Secondary Treatment Configurations

Secondary Treatment Secondary Treatment ConfigurationsConfigurations

SOP Pretreatment WorkshopSOP Pretreatment Workshop

August 2011August 2011

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. CR827881-01-0) through a Cooperative Agreement (EPA No. CR827881-01-0) 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 Agency. not been reviewed by the U.S. Environmental Protection Agency. These materials have been reviewed by representatives of the These materials have been reviewed by representatives of the

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These 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 peer-reviewed and represent the current state of been peer-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 formulating series of writing and review meetings with the goal of formulating a consensus on the materials presented. These materials do not a consensus on the materials presented. These materials do not

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recommendation for use from these individuals or entities, nor recommendation for use from these individuals or entities, nor does it constitute criticism for similar ones not mentioned.does it constitute criticism for similar ones not mentioned.

Pretreatment componentsPretreatment components Section objectivesSection objectives

Describe various engineered systems that maintain Describe various engineered systems that maintain high-rate aerobic digestion of organic compounds high-rate aerobic digestion of organic compounds found in domestic wastewaterfound in domestic wastewater

Provide an understanding of the typical issues Provide an understanding of the typical issues associated with these componentsassociated with these components

Describe basic operation and maintenance Describe basic operation and maintenance procedures required to keep these systems functionalprocedures required to keep these systems functional

Basic aerobic treatment Basic aerobic treatment environmentsenvironments

SaturatedSaturated Suspended growthSuspended growth Fixed/attached growthFixed/attached growth Integrated fixed/activated sludge (IFAS)Integrated fixed/activated sludge (IFAS)

UnsaturatedUnsaturated Media filtersMedia filters Trickling filtersTrickling filters

Saturated treatmentSaturated treatment

Suspended growthSuspended growth Fixed/attached growthFixed/attached growth Integrated fixed/activated sludge (IFAS)Integrated fixed/activated sludge (IFAS)

Saturated aerobic units:Saturated aerobic units:Primary distinctionsPrimary distinctions

PackagingPackaging Flow of effluentFlow of effluent Aeration methodAeration method Biomass managementBiomass management

Suspended growth reactorsSuspended growth reactors

Activated sludge processActivated sludge process Biomass is thoroughly mixed with nutrients Biomass is thoroughly mixed with nutrients

and biodegradable compoundsand biodegradable compounds Organisms flocculate and form active Organisms flocculate and form active

mass of microbes - biological flocmass of microbes - biological floc Extended aeration to limit biomass wastingExtended aeration to limit biomass wasting

Endogenous respirationEndogenous respiration

Suspended Growth Suspended Growth

Suspended growthSuspended growth



USEPA Manual, 1980USEPA Manual, 1980

Sequencing Batch ReactorSequencing Batch Reactor

Suspended growth treatment processSuspended growth treatment process Utilize a Utilize a single chambersingle chamber for achieving aeration, for achieving aeration,

clarification and anoxic conditionsclarification and anoxic conditions Flow equalization chamber for dosing effluent into Flow equalization chamber for dosing effluent into

the treatment chamberthe treatment chamber

Sequencing batch reactorsSequencing batch reactors

Sequencing batch reactorsSequencing batch reactors

Fixed/attached growth reactorsFixed/attached growth reactors Fixed-film processFixed-film process Inert medium is submerged in the aeration Inert medium is submerged in the aeration

chamberchamber Effluent circulated through media and Effluent circulated through media and

attached microbesattached microbes Colloidal and dissolved organics Colloidal and dissolved organics

compounds absorbed by biological filmcompounds absorbed by biological film Extended aeration to limit biomass wastingExtended aeration to limit biomass wasting Food brought to bugsFood brought to bugs

Fixed-film reactorsFixed-film reactors

Rotating Biological Contactor Rotating Biological Contactor (RBC)(RBC)

Membrane bioreactorsMembrane bioreactors

Wikipedia

Flow schemesFlow schemes

Continuous inflowContinuous inflow Batch processesBatch processes

AerationAeration

Air supply and delivery componentAir supply and delivery component Distribution deviceDistribution device Venting deviceVenting device

Air supply deliveryAir supply delivery

MethodsMethods Aspirator/AeratorAspirator/Aerator CompressorCompressor BlowerBlower Free AirFree Air

Aerator/AspiratorAerator/Aspirator

Aerator/AspiratorAerator/Aspirator Spinning shaft or impeller creates a vacuum (venturi)Spinning shaft or impeller creates a vacuum (venturi) Vacuum pulls air into the waterVacuum pulls air into the water

CompressorCompressor Two distinct types of Two distinct types of

compressorscompressors RotaryRotary LinearLinear

Both types fitted with Both types fitted with filtersfilters

Relative to blowers:Relative to blowers: Greater pressure Greater pressure Lower air flowLower air flow

Rotary

Linear

BlowersBlowers Fitted with inlet Fitted with inlet

screens/filtersscreens/filters Relative to compressors:Relative to compressors:

Lower pressure Lower pressure Greater air flowGreater air flow

Air distribution deviceAir distribution device

Introduces air into the waterIntroduces air into the water Includes any supply line(s)Includes any supply line(s) Various methodsVarious methods

Aspirator/aeratorAspirator/aerator

Shaft piping delivers Shaft piping delivers the air supplythe air supply

Distribution relative Distribution relative to pressureto pressure

Diffused air distributionDiffused air distribution

Compressor or Compressor or blower delivers airblower delivers air

Mode of distribution Mode of distribution is manufacturer is manufacturer specificspecific Solid pipeSolid pipe Perforated pipePerforated pipe

• HolesHoles• SlotsSlots

Porous materialPorous material


Perforated Pipe


Porous ceramic diffuser

Diffused air distributionDiffused air distribution SpargersSpargers

small interconnected passageways inside a ceramic small interconnected passageways inside a ceramic matrixmatrix

Oxygen transfer into solutionOxygen transfer into solution

Small diameter Small diameter bubbles bubbles More surface area per More surface area per

unit volumeunit volume Oxygen transfer takes Oxygen transfer takes

place across interface place across interface between air and waterbetween air and water

Point of injectionPoint of injection Usually near Usually near

bottom of tankbottom of tank more time for oxygen more time for oxygen

to go into solutionto go into solution more hydrostatic more hydrostatic

pressure on bubblepressure on bubble more mixing of more mixing of

contentscontents

““Free” airFree” air

Alternately rotates media Alternately rotates media through air space in top through air space in top of unit and down into of unit and down into effluent in basineffluent in basin

Water accepts oxygen Water accepts oxygen from air from air

Aeration and MixingAeration and Mixing Aeration system Aeration system

also encouragesalso encourages

mixingmixing displacement of displacement of

water as air is water as air is introduced causes introduced causes turbulenceturbulence

Air supply operationAir supply operation

ContinuousContinuous TimedTimed

VentingVenting Air entering systemAir entering system Air must exit Air must exit

somewheresomewhere UnitUnit House ventHouse vent BiofilterBiofilter

Biomass managementBiomass management

Returning sludge to a previous point in Returning sludge to a previous point in treatment systemtreatment system

Keeps the biological processes workingKeeps the biological processes working

At some point, accumulated solids will At some point, accumulated solids will have to be removedhave to be removed

Passive sludge return systemPassive sludge return system

Settled material Settled material automatically returns automatically returns to the aeration to the aeration chamberchamber

No moving partsNo moving parts Limited flexibility for Limited flexibility for

including anoxic including anoxic treatment processtreatment process

Active sludge return systemActive sludge return system

Pump on bottom of Pump on bottom of settling chambersettling chamber

Control panel with timerControl panel with timer Timing of returnTiming of return Volume returnedVolume returned Location for returned Location for returned

materialmaterial

Proprietary configurationsProprietary configurations

Modular units with complete configurationModular units with complete configuration Subcomponents installed in prefab tanksSubcomponents installed in prefab tanks Specific to proprietary productsSpecific to proprietary products

Basic aerobic treatment Basic aerobic treatment environmentsenvironments

SaturatedSaturated Suspended growthSuspended growth Fixed/attached growthFixed/attached growth Integrated fixed/activated sludge (IFAS)Integrated fixed/activated sludge (IFAS)

UnsaturatedUnsaturated Media filtersMedia filters Trickling filtersTrickling filters

Unsaturated treatmentUnsaturated treatment

Media filtersMedia filters Trickling filtersTrickling filters

Media filtersMedia filters A container or lined A container or lined

excavation containing excavation containing a specific media a specific media through which through which wastewater flowswastewater flows

Treatment occurs in Treatment occurs in unsaturated conditionsunsaturated conditions

Designed to follow Designed to follow primary treatmentprimary treatment

Flow regimes for media filters Flow regimes for media filters

Single passSingle pass RecirculatingRecirculating

Single-pass media filterSingle-pass media filter

NSFC

Recirculating media filter schematicRecirculating media filter schematic

Septic Tank Recirculation Tank Final Effluent Tank

Recirculating Media Filter

From House To Soil

Filter Drainage

Effluent Filter Float Valve in Tank Effluent PumpDosing Pump

Typical configurationTypical configuration

24 – 36 inches of media24 – 36 inches of media Methods of distributionMethods of distribution

Pressure distribution - most common Pressure distribution - most common • Spray nozzlesSpray nozzles• DriplinesDriplines

GravityGravity

Increasingly, timer-controlled dosing is being usedIncreasingly, timer-controlled dosing is being used Usually lined to collect filtrate for external dispersalUsually lined to collect filtrate for external dispersal May be configured to drain into rock pad beneath May be configured to drain into rock pad beneath

unit in certain soil/site conditionsunit in certain soil/site conditions

Typical configurationTypical configuration

Single-pass: 1 – 2 gal / ftSingle-pass: 1 – 2 gal / ft2 2 /day/day Multiple-pass filters: up to 5 gal / ftMultiple-pass filters: up to 5 gal / ft2 2 /day/day Increased loadings may be allowed for Increased loadings may be allowed for

certain proprietary designscertain proprietary designs

Typical hydraulic loadingTypical hydraulic loading

Single-pass filters:Single-pass filters: Historically - 4 times/dayHistorically - 4 times/day Current recommendations - as high as 12-24 Current recommendations - as high as 12-24

times/daytimes/day Multiple-pass: 12-72+ times/dayMultiple-pass: 12-72+ times/day

Dosing frequencyDosing frequency

Treatment processTreatment process

Wastewater applied in small dosesWastewater applied in small doses Percolates over media in thin filmPercolates over media in thin film Organisms on media contact wastewaterOrganisms on media contact wastewater Air is maintained in media poresAir is maintained in media pores Oxygen is transferred into the thin film and Oxygen is transferred into the thin film and

to organismsto organisms Aeration typically passiveAeration typically passive

Treatment occurs by:Treatment occurs by:

Filtration and trappingFiltration and trapping AdsorptionAdsorption Biological decompositionBiological decomposition Biochemical transformationBiochemical transformation

NitrificationNitrification Denitrification (especially if recirculated) Denitrification (especially if recirculated)

Types of mediaTypes of media Washed, graded sandWashed, graded sand GravelGravel Foam chips and cubesFoam chips and cubes Expanded polystyreneExpanded polystyrene PeatPeat Synthetic textile materialsSynthetic textile materials Bottom ash from coal-fired plantsBottom ash from coal-fired plants Crushed glassCrushed glass OtherOther

Sand and gravel filtersSand and gravel filters

Single pass or recirculating modeSingle pass or recirculating mode Sand/Gravel media specificationsSand/Gravel media specifications

Must (generally) be processed to provide the right Must (generally) be processed to provide the right gradationgradation

Screened for proper gradationScreened for proper gradation WashedWashed

Must be handled carefully after processing to Must be handled carefully after processing to maintain the specification and remain free of maintain the specification and remain free of finesfines

Cutaway demoCutaway demo

Single pass sand filterSingle pass sand filterwith pump basinwith pump basin

Questions?Questions?

Documents

Secondary Treatment Configurations