MicrosoftPowerPoint-WEF Wet Weather 2008

8/8/2019 MicrosoftPowerPoint-WEF Wet Weather 2008

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Treating Wet Weather Flows in aTreating Wet Weather Flows in a

Membrane BioreactorMembrane Bioreactor

Shane Trussell, Ph.D., P.E.Shane Trussell, Ph.D., P.E.

WEF Membrane Technology 2008

Atlanta, Georgia


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OutlineOutline

IntroductionIntroduction

Review of Important WetReview of Important Wet

Weather MBR DataWeather MBR Data Possible ExplanationsPossible Explanations

What Do We Know TodayWhat Do We Know Today ConclusionsConclusions


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OutlineOutline

IntroductionIntroduction





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IntroductionIntroduction An MBR is not aAn MBR is not a

membrane processmembrane process

An MBR is aAn MBR is a

biological processbiological processthat uses membranesthat uses membranes

for solidsfor solids--liquidliquid

separationseparation


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Principle Advantages ofPrinciple Advantages ofMBR ProcessMBR Process

High qualityHigh qualityeffluenteffluent

CompactCompactFootprintFootprint

High MLSSHigh MLSSconcentrationsconcentrations


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Principle Disadvantage ofPrinciple Disadvantage of

MBR ProcessMBR Process Ability to maintain hydraulic capacityAbility to maintain hydraulic capacity

All treated wastewater exiting an MBRAll treated wastewater exiting an MBR

process must pass through the membraneprocess must pass through the membrane

Peak flows are aPeak flows are aparticularlyparticularlysignificant issuesignificant issue


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OutlineOutline IntroductionIntroduction





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1)1) Data presented atData presented at

WEFTEC in 2006WEFTEC in 20062)2) Data from 2007Data from 2007

STOWA reportSTOWA reportentitled,entitled, OperationOperation

and results of anand results of anMBR WWTPMBR WWTP by vanby vanBentemBentem et al.et al.


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Two Pilot Studies on LargeTwo Pilot Studies on LargeCombined Sewer SystemsCombined Sewer Systems

SEATTLE WPTP Kubota ESKubota ES--75s75s -- 1 deck1 deck

Flat plateFlat plate

MFMF -- 0.40.4 mm

9 min cycle9 min cycle -- 1 min relax1 min relax

Flux rate = 32 gfdFlux rate = 32 gfd

Aeration = 28 to 36 scfmAeration = 28 to 36 scfm

June 2002 to June 2003June 2002 to June 2003

Capacity ~ 10,000Capacity ~ 10,000 gpdgpd

Treating primary effluentTreating primary effluent

SAN FRANCISCO SEP ZenonZenon ZW500cZW500c

Vertical hollow fiberVertical hollow fiber

UFUF -- 0.0350.035 mm

9 min cycle9 min cycle -- 30 sec relax30 sec relax

Flux rate = 18 gfdFlux rate = 18 gfd

Aeration = 30 scfmAeration = 30 scfm

Oct 2002 to Feb 2005Oct 2002 to Feb 2005

Capacity ~ 10,000Capacity ~ 10,000 gpdgpd



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San FranciscoSan Francisco -- 2003 to 20052003 to 2005

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

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10/1/04

11/

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12/1/04

1/1/05

2/1/05

3/1/05

Rain,

in Year 1 Year 1 Year 2 Year 3

SRT = 10 d SRT = 5 dSRT = 10 d SRT = 5 d


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SF Year 1SF Year 1 -- 5 d SRT5 d SRT

0

5

10

15

20

25

30

35

40

180 190 200 210 220 230 240 250 260 270 280

Days of Operation

0

50

100

150

200

250

300

S

pecificFlux@2

0oC,

LMH/bar

Flux Specific Flux

Foam EventDay 185

89 Days at 5-d MCRT

(F/M = 0.53 gCOD/gVSS.d)

Steady-state fouling rate

Fouling Rate = 0.017 LMH/bar

.

h


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SF Year 3SF Year 3 -- 5 d SRT5 d SRT

y = -3.1569x +

69.524

R2 = 0.991

0

5

10

15

20

25

30

35

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0 1 2 3 4 5 6 7 8 9 10

Minutes of Operation

0

50

100

150

200

250

300

SpecificFlux@2

0oC,

Flux S ecific Flux

Fouling Rate = 188 LMH/bar.h

> 10,000 x faster


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Summary of Membrane FoulingSummary of Membrane FoulingRates and Exp. ConditionsRates and Exp. Conditions

Location Experiment SRT, dFouling Rate@20oC,

LMH/bar.h

Flux,

LMH

Aeration

Intensity, m/sMLSS, g/L

10 0.016 7.8

5 0.017 8.6

Year 2 10 0.090 14

Year 3 5 188 6.5

Exp 1 54 1.3 8.4

Exp 2 54 23 7.7

Exp 3 15 0.53 2.87x10-4

10.3

2.28x10-430

2.23x10-4

Year 1

San Francisco

Seattle 54


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Varsseveldarsseveld MBR 2005MBR 2005

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 5 10 15 20 25

Production, L/m2

van Bentem, et al. (2007)

Observed significant decreases

in membrane permeabilityduring wet weather events


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0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 5 10 15 20 25

Production, L/m2

January

to April

Wet Weather

Season


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0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 5 10 15 20 25

Production, L/m2

June toOctober

Dry Weather

Season


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WhatWhats happening?s happening?


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Sludge DeflocculationSludge Deflocculation

SF Year 3 - 1000x

Diffuse Floc StructureSF Year 3 - 1000x

Supernatant from the

Colloidal Material Method

Single Cells and Nocardioforms


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Summary of Mixed LiquorSummary of Mixed Liquor

Properties for San FranciscoProperties for San Francisco

Year 1 Year 2 Year 1 Year

Colloidal MaterialNTU - 72 53 104

SMPc mg/L 10 26 23 90SMPp mg/L 25 19 20 60

Total SMP mg/L 35 45 42 150

EPSc mg/g VSS18 24 16 17EPSp mg/g VSS102 62 70 87

Total EPS mg/g VSS120 86 86 104

10 d MCR 5 d MCRTMixed LiPropert Units


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Summary of FindingsSummary of Findings Sludge filterability decreased after significant

storm events

A significant decrease in membrane permeability

occurred

Potentially serious issue - when the peak flux isrequired - cannot perform due to low permeability

Poor sludge filterability resulted from diffuse flocs

with an abundance of single cells and dispersefilaments

Same phenomenon occurred in two independent

studies on combined sewers and at one full-scale


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Weather MBR DataWeather MBR Data

Possible ExplanationsPossible Explanations



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Possible Causes for Observed SludgePossible Causes for Observed SludgeDeflocculation Due to Wet WeatherDeflocculation Due to Wet Weather

Increase in influent colloidal materialIncrease in influent colloidal material Increase in influent toxicantsIncrease in influent toxicants

Decrease in influent CODDecrease in influent COD Decrease in divalent cation conc.Decrease in divalent cation conc.

Issues with pilot reactor design (CSTR)Issues with pilot reactor design (CSTR)


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Influent Colloidal MaterialInfluent Colloidal Material


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TriTri--City Service DistrictCity Service District

MBR Pilot StudiesMBR Pilot Studies Designed Experiments to Test Wet Weather FlowDesigned Experiments to Test Wet Weather Flow

ConditionsConditions ZW500D UFZW500D UF -- 0.0350.035 m/ Area: 680 ftm/ Area: 680 ft22


44--month operationmonth operation

As membrane flux is increased to simulate peakAs membrane flux is increased to simulate peak

flows, secondary effluent is fed to the reactor asflows, secondary effluent is fed to the reactor as

make up water (dilution of influent COD)make up water (dilution of influent COD)

Same divalent cation concentrations and ratiosSame divalent cation concentrations and ratios


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Decrease in Influent CODDecrease in Influent COD

9 gfd

24 gfd

11 gfd 15 gfd 19 gfd 15 gfd 9 gfd

>50%

Dilution

18%

Dilution

40%

Dilution


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Decrease in influent CODDecrease in influent COD

Decrease in divalent cation conc.Decrease in divalent cation conc.


I i h Pil RI i h Pil R


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Issues with Pilot ReactorIssues with Pilot Reactor

Design (CSTR)Design (CSTR) Increase in sludge colloidal content occurredIncrease in sludge colloidal content occurred

at theat the VarsseveldVarsseveld MBR in wet weather seasonMBR in wet weather season

TheThe VarsseveldVarsseveld facility is an oxidation ditchfacility is an oxidation ditch

with an effective PFR designwith an effective PFR design

Additionally, other large MBR facilities areAdditionally, other large MBR facilities arereportingreporting more than normal temperaturemore than normal temperature

correctioncorrection fouling during wet weather flowsfouling during wet weather flows

Although there is no doubt that the reactorAlthough there is no doubt that the reactor

design is important, this does not appeardesign is important, this does not appear

unique to pilotunique to pilot MBRsMBRs with CSTR designswith CSTR designs


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ConclusionConclusion

Sludge filterability decreases after significantstorm events and decrease in membrane

permeability Poor sludge filterability results from

deflocculation

Exact cause of deflocculation is not known What we do know:

Not caused by an increase in influent colloidalcontent

Not caused by the dilution of influent COD

Not only an artifact of pilot-scale MBRs (CSTR)


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Possible causes of sludge deflocculation:

Toxicity

Dilution of divalent/trivalent cationconcentrations

In addition, this sludge deflocculation will

reduce the efficacy of the coarse bubble airscour:

Deflocculation negatively impacts sludge

viscosityTemperature will also negatively impact sludge

viscosity

Mi d Li Vi itMi d Li Vi it


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Mixed Liquor ViscosityMixed Liquor Viscosity

0

100

200

300

400

500

600

700

10 12 14 16 18 20 22 24 26 28

MLSS, g/L

10-d MCRT 20-d MCRT 30-d MCRT

LV Spindle #2, 100 rpm

Colloidal = 73 NTU

Colloidal = 23-26 NTU


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RM RF R

C

JssJss == to membraneto membrane

VVLL = away from membrane= away from membrane

JssJss VVLL (rapid fouling)(rapid fouling)


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Mixed Liquor ViscosityMixed Liquor Viscosity

Adapted from Cui et al., 2003Journal of Membrane Science


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Nothings changed for biological design!

Need a good biological design that

encourages bioflocculation and minimizes themixed liquor colloidal content
















We do not necessarilyneed flocs that settle

We do need flocs that

filter well


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AcknowledgementsAcknowledgements Dr.Dr. RionRion Merlo, ProfessorMerlo, Professor SlawomirSlawomir

HermanowiczHermanowicz, Professor Emeritus David, Professor Emeritus DavidJenkins at UC BerkeleyJenkins at UC Berkeley

The City and County of SF SEP staffThe City and County of SF SEP staff

King County Wastewater Treatment DivisionKing County Wastewater Treatment Division

The TriThe Tri--City Service District StaffCity Service District Staff

MWH Americas: Jude Grounds and DaleMWH Americas: Jude Grounds and DaleRichwineRichwine

GE/GE/ZenonZenon


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Thank you!Thank you!

[email protected]@trusselltech.com

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