1,1,2,2-Tetrachloroethane aerobic cometabolic biodegradation in slurry and soil-free bioreactors: a kinetic study

In this work the aerobic cometabolic biodegradation of 1,1,2,2-tetrachloroethane (TeCA) by propane-utilizing bacteria was studied in slurry bioreactors containing soil and groundwater from 5 aquifers as well as in soil-free bioreactors. The main goals were: a) to identify and calibrate a kinetic model of TeCA cometabolism; b) to select and characterize a TeCA-degrading bacterial consortium; c) to compare the results obtained in slurry and in soil-free bioreactors. The results showed that 4 of the 5 tested aquifers contain TeCA-degrading bacteria, indicating that aerobic cometabolism is a potentially effective approach for TeCA-contaminated aquifers. In bioaugmentation tests, a TeCA-cometabolizing consortium developed in the slurry bioreactors induced a strong reduction of the lag-time for the onset of TeCA cometabolism. The soil-free tests yielded a satisfactory TeCA degradation performance, indicating that on-site soil-free bioreactors represent an interesting technical solution for the aerobic cometabolic bioremediation of CAH-contaminated groundwaters. The mineralization of the organic Cl was equal to about 97%. The prolonged TeCA biodegradation determined a progressive selection of the bacterial strains more effective in TeCA degradation and less affected by degradation product toxicity. The tested Michaelis-Menten-based kinetic model proved an effective tool to interpret the experimental data of TeCA aerobic cometabolism.