Enhanced biodegradation of 1,1,1-trichloroethane under low biomass conditions

Biotransformation of 1,1,1-trichloroethane (TCA) by mixed bacterial communities, obtained from anaerobic digester sludge, under low concentrations of electron donors and microorganisms was performed at 35°C to assess the effect of substrate and concentration of microorganisms on the biotransformation rate of TCA. Humic acid (HA), acetate and glucose were selected to determine the suitability as electron donor with respect to the in-situ bioremediation of contaminated subsurface. The addition of electron donor and microorganisms was found to significantly enhance the biotransformation efficiency of TCA. Addition of electron donor resulted in increasing the cell numbers of anaerobic consortia, thereby increasing the rate of dechlorination. Glucose was found to be a better electron donor, as compared to acerate and humic acid, both in experimental results as well as thermodynamic calculations under reducing environments. Microbial concentration has been observed to be a dominant factor than electron donor in facilitating biodegradation of TCA. The pseudo-first-order rate constants of TCA ranged from 0.0023 per day to 0.0077 per day, depending on the nature of electron donor and biomass supplemented. Furthermore, addition of electron donor in low biomass input system resulted in enhanced efficiency as compared to that of high biomass input system.