Anaerobic biodegradability and toxicity of chlorophenols

Anaerobic biodegradation of several chlorophenol compounds under different conditions was studied. The experiments were carried out in batch and continuous processes and supplying or not an external carbon source. In the batch bioassays the observed reductive dechlorination with external carbon was greater than without external carbon source. The addition of the external carbon source stimulated the dechlorination, stabilized the process, and ensured the presence of sufficient amount of active biomass. The continuous process was evaluated in a fluidized bed reactor fed with synthetic wastewater containing 2,4,6-trichlorophenol (2,4,6-TCP) and acetic acid as primary substrate. Removal efficiencies of 2,4,6-TCP were larger than 80% at influent 2,4,6-TCP concentration of 25 mg/litre. No accumulation of lower chlorinated phenols was observed in batch or continuous processes, suggesting complete dechlorination. (C) 1999 Published by Elsevier Science Ltd on behalf of the IAWQ. All rights reserved.