Media FiltersMedia Filters

Ted L. LoudonTed L. LoudonMichigan State UniversityMichigan State University

Terry R. BoundsTerry R. BoundsVice President, Orenco Systems CompanyVice President, Orenco Systems Company

James C. Converse, Professor James C. Converse, Professor University of Wisconsin, MadisonUniversity of Wisconsin, Madison

John R. Buchanan John R. Buchanan University of Tennessee, KnoxvilleUniversity of Tennessee, Knoxville

University Curriculum Development University Curriculum Development for Decentralized Wastewater for Decentralized Wastewater

ManagementManagement

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 formulatiseries of writing and review meetings with the goal of formulating ng a consensus on the materials presented. These materials do not a consensus on the materials presented. These materials do not

necessarily reflect the views and policies of University of necessarily reflect the views and policies of University of Arkansas, and/or the Consortium of Institutes for Decentralized Arkansas, and/or the Consortium of Institutes for Decentralized

Wastewater Treatment (CIDWT). The mention of trade names or Wastewater Treatment (CIDWT). The mention of trade names or commercial products does not constitute an endorsement or commercial products does not constitute an endorsement or

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.

CitationCitation

Loudon, T.L., T.R. Bounds, J.R. Buchanan and J. Loudon, T.L., T.R. Bounds, J.R. Buchanan and J. C. Converse. 2005. Media Filters C. Converse. 2005. Media Filters -- PowerPoint PowerPoint Presentation. Presentation. inin (M.A. Gross and N.E. Deal, (M.A. Gross and N.E. Deal, eds.) University Curriculum Development for eds.) University Curriculum Development for Decentralized Wastewater Management. Decentralized Wastewater Management. National Decentralized Water Resources National Decentralized Water Resources Capacity Development Project. University of Capacity Development Project. University of Arkansas, Fayetteville, AR.Arkansas, Fayetteville, AR.

Media FiltersMedia FiltersIntroductionIntroduction

Media Filters (PBF) are secondary Media Filters (PBF) are secondary treatment unitstreatment unitsDesigned to follow primary treatment in a Designed to follow primary treatment in a septic tankseptic tankPBF’s are fixed film treatment systemsPBF’s are fixed film treatment systemsA passive aerobic systemA passive aerobic systemOne example is a sand filterOne example is a sand filterThe basic assumption in this module is The basic assumption in this module is that MF effluent goes to soil dispersalthat MF effluent goes to soil dispersal

MF Treatment ProcessMF Treatment Process

Wastewater applied in small dosesWastewater applied in small dosesPercolates over media in thin filmPercolates over media in thin filmOrganisms on media contact wastewaterOrganisms on media contact wastewaterAir is maintained in media poresAir is maintained in media poresOxygen is transferred into the thin film and Oxygen is transferred into the thin film and to organismsto organismsAeration may be active or passiveAeration may be active or passive

Fixed Film TreatmentFixed Film TreatmentP RO CE SS E S A T W O R K

M E D IA

B IO L O G IC A LM A S S

LI Q U I D W A S T E S

O R G A N IC S

E N D PR O D U C T S

A IR

P A T HO G E N S

E X CE SSCE L L M A SS

B.O .D .SS

N U TR IE N T S

Theory of operationTheory of operation

Organisms are “fixed” on the surfaces of Organisms are “fixed” on the surfaces of mediamediaWW effluent is “microWW effluent is “micro--dosed” to the filterdosed” to the filterWW is treated as it moves over media WW is treated as it moves over media surfaces in contact with organismssurfaces in contact with organisms

Modes of TreatmentModes of Treatment

Filtration and trappingFiltration and trappingAdsorptionAdsorptionBiological decompositionBiological decompositionBiochemical transformation Biochemical transformation

Typical Concentrations of Effluent from Septic Tanks Typical Concentrations of Effluent from Septic Tanks and and MF’sMF’s

BODBODMg/LMg/L

TSSTSSmg/Lmg/L

NitrateNitrate--NN

mg/Lmg/L

AmmoniaAmmonia--NN

mg/Lmg/L

D.O.D.O.mg/mg/LL

Fecal Fecal ColiformColiform

Org./100 mlOrg./100 ml

Septic Septic TankTank

130 130 --250250

30 30 --130130

0 0 -- 22 2525-- 6060 <2<2 101055 –– 101077

MF MF 55--2525 55--3030 1515--3030 00--44 33--55 101022 -- 101044

Media Filter EffluentMedia Filter Effluentin comparison to septic tank in comparison to septic tank

effluenteffluentLow in Oxygen demand (BOD5) Low in Oxygen demand (BOD5) ---- >90% >90% removed removed Low in total solids (TSS) and volatile solids Low in total solids (TSS) and volatile solids (VSS) (VSS) ---- > 90% removed> 90% removedWill not form a significant biological clogging mat Will not form a significant biological clogging mat in soilsin soilsLow in pathogens Low in pathogens ---- > 99% removed> 99% removedSignificantly reduced Total Nitrogen Significantly reduced Total Nitrogen

Typical removal range is 40Typical removal range is 40--60% removed60% removedUp to 80% removal with certain process designsUp to 80% removal with certain process designs

Uses of Media FiltersUses of Media FiltersEnvironmentally sensitive areasEnvironmentally sensitive areasSoils that are not acceptable for septic Soils that are not acceptable for septic tank effluenttank effluent

Hydraulically slowHydraulically slowInadequate vertical separationInadequate vertical separation

Systems with large flowsSystems with large flowsTo mitigate impact of subsurface dispersalTo mitigate impact of subsurface dispersalAllow a higher application rate to soilsAllow a higher application rate to soilsWhere irrigation of effluent is desiredWhere irrigation of effluent is desired

Benefits of Media FiltersBenefits of Media FiltersReduce organic matter, pathogens, some nutrientsReduce organic matter, pathogens, some nutrients

Produce an effluent that:Produce an effluent that:ReduceReduce biomatbiomat in soil absorption systems when applied at in soil absorption systems when applied at reasonable ratesreasonable rates

Can be subjected to tertiary treatment, if needed, and surface Can be subjected to tertiary treatment, if needed, and surface dischargeddischarged

•• Further nutrient removalFurther nutrient removal

•• DisinfectionDisinfection

Can be further treated rapidly in soilCan be further treated rapidly in soil

Can be applied to a wider range of soils than septic effluentCan be applied to a wider range of soils than septic effluent

Can be applied to soil at higher loading ratesCan be applied to soil at higher loading rates

Two Major Categories of MF Two Major Categories of MF

Single PassSingle PassRecirculatingRecirculating

Media TypesMedia Types

Natural and mineral mediaNatural and mineral mediaSand and gravelSand and gravelExpanded shaleExpanded shaleCindersCindersLimestoneLimestoneActivated carbonActivated carbonPeat or peat fiberPeat or peat fiber

Manufactured Media TypesManufactured Media Types

Textile fabricTextile fabricOpen cell foam cubesOpen cell foam cubesHard plasticHard plasticCrushed recycled glassCrushed recycled glassChipped recycled tiresChipped recycled tiresProcessed slagProcessed slag

Sand and Gravel FiltersSand and Gravel FiltersMay be designed and constructed to operate in May be designed and constructed to operate in either single pass or recirculating modeeither single pass or recirculating modeSand/Gravel media must meet a specific Sand/Gravel media must meet a specific specificationspecificationMust (generally) be processed to provide the Must (generally) be processed to provide the right gradationright gradation

Sometimes crushedSometimes crushedScreened for proper gradationScreened for proper gradationWashedWashed

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

Biological ProcessesBiological ProcessesBiofilmBiofilm forms on sand grainsforms on sand grains

Oxygen around the film promotes aerobic Oxygen around the film promotes aerobic activityactivity

Many species are present at all timesMany species are present at all times

Most are in the upper 12 inchesMost are in the upper 12 inches

Insufficient food and oxygen limit aerobic Insufficient food and oxygen limit aerobic organisms in lower layersorganisms in lower layers

Most BOD removal occurs in the top few inchesMost BOD removal occurs in the top few inches

Organic matter is consumed by microbes in the Organic matter is consumed by microbes in the biofilmbiofilm

Important Biological Design Important Biological Design ParametersParameters

Choice of mediaChoice of mediaSurface areaSurface areaVoid spaceVoid space

Provision for aerationProvision for aerationActive Active PassivePassive

Small doses of wastewater applied uniformlySmall doses of wastewater applied uniformlyKeeps flow in the biofilm Keeps flow in the biofilm –– i.e. unsaturated flowi.e. unsaturated flowProvides residence time in thin films on surfacesProvides residence time in thin films on surfacesPrevents displacing air from voidsPrevents displacing air from voids

More on Biological ProcessesMore on Biological ProcessesNitrogen removal is a biological processNitrogen removal is a biological process

Nitrifying bacteria convert ammoniumNitrifying bacteria convert ammonium--N (NHN (NH44)and )and organicorganic--N to nitrateN to nitrate--N (NON (NO33))

Most conversion to NOMost conversion to NO3 3 occurs in the top 12 inchesoccurs in the top 12 inches

In small pores and lower in the filter, oxygen In small pores and lower in the filter, oxygen concentrations are reduced and someconcentrations are reduced and some DenitrificationDenitrification can can occur in smaller saturated pores, releasing nitrogen gas occur in smaller saturated pores, releasing nitrogen gas (N(N22))

Single Pass SystemsSingle Pass Systems

Any of the media options may be used in Any of the media options may be used in either single pass or recirculating modeeither single pass or recirculating modeNatural/Mineral media are more likely to Natural/Mineral media are more likely to be used in single pass modebe used in single pass modeManufactured media are usually used in Manufactured media are usually used in recirculating moderecirculating mode

Single Pass Sand FiltersSingle Pass Sand Filters

Several designs are in useSeveral designs are in useFree accessFree accessBuried single passBuried single passPressure dosed single passPressure dosed single pass

Free Access Sand FiltersFree Access Sand FiltersOldest form Oldest form –– most often used for communities most often used for communities Used for community wastewater treatment in Used for community wastewater treatment in Massachusetts in the late 1800’sMassachusetts in the late 1800’sMay be large May be large –– several acres in sizeseveral acres in sizeDepth ranged from 3 to 8 feetDepth ranged from 3 to 8 feetWastewater is pump or siphon dosed to the Wastewater is pump or siphon dosed to the filter, discharged at a single pointfilter, discharged at a single pointGravity flow over the surface of the filterGravity flow over the surface of the filterRequire frequent maintenance of the surface to Require frequent maintenance of the surface to break up or remove accumulated solidsbreak up or remove accumulated solidsLargely historic, but some still being designed Largely historic, but some still being designed and used in the northeastern states and used in the northeastern states

Dose Pump

Dose Tank

Valve Box

Sand Treatment Media

Top of Container Wall

Top of Media Treatment

Drain

Splash Plate

Two Cell Free Two Cell Free Access Sand Access Sand

FilterFilter

Plan ViewPlan View

Cross Section Cross Section

Buried, Gravity Fed Single Pass Buried, Gravity Fed Single Pass Sand FiltersSand Filters

Used as single home systems Used as single home systems Some have surface discharge after Some have surface discharge after disinfectiondisinfectionEffluent “distribution” is through 4Effluent “distribution” is through 4--inch inch diameter pipe with large (1/2” +) diameter pipe with large (1/2” +) perforationsperforationsSeptic tank effluent flows by gravity to the Septic tank effluent flows by gravity to the filter at whatever rate it flows from the tankfilter at whatever rate it flows from the tankPoor distribution limits the life and Poor distribution limits the life and performance performance

From Septic TankDistribution

Box

Drain Vent

Port

Port

DeepObs. Port

Vent

Buried Sand FilterGravity Fed

2" Sand

6-12"

Washed Pea Gravel

PVC Liner

12"

24" Min ASTM C-33 Concrete Sand

Deep Observation Port

6"6"

4" Gravity Drains

Vent

Pea Gravel or Drain Rock

Drain Lines Manifolded to One Outlet

Drain Outlet

2" Sand Cushion

Observation Port

Sandy Soil 6" Min.

Buried Gravity Flow Buried Gravity Flow Single Pass Sand FilterSingle Pass Sand Filter

Plan ViewPlan View

Cross Section Cross Section

Pressure Dosed Single Pass Pressure Dosed Single Pass Sand Filters (SPSF)Sand Filters (SPSF)

The preferred system The preferred system –– uniform uniform applicationapplicationPump control can include a timer so that Pump control can include a timer so that effluent can be “microeffluent can be “micro--dosed” to the sand dosed” to the sand filter uniformly over time as well as spacefilter uniformly over time as well as spaceProvides the ultimate in slow, unsaturated Provides the ultimate in slow, unsaturated flow flow

Assures film flowAssures film flowLong residence time for biological reactionsLong residence time for biological reactionsAir remains in pores for oxygen diffusion into Air remains in pores for oxygen diffusion into the moisture films on surfaces the moisture films on surfaces –– to microbesto microbes

Single Pass Pressure Dosed Sand FilterSingle Pass Pressure Dosed Sand FilterWith Pump Basin With Pump Basin –– Cross SectionCross Section

Single Pass Sand Filter With Discharge Pump

Geo-FabricLoamy Sand or Decorative Rock

Stone (2" Over Pipe)

Filter Sand (See Specifications)

Pea Gravel

30 MIL PVC Liner

Pump Basin Sand Backfill

2" Sand Leveling Layer

PVC Lateral w/ Orifice Shields

Flushing Valve Valve Box

Liner Support (1/2" Plywood)

To Soil

Optional Lateral/Flushing Valve Connections

6"6"

2'

6"

Sweep 2 - 45°

SPSF Design CriteriaSPSF Design CriteriaSurface area loading = 1 Surface area loading = 1 –– 1.25 gpd/ft2 (design 1.25 gpd/ft2 (design Q)Q)Media depth 24 inchesMedia depth 24 inchesMedia specificationMedia specification

Typical: dTypical: d10 10 = 0.3 = 0.3 –– 0.6 mm, C.U. (i.e. d0.6 mm, C.U. (i.e. d10 10 / d/ d6060) = 4 +/) = 4 +/--For colder climates: dFor colder climates: d1010 = 0.4 = 0.4 –– 0.9 mm, C.U. < 4 See 0.9 mm, C.U. < 4 See curve.curve.

Maximum soil cover 8 Maximum soil cover 8 –– 12 inches12 inchesTexture of soil cover: sand or loamy sandTexture of soil cover: sand or loamy sandBottom layer: 6 Bottom layer: 6 –– 8 inches of pea stone around 8 inches of pea stone around draindrainMaximum flow distance to 4” slotted drain: 15 ftMaximum flow distance to 4” slotted drain: 15 ft

Importance of Media Importance of Media SpecificationSpecification

Correct media is an important factor in Correct media is an important factor in determining the useful life of a SPSFdetermining the useful life of a SPSFMedia availability is an issue is some areasMedia availability is an issue is some areasIf material that fits the media spec is not If material that fits the media spec is not available, error on the coarse side.available, error on the coarse side.

If media is too fine If media is too fine –– filter will clog with biomatfilter will clog with biomatIf media is too coarse If media is too coarse –– effluent quality may be effluent quality may be reduced, but only slightlyreduced, but only slightly

Smaller, more frequent doses can partially Smaller, more frequent doses can partially compensate for somewhat coarser mediacompensate for somewhat coarser media

SPSF Media SPSF Media –– Typical SpecificationTypical SpecificationGrain Size Distribution Curve EnvelopeGrain Size Distribution Curve Envelope

SPSF CutSPSF Cut--Away IllustrationAway Illustration

SPSF Media for Cold Climates SPSF Media for Cold Climates

In cold climates, winter decomposition of In cold climates, winter decomposition of organic solids within the media is slowedorganic solids within the media is slowedThe typical media (DThe typical media (D1010 = 0.3= 0.3--0.5, C.U. = 10.5, C.U. = 1--4) may clog prematurely4) may clog prematurelySome states have adopted a coarser Some states have adopted a coarser media specification of Dmedia specification of D1010 = 0.4= 0.4--0.9, C.U. 0.9, C.U. = 1= 1--4, to reduce this tendency. 4, to reduce this tendency.

Small Diameter, Low Pressure Small Diameter, Low Pressure Pipe NetworkPipe Network

Lateral pipe diameter for an individual Lateral pipe diameter for an individual home system home system

Typically ¾” or 1” schedule 40 PVCTypically ¾” or 1” schedule 40 PVCTypically 1/8” orifices spaced 1.5 Typically 1/8” orifices spaced 1.5 –– 2.5 feet2.5 feetTypical pipe spacing is 1.5 Typical pipe spacing is 1.5 –– 2.5 feet 2.5 feet Several sources offer software for the Several sources offer software for the hydraulic design of the pressure network. hydraulic design of the pressure network. The Hydraulics Module provides guidance for The Hydraulics Module provides guidance for pipe network designpipe network design

Plan View – Single Pass Pressure Dosed Sand Filter

30 MIL PVC Liner

Orifice Shield

Pump Basin

To Pump Control Panel

Discharge Line

Flushing Valve & Enclosure

From Septic Tank

To Soil

1.5-2.5'

Top View: Single Pass Sand Filter

1/2 Lateral Space

1/2 Orifice Space

1.5-2.5'

As Required

As Required

PVC Lateral

Pressure Distribution Network Pressure Distribution Network

Illustration courtesy of GAG Sim/Tech Filter,Inc.

SPSF Showing Valve Boxes Over CleanoutsSPSF Showing Valve Boxes Over Cleanouts

Pressure Distribution NetworkPressure Distribution Network

SPSF Slightly Above GradeSPSF Slightly Above Grade

Hydraulic and Organic Loading Hydraulic and Organic Loading ---- SPSFSPSF

Typical design hydraulic loading is 1 Typical design hydraulic loading is 1 –– 1.2 gpd/ft1.2 gpd/ft22

Maximum organic loading is .002 lb BOD/ ftMaximum organic loading is .002 lb BOD/ ft22/da/daCalculate from: O.L. = 8.34 x 10Calculate from: O.L. = 8.34 x 10--66 Q gpm x BOD Q gpm x BOD mg/Lmg/LLower value recommended for cold climatesLower value recommended for cold climates

For cold climates, keep hydraulic load < 1.0 gpdFor cold climates, keep hydraulic load < 1.0 gpdDose volume < 0.5 gal/orifice/doseDose volume < 0.5 gal/orifice/doseTypical doses per day = 18 Typical doses per day = 18 –– 2424

Orifice OrientationOrifice OrientationUpward directed orificesUpward directed orifices

Less prone to cloggingLess prone to cloggingLess flow as the network fills and pressurizesLess flow as the network fills and pressurizesRequire special provision for drainageRequire special provision for drainage

•• Network set to drain back to pump chamber Network set to drain back to pump chamber –– no check valveno check valve•• Some orifices placed in the bottom of the pipe Some orifices placed in the bottom of the pipe –– a less a less

positive solution because these orifices are prone to cloggingpositive solution because these orifices are prone to clogging

Downward directed orificesDownward directed orificesMore prone to clogging More prone to clogging –– alleviated with good orifice alleviated with good orifice shieldsshieldsMore prone to cloggingMore prone to clogging

Orifices directed to the side (3 and 9 O'clock)Orifices directed to the side (3 and 9 O'clock)Less clogging than downward orificesLess clogging than downward orificesAdequate drainageAdequate drainageA bit more flow released as orifices fillA bit more flow released as orifices fill

Design for MaintenanceDesign for MaintenanceMonitoring tubesMonitoring tubes

To infiltrative surfaceTo infiltrative surfaceTo the bottom of the filter, the linerTo the bottom of the filter, the liner

Provide for flushing of distribution lateralsProvide for flushing of distribution lateralsAccess to dead end laterals Access to dead end laterals Continuous, low rate flushingContinuous, low rate flushingAlternating flow directionAlternating flow direction

Provide for aerationProvide for aerationRegular, continuousRegular, continuousCatastrophic rejuvenationCatastrophic rejuvenation

Prevent storm water infiltrationPrevent storm water infiltration

Maintenance or SPSFMaintenance or SPSFMaintenance should be performed at least annually, Maintenance should be performed at least annually, preferably more oftenpreferably more often

Owners should hire knowledgeable maintenance Owners should hire knowledgeable maintenance providerprovider

First visit MUST be within the first few weeks of useFirst visit MUST be within the first few weeks of useTo catch construction damage or errorsTo catch construction damage or errors

To be sure controls are set correctly for the use patternTo be sure controls are set correctly for the use pattern

To check for leaks, including leaky tanksTo check for leaks, including leaky tanks

To advise owner/resident on SPSF useTo advise owner/resident on SPSF use

To be sure landscaping does not add depth, compact or cause To be sure landscaping does not add depth, compact or cause other damageother damage

Maintenance Routine for the Maintenance Routine for the SPSFSPSF

The septic tank(s) should be inspected periodically (not every The septic tank(s) should be inspected periodically (not every visit) and pumped as neededvisit) and pumped as needed

Flush pressure pipe networkFlush pressure pipe network

Check pressure at end of laterals: compare with previousCheck pressure at end of laterals: compare with previous

Check sand filter for Check sand filter for pondingponding (in monitoring tubes)(in monitoring tubes)

Check pump controls for proper operationCheck pump controls for proper operation

Read pump runRead pump run--time meter and event countertime meter and event counter

Check pump voltage (off and while pumping) and amp draw Check pump voltage (off and while pumping) and amp draw while pumpingwhile pumping

Pull and observe the final effluent in a clear sample bottle Pull and observe the final effluent in a clear sample bottle checking for clarity and odor.checking for clarity and odor.

Drainfield Check as Part of Drainfield Check as Part of Maintenance visitMaintenance visit

Check for wetness around the drainfieldCheck for wetness around the drainfield

Note vegetation patterns Note vegetation patterns

Note ponding level in observation tubesNote ponding level in observation tubes

Observe surface flow patterns Observe surface flow patterns Be sure surface runoff is directed away from drainfield and SPSFBe sure surface runoff is directed away from drainfield and SPSF

Roof water/downspout drainage away from systemRoof water/downspout drainage away from system

This drawing showsThis drawing showsan air coil added an air coil added underneath the sandunderneath the sandtreatment media sotreatment media sothat air can bethat air can beintroduced from introduced from below to enhancebelow to enhancebiological digestionbiological digestionof a clogging matof a clogging matthat might form onthat might form onthe top of the media.the top of the media.

Recirculating SystemsRecirculating Systems

Recirculation is used in many wastewater Recirculation is used in many wastewater treatment processes, usually to retain organism treatment processes, usually to retain organism populationspopulationsRecirculating sand filter concept was introduced Recirculating sand filter concept was introduced by Hines and Favreau in the 1970’s.by Hines and Favreau in the 1970’s.Recirculating systems involve mixing a portion of Recirculating systems involve mixing a portion of the filtered effluent with incoming septic tank the filtered effluent with incoming septic tank effluenteffluentThis blended effluent is applied to the coarser This blended effluent is applied to the coarser filter media at higher loading rates filter media at higher loading rates

Recirculation MechanismsRecirculation Mechanisms

Pump in a recirculation tank is operated by a Pump in a recirculation tank is operated by a timertimer

Timer is set to deliver a daily flow to the filter of:Timer is set to deliver a daily flow to the filter of:QQff = Q= Qii(R(Rrr +1)+1)Where, Where, QQff is the daily quantity to the filteris the daily quantity to the filter

RRrr is the recirculation ratiois the recirculation ratioQQii is the daily inflow to the filteris the daily inflow to the filter

Recirculation ratio is defined as the ratio of daily Recirculation ratio is defined as the ratio of daily quantity of flow returned to the recirc. tank, Qquantity of flow returned to the recirc. tank, Qrr, , divided by the daily inflow, Qdivided by the daily inflow, Qii

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

Achieving RecirculationAchieving Recirculation

Drainage from the filter is directed through Drainage from the filter is directed through a flow dividera flow divider

One part is sent to final dispersalOne part is sent to final dispersal3 3 –– 5 parts, more or less, are returned to the 5 parts, more or less, are returned to the recirc. tank for another pass through the filterrecirc. tank for another pass through the filter

The pump control timer is set to deliver the The pump control timer is set to deliver the desired total quantity of flow to the filter desired total quantity of flow to the filter dailydaily

QQff = Q= Qi i (R(Rrr +1)+1)

Recirculation Ratio DefinitionRecirculation Ratio DefinitionR = Q /QRr = Qr/QiQQrr = R= Rrr QQiiQQff = Q= Qrr + Q+ Qii = (R= (Rr r +1)+1)

QQii

Where:Where:

RRrr is the recirculation ratiois the recirculation ratio

QQrr is the daily flow returning to is the daily flow returning to the the recirc tankrecirc tankQQff is the daily flow through the is the daily flow through the

filter, in gpd.filter, in gpd.

QQii = = QQee is the daily forward flow is the daily forward flow

Recirculation/Blend Tank

PackedBed Filter

Qf = (Rr+1)Qi

Qe

Qi

Qr = RrQi

Rr = recirc-blend ratio = Qr/Qi

Qe = Qi

Qf = daily flow to filter

r r i

Simple Float Valve IllustrationSimple Float Valve IllustrationValve is mounted in the Valve is mounted in the recirc. tank on the filter recirc. tank on the filter drain return linedrain return lineWhen the valve is closed, When the valve is closed, all the flow is sent to final all the flow is sent to final dispersaldispersalWhen the valve is open, When the valve is open, all the flow drops into the all the flow drops into the tanktankBy setting the timer for By setting the timer for the correct total daily flow the correct total daily flow to the filter, the system to the filter, the system provides the proper provides the proper recirculation ratio.recirculation ratio.

Float Valve2" Tee

Tapered ReducerRacketball or Durable

Plastic Ball

Section of Styrofoam3" PVC

Plastic or Stainless Bar

3"x2"

Proprietary Flow Splitting Proprietary Flow Splitting Valve Valve

A baffle downstream A baffle downstream from the vertical stem from the vertical stem forces flow to exit the forces flow to exit the return pipe in such areturn pipe in such amanner that a preset manner that a preset amount of flow, dependingamount of flow, dependingon the number of overflow on the number of overflow pipes that are uncapped, pipes that are uncapped, will return to the recirc. will return to the recirc. tank even when the floattank even when the floatvale is closed.vale is closed.

Courtesy of Orenco Systems, Inc.Courtesy of Orenco Systems, Inc.

Another Flow Splitting OptionAnother Flow Splitting Option

H

Flow Control Orifices InRemovable Standpipe

Watertight Grommet

Discharge

Screened Influent

Side View - Flow Splitter Basin

Top View - Flow Splitter Basin

3"3"

2" Typ.

L.L.

Adapted from Orenco Systems, Inc. drawingAdapted from Orenco Systems, Inc. drawing

RSF Schematic with Dual Slope RSF Schematic with Dual Slope BottomBottom

Septic TankSand Filter Dosing Tank Final Effluent Tank

Sand Filter

From House To Soil

Effluent Filter Sand Filter Dosing PumpOn Timer

Effluent Pump(Float Controlled)

Denitrifying Sand Filter

Return

Filter Drainage

Recirc Tank

Typical RSF Cross SectionTypical RSF Cross Section

Filter Sand (refer to gradation curve)

30 MIL PVC Liner

Option: Ag. Drain w/ RSF media all the way down

See Detail A

End Cap 4" Slotted Underdrain

PVC Boot

6"-9"

24"

3/8" Pea Gravel Washed(1"-2" over laterals)

3/8" Pea Gravel

2" Sand Leveling Layer

To Recirc. Tank

PVC Lateral w/ Orifice Shields

Flushing Valve

Perimeter Support Frame (1/2" untreated plywood)

Sand

4" Boot(s)

Adapted from Orenco Systems, Inc.Note, this may not be the best drawing

Home RSF Nicely LandscapedHome RSF Nicely Landscaped

Benefits of RecirculationBenefits of RecirculationDiluted effluent is applied to the filterDiluted effluent is applied to the filter

Can apply effluent a greater forward flow loading rateCan apply effluent a greater forward flow loading rateLess odorLess odor

Smaller filter surface area required for a given Smaller filter surface area required for a given flowflowCan withstand somewhat higher strength Can withstand somewhat higher strength incoming wastewaterincoming wastewaterCan cope with flow variations, including peak Can cope with flow variations, including peak flowsflowsProvides a means for making adjustments for Provides a means for making adjustments for variations in flow and strength through varying variations in flow and strength through varying recirculation ratiosrecirculation ratios

RSF MediaRSF Media

Effective Grain Size (dEffective Grain Size (d1010): 1.5 ): 1.5 –– 2.5 mm (or 2.5 mm (or larger)larger)Uniformity Coefficient: < 2 Uniformity Coefficient: < 2 Media Depth: Minimum of 24Media Depth: Minimum of 24””Typical Void space: 30%Typical Void space: 30%Typical Moisture Holding Capacity: < 7%Typical Moisture Holding Capacity: < 7%

RSF MediaRSF MediaGrain Size Distribution Curve EnvelopGrain Size Distribution Curve Envelop

Typical RSF MediaTypical RSF Media

Fine gravel Fine gravel media with media with effective size of effective size of 2.5 2.5 –– 3 mm3 mmNote lack of Note lack of fines on the fines on the mediamediaThis is a good This is a good material for an material for an RSF for RSF for domestic domestic effluenteffluent

Recirculation Tank DesignRecirculation Tank DesignSize Size –– provide volume at least equal to provide volume at least equal to daily design flowdaily design flowConfigurationConfiguration

Septic tank effluent and return flow from filter Septic tank effluent and return flow from filter enter at same end of the tank to mixenter at same end of the tank to mixPump(s) to filter are at opposite end of tankPump(s) to filter are at opposite end of tankProvide long flow path to pump endProvide long flow path to pump endPumps mounted up off tank floorPumps mounted up off tank floor•• Preferably in a vault with effluent screen ahead of Preferably in a vault with effluent screen ahead of

pump intakepump intake•• Intake to pump at midIntake to pump at mid--depth of tankdepth of tank

RSF RSF ---- Recirculation Tank Recirculation Tank IllustrationIllustration

Home Size RSF Home Size RSF –– Training Center DemonstrationTraining Center DemonstrationUnit is 10’ x 10’ with exposed stone surface, recirc. tank bUnit is 10’ x 10’ with exposed stone surface, recirc. tank belowelow

Some stone removed to expose distribution pipe and treatment medSome stone removed to expose distribution pipe and treatment mediaia

RSF with Mix/Recirc. Zone RSF with Mix/Recirc. Zone in Chambers Under Mediain Chambers Under Media

Peastone: 4" Over Chambers

24" Min

9 - 12"

See RSF Media Spec

Framing Timbers

Excavation Wall or Plywood Frame

2" Sand Cushion

Peastone or Drain Rock

Pressure Laterals

Recirculating Sand Filter with Mix Zone Underneath

Plan View Plan View –– Mix Zone in Chambers Mix Zone in Chambers Under MediaUnder Media

Effluent InChamber Connections

To Recirc Pump Tank

LPP Distribution Network on Community RSF

Multiple Cell Community RSF Makes Maintenance EasierMultiple Cell Community RSF Makes Maintenance Easier

Laterals End with Constant Flow OutLaterals End with Constant Flow Out

Access to Dead End Laterals in the Middle of a Large RSFAccess to Dead End Laterals in the Middle of a Large RSF

Measurement of Measurement of Pressure at the End of Pressure at the End of LateralsLaterals

Head is typically 5Head is typically 5--8 8 ftftClear tube that can Clear tube that can be screwed in or be screwed in or attached to laterals attached to laterals allows easy allows easy determination of determination of headheadHead increase over Head increase over time may mean time may mean clogging of orificesclogging of orifices

Alternative Distribution System Alternative Distribution System Upward Directed Orifices in Upward Directed Orifices in

ChamberChamber

2" Over Chambers

24" MinRSF Treatment Media

Sand Filter w/ Upward Directed Orifices in a Chamber

Pea Gravel

Pea Gravel

PVC Liner

Alternative Distribution System Alternative Distribution System NonNon--Clog Spray Nozzles in Clog Spray Nozzles in

ChamberChamber

2" Over Chambers

24" MinRSF Treatment Media

Sand Filter w/ Spiral Nozzles in a Chamber

Pea Gravel

Pea Gravel

Sand Filter Frame Ready for MediaSand Filter Frame Ready for Media

Sand Filter Drain NetworkSand Filter Drain Network

Residential Community RSF in Operation

RSF Effluent QualityRSF Effluent Quality

RSF Maintenance TasksRSF Maintenance TasksCheck observation sumps in S.F. for pondingCheck observation sumps in S.F. for pondingFlush distribution system lines Flush distribution system lines Check pressure to determine orifice cloggingCheck pressure to determine orifice cloggingClean orifices as neededClean orifices as neededMake sure drain(s) are not submerged and can Make sure drain(s) are not submerged and can “breath” air into filter“breath” air into filterCheck pump controls for proper operation and Check pump controls for proper operation and adjustmentadjustmentCheck pump voltage Check pump voltage –– off and while pumpingoff and while pumpingCheck pump amp draw while pumpingCheck pump amp draw while pumpingCheck Soil Absorption System observations sumpsCheck Soil Absorption System observations sumpsCheck sludge and scum in septic tank(s) & pump Check sludge and scum in septic tank(s) & pump tanktank

Manufactured/Prepackaged Manufactured/Prepackaged MF’sMF’sSeveral types of Several types of MF’sMF’s are packaged in modular are packaged in modular unitsunitsSand filters have been packaged for local Sand filters have been packaged for local markets in some locationsmarkets in some locationsThree types are prominent nationallyThree types are prominent nationally

Peat filtersPeat filtersTextile filtersTextile filtersOpen cell foam filtersOpen cell foam filters

These three materials have significant These three materials have significant advantageadvantage

Large media surface areaLarge media surface areaHigh percentage of void space in the mediaHigh percentage of void space in the mediaLight weight for shippingLight weight for shippingEasier maintenanceEasier maintenancePredictable, consistent, high quality material Predictable, consistent, high quality material

Peat FiltersPeat FiltersPeat provides an excellent media for Peat provides an excellent media for MF’sMF’sUsed in several formsUsed in several forms

Peat fiberPeat fiberPeat mossPeat mossPeat pelletsPeat pelletsPrefabricated peat balesPrefabricated peat bales

Several manufacturers provide modular peat Several manufacturers provide modular peat filters ready to set in place and connect upfilters ready to set in place and connect upTypical components Typical components –– all in a prefabricated all in a prefabricated containercontainer

Distribution systemDistribution systemPeat mediaPeat mediaDrainage systemDrainage system

Peat Filters (con’t.)Peat Filters (con’t.)Typically used in single pass modeTypically used in single pass modePeat is carefully chosen and, in some cases, Peat is carefully chosen and, in some cases, processed processed Peat will house a wide variety of micro flora from Peat will house a wide variety of micro flora from bacteria to nematodesbacteria to nematodesPeat will deteriorate over time an need to be Peat will deteriorate over time an need to be replaced.replaced.

Peat fiber lasts longPeat fiber lasts longManufacturers estimate media life at 8 Manufacturers estimate media life at 8 –– 15 years15 years

Manufacturers have proprietary design criteria Manufacturers have proprietary design criteria and specifications that must be followedand specifications that must be followed

Peat Fiber Filter Module Peat Fiber Filter Module

Peat Filter Modules Over Drain StonePeat Filter Modules Over Drain Stone

Peat Filter PerformancePeat Filter Performance

Peat filters have been found to provide Peat filters have been found to provide good, long term performancegood, long term performanceEffluent quality is similar to sand filters, but Effluent quality is similar to sand filters, but space requirement is less space requirement is less –– about 1/6 as about 1/6 as much.much.Having material preHaving material pre--selected and selected and prepackaged is a big advantageprepackaged is a big advantage

Example Peat Filter Performance DataExample Peat Filter Performance Data

2 x 102 x 104411117744

After After 4 Years4 Years

6 x 106 x 10442225251818

New New Peat Peat FilterFilter

66--7 x 7 x 101055

33 33 -- 39392 2 -- 33116116--132132S.T. w/ S.T. w/ ScreenScreen

Fecal Fecal ColColMPN/10MPN/10

0ml0ml

NHNH33--NNMg/LMg/L

NONO33--NNMg/LMg/L

BODBOD55

Mg/LMg/L

Open Cell Foam FiltersOpen Cell Foam FiltersDeveloped for use in Ontario as the “Waterloo Developed for use in Ontario as the “Waterloo BiofilterBiofiltertmtm””The foam material is a polyurethane foamThe foam material is a polyurethane foam

Foam is in 2Foam is in 2--inch cubesinch cubesLarge surface area, large void volume percentageLarge surface area, large void volume percentageNot decomposed by organisms in wastewaterNot decomposed by organisms in wastewaterLight weight for easy shipping and handlingLight weight for easy shipping and handling

Wastewater is sprayed over the top Wastewater is sprayed over the top Long retention time in the filter provides good Long retention time in the filter provides good treatmenttreatmentSometimes requires forced aerationSometimes requires forced aeration

Waterloo Biofilter Waterloo Biofilter –– Home SizeHome Size

Waterloo Biofilter Foam BasketsWaterloo Biofilter Foam Baskets

Small Modules Containing Foam Cubes Small Modules Containing Foam Cubes ––“Aerocell“Aerocelltmtm””

Scattm System

AdvanTexAdvanTextmtm Textile Based FilterTextile Based Filter

Recirculating Textile Filter Over a 1500 gal Septic tank

Network of Small Textile Filter Units at a SchoolNetwork of Small Textile Filter Units at a School

MF ControlsMF ControlsControl systems for pumps and dosing are Control systems for pumps and dosing are critical to proper operation critical to proper operation Uniform distribution and small, frequent Uniform distribution and small, frequent doses are required for best treatmentdoses are required for best treatmentTimer control for pumps is preferredTimer control for pumps is preferredFor single pass systems, timers can be For single pass systems, timers can be turned on and off by floatsturned on and off by floats

Pump in a recirc. tank with floats to Pump in a recirc. tank with floats to control the timer, alarms, and a second control the timer, alarms, and a second

pumppump

Float Type ControlsFloat Type ControlsFloats may contain mechanical or mercury Floats may contain mechanical or mercury switchesswitchesShould be mounted on a separate bracket Should be mounted on a separate bracket or float “tree”or float “tree”

Separate from pump discharge pipeSeparate from pump discharge pipeRemovable as a unit for float position Removable as a unit for float position adjustmentadjustmentAllow pump removal without disturbing floatsAllow pump removal without disturbing floats

Floats must be positioned so as not to Floats must be positioned so as not to become inhibited by cords, other floats, or become inhibited by cords, other floats, or pipingpiping

Determining Timer SettingsDetermining Timer SettingsDosing frequency (DF) and cycle time CT) are Dosing frequency (DF) and cycle time CT) are terms that are used to mean the same thingterms that are used to mean the same thingCycle time includes pump on or dose time (TCycle time includes pump on or dose time (Tdd) ) and pump off or rest time (Tand pump off or rest time (Trr)) DF = CT= TDF = CT= Tdd + T+ TrrIf the pump is expected to run all the time, 24 If the pump is expected to run all the time, 24 hours (1440 minutes) per dayhours (1440 minutes) per day

nndd = 1440/DF= 1440/DFwhere nwhere ndd is the number of doses per dayis the number of doses per daynndd = Q= Qff/T/TddqqffQQf f = the daily flow to the filter= the daily flow to the filterqqff = the flow rate to the filter while the pump is = the flow rate to the filter while the pump is

runningrunning

SPSF Timer Setting ExampleSPSF Timer Setting ExampleConsider a single pass sand filter having a flow rate, qConsider a single pass sand filter having a flow rate, qff, , of 40 gpm, Tof 40 gpm, Tdd = 30 seconds, and a daily flow, Q= 30 seconds, and a daily flow, Qff, of 200 , of 200 gpd. gpd. It is desirable to set the timer so that the daily flow can It is desirable to set the timer so that the daily flow can be dosed to the filter in less than 24 hours, say 18 be dosed to the filter in less than 24 hours, say 18 hours to provide some buffer for a high flow day.hours to provide some buffer for a high flow day.

nndd = [1440 (18/24)/DF] = Q= [1440 (18/24)/DF] = Qff/T/Tddqqffnndd = [1440 (18/24)/DF] = 200 / 0.5 x 40= [1440 (18/24)/DF] = 200 / 0.5 x 40[1440 (18/24)/DF] = 10[1440 (18/24)/DF] = 10DF = 108 minutesDF = 108 minutesTTrr = 108 = 108 –– 0.5 = 107.5 minutes0.5 = 107.5 minutes

So, to discharge 200 gpd, in 18 hours of the day, the So, to discharge 200 gpd, in 18 hours of the day, the pump should be set to run 30 seconds and rest 107.5 pump should be set to run 30 seconds and rest 107.5 minutes. For about 6 hours in the middle of the night, minutes. For about 6 hours in the middle of the night, the pump is off.the pump is off.

Pump SelectionPump SelectionPumps used are usually submersiblePumps used are usually submersible

High head turbine pumps High head turbine pumps –– a converted well pump a converted well pump Effluent pumps Effluent pumps –– higher flow, low headhigher flow, low head

Turbine pumps are desirable for feeding distribution Turbine pumps are desirable for feeding distribution systems with small holes (typical 1/8”)systems with small holes (typical 1/8”)

Steep curve assists in providing self cleaningSteep curve assists in providing self cleaningHead increases rapidly as flow is reducedHead increases rapidly as flow is reduced

If effluent pumps are used, inIf effluent pumps are used, in--line screens can be line screens can be added to help protect against orifice cloggingadded to help protect against orifice cloggingBoth types of pumps, if selected for effluent Both types of pumps, if selected for effluent applications, will provide long service lifeapplications, will provide long service lifeLiquid levels should be designed to keep pumps Liquid levels should be designed to keep pumps submerged.submerged.

System Monitoring and MaintenanceSystem Monitoring and MaintenanceMF’sMF’s of all types must be designed so that of all types must be designed so that maintenance personnel can easily monitor maintenance personnel can easily monitor condition and performancecondition and performanceEasy access to screens, pumps, floats and other Easy access to screens, pumps, floats and other controlscontrols

Risers to gradeRisers to gradeEasily reachable quick disconnects for pump removalEasily reachable quick disconnects for pump removalFloats on a separate, easily removable mountFloats on a separate, easily removable mountControl boxes within sight of pump chamber riserControl boxes within sight of pump chamber riser

Monitoring tubes to critical levels in filtersMonitoring tubes to critical levels in filtersDistribution laterals easily accessible for Distribution laterals easily accessible for cleaningcleaningConvenient sampling locations for obtaining Convenient sampling locations for obtaining effluent samples for analysis effluent samples for analysis

An Example Maintenance RoutineAn Example Maintenance RoutineCheck sludge and scum levels in the septic tankCheck sludge and scum levels in the septic tankCheck septic tank effluent screen, and clean if necessary.Check septic tank effluent screen, and clean if necessary.Flush Media Filter distribution laterals.Flush Media Filter distribution laterals.Check pressure at the distal end of the lateralsCheck pressure at the distal end of the lateralsNote readings on pump runNote readings on pump run--time meter and event counter and time meter and event counter and compare with previous readings.compare with previous readings.Check pump voltage (off and while pumping) and amp draw Check pump voltage (off and while pumping) and amp draw while pumping.while pumping.Check pump control floats for proper operation and proper Check pump control floats for proper operation and proper elevation adjustment.elevation adjustment.Check for ponding at the media infiltrative surface and the Check for ponding at the media infiltrative surface and the bottom of the filter through observation tubes.bottom of the filter through observation tubes.Pull and observe the final effluent in a clear sample bottle Pull and observe the final effluent in a clear sample bottle checking for clarity and odor.checking for clarity and odor.Check for wetness around the drainfield and observe ponding Check for wetness around the drainfield and observe ponding in observation tubesin observation tubes

Concluding CommentsConcluding CommentsMedia Filters are capable of providing reliable, Media Filters are capable of providing reliable, long term service and excellent effluent quality if long term service and excellent effluent quality if they are:they are:

Properly sitedProperly sitedProperly designedProperly designedProperly used by the owner/occupantProperly used by the owner/occupantProperly maintained on a regular basisProperly maintained on a regular basis

The greatest challenge to be addressed before The greatest challenge to be addressed before widespread adoption of technologies like PBF’s widespread adoption of technologies like PBF’s can be commonplace is the development and can be commonplace is the development and public acceptance of management organizations public acceptance of management organizations and fee structures to assure that the systems and fee structures to assure that the systems are properly maintained on a regular basis.are properly maintained on a regular basis.