Anaerobic biological treatment systems can offer a number of advantages over their aerobic counterparts. The operational costs associated with anaerobic systems are typically lower than with aerobic systems, and anaerobic systems also generate less waste sludge. In addition, the energy associated with the biogas produced during anaerobic biological treatment can potentially be recovered. However, to date, the use of conventional anaerobic biological systems for the treatment of dilute wastewaters has been relatively limited. The present study was designed to address this current knowledge gap. The specific objectives of the present study were (1) to assess and compare the treatment performance of external and a submerged membrane AnMBRs operated at different OLRs when treating a low strength municipal wastewater at a relatively low temperature, (2) to assess and compare the membrane filtration characteristics of mixed liquors generated in external and submerged membrane AnMBRs, (3) to assess and compare the membrane filtration characteristics of a mixed liquor in AnMBRs when filtering through inorganic and organic membranes, and (4) to assess and compare the membrane filtration characteristics of the mixed liquors generated in AnMBRs to the mixed liquor generated in an aerobic MBR operated with the same influent wastewater.