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Anderson, StePhen P.Wastes to R6sources: Appropriate /Technologies forSewage Treatment and Conversion.National Center for Appropriate Technology, Butte,Mont.Department of Energy, Washington, DC. AppropriateTechnology Program.

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MF01 Plus Postage. PC Not Available from EDRS.Case Studies; Environmental Standards; FederalPrograms; Re'cycl g; *Sanitation; Solid Wastes;*Technological A vancement; Technology; UrbanImprovement; *Waste Disposal; *Wastes; Water Quality; ,11.

*Water Treatment*Appropriate Technology; Water Treatment PlantsA

Appropriate technology options for sewage ,managementsystems are explained in this four-chapter report. The use ofappropriate technologies is advocated for its health, environmental,and economic benefits.. Chapter 1 presents background information onsewage treatment in theeUnited States and the key issues 'acingmunicipal sewage managers. Chapter 2 outlines conventional sewagetreatment systems and introduces alternative and innovativetechnologies. Chapter' 3 presents case studies of the experiences offive municipal systems, including the technologies involved, costs,

-project problems and subsequent solutions, and current status. Theseprojects (funded by the Department of Energy's Appropriate TechnologySmall Grants Program) focused on verMicomposting, apaerobicprimarytreatment, digeSter gas recovery and use, electricity from effluentoutfall, and an energy audit/conservation plan. Chapter 4 reviewssome of the lessons learned and examines future possibiliities. Eachchapter includes a. glossary, and abbreviations list,references/sources, and a list of agencies or individuals able toprovide further assistance. A list of selected sewage treatmentprojects from the Department of Energy Appropriate Technology SmallGrants Program is included in an appendix. (ML)

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DOE ICE / 15095-7

WASTES TO RESOURCESCT July 1983u-Ntsj(---vo APPROPRIATE TECHNOLOGIES F9RIjj S EWAGE TREATMENT AND CONVERSION

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- WASTES TO RESOURCES:APPROPRIATE TECHNOLOGIES FOR

TREATMENT AND CONVERSION

Prop:trod fors I.U.S. Department of EnergyAssistant Secretary, Conservation and Renewable EnergySmall Scale Technology BranchAppropriate Technology ProgramUnder Contract No. DE-AC01-82CE15095

July 1983

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ONTENTSIntroduction JP`

Chapter 1:Se Wage Cdllection and Treatment.: The Major losuesHealth and PollutionWater and Soil ContaminationLaws 'and Regulations

rpnancing

Chapter 2;Sefage Management, Treatment, Conversion, lJse, and DisposalTreatment Systems

Conventional Centralized PlantsLagoons',AquacultureLand Treatment

Management and Use of SludgeSystem-wide Management Strategies

Decentralized Systems

A

Chapter 3:Case Studies: Appropriate Technology at WorkEnergy Audit and Conservation PlanDigester Gas Recovery and UseProducing Electricity From Effluent OutfallAn Innovative Anaerobic Primary Treatment SystemVermicomposting: WormsUsed To Proctss Sludge

Chapter 4:Lessons Learned and Future Directions

Appendix A:Selected Sewage Treatment Projects Irom the DORppropriateTechnology Small Grants Program

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While It is Impossible to mention every individual who has helped in the development of this document, the followingindividuals and organizations are recognized for their special contributions: Stephen P. Anddrson, author; StephenG. Thomas and Diane,Smith, editors; Hans Haumberger, technical illustrator; Tom Cook, graphic designer; andthestaff of the National Center for Appropriate Technology; Ray Dinges, Texas Health Department, Austin, TX; WilliamStewart, Biological Engineer, Encinitas, CA; Stan S ith, EPA, Denver, CO; the DOE Appropriate Technologygrantees and their staffs. In addition, the cooperatio and information offered by the following U.S. Government

Is greatly appreciated: EPAthe Municip nvironmental Resource Laboratory (Cincinnati, OH), theOffice of Water Pollution_Operations ( Washington), and the FIT-Kerr Environmental Research Laboratory (Ada,OK); NASAthe Nationpl4pace Technology Laboratory (Ray St. Louis, MS); and the Department of interiortheOffice of Water Researbh and chnology (Washington)."TNe report wee psrepated as an AAA sponsored by en atom of the Untied Stelae Government. NOther the United States Govern.meat nee any army thereof, or any of their employees, makes any warranty, expressed or Implied, or 1911.11fRIM ant lopef Itabatty or meson.& INV fer die WipWOO'f,-0011106001111, Of seseminese ef 'any Information, apparatus, product, or process diseteeed, or represents that Its usemold net Infringe privately owned IM.. fleferenew herein fe any spindle oommeistal 'rafted, pram% or rowdy* by trade nem% trademark,e tansfeetwrer, or elherwiee, dose not neeeseadly Oftelltilie Of Imply Its , resernmetidetten,'or favoring by the UMW SlatesGOVIIIMINIt el any *patsy Memel. Ms slows and °Odom of outliers do nel mitreeserfly state a reflect thorn of the UnitedStates Oftiornment er any army thereof."

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Managers of municipal sewage systemsacross the country are confronted with aseemingly contradictory set of challenges.How can they reduce pollution and yetoperate within their shrinking city budgets?How can they conserve energy and yeteffectively process a growlicg volume ofsewage?

Appropriate technologies have shownthat they can provide some of the answersand at the same time help sewage plant'managers operate systems more efficientlyand with less threat to the environment andhuman.health. And there are other benefitsas well. For example, the problem of reduc-ing pollution does not have to be expensive.On the contrary, by using appropplatetechnologies, money can be saved in thelong run by conserving resources throughrecycling wastes. ^

More than two dozen projects concernedwith wastewater treatment, conversion, oruse were funded by the U.S..Department ofEnergy's Appropriate Technology SmallGrants Program. These projects wereawarded to individuals and .groups as di=verse as fiomeowners, farmers, and theworld's largest wastewater treatment plantin Chicago. But all the grantees shared acommon concern: that it is simply too ex-pensive, both at the broadest ecologicallevel and at the increasingly critical eco-nomic level, to continue wasting materialsthat are, in fact, resources.

They also shared a common goal of re-ducing sewage treatment costs. Many citiessaved money by implementing appropriate.technologies that improve, upgrade, orexpandoexisting systems. Others in thefield tested basic new ideas, constructedbench-scale systems, or used appropriatetechnologies in innovative ways at lull-scale. As . the various technologies weretested and implemented, two main lessonsbecame dear: significant amounts of theenergy and water resource* going intosewage collection and treatment can beconserved, and wastes can be convertedoresources, Both conservation and Waconversion can save the taxpayers' money,and at the same time can often reducepollution.

Wastes to Resources: Appropriate Tech-nologies for Sowctip Treatment and Con-version is intended to introduce sewage

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system managers, municipal administrators,and interested professionals and citizens toa general background of appropriate tech-,nology options for sewage management.Many of these technologies have shownthat they work on existing, traditional sew-age systems; others may hold promise forthe future.

Chapter One presents background infor-mation on sewage treatment in the UnitedStates and the key issues facing municipalsewage managers, Chaptei Two outlinesconventional iiewagg treatment systemsand introduces alternative and innovativetechnologies.

The case studies in diapter Three pre-sent the experiences of five municipal sys-tems: the technologies involved, the costs,the project problems and subseqUent solu-tions, the energy considerations, and thecurrent status of each project. All five werefurlded through, the U.S. Department ofEnergy's Appropriate Technology SmallGrants Program. (Appendix A lists otherprojects funded by the Department of En-ergy under this program.)

Chapter Four reviews some of the lessonslearned and future possibilities for theapplication of appropriate technologies tosewage treatment and conversion. Eachchapter includes a glossary an(71 abbrevia-tion list, reference sources, 4nd a list ofagencies and people who can provide fur- t

ther assistance*.

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CHAPTER ONESEWAGE COLLECTION AM') TREATMENT: THE MAJOR ISSUES&

treated, and can contaminate suLface ra-ters or ground water. Those thai are notremoved or treated generally are found insludge. Kmmonium and nitrates are oftenpresent in the liquid effluent and are ofparticular concern because they can beharmful to aquatic life.

StudiEth- hlso indicate that trace, metals,'such as lead, mercury, cadmium, and zincoften are not removed by sewagi) treatmentplants. High levels of heavy metals areknown to cause severe neurological symp-toms, chromosome damage, and even deathin humans.

American towns and cities face manybkoad challenges related to sewage collec-tiM and treatment. They have to protecthuman and environmental health, to main-tatn or improve water and air quality, anduse land, water, and energy effectively.They also have t cope with a mace of local,state, and. Fe al regulations. And theyhave to dec de how to spendor not tospendgreat sums of money to build andoperate sewage systems. Appropriate tech,nologies can be applied to help meet all ofthese challenges while saving costly energy.

GLOSSARYInorganic Compounds:Those compounds .lockingcarbon but including the car-bonates and cyanides: nothaving organized anatomicalstructure of animal or vege-table life.Organic Compounds:Referring to or derived fromliving organisms. In chemis-try, any compound contain-ing life.

Semmes):The waste matter from do-mestic, commercial, and in-dustrial sources carlqed by$11w1113.

Shift*:Mixture of organic and inor-ganic substances separatedfrom the sewage; generallywastewater with 3 to 8 per-cent solids.

A

HEALTH *ND POLLUTION

Historically, inadequate sewage handlingand treatment has been directly responsiblefor outbreaks of diseases such as typhoid and

-cholera. Improved sanitation has largelycontrolled waterborne diseases in bothurban and rural areas. HoWever, modernresearch has shown that organic and inor-ganic compounds may cause- other long-term health problems such as cancer and'genetic defects.

The U.S. Environmental Protection Agency(EPA) lists over 1,000 organic and inor-ganic .compounds that are disposed 'of nthe wasteviater of a typical home.than one hundred of these are known tinepotentially dangerous . when dischargedinto surface waters or ground water. Manyadditional hazardous compounds are partof commercial and industiial wastewaters.

A survey in 1982 for the EPA's Toxic-Pol-lutants Control Pp:50'am found that a me-dian of only 72 percent of the toxic organiccompound entering municipal sewageworks was removed. In many cases, inor-ganic ,compounds gr viruses pass throughsewage works without being separated or

CHAPTER CtI7

WATER AND SOIL CONTAMINATION -,About -22 billion gallons of wastewater'

pass through municipal systems every day.Much of this wastewater eventually reachesdrinking water sources.

Together, septic tanks and cesspools arethe greatest sources of wastewater dischargeinto the ground. Also, ope-fourthof themunicipal treatment systems in the countryuse some form of wastewater treatmentlagoon, and it is estimated that 50 milliongallons of wastewater leak frot. these la-goons every day. An additional 2.3 billiongallons of untreated and treated wastewaterare applied daily to the land. If this waste-water is improperly treated or applied, itcan pollute -drinking water sources or cancontaminate the soil with undesirable con- 'centrations of chemicals.

Water pollution can be caused by mate-rials in sewage that inhibit or encouragebiological growth. Toxic substances canpollute water and kill both plants and ani-mals. Inorganic materials, such as phospho-rus and nitrogen; can 9ver-stimulate plantgrowth which depletes "the water's oxygenand thereby causes massive fish kills.

Modern, mechanical 4aste-water troatdient plants typi-cally use large amounts ofenergy and chemicals andrelatively little land. Alter-native biological wastewatertreatment systems generallyuse small amounts of exter-nal energy but require largsiramounts of land. In both in-stances sewage treatmerttbyproducts can be used ben-eficlaliy on the land.

y, disturbed land is:reclaimed with sludge,

wastewater is being used forIrrigation, and sewage treat-ment Is being integrated withother land uses: If all of thenutrients In the country'ssewage wars recycled andused on the land, it wouldprovide 12 percent of the cur-rent demand for commercialnitrogen fertilizers and 20percent of the demand forphosphorbs fertilizers, with-a total value of over $1 billionper year.

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SEWAGE COLLECTION AND TREATMENT: THE MAJOR ISSUES

LAWS AND REGULATIONS 1111

There have been many environmentallaws and regulations developed iu recent

years that apply to sewage system-11, mostsignificantly at the Federal level. However,in several cases, such as under the CleanWater Act, the states are en'codraged to be'active partners. As of January, 1983, 35states now issue permits and enforce com-pliance to meetthe minimum Federal stan-dards. On the other hand, health and land'use related regulations are most often theresponsibility of county and municipalauthorities.

Major sewage treatment projects face agpmut pf regulations, frOm environmentalimpact statements to local zoning permits.More frequently, local siting and zoningproblems are proving t9 be the most diffi7cult to overcome because of persistent mis-conceptions and. apprehensions about thenature of sewage treatment. Becauhe somany considerations affect the siting, con-struction, and operation of sewage treatmentfacilities, a full survey of, environmentaland land use factors, and an .exhaustivereview of regulations which may pertain,areimperative first steps in planning a sew-age system.

Early Federal laws recognized that waterquality had to be flnproved, but these weregeneral in nature and did not specify themethods to achieve cleaner water. The Fed-

' eral Water Pollution Control Act Amend-ments of 1972 set ambitious goals to restoreand Maintain the nation's water quality,and it allocated $18 billion (kg fiscal years1973-75) to improve municipal sewage col-lection and treatment in the country. Theemphasis at that time, however, was formunicipalities to act quickly to cltitin upwater, which tended to discourage innova-tion and favor the constructiQktA systemsbased on standard designs.

FINANCINGI

The major source of federal funding formunicipal sewage collection and treatmentfacilities is the EPA's Construction GrantsProgram, authorized by the Clean WaterAct. This program provided over $34 billionfor the construction or improvement ofsewage facilities between 1972 and 1983;states and municipalitiqp contributed'additional $15 billion. The environmentalProtection Agency estimates thet, through

CHAPTER ONE

the year 2000, an additional $70 billion willbe needed to construct or improy,e sewpgRfacilities. In 1982, the Constsuction GrantsProgram provided as much as 75 percentthe funds required for construction of sew-age facilities, and it provided as-much as85 percent (proposed to be reduced' to75 percent in 1984) of the funding for alter-native or innovative treatmen(systemscomponents. Funds under this program,iwhich may also cover land costs, are allo-

Vetted on a priority basis so that the mostserious 1ources of pollution are dealt withfirst.

The Innovative and Alternativ Programwas included in- the Clean Mater Act of1977 to foster the development and,use oftechnologies that reclaim and re-use water,recycle wastewater constituents, eliminatethe discharge of pollutants, or recoverenergy. By September 1981, 1,035 projbctshad been funded to use innovative andalternative technologies. These projectshave included aquaculture, composting,land application, on-site treatment, andsolar applications.

Other Federal programs have been estab-lished intermittently, such as the Depart-ment of Energy ApprOpriate TechnologySmall Grants Program, that provide fundsthat can be used for sewage treatmentprojects...

Most states prOvide ome form of finan-cial assistance either through direct grantsor loan programs. In many cases, statecontributions are inversely proportional toFederal contributiorks. Federal and statefinancing rarely combine to pay 100 percentof project costs, although there are situa-tions when funding mixes can meet all costs.

The two traditi bources of local fund-ing are user es or municipal bonds. Theprimary lim on with municipal bondissues is the cur ent indebtedness of thecommunity; a city with a significant debtwill probably be unable to issue bonds.Recently, some districts have used tax-fief:1,industrial developnient bonds to financeprojects.

A Amber-of alternative financing option;are being developed for municipalities,many of them involving the 'cooperation of

cities and local businesses. This may beparticularly appropriate if it is necessary topretreatrindustritil wastes entering the mu-nicipal system. With the significant capitaloutlay required for sewage facility construe-tion, operation, and , maintenance, every.,financing option should be explored.

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For more informatioron theEn4ironmental Protection.Agents Innovative and Al-ternative Program:

Region I (CT, ME MA. NH,RI, VT)

Jim LordJFK Federal Building,

bird FloorBoston, Massachusetts02203Water Division Director

(Acting): Richeird KotkIllyTel. 617.223-5604 -

Regionil (NJ, NY, PR, VI)Jerry Clotola26 Federal Piazri, Room 805'4New cork, New York 10007Water,Division Director:

William MuszynsklTel. 212-26.4-9596 ' -

Region III (DE, MD, PA,VA, WV, QC)

Lee MurphyCurtis Building6th ancPWalnut StreetsPhiladelphia, Pennsylvania

19106Water Division Director:

Greene Jones .

Tel. 215-597-9131

Region IV (Al, GA, FL, MS,NC, SC, TN, KY)

John Harkins .345 Courtland Street, NEAtlanta., Georgia 30365Water Division Director:

Paul TrainsTel. 404-881-3633

Region V (IL, IN, OH, MI,/144, WI)

Steve Poloncs,ikSouth De'rborn Streetago, 1111rials 60604

visiontilr,ect6r:in

3.2314

n VI (V,LA,X, NM) ..

Ancil JonesFirst Federal Building -1201 Elm Street

\ Dallas, Taxosi76270Water Division Director:

" :MirorcKuncisqnT.I. 214:767-9905

RegiOnVII (IA, 41480, NE)Mario Nuncio324 E. 11th St.Kansas City, Misiouri 6.4106Water Division Director:

Allen AbramsonTel. 816-374-2725

Region VIII (CO, UT, WY,MT, ND, SD)

Stan Smith1860 Lincoln StreetDenver, Colorado 80203Water Division Director:

Max DodsonTel. 303-837-2735

Region IX (AZ CA, GU,HI, NV, Aniican Samoa,Trust Territories of the

Irvt.Terzich

cific)

215 Fremont Street.San Francisco, California -f

94105 .

Water.Division Director:Frank Convington

Tel. 415-974-8106

Region X (AK, ID, OR, WA)Tom Johnson1200 6th StreetSeattle, Washington 98101Water Division Director:

Robert BurdTel. 206-442-1413

WHO TO CONTACT

California Municipal Rev-enue Sources HaLeogue of California Cities,

sSacramento, CA, January1982.

AI

Hatheway, S.W., Sources ofToxic Compounds in House-hold Wastewater, EPA-600/2-80-128, NTIS, Springfield,VA, August 1980.

Innovailve and Alterna-tive Technology Assess-ment Manual, EPA- 430/9-78.009, NTIS, Springfield, VA,February)980.

Kormondy, E,J., Conceptsof. Ecology, Prentice -Hall,Inc., Englewood Cliffs, NJ,1969.

Miller, D.W., et al. (Ed),Waste Disposal Effects onGround Water, PremierPress, Berkeley, CA, 1980. .

Rybczynski, W., et al., Ap-propriate Technology forWater Supply and Sanita-tion: Low-cosi TechnologyOptions for Sanitation, AState-of-the-Art Reviewand Annotated Bibliogra-phy, World Bank, Washing-ton, DC, February 1982.

Sewage Treatment Con-struction Grant Manual,The Bureau of National Af-fairs, Inc., Washington, DC,January 1983.

Southwick, C.H., Ecologyand the Quality of Our En-vironment, Van NostrandReinhold Cgmpany, Inc.,New York, NY, 1972.

U.S. Environmental Protec-tion Agency Sludge TaskForce and Office of WaterPrograms Operations Man-agement and Advisory Brief-ing, U.S. EPA, Cincinnati,OH, unpublished, September1982.

REFERENCES

CHAPTER ONE

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CHAPTER TWO"SEW ArGE MANAGEMENT, TREATMENT,' CONVERSION, USE, AND DISPOSAL

Knowing which appropriate technologiescan be used to solve sewage treatment prob-lems requires an understanding of present

.practices. Conventional systems and alter-natives already .in use provide the contextfor appropriate technology applications. ,Inthis chapter,-an array of existing technolo-gies is briefltlintroduced and reviewed.

GLOSSARYAerobic:Life or biological processesthat Can 'occur only in thepresence of oxygen.Anaerobic:Life or biological processesthat occur in the absence ofoxygen.DOD:Biochemical oxygen demand.

Centralized SewageTreatment:The collection and treatmentof `sewage from many sourcesto separate pollutants andpathogens from t waste-water.Effluent:The treated wastewater dis-charged by sewage treat-ment plants.

,Ivapotranspiration:The water released fromplants as they grow and theevaporation of water fromplant surfaces and a/diacentsoil.Facultative Ponds:Ponds having an aerobic zoneon the top and an anaerobic

gr

zone on the bottom.

InfiltrationsLeakage of ground- waterthrough poor idnts, etc. intothe sewage collection-system.

Influent:Wastewater going into thesewage treatment plant.MOD: ..Million gallons per day.Percolation:The filtering of a liquidposited through a mediumwith many fin. spaces.Polishing Treatment:The final sewage treatmentprocess to further reduceBODs, SS, and other pollu-tants.Reci elation: ,

Ret ning a fraction of the*HI ant outflow to the inletto dilute incoming waste-water.UsSuspended Solidi.

TREATMENT SYSTEMS

Lagoons. .

Lagoons require large amounts of landand are best suited to warm and moderateclimates. However, lagoons continue to bea useful alternative, particularly for smallercommunities, because of the low construc-tion costs and minimal operating require-

- ments. Lagoons gerirally do not treat waste-water as effectively as conventional plants,but they can be used in many parts of thecountry, because systems with low flowrates are permitted to release higher levelsof suspended solids than larger systems.Odor and mosquitoes are common iproblemswith laggons, and the nutrients and Mineralsthat settle to the bottom are rarely reclaimed.There are generally three types of lagoonsthat are used for all levels of treatment:anaerobic;aerobic, and facultative.

Anaerobic lagoons are relatively deep,with minimal dissolved oxygen except atthe surface. Levels of BOD5 and SS arecommonly reduced by 50 to 70 percent.

Aerobic lagoons are generally less than2-feet deep and use the action of wind, sun-light, and algae to convert wastes. Whiletreatment efficiencies can be very high,the algae that convert the wastes can createhigher BOD, and SS conditions than thewastewater had originally. To achieve max-imum results, lagoons must be deeper anduse mechanical aeration, 'which consumeslarge amounts of energy.

Facultative lagoons have an aerobiczone on top and an anaerobic zone on thebottom. This requires depths of about 12 feetat the inlet to as little as 1 feet at the outlet.Either a preliminary, treatment stage orrecirculation is required to keep the surfaceone aerobic. Sludge build-0 in wellanaged facultative ponds is relatively

low, and a trench at the entrance end canbe used to ,accumulate the sludge that is

-produced (see Figure 2.2).

Conventional Centralized Plants

Most of the urban centers in the UnitedStates are served by conventional treatmentplants 'which use mechanical andprocesses to break down and treat sewage.Most of these plants incorporate four basicstages: preliminary, primary, secondary,and advanced (see Figure 2.1). Wastewatertreatment'is usually concluded with disin-fection of the effluent, most often bychlorination.

Aquaculture

Aquaculture treatment of sewage beganto develop when hyacinths were added totraditional lagoons to produce cleanerwater and reduce odors. Water hyacinthsare most commonly used to treat wastewater,but aquaculture systems can also use otheraquatic plants, animals, or both.

If water hyacinths are used to treat waste-water from facultative ponds, they are capa-ble of producing very clean effluent. Hya.-cinth ponds alone can be very effective in

CHAPTER TWO 6

[,14OR

SEWAGE MANAGEMENT, TREATMENT, CONVERSION, USE, AND DISPOSAL

Sawagetrootment perfor-mance is commonly moo- frsured In terms of biochemicaloxygen demand, suspendedsolids, and phosphorus.

The amount of oxygenneeded by bacteria and ofhermicroorganisms to oxidizisorganics for food and energyIs called laothornicol oxy-won demand (BOD). elo-chsmIcol oxygen demand Is

process that occurs ovirperiod of time, and It is com-monly measured for a f Iv.-day period. referred to asPOD. Biochemical oxygendemand Is an important wa-ter quality measurement,because the type of aquaticlife is determined by theamount of oxygen in thewater.

Waste particles suspendedin water, referred to as sus -pended solids (SS), can har-bor harmful microorganismsand toxic chemicals. Sus-pended solids cloud the wa-ter and make disinfectionmore difficult and costly.

Phosphorus (P), In Its In-organic forms is necessaryallome levels, but when ItIs concentrated it becomespollutant that can overloadecosystems beyond their ca-pacity to assimilate it. Thisnot only upsets the biologicalbalance:tut also diminishesthe natural capacity of theenvironment to break downand use wastes.

t=1I SLUDGE I

TYPICALRAW SEWAGE

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PRELIMINARY TREATMENT

.W41.4 1=1 A NI...wr ppm.* MHP ripMpolowl.

PRIMARY TREATIL T11 mfortal 104014 14.1. IFrFMSA KM ihm."*".pAAJA. refhi.1ns.

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Figure 2.1 Measuring Sewage Treatment Performance

treating wastewater if recir6ulation is used.Hyacinth ponds are 2-, to 3-feet deep andtypically require 5 to 15 .acres per milliongallons per day to achieve secondary toadvanced treatment water quality (see Fig-ure 2.3). f139,nds are primarily aerobic, andabout one-fifth of the surface is kept clearedof plants to help maintain aerobic condi-tions at the surface. Water hyacinths canbe harvested for use as a fertilizer and soilconditioner, or as an animal feed supple-ment. Hyacinths and sludge.also make anideal compost.mixture.

Full-scale hyacinth treatment systemsare now operating in Texas, Florida, andMississippi. The largest hyacinth pond sys-tem in the country is' being planned forStockton, California.

Hyacinth ponds are used today only inwarm climates because the plants die whenexposed to freezing temperatures (see Fig-ure 2.4).- Duckweed, watercr , and cat-tails are used in cooler cl ates. In coldregions, other plants that normally toleratecolder weather, such as European iris, or

'new genetic strains of plants may provide,alternatives. Mosquitoes can be a problemwith all lagoon systems, but they can be

'Controlled if fish are added tq aquaculturetreatment systems. a '

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Figure 2.2 Typical Facultative Lagoon

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Figure 2.3 Water Hyacinth Treatment Basins

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SEWAGE MANAGEMENT, TREATMENT, CONVERSION, USE, AND DISPOSAL

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rLand`fmatment

,

Wastewater and sludge are treated byland'application in about 1,200 locations inthe United States. If properly handled,latd treatment can be more. effective thanconventional secondary treatments andoperation and maintenance costs are usu-ally low. It requires larger areas of landthan conventional plants, it is well-suited to small community needs, especiallyin agricultural areas. Three main landapplication techniques are used: slow-rate,,rapid infiltration, and overland flow. Thesuitability and effectiveness of these. tech-niques depend on the availability of landwith the proper characteristics (see Table2.1) When trace metals are a problem, lime)or other pH adjusters must be applied tostabilize those metals on acidic soils. Con-sequently, operating costs are generallylower with &kaif-le galls.

Slow-rato is the most popular and reliableland treatment method (see Figure 2.5).Primary treatment is required to remove

Characteristics

solids that might clog the equipthent andreduce BON levels to control odor prob-lems. The sewage is treated when the vege-tation absorbs and uses the sewage nutri-ents and water. What isn't absorbed by theplants either eisporatere percolatesthrough the soil.

With rapid Infiltration, wastewater Isspread in porous basins 4and treatment oc-curs in the soil (see Figure 2.6). Wastewaterukially receives primary treatment to reducesolids and BOD5. trogen and salt build-upin the soil may imiting factors to thisand other land trea ent methOds. A build-up of nitrogen can inc se the concentra-tion cilhrotes, which nre easily leached.out tMe soil, and can contaminate groundwater. High salt levels restrict the ability ofplants to take up water and nutrients. ,

With overland flow, wastewater is ap-plied upslope and allowed to flow downhillthrough vegetated surfaces to runoff col-lection ditches and into lagoon basins (seeFigure 2.7). Preapplication treatment isnormally used to remove grease and somesolids. Overland flow is an excellent pol-ishing treatment if it follows conventienalsecondary treatment.

In a variation of land application treat-ment, wetlands can be used to treat waste-water in areas where the water table is atthe surface. Wastewater is treated by thebiological processes of complex ecosys-tem, as well as by ev'potranspiration andpercolation. Wetland systems can achievehigher removal efficiencies than mechan-ical systems. Natural wetlands, such asmarshes and swamps, or artifiCial wetlandshave been used to treat both raw and treatedwastewater (see Figure 2.8).

Application Method

Slop.

Slow-Sete

Less than 20% on cultivatedland: less than 40% on non-cultivated land.

Soil Permeability Moderately slow to moder-ately ,rapid.

Depth to Ground Water 2 ft to3 ft (minimum).

Climatic Restrictiops Storage often needed forcold weather andprecipitation.

Rapid inflitrallon Overland Flow

Not critLcal: ive slopesrequire 1nuch thwork.

Rapid (sands, loamy sands).

10 ft (lesser depths are ac-ceptable where undrdrain-age Is provided).

None (possibly modify op-eration in cold weather).

Slopes of 2 to 8%.

Slow (cloy*. silts; and soilswith impermeable barriers).

Not critical.

Storage often ndd forcold weather.

Land Area per MGD 57 to 560 ac 2 to 57 ac 16 to 111 ac

Source: Operation and Maintenance Considerations for Land Treatment Systems, EPA 600/2-82-039, NTIS, Springfield, VA, June 1982.

CHAPTER TWO 11'

5

ton

SEWAGE MANAGEMENT, TREATMENT, CONVERSION, USE, AND DISPOSAL

A' ?641$frefr

4-e*

Spray or SurfaceApplication

Figure 2.5 SlowRate Land Application

Surface Application

Percolation throughUnsaturated Zona *".

Evaporatlo- 7.

"--

'

,).

RechargeMound

OriginalWater Table

AerationTreatment Zone

Infiltration

Figure 2.6 Rapid infiltration Land Application

Ev,aporation

2°8° Slope

Percolationinto Subsoil

Stuce .4. ..1141 ,1,11.0,1 VV./

ALI is' ,,,A. c, ...Amu 4Jillik,au

if11,14,

31101,1A'

Spray Appstvatlon

.Sheet FJow

41)110

07)00,0,

l .41,14. .if rAM ,)(' 440V

,,, w.c.f ..0 . ,/)/..4. 0,1111t, Wk..c 1,

4.8Run oilCollection.Ditch

Figure 2.7 Overland Flow Land Application

.4s

hA

t

Compacted SoilZone

Berm

4.,re 4.1111,=,

, _

A.

IVIP .All, 4.

..1100,,. .41,10 K .Aii.,

vea.. '1or

.

Ovortiow Perimeter -I Percolation 4

Effluent Distribution

Berm

, Overflow PerimeterPercolation

.CHAPTER rwol 912

ic

a s V -N,0'

SEWAGE MANAGEMENT, TREATMENT, CONVERSION, USE, AND DISPOSAL

4

ANADEPAINT AND USE OPSLUD01-111111,

With most sewage treatment systems, twopr:oducts result: liquid effluent and sludge.Suitably treated, effluent may bedischarged into surface Water bodies, in-jectrqd into the ground, or re-used for irri-gation or industrial proces'e water. In thesame way that appropriate technology canprovid1 alternatives to conventional sewage-treateent processes, it can also -offer alter-native option6 for the use of sludge.

'Sludge is composed of 3 to 10 percent or-ganic and inorganic solids; the rest is Water.In the United States, more than half of thesludge-pioduced is disposed of in landfillsor by land application (see Figure 2.9):

Methane is produced naturally from thebreakdown of sludge buried in landfills,and is resource can be recovered. Insteadof allowing the gas to rise to the surfaceand escape, wells are drilled into the land-fill, and the gas is collected and processedfor use or sale (flee Figtire 2.10). Vroperplanning and management of the landfillcan increase the amount of gas producedand recovered.

Much of the work curreto improve the handling, usof sludge involves improveintechniques, such as the reic

eing donedisposalexisting

y and useof heat from incineration. The appropriatetechnologies that are most ,commonty ap-plied in sludge management include landapplication, solar drying, and composting.

Land Application. Sludge, which canbe source of valuable soil nutrients': canbe applied to the land dried, as compost,or as a liquid. Properly treated, it is possi-ble to recycle the nutrients inherent insludge with minimal health risks.

Solar Sludge Drying. The natural heatof the sun is routinely used to dry sludge onsand beds throughout the country. Studiescontinue to explore the applications ofactive and passive solar sludge dryingtechniqugs. Experimentiwith passive solarsludge drying .at the Los Alamos NationalLaboratory have produced a method forestimating the performance of intor andoutdoor passive solar sludge dryinp. Testsindicate that passiire solar drying insidesunspaces is more effective in climates withhigh rainfall.

Composting is an effective way to .de-crease the pathogen density of sewagesludge and return the nutrients to the land.As of 1982, composting was classified as an

alternative sludge management system byEPA and became eligible for 85 percentFederal funding under the ConstructionGrants Program. Sludge composting iffnow practiced from the hot and humid cli-mate of Puerto Ric6 to the severe cold ofBangor, Woe.

Three sewage sludge composting meitodsare most common: windrow, static aeratedpile (see Figure 2.11), and within-vessel.All three methods provide "significant"and "further" levels of pathogen reduction,although the periodiC turnip windrowscan contaminate composted terial withunconiposted material. Windrow and staticaerated pile methods were developed inthe United States and Canada, and haveproven to be cost-effective, environment=ally acceptable options. The within-vesselmethod was developed in Europe a9d isused there successfully.

r

LAGOON ot OTHERSTORAGE. 11%

OCEANDUMPING, 10%

LANDAPPL1C241.

INCINERATION, 22

LANDFILL, 32

Figure 2.9 Sludge disposal Methods

Rohr. FM.

P7M.BNlf

Figure 2.10 Landfill Methane Recovery

IPMk,

=CAP

7 11.0001011111CKI,

Fan*..:.;r

CHAPTER TWO BEST COPY AVAILABLE' 13_10

7

ry

SEWAGE MANAGEMENT, TREATMENT, CONVERSION, USE, AND DISPOSAL

SYSTEM-WIDE MANAGEMENT STRATEGIES

Water shortages in some parts of thecdtintry, coupled with general concernabout the continuing- demand for water,have required a closer examination of wateruse and t&I, potential for conservation.

Studies indicate that conservation couldreduce water consumption by as much as40 percent. If overall water use were re-duced by even 10 percent, there would bean appreciable effect on water supply andwastewater treatment systems. For example,if a sewage system originally designed for12.5 MGD were redesigned for a 10 percentreduction in trifluent, annual costs wouldbe reduced by about 0.3 million per yearfor the life of theoplant. When less water isused, the water supply system pumps andtreats less water, uses less energy, andsaves money. Consequently, it also lakesless energy- to pump and treat wastewater(see Figure 2.12).

Although there are significant net energysavings as a result of water conservation,thdre can be incremental 'increases in.en-erg.y and chemical costs to treat sewagetlAt is more concentrated. Incieased odor

. can also be a problem in both collectionand treatment. systems. In practice, theproblems resulting from lower water levelshave been successfully rqolved with modi-fied operation and maintenance.

12000

10000

8000

6000sa

zSO

,

SO

4000z

2000

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egg ortrisEylitil:T PLANT

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PERCENT REDUCTION OF INDOOR WATER USEMOTE:Ammo; NAOMI beu'd WI 7%Interest Woo (tom tv toeTEE MOO New Hitt

CHAPTER TWO

Many of the problems associated withreduced sewage loads occur because con-servation plans are implemented after tew-age treatment plants have been designedand built for larger loads. If water conser-vation plans were established and accurateload estimates were developed prior toconstruction, then collection and treatmentsystems could be planned that would avoidthe problems and maximize the benefits.Lower construction costs for collector sys-iems and treatment plants, and lower energydemand and reduced costs for pumpinghave been realfzed in all parts of the coun-try as a result of guch efforts.

Decentralized Systems

The general perception is that nearly allof the United States is served by systemsthat collect sewage from broad areas andtransport it, by sewer collation systems, toa central treatment plant. While these cen-tralized systems clearly predominate, about30 percent of the United States populationuses decentralized disposal systems. Recentpopulation shifts from urban to suburbanand rural areas have placed an increasingnumber of people in areas where central-ized systems are- impossible, imprvtical,or unaffordable. On-site waste disposalsystems offer several alternatives.

Three types of on-site waste disposal sys-tems are most common: septic tanks, cess-pools, and privies. Several more advancedsystems are now available, such as compost-ing toilets, incinerating toilets, recirculatingtoilers, chemical toilets, aerobic systems,vacuum systems, And evapotranspiration.

Recently there has been increasing inter-est in using on-site disposal methods moresystematically. Case . indicate thaton -sits disposal syste s, developed on acommunity basis, ben t greatly from theestablishment of their o n waste manage-ment organization:

Community waste 4 age ent organiza-tions, set up by munici es, developers,or homeowners, provi e several benefits.They can have preliminary studies per-formed, establish construction and operationstandards, monitor construction, providepersonnel to monitor operations, and pro-vide,maintenance and service. The greatestbenefit is that they can provide the advan-tages of a well-ruri decentralized system,without requiring the individual propertyowner to become a -sanitation engineer.

rw

SEWAGE MANAGEMENT, TREATMENT, CONVERSION, USE, AND DISPOSAL

Such systems can also hXe lower capitalcosts and provide more ,jobs than large,central systems.

As with any new undertaking, there aredrawbacks to decentralization that must beconsidered. To form and operate a detralized waste treatment organizationquires more involvement by the individualthan it does to hook into an existing centralsystem. In addition, -site characteristics orstate and local regulations in some areasmay prohibit the use of certain systems.While these problems are not insurmount-able, they must be realistically evaluated.

On-site evapotranspirationsystems normally consist ofa bed of gravel, sand, andsoil containing a distributionpiping system, underlaid by

' an impermeable liner (seeFigure 2.13). Wastewater Ispretreated by grease trapsand either a septic tank oran aerobic treatment system.The surface of outdoor evap-otranspiration beds is slopedto drain off rain water and isplanted with vegetation. Theliner prevents the waste-

, water from draining Into thesoil, and water is raised tothe upper portion of the bedby capillary action in thesand where it evaporates in-to the air. Also, vegetationtransports water from theroot zone to the leaves (andstems of some plants), whereit is transpired.

Climatic conditions arethe most significant con-

straint to the use of evapo-transpiration systems. Yecir-round, non-discharginVout-door systems are practicalonly in arid and semi-aridportions of the western andsouthwestern United States.Indoor evapotranspirationsystems under transparentcovers and in greenhouseshave been proposed to ex-tend

t.

their use to other re-gions. Covered beds can besmaller because -the beddoes not have to evaporateor transpire the-added waterof rainfall.

Evapotranspiration systemsin attached solar greenhousesca"h be used to process do-mastic greywater. In addi-tion, non-food plants grownusing the wastewater nutri-ents have the gbility to ab-sorb air impurities throyghtheir leaves while absorbingwater pollutant; through

Composting Prnmsses toStabilize and Disinfect Mu-nicipal Sewage Sludge,EPA-430/9.81-011, U.S. Envi-ronmental Protection Agency,Washington, DC, July 1981.

Diriges, R., Natural Sys-tems for Water PollutionControl, Van Nostrand Rein-hold Company, New York,NY, 1982. ,

The 1910 Needs Slarvey,Conveyance, Treatment,aniControl of Municipal'Wastewater, CombinedSewer Overflows, andStarr/water Runoff, Sum-maries of 'technical Date,-EPA-430/9-81-008., Washing,ton, DC, February 1981.

)'Hedstrom, J.C. and Dicker,J.S., Solar Drying of Sew-age Sludge, LA-9317-MS,Los Alamos National Labora-tory, Los-Alamos, NM, MO1982.

innovative and Alterna-tive' Technology Assess-ment Manual,. EPA - 430/9-78 -009, NTIS, Springfield, VA,February 1980.

K yosako, J.S., Effects ofter Conservation In-

duced Wastewater FlowReduction: A Perspective,EpA-600/2-80-137, NTIS,Springfield, VA, August 1980.

.Operation and Mainte-nance Considerations forLand Treatment Systems,EPA-600/2-82-039, NTIS,Springfield, VA, January1982.

Van Note, R.H., et al., AGuide to the Selection ofCost-Effective WastewaterTreatment Systems, EPA-

. 430/9-75-002, NTIS, Spring-field, VA, July 1975.

Wilkey, M.L., et al., 'Meth-ane from Landfills: Prelim-inary Assessment Work-book, ANL/CNSV-31, NTIS,Springfield, VA, June 1982.

Wolverton, B.C. and McDon-ald, R.C., Foliage Plantsfor Removing Formalde-hyde From ContaminatedAir Inside Energy-EfficientHomes and 'future spec*Stations, NASA, TM-84674,NASA, NSTL Station, MS, De-cember 1982.

their roots. Therefore, afully - integrated greenhouseand evapotranspiration sys-tem can treat anddispose ofdomestic wastewater, re-

' move indoor air Pollutants,

such as formaldehyde, andprovide .,space heating forthe attached building.

1T-11

.

Evaporation

Effluent from C - Valve

Anaerobic TankSandyLoam

Septic or .

...,.

r. Transpirationfrom VegetatiOn

Columns offine, Washed Sand

Filter Cloth orAsphalt Paper

Perforated

Gravel

;1,01 pipt#10us Lining

100,; Top

CHAPTER TWO 12

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b.-

CASE STUDIES: APPROPRIATE TECHNOLOGY AT WORK

More than a dozen cities4, towns, andindividuals, across the country were able todevelop appropriate technology solutionsto municipal sewagOiroblems with grantsfrom the U.S. Department of Energy Appro-priate Technology Small Grants Program.

The projects examined in this chapterwere selected as examples of the range oftechnologies employed and the range offproject sizes. These grantee managedexisting systems more effective) , modifiedexisting system to reclaim the energy frommethane and effluent.that had been wasted,and tested the effectiveness of new pro-cesses for sewage treatment.

These projectewere also chosen becauSe*they were associated with established sew-age treatment plants, with capacities thatrange froltt moderate to the largest in theworld. This 'makes the lessons learned more

useful to managers of other similar treatment,systems. finally, these projects were -se-lected because they have had enough timeto prove themselves. The case studies in thischapter have-been prepared fr9m projectfinal reports (available from the NationalCenter for Appropriate Technology), andfollow-up contacts with the grantees.

Experimental science rarely yields over-night successes. All of the case studiesreviewed here have achieved substantialresults, but there are other projects spon-sored by the,Appropriate Technology SmallGrants Prolgrefn that also contributed,to theknowledge of sewage treatment throughtheir work (see Appendix A). While most ofthe projects deal directly with municipalsewage treatment; some deal with othertechnologies, such as on-site treatment sys-tems, that can affect municipal systems.

GLOSSARY

Activated Sludge Proses,:A biological wastewatertreatment process in which amixture of wastewater andactivated sludge is agitatedand aerated. The activatedsludge is subsequently sepa-rated from the treated wove-

.water by sedimentation anddisposed of or returned tothe process as needed.Aeration Basin:A basin where oxygen issupplied by mechanical agi-tation or pneumatic meansto enhance the breakdownof wastes held in suspension.Bar Screen:A screen made .of parallelbars from about three-quarters of an inch to twoinches apart, used to filterout large objects.Cascade Aeration:Aeration of the effluentstream through the action offalling water.cfni:Cubic feet per minute.Clarifier:A tank used to remove set-tleable solids by gravity, orcolloidal solids by coagula-tion, sometimes followingchemieal flocculation; willalso remove floating oit andscum through skiniming.

COD:Chemical oxygen dembnd. Ameasure of the oxygen equiv-alent of that portion of or-ganic matter that is suscepti-ble to oxidation by a strongchemical oxidizing agent.Co liform Bacteria:A bacteria whose presenceIn wastewaterlis an indicatorof pollution and of potentiallydangerous contamination.DC:Direct current.Deeeration:Removal of gases from aliquid.Flow Rate:The amount of water thatmoves through on area (usu-ally pipe) over a set periodof time.Francis Tyrbine:A water-powered turbineused fo transform water fall-ing vertically to mechanical(rotating) energy.

gallons per day.Herd:The vertical distance waterdrops from the highest levelto the level of the receivingbody of water.Header:A pip* from which two ormore tributary pipes run.hp:Horsepower.HYdiaulic Load:Amount of liquid going. Intothe system.

lichoff Treatment System:A tank without aeration oroxygenation where solidssettle out of the wastewaterand may be digested in aseparate compartment inthe bottom.Induction Generator:A variabletspeed multi-poleelectric generator which issimple, rugged, reliable, andrelatively inexpensive.InflowsWater (and pollutants) thatenter sewage systemsthrough street inlets, roofdrains, and similar sources.kW:Kilowatt.kWh:Kilowatt-hour.Mesophilic:An optimum temperature of25-10°C, for bacterial growthin an enctosed dlaester.MOD:Million gallons pet day.mg/I:Milligrams per liter.mad:Thousand standard cubic foot.

Mid:Million standard cubic feet.NTU:Nephilometric turbidity unit.A measurement .unit of the.clarity of water, dependenton the amount of suspendedmatter.

PCB's:Polychlorinated biphenyls,group of organic compounds.PCB's are highly toxic toaquatic life; they persist inthe environment for long pe-riods of time, and they arebiologically accumulative.pH:A measure of the acidity oralkalinity of a substance (7.0is neutral).Post-Aeration:The introduction of oxygeninto wastewater after sec-

"ondary or advanced treat-ment to further reduce BODand CQD.

Pilot icale:The size of a system betweenthe small ,laboratory modelsize and a full size system.

Pounds per square inch gagepressure.

Therm:A unit of heat equal to100,000 British thermal units.

CHAPTER THREEr ",

16 13.

40-

ENERGY AUDIT AND CONSERVATION PLANWalterboro, South Carolina Wastewater Treatment Plant

As part of 10 overall effort to controlmunicipal costs; the City of Walterboroused a $6,500 grant to evaluate the opera-tion of the Wastewater Treatment Plant andto identify ways to reduce electrical con-sumption. The studyhad two primary goals:compare ,how the plant was designed withhow it was actually operating, and thenfind out what could be done to cut electric-ity use and costs. All treatment units at the.plant were considered:

Bar ScreenGrit RemovalInfluent PumpingAeration BasinClarifier and Sludge 'RecirculationPost-Aeration

It should be noted that prior to this study,energy use at the plant had been reducedby a sizeable 30 percent through the modi-fication of existing operating procedures.Lighting and heating loads were not con-sidered in this energy study; because theywere known to be relatively small and wellmanaged.

Treated Chlorine ContactEffluent S Aeration Basin _Drain

Laboratory -`

leer Screen X,Grit Remover

t

Circulation PumpChlorine

Building

Drain- Pump Sul !ding r Line

Pint CieliflorEffluent lox

DrainLine

SludgeDryingBed.

\)r SewageInterceptorLin

F' , .4/?wat r T c plant

Aeretioibasin

FlowMeteringSox

Technological !recesses and Operation

In 1972, the Walterboro treatment plantwas upgraded. However, because of lowenergy costs at that time, energy efficiencywas not a design consideration, and theupgrade included oversized unite that en-ergy auditors found to be unnecessary foreffective and efficient plant operation.

fl

The audit found that organic levels at theplant were lower than expected and thewater volume was higher than expected.Organic loading was lower because pre-treatment (of slaughterhouse "wastes) haddecreased the volume of organics, andinflow anct infiltration into the collectionsystem were dilutirig the or/anic load andincreasing the hydraulic load. Plant 'flowrates averaged between 1.25 MGD and2.5 MGD, but during rainy periods dailyflows peaked as high as 6.0 MGD. Theaverage flow of sewage into The system wasonly .65 MGD; the rest was water frominflow and infiltration. Consequently, sew-age at the plant was fairly weak, averaging110. mg/1 BOD5 and 110 mg/1 for SS. Asewer rehabilitation program is expectedto reduce inflow during rainy periods, butthe average flow rate is expected to con-tinue in the 1.25 MGD to 2.0 MGD range.

Screening and Grit Removal. The studydetermined that, operating the bar screenon a timer for 12 to 14 hours per day, ratherthan around-the-clock, could result in a40 percent energy savings for this part ofthe, process. -This change would have a,.high return on investment, but the overallimpact would be fairly minor, becausescreening and grit removal accounted foronly 4.6 percent of total. electrical demandfor the plant. It is also possible that timedoperation could Increase grit compactionin the housing for the bar screen lowerbearings: Therefore, this measure wasgiven a low priority.

Influent Pumping. The influent pump-ing-station at the plant has two 100-hp mainpumps and a ,15-hp back-up pump. Bydesign, only one main pump could operateat a time, and it usually operated at only 15to 40 ;percent capacity. (The pump occa-sionally operated at full capacity duringperiods of extraordinary inflow.) So muchexcess capacity made the influent pumpsthe most inefficient plant operation. Tiestudy found that three modifications in thepumps would be..effective: 1) to install anew, 30-hp pump that would, be turned onmanually to handle normal flows; 2) rebuildand reduce the capatity of one main pumpto 50 hp for normal flows and some peakflows, and 3) reduce the capacity of theother mainpump to 75 hp for peak flows. Itwas estimated that implementation of thesemodifications would reduce consumption kirinfluent pumping by 43,000 kWh per year.

Aeration Basin. The volume of the aer-ation basin isItl .85 million gallons. It was,

CHAPTER THREE1 7

14

ri

.4

.

found to be organically undeladed, andeither of the two 100-hp, low-speed aeratorscould maintain satisfactory oxygen level'sand solids suspension. If the normal organicloading rate wefe doubled, it was estimatedthat 120 hp would be required to maintainrequired oXygen levels. The study indicatedthat the most effective way to do this would .

be to replace one of the 100-hp aeratorswith up to three' 20-hp, floating aerators.This.step would result in a 40 kVA demandreduction. Even with no changes in theaerator configuration, as much ag. 36,000,kWh per year could be saved by purchasinga dissolved oxygen meter, monitoring oxy-,gen levels in the basin, and operating theaerators to meet specific oxygen demand.Some savings have already resulted fromchanging the schedules for operating thefixed aerators.

Clarifier. Before the study, a tricklingfilter was converted to a 7-foot deep clari-fier, about half the depth of normal clari-fiers. This clarifier unit and the sludgerecirculation pumps use more energy andeeper clarifiers, and accounted for about15 percent of the plant power requirements.Both the clarifier sweep and the recircula-tion pumps ran most of the time. It wasdetermined that these could be run left ifsolids from the aeration basin were reducedand the recirculation rate for the pumpswere lowered. Also, pump performance

could be incr/ased by changing pump pul-leys; one pump should handle low-flowoperations. Modification of the inlet struc-ture to reduce flow restriction has reducedthe energy needed for pumping.

Post-Aorationt. Cjilorination is followedby mechanical ppst=aeration in a convertedclarifier tank, Effluent from the tank is dis-charged to a canal with -a drop of 20 feet,which was estimated to be suffidient to pro-vide post-aeration to meet permit standards.Replacing the mechanical aerator with thiscascade aeration would totally eliminate'the power demand for post-aeration.

Energy and Economics

At the time of the audit, energy con-sumption at the Walterboro Plant averaged71,300 kWh per month. If all of the effi-ciency changes proposed by the energyaudit were made, electric consumption,would be reduced an .average of 11,468kWh per month, a reduction of 16 percent.The potential for energy savings for individual components range from 7.5 percent(operating the aeration basin based onmeasured oxygen levels) to.100 percent, Owcascade aeration replacedThe post-aeration .

tank (see Table 3.1). These changes wouldalso offer a range of cost savings and pap-back periods.

4.

Energy Savings Cost Savings PaybackProposed Alteration (Percent) ($ /Year) (Years)

Ser ScreenOperate Bar Screen on Timer 40.0% $ 37 1.4

Influent PumpingModify influent Pump & AddPump 22.0% $2,200 11.4 I

Aeration BasinOption 1Replace One Fixed Aeratorwith .Three Floating Aeratorsor Option 2

12.5% $3,840 . 5.9

Monitor Oxygen Levels inAeration Basin 7.5% $1,836 .8

ClarifierReduce Solids to Clarifierand-Run Ono Purilp 12,0% $ 744 3

Post-XerationOption IOperate PostAerator onTimeror Option 2

62.0% $.612 4.9

Replace with CascadeAeration 100.0% $ 984 15.2

TABLE 3.1: PREO/CTED iNFPGY SAVINGS AND COST QFOUCTiONS

-CHAPTIIIR maw 1577-

ti . .

HighlIghtsnontl Current Stattii _AMOperators at the Walterboro Wastewater

Treattnitnt Plant' have learned how tostakecontrol of energy consumption. They nowundeistand the plant in terms of energyperformance and thb relationship betweenhow things were designed and how theyactually work. Changes in operating pro-cedures (mostly by using timers) put intoeffect before and as a result of the audithave 1004 achieved significant savings.As he city budget. will allow, Walterborooperators can implement further cost saving .steps that require larger capital investments.

This case illustrates what lo expect fromenergy conservation programs at sewagetreatment facilities. The savings overall arein the 15 percent Lange. That may not seemlike much, but sewage treatment is a fixedcost for all communities in tile United States.Residents pay year after year, and risingenergy costs are increasing the burden onmunicipal budgets. Shaving 15 percentfrom the cost of a perennial community ser-vice is an iniportant contribution, especiallyon top of the 30 percent savings Walterborohad achieved before the study.

WHO TO CONTACT:

Mr. Tom Hyorrick, Director of Public WorksCity of WalterboroP.O. Box 717Walterboro, S.C. 29488Telephone (803) 549-2545Final Report: NCAT ID #SC-81-006DOE Contract No.: DE-FG44-81R410422

S

CHAPTER THREE

Several recent publicationsare available that providedetailed suggestions and

Identification/Correctionof Typical Design Deficien-des of MuNcipal Waste-water Treatment Facilities,CERI, EPA, Cincinnati, OH,October 1982.

ZIcivo), R.L., et al., "NowBubble Diffusers ReduceTreatment Cosa" Publit

,Works, Vol. 113, No. 0, June1982.

Martel, C.J., et al., Evaluat-ing-the Heat Pump Alter-natives for Heating In-closed Wastewater Treat-ment Facilities in ColdRegions, CRREL,SR-82-10,NTIS, Springfield, VA, May1982.

Energy Management Diag-nostics, EPA-430/9-82-002,NTIS, Springfield, VA, Feb-ruary 1982.

Water Pollution Control Fed-/oration, Energy Conserva-

tion In the Design,and Op-oration of WastewaterTreatment Facilities, Man-ual of Practice M.O.P. FD2,WPCF, Washington, DC, Feb-ruary 1982.

methods for conserving on-(orgy at wastewater treat-ment plants:

Dean, R.B., and Lund, E.,

Water Reuses Pcoblemsand Solutions, AcademicPress, London, England, 1991.

Energy Conservation inMunikipgi Water andWasteWater TreatmentSystems, Arizona EnergyOffice, Phoenix, AZ, Decem-ber 1981.

Proceedings of the U.S.Department of Energy:En-ergy Optimization of Wp-tfilr and Wastewater Man-agement for Munldpal andindustrial ApplicationsConference, Volumes 1 and2, Argonne National Lab.,Argonne, IL, December 1979.

Hyman, A.M., "'Reducing En-ergy Charges at a TreatmentPlant," Public-Works, Vol-ume J10No. 1, January1979.

Field Manual for Perfor-mance Evaluation _ andTrouble-Shooting at Mu-nicipal Wastewater Treat-ment Facilities, EPA 430/9-78.001, EPA, Columbus,OH, January 1978.

WHERE TO FIND MORE INFORMATION

ti

16

DIGESTER GAS RECOVERY AND USEMetr-opolitein Sanitary District of Chicago, Illinois

The West-Southwest Sewage TreatmentWorks, just west of Chicago, is the world'slargest. In an average day, it treats about800 million gallons of sewage. Sludge treat-ment generates approximately 2.7 Mscf ofgas per day. Before this project was -initi-ated in March 1980, 1.7 Mscf oLgas wagburned to maintain mesophilic operatingtemperatures in the digesters-1.0 Mscfwas flared off as waste gas. Sanitary Districtpersonnel'designed and implemented asystem to make better use of the gas pro-duced by sludge;digestion with a $50,000grant from`the Department of LEnergy and a$780,000 investment o'f its n.

Modesto, California hasbeen waling seven city ve-hicles on methane from Itswastewater treatment plantsince 1978. The pilot projecthas been so successful thatcity managers have planneda full-scale operation for1983 that wilt serve about200 vehicles.

One key to the Modestsuccess has been the clean-ing process that yields gasthat is 98 percent methane.City vehicles were convertedto use either gasoline or

methane at a cost of /About$1,200 per viihiclo.

Methane from the pilotproject was estimated tocost about 35 cents for theequivalent of a gallon ofgasoline. The vehichs.s haveperformed well using themethane, which burns clean-

an gasoline and seemsto cause less engine wear.Only police had any com-plaints; they felt methanedidn't 'fuel their cars withquit. as much "punch" asgasoline.

SEWAGE GAS POWERS CARS & TRUCKS

Technological Processes and Operation

The West - Southwest Works uses the acti-vated sludge- process and incorporates twoseparate sluplge digestion systems: an Imhofftreatment systeM and a heated anaerobicdigestion system. Only the heated ainaero-bic digestion system is included in the gasgathcrifig process. There are currently 12high-rate digestion units, each with a 2.5million gallon capacity, operating at theplant. [Six additional digesters are pro-posed, each with a 3.0 million gallon capac-ity (see Figure 3.2).]

After an engineering study was com-pleted, a gas-collector-and-boiler systemwas constructed. In the new system, gas iscollected from The digesters, compressed,cooleciold dried, and then piped about1,800 Met tt, the .storpge accumulator andthe boilers (see Ffure 3.3). The range of9eis flow frOm the digester tanks is from

CHAPTIR THREW.

TwelveExistingDigesters --

Sludge ControlBuilding ----

Wash, GesControl Building -

SludgeConcentration

- Tanks

">)fix Future

t_k; Digesters

000000000000Q00.

1=1.°:100000000Final

AerationTanks

Existing LinosUsed:

Boller FeedNaturil GasLowPress.

Steam

DigesterGas Like toPower House

FutOre SteamLino Mr SludgeHeating

r.

00 0 000 111Pow's0000000000000000Pump IBlowerHouse

FinalSettlingTanks

F Tuft' 3 ? West Southwest Sewage Treatment Works

Affercool.. -- Separators

tiaa Header from Variable SpeedDtp.fers Confront,

O.C. Meter

Noe Not ". Comptes Kw0 Pre.wtranarnilter

Variable SpeedController Compreaoor

D.C. 1121:2:,

r spore 3 3 Weft Southwest Sewage Treatment Works

250 cfm to 700 m, on a daily basis. Tohandle this range and the 'future expansion,compressors with a range of 2SPto .1,400 chi*were selected. The gas is notalied; it isfed to the boilersjust as it is generated fromthe digesters. However, the gas compressoraftercoolers do r ove a considerable

. quantity of moisture rom the digester gas.To maintain relativ ly constant gas flows 40

and optimum digester operation, gas pres-sure transmitters are stalled in the gasheaders. These trananiitters send a signalto change the speed of the DC, variable -speed motors at the compressors.

Alter compression, the Oas is cooled andmoisture separated off. Gari is carried to theboilers by a 12-inch pipe, \uitably coatedand protected to transport gas.The pipe was oversized toaccommodate ananticipated 50 percent increaie in digestercapacity.

Initial studtbs of how to usedigester gas considered gas tut gener-

.

, 17

n.

ators, 'internal combustion engines, andwater tube boilers. Boilers were selectedfor three reasons:

1) comparatively low capital cost andquick return on3nvestment,

2) consistent plant demand and uses forlow-pressure steam,

3) and low-pressure boilers would comeon-line when existing high-pressuresteam generators were being retired.

The new boilers are located in a buildingthat had housed a sludge processing sys-tem. The boilers were sized to meet boththe projected gas production levels and theplant steam requirements.. Two boilers werepurchased rather than one so that a back-upboiler would be 'available if needed. Theextra boiler will be used when more gas isproduced in the future.

The system is fully monitored and con-trolled to assure the safety of the operation.Faults in system operation cause the com-pressors to shut down automatically.

Energy and Economics

A significant amount of the natural gasrequirements for deaerating boiler feedwater, and plant heating and cooling arenow met by using digester gas. As a result,the use of digester gas at the plant displatcesenough natural gas to heat approximately3,300 private homes, each burning 1,100therms of .gas every year.

When the first four digesters at theWest-Southwest Works went into service in 1964,only enough gas was recovered to heat thedigesters; the rest was flared off by wastegas burners. ri,y 1978, when the gas recov-ery project was proposed, plant operationsand the cost of energy had changed con-siderably. Flared gas at the West-SouthwestWorks' represented 6,500 therms of energy

l

lost every day. In 1978, the price of r/aturalgad was10.24 per therm, and the v ue of,the gas -the project proposed to save was$1,560 per day, or nearly $568,000 peryear. By ,1982, the cost of natural gas pur-chased by the Works had risen by,$0.10per therm, and the value of the digestergas had increased accordingly. Also, thevolume of *ester gas available for use intide boilers has increased to 10,000 thermsper day because of an improved 9perating*'mode developed for the 12 digeiters.

The total cost of thaprojecl was $830,000with a payback on investment of less thentwo years. Operation and maintenance

costs for the system are estimated to be$150,000 per year Maintena 'hce has beenroutine, and the bulk of the cost has beenin wages for the boiler operators.

The West-Southwest Treatment Worksproject incorporated several elementswhich contributed to its cost-effectiveness.

I) Analysis,'design, and construction ofthe project was carried out by SanitaryDistrict employees.

2) The project was phased into long-rangeplanning. Design tynd equipment deci-sions were made to allow for increasedgas production and steam demand,and boilers were selected to replaceothers designated for retirement.

3) Equipment was selected that satisfiedspecific needs and was cost-effective.The boilers cost at least $1.5 millionless than gas turbines.

Highlights and Current Status

Operation of the gai; gathering and sham'productt6n system at the West-SouthwestWorks has been so successful that the Sani-tary District has implethented a similarproject at the District's Johp Egan Plant.Other municip91 systems that uAe anaerobic >

i sludge digestion arid produce excess diges-ter gas could benefit from the implemtnta:Hon of a gas recovery anduse system. If the

g t conditions exist, plant managers can1.1

mea re the amount of gas produced, deter-..,mine its 4anergy and economic values, andconduct a feasibility study to determinewhich options will yieldthe greatest benefits.

,

I

, CHAPTER THREE Is

4'

4.t

tr

a

(

Metropolitan Sanitary District of Chicago, Illinois

The amount of energy in the form of methane gas availablefrom residential sewage can be estimated by using the followingformula, if the number of people served is known.

pooplo 650 Stu'sStu's per dew

day porsoh .Examples 1) If Our sewage treatment plant story*,

100.000 poop,* poi day, them 3r100,000 people 650 Stu's

X = 65,000,000 Stu's per dayday poison

One pound of volatile solids yields about 12 ft' of methane. Soif the amount of volatile solids is known (typically /5 percent oftotal solids) methane production can be estimated. "Typical"wastewatqUas 230 mg/I of solids or 1,921 pound] /milliongallons. Seventy-five percent of 1,921 Is 1,440 pounds of volatilesolids per million gallons. (An analysis of sewage at the plantwill give a more realistic number for the average pounds ofvolatile solids per million gallons.)

Use the following formulas to estipfte the energy voluthe methane production potential:

(pounds of volatile Solids per day) 'X 12 ft' /lbft' methane per day

Example: 2)(1,440 lb of volatile solids per day) X.12 /lb =

There are about 650 Bb's /ft' of diges/ter gas, so .(650 Btu per ft' X 17,280 ft' per d y) 11,232,000Iitu's per day

Co9eneratiar4is an additio a option. The conversion of meth-ane fo electricity is us ally only 30 percent efficient, so if thedigester gas is burnecf\in n nternal combustion engine, theelectricitfavailoble son ca culated 'hi 'follows:Example: 3) 11,232,Q00 0 s gar gay

X (.30) =1,414 kWh poi Stu

1117 kWh per day'rom the ongine an usu Ily.be reclaimed at 34 to 65 per-

cent of ciency, and this heat c n.be used to heat digesters orsupply her demands for hut. 4

Bode, Dave, "Cutting CostsWith Digester Gas," Diostoland Gas Turbine Progress,Fel1ruary 1980.

,The Energy Exchange Prol-oct, Volumes 1 and 2, DOE/CS/20468, NTIS, Springfield,VA, April 1982.

REFERENCES

Stanfford, D.A., et al'; Moth-an* Production from Or-ganic ,Matter, CRC Press,Inc., Boca Raton, FL, 1980.

System Analysis for Do-volopinont of Small So-source, Rocovory Systems,DOE/CS/20026-01, Vol. 4,NTIS, Springfield, VA, Octo-ber 1980.

17,200 ft' per day

ESTIMAT'NG METHANE PROOUCTiON

I

a

e

4

CHAPTER (411

41

PRODUCING ELECTRICITY FROM EFFLUENT OUTFALLNorth Andover, Massachusetts Treatment Plant

a

Until about 1870, water was the principalsource of power for American industry. Alarge number of the early water "mills"were located in the Merrimack River Val-ley, the center of the early textile industryin the United States. A feasibility study,funded with a $9,324'grant, indicated thatthe Greater Lawrence Sanitary District inthe Merrimack Valley can continue this.tra-dition using a water turbine-generator toreclaim energy from the effluent waterwhidh is discharged from the plant to theriver about 40 feet below.

In the 1840's, James 8.Francis, working In the Mer-rimack River Valley, inventedthe highly efficient FrancisHydro Turbine. Modern vol.-sions of this turbine are Ria,duced to exacting specifia-tions and usually requirefrom 6 months tos2 'years toproduce aod 'deliver.

Another hydrokactric op-tion is available 'or lessmoney that works with lower

hoods (vertical distance thewater falls) and flow rates.Mass-produced pump/gen-erator sots use the punfpoperating in revers. as aturbine coupled with a gen-orator or alternator to pro-duce electricity. They aregenerally only 65 to 85 par-cant efficient, but they costless initially, are more read-ily available, and can be de-livered relatively quickly.

Technological Processes and Opgrationill4.

As designed, an average 28 MGD of efflu-ent water from the plant will flow down into avortex chamber where a gated Francis tur-bine is Moupted vertically. A shaft connectsthe turbine (via gears) td a horizontally-mounted, 200-kW induction generator. The3 -phase power will be fed into the plant's

wer grid at the 'plant water pump station.PpkAfter driving the turbine, the water will

flow through a 72-inch outfall pipe and willbe diffused through multiple openings intothe river. An emergency overflow chambercan divert any excess water to a 60-inchstorm drain and then into the river (see Fig-ure 3.4).

Energy and Etononalai

The Greater Lawrence Sanitary District.pays $0.068 per kWh for electricity. In thefirst year of operation the hydroelectric sys-tem is expected to generate 1 million k*h.By 1995, it is estimated that 2 million kWhper year will be generated. With constantgrowth in the plant loading rate, a total ofabout 19 million kWh of electricity will beproduced by 1996.

EmergencyOverflowChamber

200 KWGenerator

VortexwAChamber

Turbine

1Ent Pipe

Existing 69 in. dia. /Storm Drain

Existing 72 In. dia. /iMerrimack Outfal!tPiptt /z

Stono.lined ..att4Channel

River ,,

iff --. ------.7,--"- b---.

------..:__' OuttenDiffuser...,__

North Andover, Massachusetts Treatment Plant

It is estimated that the hydroelectric sys-tem will have an 8-year paybdck, assuming a7 percent interest-rate for borrowed money.Nearly $290,WO for project constructioncanie from the Mgssachusetts Energy Office.Another $285,000 came from the GreaterLawrence Sanitary District.

HydroeQtric systems mord than 80 years/obi are still producing power today, andthe North Andover system could easilyoperate for 40 years. No operational data isavailable yet, but water, power systemp tra-ditionally have low operation and mainte-nance costs. It is assumed that maintenanceand operation wilt cost about $5,000 peryear. The system will not require a full-timeoperator.

HIghliehts and Current Status -1111The Greater Lawrence Sanitary District

has irfvested in an 'environmentally soundenergy recovery system. The system isscheduled to become operational in April1983. Instead of wasting energy and spend-ing money, the hydroelectric system willuse an existing situation to produce energyand save money.

WHO TO CONTACT1

Mr. Eric TeittimenGreater Lawrence Sanitary DistrictNorth Andover, MA 01845Telephone (617) 685-1612Final Report: NCAT ID # MA-80-015DOE Contract No.: DE-FG41-80R110409

In sillany plants, after thewastewater is treated It Is

discharged Into a stream,fiver, lake, or the ocean. Ifthe discharge Water falls 8feet or mom It may containenough energy for practicalhydroelectric production.

Many different turbine-generators are available,and the amount of electricitythey can generate dependson three primary factors:

1) the flow rats in milliongallons per day,

2) the vertical distancethe water falls (hood)In foot,

3) and the IsfficiencY ofthe turbine-generator.

Discharge flow rates aremeasured routinely at mostwastewater treatment plants.The distance the water fallsIs also easily ,clotorminskkThe efficiencies of turbine-generators, which rang.from 75 to 93 percent, andspecific efficiency informa-

tion can be obtained frommanufacturirs or found Inhydroelectric literature.Variations In flow must alsobe tOken Into account whenestimating turbine efficien-cies. If variations are ex-triune, a flow equalizationstrategy may be required.

To estimate the amount ofelectrical energy per daythat can be reclaimed fromsewage effluent outfall, usethe following formula:

(3.1426) x (MOD) X(Fall In Poet) XEffIclancy = kWh per

dayEXAMPLE: 3.1426 X 30MOD X 40 ft X.5 = 3.017 kWh/day

Plants that seem to havethe potential for prodycingenergy with hydrotfoctricgeneration should also In-vestigate the option of sav-ing energy with cascadeaeration.

Chappell, J.R., t al.,Pumps -As- Turbines Expo,dance Prank', IDO-10109,NTIS, Spririfield, VA, Sep -tember 0 982.

Hydropower EquipmentManufacturers and Third-wore Suppliers, NCAT,Butte, MT, January 1983.

Small Hydropower Engl.nanrIng Dtvalopmants,8208-6/81-1M, Departmentof Energy! Idaho Falls, ID,1981.

rs

REFERENCES

A

CHAPTER THREE 21

AN ANAERO3IC PRIMARY TREATMENT SYSTEMSolar Aquasystenns, Inc.; at the Sqn El ilo Water Pollution Control Facility,CardHf-by-the Sea, California

With an $8,000 grant, Solar Rquasys-toms, Inc. designed and built-a prototypeAnaerobic Aqua Cell system. The systemwas" tested from November .1978 to August1979. While in operation, it demonstrateda two-cell primary treatment system fordomestic wastewater that combined anupflow solids digestion process with afixed-film anaerobic process.

Technological Process** and Operation

A prototype stem, designed toapproximate the rface-to-volume °ratiosof a full-scale stem, was 'constructed atthe San Elij WaterawPollution ControlFacility, which serves Cardiff-by-the-Seaand Solana Beach,, Cal4fornia, .The pilotplant was housed,in a greenhouse structurethat provided passive solar heating: Afteran initial loading with sludge from thecounty's anaerobic digester, raw sewagethat had been ground and screened wastreated by the 3,000 gal/d pilot plant.

Treatment took place in two cells. Bothcells had floating black synthetic rubber

FloatingCover

Cell One

covers for digester gas collection, heatretention, and odor control. Sedimentationand sludge digestion occurred in the firstcell- which used upflow percolation (seeFigure 3.5). At this stage, bacteria at-tached themselves to sludge particles andbroke down organic compounds intosmaller molecules.-These blicteria are rela-tively resistant to toxins and environmentalfluctuations, and they respond relativelyquickly to variable loading rate8.

After 6 hours of water treatment in thefirst cell, the effluent 'entered the-secondcell. Methane-producing bacteria in thesecond cell attached themselves to an array"of hanging plastic sheets and webbing witha verwhigh surface area. These provided astable attachment area, accelerated thefejnoval' of suspended solids, and per-mitted coagulated solids to drop to the bot-tom where they were further reduced andstabilized. The bacteria produced methanegas and carbon dioxide while reducingBOD, levels and some SS. The water treat-ment time in Cell Two was 8 hours.

Methane-producing bjtcteria are vulner-able- to drastic influen1 ,sflanges. theAquaCell process, the fir& cell'acted as abuffer for the second, reducing toxins andmoderating the wastewater temperature.

One of the primary disadvantages ofconventional, high-rate, anaerobic systemsis that temperatures must be kept high(35°C) for effective digestion. The Aqua-

Cell Two Gus Vent'

FloatingCover

Raw SewageInfluent

Upflow Percolation,Through Sludge

pelfCleaningBioFlini'Substrates for-MothanogenicIta (aria

CHAPTER THREE

2522

a

Cell operated from 18°C to 31°C with noapparent effect. on removal efficiencyrelated to terrerature.

Project operators estimated that thesolids content of sludge was reduted by ap-proximately 85 percent during a 6-monthperiod. Eighty-five percent is 4 signifi-cantly higher solids reduction rate than forconventional systems (see Table 3.2). Thesludge produced during those 6 monthswas removed and dried on sand beds inonly one week.

Over a 10-month test period, the Anaero-bic AquaCell removed an average of 50percent of BOD3, and 88 percent of SS,with a 6-hour rAtention time in the first celland 8 hours in the second cell. Colifortnwas reduced on an average of 96 percInt(see Table 3.3).

t-

_

Energy and economics. ,

The primary treatment process its re-quires no energy. Energy is neces.. A \forscreening and grit removal and intermittentsludge pumping. However, because sludgecontinues to break down while ft is retainedin the cells, there is less sludge remainingto be pumped out. Because only intermit-tent pumping is necessary, less energy tsused. In addition, the AquaCell system isan alternative Ao primary clarifiers andconventional anaerobiC digesters, both ofwhich require significant amounts ofenergy to operate.

Because there were -problems with theseals on the floating covers of Cells Oneand Two, methane was not collected and

TYPE OP PROCESSTREATMENT LEVEL

Primary Secondary

SEPARATE FREQUENCY OFPROCESS SOLIDS REMOVAL

REQUIREDFOR SLUDGEDIGESTION?

DRY SOLIDSAPIR DAYPLOW RATE OF

37$5 m'/DAY (1 MOD).OR 10.000 PEOPLE

SAS Anaerobic Aqua Cell

Septic Tank

Imhoff Tank

Primary Sedimentation

Primary Sedimentation & Trickling FilterWith Secondary Sedimentation

Primary Sedimentation & ActivatedSludge

Activatediludge (Package Plant)

Yes

Yes

Yes

Yes

Yes

Yes

Yes

YesNo

No

No

Yes

Yes

Yes

No

No

No

Yes

Yes

Yes Daily

Once/6-12 Months

Onc./1-2 YearsOn /20-60 Days

Daily

Daily

170 kg (375 lb.)

367.4 kg (810 lb.)

313 kg (690 lb.)

340.2 kg (75011)4

'558 kg (1230 lb.)

635 kg (1400 lb.)

No Daily 1020.6 kg (2250 lb.)

With longer retention times.

SOURCer AlTr

/-ten, C. and Stewart, W., Perlionnance Characteristics of a Covered Anaerobic Wastewater Lagoon Primary

tment System, NCAT ID 0 CA-78-032, Butte, MT, 1981

Parameter.

Rawsewageinfluent

Anaerobicequine°effluent*

% Remov51anaerobicaqaecell

80D. 218.4 109.0 50.0%

SS (mg/I) 247.9 27.9 88.7%

COD (mg/I) 518.0 142.0 72.6%

Turbidity (NTU) 205.0 103.4 49.6%

TOC (mg/I)

pH(average means)

271.6

7.4

67.5,

6.9

75.1%

Ammonia (mg/I) 40.9 3.4.0 16.9%

Coliform 5 X 10' 2 X 10' 96.0%

A

"6 hr retention time Cell 1; 0 hr retention time Cell 2

production records were Jot obtained.However, gas containment should not be aproblem if commercially produced -enclo-sures are used at a full-scale plant. Basedon process modeling and observations ofthe pilot plant, methane production shouldbe substantial.

Capital costs for the .AquaCell system'are estimated to.be approximately $1 to $2per gallon of treatment capacity per day,depending on the size of the system. This DS

comparable to the cost 'of primary. clari-fiers. In 1982, this process was consideredto be innovative arid qualified for 85 per-cent federal assistance through the Con-struction Grants Program.

Maintenance and operating costs shouldbe low because a separate sludge digestion

#11

CHAPTER PIRO7 .A V "

14,

4.

Solar Aquasysterns inc., at the San EIJI° Water Pollution Control Facility

process is not required and here are nochemical costs.. Sludge can accumulate inthe cells for relatively long periods of timewhich reduces handling and related costs.The system also eliminates the need forprimary clarifiers and their associatedcosts. Because the system treats the waste-water (not just separating the sludge likeclarifiers), patllogens are significantlyreduced and disinfection costs would belower. Operator training requirements areminimal, beCause the Aqua Cell system issimple to operate.

HIGHLIGHTS AND CURRINT STATUS -

As this test project demonstrated, thetwo-stage anaerobic process for primarytreatment hag the following advantages: 1

1) Relatively little energy is requiriad.2) It operates effeetively at moderate

temperatures.3) Methane gas is produced and could

be collected.4) It is stable and toltrant to variations

in influent.5) Maintenance and operating costs are

6) -Cakital costs are competitive withprimary clarifiers.

7) It is simple and has no moving parts.The anaerobic AquaCell system avoids

the drawbacks common to anaerobicsludge 'digestion systems and anaerobiclagoons. It can gather the gas producedand control odors; openonaerobic lagoonscannot'. The AquaCell is a medium-ratesystem and relatively stable. Consequent-ly, it could operate for !Ong periods .withonly intermittent checks and would not re-quire special operator skills. High-rate,anaerobic sludge digestion systems arerelatively sensitive and unstable, and re-quire careful monitoring to maintainproper performance.

In 1978, the Solar Aquasystems projectwas one. of the first to study the perfor-mance of a two-stage, anaerobic, fixed-film, primary treatmept system at the pilotscale. Since then, numerous sing%-cell,upflow systejns have been built. As of 1982,similar systems are eligible for 85 percentfunding under EPA's Innovative and Alter-native Technology. Program, and EPA isfunding tdditional-research.

CHAPTER THREE

WHO TO CONTACT

Mr. Steve Serfling, President,Solar Aguaststems, Inc. 41r

P.O. Box 88,Encinitgs, CA 92024Telephone (619) 753-0449Final Report: NCAT ID# CA-78-032DOE. Contaact No.: DE-FG03-78R901948

After primary treatmentof th. slorhesticlvastewaterin Cells One and Two, theefflUent was treated in threemore cells. Each of the addi-tional cells contained highsurfqce "bio-film" and "bio-web" substrates. Cell Threewas facultative and used asmall surface aerator anddiffuse bubbles aeration.Wat4 hyacinths, duckweedand fish were used in thelast two cells, The final threecells were funded by theDepartment of Interibr andthe Environmental Protec-tion Agency.

If the products of aquacul-ture wastewater treatmentare to be fully used, healthhazards found in the sewagemust be removed: The finalthree cells were used toremove heavy metals, PCB's,

pesticides, patttogens; SS,

BODs, ammonia, and othernitrogen and phosphatecompounds.

The system was tested tosee how well the series offive cells removed heavymetals and other toxiccompounds. After measur-ing the amountrof the .com-pounds added to Cell Ohodad the of thiieconipoUn,4 in the effluentleaving Cell Five, the re-searchers repartd ex-tremely high removaliiencies. Results indicatedthat removal riot with 4- or5-day retention times wereadequate to allow reuse ofeffluent for food production,if influent concentrations oftoxics are within the rangeof dom tic, rather' thanindustri types of sewage.

THPFE ADOiliONAL CELLS IMPROVE SYS' M PER,ORMANCE

A Controlled EnvironmentWasteweter AquacultureSystem for Water Reuse,OWRT/RU-80/11, U.S. De-partment of the Interior,Washington, DC.

Gee and Jenson, Inc., WaterHyacinth WastewaterTreatment Design Manual,

.NTIS, Springfield, VA, June1980.

Ghosh, 1., and Klass, D.C.,Two -phase AnaerobicDIgestton; U.S. Patent04,022,66.4,May 1977.

Hanisak, M.D., Ut "Re:,cycling the Nutrients inResidues, from MethaneDigesters of AquaticMacrophyt*S for New Bio-mass Production," ResourceRecovery and Conserva-tion, April 1980.

--Heldman, J.A., TechnologyAssegsment of AnaerobicSystems for MunicipalWastewater Treatment:(1) Anaerobic -FluidizedBeds (2) ANPLOW, U.S. En-vironmental ProtectionAgency, ERA-60072-82-004,Cincinnati, OH, February1982.

U.S. Department of liner-gy/Argonne ContractorsR&D Workshop: Convert-ing Waste to energy, ANL/CNSV-TM-96, NTIS, Spring-field, VA, December 1981.

Wolverton, B.C.,' andMcDonald, R.C., "WaterHyacinths for UpgradingSewage Lagoons to MeetAdvanced WastewaterTreatment Standards,"NASA/NSTL, Memorandum,X-72730, October 1976.

0

..1

24

r

VERMICOMPOSTING:WORMS USED TO PROCESS SLUDGE Lufkin, Texas, Sewer Treatment Plant

Previous experimental work done in SanJose, California, and the practical use ofsludge in the worm/fish bait industry inTexas, indicated that worms could be usedto process sludr. Aware of this work, theCity of ruf kin began construction of a22,800 ft2 vermicomposting unit at thecity's Sewer Treatment Plant in 1979.

Earthworms transformlarge volumes .of organicwastes to earthworm ma-nure, called castings. Thisprocess Is known as "vermi-

.composting.",The conversionof wastes to castings in.creases the surface areaenormously, and this accel-rates drying and Microbialactivity. Castings cruartblieasily and no longer gener-ate heat, so .castings are afinished Compost that willnot burn plants.

Vermicomposting of wastesat any more than backyardscale has been practiced onlysince 1970. In that year, a fa-cility In Hollands Landing,Canada, started vermicom-posting sew_ age sludge, food-processing wastes, and ma.num. Worms have convertedpulp and paper sludges tocastings in Japan since 1/71.The Japans have expanded

VFRMSCOMPOSTING

their efforts to Include theprocessing of municipal 'sludge and other waste. Inthe United States. pioneering.efforts in the vermicompost-Ina of sewage sludge In-cluded demonstration Proi-iicts In San Jose: California:Keysville, Maryland: Ridge-field, Washington; and Titus-vale, Florida. Vermicom-posting Is also being used inHolland, Italy, and the SouthPacific.

Basic and applied researchat the University of Now Yorkin Syracuse and Cornell Uni-versity in Ithaca, New York,have developed greater fun-damental knowledge ofearthworm waste f1101101p-ment systems. The objectiveof this work is to provide ascientific and engineeringbasis for the design and op-oration of vermicompostingsystems.

TECHNOLOGICAL PROCESSES ANDOPERATION

The worms live in 12 cells, "esach 20-ftwide by 95-ft long (see Figure 3.6). Thereare six cells on each side of a central work-ing aisle. Each cell has a bed of aged saw-dust, initially 6-inches deep, spread onpolyethylene film on the ground. For eachsquare foot of surface area, there is aboutone-half pound of earthworms. (Eisen's::foetida). Each cell, its constructed of steeltubing arches coverild by two layers of six -mil plastic (one blacliand one clear).filledwith air from a blower.

The Lufkin treatment plant is a conven-tional 4.5 MGD facility with activatedsludge secondary treatment. For.the vermi-

0 irt: dlt, 100!W Vim

Pump Station

Mixing Tank

Dump Station

F/9 1t Ishtar

SecondaryActivated

udwa Unit

CentralWorkiag Alike

Worm Dada

To ConventionalTtoatmant

Primary TO Slade' HeatCistffiat Stabilisation

. .

Raw Sawa,* Lin.

Figure 3.6 Lufkin Vermicomgosting Facilities

composting project, one part stabilizedsludge from the primary clarifier and onepart secondt;ry activated sludge are mixedin a holding tank and pumped to the wormbeds. The sludge 'mixture contains 3.5 to 4percent solids and is piped from the hold-ing and mixing tank and sprayed over thebeds at a rate of .Q5 lb (dry) iday/fta: Treat-ment plant operators designed special eon-stant-prf*ure valves to distribute thesludge. altich bed is covered by three,sprayers controlled by an operator fromthe central aisle. The worms ingest anddigest the sprayed sludge; this uses thewater avid stabilizes the sludge as it is'con-verted to castings.

The worms are spray-fed sludge on anaverage of once a day for 3 to 5 minutes inthe late afternoon. The 'beds tire hoseddown with additional water to keep them atthe desirable 70 to 95 percent moisturecontent. The beds are also monitored fortemperature and pH. The optimum bedtemperature range is 60° to 75°F, and pHis kept at 6.4 to 6.9 with occasional applica-tions of small amounts of lime. When a crustforms on top of the beds, usuiply at 1- to3-month intervals, the top 2 inches of thebeds are rototilled lightly. It takes about 20minutes to till a 1,900 ft2 bed. Beds are tilledwhen the worms are relatively deep, solosses are minimal. One person can main-tain all 12 of the cells.

Worms Ore sensitive to changes in the -weather and are inclined to crawl out of thebeds during rainy periods or thunder,storms. Lights are turned on in the, cells atthese times to keep the worms from leav-ing. Normally, the cells are kept dark andwell-ventilated.

Castings are toxic to the worms, and theymust migrate or die if-fresh bedding is notavailable. At approximately 6-month inter-vals, of when the casting exceed 50 to 70percent of the bedding, the material fromthree /-foot 'wide trenches is removed forthe length of the beds. The trenches are

CHAPtlIR TH111111 2341-

k" "

Lufkin, Texas, Sewer Treatment Plant

filled with aged sawdust, and the fresh bed-ding areas are watered and fed while therest of the bed is left unmaintained. Theworms migrate to the new misterial, andafter about 2 weeks the rest of the old bed-ding is removed and replaced.

Energy and Economics

Due to the experimental nature of thisproject, the state Health Department does'not allow Lufkin to sell either worms orcastings. The castings are used by theLufkin Parks and Recreation Department asa soil amendment-fertilizer and pottingsoil. The wholesale kralue of castings isabout $30 per 'ton, but to date the HealthDepartment restrictions still stand, and nocommercial development has taken place.

Under good conditions, the worm popuu=lation doubles every 2 to 3 months. Assum-ing a 25 percent recovery -rate, about'10,000 lb of worms could be harvestedevery 6 months. At $1.50 per pound fqr liveworm, the income potential is about$15,000 per year. As a protein source forfish or animal feed, worms are worth about$130 per ton. '-

Exclusive of potential income from cast-ings and worms, vermicomposting . is apromising sludge processing technology.Based on the Lufkin data, it is estimated

a that the cost of processing sludge is from$160 to $184 per dry ton, which is compar-able to the costs of other treatment proc-esses (see Table 3.4).

Thii process is quiet, requires negligibleenergy, produces "topsoil" and protein,and uses biological processes rather thanenergy and chemica to process thesludge.

Sludge Disposal Method

IncinerationCompostingSurface impoundmentsLandfillsOcean dumpingOcean dischargeLandspreading

Source:Office of Water Program Operations, U.S. Environ *Mal Protec-tion Agency, A Guido to Regulations end Owl for theUtilization and Disposal of Municipal Sludge, E A- 430/9 -80-015, Washington DC, September 1980. (AdIestid 4 1982 S.)

$ /Dry Ton

$96 to 2878,4 to 239

Apprx. $30SW to 271836 to 60

Apprx. $24$48 to 251

Highlights and Current 'fetus

Four of the twelve beds at Lufkin are fullyoperational. The other elRjht are now beingreconditioned after suffering from delayedmaintenance and ant predation.

Restrictions on the salts' of worms andcastings produced by the system have ham-pered commercialization, but the projecthas added substantially to the knowledgeand practical information on vermicom-posting at a relatively large scale.

The Lufkin vermicomposting effort ha' sstayed in operation, despite setbacks,because -of strong and continuing support'from local officials. 'The project has alsobenefited from assistance from the U.S.Department of Energy and the State ofTexas.

WHO TO CONTACT

Mr. Harvey Westerholm, City Mana4rCity of Lufkin300 East ShepherdP. 0. Drawer'190, Lufkin, TX 75901Telephone (713) 634-8804Final Report: NCAT ID # TX-79-008DOE Contract No.: DE-FG46-79R610985

Collier, J., et al., Conver-sion of Municipal West. -'water Treatment PlantResidual Sludges intoEarthworm Gifting' forUse es fertile Topsoil,Diane Livingstone & Associ-ates, Santa Cruz, CA, Febru-ary 1981.

Donovan, John, Engineering-.* Aseepment of Verrnicom-

posting Municipal Waste-water Sludge, EPA- 600/S2-82.075, NTIS; Springfield, VA,June 1981.

Hartenstoin, R., Utilizationof Earthworms and Micro-organisms In.StehIllzotion,Decontamination and De-toxification of ResidualSludges from Treatmentof Wastewater, Final Re-port, National Science Foun-dation Protect PFR 78. 09331,National Science Foundation,Washington, DC, February1981.

LOhr, R.C., et al., WasteMenegenvent Using Earth -worms Engineering andScientific Egletionships.Progress Reloort, CornellUniversity, Ithaca, New York,August 1982.

Pincince, A.8., et al., Ver-micompoeting of Munkipalsolid Wastes and Munici-pal Weetevreter.Camp Drbsser, land McKee,Inc., Boston, MA, April 1980.

Proceedings of the Con-femme on loll OrganismsIn Sludge Management,The State University of NewYork, Syracuse, NY, June1978.,

Proceedings of the Work-else, on the tole of Earth-worms in the Stabilizationof Organic Residues, Vol. 1and 2, Kalamazoo NatureCenter, Kalamazoo, MI, April1980.

REFERENCES

CHAPTER THREE

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CHAPTER FOUR:lESSONS LEARNED AND FUTURE DIRECTIONS

The case studies featured in this puLftcar,lion, other projects conducted uncle theDepartment of Energy's Appropriate Tech-nology Small Grants Program, and relatedwork provide eeveral valuable lessons forthose concerned with municipal sewagecollection and treatment. -

Wastes are resources. Chicago usesdigester gas lo produce steam. In NorthAndoverthe plant effluent stream is beingharnessed to produce electricity. And atLufkin, worms are, processing sludge toproduce a valuable soil amendment.

Conservation works and pays.' On anational basis, approximately 20-25 percentof municipal wastewater treatment budgetsis allOcated for energy. As the case studiesindicate, there are two basic ways to-cut

.energy consumption and costs: audit andmanage treatment processes effectively,and use th esources of the "waste( andthe treatm t processes themselves. TheWalterboro project demonstrates the valueof energy audits and management, and theChicago and North Andover projects, usebyproducts of the treatment process to helpmeet in-plant energy requirements. .

Work with what you have. Majorohanges are not necessary to achieve re-sults. Walterboro; North Andover, andChicago all built on existing situations toimprove the performance of their systems,and all three of these projects .also recycledequipment and buildings as their treatmentplants evolved.

_

Modify when time and money permit.Working with what yew' have applies totime and money as well haliquipment andbuildings. Sewage treainient is a majorcomponent of municipal budgets, and costsavings can be realized by, incorporatingimprovements into lonTrange planning.

Use problems to oxplorov,options. Noone likes to see problems crbp up, but whenthey do, they often bring opportunitiesalong with them. In each case cited in thispublication, an existing problem was themotivation for change: high energy coots,non-compliance, inadequate capacity. Asthis publication also illu'strates, there is awide range of options available to helpsolve problems.

Sewage problems will not go away.Sewage collection and treatmen) is a persis-tent need and essential service in this coun-

t try. It is a service taken (for granted by mostof the populigion, and in effect, this placesadditional responsibility on professionalswho .itct on the public's behalf. Recentexperiences and a broader understandingof environmental hazards, water resourcecycles, and the increasing costs of all publicservices make it even more important todevelop and operate the most effective andefficient sewaq,e treatment'systems possible.

Appropriate technologies can helpprovide answers. Appropriate technol-ogies, applied to both conventional andalternative forms of sewage treatment, canhelp plant managers harvest the energyand nutrients of sewage. Viewing sewage,,as a resource rather than a liability cansave energy and taxpayers' money.

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APPENDIX A

:ELECTED SEWAGE TREATMENT PROJECTS FROM THEDEPARTMENT. OP ENERGY APPROPRIATE TECHNOLOGY SMALL GRANTS PROGRAM

Oroject typeNIMPOInollibOrPolle.s

Project grant*.

Algae and plant biomassLised to treat wastewaterconverted to alcohol

An alternative on-site sew-age system to conservewater

Bacterial seeding used to .

save energy

Blue-green algae used totreat wastewater

ti

Conversion of sewageMudge to oil with hydropy-rolysis

Fish and bivalves used toremove suspended solids

Methane digester for waste-water grown aquatic plant§

Methane produced frommunicipal refuse

On-site vermicompostingused to convert commercialprodude

Owner-built compost toiletdesign

Sequencing mesophilic andthermapitilic anaerobicdigesters

Sewage treatment effluentused as evaporative coolantfor solid waste-fired gener-ating plant

Solar eneitgy used t6 drysludge

Water hyacinths in solargreenhouses used to treatwastewater '

City of Cayce, SC

Proje-ct scale

Pilot-scale test system

Soil -crete Slip Company, Full-scale test systemNavajo Dam, NM

Department of Pub!Works, Springfield, 'MA

Experimental Energy, Envi-ronment, Inc., Atlanta, GA

Patrick S. Kujawa,Vienna, Va

Everett Sewer Department,Everett, WA

Solar Aquasysterns,Encinitas, CA

North Country.RecyclingResource Recovery;Winthrop, NY

Small-scale test system

Small-scale test system

Feasibility study

Small-scale test system

Small-scale test system

Pilot-scale test system

Semple Street Food Co-op, Full-scale test systemPitteburgh, PA

farallones Institute RuralCenter, Occidental, CA

City of Atlanta, GA

Valley City, ND

Jefferson Parish Dept. of\Public Utilities,.New Orleans, LA

of San Marcos, TX

1

Full-scale test system

Bench-scale test system

Feasibility study

Small-scale test system

Pilot-scale test system

MIMI= A U.S. 00VSNWPISNT psfeixwo orribt: 1903.- 3S0 -903 : 113 ,

fur

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