household wastewater treatment - twontwon.tamu.edu/media/385829/reducing risk of ground...household...

Household Wastewater Treatment

Virtually all farms use a septic system orsimilar on-site wastewater treatment system.While these systems are generally economicaland safe, household wastewater can containcontaminants that degrade water quality forsuch uses as drinking, stock watering, foodpreparation and cleaning.

Potential contaminants in household waste-water include disease-causing bacteria, infec-tious viruses, household chemicals, and excessnutrients such as nitrate. Viruses can infect theliver, causing hepatitis, or infect the lining ofthe intestine, causing gastroenteritis (vomitingand diarrhea). If coliform organisms (a group ofindicator bacteria) are found in well water, thewater is potentially dangerous for drinking andfood preparation. Septic systems are a potentialsource of this pollution, as are livestock yards.

A properly installed and maintained systemfor treating and disposing of household waste-water will minimize the impact of that systemon ground water and surface water. State andcounty codes specify how wastewater systemsmust be designed, installed and maintained.All new systems must be installed by a statecertified installer and inspected by a state certi-fied inspector prior to use. At a minimum, fol-low the Texas Natural Resource ConservationCommission codes for design and construction,but also consider whether the minimumrequirements are sufficient at your site.

A glossary of terms at the end of this publi-cation will clarify terminology. This publicationcovers the following topics:

1. Septic tanks/soil absorption systems

2. Quantity of wastewater

3. Quality of wastewater

4. Collection of wastewater

5. Treatment systems

6. Disposal system

7. Assistance with failing systems or newdesigns

8. Evaluation table

Septic Tanks/Soil Absorption Systems

The most common form of on-site waste-water treatment is a septic tank/soil absorptionsystem. In this system, wastewater flows from

the household sewage lines into an under-ground septic tank. The following then occurs:

★ The waste components separate, with theheavier solids (sludge) settling to the bot-tom and the grease and fatty solids (scum)floating to the top.

★ Bacteria partially decompose and liquefythe solids.

★ Baffles in the tank provide maximumretention time of solids to prevent inletand outlet plugging, and to prevent rapidflow of wastewater through the tank.

★ The liquid portion (effluent) flows throughan outlet on the septic tank to the soilabsorption field.

★ The absorption field is usually a series ofparallel trenches, each containing a distri-bution pipe or tile line embedded in drainfield gravel or rock.

★ The effluent drains out through holes inthe pipe or seams between tile sections,then through the drain field gravel or rockand into the soil.

★ The soil filters remaining minute solids,some dissolved solids, and pathogens (dis-ease-producing microorganisms). Waterand dissolved substances slowly percolateoutward into the soil and down towardground water or restrictive layers. A por-tion of the water evaporates into the air,and plants growing over the drain fieldlines utilize some of the water.

Figure 1 shows a typical household systemfor wastewater generation, collection, treat-ment, and disposal. While such systems maybe called by various names (such as septictanks or subsurface treatment and disposal sys-tems), they are similar. In this discussion theterm septic tank is used. Note the list ofoptions below each part of the diagram. Youmay wish to circle the parts found in your sys-tem. The “leakage,” “overflow,” “infiltration”and “clearwater” components represent possi-ble problems with the system. Unfortunately,these problems are often difficult to recognize.Over-flow from systems may be noticed as wetspots, odors and changes in vegetation cover.Water entry (infiltration and clear water) willbe more difficult to detect. To help detect anywater entry, trace where the floors drain, theroof drains, the foundation drains, and wheresumps are directing outside water into the

treatment system. Leakage from the collectionand treatment system, as well as infiltration ofwater into the system through unsealed joints,access ports and cracks, can be very difficult to

assess. The flow chart at the bottom of the boxfollows the flow of wastewater and sludgethrough the treatment system.

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InfiltrationProblem Overflow

Problem

SALT

ClearwaterProblem

SludgeProblemLeakage

Problem

ExcessiveWater Use

Scum

Sludge

WaterSupply*

Figure 1. Typical household wastewater treatment system with problems. Illustration by Andy Hopfensperger, University ofWisconsin-Madison Department of Agricultural Engineering.

Water Use Collection Pretreatment Additional Treatment DisposalQuantity* Leakage* Septic Tank* Sand Filter Soil Absorption*Quality* Clearwater* Holding Tank Nitrogen Removal In Ground

Infiltration* Cesspool Disinfection BedAerobic System Trench

Mound, At Grade* = Elements Illustrated Pump and Haul

Quantity of Wastewater

The best strategy is to minimize the volumeof household wastewater entering the treat-ment system. This is important because lessflow (volume) means better treatment, longersystem life, and less chance of overflow. Lessvolume also lowers costs by reducing the num-ber of times the holding tank must be emptied.

The quantity of water used depends uponthe number of people using the dwelling, theirwater use rates, and the maintenance of thewater supply system. Average water use inrural households is 40 to 50 gallons per personper day. With low-use fixtures and individualawareness and concern, a reduction to fewerthan 25 gallons per person per day is possible.However, even conservative use by several peo-ple may exceed the capacity of the wastewatertreatment system.

Reducing the volume of water entering thesystem will improve treatment by increasingthe time the waste spends in the system, thusproviding more time for settling, decomposi-tion, aeration and soil contact.

Consider the following ways to minimizewater use.

★ Eliminate non-functional uses, such asflushing toilets to dispose of tissues orother waste that should be handled assolid waste. Turn off water between uses,fix plumbing fixture leaks, and try to elim-inate sources of clear water infiltrationinto the system. (For example, divert roofdrains away from the soil absorptionfield.)

★ Consider which actions use the mostwater. Toilet flushing usually ranks thehighest. Low-flow models could decreasewater use by more than half. Compostingtoilets allow even greater reductions, butthey can present other waste disposalchallenges.

★ Bathing and washing clothes are next inorder of water use. Consider installinglow-flow or controlled-flow showerheads,which give good cleansing with less water;taking shorter showers; and taking “wet-down-soap-up-without-water-then-rinse”showers.

★ Wash full loads of clothes to save soap andwater. Front loading washers use muchless water. When running small loads, besure to use the reduced water level set-ting.

★ Use modern, efficient plumbing fixturesand appliances, including 0.5- to 1.5-gallontoilets, 0.5- to 2.0-gallons-per-minute(gpm) showerheads, faucets of 1.5 gpm orless, and front loading washing machinesof 20 to 27 gallons per 10- to 12-pound dryload. These fixtures and appliances canreduce water use from 30 to 70 percent(see Fig. 2.).

★ Use water softener devices with care, be-cause they may use significant amounts ofwater. Proper adjustment and timing ofthe softener’s regeneration mechanism canreduce excessive water use. The flushbackwash should not go to your septictank.

★ Eliminate household water leaks. A leak inthe home may be detected by opening thecleanout (usually located between thehouse stub-out and the septic tank) andchecking for a continuous flow throughthe pipe to the septic tank. Since a smallflow is sometimes difficult to see, youshould drop a pinch of sand into the pipeand watch to see if the sand is carriedaway. If the sand is carried away, you havea continuous leak inside the home. To iso-late the leak, check each fixture. If a leak-ing toilet is suspected, put a small amountof food coloring into the toilet and checkto see if it appears in the flow through thecleanout.

★ Prevent water from other sources fromentering either the septic tank or the drainfield. Divert water flowing from roofdrains away from the septic tank andaway from the drain field. Construct aberm or a swale upslope of the drain fieldif there is surface runoff flowing down-slope over the drain field. However, avoiddiverting the runoff toward your well.

★ Do not allow water from basement floordrains or foundation drains to enter theseptic tank through the house plumbing.

Keep in mind that your family’s awarenessof your water use and how it can be reduced isas important as the use of water conservationdevices.

Quality of Wastewater

Domestic wastewater usually contains rela-tively small amounts of contaminants — lessthan 0.2 percent (i.e., it is 99.80 percent “pure”water), but even small amounts of contami-nants can make a big difference in the useful-ness of the water.

Contaminants found in wastewater includethe following:

★ Bacteria and viruses, some of which cancause disease in humans. These microor-ganisms are large enough to be removedby settling, or through filtration in sandbeds or soil. Many will die as they passthrough the system.

★ Suspended solids are particles that aremore dense (sludge) or less dense (scum)than water and that can be removed byfiltration. Most can be separated from liq-uid waste by allowing enough time in arelatively calm tank. Grease and fats are apart of the suspended solids. Filtrationbeds and absorption systems can beclogged by wastewater high in suspendedsolids.

★ High oxygen demand can lower waterquality. The microorganisms that decom-pose organic wastes (such as blood, milkresidues and garbage grindings) use lots ofoxygen. The amount of oxygen required to“stabilize” wastewater is typically mea-sured as biochemical and chemical “oxy-gen demand.” Aeration and digestionprocesses, in the presence of oxygen andorganisms, produce stable, low-odorwastewater when given enough time.However, wastewater with excess oxygendemand can cause problems for soilabsorption fields, ground water, streamsand lakes by reducing levels of oxygen inthe water.

★ Organic solvents from cleaning agents andfuels may not be degraded or removedthrough treatment and can pass alongwith the wastewater back into the watersupply.

★ Nutrient contaminants are composedmainly of nitrogen from human wastes,phosphorus from dish washer detergentsand some chemical water conditioners.Nitrate-nitrogen is a common ground

Outlet

Vent

ElectricMotor

Inlet

Aeration Compartment

Air Discharge

SettlingCompartment

Sludge ReturnMixing Return

Figure 2. Aeration tank of a household aerobic treatment system. Source: Onsite Domestic Sewage Disposal Handbook, MWPS-24,Midwest Plan Service, 1982

water contaminant, and phosphorus is acommon contaminant of surface water.

Here are some ways to improve wastewaterquality:

★ Minimize use of the garbage disposal unit.Garbage disposals deposit large amountsof suspended solids and organic matterinto the septic system, as well as usingadditional water.

★ Do not clog septic tanks by putting itemssuch as fats, grease, coffee grounds, papertowels, sanitary napkins, tampons or dis-posable diapers down drains.

★ Do not put toxic substances in drains.They might end up in the ground water.These include solvents, degreasers, acids,oils, paints, disinfectants and pesticides.However, this does not prohibit the use ofbleach to disinfect laundry or the washingof clothing worn for pesticide applications.

★ Do not use chemicals to clean your sys-tem. They may interfere with the biologi-cal action in the tank, clog the drainfieldby flushing sludge and scum into the field,or add toxic chemicals to ground water.

Collection of Wastewater

Collect all waste that needs treatment andminimize the loss of untreated waste. Leakingpipes or treatment tanks can allow wastewaterto return to the local water supply without ade-quate treatment. Exclude from the treatmentsystem water that does not need treatment ordisposal.

Infiltration of clear water overloads the sys-tem and dilutes the wastes. Do not allow rain-water or water from basement floor drainsumps, foundation drains or roof drainage toadd to your waste water volume. Divert cleanwater away from the house, any wells, and anywastewater treatment system.

Treatment Systems

Make wastewater suitable for treatment anddisposal in the soil by reducing the concentra-tion of contaminants in the wastewater.

Septic tanks retain most of the suspendedsolids (sludge) and scum from wastewater. Inthe tank, bacteria digest and compact thesludge. The partially treated water moves to

additional treatment or disposal, for example,in the soil absorption field.

The design and construction of septic tanksinfluence their water tightness and effective-ness at retaining sludge and scum. Multipletanks or chambers in series can improve sludgeand scum removal. Gas deflectors and filterscreens or inclined-plate settling units help tominimize solids entering the drain field. Tanksshould be sized to accommodate at least 24hours of wastewater flow while still allowingfor sludge and scum retention. Pumping thetank before it is more than one-third filled withscum and sludge (generally every 3 to 5 years)improves the functioning of the system. Whenthe tank is pumped, you should have the baf-fles checked and also check for tank leaks.Septic tanks should be made of reinforced con-crete, polyethylene or prefabricated fiberglass.

Aerobic (oxygen using) biological systems,which are considered packaged systems, treatwastewater better than the typical anaerobic(no oxygen) septic units, thus improving solidsseparation, releasing volatile chemicals, andreducing sludge volume. These systems are,however, more expensive to operate and main-tain and are more often subject to problemscaused by changes in wastewater quality orenvironmental conditions. Aerobic systems areoften used because they produce high qualityeffluent which may be disposed of throughconventional trenches or drip irrigation, orsprayed on top of the ground.

If you have an aerobic system, you shouldhave a maintenance person inspect the unitthree times each year. The maintenance personshould check the aeration mechanism, the dis-infection unit (tablet chlorinator), and othercritical aspects of the unit.

Between inspections you should check thetablet chlorinator for chlorine tablets. If thereare no tablets, fill the chlorinator immediately.An empty chlorinator increases the chance thatdisease causing organisms will come into con-tact with people.

Additional treatment after wastewater haspassed through the septic system can reducethe concentration and amount of contaminantsin the wastewater and make it suitable for dis-posal.

Aerobic systems may be used for additionaltreatment of septic tank effluent, and these sys-

tems can yield a better quality effluent suitablefor more disposal options.

Sand filters also improve the quality ofwastewater after septic tank pretreatment.Effective treatment involves aerobic biochemi-cal activity as well as physical filtration. Filtersconsist of 2 to 5 feet of sand (or other media) ina bed equipped with a distribution and collec-tion system. Wastewater is applied by dosing,and it may be recirculated to improve treat-ment.

Filters should be designed according to thepretreatment system used, the quality of thewastewater, the hydraulic loading rate, the dos-ing frequency, the temperature, and the distrib-ution and collection systems used. Filter main-

tenance includes resting, occasional raking,removal of clogged or crusted surface media,filter media replacement, and attention to dos-ing equipment.

Wastewater treated in such systems is gener-ally lower in bacteria, nitrogen, phosphorus,oxygen demand, suspended solids and organicmatter. The amount of reduction depends onthe design of the system.

A disinfection unit is a system that kills dis-ease-causing microorganisms in wastewater,and is used when discharge on the surface ispermitted. Chlorine, iodine, ozone and ultravio-let light systems are available to treat goodquality effluent, such as that from properlyfunctioning aerobic units and sand filters.

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Observation and Ventilation Pipe

1/4" Screen

12" max Soil10" Rock24" Sand3" Pea Gravel6" Rock over Pipe

10' max to next collection line

END VIEW

SIDE VIEWCollection LineSlope 6" / 100'

Rock

Observation Pipe

Plug

Soil Cover

Sand

Pea GravelRock

PLAN VIEW

Observation Pipe

Collection Line

Distribution Lines. 3" o.c.

Distribution Lines. 3" o.c.

6"

Figure 3. Buried sand filter. Source: Onsite Domestic Sewage Handbook, MWPS-24, Midwest Plan Service, 1982.

Disposal Systems

To reduce the risk of wastewater contaminat-ing water supplies, disperse effluent and maxi-mize its contact with soil and plant roots.

Discharging treated or untreated wastewaterfrom private systems directly to surface watersor ditches is illegal in Texas. Illegal wastewaterdischarges or wastewater surfacing above thedrain field can endanger your health as well asthe health of others in your community.

Subsurface Treatment Systems

Subsurface treatment and disposal, using soilabsorption systems (trenches, beds, ormounds), is the common disposal system fol-lowing septic tanks. There are, however, siteswhere soil absorption systems will not functionproperly and will endanger ground water quali-ty. Unsuitable sites are those with impermeablesoils, shallow rock, shallow water tables, orvery permeable soils such as a sand or gravellysoil.

Suitable sites are those with deep, well-drained, well-developed, medium-textured soils(such as silt loam and loam). Soil beneath thedisposal area must be unsaturated to provideadequate treatment. Unsaturated soil allowsthe effluent to remain aerobic and to flowthrough tighter soils, thereby filtering contami-nants and giving soil microbes longer contacttime with soil organic matter. Approximately 4feet of unsaturated soil should be maintainedbeneath the disposal system to adequatelyremove pathogens and organic matter fromwastewater.

Disposal systems that are downslope and farfrom the water well will better protect yourwater supply from possible contamination fromwastewater.

Surface Treatment Systems

When compared to subsurface treatment sys-tems, surface treatment systems promote moreevapotranspiration (removal of effluent byevaporation and loss through plants). Increasedevapotranspiration decreases the amount oftreated effluent that can reach the water sup-ply. However, disposal systems that apply thetreated effluent directly on the ground surfacemust have an approved method of treatmentand should disinfect the effluent before appli-cation. Keep the following application strate-gies in mind:

★ The application of effluent in a surfacetreatment system should not producerunoff or ponding.

★ Spreading the effluent over a larger sur-face area promotes maximum vegetativeuptake of nutrients. The entire applicationarea should be covered with vegetation sothat most of the effluent will encounterplant roots before reaching ground water.The plant roots will utilize many of thenutrients in the wastewater.

Assistance with Failing Systemsor New Designs

If you suspect your household wastewatertreatment system is backing up or your distrib-ution system is clogged, first contact a plumberor treatment system installer, who may havesuggestions for extending the life of your sys-tem. The county public health office is thelocation to visit for permits to repair or replacea wastewater treatment system. Take the fol-lowing steps to reduce any risk of contaminat-ing ground water:

★ Do not use septic tank cleaners that con-tain degreasing solvents such as TCE,which can contaminate ground water.

★ Do not place more soil over a surfacingsoil absorption field; this does not fix thesystem, and water will surface again.

★ Do not pipe sewage to the road ditch,storm sewer, sink hole, drainage well,stream, or drain tile; this pollutes thewater and creates a health hazard.

★ Do not wait for the system to fail beforepumping the septic tank. Once a systemfails, it is too late to pump the tank.

★ Remember that spreading the effluentover a larger area and placing the effluentshallower in the soil will decrease thechance of contaminating your water sup-ply.

A properly designed, constructed and main-tained septic system can effectively treat waste-water for many years, but it requires routinemaintenance. For additional information onseptic systems, contact your county Extensionagent, local health department, or TexasNatural Resource Conservation CommissionOn-Site Wastewater/Agricultural Division (512)463-8260.

Evaluation Table

The following table can be used to help agri-cultural producers and rural homeownersdetermine the risk that drinking water on agiven property may be contaminated becauseof the management practices being used. Foreach category on the left that is appropriate,

read across to the right and circle the state-ment that best describes conditions on yourland. Allow 15 to 30 minutes to complete thetable, and skip any categories that do notapply. Note any high risk ratings and takeappropriate actions to remedy them. Strive forall low or low-moderate risk ratings.

Assessing the Risk of Ground Water Contamination from Household Wastewater TreatmentLow Risk Low-Moderate Risk Moderate-High Risk High Risk


Internal water use Conservative water Moderate water use. High water use. Use Excessive wateruse. Use water- Use a few water- very few water-con- use. Use no water-conserving fixtures. conserving fixtures. serving fixtures. conserving fixtures,Routinely check for Periodically check for Rarely check for and never check forand repair leaks. and repair leaks. repair leaks. Water and repair leaks,Water softener Water softening re- softening recharges and water softeningrecharges are infre- charges to septic tank to septic tank more recharges to septicquent or not connect- twice per week or less. than twice per week. tank more thaned to septic tank. twice per week.

Unnecessary water No inflow. Rain-water Moderate inflow. Rain- High inflow. Neither Excessive inflow.entering treatment runoff and roof drains water runoff and roof rainwater runoff nor Rainwater runoffor disposal system are diverted away drains are diverted roof drains are divert- and roof drain flow

from septic tank and away from septic tanks ed away from the directly over septicdisposal area. The and disposal area. drain field and septic tank or drain field.basement or founda- However, the system tank. The septic Septic tanktion drain is not con- does receive water tank receives water receives flow fromnected to the system. from either foundation from basement or foundation and

or basement drains. foundation drains. basement drains.


Solids No use of garbage Minimal use of gar- Moderate use of gar- Daily use of gar-disposal unit in bage disposal (1 to 2 bage disposal unit (3 bage disposal unit.kitchen sink. times per week). to 5 times per week).

Chemicals Minimal use of house- Careful use of house- Moderate use of Extensive use ofhold chemicals (cups hold chemicals (pints household chemicals household chemi-per week). No dis- per week). Minimal (quarts per week). cals (gallons perposal of solvents and disposal of solvents Moderate disposal of week). Extensivetoxic cleaning agents. and toxic cleaning solvents and toxic disposal of solventsNo water softener or agents. Water softener cleaning agents. and toxic cleaningnot recharged on site. used, recharged on agents.

site.

Oils/Grease No disposal of grease Minimal disposal of Moderate disposal of Extensive disposalor oils into sewer. grease/oils. Oil and grease/oils. No of grease/oils.Domestic wastes only. grease wiped from attempt to reduce

cooking utensils disposal of grease/oilbefore washing. from household, but

little generated.

Pretreatment System

Cesspool (these are Any cesspool,illegal systems) direct discharge of

water, injection wellor seepage pit.

Assessing the Risk of Ground Water Contamination from Household Wastewater TreatmentLow Risk Low-Moderate Risk Moderate-High Risk High Risk

Pretreatment System (continued)

Septic tank More than one tank in One tank or one-com- Metal or cinder block Any homemade de-series or two-compartment tank. Tank tank. Total liquid vices, particularlypartment tank. Tank made of reinforced capacity less than with small volumes.made of reinforced concrete, polyethene 500 gallons. Tank is Tank or device hasconcrete. Liquid or fiberglass. Liquid pumped every 7 or never beencapacity of tank is capacity of tank is less more years. pumped.equal to or greater than 300 gallons timesthan 300 gallons the number of bed-times the number of rooms. Tanks pumpedbedrooms. Tanks every 5 years.pumped every 3 years.

Packaged aerobic Maintenance program No maintenance pro- No maintenance, No maintenance,system followed. gram, but no notice- occasional failures. frequent system

able failures. failure.

Tablet chlorinator Chlorine tablets pre- Chlorine tablets are Chlorine tablets are No chlorine is insent. Strong chlorine disintegrated and disintegrated and chlorinator and nosmell. caked on walls, but a caked on walls and chlorine smell is

chlorine smell is no chlorine smell is present.present. present.

Disposal of Wastewater

Horizontal separa- Offsite disposal. Subsurface disposal Subsurface disposal Upslope from well.tion of wastewater downslope more than downslope less thandisposal site from 50 feet from well. Sur- 50 feet from well.water supply (sub- face disposal more Surface disposal lesssurface or surface) 200 feet from well. than 200 feet from

well.

Vertical separation Offsite disposal. More than 6 feet to 3 to 6 feet to saturat- Less than 3 feet toof wastewater dis- saturated soil or bed- ed soil or bedrock. saturated soil orposal site from rock. bedrock.water supply(subsurface)

Soils Offsite disposal. Medium- or fine-textur- Medium-to coarse- Very coarse sandsed soils (silt loam, textured soils (sandy or gravel.loam, clay loams, clay). loam, sands).

Subsurface disposal Pressurized system Pressurized system Gravity system with Gravity system withsystem which uniformly which uniformly applies shallow trenches. deep trenches or

applies effluent effluent throughout There is healthy bed. There is littlethroughout entire entire field. Deep vegetation above vegetation abovefield. Shallow trenches or bed with- trenches and vege- trenches or bed.trenches or bed out covering of healthy tation is regularlycovered with healthy vegetation. harvested.vegetation. Vegetation harvested regularly.

Surface application Irrigation area is Irrigation area is Irrigation area has Irrigation area isdisposal system covered with healthy covered with healthy bare spots and it totally bare and is

vegetation. Vegetation vegetation. Vegetation appears that irriga- producing channel-harvested regularly. is rarely harvested and tion is producing ized runoff from theArea appears to pro- it appears that irriga- runoff. site.duce little or no run- tion is producing run-off. off.

*See Glossary.

Glossary

Approved disposal site: A site for land appli-cation of wastewater or tank pumpage thatmeets state standards of the Texas NaturalResource Conservation Commission(TNRCC).

Cesspool: Covered excavation in the groundthat receives sewage directly from a build-ing’s sanitary drainage system. It isdesigned to retain the organic matter andsolids and to permit liquid to seep into thesoil. Cesspools are not allowed for construc-tion and/or use in the state. They are con-sidered unsuitable on-site wastewater dis-posal methods.

Clear water infiltration: Entry of water thatdoes not need treatment into a treatmentsystem; clear water may enter through tiledrainage, unsealed joints, access ports andcracks.

Design capacity: Maximum volume of liquidthat can be treated in a particular waste-water treatment system. For systems thatinclude subsurface wastewater disposal anddistribution, capacity is also based on thesoil’s ability to accept and treat sewageeffluent. In filling out the worksheet, if youdo not know the design capacity of yoursystem, use 150 gallons per bedroom perday as an estimate.

Effluent: Liquid discharged from a septic tankor other sewage treatment tank.

Holding tank: An approved watertight recep-tacle for collecting and holding sewage.

Hydraulic loading rate: The volume of wastedischarged per unit area per unit time.

Off-site disposal: Disposal of wastewater orsludge at a municipal treatment plant orother approved disposal site.

Scum: Floatable solids, such as grease and fat.

Seepage pit (dry well): Underground recepta-cle constructed to permit disposal of septictank effluent, treated wastes or clear wastesby soil absorption through its bottom andwalls. Seepage pits are not allowed for con-struction and/or use in the state. They areconsidered unsuitable on-site wastewaterdisposal methods.

Sludge: Settleable, partially decomposed solidsresulting from biological, chemical or physi-cal wastewater treatment.

Contacts and References

For additional information, contact yourlocal county Extension agent, or:

★ The Texas Natural Resource ConservationCommission at (512) 239-1000,

★ Texas Agricultural Extension ServiceAgricultural Engineering unit (409) 845-7451,

★ Texas Agricultural Extension Service WaterQuality unit (409) 845-0887,

★ Texas State Soil and Water ConservationBoard, (817) 773-2250.

Internet address: TEX*A*Syst bulletins andlinks to other water quality sites are containedin a homepage located on the World Wide Webat: http://waterhome.tamu.edu.

TEX*A*Syst is a series of publications to help rural residents assess the risk of ground water pollution, and to describeBest Management Practices (BMPs) that can help protect ground water. The TEX*A*Syst documents were developedfrom the national Farm*A*Syst ground water protection program. The TEX*A*Syst system is designed to help the userlearn more about the environment, existing environmental policies and regulations, and recommended managementpractices. Thus, the user can voluntarily reduce the pollution risks associated with water wells.

TEX*A* Syst materials were edited by Anna Schuster Kantor, and reviewed by M.C. Dozier and the personnel of theUSDA-Natural Resources Conservation Service, U.S. Environmental Protection Agency, Texas Department ofAgriculture, Texas Natural Resource Conservation Commission, Texas Water Development Board, Texas State Soil andWater Conservation Board, Texas Water Resources Institute, and Texas Farm Bureau. Editorial and formatting assis-tance were provided by the Department of Agricultural Communications, The Texas A&M University System.

The TEX*A*Syst program is sponsored by the U.S. EnvironmentalProtection Agency under Section 319(h) of the Clean Water Act.Funds for this program are administered by the Texas State Soil andWater Conservation Board’s Agricultural/Silvicultural NonpointSource Management Program.

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