Technology:
Electrokinetic remediation
- System included an array of electrode wells, power supply and control system , monitoring system, process piping to distribute chemicals to and extract contaminants from electrode wells, and off-gas treatment system
- Electrode array consisted of a series of 24 anode and 14 cathode wells for two lagoons in the test cell; anode wells were 4 inch slotted PVC casings wrapped in linen fabric; anodes were rod-shaped and constructed of titanium with iridium oxide coating; cathode wells were 3-inch porous ceramic casings; cathodes were 2-inch wide strips of stainless steel mesh
- Citric acid was used as a soil amendment to enhance contaminant mobility
- Current density - 0.1 mA/cm2 for about 3 months; increased to 0.2 mA/cm2 in effort to raise contaminant movement; after six week shutdown to review project, current density further increased to 0.33 mA/cm2 with a corresponding decrease in the size of the treatment cell to one lagoon
- Prior to field demonstration, extensive laboratory testing was conducted to assess the potential effectiveness of electrokinetic extraction at the site; results indicated the technology could be successfully applied at the demonstration site
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Cleanup Authority:
Not identified
Technical Contacts:
Steve Granade
NAWS Point Mugu
Brian Harre
Naval Facilities Engineering Service Center |
Contaminants:
Heavy metals
- Surface sampling indicated chromium at up to 25,100 mg/kg (TCLP ND) and cadmium at up to 1,810 mg/kg (TCLP 10.5 mg/L) |
Waste Source:
Discharges from electroplating and metal finishing operations |
Type/Quantity of Media Treated:
Soil and Sediment
- Approximately 0.5 acres
- 85% sand, 7% gravel, 6% silt, and 1% clay
- pH of 5.84, TOC of 6,390 mg/kg, hydraulic conductivity of 0.045 cm/sec, cation exchange capacity of 3.9 |
Purpose/Significance of Application:
Demonstrate the use of electrokinetics for treatment of heavy metals in soil |
Regulatory Requirements/Cleanup Goals:
- Site target cleanup levels are State of California limits for chromium of <2,500 mg/kg and cadmium of 100 mg/kg |
Results:
- After 22 weeks of operation, contaminant reduction goals were not met; a pH front was just beginning to develop, with limited contaminant movement; the demonstration was suspended in October 1998
- Control of electrokinetically mobilized contaminants within the confined and unconfined treatment areas could not be assessed due to the poor performance of the technology.
- There was an increase in soil VOCs, primarily due to trihalomethane production resulting from Cl buildup in the anode wells
- The high chloride concentration of the groundwater was the main site characteristic that lengthened the time required to extract contaminants from the soil |
Cost Factors:
- Projected full-scale costs of $1,193/CY were extrapolated from the costs incurred for the field demonstration
- The total projected cost was $1,193,050 for treatment of 1,000 CY, consisting of $890,988 for capital and $302,062 for O&M |
Description:
Site 5 at NAWS Point Mugu was used for electroplating and metal finishing operations. Wastewater was discharges to unlined lagoons, resulting in soil and groundwater contamination at the site. A demonstration of electrokinetic remediation was performed from March to October 1998 to treat soil at the site. The demonstration was conducted by the U.S. Army Environmental Center (USAEC), Engineer Research and Development Center (ERDC); the Environmental Security Technology Certification Program (ESTCP) and Southwest Division, Naval Facilities Engineering Command.
The electrokinetic remediation system demonstrated consisted of a series of anode wells and cathode wells arrayed in the test cell. Citric acid was used as a soil amendment to enhance contaminant mobility. The initial current density applied to the system was increased after about three months of operation in an effort to increase contaminant mobility. The current density was further increased with a corresponding decrease in the size of the test area in additional efforts to increase contaminant mobility. However, after 22 weeks of operation, the pH front was just beginning to appear with limited contaminant removal; the demonstration was suspended in October 1998. The bench-scale tests did not accurately reflect the effects of site conditions on performance. A projected full-scale cost for use of the technology was estimated as more than $1,100/cubic yard of soil treated. |
