Biodegradtion of all three isomers of monochlorophenol in a fixed bed reactor to very low concentrations

An enriched mixed culture able to mineralize all three isomers of monochlorophenol (MCP) and a pure culture (Alcaligenes sp. A7-2) were used to inoculate a non-aerated fixed bed reactor filled with sintered glass beads. Oxygen was supplied in form of a 1% solution of H₂O₂. The 3 monochlorophenol isomers, added as a mixture (concentration of each compound 3.3 mgl⁻¹), were eliminated to over 99%. When the MCP concentrations were lowered to 1 mgl⁻¹ of each isomer, no addition of H₂O₂ was necessary since the oxygen concentration in the feed was sufficient for complete mineralization of the chlorophenols. Residual concentrations in the effluent of the reactor of below 0.2 μgl⁻¹ for 2-MCP, 0.05 μgl⁻¹ for 3-MCP and 4-MCP, respectively, were obtained. These values were also the detection limits for the three isomers. The low effluent levels were even obtained at hydraulic retention times of 0.7 h, which was reached stepwise. NO⁻₃ did not serve as an alternative electron acceptor to O₂.