An integrated system comprising coagulation, hydrolysis acidification, and multilevel contact oxidation was evaluated to make the dyeing effluent meet discharge standards. A new spiral biological carrier was first used in the treatment of dyeing wastewater. The chemical oxygen demand (COD), color, and biodegradability index (i.e., biological oxygen demand (BOD)/COD) of raw dyeing wastewater were 5051 mg/L, 404 times, and 0.29, respectively. During coagulation, 80% COD and 64% color were reduced with 80 mg/L polyaluminum chloride as coagulant. The hydraulic retention time (HRT) of subsequent hydrolysis acidification and multilevel contact oxidation was determined as 23.6 h. After the integrated treatment of coagulation–hydrolysis acidification–multilevel contact oxidation, COD, BOD, color, and ammonia removal efficiencies reached 98%, 99%, 92%, and 99%, respectively. The effluent met Class 1 discharge standards (GB4287-2012). In particular, the new spiral biological carriers used in multilevel contact oxidation led to significant total nitrogen (TN) removal. When the HRT of multilevel contact oxidation process was 16.4 h, the TN removal efficiency was 73.3%. The spiral carriers can provide an anoxic microenvironment in the inner part because of their high strength spiral structure, which facilitates the transformation from nitrate to nitrogen gas through simultaneous nitrification and denitrification. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 339–345, 2015
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