Effect of Temperature on the Performance and Microbial Community Structure in an Integrated Anaerobic Fluidized-bed Membrane Bioreactor Treating Benzothiazole Wastewater

Abstract

An integrated anaerobic fluidized-bed membrane bioreactor (IAFMBR) was applied to treat synthetic high-strength benzothiazole wastewater. This study investigated the effect of temperature on the performance, membrane fouling and microbial community structure of IAFMBR. The results showed that decreasing temperature had an adverse effect on the performance and the cycle of membrane fouling. When temperature declined from 35℃ to 15℃, the COD efficiency dropped 7.4%, benzothiazole removal efficiency dropped 49.2%, the accumulation of total VFAs increased 225.66 mg·L-1, and methane yield (in CH4/CODremoved) dropped 0.118 m3·kg-1. The membrane fouling cycle shortened from 5.2 d to 2.5 d. For cake layer, the concentration of soluble microbial product (SMP) increased from 42.47 mg·L-1 to 70.62 mg·L-1, and the extracellular polymeric substance (EPS) content (in VSS) increased from 46.30 mg·g-1 to 82.22 mg·g-1 when the TMP was 15 kPa. For mixed liquor, the concentration of SMP increased from 36.46 mg·L-1 to 69.35 mg·L-1 and the EPS content increased from 47.47 mg·g-1 to 81.63 mg·g-1. Protein was the main component of EPS and SMP, and occurred in proportion of 80%.The microbial community structure showed that the dominant phyla were Firmicutes and Chloroflexi, which accounted for 42.6%-61.0% of the total relative abundance. The genera Clostridium (13.7%), Levilinea (15.2%), and Lactococus (17.9%) dominated with decreasing temperatures. The dominant methanogen was Methanosaeta.