Degradation of Technical Grade Hexachlorocyclohexane In Soil Slurry by a Defined Microbial Consortium

Hexachlorocyclohexane, an organochlorine insecticide has been used in agriculture and public health programmes since a very long time. It is very resistant to degradation and thus accumulates in the environment for long time. A microbial consortium was developed in our laboratory which could degrade Hexachlorocyclohexane very efficiently in water. A study was carried out to understand the biodegradation of technical grade hexachclorocyclohexane (HCH) in soil slurry in lab scale bioreactor by a defined bacterial consortium under aerobic conditions. Effects of parameters such as initial HCH concentration and volume of air required were optimized. 10 and 25 ppm of HCH were degraded completely by 120 and 168 h, respectively. No lag was observed. In both the concentrations of HCH, gamma -isomer was degraded faster and -and, beta- isomers took more time for degradation. The rate of degradation of alpha,beta, gamma and delta isomers of 10 and 25 ppm HCH were 0.0186, 0.0136, 0.0179, 0.0176 mg/L/h and 0.0122, 0.01444, 0.0126, 0.0122 mg/L/h respectively. Aeration rate of 0.5 vvm gave maximum degradation, whereas at 1.0 vvm delta-isomer was not degraded completely. At 2.0 vvm aeration, all the isomers remained even after 144h if incubation.