Bioisomerization kinetics of gamma-HCH and biokinetics of Pseudomonas aeruginosa degrading technical HCH

Abstract

Bioconversion kinetics of gamma-HCH and biological growth kinetics of Pseudomonas aeruginosa degrading technical HCH was investigated in flask experiments under aerobic condition. Degradation studies for various isomers of technical HCH were also performed. The biodegradation of the most persistent beta\-HCH and delta-HCH isomers was also observed. At lower technical HCH concentrations (1-10mg/l), above 99% of the degradation was observed whereas at higher concentration (20-50 mg/l), the degradation efficiency was dropped. This may be due to inhibitory effect of technical HCH at higher concentrations. The technical HCH inhibitory behavior and bacterial growth kinetics could be correlated well by simple Haldane's growth kinetic model. The value of decay and yield coefficient was also determined. Further experimental results also revealed that degradation of the gamma-HCH isomer is faster (after incubation of 5 days) in the presence of other isomers of technical HCH, whereas gamma-HCH alone does not degrade even after a long period of incubation (14 days), but isomerizes to alpha-HCH isomer by the P. aeruginosa. The rate constant for the bioisomerization was found to be 0.0474 day(-1). The above estimated parameters (maximum specific growth rate, half saturation coefficient, inhibition constant, decay coefficient, yield coefficient and bioisomerization rate) are invariably required for the design and simulation of batch and continuous bioreactors treating HCH containing wastewaters. (c) 2007