Robustness of granular activated carbon-synergized anaerobic membrane bioreactor for pilot-scale application over a wide seasonal temperature change

A novel granular activated carbon-synergized anaerobic membrane bioreactor (GAC-AnMBR), consisted of four expanded bed anaerobic bioreactors with GAC carriers and a membrane tank, was established in pilot scale (10 m3 /d) to treat real municipal wastewater (MWW) at ambient temperature seasonally fluctuating from 35 to 5 degrees C. It showed sound organic removal over 86% with the permeate COD less than 50 mg/L even at extremely low temperatures below 10 degrees C. COD mass balance analysis revealed that membrane rejection (with a contribution rate of 10%-20%) guaranteed the stable organic removal, particularly at psychrophilic temperature. The methane yield was over 0.24 L CH4 (STP)/g COD (removed) at mesophilic temperature and 0.21 L CH4 (()(STP)())/8 COD removed at 5-15 degrees C. Pyrosequencing of microbial communities suggested that lower temperature reduced the abundance of the methane producing bacteria, but the methane production was enhanced by selectively enriched Methanosaeta, syntrophic Syntrophobacter and Smithella and exoelectrogenic Geobacter for direct interspecies electron transfer (DIET) on the additive GAC. Compared with previously reported pilot-scale AnMBRs, the GAC-AnMBR in this study showed better overall performance and higher stability in a wide temperature range of 5-35 degrees C. The synergistic effect of GAC on AnMBR guaranteed the robustness of GAC-AnMBR against temperature, which highlighted the applicational potential of GAC-AnMBR, especially in cold and temperate climate regions. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

A novel GAC-AnMBR was established to treat real municipal wastewater with sound organic removal efficiency at both high and low temperatures. The membrane rejection and microbial communities analysis revealed the mechanisms behind the stable organic removal even under extreme temperature conditions. The synergistic effect of GAC on AnMBR ensured the robustness of GAC-AnMBR against temperature variations, showcasing its potential in cold and temperate climate regions.