Degradation of 2,4,5-trichlorophenol and 2,3,5,6-tetrachlorophenol by combining pulse electric discharge with bioremediation

Degradation of 2,4,5-trichlorophenol (2,4,5-TCP) and 2,3,5,6- tetrachlorophenol (TeCP) was studied using a two-stage approach that utilized efficient pulse electric discharge (PED) followed by biological degradation with a consortium from acclimated return activated sludge. The chlorinated phenols were treated in the PED reactor as an aerosol at a voltage of 55-60 kV, a frequency of 385 Hz, a current of 50-60, and with a 200-ns pulse. As determined by gas chromatography and mass spectrometry (GC/MS), the first stage converted 500 ppm 2,4,5-TCP to 163 ppm 2,4,5-TCP and dimethyldecene, dichloronaphthalenol, octyl acetate, and silyl esters. The total carbon content of 2,4,5-TCP after PED treatment was determined to be 228 ± 35 ppm. The remaining 2,4,5-TCP and the products formed were then mineralized by the acclimated activated sludge in shake flasks; the initial rate of degradation of 2,4,5-TCP was calculated to be 5 nmol min^-1 mg protein^-1 at 163 ppm initial concentration (three orders of magnitude higher than the only rate found in the literature). By combining the two techniques, a synergistic effect (2.3-fold increase in the concentration of 2,4,5-TCP degraded and 3.3- fold increase in total carbon degraded) was observed, in that bacteria without any treatment degraded a maximum of 70 ppm 2,4,5-TCP but after PED treatment 163 ppm 2,4,5-TCP was degraded. TeCP was also mineralized by the acclimated activated sludge after treatment with PED. This two-stage approach was also evaluated using a continuous 1-1 fluidized-bed reactor.