trinidad seawater reverse osmosis plantmosis plant
TRANSCRIPT
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
Background on ProjectBackground on Project
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
Background on ProjectBackground on Project
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
Background on ProjectBackground on Project
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
Background on ProjectBackground on Project
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
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
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
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
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
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
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
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
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
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
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
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
Diameter of top media, mm
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
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
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
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
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
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
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
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
conventional filterconventional filter[20 in 1 mm/10 in 0.5mm][20 in 1 mm/10 in 0.5mm]
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
2 stage filter2 stage filter[20 in 1 mm/10 in 0.5mm][20 in 1 mm/10 in 0.5mm]22
conventional filterconventional filter[20 in 1 mm/10 in 0.5mm][20 in 1 mm/10 in 0.5mm]
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
2 stage filter2 stage filter[20 in 1 mm/10 in 0.5mm][20 in 1 mm/10 in 0.5mm]22
conventional filterconventional filter[20 in 1 mm/10 in 0.5mm][20 in 1 mm/10 in 0.5mm]
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 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 Sizes TestedMedia Sizes Tested
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 Sizes TestedMedia Sizes Tested
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
Diameter of top media, mm
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
Diameter of top media, mm
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
•• 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)•• 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
•• 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)
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
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)
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
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)
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
Percent of samples less than or equal toPercent of samples less than or equal to
SDI of filtered waterSDI of filtered water
SDISDI
Percent of samples less than or equal toPercent of samples less than or equal to
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
Full-scale ExperienceFull-scale Experienceoo Summary of key operating variablesSummary of key operating variables
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
Full-scale ExperienceFull-scale Experienceoo Summary of key operating variablesSummary of key operating variables
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)
Full-scale ExperienceFull-scale Experienceoo Summary of key operating variablesSummary of key operating variables
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