Study of Submerged Anaerobic Membrane Bioreactor (AnMBR) Treating Municipal Wastewater

Conventional anaerobic biological treatment systems can effectively remove the bulk of the organic contaminants present in wastewater; however, they are typically not effective at removing residual levels of soluble and colloidal organic contaminants. By coupling a membrane to an anaerobic biological reactor, it may be possible to maintain an adequate biomass concentration to effectively treat low/medium strength municipal wastewater. The objective of the study was to critically analyze the treatment performance of a submerged anaerobic membrane bioreactor (AnMBR) treating low strength municipal wastewater at an ambient temperature. The anaerobic process was effective in removing chemical oxygen demand (COD) and volatile fatty acid (VFA) from the effluent. VFA removal was essentially complete and 80% COD removal was achieved under acetate-supplemented conditions. Nonetheless, high concentration of effluent COD (i.e. 72 mg/L) indicated that aerobic post treatment is needed to achieve secondary quality effluent. Measured biogas production rates were always lower, and in some cases substantially lower, than the expected values. The permeate flux and TMP profiles illustrated that the permeate flux that could be maintained in the submerged AnMBR system was 5 L/m2 hr. Similar aerobic MBRs can typically sustain a flux of 20-30 L/m2 hr. Therefore, membrane flux became the limiting process attribute for the AnMBR