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Household Wastewater Systems Mike Kizer OSU Extension Biosystems & Agricultural Engineering.

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Presentation on theme: "Household Wastewater Systems Mike Kizer OSU Extension Biosystems & Agricultural Engineering."— Presentation transcript:

1 Household Wastewater Systems Mike Kizer OSU Extension Biosystems & Agricultural Engineering

2 Typical Waste Water System Well Renovated Wastewater

3 Wastewater System Regulation Regulatory agency in Oklahoma is: Department of Environmental Quality (DEQ) 707 N. Robinson, OKC (Tel: )Regulatory agency in Oklahoma is: Department of Environmental Quality (DEQ) 707 N. Robinson, OKC (Tel: ) DEQ field offices in many counties Check local listing under: Oklahoma – State of –DEQ field offices in many counties Check local listing under: Oklahoma – State of – Regulations are outlined in Title 252 of Oklahoma Administrative Code, Ch. 641Regulations are outlined in Title 252 of Oklahoma Administrative Code, Ch. 641 DEQ wastewater system website: wastewater system website:

4 Minimum Lot Size for Wastewater Disposal Systems Disposal System Type Water Supply Source Private Well Public Supply Aerobic w/ sprinklers ¾ acre ½ acre ET/Absorption Trench 1 acre Subsurface (fast perc.) ¾ acre ½ acre Subsurface (slow perc.) 1 acre Lagoon 2 ½ acres

5 Wastewater System Separation Distances (distance in feet) Tanks (septic, pump, aeration) Perforated Pipe or Chamber Solid Pipe Lagoon Sprinkler Head Spray Head Private Well 50 / Public Well Buildings55NA50NANA Other Structure NA10NANANANA Water Line NA Property Line Stream/Lake1515NA Drains1515NA15NA15

6 Wastewater System Components Water-tight sewer linesWater-tight sewer lines Septic tankSeptic tank Disposal systemDisposal system –Subsurface drain field Absorption trenchesAbsorption trenches Infiltration chambersInfiltration chambers –ET/Absorption trenches –Aerobic system with sprinkler –Total retention lagoons –Pre-approved alternative disposal systems

7 Household Plumbing Sewer and Vent System Sewer lines in the house collect waste water for conveyance to the septic tankSewer lines in the house collect waste water for conveyance to the septic tank Roof vents and the traps under sinks, tubs, showers, toilets and wall/floor drains prevent sewer gas from entering the house.Roof vents and the traps under sinks, tubs, showers, toilets and wall/floor drains prevent sewer gas from entering the house. Screen vent pipe opening to prevent blockage by birds, squirrels, etc. Main Sewer Pipe

8 Septic Tank All household wastewater systems will have a septic tankAll household wastewater systems will have a septic tank Microbial action digests solid wastesMicrobial action digests solid wastes Liquids flow through tank to disposal areaLiquids flow through tank to disposal area Tank sizeTank size –1000 gallon liquid capacity (4-BR house or less) –Add 250 gallons per additional bedroom

9 House Foundation Typical Septic Tank Installation Two-Chamber Tank Baffles

10 Wastewater Piping Materials Water-tight Sewer Conveyance LinesWater-tight Sewer Conveyance Lines –Cast iron –PVC (Sch. 40 is preferred weight) –Transite (asbestos-cement) –Orangeburg (paper-tar product: old houses) Drain Field LinesDrain Field Lines –Perforated PVC –Polyethylene infiltration chambers –Clay tile (old houses)

11 Effluent Disposal Area Options Absorption fieldAbsorption field –Absorption trenches –Infiltration chambers –ET/Absorption trenches LagoonsLagoons Aerobic systemsAerobic systems Authorized alternative systemsAuthorized alternative systems

12 Subsurface Absorption Field Approval Percolation TestPercolation Test –3 test holes in drainage area perc at a rate of 60 min/inch of water or faster Soil Profile DescriptionSoil Profile Description –3 test holes without any of the following: (1) impervious material (bedrock, clay pan) (1) impervious material (bedrock, clay pan) (2) water saturated soil (discoloration) (2) water saturated soil (discoloration) (3) loamy coarse sand or coarser soil, or (3) loamy coarse sand or coarser soil, or (4) sandy clay or finer soil (4) sandy clay or finer soil

13 The size and type of waste water disposal system is very dependent on the soil at the building site. Even before a percolation test or soil profile evaluation you can get an idea of site suitability from the county soil survey.

14 Cross-Section of Subsurface Absorption Trench Perforated Pipe 8-ft minimum distance to center of next trench

15 150’ MAX.

16 Lateral lines following the slope contour 150’ max. length

17 Infiltration Chambers Polyethylene infiltration chamber has 100% open volume vs. 50% for gravel- filled absorption trench Polyethylene infiltration chamber has 100% open volume vs. 50% for gravel- filled absorption trench Corrugated design gives strength to support ground traffic over its 2-ft width Corrugated design gives strength to support ground traffic over its 2-ft width Chamber cost per unit length is approximately equal to unit cost of perforated PVC pipe, plus gravel and installation Chamber cost per unit length is approximately equal to unit cost of perforated PVC pipe, plus gravel and installation

18 ET/Absorption Trench System Used when soil percolation rate is too slow for ordinary subsurface absorption trenchesUsed when soil percolation rate is too slow for ordinary subsurface absorption trenches Uses evapotranspiration (ET) of grasses plus soil absorption to dispose wastewaterUses evapotranspiration (ET) of grasses plus soil absorption to dispose wastewater Plant a mix of cool and warm season grasses for year-round ETPlant a mix of cool and warm season grasses for year-round ET

19 Cross-Section of ET/Absorption Trench Cool-Warm Season Grass Mixture Perforated Pipe

20 Lagoons Used when soil percolation rate is too slow for soil absorption systemsUsed when soil percolation rate is too slow for soil absorption systems Require 2 ½ acre minimum lot sizeRequire 2 ½ acre minimum lot size Fencing required around the lagoonFencing required around the lagoon Size based on house size, and rainfall and evaporation of geographic zoneSize based on house size, and rainfall and evaporation of geographic zone Must retain all wastewater (no overflow)Must retain all wastewater (no overflow)

21 3 1 Typical Lagoon Installation 5 ft max. 7 ft 4 ft Concrete Pad 1 ft min acre minimum lot size required - 4-ft high fence required - lagoon size based on house size and local rainfall

22 Location & Lagoon Size The required size of total retention waste water lagoons (because of their annual hydraulic balance) makes them less desirable the farther east you build in Oklahoma.

23 Aerobic Systems Used to treat septic tank effluent where subsurface disposal is not possibleUsed to treat septic tank effluent where subsurface disposal is not possible Bubbling air through effluent supports aerobic bacteria for further digestionBubbling air through effluent supports aerobic bacteria for further digestion Exposure to oxygen kills most pathogensExposure to oxygen kills most pathogens Chlorination allows surface land application of wastewater through sprinklersChlorination allows surface land application of wastewater through sprinklers

24 (Septic Tank) Onsite Aerobic Treatment System Onsite aerobic treatment systems treat septic tank effluent further by aerobic digestion, chlorination to kill pathogens, and surface application through a spray head sprinkler system.

25 Typical Aeration Chamber of Aerobic Treatment System DIFFUSER EFFLUENT FROM SEPTIC TANK WASTEWATER TO CHLORINATOR & SPRINKLERS

26 Stack-Feed Contact Tablet Chlorinator Chlorine Tablet Feed Tubes Ca(OCl) 2 Tablets Effluent Inlet Effluent Outlet

27 Pump Chamber and Surface Application System Pump Pump Control & Alarm Floats Access Hatch Spray Heads

28 Finding Waste Water System Components Waste water components are normally downhill from the house (gravity flow)Waste water components are normally downhill from the house (gravity flow) Septic tank can be no less than 5 feet, and is normally no more than 50 feet from houseSeptic tank can be no less than 5 feet, and is normally no more than 50 feet from house Two-way sanitary sewer clean-outs located:Two-way sanitary sewer clean-outs located: –Within 5 feet of the house –Within 5 feet of every bend greater than 45º –Every 100 feet of straight sewer line Grass over septic tank may be brown in summerGrass over septic tank may be brown in summer Grass over drain field will be greener in summerGrass over drain field will be greener in summer

29 Clean-outs on main sewer line Locating Waste Water System Components

30 Sewer system roof vents 4-inch roof vent on main sewer line 2 1/2 -inch roof vent on branch line Locating Waste Water System Components

31 Largest roof vent on main sewer line Clean-outs on main sewer line exiting house Locating Waste Water System Components

32 Regular green stripes in a dry lawn are the lateral lines

33 Household Water Use Typical Usage: gallons/person-dayTypical Usage: gallons/person-day –Clothes washer: gallons/load –Dishwasher: 7-15 gallons/load –Garbage Disposal: gallons/day –Shower/Bathtub: gallons/use –Ordinary toilet: gallons/flush –Water softener: gallons/regeneration

34 Septic System Additives Biological BacteriaBacteria YeastYeast EnzymesEnzymes CombinationCombinationChemical AcidsAcids BasesBases Organic SolventsOrganic Solvents FlocculantsFlocculants

35 Biological Additives Will not eliminate need for tank pumpingWill not eliminate need for tank pumping 20% of sludge is inorganic (indigestible)20% of sludge is inorganic (indigestible) Billions of bacteria live in septic tanks-- a few million more have little effectBillions of bacteria live in septic tanks-- a few million more have little effect If natural bacteria have been killed, added bacteria will die alsoIf natural bacteria have been killed, added bacteria will die also Normal population is restored in hours even if 99.99% has been killedNormal population is restored in hours even if 99.99% has been killed

36 Maximum Safe Levels of Cleaners (Single dose in 1000-gallon septic tank) Bleach (5.25% Cl): 1.3 gallonsBleach (5.25% Cl): 1.3 gallons Cleansers/Disinfectants:2.5 gallonsCleansers/Disinfectants:2.5 gallons Drain Cleaners:0.65 ouncesDrain Cleaners:0.65 ounces

37 Chemical Additives Strong Acids and Bases Disrupt normal tank biological activityDisrupt normal tank biological activity Harm soil structure in drain fieldHarm soil structure in drain field Organic Solvents Clean thin layers of sewer line build-upClean thin layers of sewer line build-up Contaminate ground waterContaminate ground water

38 Annual Cost of Additives Amherst, MA Retailers Study (using manufacturer’s recommended rates) Biological (11):$19.75/yrBiological (11):$19.75/yr Solvents (3):$78.00/yrSolvents (3):$78.00/yr Acid/Base (8):$13.48/yrAcid/Base (8):$13.48/yr

39 Annualized Pumping Cost (USPHS Pumping Frequency Estimate) $150 Pumping Cost for 1000-gal tank Family SizePumping Freq.Annual Cost 2 20 yrs $ 7.50/yr 3 12 yrs $12.50/yr 4 8 yrs 8 yrs$18.75/yr 5 6 yrs 6 yrs$25.00/yr 6 4 yrs 4 yrs$37.50/yr

40 Septic System Additives Conclusions Biological additives are harmless but of little useBiological additives are harmless but of little use Chemical additives can damage septic system and contaminate ground waterChemical additives can damage septic system and contaminate ground water Don’t use if active ingredients are unspecifiedDon’t use if active ingredients are unspecified Annualized cost of additives is about the same as for tank pumping on recommended scheduleAnnualized cost of additives is about the same as for tank pumping on recommended schedule “These products make a lot of money for the people that sell them.”“These products make a lot of money for the people that sell them.”

41 Waste Water System Failures Common Causes Hydraulic overloading (too much water)Hydraulic overloading (too much water) Solids migration to drain fieldSolids migration to drain field –Failure to pump tank on schedule –Baffle failure Root intrusion into sewer linesRoot intrusion into sewer lines Traffic damage to drain fieldTraffic damage to drain field Garbage disposal overuseGarbage disposal overuse

42 Reducing Hydraulic Loading Equipment AdjustmentsEquipment Adjustments –Low flow toilets (1.6 gpf and 0.6 gpf) –Water-saving showerheads –Front-loading washing machines Lifestyle AdjustmentsLifestyle Adjustments –Shower vs. bath –Distribute laundry loads throughout week –Distribute bathing morning & evening –Full loads only for washer & dishwasher

43 Root Damage Plant no trees or shrubs near sewer linesPlant no trees or shrubs near sewer lines Copper sulfate to kill tree/shrub rootsCopper sulfate to kill tree/shrub roots –Treatment is not toxic to plants –Once intruding roots are killed, absorption ends –Add ½ cup of crystals to distribution box or to cleanout downstream from septic tank –If added through toilet, 2 pounds of crystals are needed (not harmful to tank bacteria) See OSU CR-6428 for more informationSee OSU CR-6428 for more information

44 Traffic Damage No vehicle parking over drain fieldNo vehicle parking over drain field No vehicle traffic except lawn mowersNo vehicle traffic except lawn mowers No traffic at all if ground is saturatedNo traffic at all if ground is saturated

45 Solids & Drain Fields Solids must be retained in septic tankSolids must be retained in septic tank Baffles should be inspected when tank is inspected or pumpedBaffles should be inspected when tank is inspected or pumped Use of additives that “liquefy” sludge and scum can lead drain field failureUse of additives that “liquefy” sludge and scum can lead drain field failure Septic tanks: like fuses in electrical wiring (failure in controlled location; cheap to fix)Septic tanks: like fuses in electrical wiring (failure in controlled location; cheap to fix)

46 Garbage Disposals Add to hydraulic load (running water)Add to hydraulic load (running water) Add to solids (more frequent pumping)Add to solids (more frequent pumping) Poorer digestion environmentPoorer digestion environment –(Carbon:Nitrogen ratio is more unfavorable)

47 Water Softeners & Septic Systems Salt does not affect septic tank functioningSalt does not affect septic tank functioning Added hydraulic load (regeneration water)Added hydraulic load (regeneration water) –Use water meter or sensor controlled regeneration rather than time clock alone Added sodium can affect marginal drain fields (dispersal of clays slows perc rate)Added sodium can affect marginal drain fields (dispersal of clays slows perc rate) –Use potassium chloride (KCl) salt if a problem

48 On-Site Wastewater System Resources MWPS-24 Home*A*Syst OK DEQ Ch. 641 Onsite Domestic SewageWorksheet #3 Disposal Handbook

49 If you don’t maintain your on-site wastewater system, it will demand your attention when it is most inconvenient.


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