Hexachlorobenzene dechlorination by indigenous sediment microorganisms.

Indigenous microbes from the sediments, whether contaminated with hexachlorobenzene (HCB) or not, could dechlorinate HCB effectively without any acclimation and supplemental nourishment. Temperature seriously affected the HCB-dechlorination: within the measured 15-45 degrees C span, the optimum range was between 30 and 35 degrees C. Sulfate-reducing bacteria (SRB), denitrifiers, and acetogens might not be directly involved in the HCB dechlorination. However, the SRB retarded subsequent dechlorination of pentachlorobenzene to tetra- and trichlorobenzenes. Some vancomycin-resistant gram-positive bacteria and methanogens were most likely to be the HCB-dechlorinators. The dechlorination followed the Michaelis-Menten behavior with the k'(m) and K(HCB) between 0.45-0.73 mg L(-1)day(-1) and 3.2-17.2 mg L(-1), respectively. These findings suggest a potential HCB treatment and cleanup for wastewater and contaminated site.