ABSTRACT & POWERPOINT PRESENTATION

Riverbed Filtration System Pilot Project

Adam Hutchinson Director of Recharge Operations Orange County Water District

Fountain Valley, California Managed Aquifer Recharge Symposium January 25-26, 2011 Irvine, California Symposium Organizers:

• National Water Research Institute • Orange County Water District • Water Research Foundation

www.nwri-usa.org/rechargesymposium2011.htm

The Orange County Water District Riverbed Filtration Pilot Project: Solids and Organic Carbon Removal Using Induced Riverbed Infiltration

Greg Woodside1, Adam Hutchinson2, Adam Canfield2, Jason Keller3, Michael Milczarek4, Scott Toland5

In an effort to reduce suspended solids and organic carbon loading and to increase long-term groundwater recharge rates at Orange County Water District’s spreading basins, a pilot project was conducted to evaluate riverbed filtration as a technology to treat Santa Ana River (SAR) water prior to groundwater recharge. Two-dimensional variably saturated flow modeling of a shallow under-channel lateral drain system coupled with pipe fluid flow calculations were used to guide the design of a riverbank filtration pilot project. Modeling was used to develop the design of a lateral drain collection system by varying drain diameters, spacing intervals, and placement depths in order to estimate the total lateral drain length required to achieve a pumping capacity of 4500 gallons per minute. A shallow under-channel lateral drain system was constructed within a channel adjacent to the SAR to induce riverbed infiltration and capture the increase in infiltrated water. Water captured from the riverbed drain system was recharged into test spreading basins and percolation columns to evaluate recharge rates compared to SAR water without treatment. At the pilot project system, subsurface phreatic levels and temperature were continuously monitored at thirteen points. River water inflow and outflow and drain system pumping rates were also monitored.

Pilot project system pumping was incrementally increased to establish the maximum pumping capacity of the drain system for two different test conditions. Water quality data indicate that riverbed filtration effectively removed all suspended solids and decreased dissolved organic carbon contents. The bulk of water captured by the under-channel drain system was from induced infiltration. The subsurface phreatic levels and groundwater movement within the pilot project area was very sensitive to changes in surface water flow rates and depth, and drain system pumping rates. The pilot test achieved a maximum pumping rate 40 % of that predicted by the model. The discrepancy between predicted and maximum collection capacity is believed to be due to actual groundwater elevations being lower than original model assumptions, and large variability in surface water depth over the system. Nonetheless, the model served as a valuable design tool and can be optimized with pilot study observations to support project scale up. The pilot project results indicate that riverbed filtration is a viable technology for treating surface water prior to recharge operations, however, additional testing and optimization is needed.

1 Orange County Water District, 18700 Ward Street, Fountain Valley, CA, 92708 2 Orange County Water District, 4060 E. La Palma Ave, Anaheim, CA 92807 3 GeoSystems Analysis, Inc., 16 Oak St, Suite 203, Hood River, OR 97031 4 GeoSystems Analysis, Inc., 2015 N. Forbes Blvd, Suite 105, Tucson, AZ 85745 5 HDR Engineering, 8690 Balboa Avenue, Suite 200, San Diego, CA 92123-1502"

Riverbed Filtration System Pilot Project

Managed Aquifer Recharge SymposiumJanuary 26, 2011

Adam Hutchinson1, Adam Canfield1, Michael Milczarek2, Jason Keller2, Scott Toland3

1Orange County Water District2GeoSystems Analysis, Inc3HDR

OCWD manages the groundwater OCWD manages the groundwater resources in north and central Orange resources in north and central Orange County. County.

• OCWD formed in 1933

• OCWD encompasses 350 mi2 in the lower watershed of the Santa Ana River (SAR)

• Orange County groundwater basin provides water for over 2.5 million people

Since 1936, OCWD has expanded Since 1936, OCWD has expanded its recharge system to over 25 its recharge system to over 25 facilities covering 1,500 acres. facilities covering 1,500 acres.

Source waters to the recharge system Source waters to the recharge system have changed over the years. have changed over the years.

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GWRSPurchased WaterMWD RechargeStorm Flow RechargeRecharged Base Flow

Solids loading has increased more than Solids loading has increased more than fivefive--fold since the 1960s due to the shift fold since the 1960s due to the shift to recharge of SAR water. to recharge of SAR water.

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Solid

s Lo

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harg

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stem

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s/ye

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MWD RechargeStorm Flow RechargeRecharged Base Flow

OffOff--River System

River SystemWarner BasinWarner Basin

Santa Ana River

Santa Ana River

Winter 2006Winter 2006

The Santa Ana River is currently the primary The Santa Ana River is currently the primary source of recharge water. source of recharge water.

Continual recharge with highly treated Continual recharge with highly treated wastewater (GWRS) has nearly tripled the wastewater (GWRS) has nearly tripled the recharge capacity of the basin. recharge capacity of the basin.

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fs)

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Average MWD

Average GWRS

SAR Recharge: 10,000 SAR Recharge: 10,000 afyafyGWRS Recharge: 27,000 GWRS Recharge: 27,000 afyafy

Concept is to use natural processes to Concept is to use natural processes to remove sediment and ultimately increase the remove sediment and ultimately increase the recharge capacity of the receiving basins.recharge capacity of the receiving basins.

Similar to bank filtration that is used in many places– Use riverbed as sand filter– Horizontal collector system may be more effective

than vertical systemBenefits– Increased recharge capacity of receiving basins

» Frees up recharge capacity of other basins– Silt is removed by river flow (no disposal issues)– Induce recharge in areas with low recharge rates– Other potential water quality benefits

Conceptual Profile of Collector Conceptual Profile of Collector Well Under OffWell Under Off--River and SARRiver and SAR

SAROff-River

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Ft bgs

15

65

95

Sand/Gravel

Sand

Silt/Clay

Desilted water to recharge basins

Pilot riverbed filtration system was Pilot riverbed filtration system was constructed to evaluate ability to constructed to evaluate ability to treat SAR water. treat SAR water.

Design elements: – Variably saturated flow model constructed to assist in design– Induce recharge (create more recharge into river)– Low tech, low cost (shallow drainfield) – 10 cfs capacity (4,500 gpm)

Pilot system constructed in Off-River Channel– Evaluate and monitor:

» Production capacity» Clogging rates» Shallow water level response (13 monitoring wells)» Induced recharge rates (Flow in – Flow out)

– Bi-weekly WQ samples of raw source and riverbed filtered water

– Percolation testing using raw water and riverbed filtered water to evaluate clogging

Test Period 1: Sheet FlowTest Period 1: Sheet Flow

Test Period 2: T&L PondsTest Period 2: T&L Ponds

System did not produce as much as System did not produce as much as expected due to lower water groundwater expected due to lower water groundwater levels. levels.

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Ft bgs

5

10 PrePre--test GW leveltest GW level

Most productive part Most productive part of system due to of system due to higher groundwater higher groundwater levels (fully levels (fully saturated)saturated)

Unsaturated conditions reduced Unsaturated conditions reduced capacity of this part of system. capacity of this part of system.

Sheet flow: 3 Sheet flow: 3 cfscfs (1,350 (1,350 gpmgpm))T&L Ponds: 4.5 T&L Ponds: 4.5 cfscfs (2,000 (2,000 gpmgpm))Induced Recharge: 80Induced Recharge: 80--100%100%

Weir 4Weir 4

GW level during GW level during testingtesting

Riverbed filtration provided significant Riverbed filtration provided significant improvements in water quality. improvements in water quality.

Parameter Influent Range

Avg. Reduction

Turbidity 8 - 80 NTU 96%

Total Suspended Solids (TSS) 7 - 37 mg/L >99%

Chlorophyll A 52 - 68 mg/M3 >99%

Total Organic Carbon (TOC) 6 mg/L 47%

Total Kjeldahl Nitrogen (TKN) 0.8 - 0.9 mg/L >99%

Iron 0.7 - 0.8 mg/L 80%

Manganese 0.06 mg/L >99%

Effect on percolation rate was measured in several ways.

Percolation Columns

Percolation Test Cells

Modified Fouling Index

Clogging with riverbed filtered water was Clogging with riverbed filtered water was significantly less than with SAR water. significantly less than with SAR water.

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0 20 40 60 80 100 120 140 160Time (hour)

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ent o

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latio

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Raw

Riverbed Filtration

7 hrs7 hrs

120 hrs120 hrs

Percolation Columns

SARSAR

The clogging potential of solids in The clogging potential of solids in riverbed filtered water is extremely low. riverbed filtered water is extremely low.

MFI TestRound 4 Testing

3/4/09

80180280380480580680780880980

0.00 0.50 1.00 1.50 2.00

TOTAL VOLUME (LITERS)

TIM

E/TO

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/LIT

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PassiveRawClothFloc-SedActiflo

1170

1300

270115

MFI = Modified Fouling IndexMFI = Modified Fouling Index

The pilot system will be expanded to The pilot system will be expanded to supply a small recharge basin. supply a small recharge basin.

Existing Riverbed Filtration System

Expanded System

Treated Water PipelineOlive Basin

The ultimate project would be constructed in The ultimate project would be constructed in the SAR channel. the SAR channel.

••5 miles of river channel5 miles of river channel••>200 acres of channel bottom>200 acres of channel bottom••Mostly selfMostly self--cleaningcleaning••No silt disposal issuesNo silt disposal issues••Gravity flow?Gravity flow?

Think Big or Go Home! Think Big or Go Home!

End of Presentation