Ex Situ Advanced Oxidation Processes, Granular Activated Carbon, and Synthetic Resin Adsorption Treatment at the Charnock Wellfield

Site Name:

Charnock Wellfield


Santa Monica, California

Period of

July 1998 - April 1999


Pilot scale

AOP - UV/Peroxide and UV/Peroxide followed by GAC
- UV/Peroxide - system included a Calgon Rayox™ tower configured for upflow operation equipped with three UV lamps that operatd at 23.5 kilowatts (kW). Peroxide dosing resulted in peroxide concentrations of 20 to 60 mg/L. Water retention times for the tower were 2 to 4 minutes for flow rates of 150 to 300 gpm, respectively. To prevent scaling, groundwater was pre-treated by filtration.
- UV/Peroxide followed by GAC - effluent from the Rayox™ tower was treated using three 2,000 pound vessels containing Calgon Carbon's Centaur carbon to remove residual peroxide followed by three 2,000 pound vessels containing Calgon Carbon's Fitrasorb 300 carbon to remove residual MTBE and by-products.
- UV/Peroxide followed by GAC - Operated in Parallel - three types of GAC units operated in parallel - Calgon Carbon's Centaur carbon, Calgon Carbon's Fitrasorb 300, and coconut shells. Each 2,000 pound unit contained an upflow column (12 inches in diameter and 8.5 feet in length) and a downflow column (8 inches in diameter and 8.5 feet in length). The flow rate was 2 gpm through each of the units.

Cleanup Authority:
State of California

Site Contact:
Gil Borboa
City of Santa Monica
Utilities Division
1212 5th Street, 3rd Floor
Santa Monica, CA 90401
Telephone: (310) 458-8230
Fax: (310) 393-6697
E-mail: Gil-borboa@ci.santa-monica.ca.us

EPA Contact:
Steve Linder
U.S. EPA Region 9
75 Hawthorne Street, WST-8
San Francisco, CA 94105
Telephone: (415) 744-2036
Fax: (415) 744-1026
E-mail: linder.steven@epa.gov
Craig E. Dial, P.E.
Kennedy/Jenks Consultants
2151 Michelson Drive, Suite 100
Irvine, CA 92612-1311
Telephone: (949) 261-1577
Fax: (949) 261-2134
E-mail: CraigDial@KennedyJenks.com


Waste Source:
Leaks from gasoline pipelines and underground storage tanks

Type/Quantity of Media Treated:
Drinking Water

Purpose/Significance of Application:
Pilot-scale testing of Advanced Oxidation Processes (AOP) to treat MTBE and TBA in drinking water

Regulatory Requirements/Cleanup Goals:
The target MTBE treatment goal for the Charnock Treatment Plant is 13 ug/L; risk-based drinking water action level established by the California Department of Health Services for chemicals for which primary MCLs have not been adopted.

- At the time of this report, only limited data were available on MTBE concentrations in the effluent from the UV/peroxide process Rayox™ tower.
- According to the PRP's consultant, one reported value for MTBE in the Rayox tower effluent was below the detection limit of 3 ug/L, based on an influent MTBE concentration of 80 ug/L. In addition, tests run with MTBE-spiked water at 1,000 ug/L and a flow rate of 210 gpm reduced MTBE effluent concentrations to 2 to 4 ug/L.

Cost Factors:
Projected capital equipment cost for a proposed full-scale UV/peroxide system is approximately $4 to $5 million, including four 1,200-gpm Rayox™ towers equipped with 24 30-kW UV lamps. This cost does not include installation, purchasing suitable property (approximately 40,000 square feet), or installing a pipeline between Arcadia and Charnock (estimated at $1 million per mile).
- Operating costs of the full-scale system are estimated to be $1.50 to $1.75 per 1,000 gallons of treated water.

The Charnock Sub-basin, located in the Mar Vista section of West Los Angeles, includes the Upper Silverado aquifer containing two municipal wellfields. In March 1996, MTBE was detected in drinking water at the Charnock Wellfield. MTBE concentrations in groundwater ranged from 130 micrograms per liter (ug/L) to 610 ug/L. In August 1998, tertiary butyl alcohol (TBA) was discovered in the shallow groundwater near the Charnock Wellfield. Two intrastate gasoline pipelines and 24 underground storage tank sites have been identified as possible sources of the groundwater contamination. The potentially responsible party (PRP) group's engineering consultant, Kennedy/Jenks (KJ), began pilot studies to evaluate treatment technologies for the removal of MTBE and TBA.

Pilot testing was conducted on UV/peroxide, UV/peroxide followed by GAC units operated in series, and UV/peroxide followed by three sets of GAC units operated in parallel. Limited data available at the time of this report showed MTBE concentrations below the detection limit of 3 ug/L in the effluent from the UV/peroxide process Rayox™ tower, and MTBE effluent concentrations reduced to 2 to 4 ug/L during tests run with MTBE-spiked water at 1,000 ug/L A 3,500 gpm treatment system is proposed for construction if the pilot studies find that the UV/peroxide system is technically feasible and cost effective. The projected capital costs for a full-scale system are $4 to $5 million, with operation costs of $1.50 to $1.75 per 1,000 gallons of water treated.