Specialized bacterial strains for the removal of dichloromethane from industrial waste

Abstract A flow-through process for the mineralization of dichloromethane was developed. To select a bacterial strain with a high degradation capacity for dichloromethane the growth properties of ten isolates were compared in batch and continuous culture. Growth rates varied between 0.01 and 0.11 h−1 and degradation rates were in the range between 0.05 and 0.86 g/1·h−1. Several strains were unable to grow on media containing 120 or 170 mM dichloromethane due to the high concentration of salt arising from the neutralization of the hydrochloric acid generated by the dehalogenation reaction. For all organisms the maximum growth rate decreased with an increase in substrate concentration. A fluidized bed reactor with sand particles as a carrier for cell immobilization was tested. The system was inoculated with a mixture of dichloromethane-degrading organisms and operated under non-sterile conditions. It exhibited a maximum degradation rate of 1.6 g dichloromethane/1·h−1 and was stable during long-time operation.