Anaerobic Transformation of β-Hexachlorocyclohexane by Methanogenic Granular Sludge and Soil Microflora

Abstract

β-Hexachlorocyclohexane (β-HCH) was microbiologically transformed under anaerobic conditions by methanogenic granular sludges from upflow anaerobic sludge blanket (UASB) reactors fed with methanol, volatile fatty acids (VFA), or sucrose as substrates. These sludges, which had not priorily been exposed to β-HCH transformed β-HCH to benzene and chlorobenzene. Usually 2-3 times as much benzene as chlorobenzene was formed. The transformation rates ranged from 0.37 to 0.46 β-HCH (g of volatile suspended solids (VSS)) -1 day -1 at 30 °C. β-HCH was not transformed by autoclaved (sterile) sludge, indicating the biotic nature of the reaction. βand also R-HCH present in contaminated soil were both found to be converted to chlorobenzene and benzene upon incubation of the soil under anaerobic conditions. Equal amounts of benzene and chlorobenzene were formed. The results show that β-HCH transforming bacteria are present in different anaerobic environments. This finding may be of importance for the application of anaerobic bioremediation on sites contaminated with HCH isomers.

Bioremediation of Hexachlorocyclohexane Contaminated Soil: Field Trials

“…However, reduction of 13 mg kg -1 day -1 was obtained under methanogenic conditions. Van Eekert et al (1998) have reported the removal of -HCH from a sandy soil containing low concentration of the isomer in slurries where lactate or sulfide had been added to reduce redox potential. Degradation of HCH was faster under anoxic conditions and that microbial degradation was primary route of HCH disappearance from soil (MacRae et al, 1967).…”

Biochemistry of Microbial Degradation of Hexachlorocyclohexane and Prospects for Bioremediation

“…Most studies of anaerobic HCH degradation reported the accumulation of chlorobenzene and benzene (24,98,179), although Quintero et al (140) detected only traces of these metabolites, and Jagnow et al (64) reported the complete degradation of ␥-HCH at least to chloride and chloride-free metabolites in mixed and pure cultures of Clostridium species. There have been other reports of the anaerobic mineralization of benzene (41,147), but we are unaware of other reports of the anaerobic degradation of chlorobenzene.…”

Application of zerovalent iron (Fe0) to enhance degradation of HCHs and DDX in soil from a former organochlorine pesticides manufacturing plant

“…2). The percentage degradation of b-HCH is less than , 1990;Johri et al, 1998;Van Eekert et al, 1998). HCH biodegradation was initially thought to be an anaerobic process (Sethunathan et al, 1983;MacRae et al, 1984) and reductive dechlorination of the four commonly found HCH isomers (a-, b-, c-, d-HCH) had been observed under anoxic conditions in soil microcosms (Jagnow et al, 1977), soil slurries (MacRae et al, 1984) and pure cultures (Jagnow et al, 1977).…”

“…Many pesticides, such as b-HCH and DDX are normally considered persistent in aerobic environments, are not persistent under anaerobic conditions (Aislabie et al, 1997;Van Eekert et al, 1998). Therefore, generating a reduced environment in water, soils and sediments may facilitate the degradation of organochlorine pesticides (OCPs) (Satapanajaru et al, 2006).…”