Biodegradation of dichloromethane in waste water using a fluidized bed bioreactor

Summary

Biological treatment of a synthetic waste water containing 120 mM dichloromethane (10.2g/l) was carried out under aerobic conditions using dichloromethane-degrading bacteria as an inoculum. The bacteria were adsorbed to support particles and grown in a fluidized bed bioreactor. Charcoal and sand particles were compared as support materials with regard to abrasion, the maximum degradation rate for dichloromethane and the stability of the biological activity in the system.

The use of charcoal led to the incorporation of coal dust into the biomass and to an uncontrollable thickness of the biofilm. Therefore the system became unstable and the biological activity decreased. In contrast sand as support material was indifferent to abrasion and allowed biofilm thickness to be controlled. The dichloromethane degrading capacity of the bioreactor increased during the first 30 days. It reached a steady state level of 1.6 g CH₂Cl₂/lxh. Dichloromethane concentration in the effluent was <0.01 mM (<0.85 mg/l) and consequently the degradation efficiency better than 99.99%.