerated gritchambers.

B-3 Primary Treatment. Primary treatment is first-stage sedi-mentation, in which settleable, suspended, and floating mate-rial is removed from the wastewater following preliminarytreatment. Well-operated primary treatment facilities canremove as much as 60 percent of the influent suspended solidsand 30 percent of the influent biochemical oxygen demand.However, primary treatment does not remove colloidal or dis-solved solids.

B-4 Secondary Treatment. Secondary treatment is intendedto reduce the concentrations of the remaining suspended sol-ids and the dissolved and colloidal organic matter in the waste-water. Such material is not removed to any significant degreein primary treatment. A wastewater treatment plant having

secondary treatment following primary treatment commonlycan achieve removal of a total of 90 percent of the influent sus-pended solids and biochemical oxygen demand of the rawwastewater. Secondary treatment processes can be either bio-logical or physical chemical.

B-4.1 Biological Treatment. Most municipal secondary treat-ment processes are biological. These processes can be classi-fied as fixed film or suspended growth. In each process, amixed population of microorganisms is established in thepresence of oxygen. These microorganisms metabolize thedissolved organic matter in the wastewater and form a biolog-ical mass. The effluent from fixed film or suspended growthprocesses contains suspensions of biological solids. These sol-ids are removed from the treated wastewater in a secondarysedimentation tank.

B-4.2 Physical-Chemical Treatment. Physical-chemical treat-ment includes one or more physical-chemical unit processesto treat primary effluent. Such processes might include chem-ical coagulation, precipitation, and filtration to remove sus-pended matter and activated carbon adsorption to removesoluble organics.

Rawwastewater

Wetwell

Pumps

Screening Gritremoval

Pre-aerationtank

Primary treatmentDisposal

Scumskimmings

Chemicalfeed & control

facilities

Secondary treatment

Tricklingfilters

Primarysludge

Returnsludge

Wastesludge

Optionalequalization

Aerationtank

Secondarysettling

tank

Wastesludge

Nitrification/denitrification

Primarysettling

tank

Carbonregeneration

Carbonadsorption

Tertiarysettling

tank

Effluentfilters

Backwash

Chlorinecontact

tank

Effluentaerators

Finaleffluent

To influent

Backwashwaste

Holdingtank

Aerobic oranaerobicdigestion

Sludgethickening

SludgedewateringUltimate disposal

Solids treatment

Incinerator

Ashdisposal

Tertiary treatment

APPENDIX C 820–53

1999 Edition

B-5 Tertiary Treatment. Tertiary treatment is used as neces-sary to reduce the concentration of inorganic and organicconstituents below the concentrations achievable through sec-ondary treatment. Tertiary treatment also includes theremoval of nitrogen and phosphorus by additional processunit operations. Tertiary treatment processes can be physical,chemical, biological, or a combination.

B-6 Disinfection. Disinfection is necessary to destroy patho-genic bacteria, viruses, and amoebic cysts commonly found inwastewater. Disinfection processes can be chemical, such asozonation or chlorination, or physical, such as ultraviolet irra-diation. Chemical disinfection using chlorine and, infre-quently, ozone are the most widely used means of wastewaterdisinfection.

B-7 Sludge Treatment.

B-7.1 Sludge Stabilization. Sludge is the settled solids accu-mulated and subsequently separated from the liquid duringvarious wastewater treatment processes. Sludge handling anddisposal is the most difficult, important, and costly part of thewastewater treatment process. Sludge treatment typically con-sists of stabilization followed by dewatering prior to disposal.Sludge can be stabilized under either anaerobic or aerobicconditions. Anaerobic sludge digestion takes place in theabsence of free oxygen. The solid end product of anaerobicdigestion is relatively nonputrescible and inoffensive. The off-gas produced in anaerobic sludge digestion contains about 65percent methane and can be collected and burned as a fuel.

B-7.2 Sludge Dewatering. Both anaerobic and aerobic diges-tion result in a reduction in the total volume and weight of theexcess organic matter. It is often desirable, before final dis-posal, to further reduce the volume and weight of sludge andto change it from a liquid that is more than 95 percent waterto a semisolid form. Dewatering can be accomplished by usingdrying beds, vacuum filters, centrifuges, filter presses, ormechanical gravity units. The dewatering operation often isenhanced by chemically conditioning the sludge before dewa-tering. The conditioning can include a thickening step thatcan be gravity or air flotation. Thermal conditioning can alsobe used to prepare sludge for dewatering.

B-7.3 Sludge Cake Disposal. After sludge has been dewa-tered, it is identified as sludge cake. This material is disposedof by several different methods. It can be incinerated toreduce the volume to ash — approximately 10 percent of theoriginal cake. The heat of this combustion can be utilized toproduce steam for process and building heat. The cake can becomposted to produce a soil conditioner. Cake can be spreaddirectly on land for agricultural use or it can be landfilled as awaste material.

Appendix C Selection of CollectionSystem Materials


C-1 General. Wastewater collection systems might or mightnot be vulnerable to the introduction of flammable liquidsinto the wastewater. These liquids, if lighter than water, willfloat and collect on the surface. The presence of these materi-als can present a threat to the integrity of the collection systemshould ignition occur.

C-2 Materials of Construction.

C-2.1 Some materials commonly used in sewer constructionare vulnerable to attack from environmental conditions com-monly found in collection systems but might provide resistanceto damage from fire. Other materials might be vulnerable tostructural damage from fire but provide protection againstlong-term structural failure from corrosion.

C-2.2 For additional information on corrosion control, seeNational Association of Corrosion Engineers RecommendedPractices RP01 series and the appropriate Water EnvironmentFederation publications.

C-3 Materials Risk Assessment.

C-3.1 The materials risk assessment should include an evalua-tion of all factors that could potentially affect the safety andlong-term functioning of the collection system. Factors to beconsidered should include both of the following:

(a) The potential that flammable liquids can enter the sys-tem from identifiable sources. As an example, a system servinga combined system or a system serving commercial and indus-trial dischargers might be more vulnerable to exposure tofloating flammable materials than separate systems servingresidential communities.

(b) The potential for the development of conditions thatmight promote attack to materials vulnerable to corrosiveagents. Experience with existing conditions within the com-munity and with existing systems with similar characteristicsshould be taken into full account.

C-3.2 The materials risk assessment should consider the long-term threat that flammable, corrosive, and explosive agentspresent to the community and to the system’s ability to servethe community before a final selection is made. It is recom-mended that the materials risk assessment be presented tolocal authorities for review and comment before the finalselection of materials of construction is completed.

C-4 Examples.

C-4.1 Storm sewers serving locations such as residential areasand areas where significant quantities of flammable or com-bustible materials are not expected to enter the sewer system,sewers, and appurtenant structures could be constructed ofany appropriate material.

C-4.2 Storm sewers serving locations such as commercial andindustrial areas or areas where there is a possibility that signif-icant quantities of flammable or combustible materials couldenter the sewer system through illicit discharges, curb inlets,leaking underground storage tanks, or broken pipes, sewers,and associated structures might be exposed to considerablerisk of fire. Materials meeting the definitions of noncombusti-ble, limited-combustible, or low flame spread might be appro-priate.

C-4.3 Where conditions or applications warrant selection ofother materials for storm sewer piping and appurtenant struc-tures, consideration to flame spread, smoke generation, andthe impact that fire or explosion will have on the structuralintegrity and operability of the sewer system and the economicand environmental consequences of having the sewer systemout of service should be included in the materials risk assess-ment.

C-4.4 Separate sanitary sewers serving locations such as resi-dential areas and areas where significant quantities of flamma-


1999 Edition

ble or combustible materials are not expected to enter thesewer system, sewers, and appurtenant structures can be con-structed of any appropriate material.

C-4.5 Separate sanitary sewers serving locations such as com-mercial and industrial areas or areas where there is some pos-sibility that significant quantities of flammable or combustiblematerials could enter the sewer system from illicit discharges,leaking underground storage tanks, or broken pipes, sewers,and appurtenant structures might be exposed to some risk offire. Materials meeting the definitions of noncombustible, lim-ited-combustible, or low flame spread might be appropriate.

C-4.6 Where applications warrant selection of other materialsfor separate sanitary sewer piping and appurtenant structures,consideration to flame spread, smoke generation, and theimpact that a fire or explosion will have on the structuralintegrity and operability of the sewer system and the economicand environmental consequences of having the sewer systemout of service should be included in the materials risk assess-ment.

C-4.7 Where combined sewers are designed to collect bothwastewater and storm water, or where there is a possibility thatsignificant quantities of flammable or combustible materialscould enter the sewer system by means of curb inlets, illicit dis-charges, leaking underground storage tanks, or broken pipes,all sewers and other appurtenant structures can be exposed toconsiderable risk of fire. Materials meeting the definitions ofnoncombustible, limited-combustible, or low flame spreadmight be appropriate.

C-4.8 Where conditions or applications warrant selection ofother materials for combined sewer piping and appurtenantstructures, consideration to flame spread, smoke generation,and the impact that a fire or explosion will have on the struc-tural integrity and operability of the sewer system and the eco-nomic and environmental consequences of having the sewersystem out of service should be included in the materials riskassessment.

Appendix D Chemical and Fuel Fire/ExplosionHazards


D-1 General Information.

D-1.1 This appendix provides guidelines for protectionagainst fire and explosion in the chemical- and fuel-handlingand storage facilities. This appendix does not include gas uti-lization equipment, vehicle maintenance areas, or laborato-ries. Table D-1.1 summarizes the various hazards associatedwith chemical- and fuel-handling and storage facilities.

D-1.2 This appendix also contains additional information onspecific areas or unit operations associated with the storageand handling of chemicals and fuels commonly used inmunicipal wastewater treatment plants.

D-2 Sources of Hazards. See Table D-2.

D-2.1 Fuel Gases. Fuel gases include natural gas, manufac-tured gas, sewer gas, liquefied petroleum gas–air mixtures, liq-uefied petroleum gas in the vapor phase, mixtures of thesegases, and floating flammable liquids. Some of these gaseshave specific gravities lower than that of air so that, when

released, they will rapidly rise and diffuse above the point ofleakage. Flammable mixtures are produced when these gasesare mixed with air within certain limits. These mixtures can beconsidered suffocating gases.

D-2.2 Sludge Gases. These flammable gases result from thefermentation or anaerobic decomposition of organic matter.Explosive conditions, especially concerning compression andstorage, can result when these gases are mixed with air.

D-2.3 Sewer Gases. These flammable gases result from thefermentation or decomposition of organic matter. Explosiveconditions, especially concerning the screening, degritting,and primary clarification processes, might result when thesegases are mixed with air.

D-2.4 Unit Processes. Special consideration should be givento the following unit processes associated with solids treatment.

(a) Scum pits collect scum, grease, and other floatingflammable liquids from the surface of sedimentation tanks.Special consideration should be given to equipment located inthese areas because of potential explosion and fire hazards.

(b) Sumps and tanks that collect drainage from anaerobicsludge treatment processes or that store, mix, and blendsludge might also collect significant volumes of sludge gas.Special consideration should be given to equipment located inthese areas because of the potential for explosion.

(c) Anaerobic digesters are unit processes specificallydesigned to produce sludge gas from the fermentation oranaerobic decomposition of organic matter. The sludge gasnormally contains significant volumes of methane as a by-product of the anaerobic digestion process. Special consider-ation should be given to equipment located in and aroundanaerobic digesters because of the potential for explosion.

(d) Solvent extraction and dehydration processes can pro-duce a very dry organic dust as a by-product. Special consider-ation should be given to equipment located in dust-handlingareas because of the potential for explosion.

(e) Incinerators used to burn scum or sludge cake are igni-tion sources when in operation. Special consideration shouldbe given in construction of incineration buildings and in stor-age of combustible materials in incineration areas.

(f) Sludge-dewatering and sludge-cake conveyance equip-ment generate sludge cake and convey it to its final destina-tion (e.g., incineration, landfill, etc.). Dried cake can be acombustible material. Special consideration should be givenin construction, operation, maintenance, and housekeepingof the equipment and surrounding areas.

(g) Pumping stations that handle raw wastewater shouldbe classified in the same manner as wastewater pumping sta-tions (see Chapter 2). In-plant pumping stations should be clas-sified depending on their location in the process train and thetype of material handled. Restrictive classifications are gener-ally not necessary for pumping stations that handle fullytreated wastewater.

(h) Grit chambers or screening equipment that is housedin a building or in belowgrade pits might be subject to thesame fire and explosion hazards as pumping station wet wells.

(i) Imhoff tanks and other similar processes can combinethe wastewater liquids and solids treatment streams in a singlevessel. Special consideration should be given to equipmentlocated in or around Imhoff tanks or similar processes becauseof the generation of methane gas from anaerobic solids diges-tion processes within the vessel and the possibility of volatilesubstances being released from the wastewater.

APPENDIX D 820–55

1999 Edition

Table D-1.1 Chemical and Fuel Fire/Explosion Hazards

A B C D E F G

Materials and Function

Fire and Explosion Hazard Ventilation

Extent of Classified Area





1ALCOHOLUsed in some ter-tiary treatment

Flammable vapors See NFPA 30

2

CHLORINE (Gas)Chlorination of water

Aids combustion; oxidizer, toxic

NR NR Refer to Chlorine Institute

NR (This equip-ment handles a corrosive chemical that necessitates the use of specific materials of con-struction. Special consideration should be given to these materials of construction.)

NR

3

OXYGENUsed in aeration basins (See Chapter 3.)

Aids combustion; oxidizer

See NFPA 50 and NFPA 53 NR NR

4

DIESEL FUEL, GASOLINE, AND MOTOR OILSFuels for equip-ment.

Various See NFPA 30 and NFPA 513 NR Indoors; FSS and FE; out-doors, FE

5LIQUEFIED PETROLEUM GAS

Flammable gas NR (stored outdoors)

See NFPA 58 NR FE

6OXYGEN GENER-ATION AND STORAGE

Aids combustion; oxidizer, oxygen-enriched areas

See NFPA 50 and NFPA 53 NR FSS (if indoors), H, and FE

7OZONE GENERA-TION

Aids combustion; oxidizer, toxic

See NFPA 50 and NFPA 53 NR FSS (if indoors), H, and FE

8

ACTIVATEDCARBON(powdered orpulverized)

Combustible NR NR NR NR NR

FE — Portable fire extinguisherFSS — Fire suppression system (e.g., automatic sprinkler, water spray, foam, gaseous, or dry chemical)H — Hydrant protection (see 5-2.4)NEC — See NFPA 70, National Electrical CodeNR — No requirement


1999 Edition

Table D-2 Gases Commonly Found in Wastewater Treatment

Explosive Limits (% vol)

Name(Chemical Formula) LEL UEL

Density1 Heavier/Lighterthan Air Sources

Ammonia2 (NH3) 16 25 L Storage tank leaks

Chlorine3 (Cl2) Nonflammable H Disinfectionprocesses

Storage tanks

Gasoline2 (C3H12 – C9H20)

1.3 7.1 H Storage tanks

Tank truck spills

Hydrogen chlo-ride (HCl)

Nonflammable H Storage tank leaks

Ceramic diffuser cleaning

Hydrogen sulfide2,4 (H2S)

4.0 44 H Sewer gas

Sludge gas

Natural gas2 3.8−6.5 13−17 L Gas-piping leaks

Nitrogen (N2) Nonflammable L Storage tanks

Oxygen genera-tion processes

Denitrification processes

Oxygen3 (O2) Nonflammable H Generation of oxygen on site

Activated sludge processes

Storage tanks

Sludge processes

Ozone3 (O3) Nonflammable H Disinfectionprocesses

On-site genera-tion processes

Sewer gas5 5.3 19.3 H Sewer systems

Sludge gas6 5 15 L Sludge digestion processes

Sulfur dioxide (SO2)

Nonflammable H Dechlorination processes

Storage tanks

1The table lists the physical properties at standard temperature and pressure. Due to actual field con-ditions, these gases might disperse and might be present throughout the structure.2Source: NFPA 325, Guide to Fire Hazard Properties of Flammable Liquids, Gases, and Volatile Solids.3These gases accelerate combustion.4Rarely reaches explosive concentration in wastewater treatment plants.5Contains approximately 70 percent carbon dioxide, 5 percent methane, and 25 percent other gases. (Source: US EPA)6Contains approximately 65 percent methane, 30 percent carbon dioxide, and 5 percent other gases. (Source: US EPA)

APPENDIX D 820–57

1999 Edition

(j) The primary sedimentation tank might collect andconcentrate floating flammable liquids.

(k) Secondary and tertiary sedimentation tanks and aera-tion tanks not preceded by primary sedimentation can be sub-ject to the same fire and explosion hazards as primarysedimentation tanks because of the potential of floating flam-mable liquids collecting on the surface. Where bypassing ofprimary sedimentation is possible, although not normally uti-lized, secondary and tertiary sedimentation tanks and aerationtanks might not be subject to the same fire and explosionpotential as primary sedimentation.

(l) Unit processes employing oxygen-enriched atmo-spheres necessitate special consideration. Covered facilitiesmight be unclassified above the covering deck. However, anyequipment or instrumentation housed under the cover withinthe reactor space should be suitable for exposure to volatilehydrocarbons in an oxygen-enriched atmosphere. Oxygenitself is not flammable. However, increased concentrations ofoxygen greatly increase the fire hazard. Oxygen aeration tanksand other similar processes should be equipped with continu-ously operating hydrocarbon LEL monitoring devices that willautomatically cut off the oxygen supply and purge reactorgases with atmospheric air when 25 percent LEL conditionsare registered. With the exception of purging equipment, allassociated aeration equipment should automatically shut offwhen 50 percent LEL conditions are registered to remove allpossible sources of ignition.

(m) Galleries and other connecting structures that containpipes transporting flammable gases or liquids necessitate spe-cial consideration in design and fire protection.

(n) Plastic media or wood for trickling filters, rotating bio-logical contactors, bio-towers, and other fixed-film systems arenot a significant hazard in normal operations. However, thesematerials are normally classified as combustible and can con-tribute a considerable fuel load if ignited under certain condi-tions, such as during maintenance and construction. Somefixed-film treatment systems are anaerobic and produce acombustible gas by-product, which aggravates the hazard forsuch enclosures containing these materials.

D-2.5 Chemicals. Wastewater treatment plants use a variety ofgaseous, solid, and liquid chemicals that by themselves orwhen mixed with oxygen or other chemicals can be a potentialsource of fire, explosion, or both. Additional information canbe found in NFPA 45, Standard on Fire Protection for LaboratoriesUsing Chemicals; NFPA 49, Hazardous Chemicals Data; NFPA 497,Recommended Practice for the Classification of Flammable Liquids,Gases, or Vapors and of Hazardous (Classified) Locations for Electri-cal Installations in Chemical Process Areas; and NFPA 499, Recom-mended Practice for the Classification of Combustible Dusts and ofHazardous (Classified) Locations for Electrical Installations in Chem-ical Process Areas. Chemicals should be handled, processed, andstored in a manner that eliminates or significantly reduces thehazard to the wastewater treatment facility and personnel andis acceptable to the authority having jurisdiction. Chemicalsshould be properly labeled to identify the materials and haz-ards, and materials safety data sheets should be made availableto all personnel.

D-2.6 Hazardous Gases. Sewer and sludge gases are flamma-ble gases generated by the fermentation or decomposition oforganic matter. Explosive conditions, especially concerningscreening, degritting, primary clarification, and the anaerobicdigestion process, can result when these gases are mixed with air.Specialty gases utilized for the following can form flammable/

explosive conditions when either acting alone or mixed withother gaseous organic substances:

(1) Laboratory analysis and instrumentation calibration(hydrogen, methane, etc.)

(2) Wastewater treatment plant unit processes (chlorine,ozone, etc.)

(3) Welding operations (acetylene, oxygen, etc.)

Fuel gases, including natural gas, manufactured gas, andliquefied petroleum gas, used as fuels for wastewater treat-ment plant equipment can cause flammable/explosive condi-tions when improperly used, handled, or stored. Appropriatemeasures should be taken to prevent the accumulation of haz-ardous gases, including ventilation, proper storage, and safehandling/distribution systems. For additional guidance, seeNFPA 55, Standard for the Storage, Use, and Handling of Com-pressed and Liquefied Gases in Portable Cylinders, and NFPA 59A,Standard for the Production, Storage, and Handling of Liquefied Nat-ural Gas (LNG). In processes where explosive mixtures cannotbe prevented, explosion venting or protection systems shouldbe provided. See NFPA 68, Guide for Venting of Deflagrations,and NFPA 69, Standard on Explosion Prevention Systems, for addi-tional guidance.

D-2.7 Liquids. The disposal of waste chemical products throughsewers and into wastewater treatment plants, and the disposal ofwaste chemical products and scum skimmed from sedimentationtanks, can be potential sources or contributing causes of fire andexplosive conditions. Hydrocarbon liquids such as gasoline, kero-sene, oils, and various chemicals either sent to sewers and drainsor used for various applications at wastewater treatment plants canalso provide flammable vapor concentrations at certain locations.For additional information, see NFPA 30, Flammable and Combusti-ble Liquids Code, and NFPA 329, Recommended Practice for HandlingReleases of Flammable and Combustible Liquids and Gases. Areas ofwastewater treatment plants as identified and classified in Tables2-2, 3-2, 4-2(a), and 4-2(b), especially areas of primary treatment,should be protected as flammable liquid hazards.

D-2.8 Finely Divided Solids and Dusts. Finely divided solidsused in various wastewater treatment processes, especiallysludge dehydration processing, or dust by-products producedby such processes can be combustible or cause potential flam-mable and explosive conditions. Process areas should becleaned on a regular schedule to prevent the accumulation ofhazardous concentrations of dust. Equipment handling finelydivided solids should be designed and installed in a mannerthat protects against the hazards of fire and explosion. Addi-tional information can be found in NFPA 61, Standard for thePrevention of Fires and Dust Explosions in Agricultural and FoodProducts Facilities; NFPA 91, Standard for Exhaust Systems for AirConveying of Vapors, Gases, Mists, and Noncombustible ParticulateSolids; and NFPA 8503, Standard for Pulverized Fuel Systems.

D-2.9 Materials. Certain materials are used in wastewatertreatment plants because of humid or corrosive atmospheres,including wood, plastic, fiberglass-reinforced plastics (FRPs),paints and coatings, insulating material, and furnishings, canbe combustible, limited-combustible, or low flame spreadunder certain conditions. Some of these materials can presenta considerable fuel load if ignited. Buildings and structuresshould be provided with fire protection in accordance withChapter 6. Areas where materials are stored should be pro-vided with appropriate fire protection approved by the author-ity having jurisdiction. For additional guidance, see NFPA 13,


1999 Edition

Standard for the Installation of Sprinkler Systems, and NFPA 230,Standard for the Fire Protection of Storage.

D-3 Conditions for and Sources of Ignition. The potential igni-tion of flammable gases, liquids, and solids, including dusts, thatcan be found at a wastewater treatment plant is limited by certainfundamental conditions. Gases and generated vapors need to bemixed with air or an oxidizer to form a flammable mixture thatneeds heat of sufficient intensity for ignition. The ignition tem-perature of a combustible solid is influenced by the rates of air-flow and heating as well as the geometry of the rates of airflowand heating and the geometry of the solid. Ignition can resultfrom one or more of the following causes:

(1) Open flames or hot surfaces(2) Electrical arc (3) Sparks(4) Chemical reaction

D-3.1 Open Flames and Hot Surfaces. Open flames and hotsurfaces might be encountered during normal operation,repair and maintenance operations, or with malfunctioningequipment and appliances within a wastewater treatmentplant. Sources of ignition might include welding tasks, boilers,incinerators, kerosene-type lanterns, internal combustionengines, and smoking by personnel. Equipment producingopen flames or hot surfaces capable of producing ignitionshould be properly installed, maintained, and isolated frompotential hazards. For additional guidance, see NFPA 31, Stan-dard for the Installation of Oil-Burning Equipment; NFPA 37, Stan-dard for the Installation and Use of Stationary Combustion Enginesand Gas Turbines; NFPA 82, Standard on Incinerators and Wasteand Linen Handling Systems and Equipment; NFPA 8501, Stan-dard for Single Burner Boiler Operation; and NFPA 8502, Standardfor the Prevention of Furnace Explosions/Implosions in MultipleBurner Boilers. Smoking should be prohibited in all hazardousareas.

D-3.2 Electrical Arc. Sustained arcing faults can cause exten-sive damage to electrical switchgear and motor control cen-ters. This arcing might provide sufficient heat to igniteflammable gases or vapors present or generated as a result ofthe arc (e.g., pyrolysis of insulating material). Electrical equip-ment should be properly maintained in good operating con-dition. Faulty equipment should be removed from service. SeeNFPA 70B, Recommended Practice for Electrical Equipment Mainte-nance, for additional guidance.

D-3.3 Sparks. Sparks generated by the following can be asource of ignition for gases of flammable vapors:

(1) Defective or worn electrical and mechanical equipment(2) Activities performed by personnel(3) Static electricity

Fire prevention practices to eliminate or control this haz-ard should include a preventative maintenance program, theuse of nonsparking tools, and the provision of bonding andgrounding conductors in hazardous areas. See NFPA 77, Rec-ommended Practice on Static Electricity, for additional guidance.

D-3.4 Chemical Reaction. Fire and explosion can be the resultof the chemical reaction of substances that are as follows:

(1) Introduced in the wastewater treatment plant influent(2) Used for laboratory analysis(3) Necessary to various unit processes(4) Produced as by-products

Potential chemical reactions can cause hazardous condi-tions that range in severity from the generation of flames (i.e.,

spontaneous combustion) to explosion. Chemicals should beidentified and stored in a proper manner. Noncompatiblechemical combinations should be identified and segregatedstorage should be provided. See NFPA 491, Guide to HazardousChemical Reactions, for additional information.

D-4 Mitigation Measures. Mitigation of either hazards orpotential ignition sources is achieved with a commonly pre-ferred method of copious flushing with air (i.e., ventilation).In the event that a foreign combustible material enters thesewer system, removal by vacuum or coverage with foam mightbecome necessary. Whenever possible, such entry is to beavoided by containment and adsorption. Appropriate use of acombustible gas detector is warranted as a minimal precautionpreceding personnel entry into a collection system. The pres-ence of toxic gases should be considered when entering anyconfined space.

D-5 Storage and Production Facilities. Special considerationshould be given to the following facilities associated with the stor-age and production of chemicals and fuels used in the treatmentof municipal wastewater.

D-5.1 Oxygen generation, storage, and handling facilitiesnecessitate special consideration. Although oxygen is not itselfflammable, it does support combustion, and increased con-centration of oxygen greatly increases the fire hazard. SeeNFPA 50, Standard for Bulk Oxygen Systems at Consumer Sites.

D-5.2 Ozone is generated by passing oxygen through an elec-tric field. As with oxygen-generating facilities, there is anincreased fire hazard. Ozonation facilities necessitate specialconsideration because of the extreme heat and electric fieldgenerated and the additional concern for the extreme corro-sivity and toxicity of ozone. See NFPA 50, Standard for Bulk Oxy-gen Systems at Consumer Sites.

D-5.3 Chlorine is a very reactive chemical and necessitatesspecial consideration in storing and handling. Chlorine incombination with other chemicals can produce sufficient heatto cause combustion of flammable materials. Chlorine andother reactive chemicals should always be stored separately.(See information from the Chlorine Institute.)

D-5.4 Activated carbon stored in bulk or in bags can providea source of combustible material that can add a considerablefuel load if ignited. Special consideration should be given toequipment located in activated carbon-handling areas or acti-vated carbon storage facilities because of the potential for fire.

Appendix E List of Associations and Abbreviations


E-1 Association Addresses. The associations and their addressesare listed as follows.

(1) ANSI. American National Standards Institute, Inc., 11West 42nd Street, 13th floor, New York, NY 10036.

(2) EPA. Environmental Protection Agency, Municipal Tech-nology Branch (4204), 401 M Street, SW, Washington,DC 20460.

(3) FMRC. Factory Mutual Research Corporation, 1151 Bos-ton-Providence Turnpike, Norwood, MA 02061-9102.

(4) NFPA. National Fire Protection Association, 1 Battery-march Park, P.O. Box 9101, Quincy, MA 02269-9101.

APPENDIX G 820–59

1999 Edition

(5) OSHA. Occupational Safety and Health Administration,U.S. Department of Labor, 200 Constitution Avenue, NW,Washington, DC 20001.

(6) UL. Underwriters Laboratories Inc., 333 Pfingsten Road,Northbrook, IL 60062.

(7) WEF. Water Environment Federation, 601 Wythe Street,Alexandria, VA 22314-1994 (formerly WPCF, Water Pollu-tion Control Federation).

Appendix F Referenced Publications

F-1 The following documents or portions thereof are refer-enced within this standard for informational purposes onlyand are thus not considered part of the requirements of thisstandard unless also listed in Chapter 9. The edition indicatedhere for each reference is the current edition as of the date ofthe NFPA issuance of this standard.

F-1.1 NFPA Publications. National Fire Protection Associa-tion, 1 Batterymarch Park, P.O. Box 9101, Quincy, MA 02269-9101.

NFPA 13, Standard for the Installation of Sprinkler Systems,1999 edition.

NFPA 30, Flammable and Combustible Liquids Code, 1996 edition.NFPA 31, Standard for the Installation of Oil-Burning Equip-

ment, 1997 edition.NFPA 37, Standard for the Installation and Use of Stationary

Combustion Engines and Gas Turbines, 1998 edition.NFPA 45, Standard on Fire Protection for Laboratories Using

Chemicals, 1996 edition.NFPA 49, Hazardous Chemicals Data, 1994 edition.NFPA 50, Standard for Bulk Oxygen Systems at Consumer Sites,

1996 edition.NFPA 53, Recommended Practice on Materials, Equipment, and

Systems Used in Oxygen-Enriched Atmospheres, 1999 edition.NFPA 55, Standard for the Storage, Use, and Handling of Com-

pressed and Liquefied Gases in Portable Cylinders, 1998 edition.NFPA 58, Liquefied Petroleum Gas Code, 1998 edition.NFPA 59A, Standard for the Production, Storage, and Handling

of Liquefied Natural Gas (LNG), 1996 edition.NFPA 61, Standard for the Prevention of Fires and Dust Explo-

sions in Agricultural and Food Products Facilities, 1999 edition.NFPA 68, Guide for Venting of Deflagrations, 1998 edition.NFPA 69, Standard on Explosion Prevention Systems, 1997 edition.NFPA 70, National Electrical Code®, 1999 edition.NFPA 70B, Recommended Practice for Electrical Equipment

Maintenance, 1998 edition.NFPA 77, Recommended Practice on Static Electricity, 1993 edition.NFPA 82, Standard on Incinerators and Waste and Linen Han-

dling Systems and Equipment, 1999 edition.NFPA 91, Standard for Exhaust Systems for Air Conveying of

Vapors, Gases, Mists, and Noncombustible Particulate Solids, 1999edition.

NFPA 230, Standard for the Fire Protection of Storage, 1999 edition.NFPA 325, Guide to Fire Hazard Properties of Flammable Liq-

uids, Gases, and Volatile Solids, 1994 edition.NFPA 328, Recommended Practice for the Control of Flammable

and Combustible Liquids and Gases in Manholes, Sewers, and Simi-lar Underground Structures, 1992 edition.

NFPA 329, Recommended Practice for Handling Releases of Flam-mable and Combustible Liquids and Gases, 1999 edition.

NFPA 491, Guide to Hazardous Chemical Reactions, 1997 edition.NFPA 497, Recommended Practice for the Classification of Flam-

mable Liquids, Gases, or Vapors and of Hazardous (Classified) Loca-tions for Electrical Installations in Chemical Process Areas, 1997edition.

NFPA 499, Recommended Practice for the Classification of Com-bustible Dusts and of Hazardous (Classified) Locations for ElectricalInstallations in Chemical Process Areas, 1997 edition.

NFPA 513, Standard for Motor Freight Terminals, 1998 edition.NFPA 600, Standard on Industrial Fire Brigades, 1996 edition.NFPA 8501, Standard for Single Burner Boiler Operation, 1997

edition.NFPA 8502, Standard for the Prevention of Furnace Explosions/

Implosions in Multiple Burner Boilers, 1999 edition.NFPA 8503, Standard for Pulverized Fuel Systems, 1997 edition.

F-1.2 Other Publications.

F-1.2.1 Chlorine Institute Publication. The Chlorine Institute,342 Madison Avenue, New York, NY 10017.

Properties of Chlorine.

F-1.2.2 NACE Publication. National Association of Corro-sion Engineers, 1400 South Creek Drive, Houston, TX 77084.

Recommended Practices RP01 series.

F-1.2.3 UL Publication. Underwriters Laboratories Inc., 333Pfingsten Road, Northbrook, IL 60062.

Hazardous Location Equipment Directory.

F-1.2.4 U.S. Government Publications. U.S. Government Print-ing Office, Washington, DC 20402.

Title 40, Code of Federal Regulations, Part 761.30.OSHA, Title 29, Code of Federal Regulations, Part 1910.156.

Appendix G Informational Publications


G-1 Additional Reading. 1. Great Lakes Upper Mississippi Board of State Public

Health and Environmental Managers, Recommended Standardsfor Wastewater Facilities (10 State Standard), Health EducationServices, Albany, NY, 1990.

2. Kavassik, Igor J., William C. Krutzsch, Warren H. Fraser,and Joseph Messina, Pump Handbook, McGraw-Hill, Inc., NewYork, 1986.

3. Metcalf and Eddy, Inc.,Wastewater Engineering: Collectionand Pumping of Wastewater, McGraw-Hill, Inc., New York, 1981.

4. Metcalf and Eddy, Inc., Wastewater Engineering: Treatment,Disposal and Reuse (3rd ed.), McGraw-Hill, Inc., New York,1985.

5. Sanks, Robert L., George Tchobanoglous, Donald New-ton, Bayard E. Bosserman, and Garr M. Jones, Pumping StationDesign, Butterworth Publishers, Stoneham, MA, 1989.

6. Water Pollution Control Federation, Wastewater Treat-ment Plant Design, Manual of Practice #8, Alexandria, VA, 1990.

7. Water Pollution Control Federation, Wastewater Treat-ment Plant Operations, Manual of Practice #11, Alexandria, VA1990.


1999 Edition

Index

1999 National Fire Protection Association. All Rights Reserved.The copyright in this index is separate and distinct from the copyright in the document that it indexes. The licensing provisions set forth for thedocument are not applicable to this index. This index may not be reproduced in whole or in part by any means without the express written per-mission of the National Fire Protection Association, Inc.

-A-Abbreviations, list of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .App. EAbovegrade areas

Valve vaults . . . . . . . . . . . . . . . . . . . . . . Table 2-2(30), Fig. A-2-2(d)Ventilation rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 7-3.1.1(3)Wastewater pumping stations . . . . . . . . . . . . . . Table 2-2(18), (19),

Figs. A-2-2(d), (f)Access, fire-fighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8(4), 8-9.2Activated carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-5.4, Table D-1.1

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Activated sludge (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Adjacent (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Administrative controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chap. 8Advanced (tertiary) wastewater treatment . . . . . . B-5; see also Tertiary

sedimentation tanksDefinition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Aeration basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 3-2(7) to (9)Aeration tanks, oxygen . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(13)Aerobic fixed film systems . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(10)Aerobic suspended growth systems . . . . . . . . . . . . .Table 3-2(7) to (9)Air supply systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . see VentilationAlarm systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-3, 8-8(1)

Ventilation system failure . . . . . . . . . . . . . . . . . . . . 5-5, 7-2.9, A-5-5.3Alcohol. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table D-1.1Alternative methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1.2Ammonia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table D-2Ammonia stripping towers . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(18)Anaerobic digesters. . . . . . . . . . . . 6-3.3.5, D-2.4(c), Table 4-2(a)(15),

Fig. A-4-2(a)Control buildings . . . . . . . . . Table 4-2(a)(16), Figs. A-4-2(b) to (e)Gas storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(18)

Anaerobic digestion (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Anaerobic fixed film systems . . . . . . . . . . . . . . D-2.4(n), Table 3-2(11)Anaerobic towers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(11)Anaerobic waste treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.4(b)

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Ancillary structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Application of standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3, A-1-3Approved (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5, A-1-5Asphyxiating atmospheres, and construction materials . . . . . . . . 6-1.2Associations, list of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .App. EAuthority having jurisdiction (definition) . . . . . . . . . . . . . . . .1-5, A-1-5

-B-

Backwash water holding tanks . . . . . . . . . . . . . . . . . . . . . Table 3-2(23)Basins

Aeration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 3-2(7), (8), (9)Catch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 2-2(24), 6-3.1Holding . . . . . . . . . . . . . . . . . . . . . Table 2-2(34), (35), Fig. A-2-2(c)

Belowgrade spaces . . . . . . . . . . . . . . . . . . . . . . . . . . . .see also TunnelsGrit chambers or screening equipment in pits. . . . . . . . . . D-2.4(h)Vaults . . . . Table 2-2(26), (28), (31), (32), (36), (37), Fig. A-2-2(e)Ventilation rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 7-3.1.1(2)Wastewater pumping stations . . . . . . . .Table 2-2(17), Fig. A-2-2(e)

Belt filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(12)Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Biological hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2.2, 5-1Biological treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-4.1Bio-towers . . . . . . . . . . . . . . . . . . . Table 3-2(10), A-6-3.3.3.3, D-2.4(n)Branch sewer (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Breakpoint chlorination tanks . . . . . . . . . . . . . . . . . . . . . Table 3-2(17)Building drain (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Building sewers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 2-2(7)Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Buildings/structuresAnaerobic digester control . . . . . . . . . . . . . . . . . . . Table 4-2(a)(16)Coarse and fine screenings–handling . . . . . . . . . . . Table 4-2(a)(1)Construction materials . . . . . . . . . . . . . . . . . . . . . . 6-3.3, A-6-3.3.3.3Control structures . . . . . . . . . . . . . . . . . . . . . . . . Table 2-2(27), (33)Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Dewatering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(12)Diversion structures. . . . . . . . . . . . . . . . . . . . . . . Table 2-2(25), (29)Effluent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 3-2(25)Grit-handling . . . . . . . . . . . . . . . . . . . . . . .D-2.4(h), Table 4-2(a)(2)Incinerator . . . . . . . . . . . . . . . . . . . . . . . . . 6-3.3.5, Table 4-2(a)(13)Scum-handling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(3)

-C-

Cable tray fires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-8-9(a)Carbon, activated . . . . . . . . . . . . . . . . . . . . . . . . . see Activated carbonCarbon columns or tanks . . . . . . . . . . . . . . . . . . . . . . . . .Table 3-2(21)Catch basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 2-2(24), 6-3.1Cellular plastic materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3.3.7Centrifuges. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(12)

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Chambers

Grit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .D-2.4(h)Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Junction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 2-2(22), 6-3.1Screening

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Ventilation rates . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 7-3.1(1)

Chemical reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-3.4Chemical storage and handling facilities . . . . . . . . . . A-8-9(c), App. DChlorine . . . . . . . . . . . . . . . . . . . . . . . . . . D-5.3, Table D-1.1, Table D-2

Breakpoint chlorination tanks . . . . . . . . . . . . . . . . . . .Table 3-2(17)Contact tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 3-2(17)Oxidation units . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(19)

Coarse and fine screen facilities . . . . . . . . Table 2-2(38), Table 3-2(1)Coarse and fine screenings–handling buildings . . . . . Table 4-2(a)(1)Coatings, interior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1.1, D-2.9Collection systems . . . . . . . . . . . . . . . . . . . . . . . . . . .Chap. 2, Table 2-2

Fire and explosion prevention and protection . . . . . . . . . Chap. 5,A-5-4.1, A-5-4.2, A-5-5.3

Material selection for . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . App. CCollector sewers (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Combined sewers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 2-2(15)

Construction materials . . . . . . . . . . . . . . . . . . . . . . . . .C-4.7 to C-4.8Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Combustible dust . . . . . . . . . . . . . . see Dust, combustible or explosiveCombustible gas detectors . . . . . . 5-4, 7-3.3(3), 8-6.3, A-5-4.1, A-5-4.2,

A-8-6.2, D-4Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Combustible gases . . . . . . . . . . see Flammable and combustible gasesCombustible liquids . . . . . . . . see Flammable and combustible liquidsCombustible materials. . . . . 1-2.4, D-2.9; see also Limited-combustible

materialsDefinition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

CompostDefinition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-8-9(b)

In-vessel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(23)Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(22)

INDEX 820–61

1999 Edition

ConstructionCollection systems. . . . . . . . . . . . . . . . . . . . . . . . 2-2, Table 2-2, A-2-2Fire protection during . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7.1Liquid stream treatment process . . . . . . . . . . . . 3-2, Table 3-2, A-3-2Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chap. 6, A-6.3.3.3.3

Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3, A-6-3.3.3.3Collection systems . . . . . . . . . . . . . . . . . . . . . . . . . . Table 2-2, C-2Liquid stream treatment processes . . . . . . . . . . . . . . . . .Table 3-2Risk assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-3Selection criteria. . . . . . . . . . . . . . . . . . . . . . . . .1-2.4, 6-2, 8-11(5)

Solids treatment processes . . . . . . . 4-2, Tables 4-2(a) and (b), A-4-2Contact tanks

Chlorine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(17)Ozone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(22)

Control structures . . . . . . . . . .Table 2-2(27), (33); see also Anaerobicdigesters, Control buildings

Corrosion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1.3, A-6-3.3.3.3, D-2.9Critical unit processes

Construction materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-3.3.2Fire emergencies in . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8(6)

-D-

Dampers, smoke and fire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-3.3.6Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5, A-1-5Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .see ConstructionDetection systems . . . . . . . . . . . . . .see also Combustible gas detectors

Fire. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3, 6-3.3.6, 8-6, A-8-6.2Flow detection devices, ventilation system . . . . . . . . . . . . . . . . 5-5.1

Dewatering of sludge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .see SludgeDiesel fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table D-1.1Digester gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .see Sludge gasDigesters, anaerobic . . . . . . . . . . . . . . . . . . . . See Anaerobic digestersDisinfection units . . . . . . . . . . . . . . . . . . . . . . . . . . . B-6, Table 3-2(24)Dissolved air flotation (definition) . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Diversion structures . . . . . . . . . . . . . . . . . . . . . . . . Table 2-2(25), (29)Domestic wastewater (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Drainage

Building drains (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Fire protection liquids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7.3Sludge . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.4(b), Table 4-2(a)(25)

Dry wellsBelowgrade or partially belowgrade wastewater

pumping station. . . . . . . . . . . . . . . . . . . . . . . . Table 2-2(17)Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Residential wastewater pumping stations . . . . . . . . . . Table 2-2(12)Sludge pumping stations . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(9)Stormwater pumping stations . . . . . . . . . . . . . . . . . . . . Table 2-2(5)Ventilation rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 7-3.1(2)

Drying beds (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Dust, combustible or explosive . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.8

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Handling of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.4(d)

-E-

Effluent structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(25)Electrical arcs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-3.2Employees, training of . . . . . . . . . . . . . . . . . . . . .8-11.1, 8-11.2, A-8-2.1Enclosed areas

Aeration basins or aerobic suspended growthsystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(8),(9)

Ventilation of. . . . . . . . . . . . . . . . . . . . . . . . . . . .Chap. 7, Table 7-3.1Enclosed space (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Equipment

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Identified (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5

Equipment enclosuresDefinition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Ventilation rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 7-3.1

Essential unit processes . . . . . . . . . . . . . . . . . . . . . . 6-3.3.3, A-6-3.3.3.3

Evacuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8(3)Exhaust air, recirculation of . . . . . . . . . . . . . . . . . . . . . . . 7-3.3, A-7-3.3Exhaust systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3.3.6Existing facilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3.1, A-1-3.1Explosion hazards . . . . . . . . . . . . . . . . .see Fire and explosion hazardsExplosion prevention. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-11Explosion protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2.1, App. DExplosionproof apparatus (definition) . . . . . . . . . . . . . . . . . . . . . . 1-5Explosive dust . . . . . . . . . . . . . . . . .see Dust, combustible or explosiveExplosive limits (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Extinguishers, portable fire. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-2.5Extinguishing systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2.2 to 5-2.4

-F-

Fans, supply and exhaust. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2.2, 7-2.3Filter presses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(12)

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Filters

Belt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(12)Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Pressure or gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(20)Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Trickling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see Trickling filtersVacuum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(12)

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Final pumping stations. . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(19)Finely divided solids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.8Finishes, interior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-1.1Fire and explosion hazards . . . see also Dust, combustible or explosive

Collection systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 2-2Control of sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-11.1Liquid stream treatment processes. . . . . . . . . . . . . . . . . . . Table 3-2Solids treatment processes . . . . . . . . . . . . . . . Tables 4-2(a) and (b)

Fire barrier (definition). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Fire brigades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9, A-8-9Fire dampers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3.3.6Fire emergency plan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8, 8-11.1Fire loading (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Fire prevention . . . . . . . . . . . . . Chap. 5, 8-11, A-5-4.1, A-5-4.2, A-5-5.3

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Management policy and direction . . . . . . . . . . . . . . . . . 8-2, A-8-2.1Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4, A-8-4(g)

Fire protection . . . . . . . . . . . . . . . . . . . . . . 1-2.1, 5-2, 8-5 to 8-7, A-8-6.2Chemical and fuel storage and handling facilities . . . . . . . . App. DCollection systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 2-2Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Liquid stream treatment processes. . . . . . . . . . . . . . . . . . . Table 3-2Management policy and direction . . . . . . . . . . . . . . . . . 8-2, A-8-2.1Solids treatment processes . . . . . . . . . . . . . . . Tables 4-2(a) and (b)

Fire pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2.4.4Fire reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4(7), A-8-4(7)Fire resistance rating (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Fire risk evaluation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1.3, 8-3, A-8-3Fire safety information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4(1)Fire-rated penetration seal (definition) . . . . . . . . . . . . . . . . . . . . . . 1-5Firestops, through-penentration (definition) . . . . . . . . . . . . . . . . . . 1-5Fixed film systems . . . . . . . . . . . . . . . . . .Table 3-2(10), (11), D-2.4(n)Fixed roof anaerobic digesters . . . . . . . . . . . . . . . . . . Table 4-2(a)(15)Flame arresters/checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-6.3Flame spread, low . . . . . . . . . . . . . . . . see Low flame spread materialsFlammable and combustible gases . . . . . . . . . . 8-4(4), D-2, Table D-2;

see also Fuel gases; Sewer gas; Sludge gasGeneration and combustion processes . . . . . . . . . . . . . . . . . 6-3.3.5

Flammable and combustible liquids . . . . . . . . . . . . . . . . . 8-4(4), D-2.7Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5, A-1-5

Flammable/combustible conditions . . . . . . . . . . . . . . . . . . . . . . . . . 5-1Flash dryer (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Flash mixer (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Flash mixer tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(15)Floating cover anaerobic digesters . . . . . . . . . . . . . . . Table 4-2(a)(15)


1999 Edition

Flocculation tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(15)Flocculator (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Flow detection devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5.1Flow equalization tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(3)Fluidized bed reactor (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Foam extinguishing systems . . . . . . . . . . . . . . . . . . . . . . .8-5.1, A-8-9(c)Foamed plastic materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3.3.7Force main (pressure main)

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Fuel gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.1, D-2.6

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Fuel storage and handling facilities . . . . . . . . . . . . . . . . . . . . . . App. D

-G-

Galleries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .D-2.4(m)Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Ventilation rates . . . . . . . . . . . . . . . . . . . . . . . . . . Table 7-3.1(2), (3)

Gas detectors . . . . . . . . . . . . . . . . . . . . see Combustible gas detectorsGases . . . . . . . . see also Flammable and combustible gases; Fuel gases;

Sewer gas; Sludge gasHazardous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.6Toxic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-7-3.3, D-4

Gas-handling equipment . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(12)Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Gasoline. . . . . . . . . . . . . . . . . . . . . . . . . . D-2.7, Table D-1.1, Table D-2Gravity belt thickeners . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(12)Gravity (pressure) filters . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(20)

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Grit chambers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.4(h)

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Grit removal tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(4)Grit-handling buildings. . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(2)

-H-

Hazardous (classified) locationDefinition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Ventilation of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1.2, 7-2.6

Hazardous (classified) locationsCollection systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 2-2Construction materials, selection of . . . . . . . . . . . . . . . . . . . . . 6-2.3Liquid stream treatment processes . . . . . . . . . . . . . . . . . . . Table 3-2Solids treatment processes . . . . . . . . . . . . . . . Tables 4-2(a) and (b)Ventilation systems . . . . . . . . . . 7-1.2, 7-2.2, 7-2.5, 7-2.8, Table 7-3.1

Hazardous gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.6Hazardous waste (definition). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Hazards

Biological . . . . . . . . . . . . . . . . . . . . . . . . . . . .see Biological hazardsFire and explosion . . . . . . . . . . . . . .see Fire and explosion hazardsToxic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see Toxic hazards

Heat treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(14)Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

High-pressure oxidation units . . . . . . . . . . . . . . . . . . Table 4-2(a)(14)Holding basins . . . . . . . . . . . . . . . . . Fig. A-2-2(c), Table 2-2(34), (35)Holding tanks

Backwash water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(23)Sludge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(10)

Holding wells, sludge-blending . . . . . . . . . . . . . . . . . Table 4-2(a)(11)Hose systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2.4.3Hot surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-3.1Hot work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-6-3.3.3.3, D-3.1

Permits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-11.3, 8-11(4)Housekeeping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4(3), 8-11.1Hydrants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2.4.2Hydrocarbon liquids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.7Hydrogen chloride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table D-2Hydrogen sulfide (H2S) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table D-2

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

-I-

Identified (as applied to equipment)Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Ignition, conditions for . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-3Ignition sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-3

Control of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4(5), 8-11.2Imhoff tanks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.4(i)

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Impairments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7, A-8-7Incineration (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Incinerators and incinerator buildings . . . . . Table 4-2(a)(13), 6-3.3.5,

D-2.4(e)Individual residential pumping units . . . . . . . . . . . . . . . . .Table 2-2(9)Individual sewers, residential . . . . . . . . . . . . . . . . . . . . . . .Table 2-2(8)Industrial sewers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 2-2(2)

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Industrial waste (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Inspection, maintenance, and testing

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Fire protection systems . . . .8-5.3, 8-6.2, 8-6.3, 8-7.3, A-8-2.1, A-8-6.2Plastic materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-6-3.3.3.3Preventive. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4(2), 8-11.1Training for . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-11.1

InstallationNon-waterbased fire protection systems. . . . . . . . . . . . . . . . . . . 8-6.1Ventilation systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2Water-based fire protection systems . . . . . . . . . . . . . . . . . . . . . . 8-5.2

Interceptor sewers (definition). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Interior coatings and finishes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1.1Intermediate pumping stations. . . . . . . . . . . . . . . . . . . . .Table 3-2(19)Intermediate sedimentation tanks . . . . . . . . . . . . . . . . . .Table 3-2(14)Intrinsically safe (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Inverted siphons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 2-2(23)In-vessel composting . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(23)

-J-

Junction chambers . . . . . . . . . . . . . . . . . . . . . . . . . .6-3.1, Table 2-2(22)

-K-

Kerosene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.7

-L-

Labeled (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Laboratories, fire protection for . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6Lagoons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 3-2(7)Lightning protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7.2Limited-combustible materials . . . 1-2.4, 6-3.3.2.3, 6-3.3.3.1, 6-3.3.3.3,

6-3.3.4.3, 6-3.3.6, A-6-3.3.3.3, D-2.9Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Liquid stream treatment processes. . . Chap. 3, Table 3-2, A-3.1, A-3-2Listed (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5, A-1-5Local alarms . . . . . . . . . . . . . . . . . . . . . 5-5.2, 5-5.3, Table 5-5.3, A-5-5.3Low flame spread materials . . . . . . . . . . 6-3.3.2.3, 6-3.3.3.1, 6-3.3.3.3,

6-3.3.4.3, 6-3.3.6, A-6-3.3.3.3, D-2.9Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Low-pressure oxidation units . . . . . . . . . . . . . . . . . . . Table 4-2(a)(14)LP-Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.6, Table D-1.1

-M-

Maintenance . . . . . . . . . . . . .see Inspection, maintenance, and testingMaintenance holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 2-2(21)

Construction materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3.1Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Management policy and direction . . . . . . . . . . . . . . . . . . . .8-2, A-8-2.1Materials, construction. . . . . . . . . . . . . . . .see Construction, MaterialsMeasurement, units of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

INDEX 820–63

1999 Edition

Metering vaults, belowgrade . . . . . . . . . . . . Table 2-2(28), (36), (37),Fig. A-2-2(e)

Methane (CH4) (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Mixers, flash

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(15)

Motor oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table D-1.1

-N-

National Electrical Code criteria . . . . . .1-3.3, A-1-3.3; see also Hazardous(classified) locations

Natural gas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.6, Table D-2Natural gas piping . . . . . . . . Table 4-2(a)(20), (21), Figs. A-4-2(f), (g)Nitrification/denitrification tanks . . . . . . . . . . . . . . . . . . Table 3-2(16)

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Nitrogen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table D-2Noncombustible materials . . . . 6-3.3.2.1, 6-3.3.2.3, 6-3.3.3.1, 6-3.3.3.3,

6-3.3.4.3, 6-3.3.5, 6-3.3.6, A-6-3.3.3.3Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5

Nonenclosed (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Nonstructural assemblies . . . .6-3.3.2.3, 6-3.3.3.3, 6-3.3.4.3, A-6-3.3.3.3

-O-

Odor control system areasCollection systems. . . . . . . . . . . . . . . . . Table 2-2(20), Fig. A-2-2(g)Liquid stream treatment processes . . . . . . . . . . . . . . . Table 3-2(26)Solids treatment processes . . . . . . . . . . . . . . . . . . . Table 4-2(a)(24)

Oils. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.7On-site treatment systems. . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(22)

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Open flames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-3.1Outfall sewers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 2-2(13)

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Oxidation ditches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(7)Oxidation units

Chlorine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(19)Low- or high-pressure . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(14)

Oxygen. . . . . . . . . . . . . . . . . . . . . . . . . . . D-5.1, Table D-1.1, Table D-2Oxygen aeration tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(13)Oxygen-enriched atmospheres. . . . . . . . . . . . . . . . . . . . . . . . . .D-2.4(l)

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Ozonation (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Ozone contact tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(22)Ozone generation . . . . . . Table 3-2(22), Table D-1.1, Table D-2, D-5.2

-P-

Penetration seal, fire-rated (definition) . . . . . . . . . . . . . . . . . . . . . .1-5Physical-chemical treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-4.2Physically separated (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Piping

Combined sewers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-4.8Construction materials . . . .6-3.3.2.3, 6-3.3.3.3, 6-3.3.4.3, A-6-3.3.3.3Gas

Natural . . . . . . . . . . . . Table 4-2(a)(20), (21), Figs. A-4-2(f), (g)Sludge . . . . . . Table 4-2(a)(20), (21), Figs. A-4-2(b), (c), (f), (g)Ventilation rates . . . . . . . . . . . . . . . . . . . . . . . . Table 7-3.1(2), (3)

Sanitary sewers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-4.6Storm sewers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-4.3Tunnels for . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .see Tunnels

Pits, sludge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(10)Plant emergency organizations (PEO). . . . . . . . . . . . . . . . 8-9.2, 8-11.1Plastic materials . . . . . . 6-3.3.7, A-6-3.3.3.3, A-8-9(d), D-2.4(n), D-2.9Polychlorinated biphenyls . . . . . . . . . . . . . . . . . . . . . . . . . .8-10, A-8-10Ponds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(7)Positive pressurization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1.2Power sources, ventilation systems . . . . . . . . . . . . . . . . . . . . . . . . 7-2.9Pre-aeration tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(5)

Preliminary treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-2Pressure filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(20)

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Pressure sewers

Collection systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 2-2(6)Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Pressurization, positive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-1.2Primary sedimentation tanks. . . . . . . Table 3-2(6), Fig. A-3-2, D-2.4(j)Primary wastewater treatment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-3

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Private sewers (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Pumping of drainage from digested sludge dewatering

processes . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(25)Pumping stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .D-2.4(g)

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Intermediate or final . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(19)Liquid stream treatment processes. . . . . . . . . . . . . . . . Table 3-2(2)Residential wastewater . . . . . . see Residential wastewater pumping

stationsSludge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(9)Stormwater . . . . . . . . . . . . . . . . . .see Stormwater pumping stationsWastewater . . . . . . . . . . . . . . . . . . see Wastewater pumping stations

Pumping units, individual residential . . . . . . see Individual residentialpumping units

Pumps, fire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2.4.4Purpose of standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2Pyrolysis (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

-R-

Radio communications equipment . . . . . . . . . . . . . . . . . . . . . . . . .8-6.3Reactor, fluidized bed (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Recirculation, of exhaust air . . . . . . . . . . . . . . . . . . . . . . . 7-3.3, A-7-3.3Referenced publications . . . . . . . . . . . . . . . . . . . . . . . .Chap. 9, App. FRelief sewers (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Remote alarms . . . . . . . . . . . . . . . . . . . 5-5.2, 5-5.3, Table 5-5.3, A-5-5.3Residential belowgrade vaults . . . . . . . . . . . . . . . . . Table 2-2(26), (28)Residential control structures . . . . . . . . . . . . . . . . . . . . . Table 2-2(27)Residential diversion structures . . . . . . . . . . . . . . . . . . . Table 2-2(25)Residential sewers . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 2-2(8), (10)

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Residential wastewater (definition) . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Residential wastewater pumping stations . . . . . . . Table 2-2(11), (12),

Figs. A-2-2(b), (e)Risk assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-3Roof coverings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3.3.7Roof decks, metal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3.3.7Rotating biological contactors (RBC) . . . . . . . . . .A-6-3.3.3.3, D-2.4(n)

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

-S-

Sanitary sewers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 2-2(14)Construction materials . . . . . . . . . . . . . . . . . . . . . . . . C-4.4 to C-4.6Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Scope of standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1, A-1-1.1.1Screening chambers

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Ventilation rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 7-3.1(1)

Screening equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.4(h)Scum incinerators . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(7), D-2.4(e)Scum or skimmings (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Scum pits . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(4), D-2.4(a)Scum-handling building or area . . . . . . . . . . . . . . . . . . Table 4-2(a)(3)Scum-pumping areas . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(5), (6)Secondary sedimentation tanks . . . . . . . . . . . Table 3-2(14), D-2.4(k)Secondary wastewater treatment. . . . . . . . . . . . . . . . . . . . . . . . . . . . B-4

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Sedimentation (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Sedimentation tanks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .D-2.4(a)

Intermediate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(14)Primary . . . . . . . . . . . . . . . . . . . . . see Primary sedimentation tanks


1999 Edition

Secondary . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(14), D-2.4(k)Tertiary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(14), D-2.4(k)

Separate nonprocess-related structures (definition) . . . . . . . . . . . . 1-5Sequencing batch reactors . . . . . . . . . . . . . . . . . . . . . . . . . Table 3-2(7)Sewer gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .D-2.3, D-2.6, Table D-2

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Sewers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 2-2

Combined . . . . . . . . . . . . . . . . . . . . . . . . . . . . see Combined sewersConstruction materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3.1Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Sanitary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see Sanitary sewersStorm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see Storm sewers

Shall (definition). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Sludge

Activated (definition). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Cakes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see Sludge cakesDefinition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Dewatering . . . . . . . . . . . . . . . . . . .Table 4-2(a)(25), B-7.2, D-2.4(f)

Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(12)Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Pumping of drainage from digested sludge dewatering

processes . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(25)Drying system . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(b), A-8-9(b)

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Stabilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-7.1Thickener/thickening . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(8)

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-7, D-2.4(b)

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Facility construction materials. . . . . . . . . . . . . . . . . . . . . . . 6-3.3.4

Sludge cakesConveyance equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . .D-2.4(f)Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-7.3Incinerators for. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.4(e)

Sludge gas . . . . . . . . . . . Figs. A-4-2(b) to (g), D-2.2, D-2.6, Table D-2; see also Anaerobic digesters

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Piping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 4-2(a)(20), (21)Processing rooms . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(17)Vent (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Sludge pumping stations, dry well . . . . . . . . . . . . . . . . Table 4-2(a)(9)Sludge storage wet wells, pits, and holding tanks . . . Table 4-2(a)(10)Sludge-blending tanks and holding wells. . . . . . . . . . Table 4-2(a)(11)Sludge-drying systems (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Smoke dampers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3.3.6Smoke detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3.3.6Solids, finely divided . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.8Solids treatment processes . . . . . . . . . . . . . . . . Chap. 4, Tables 4-2(a)

and (b), A-4.1, A-4-2Solvent extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.4(d)Sparks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-3.3Sprinkler systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2.2, 6-3.3.7, 8-5Standard (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Standpipe and hose systems. . . . . . . . . . . . . . . . . . . . . . . . . 5-2.4.3, 8-5Storage

Anaerobic digesters, gas storage . . . . . . . . . . . . . . Table 4-2(a)(18)Chemical and fuel . . . . . . . . . . . . . . . . . . . . . . . . . .A-8-9(c), App. DSludge storage wet wells, pits, and holding tanks. Table 4-2(a)(10)

Storm sewers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 2-2(3)Construction materials . . . . . . . . . . . . . . . . . . . . . . . . . C-4.1 to C-4.3Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Stormwater pumping stations . . .Table 2-2(4), (5), Figs. A-2-2(a), (e)Structures (definition) . . . . . . . . . . . .1-5; see also Buildings/structuresSulfur dioxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table D-2Sumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.4(b)

-T-

Tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 3-2Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.4(b)

Holding . . . . . . . . . . . . . . . . . . . . . .Table 3-2(24), Table 4-2(a)(10)Imhoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2.4(i)

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Nitrification/denitrification . . . . . . . . . . . . . . . . . . . . .Table 3-2(16)

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Sedimentation . . . . . . . . . . . . . . . . . . . . . . see Sedimentation tanksSludge-blending. . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(11)

Tertiary sedimentation tanks . . . . . . . . . . . . . Table 3-2(14), D-2.4(k)Tertiary treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-5Testing . . . . . . . . . . . . . . . . .see Inspection, maintenance, and testingThrough-penentration firestop (definition). . . . . . . . . . . . . . . . . . . 1-5Towers

Ammonia stripping . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 3-2(18)Anaerobic. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 3-2(11)Bio-towers. . . . . . . . . . . . . . . . . .D-2.4(n), Table 3-2(10), A-6-3.3.3.3

Toxic hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2.2, 5-1Construction materials and . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1.2Control of sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-11.1Gases. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1.1.1, A-7-3.3, D-4

Training, employee . . . . . . . . . . . . . . . . . . . . . . . 8-11.1, 8-11.2, A-8-2.1Transport systems . . . . . . . . . . . . . . . . . . . . . . . . see Collection systemsTrickling filters. . . . . . . . . . . . . . . .Table 3-2(10), A-6-3.3.3.3, D-2.4(n)

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Trunk sewers (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Tunnels

Natural gas or sludge gas piping . . . . . . . . .Table 4-2(a)(20), (21),Figs. A-4-2(f), (g)

Ventilation rates. . . . . . . . . . Table 4-2(a)(20), (21), Table 7-3.1(2),Figs. A-4-2(f), (g)

-U-

Ultraviolet disinfection unit . . . . . . . . . . . . . . . . . . . . . . .Table 3-2(24)Unit processes . . . . . . . . . . . . . . . . 6-3.3.2 to 6-3.3.5, A-6-3.3.3.3, D-2.4Utilization equipment (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

-V-

Vacuum filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(12)Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Valve vaultsAbovegrade . . . . . . . . . . . . . . . . . . . . . . Table 2-2(30), Fig. A-2-2(d)Belowgrade . . . . . . . . . . . . .Table 2-2(26), (31), (32), Fig. A-2-2(e)

Vaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see also Valve vaultsDefinition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Metering, below grade . . . .Table 2-2(28), (36), (37), Fig. A-2-2(e)

Vent, sludge gas (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Chap. 7, A-7-3.3, D-4

Collection systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 2-2Construction materials . . . . . . 6-3.3.2.3, 6-3.3.3.3, 6-3.3.4.3, 6-3.3.6,

A-6-3.3.3.3For fire and explosion control . . . . . . . . . . . . . . . . . . . . . . . .8-11(1)Liquid stream treatment processes . . . . . . . . . . . . . . . . . . Table 3-2Monitoring and signaling systems . . . . . . . . . . . . . . . . . .5-5, A-5-5.3Solids treatment processes . . . . . . . . . . . . . . Tables 4-2(a) and (b),

Figs. A-4-2(b to (g)Ventilation rates . . . . . . . . . . . . . . . . . . . .1-2.3, 7-3, A-7-3.3, Table 7-3.1

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Volatile liquid (definition). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

-W-

Waste backwash water holding tanks . . . . . . . . . . . . . . . .Table 3-2(23)Waste treatment, anaerobic

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Sludge treatment processes . . . . . . . . . . . . . . . . . . . . . . . . .D-2.4(b)

Wastewater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .B-1.1Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5, B-1.1Domestic (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Wastewater holding basins. . . . . . . . Table 2-2(34), (35), Fig. A-2-2(c)

INDEX 820–65

Cou/D 1999 Edition

Wastewater pumping stations . . . . . . . . . . D-2.4(g); see also Residentialwastewater pumping stations

Abovegrade . . . . . . . . . . . . . . Table 2-2(18), (19), Fig. A-2-2(d), (f)Belowgrade or partially belowgrade . . . . . .Table 2-2(17), A-2-2(e),

Fig. A-2-2(e)Construction materials . . . . . . . . . . . . . . . . . . . . . . . .6-3.2, Table 2-2Dry wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 2-2(12), (17)Ventilation of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Chap. 7Wet wells . . . . . . . . . . . . . . . . . . . . Table 2-2(11), (16), Fig. A-2-2(c)

Wastewater treatmentAdvanced. . . . . . . . [see Advanced (tertiary) wastewater treatment]Elements of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1.2Primary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-3

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Secondary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-4

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Wastewater treatment processes. . . . . . . . . . . . . . . . . . . . . . . . . App. B

Fire and explosion prevention and protection. . . . . . . . . . Chap. 3,Chap. 5, A-3-1, A-3-2, A-5-4.1, A-5-4.2, A-5-5.3

Gases commonly found in . . . . . . . . . . . . . . . . . . . . . D-2, Table D-2

Schematic flow and process diagram . . . . . . . . . . . . . . . . . . Fig. B-1Water spray fixed systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-5Water supplies, fire protection . . . . . . . . . . . . . . . . . . . . . . . 5-2.4, 8-5.1Water-based fire protection systems . . . . . . . . . . . . . . . . . . . . . . . . . 8-5

Impairments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7, A-8-7Wells

Dry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see Dry wellsHolding, sludge-blending . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(11)Wet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see Wet wells

Wet wellsDefinition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Residential sewer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. A-2-2(b)Residential wastewater pumping stations. . . . . . . . . . Table 2-2(11)Separate or combined sanitary sewer . . . . . . . . . . . . . . Fig. A-2-2(c)Sludge storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4-2(a)(10)Storm sewer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. A-2-2(a)Stormwater pumping stations . . . . . . . . . Table 2-2(4), Fig. A-2-2(a)Ventilation rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 7-3.1(1)Wastewater pumping stations . . . Table 2-2(11), (16), Fig. A-2-2(c)