Trinidad Seawater Reverse Osmosis Plantmosis plant

Design and PerformanceDesign and Performanceof the Pretreatment for theof the Pretreatment for the

Point Point Lisas Lisas DesalterDesalterR. Rhodes TrussellR. Rhodes Trussell

Trussell Technologies, Inc.Trussell Technologies, Inc.Pasadena, CAPasadena, CA

Joe JacangeloJoe JacangeloMWH, Inc.MWH, Inc.Reston, VAReston, VA

Ron CassRon CassMWH, Inc.MWH, Inc.Atlanta, GAAtlanta, GA

AcknowledgmentsAcknowledgments

oo MHW:MHW:oo Phil WallerPhil Walleroo Jude GroundsJude Grounds

oo Desalination CompanyDesalination Companyof Trinidad & Tobagoof Trinidad & Tobago((DesalcottDesalcott))oo Dr. Ian Dr. Ian RamroopRamroopoo John ThompsonJohn Thompson

Outline of TalkOutline of Talk

oo Background on projectBackground on projectoo Development of pre-design conceptDevelopment of pre-design conceptoo Pilot resultsPilot resultsoo Final design specificationsFinal design specificationsoo First year and a half of performanceFirst year and a half of performance

Background on ProjectBackground on Project

oo Ionics organized a team that prepared theIonics organized a team that prepared thesuccessful bid for the 26 mgd desalter tosuccessful bid for the 26 mgd desalter toprovide drinking-quality water for theprovide drinking-quality water for theTrinidad and Tobago Water and SewageTrinidad and Tobago Water and SewageAuthorityAuthority

oo MWH Inc. was a member of that team,MWH Inc. was a member of that team,charged with design of the system tocharged with design of the system topretreat the water for SWRO as well aspretreat the water for SWRO as well ascertain other support facilitiescertain other support facilities


oo Based on IonicsBased on Ionics’’ experience with other experience with otherprojects, the bid was prepared basedprojects, the bid was prepared basedon coagulation, sedimentation and twoon coagulation, sedimentation and twostage, dual media filtrationstage, dual media filtration

oo After the After the Ionics Ionics team was selected,team was selected,MWH conducted a more detailedMWH conducted a more detailedevaluation of pretreatment optionsevaluation of pretreatment options


oo Membrane filtration was attractive, butMembrane filtration was attractive, butthe aggressive schedule did not allowthe aggressive schedule did not allowtime for the kind of piloting that successtime for the kind of piloting that successwith this alternative would requirewith this alternative would require

oo MWH recommended coagulation andMWH recommended coagulation andsedimentation followed by a single-sedimentation followed by a single-stage, deep bed filterstage, deep bed filter


oo The recommendation to include flocculationThe recommendation to include flocculationand sedimentation was based on:and sedimentation was based on: Historical information indicating the turbiditiesHistorical information indicating the turbidities

as high as 200 as high as 200 ntu ntu might be expectedmight be expected Coagulation has been shown to reduce organicCoagulation has been shown to reduce organic

foulantsfoulants As it turned out, the basins also play a criticalAs it turned out, the basins also play a critical

role in the control of role in the control of biofoulingbiofouling


oo The recommendation to use single-The recommendation to use single-stage, deep-bed filters was based on:stage, deep-bed filters was based on: Successful MWH experience with deepSuccessful MWH experience with deep

bed filtration in several conventionalbed filtration in several conventionalwater treatment plants of comparablewater treatment plants of comparablesize and largersize and larger

Results from MWHResults from MWH’’s filtration models filtration modelwhere SDI was assumed to track withwhere SDI was assumed to track withparticle counts and turbidityparticle counts and turbidity

MONTGOMERY WATSON FILTER MODEL Conventional Treatment Mode

Basic Input Data Clean bed Headloss= 0.26m 10.3in

Raw Particles, p/ml = 0.0E+00 Rate of headloss buildup = 0.16m/h 6.3 iph

Raw Turbidity = 2.0 Time to Breakthru 0.8hr

SS = 4 Time to headloss 23.2hr

Alum or ferric =3.0 UFRV = 24 m 601gal/sf

Filter rate, m/h =30 NWP = -74m/d -1,856gpsfdgpm/sf = 12.24 Final Particles = 3,130particles/ml

d_10 Anthracite, mm =2.00 Log[No/N] = 1.31Log Particle Removal

s.g. anthracite, g/cc = 1.70 Operating Turbity = 0.435ntuDepth top layer, m = 0.28571 Estimated SDI = 3.50

d_10, sand, mm = 1

s.g. sand, g/cc = 2.65 Simplified Model CalibrationDepth of middle layer = 0.14286 Purpose Default Your Coeff-

d_10 garnet, mm = 0.65 Value Value icient

s.g. garnet = 3.80 Incr t to brkthru 0.5 to 50 8.00 b

Depth of bottom layer = 0.07143 Reduce t to headloss 0.35 to 35 1.00 f

Design Head, m = 4.0 Incr final p/ml 0.4 to 40 0.40 k

Filter Aid, mg/L=0.000 Reduce final turb 2.5 to 10 2.50 p!Media Depth, m = 0.50 increase SDI 0.1 to 10 1.0 sdi

!L/d =253 * See Key equations below left

®R. Trussell 0.5

Montgomery Watson, 1993

MWH Filter ModelMWH Filter Model










d_10, sand, mm = 1








®R. Trussell 0.5


Basic input data to determine the load on the filter:Basic input data to determine the load on the filter:For direct filtration For direct filtration –– Particles or turbidity, and alum or Particles or turbidity, and alum orferric doseferric dose










d_10, sand, mm = 1








®R. Trussell 0.5


Basic input data to determine the load on the filter:Basic input data to determine the load on the filter:For complete treatment For complete treatment –– the SS in the clarified water the SS in the clarified water










d_10, sand, mm = 1








®R. Trussell 0.5


Design Data on the Filter: Filter rate, Size and depth of up Design Data on the Filter: Filter rate, Size and depth of up to three media layers, Total design headto three media layers, Total design head










d_10, sand, mm = 1








®R. Trussell 0.5


Performance Results: clean bed headloss, rate of Headloss buildPerformance Results: clean bed headloss, rate of Headloss buildup, time to turbidity breakthrough, time to limiting headloss,up, time to turbidity breakthrough, time to limiting headloss,UFRV, NWPUFRV, NWP










d_10, sand, mm = 1








®R. Trussell 0.5


Performance Results: also effluent particles, estimatedPerformance Results: also effluent particles, estimatedLog removal, effluent turbidity Log removal, effluent turbidity …… and SDI and SDI

Use of filter model to compareUse of filter model to comparepotential fouling with different designspotential fouling with different designs

Fouling of RO can be due to particulates,Fouling of RO can be due to particulates,but it is also due to organicsbut it is also due to organics

The filter model only estimates particulateThe filter model only estimates particulateremoval, so obviously it cannot addressremoval, so obviously it cannot addressorganic foulingorganic fouling

We decided to try and find a roughWe decided to try and find a roughcorrelation between SDI and particulatescorrelation between SDI and particulates

We used data on SDI and turbidity fromWe used data on SDI and turbidity fromAllison, (1987)Allison, (1987)

The relationship between NTU and The relationship between NTU andSDI used in the modelSDI used in the model

0

1

2

3

4

5

6

7

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Turbidity, NTU

SD

I Data of Allison, 1987Data of Allison, 1987

The relationship between NTU and The relationship between NTU andSDI used in the modelSDI used in the model

0

1

2

3

4

5

6

7

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Turbidity, NTU

SD

I Data of Allison, 1987Data of Allison, 1987

Model FitModel Fit

Having outfitted the model withHaving outfitted the model withits new its new ““SDI capabilitySDI capability”” we then we then

Examined some key filter design issuesExamined some key filter design issues

Depth of filter mediaDepth of filter media Diameter of filter mediaDiameter of filter media Filtration rateFiltration rate Adding a second stage Adding a second stage vs vs deep mediadeep media

An ObservationAn Observation

The model predicts The model predicts SDIs SDIs that are too low.that are too low. But we know it does a reasonable job ofBut we know it does a reasonable job of

predicting turbidity and particlespredicting turbidity and particles So we assume the trends we observe areSo we assume the trends we observe are

meaningfulmeaningful

Standard Dual MediaStandard Dual Media

In all this work we used In all this work we used MWHMWH’’s s standard approach tostandard approach tothe design of dual media:the design of dual media: Anthracite over sandAnthracite over sand Uniformity coefficient < 1.5Uniformity coefficient < 1.5 dd1010 anthracite = 2 x d anthracite = 2 x d1010 sand sand Anthracite depth = 2 x sand depthAnthracite depth = 2 x sand depth The size of the media is referred to by the size of the The size of the media is referred to by the size of the antrhaciteantrhacite

So 1.0 mm anthracite over 0.5 mm sand is So 1.0 mm anthracite over 0.5 mm sand is ““1.0 mm media1.0 mm media””

Model Results: media depthModel Results: media depth[diam. = 1 mm, rate = 15 m/h][diam. = 1 mm, rate = 15 m/h]

0

1

2

3

4

1 2 3 4 5 6 7

Depth of dual media, m

SD

I

0

1

2

3

4

1 2 3 4 5 6 7

Depth of dual media, m

SD

I

Performance improves with depth Performance improves with depthbut there is a diminishing returnbut there is a diminishing return

Model results: media diameterModel results: media diameter[dual media, rate 15 m/h, depth = 1 m][dual media, rate 15 m/h, depth = 1 m]

0

1

2

3

4

0.5 0.75 1 1.25 1.5 1.75 2

Diameter of top media, mm

SD

I

SDI increases as size increasesSDI increases as size increases

0

1

2

3

4

0.5 0.75 1 1.25 1.5 1.75 2


SD

I

Model results: filter rateModel results: filter rate[diam. = 1.2 mm, depth = 1 m][diam. = 1.2 mm, depth = 1 m]

0

1

2

3

4

5

5 10 15 20 25

Filter rate, m/h

SD

I

SDI increases with filter rateSDI increases with filter rate

0

1

2

3

4

5

5 10 15 20 25

Filter rate, m/h

SD

I

Dual media: Impact of depthDual media: Impact of depthand diameter on SDIand diameter on SDI

[filter rate = 15 m/h][filter rate = 15 m/h]

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

0.50

0.75

1.00

1.25

1.50

1.75

2.00

Overall depth of dual media, m

Diameter of top of

dual media mm

1.75

2.0

2.25

2.5

3.03.53.25

4.0 2.75



0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

0.50

0.75

1.00

1.25

1.50

1.75

2.00


Diameter of top of

dual media mm

1.75

2.0

2.25

2.5

3.03.53.25

4.0 2.75

ISOPLETHS OF ISOPLETHS OF EQUAL SDIEQUAL SDI

Note: as depth of media increases andNote: as depth of media increases andthe diameter of the media decreases, thethe diameter of the media decreases, theSDI also decreasesSDI also decreases

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

0.50

0.75

1.00

1.25

1.50

1.75

2.00


Diameter of top of

dual media mm

1.75

2.0

2.25

2.5

3.03.53.25

4.0 2.75



0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

0.50

0.75

1.00

1.25

1.50

1.75

2.00


Diameter of top of

dual media mm

1.75

2.0

2.25

2.5

3.03.53.25

4.0 2.75

conventional filterconventional filter[20 in 1 mm/10 in 0.5mm][20 in 1 mm/10 in 0.5mm]



0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

0.50

0.75

1.00

1.25

1.50

1.75

2.00


Diameter of top of

dual media mm

1.75

2.0

2.25

2.5

3.03.53.25

4.0 2.75

2 stage filter2 stage filter[20 in 1 mm/10 in 0.5mm][20 in 1 mm/10 in 0.5mm]22




0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

0.50

0.75

1.00

1.25

1.50

1.75

2.00


Diameter of top of

dual media mm

1.75

2.0

2.25

2.5

3.03.53.25

4.0 2.75

2 stage filter2 stage filter[20 in 1 mm/10 in 0.5mm][20 in 1 mm/10 in 0.5mm]22


deep bed filterdeep bed filter[60 in 1 mm/30 in 0.5mm][60 in 1 mm/30 in 0.5mm]

DecisionsDecisionsoo We proposed that we do a two stage design withWe proposed that we do a two stage design with

the first stage as a deep bed filterthe first stage as a deep bed filteroo During the design and early stages ofDuring the design and early stages of

construction we would do a one month pilot studyconstruction we would do a one month pilot studywith 4 in. pilot columnswith 4 in. pilot columns

oo Based on those pilot studies we would decide if aBased on those pilot studies we would decide if asecond stage of filtration would be justifiedsecond stage of filtration would be justified

oo If the deep bed performed as we expected, theIf the deep bed performed as we expected, theconstruction of the second stage would not beconstruction of the second stage would not benecessarynecessary

Pilot TestingPilot Testing

Raw Water During Pilot TestsRaw Water During Pilot Tests

Median Range Median Range

pHpH 7.57.5 7.0 - 8.27.0 - 8.2

TSS, mg/LTSS, mg/L 4.04.0 0.5 - 230.5 - 23

TDS, mg/L TDS, mg/L 25,400 21,100 - 29,80025,400 21,100 - 29,800

TOC, mg/LTOC, mg/L 3.83.8 3.0 - 5.83.0 - 5.8

u

First we examined theFirst we examined theeffect of media size andeffect of media size and

filter ratefilter rate

Conditions: Media Size TestsConditions: Media Size Tests

•• Coagulant dose: 15 mg/L ferric chlorideCoagulant dose: 15 mg/L ferric chloride•• Preoxidation with chlorine (0.1 - 0.5 mg/L free residualPreoxidation with chlorine (0.1 - 0.5 mg/L free residual

at end of sedimentation basin)at end of sedimentation basin)•• Filtration rate: 6 gpm/ftFiltration rate: 6 gpm/ft2 2 (14.7 m/hr)(14.7 m/hr)

Media Sizes TestedMedia Sizes Tested


Media Media One One

Media depth, inMedia depth, in 40/20 40/20 Media size, mmMedia size, mm 0.8/0.4 0.8/0.4

Media typeMedia type AnthAnth./sand ./sand


Media Media Media Media One Two One Two

Media depth, inMedia depth, in 40/20 60/30 40/20 60/30 Media size, mmMedia size, mm 0.8/0.4 1.0 / 0.5 0.8/0.4 1.0 / 0.5

Media typeMedia type AnthAnth./sand ./sand AnthAnth./sand ./sand


Media Media Media Media Media Media One Two Three One Two Three

Media depth, inMedia depth, in 40/20 60/30 60/3040/20 60/30 60/30 Media size, mmMedia size, mm 0.8/0.4 1.0 / 0.5 1.2/0.60.8/0.4 1.0 / 0.5 1.2/0.6

Media typeMedia type AnthAnth./sand ./sand AnthAnth./sand ./sand AnthAnth./sand./sand

0

0.01

0.02

0.03

0.04

NTU


Effect of Media Diameter: TurbidityEffect of Media Diameter: Turbidity

0.8 1.0 1.2

0

0.5

1

1.5

2

2.5

3

3.5

SDI


Effect of Media Diameter: SDIEffect of Media Diameter: SDI

0.8 1.0 1.2

Filter rateFilter rate

Conditions: Filter Rate TestsConditions: Filter Rate Tests


at end of sedimentation basin)at end of sedimentation basin)•• Media in all three filters:Media in all three filters:

•• Top: 60 in. of 1.0 mm anthraciteTop: 60 in. of 1.0 mm anthracite•• Bottom: 30 in. of 0.5 mm sandBottom: 30 in. of 0.5 mm sand

•• Filtration rates:Filtration rates:•• 4 gpm/sf (9.8 m/h)4 gpm/sf (9.8 m/h)•• 6 gpm/sf (14.7 m/h)6 gpm/sf (14.7 m/h)•• 9 gpm/sf (22 m/h)9 gpm/sf (22 m/h)

Effect of Filter Rate: TurbidityEffect of Filter Rate: Turbidity

0

0.01

0.02

0.03

NTU

Filter rate, gpm/sf

4 6 9

Effect of Filter Rate: SDIEffect of Filter Rate: SDI

0

0.5

1

1.5

2

2.5

3

SDI

Filter rate, gpm/sf

4 6 9

Effect of Filter Rate: UFRVEffect of Filter Rate: UFRV

0

5

10

15

20

25

30

35

40

UFRV

1000 gal/ft2-run

Filter rate, gpm/sf4 6 9

Effect of Filter Rate: UFRVEffect of Filter Rate: UFRV

0

5

10

15

20

25

30

35

40

UFRV1000 gal/run

Filter rate, gpm/sf4 6 9

Adding a second stageAdding a second stage

Conditions: Two-Stage TestsConditions: Two-Stage Tests



Conditions: Second Stage TestsConditions: Second Stage Tests

•• 15 mg/L ferric chloride15 mg/L ferric chloride•• Preoxidation with chlorine (0.1 - 0.5 mg/L free residualPreoxidation with chlorine (0.1 - 0.5 mg/L free residual


First First Stage Stage

Media depth, inMedia depth, in 60 / 3060 / 30 Media size, mmMedia size, mm 1.0 / 0.51.0 / 0.5 Media typeMedia type AnthAnth./sand./sand

Conditions: Second Stage TestsConditions: Second Stage Tests

•• 15 mg/L ferric chloride15 mg/L ferric chloride•• Preoxidation with chlorine (0.1 - 0.5 mg/L free residualPreoxidation with chlorine (0.1 - 0.5 mg/L free residual


First First Second Second Stage Stage Stage Stage

Media depth, inMedia depth, in 60 / 3060 / 30 40 / 20 40 / 20 Media size, mmMedia size, mm 1.0 / 0.51.0 / 0.5 0.8 / 0.4 0.8 / 0.4Media typeMedia type AnthAnth./sand./sand AnthAnth./sand./sand

0

0.01

0.02

0.03

0.04

NTU

First Stage Second Stage

Comparison of Deep Bed and Two StageComparison of Deep Bed and Two StageTurbidityTurbidity

0

0.5

1

1.5

2

2.5

3

3.5

SDI

First Stage Second Stage

Comparison of Deep Bed and Two StageComparison of Deep Bed and Two StageSilt Density Index, (SDI)Silt Density Index, (SDI)

Overall Summary of Pilot WorkOverall Summary of Pilot Work

•• Deeper Beds, Smaller Media and LowerDeeper Beds, Smaller Media and LowerFilter Rates all improve performanceFilter Rates all improve performance

•• Adding a second stage of filtrationAdding a second stage of filtrationfollowing a deep bed first stage did notfollowing a deep bed first stage did notimprove performance significantlyimprove performance significantly

•• Hence a second stage was notHence a second stage was notconstructedconstructed

Full-scale designFull-scale design

Plant LayoutPlant Layout

FlocculationFlocculationSedimentationSedimentation

Deep Bed Deep Bed FiltrationFiltration

11stst Pass PassRORO

Product Product WaterWater

StorageStorageCartridge Cartridge

FiltersFilters

High High ServiceServicePumpsPumps

22ndnd Pass PassRORO

HydrHydr. Flash . Flash MixMix Chem. Chem.

Storage Storage & Feed& Feed

CIPCIP

SludgeSludgedewateringdewatering

PowerPowerSubstationSubstation

Design SpecificationsDesign Specificationsoo Capacity of Capacity of preteatment preteatment system: 53 mgd (100,000 msystem: 53 mgd (100,000 m33/d):/d):

Ultimate 79 mgd (300,000mUltimate 79 mgd (300,000m33/d)/d)oo CoagulationCoagulation

oo Ferric chloride - pumped flash mixFerric chloride - pumped flash mixoo Cationic polymer - can be added at downstream turbulenceCationic polymer - can be added at downstream turbulence

oo FlocculatonFlocculatonoo 20 minutes20 minutesoo 3 stages of compartmentalization3 stages of compartmentalization

oo Axial flow impellersAxial flow impellersoo All impellers on All impellers on VFDsVFDsoo Max. design G = 80, 60, & 30 Max. design G = 80, 60, & 30 sec-1sec-1

oo Concrete baffles between stagesConcrete baffles between stages

Photos?Photos?

oo SedimentationSedimentation

oo Rectangular sedimentation basins with tubesRectangular sedimentation basins with tubes

Design Specifications (contDesign Specifications (cont’’d)d)

oo Detention time, 51 minutesDetention time, 51 minutesoo Overflow rate, 2 gpm/sf (4.9 m/h)Overflow rate, 2 gpm/sf (4.9 m/h)

oo Brentwood tubes, 2 ft deep, inclinedBrentwood tubes, 2 ft deep, inclined

Photos?Photos?

SedSed. basins under construction. basins under construction

Photos?Photos?Supports for tube bundlesSupports for tube bundles

Photos?Photos?Chain flights forChain flights forsludge collectionsludge collection

Design Specifications (contDesign Specifications (cont’’d)d)oo Single-stage, deep bed filtersSingle-stage, deep bed filters

oo MediaMediaoo Top, anthracite: 1.0 mm diam./60 in. depth (1524 mm)Top, anthracite: 1.0 mm diam./60 in. depth (1524 mm)oo Bottom, Silica sand: 0.5 mm diam./30 in. depth (762 mm)Bottom, Silica sand: 0.5 mm diam./30 in. depth (762 mm)

oo Filter rate, 6 gpm/sf (14.7 m/h)Filter rate, 6 gpm/sf (14.7 m/h)oo Hydraulic controlHydraulic control

oo Influent flow split via weirsInfluent flow split via weirsoo Effluent valve used to keep filter at constant submergenceEffluent valve used to keep filter at constant submergence

Trinidad and Tobago (2002)Trinidad and Tobago (2002)Operating filters Operating filters in wash modein wash mode

Cartridge FiltersCartridge Filters[18 vertical vessels -[18 vertical vessels -215 cartridges each]215 cartridges each]

View from belowView from below

5 5 µµm filter cartridgesm filter cartridges

First Stage of Reverse OsmosisFirst Stage of Reverse Osmosis

Water QualityWater Quality

Raw Water QualityRaw Water Qualityoo Salinity varies due to the influence of OrinocoSalinity varies due to the influence of Orinoco

RiverRiveroo ChlorinityChlorinity: 10.5 to 19.5 : 10.5 to 19.5 oo//oooo

oo TDS: 19.5 to 36 TDS: 19.5 to 36 oo//oooooo ““Standard SeawaterStandard Seawater””

oo Chlorinity Chlorinity = 19 = 19 oo//oooo

oo TDS = 35 TDS = 35 oo//oooo

oo Rest of mineral composition pretty much followsRest of mineral composition pretty much followsDittmar Dittmar (i.e. everything (i.e. everything αα chlorinitychlorinity))

oo TOC ~ 4 mg/LTOC ~ 4 mg/Loo Turbidity from 5 to 90Turbidity from 5 to 90

Raw Water TurbidityRaw Water Turbidity

TurbidityTurbidityntuntu

Percent of samples less than or equal toPercent of samples less than or equal to

OperationOperationandand

PerformancePerformance

Asian Green ClamsAsian Green Clamsoo Asian Green Clams are a constant worryAsian Green Clams are a constant worryoo These cause problems everywhere:These cause problems everywhere:

oo Tampa, Trinidad, Australia, Hong Kong, etc.Tampa, Trinidad, Australia, Hong Kong, etc.

oo Asian green clams are to sea life likeAsian green clams are to sea life likebermuda bermuda grass is to a garden ingrass is to a garden inSouthern CaliforniaSouthern California

oo i.e. you spend all your time i.e. you spend all your time ““rootingrootingthem outthem out””

oo At one point the clams were 6 feet deepAt one point the clams were 6 feet deepin the flocculation basinsin the flocculation basins

Asian Green ClamsAsian Green Clams

oo Desalcott Desalcott now controls the the clamsnow controls the the clamsusing shock chlorinationusing shock chlorinationoo Each day they add chlorine at plant inletEach day they add chlorine at plant inlet

until a residual comes through the until a residual comes through the flocflocbasinsbasins

oo Required dose 5 to 10 mg/LRequired dose 5 to 10 mg/L

Bio ControlBio Control

oo The basins were installed to address highThe basins were installed to address highturbidities from the Orinoco River but itturbidities from the Orinoco River but it’’s nows nowclear they play an essential role in control ofclear they play an essential role in control ofinvasive invasive sealife sealife as wellas well

oo In fact In fact Desalcott Desalcott maintains a generally aggressive programmaintains a generally aggressive programre. Biological growthre. Biological growth Goal is HPC = zero after cartridge filtersGoal is HPC = zero after cartridge filters And they meet that goalAnd they meet that goal Dr. Dr. Ramroop Ramroop is obsessed with bio controlis obsessed with bio control Shock Shock chlorinations chlorinations in the basinsin the basins Chlorine soakingsChlorine soakings

Deep bed filtersDeep bed filters Cartridge filtersCartridge filters

SDI of filtered waterSDI of filtered water

SDISDI


SDI of filtered waterSDI of filtered water

SDISDI


RecentRecentSDIsSDIs2 to 32 to 3}}

Full-scale ExperienceFull-scale Experienceoo Summary of key operating variablesSummary of key operating variables

oo Pretreatment:Pretreatment:oo Started out with 6 mg/L Ferric and 1 mg/L cationicStarted out with 6 mg/L Ferric and 1 mg/L cationic

polymerpolymeroo Resulted in Resulted in SDIs SDIs of 2.5 to 3.5+ and some ferricof 2.5 to 3.5+ and some ferric

breakthroughbreakthroughoo After several months of optimization have reducedAfter several months of optimization have reduced

ferric dose to 2.5 mg/Lferric dose to 2.5 mg/Loo Performance for past six months:Performance for past six months:

oo SDI 2 to 3SDI 2 to 3oo Filter runs 70 to 80 hoursFilter runs 70 to 80 hoursoo UFRVs UFRVs 25 to 29,000 gal/run25 to 29,000 gal/run


oo Cartridge filters (as of Mid March 04):Cartridge filters (as of Mid March 04):oo Change outs: Oct 02; Jan 03; Mar 03; Sep 03 Change outs: Oct 02; Jan 03; Mar 03; Sep 03oo Sep 03 Cartridges still in placeSep 03 Cartridges still in place ΔΔp p running ~ 6 psirunning ~ 6 psioo Change out criterion = 12 psiChange out criterion = 12 psioo DidnDidn’’t trust instrumentationt trust instrumentationoo Removed several filters to examine themRemoved several filters to examine them

oo Very clean, no staining, no bio-growth, nothingVery clean, no staining, no bio-growth, nothing


oo Membrane CIPMembrane CIPoo For the first ten months contract requirements left littleFor the first ten months contract requirements left little

capacity to spare:capacity to spare:oo They only did partial cleanings They only did partial cleaningsoo They put the membranes right back into serviceThey put the membranes right back into serviceoo They tolerated some increased pressure They tolerated some increased pressure

oo This January, a new train came on line leaving someThis January, a new train came on line leaving somespare capacity:spare capacity:

oo They They’’ve begun more thorough cleaningve begun more thorough cleaningoo TheyThey’’ve been experimenting:ve been experimenting:oo Longer soaks, different solutions and conditionsLonger soaks, different solutions and conditionsoo TheyThey’’ve made good progress, but they are still recovering ironve made good progress, but they are still recovering iron

off the membranes.off the membranes.

ConclusionConclusionoo Conservatively designed pretreatment usingConservatively designed pretreatment using

coagulation, sedimentation and deep bed filtrationcoagulation, sedimentation and deep bed filtrationadequately addressed the difficult pretreatmentadequately addressed the difficult pretreatmentsituation at Point situation at Point LisasLisas..

oo Our past experience has been that Our past experience has been that flocfloc././sedsed..basins can provide important flexibility andbasins can provide important flexibility andversatility for the operator of a versatility for the operator of a drinking waterdrinking watertreatment planttreatment plant

oo Now weNow we’’ve seen similar results in pretreatment forve seen similar results in pretreatment fora seawater desalination facility as wella seawater desalination facility as well

thanks for your patiencethanks for your patience

Design Specifications (contDesign Specifications (cont’’d)d)

oo Filter WashFilter Washoo Roberts Roberts Leotech Leotech TrilateralTrilateral™™ air/water air/water underdrainsunderdrainsoo Washwater Washwater troughstroughsoo Design wash sequence:Design wash sequence:

oo Filter until the water surface near top of mediaFilter until the water surface near top of mediaoo Apply Air and water, together until the surface approaches troughApply Air and water, together until the surface approaches trough

liplipoo Air at 3 Air at 3 scfmscfm//sf sf (180 m/h)(180 m/h)oo Water at 5 gpm/sf (12.2 m/h)Water at 5 gpm/sf (12.2 m/h)

oo Fluidize bed with water alone (approx. 5 Fluidize bed with water alone (approx. 5 mins mins @ 20 gpm/sf or@ 20 gpm/sf or48.9 m/h)48.9 m/h)

oo Single stage deep bed filter (continued)Single stage deep bed filter (continued)


oo Membranes:Membranes:oo First pass:First pass:

oo Toray SU-8320Toray SU-8320oo Running 7.6 Running 7.6 gfdgfdoo Conductivity ~ 400 to 500 Conductivity ~ 400 to 500 µµSSoo TDS ~ 250 to 275 mg/LTDS ~ 250 to 275 mg/L

oo Second pass:Second pass:oo Toray SUL-G20FToray SUL-G20Foo Running 12 Running 12 gfdgfdoo Conductivity ~ 40 to 50 Conductivity ~ 40 to 50 µµSSoo TDS 25 to 30 mg/LTDS 25 to 30 mg/L

oo Final product TDS ~ 35 to 40 mg/LFinal product TDS ~ 35 to 40 mg/L

Leopold Type SL and SLeopold Type SL and S

Roberts Roberts Leotech Leotech TrilateralTrilateral

Trinidad Seawater Reverse Osmosis Plantmosis plant

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