Effects of temperature and temperature shock on the performance and microbial community structure of a submerged anaerobic membrane bioreactor (SAnMBR) treating thermomechanical pulping pressate were studied for 416 days. The results showed that the SAnMBR system were highly resilient to temperature variations in terms of chemical oxygen demand (COD) removal. The residual COD in treated effluent was slightly higher at 55 degrees C than that at 37 and 45 degrees C. There were no significant changes in biogas production rate and biogas composition. However, temperature shocks resulted in an increase in biogas production temporarily. The SAnMBR could tolerate the 5 and 10 degrees C temperature shocks at 37 degrees C and the temperature variations from 37 to 45 degrees C. The temperature shock of 5 and 10 degrees C at 45 degrees C led to slight and significant disturbance of the performance, respectively. Temperature affected the richness and diversity of microbial populations. (C) 2011 Elsevier Ltd. All rights reserved.