Using a peat biobarrier to remediate PCE/TCE contaminated aquifers

Abstract

The industrial solvents tetrachloroethylene (PCE) and trichloroethylene (TCE) are among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this study was to evaluate the potential installation a peat biobarrier to clean up aquifers contaminated by PCE/TCE. Peat bioavailability was evaluated using a modified biochemical oxygen demand (BOD) test. Results show that biodegradable materials were released from peat and utilized by microbial consortia contained in the activated sludge. Degradation of the released organic materials caused the oxygen consumption and a slight decrease in chemical oxygen demand (COD) measurements. Based on the COD tests, 0.5 g of peat released approximately 6 mg of COD, which has the potential to convert 1.5 mg of PCE to ethylene (ETH). Microcosms inoculated with aquifer sediments or activated sludges were constructed under both aerobic and anaerobic conditions. Results indicate that peat can serve as the diffusion source of primary substrates, and enhance the PCE and TCE biodegradation under aerobic cometabolism and reductive dechlorination processes, respectively. Compared to the microcosms with aquifer sediments as the inocula, microcosms inoculated with sludges showed higher TCE/PCE degradation ratios (0.277 μM/day for TCE removal and 0.419 μM/day for PCE removal under aerobic and anaerobic conditions, respectively), and an immediate PCE/TCE decrease. These findings make the peat biobarrier containing sludge inocula more feasible and applicable from an engineering point of view. Results from the feasibility study show that the proposed peat biobarrier has the potential to become an environmentally and economically acceptable technology for the bioremediation of chlorinated-solvent contaminated groundwater.