Impact of SRT on the efficiency and microbial community of sequential anaerobic and aerobic membrane bioreactors for the treatment of textile industry wastewater

The aim of this study is to evaluate the impact of SRT (infinite, 60 and 30 days) on the treatment and filtration characteristics of sequential anaerobic sulfate-reducing and aerobic sulfide-oxidizing MBRs treating textile wastewater. The influent COD, dye and sulfate concentrations were kept constant at 2000, 200 and 1000 mg/L, respectively. The decreased SRT caused substantial and partial decreases in COD oxidation and sulfate reduction, respectively, due to decrease of biomass concentration. Complete color removal was observed in the AnMBR and a slight increase in color was detected in the AeMBR. Sludge filterabilities were assessed with specific resistance to filtration, capillary suction time, and supernatant filterability tests. Compact and non-porous cake layer formed in the AnMBR. Metal-sulfide and Ca-P were detected in the cake layers of AnMBR and AeMBR, respectively, by SEM-EDS analyses. Desulfuromonas thiophila and Thioalkalivibrio sulfidiphilus were dominant sulfate-reducing and sulfide oxidizing bacteria in AnMBR and AeMBR, respectively.