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[摘要]：The effects of oxygen availability on the degradation of pentachlorophenol (PCP) by coupled sludge granules and the granules' physicochemical characteristics were studied in batch experiments. Results indicated that the quantity of available oxygen in serum bottles had a significant effect on the metabolism of PCP. The mass balance analysis of various intermediates (chlorinated phenols and release of chloride ion) indicated that reductive dechlorination was the pathway for the PCP degradation under the studied conditions. The highest degree of mineralization of PCP (95%) was achieved at 40% initial headspace oxygen percentage (IHOP), producing trichlorophenol (TCP), dichlorophenol (DCP), and monochlorophenol (MCP) as the intermediates and chloride as one of the final products in a 3-day incubation period. Under strictly anaerobic or slightly oxidative conditions (0 and 20 IHOP), the reductive dechlorination of PCP caused an accumulation of TCP. Under aerobic conditions (80 and 100 IHOP), PCP degradation was less significant due to the hindered reductive chlorination in the presence of excess oxygen. A positive correlation exists among hydrophobicity, settling velocity, and protein (PN) concentration. The hydrophobicity and PN decreased from 85%, 3.5 mg g(-1) VSS to 70%, 1.3 mg g(-1) VSS as IHOP increased from 0 to 60, and then increased to 82%, 2.8 mg g(-1) VSS as IHOP increased to 100. Oxygen-limited conditions caused an inferior settling characteristic of the granules. Because of a combination of reductive and oxidative degradation mechanisms, aerobic or facultative bacteria were found to oxidize the PCP degradation intermediates produced by methanogens during the metabolism. (C) 2009 American Institute of Chemical Engineers Environ Prog, 29: 307-312, 2010 |
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