Bio-removal of mixture of benzene, toluene, ethylbenzene, and xylenes/total petroleum hydrocarbons/trichloroethylene from contaminated water

Four pure cultures were isolated from soil samples potentially contaminated with gasoline compounds either at a construction site near a gas station in Fai Chi Kei, Macau SAR or in the northern parts of China (Beijing, and Hebei and Shandong). The effects of different concentrations of benzene, toluene, ethylbenzene, and three isomers (ortho-, meta-, and para-) of xylene (BTEX), total petroleum hydrocarbons (TPH), and trichloroethylene (TCE), when they were present in mixtures, on the bio-removal efficiencies of microbial isolates were investigated, together with their interactions during the bio-removal process. When the isolates were tested for the BTEX (50-350 mg/L)/TPH (2000 mg/L) mixture, BTEoX in BTEoX/TPH mixture was shown with higher bio-removal efficiencies, while BTEmX in BTEmX/TPH mixture was shown with the lowest, regardless of isolates. The TPH in BTEmX/TPH mixture, on the other hand, were generally shown with higher bio-removal efficiencies compared to when TPH mixed with BTEoX and BTEpX. When these BTEX mixtures (at 350 mg/L) were present with TCE (5-50 mg/L), the stimulatory effect of TCE toward BTEoX bio-removal was observed for BTEoX/TCE mixture, while the inhibitory effect of TCE toward BTEmX for BTEmX/TCE mixture. The bio-removal efficiency for TPH was shown lower in TPH (2000 mg/L)/TCE (5-50 mg/L) mixtures compared to TPH present alone, implying the inhibitory effect of TCE toward TPH bio-removal. For the mixture of BTEX (417 mg/L), TPH (2000 mg/L) along with TCE (550 mg/L), TCE was shown co-metabolically removed more efficiently at 15 mg/L, probably utilizing BTEX and/or TPH as primary substrates.