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Water Quality Impacted by External Events in the Demonstration-Scale Under-Ocean Floor
Seawater Intake System
Yan Zhang, Tai J. Tseng, Robert C. Cheng, and Kevin L. WattierNov 15th, 2011
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2011 Water Quality Technology ConferencePhoenix, AZ
Presentation Outline
Project Overview and ApproachDemonstration Scale Research and Findings
• Flow Data• Water Quality
Conclusion• Findings• Future Work
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Presentation Outline
Project Overview and ApproachDemonstration Scale Research and Findings
• Flow Data• Water Quality
Conclusion• Findings• Future Work
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Seawater Desalination Program
Post treatment / DistributionPretreatment Intake/Discharge
NF2 or RO
A $20 M, 10-year investment Leverage various partnerships for technical input and other supportFederal/State/Local Funds, 50% funding by Reclamation
•$5 M Project($2 M DWR)
•Prototype•UV/ClO2
•Mitigation of WQ impacts due to integration of new source
Open Ocean IntakeSubsurface Intake
Horizontal/Directional DrillingVertical Beach WellInfiltration Gallery (LBWD method)
Types of Intake Systems
Demonstration Site Layout
Discharge Area ~2000 ft2
Infiltration Area ~3100 ft2
Cross Section of Intake Gallery
View at Low Tide
Construction
System Layout
Filter Effluent delivered to
Wet-well
Raw Seawater
To Discharge Gallery
Cartridge Filtration and
Membrane
Cartridge Filtration
Research ObjectivesTechnical
Can we sustain water quantity?• Determine the maximum sustainable intake filtration
and discharge rateWhat is the water quality and how does it compare to Microfiltration?• Determine the additional treatment benefits provided
by the intake system
EnvironmentalImpingement/entrainment• Federal Clean Water Act, Section 316 (b)
Discharge• Brine dispersion
Yield InvestigationInvestigate Infiltration Rates of 0.05, 0.10, and 0.15 gpm/ft2.
Water Quality MonitoringContinuous online filtrate monitoringWeekly/Bi-weekly raw, filtrate and post CF microbial, general physical grab monitoringIntensive 30 day monitoring for external events’ impacts
Research Approach
Presentation Outline
Project Overview and ApproachDemonstration Scale Research and Findings
• Flow Data• Water Quality
Conclusion• Findings• Future Work
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Flow through system(Jun '08- Oct '08, 155 gpm-0.05 gpm/ft2)
Flow through system(Oct '08- Mar '09, 310 gpm-0.1 gpm/ft2)
Flow through system(Apr '09- Jun ‘10, 233 gpm-0.15 gpm/ft2)
Flow through system(Sep ‘10- Oct ‘11, 465 gpm-0.15 gpm/ft2)
What’s Causing the Shut Downs?System design
Filter Gallery SizeEngineered sand permeability
Tidal conditionsLow tide levels? Shut downs not consistently occuring at low tide levels
Temperature-changing water permeabilityRaw Water Quality?
Very frequent shut downs occurred in Nov/Dec heavy rain season, caused by deteriorated water clogging filter bed?
Water Production Summary
Presentation Outline
Project Overview and ApproachDemonstration Scale Research and Findings
• Flow Data• Water Quality
Conclusion• Findings• Future Work
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WQ Improved with Time
WQ Improved with Time
WQ Impacted by External EventsRainSewer SpillRed TideTidal Levels
Impacts of Rain on Total Coliform
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Impacts of Sewer Spill
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Impacts of Red Tide
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Impacts of Tide Levels
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Impacts on Turbidity
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Impacts on TOC
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Impacts on Conductivity
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Water Quality SummaryWater quality improves with timeHeavy rain and sewer spill increased microbial levels in raw seawater, but no clear impacts observed with red tide events and different tide levelsThe filtration system was effective in removing raw water microbial levels spikes during rain and sewer spill eventsHeavy rain, red tide and sewer spill all increased raw seawater turbidityRed tide increased raw seawater TOC levelsHeavy rain decreased raw seawater conductivity
Presentation Outline
Project Overview and ApproachDemonstration Scale Research and Findings
• Flow Data• Water Quality
Conclusion• Findings• Future Work
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Findings
Water Quantity:The system can produce a sustained capacity up to a flow rate of 465 gpm (infiltration rate of 0.15 gpm/ft2)
Water Quality:System product water quality improves with timeExternal events can impact raw seawater quality, however, this impact was removed by the system
Future WorkContinue testing on current and higher infiltration rates and investigate hydraulic profile to improve system capacityMembrane Testing
AcknowledgementLong Beach Water Department’s staff, Cynthia Andrews-Tate, Ana Flores, and Eric Mintz for conducting the laboratory workCA Department of Water Resources and the US Bureau of Reclamation for partial funding of this project Technical Advisory Committee: Dr. Steve Duranceau, Steven Hubbs, and Gary Logsdon
www.lbwater.org
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Questions