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