Dichloromethane is harmful to human health and hazardous to atmospheric environment. In this study, two strains were isolated which were identified as Pseudomonas sp. and Mycobacterium sp., and utilized dichloromethane （DCM） as sole carbon and energy sources. The optimal culture conditions were temperature of 28℃ and pH of 6.5 for obtaining the two mixed bacterial strains. The investigation on the purification of DCM-contaminated gas was carried out in a bench-scale biotrickling filter which was inoculated with the two strains and operated under these optimal conditions. The DCM removal efficiencies varied between 72% and 99% in the biotrickling filter when empty-bed residence time was 9.6 s with the inlet concentrations ranged fi＇om 0.7 to 3.12 g/m^3 under the conditions ofpH of 6.5 ±0.5 and temperature of 28℃. It was also found that NaCl accumulation in the broth would inhibit the DCM biodegradation dramatically when the accumulated NaCl concentration was over 35.1 g/L.
Response surface methodology （RSM） was employed to evaluate the optimum aerobic biodegradation of dichloromethane （DCM） in pure culture. The parameters investigated include the initial DCM concentration, glucose as an inducer and hydrogen peroxide as terminal electron acceptor （TEA）. Maximum aerobic biodegradation efficiency was predicted to occur when the initial DCM concentration was 380 mg/L, glucose 13.72 mg/L, and H202 115 mg/L. Under these conditions the aerobic biodegradation rate reached up to 93.18%, which was significantly higher than that obtained under original conditions. Without addition of glucose degradation efficiencies were ≤ 80% at DCM concentrations ≤ 326 mg/L. When concentrations of DCM were more than 480 rag/L, the addition of hydrogen peroxide did not help to significantly increase DCM degradation efficiency. When DCM concentrations increased from 240 to 480 rag/L, the overall DCM degradation efficiency decreased from 91% to 60% in the presence of HaO2 for 120 mg/L.
WU Shijin,YU Xiang,HU Zhihang,ZHANG Lili,CHEN Jianmeng College of Biological and Environmental Engineering,Zhejiang University of Technology,Hangzhou 310032,China
