Enhanced treatment of composite industrial wastewater using anaerobic‐anoxic‐oxic membrane bioreactor: performance, membrane fouling and microbial community

Abstract

BACKGROUND: A laboratory-scale anaerobic-anoxic-oxic membrane bioreactor (AAO-MBR) system was used to remove organic compounds and nitrogen in the composite industrial wastewater collected from an industrial park. RESULTS:The recommended conditions for both chemical oxygen demand (COD) and nitrogen removal were as follows: hydraulic retention time of 73.6 h, sludge retention time of 35 days and mixed liquor return ratio of 300%. Under this condition, COD and total nitrogen removal efficiencies were 89.4% and 77.7%, respectively. After treatment, most organic compounds were removed, but there were still a few refractory organic compounds in the final effluent, such as 2-hydroxydesmethylimipramine, 1-dichloromethyl-3-methyl-benzene and N-phenyl-2,3-dichloromaleimide. Compared to carbohydrates, proteins in the extracellular polymetric substances accumulated more easily on the membrane surface, resulting in the membrane fouling. Ternary analysis at the family level indicated that the bacteria Desulfuromonadaceae, Rikenellaceae, and Spirochaetaceae were dominant in the anaerobic sludge, and played an important role in hydrolysis and fermentation. The abundance distributions of Nitromonadaceae, Caldilineaceae and Xanthomonadales were above 50% in the anoxic sludge, and these bacteria played an important role in denitrification. CONCLUSION:The results can provide valuable information for optimizing the operation of the AAO-MBR system for the treatment of composite industrial wastewater. Industry the anaerobic, anoxic and oxic membrane bioreactor (O-MBR) tanks were taken from the anaerobic, anoxic and oxic tanks in the CWWTP, respectively. Experimental setup and operational conditionsThe setup and operation of the laboratory-scale AAO-MBR system was similar to the CWWTP, and its schematic diagram is also shown in Fig. S1. The working volumes of the anaerobic, anoxic and O-MBR systems were 13.3, 13.0 and 16.0 L, respectively. A sedimentation reactor with a working volume of 20.0 L was set between the anaerobic reactor and the anoxic reactorNitrogen removal NH 4 + -N removal by the AAO-MBR system during the entire operation period is shown in Fig. 1(b). The NH 4 + -N concentration in