A submerged anaerobic membrane bioreactor (SAMBR) combining anaerobic digestion and membrane separation has recently attracted attention, because of its potential to recover methane and reduce sludge production in wastewater treatment. In this study, a lab-scale SAMBR that treats suspended solids containing synthetic sewage was continuously operated for 106 days at room temperature (25℃) to investigate the effect of hydraulic retention time (HRT) on its treatment performance and microbial

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... ity. HRT was changed from 48 to 6 hours in 4 steps. At HRT of 12 hours, the chemical oxygen demand (COD) and biochemical oxygen demand removal rates were 94%, and 95% respectively, and 64.6% of input COD was converted to methane. On the basis of the results of cloning analysis, Methanosaeta and Methanoregula were found to be the two dominant Archae a genera, in the reactor. In the clone library of Bacteria , many unclassifi ed bacteria have been detected, and about 21% of facultative anaerobic bacteria have been detected among all the clones.