title: Mechanism for sludge acidification in aerobic treatment of coking wastewater.
abstract: This work was undertaken to investigate the cause of sludge acidification that led to disruption of the activated sludge process treating coking wastewater from a steel-making plant in Taiwan. An activated sludge reactor (ASR) with a working volume of 80 L was used as a model system to simulate the behavior of the real wastewater treatment process. Parameters that may cause acidification or inactivation of the sludge (NH(3), SCN(-), S(2)O(3)(2-) and CN(-)) were studied individually to examine for their effects on the performance of the ASR. The results show that high loading of NH(3), SCN(-) and CN(-) did not lead to pH decrease, while the ASR attained 85% COD removal and nearly 100% SCN degradation. In contrast, when the wastewater was supplemented with ca. 1,000 mg/L of S(2)O(3)(2-), the pH dropped to nearly 4.0 in 2 days and the COD and SCN removal yields were significantly lower (at 50 and 0-20%, respectively). Thus, overloading of S(2)O(3)(2-) was apparently a key factor causing sludge acidification. The results suggest that to ensure a normal functioning of the activated sludge, the influent S(2)O(3)(2-) concentration should be closely monitored and that the pH control of the ASR is indispensable when the S(2)O(3)(2-) loading is in excess.
authors.affiliation: Chemical Process & Water Treatment Section, Division of New Materials R&D, China Steel Corporation, Kaohsiung, Taiwan.
authors.forename: Yu-Mei
authors.initials: YM
authors.lastname: Chao
authors.forename: I-Cheng
authors.initials: IC
authors.lastname: Tseng
authors.forename: Jo-Shu
authors.initials: JS
authors.lastname: Chang
mesh_terms: D000143:Acids / Q000737:chemistry*; D000332:Aerobiosis; D003077:Coke / Q000032:analysis*; D003486:Cyanides / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D012722:Sewage / Q000032:analysis* / Q000737:chemistry* / Q000382:microbiology; D013455:Sulfur / Q000737:chemistry; D014865:Waste Disposal, Fluid / Q000295:instrumentation* / Q000379:methods*
chemical_list: D000143:Acids; D003077:Coke; D003486:Cyanides; D000644:Quaternary Ammonium Compounds; D012722:Sewage; D013455:Sulfur