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Electrokinetic Remediation - CASE STUDY 4: Creek bed, U.S Army Firing Range, Louisiana

 

CASE STUDY 4: Creek bed, U.S Army Firing Range, Louisiana

About the site:

The creek bed in U.S Army firing range in Louisiana was contaminated with lead. Lead poisoning occurs due to the accumulation of lead in body tissues. Prolonged exposure will lead to digestive problems, neurological problems, high blood pressure and kidney dysfunction (US EPA, 2001). In 1996, the Department of Defense supported the Small Business Innovative Research Program in Collaboration with WES, Electrokinetics, Inc. in carrying out a comprehensive study on the lead contaminated site. U.S EPA takes part in the result assessment from the study. The soils are contaminated with very high levels of lead and it reaches almost 4,500 mg/kg in some areas.

The table shows the Lead classification according to the contamination levels in ppm of soil. 

 

16.CASE4

Table 1: Classification of Lead Levels in Soils (University of Massachusetts, 1985)

  

Remediation and Results

A pilot-scale laboratory testing was done for the removal of 2000 mg/kg of lead from the kaolinite in 1993. The electrodes were placed one inch apart in the soil. The total soil specimen volume was about two tons and the process was carried out for four months. The total energy cost reached about $15 per ton. At the site of the study, Electrokinetics, Inc. was using CADEXTM electrode system that would promote contaminant transport to the cathode compartment. The contaminants are precipitated or deposited directly (US EPA, 1997). 

The removal efficiency was observed to be varying between 90 to 95%. The pilot scale studies showed that the lead concentrations decreased to less than 300 mg/kg within 30 weeks of processing. The toxicity leaching characteristic [TCLP] values dropped more than 300 mg/L to less than 40 mg/L within the same 30 weeks (US EPA, 1995).

Depending on soil type, the lead removal would vary. If the soil contains high amounts of Calcium or Magnesium then Lead is precipitated in groundwater and this would impact removal. Clays tend to show high bonding capacity and they slow the movement of contaminants. On the other hand, in clean silica or gravel, most of the minerals are removed and lead travels over longer distances easily (US EPA, 2001).

The results at the site are promising so far but full-scale efficiency or cost effectiveness have not been evaluated yet.   

 

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