Removal of mixture of cis-1,2-dichloroethylene/trichloroethylene/benzene, toluene, ethylbenzene, and xylenes from contaminated soil by Pseudomonas plecoglossicida

BACKGROUND: This study focused on the simultaneous removal of BTEX (benzene, toluene, ethylbenzene, and xylenes) and CAHs (chlorinated aliphatic hydrocarbons, represented by cis-DCE (cis-1,2-dichloroethylene) and TCE (trichloroethylene) mixture from soil, using an indigenous BTEX-adapted bacterium identified as Pseudomonas plecoglossicida. CAHs can be aerobically cometabolized by microbial oxygenases induced during the bacterial growth on such primary substrates as toluene and ortho-xylene. RESULTS: The bioremoval extent of BTEX/CAHs mixture varied, depending on the experimental conditions. As the ratio of BTEX to CAHs concentration was changed from 4 to 20, the bioremoval of both BTEX and CAHs decreased. The increase of initial BTEX concentration, from 200 to 1000 ppm, increased the microorganism lag phase and correspondingly prolonged the bioremoval process but decreased the bioremoval efficiency. The cometabolism of CAHs, when toluene and/or BTEX were provided as growth substrate, was significantly higher compared with other treatments without toluene. The BTEX/CAHs mixture removal between sterile and non-sterile soils revealed removal by the inoculant to be the major removal mechanism for the mixture. CONCLUSION: A mixture of BTEX, cis-DCE, and TCE in soil was simultaneously removed by P. plecoglossicida under aerobic conditions. The results obtained help to enhance the applicability of bioremediation technology to mixed wastes contaminated sites.