How microbial community and membrane biofouling respond to temperature changes in an anaerobic membrane bioreactor

Abstract

The temperature plays a key role in wastewater treatment by biological process in practical application because its changes directly influence physical, chemical and biological characteristics of activated sludge, especially under anaerobic conditions. However, there is little know that the effect of the temperature on microbial community and membrane biofouling in an anaerobic membrane bioreactor. An anaerobic membrane bioreactor was operated to investigate the effect of temperature on microbial community and membrane biofouling at 15, 25, and 35 °C. The respective chemical oxygen demand removal efficiencies at the temperatures were 85%, 93%, and 90%. In comparison with the mesophilic condition, the low temperature was able to worsen membrane biofouling (membrane fouling cycles changed to 8 d from 23 d when the temperature was decreased from 35 °C to 15 °C). The succession of microbial populations made the concentration of microbial metabolites increase gradually (EPS and SMP concentration reached to 48.3 mg/g and 33.2 mg/L from 38.3 mg/g and 23.6 mg/L when the temperature dropped to 15 °C from 35 °C), and it mainly caused membrane fouling. After slow-rising and steady-rising periods, the transmembrane pressure correlated positively with diverse microbial structures. At a rapid-rising stage of membrane fouling, the microbial community diversity decreased significantly. The transmembrane pressure correlated positively with diverse microbial structures, and the evenness of the microbial community (Gini coefficient) showed a significant correlation with membrane biofouling. This finding will help the practitioners to understand the mechanism of membrane biofouling under different temperature conditions, and to do the best to control the membrane fouling.