Sequential Degradation of Chlorophenols by Photolytic and Microbial Treatment

Using the radiolabeled model pollutants 2,4-dichlorophenol (DCP) and 2,4,5-trichlorophenol (TCP) we demonstrated that brief UV (300-nm) photolysis greatly facilitates the removal of the two chlorophenols from sewage through accelerated mineralization and binding of polar products. The addition of 0.1 M H₂O₂ strongly accelerated the photolysis process resulting in half-lives of 1.68 and 0.87 min for DCP and TCP, respectively. In natural sunlight, half-lives of the chlorophenols were less than 1 day when H₂O₂ was present. During 4 days of incubation in activated sewage sludge, only 3% of unphotolyzed DCP and 1 % of unphotolyzed TCP were mineralized. Mineralization rose to79 and 59%, respectively, after photolysis in the presence of H₂O₂. Photolysis without H₂O₂ resulted in removal ofchlorophenols from solution chiefly by binding. Increased mineralization and binding were observed also upon incubationof photolyzed chlorophenols in soil. Disruption of carbon-halogen bonds by brief photolysis followed by traditional biological effluent treatment offers an alternative to activated charcoal treatmentfor removal of xenobiotics from industrial effluents.