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EFFECTIVE REMOVAL OF TCE IN A LABORATORY MODEL OF A PRB CONSTRUCTED WITH PLANT MULCH
Citation:
WILSON, J. T. AND H. SHEN. EFFECTIVE REMOVAL OF TCE IN A LABORATORY MODEL OF A PRB CONSTRUCTED WITH PLANT MULCH. Presented at RTDF PRB Action Team Meeting, Charleston, SC, October 11 - 12, 2006.
Impact/Purpose:
To inform the public.
Description:
In the past ten years, passive reactive barriers (PRBs) have found widespread application to treat chlorinated solvent contamination in ground water. The traditional PRB commonly uses granular zero-valent iron and/or iron alloys as filling materials for treatment of chlorinated solvents. In recent years, there has been a surge in the price of iron. The higher price for iron makes alterative matrix materials for the PRBs more attractive. One alternative for iron is shredded plant mulch. As the plant mulch decays under anaerobic conditions, it provides substrate to bacteria that biologically dechlorinate the contaminants. Because the PRB functions like an in situ bioreactor, the PRBs constructed with plant mulch are often called biowalls. The biowall is constructed by excavating a trench across the plume perpendicular to ground-water flow, and then backfilling the trench with a mixture of woody plant tissue (such as shredded tree mulch and cotton gin trash) and sand to hold the plant tissue in place below the water table. Because it is a passive treatment system, a biowall requires no continuous and intensive input of energy for operation. Because the plant mulch for the biowall can often be acquired for the cost of transportation to the site, the construction of a biowall is much less expensive than an iron PRB, and is generally much less expensive than conventional approaches such as pump and treat. The results suggest that the plant mulch biowall may be an efficient and cost-effective method to control ground water contaminated by chlorinated solvents.