Development of Biological Permeable Barrier to Treat Contaminated Groundwater Using PVA-Immobilized Cells

Passive biological permeable barriers that can be designed to degrade target contaminants in groundwater to harmless by-products and require almost very . low annual energy or labor input has obvious advantages over conventional pump and treat. This investigation developed and evaluated a biological permeable barrier medium designed to biodegrade 2,4,6 trichlorophenol (TCP) contaminated groundwater to harmless by-products under aerobic conditions. Polyvinyl alcohol (PVA) immobilized cells was selected as the medium for a series of column studies under a variety of operating conditions for 240 days to simulate a passive biological permeable barrier. PVA-immobilized cells were found to be a very good permeable barrier medium with a 100% – 91% TCP removal efficiency at loading up to 0.3–0.6 g L^–1 d^–1, respectively. In this study the removal efficiency of PVA-immobilized cells were tested under shock loads of TCP (>550 mg/L TCP) and deficiency of dissolved oxygen (DO<2 mg/L). PVA-immobilized cells were able to tolerate two 50 hours shock loads of 500 mg/L of TCP and resume their biodegradation activity. PVA-immobilized cells also tolerated two 50 hours of very low DO and continued to biodegrade TCP in the influent. This investigation showed cells entrapped within PVA were protected against high shock loads by immobilization and resumed their biological activity to the steady state in a matter of few days.