Response of anaerobic membrane bioreactor to the presence of nano-BiWO: reactor performance, supernatant characteristics, and microbial community.

Considering the increasing incorporation of manufactured nano-material into consumer products, there is a concern about its potential impacts in biological wastewater treatment. In this study, the response of anaerobic sludge to the presence of BiWO nano-particles (NPs) was investigated in the anaerobic membrane bioreactor (AnMBR). As the concentration of BiWO in the reactor was controlled around 1 mg/L, there was no significant difference in effluent water quality or bacterial activities before and after NP exposure, partially due to the microbial-induced NP aggregation and stable complex formation. However, with the increasing dosage of BiWO from 5 to 40 mg/L, great influences on the AnMBR performance were observed, including the reduction of COD removal efficiency, inhibition of the mechanization step, increased production of soluble microbial products, and enhanced secretion of extracellular polymer substrates. Additional investigation with high-throughput sequencing was conducted, clearly demonstrating that BiWO NPs induced changes in the bacterial community.