The International Information Center for Geotechnical Engineers

Electrokinetic Remediation - Field setup and Implementation

 

Field Setup and Implementation

The field set up requires electrodes, power supply for supplying DC, wells, pumps and treatment units. The usually used electrodes are carbon, graphite, or platinum since they are inert and would not react in the process creating more contamination. The power supply is expected to deliver 1 A/sq. ft power between the electrodes. The power required to treat a cubic yard varies from 50 to 250 kWh. Ceramic wells are preferred to avoid corrosion during the process (Sharma and Reddy., 2004). Pumps are needed to remove the contaminated water from the wells. Treatment units are necessary to treat the contaminated water.

To make the remediation process cost effective the lowest possible voltage is used to meet the cleanup criteria. Field and pilot studies indicate that the voltage typically varies between 100 and 600 V and 15 and 50 A. the cost effectiveness also depends on the number of wells. Usual distances between the electrodes are 2 to 7 ft. It is sometimes ineffective in removing metals like mercury. This is due to the complex chemistry of the metal which does not allow it to be in solution as the soil chemistry changes (oxidation or reduction states) with remediation. Therefore for metals like mercury there is a need for enhancement methods to increase their solubility for successful removal and decontamination (Kornilovich et al., 2005). There are inexpensive ways to improve electrokinetic transport and chemical enhancement is one method. Enhancement solutions are used since the remediation causes premature precipitation. Ethylenediaminetetraacetic acid (EDTA), citrate and carbonate salts, sodium chloride and citric acids are used.

Upon completion of the installation system, the voltage is applied and enhancement solutions are introduced. The reservoirs are monitored to check for removal efficiency. The point where the system stops removal indicates the process is complete. In case the system no longer removes contaminant and still the target concentrations are not met then adjustments are made to the system. Electrode spacing can be decreased, more enhancement solution added or voltage can be increased.

The water near anode might get depleted since most contaminants move towards the cathode (Wieczorek,S., 2005). This could be overcome by replenishing the porewater adjacent to anode casing but never fully saturating it. Too much saturation might lead to extensive contamination in the soil resulting in more damage. 

 

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Figure 3: Water flux components during electrokinetic remediation in unsaturated soil (Wieczorek,S., 2005)

 

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