Conventional Onsite Wastewater Conventional Onsite Wastewater Treatment Systems, Alternative Treatment Systems, Alternative
DrainfieldsDrainfields, and Distribution , and Distribution MethodsMethods
This presentation has been modified from This presentation has been modified from the following “Alternative Onsite the following “Alternative Onsite Wastewater Treatment Technologies” Wastewater Treatment Technologies” developed by the National Decentralized developed by the National Decentralized Water Resources Capacity Development Water Resources Capacity Development Project.Project.
NDWRCDP DisclaimerNDWRCDP DisclaimerThis work was supported by the National Decentralized Water This work was supported by the National Decentralized Water Resources Capacity Development Project (NDWRCDP) with Resources Capacity Development Project (NDWRCDP) with
funding provided by the U.S. Environmental Protection Agency funding provided by the U.S. Environmental Protection Agency through a Cooperative Agreement (EPA No. CR827881through a Cooperative Agreement (EPA No. CR827881--0101--0) 0) with Washington University in St. Louis. These materials have with Washington University in St. Louis. These materials have
not been reviewed by the U.S. Environmental Protection not been reviewed by the U.S. Environmental Protection Agency. These materials have been reviewed by Agency. These materials have been reviewed by representatives of the NDWRCDP. The contents representatives of the NDWRCDP. The contents
of these materials do not necessarily reflect the views and of these materials do not necessarily reflect the views and policies of the NDWRCDP, Washington University, or the U.S. policies of the NDWRCDP, Washington University, or the U.S.
Environmental Protection Agency, nor does the mention of trade Environmental Protection Agency, nor does the mention of trade names or commercial products constitute their endorsement or names or commercial products constitute their endorsement or
recommendation for use.recommendation for use.
CIDWT/University DisclaimerCIDWT/University DisclaimerThese materials are the collective effort of individuals from These materials are the collective effort of individuals from
academic, regulatory, and private sectors of the academic, regulatory, and private sectors of the onsite/decentralized wastewater industry. These materials have onsite/decentralized wastewater industry. These materials have
been peerbeen peer--reviewed and represent the current state of reviewed and represent the current state of knowledge/science in this field. They were developed through a knowledge/science in this field. They were developed through a
series of writing and review meetings with the goal of series of writing and review meetings with the goal of formulating a consensus on the materials presented. These formulating a consensus on the materials presented. These materials do not necessarily reflect the views and policies of materials do not necessarily reflect the views and policies of
North Carolina State University, and/or the Consortium of North Carolina State University, and/or the Consortium of Institutes for Decentralized Wastewater Treatment (CIDWT). Institutes for Decentralized Wastewater Treatment (CIDWT).
The mention of trade names or commercial products does not The mention of trade names or commercial products does not constitute an endorsement or recommendation for use from constitute an endorsement or recommendation for use from
these individuals or entities, nor does it constitute criticism these individuals or entities, nor does it constitute criticism for for similar ones not mentioned.similar ones not mentioned.
CitationCitationLenning, D., T. Banathy, D. Gustafson, B.J. Lenning, D., T. Banathy, D. Gustafson, B.J.
Lesikar, S. Wecker, D. Wright. 2005. Technology Lesikar, S. Wecker, D. Wright. 2005. Technology Overview Overview –– PowerPoint Presentation. PowerPoint Presentation. inin (D.L. (D.L. Lindbo and N.E. Deal eds.) Model Decentralized Lindbo and N.E. Deal eds.) Model Decentralized Wastewater Practitioner Curriculum. National Wastewater Practitioner Curriculum. National Decentralized Water Resources Capacity Decentralized Water Resources Capacity Development Project. North Carolina State Development Project. North Carolina State University, Raleigh, NC.University, Raleigh, NC.
ObjectivesObjectivesLearn about the followingLearn about the following
The conventional onsite wastewater treatment The conventional onsite wastewater treatment systemsystem•• Septic tankSeptic tank•• Gravel Gravel drainfielddrainfield
How the different components in the How the different components in the conventional system workconventional system workAlternatives to the gravel Alternatives to the gravel drainfielddrainfieldDifferent methods for distribution of effluent in Different methods for distribution of effluent in the the drainfielddrainfield
Treatment ProcessesTreatment ProcessesVariety of physical, chemical and Variety of physical, chemical and biological processes including:biological processes including:◘◘ FiltrationFiltration ◘◘ AdsorptionAdsorption◘◘ SedimentationSedimentation ◘◘ IonIon--exchangeexchange
◘◘ AerationAeration ◘◘ AnaerobicAnaerobic
◘◘ FlotationFlotation ◘◘ PredationPredation
◘◘ InactivationInactivation ◘◘ DisinfectionDisinfection
Pretreatment OptionsPretreatment Options
Traditionally, have been categorized as:Traditionally, have been categorized as:PrimaryPrimary –– solids removalsolids removalSecondarySecondary –– organics and BOD removalorganics and BOD removalTertiaryTertiary –– nutrient removalnutrient removal
Bacteria classified in one of the following Bacteria classified in one of the following three categoriesthree categories
Aerobic Aerobic AnaerobicAnaerobicFacultativeFacultative
Pretreatment OptionsPretreatment Options
Septic tankSeptic tankGrease Traps and InterceptorsGrease Traps and InterceptorsAerobic Treatment Unit (ATU)Aerobic Treatment Unit (ATU)Media FiltersMedia FiltersConstructed WetlandsConstructed WetlandsDisinfectionDisinfectionOther Other –– Lagoons, AnaerobicLagoons, Anaerobic upflowupflow filtersfilters
Septic TankSeptic Tank
What is it?What is it?
Septic TankSeptic Tank
Solids settle to bottom, retained by baffleFats and grease float to top (scum)Wastewater exits through effluent filter
Septic TankSeptic Tank
Design considerationsDesign considerationsRisersRisers•• Required for pump tanksRequired for pump tanks•• Can be required for septic tanksCan be required for septic tanks
Septic TankSeptic Tank
Effluent screenEffluent screenFunctions:Functions:•• Help keep solids in tankHelp keep solids in tank
Septic TankSeptic Tank
Installation considerationsInstallation considerationsLevelLevelFlows from inlet to outlet (2Flows from inlet to outlet (2--inch difference)inch difference)Effluent filterEffluent filterRisersRisersCastCast--inin--place bootplace bootWatertightnessWatertightness testtest
Subsurface DisposalSubsurface Disposal
Subsurface DisposalSubsurface Disposal
Subsurface disposalSubsurface disposalEffluent is disposed of beneath the ground Effluent is disposed of beneath the ground surfacesurfaceThe soil can provide additional treatmentThe soil can provide additional treatmentUsually the trench bottom is installed three Usually the trench bottom is installed three feet below ground surfacefeet below ground surfaceCan be shallower or deeper under certain Can be shallower or deeper under certain conditionsconditions
Subsurface Disposal OptionsSubsurface Disposal Options
Conventional gravel trenchConventional gravel trenchShallow systemsShallow systemsGravellessGravelless trenchestrenchesPrefabricated permeable block panel systemPrefabricated permeable block panel systemSaprolite Saprolite systems (which will be discussed at a systems (which will be discussed at a future time)future time)Low pressure pipe (LPP)Low pressure pipe (LPP)Fill systemsFill systemsDrip irrigationDrip irrigation
Subsurface Disposal OptionsSubsurface Disposal Options
Conventional gravel Conventional gravel trench and shallow trench and shallow systemssystems
The main difference is the The main difference is the depth of installation for the depth of installation for the trench bottom, trench bottom, conventional systems have conventional systems have a trench bottom depth at 36 a trench bottom depth at 36 inches while shallow inches while shallow systems can be installed at systems can be installed at depths of 24 inches or lessdepths of 24 inches or less
Subsurface Disposal OptionsSubsurface Disposal Options
GravellessGravelless trenchestrenchesThere are three main types of There are three main types of gravelless gravelless trenches trenches used in North Carolinaused in North Carolina
•• ChamberChamber•• Large diameter pipeLarge diameter pipe•• NonNon--gravel trenches (use a different media in gravel trenches (use a different media in
place of gravel)place of gravel)
Subsurface Disposal OptionsSubsurface Disposal Options
Gravelless Gravelless trenchestrenchesChamber systems are Chamber systems are made of plastic, open made of plastic, open to the bottom and to the bottom and have louvers or have louvers or openings in the sides openings in the sides for effluent movementfor effluent movement
Subsurface Disposal OptionsSubsurface Disposal Options
GravellessGravelless trenchestrenchesLarge diameter pipe consists of eight or ten Large diameter pipe consists of eight or ten inch corrugated polyethylene tubing encased inch corrugated polyethylene tubing encased in a synthetic filter fabricin a synthetic filter fabric
Subsurface Disposal OptionsSubsurface Disposal Options
GravellessGravelless trenchestrenchesNonNon--gravel media which is used as a gravel media which is used as a substitute for gravel in the trenchsubstitute for gravel in the trenchAn example is provided belowAn example is provided below
Subsurface Disposal OptionsSubsurface Disposal Options
Prefabricated permeable block panel Prefabricated permeable block panel systemsystem
42”
12” + 6” + 16” + 6” = 42”
12”
6”
6”
16”
Subsurface Disposal OptionsSubsurface Disposal Options
Low pressure pipe systemsLow pressure pipe systemsShallow dosed soil absorption systemShallow dosed soil absorption systemPump forces effluent through the distribution Pump forces effluent through the distribution lines under pressurelines under pressureEffluent will be evenly dosed over entire Effluent will be evenly dosed over entire drainfield drainfield areaarea
Subsurface Disposal OptionsSubsurface Disposal Options
Low pressure pipe systemsLow pressure pipe systems
Subsurface Disposal OptionsSubsurface Disposal Options
Low pressure pipe systemsLow pressure pipe systems
Subsurface Disposal OptionsSubsurface Disposal Options
Fill systemsFill systemsA system in which all or part of the trenches A system in which all or part of the trenches are installed in fill, either new file or existing are installed in fill, either new file or existing file.file.The requirements for fill systems are found in The requirements for fill systems are found in Rule .1957(b).Rule .1957(b).
Subsurface Disposal OptionsSubsurface Disposal Options
Drip irrigationDrip irrigation
NSFC
Subsurface Disposal OptionsSubsurface Disposal Options
Drip irrigationDrip irrigation
Subsurface Disposal MethodsSubsurface Disposal Methods
Subsurface Disposal MethodsSubsurface Disposal Methods
Effluent can be disposed of beneath the Effluent can be disposed of beneath the ground surface by two different methodsground surface by two different methods
Gravity distribution Gravity distribution -- which includes parallel which includes parallel and serial distributionand serial distributionPressure distribution Pressure distribution -- which includes which includes pressure manifold, LPP, drip irrigation, and pressure manifold, LPP, drip irrigation, and siphonssiphons
Gravity DistributionGravity Distribution
Gravity distributionGravity distributionEffluent flows out of one component into the next Effluent flows out of one component into the next downstream component and on to downstream component and on to drainfielddrainfield by by gravitygravityInlet of downstream component must be at a lower Inlet of downstream component must be at a lower elevation than the outlet of the upstream componentelevation than the outlet of the upstream componentFlow dependent on when and how much flow occurs Flow dependent on when and how much flow occurs at the sourceat the sourceDistribution considered to be nonDistribution considered to be non--uniform over the uniform over the drainfielddrainfieldIt is the simplest and least expensive means of It is the simplest and least expensive means of distributiondistribution
Gravity DistributionGravity Distribution
Parallel DistributionParallel DistributionIn parallel distribution, effluent is distributed to In parallel distribution, effluent is distributed to all trenches in theall trenches in the drainfielddrainfield at the same timeat the same time
Gravity DistributionGravity Distribution
Parallel DistributionParallel DistributionA distribution box, tee, A distribution box, tee, wyewye, or header can be , or header can be used to split the flow among the linesused to split the flow among the lines
Gravity DistributionGravity Distribution
Serial DistributionSerial DistributionIn serial distribution, In serial distribution, effluent is discharged effluent is discharged to the first trench in the to the first trench in the systemsystemWhen that trench is full When that trench is full (reaches saturation) (reaches saturation) the effluent overflows the effluent overflows from the first trench to from the first trench to the second trenchthe second trench
Gravity DistributionGravity Distribution
Serial DistributionSerial Distribution
University of MinnesotaUniversity of Minnesota
Pressure DistributionPressure Distribution
Pressure DistributionPressure DistributionPredetermined volumes of effluent are held in a Predetermined volumes of effluent are held in a chamber and dosed to the next componentchamber and dosed to the next componentThis provides:This provides:
•• More uniform loading to next componentMore uniform loading to next component•• Resting times between dosesResting times between doses
Costs more and is more complex than gravity flowCosts more and is more complex than gravity flowOnOn--going monitoring & maintenance are importantgoing monitoring & maintenance are importantAlarms are required Alarms are required
Pressure DistributionPressure Distribution
Two types of pressure distributionTwo types of pressure distributionDemand dosingDemand dosingTime dosingTime dosing
Pressure DistributionPressure DistributionDemand DosingDemand Dosing
Dose occurs when sufficient volume of Dose occurs when sufficient volume of effluent has been collected.effluent has been collected.Dosing frequency depends on how much Dosing frequency depends on how much wastewater is being generated.wastewater is being generated.There is no control on how much effluent There is no control on how much effluent is being dosed daily.is being dosed daily.
Pressure DistributionPressure DistributionDemand DosingDemand Dosing
Pump on and off controlled directly by Pump on and off controlled directly by floatsfloats
Pressure DistributionPressure DistributionTime DosingTime Dosing
Timer controls number of doses per day and Timer controls number of doses per day and dose volumedose volumeWill allow only certain amount of effluent to be Will allow only certain amount of effluent to be dosed dailydosed dailyProtects downstream components from Protects downstream components from overloadingoverloadingUseful for controlling surges or bigUseful for controlling surges or big--flow daysflow days
Pressure DistributionPressure Distribution
Time DosingTime DosingA timer controls the dosing device.A timer controls the dosing device.
Pressure DistributionPressure Distribution
Pressure ManifoldPressure ManifoldPressurized manifold results in equal amounts Pressurized manifold results in equal amounts of effluent discharging to each receiving pipeof effluent discharging to each receiving pipeUsually discharges to gravityUsually discharges to gravity drainfielddrainfield, , though version of this can go to pressurizedthough version of this can go to pressurizeddrainfielddrainfieldValves may be placed on each outlet pipe Valves may be placed on each outlet pipe allowing resting or repairingallowing resting or repairing
Pressure DistributionPressure Distribution
Pressure ManifoldPressure Manifold
Pressure DistributionPressure DistributionSiphonSiphon
Passive device, part of a demand systemPassive device, part of a demand systemPower is not requiredPower is not requiredProper installation is criticalProper installation is criticalRegular operation and maintenance is Regular operation and maintenance is neededneeded
