REMEDIATING SELENATE-CONTAMINATED GROUNDWATER WITH BIOBARRIERS CONTAINING BIODIESEL: LABORATORY EVALUATION

摘要

Selenate is in surface and groundwaters as a natural constituent and as a contaminant introduced by human activity. Laboratory studies were conducted to see if in situ biobarriers might be used to remove selenate from groundwater by its reduction to insoluble selenium (Seo). Biobarrier were formed by injecting an emulsion containing biodiesel onto sand filled columns. The biodiesel provides a carbon substrate that stimulates microbial activity. After the injection of the biodiesel emulsion, a soil wash was added to provide an inoculum of native microorganisms, and water containing 10 mg/L selenate was pumped through columns. Samples of the effluent water were collected at intervals and analyzed for selenate and selenite. Total amounts of selenate present in the effluent water decreased significantly but total soluble selenium in the column effluents decreased by only about 15-to16%. Increasing the length of the biobarrier failed to decrease the amount of soluble selenium in the effluent water. Biobarriers containing sawdust were also ineffective at removing soluble selenium compounds from flowing water during short-term studies. The results of this study suggest that permeable barriers containing biodiesel or sawdust may not be a very effective process for removing selenate or selenite from contaminated groundwater.