Recirculating Anaerobic Dynamic Membrane Bioreactor Treatment of Municipal Wastewater

A recirculating anaerobic dynamic membrane bioreactor system was evaluated at the lab scale for the treatment of simulated and real municipal wastewater (MWW). The bioreactor contained a filtration structure with meshes to support the development of a biofilm or dynamic membrane through which bulk liquid was continuously recirculated. This approach aimed to overcome high fouling and dissolved methane oversaturation, challenges typical of mainstream anaerobic membrane bioreactor technologies. At hydraulic retention times ranging from 4 to10 h, the system achieved average effluent suspended solids levels of 20 mg/L (simulated MWW) and 22 mg/L (real MWW), while also achieving average chemical oxygen demand (COD) concentrations of 71 mg/L (simulated MWW) and 84 mg/L (real MWW). The system demonstrated minimal dissolved methane oversaturation, and the average total methane yield was 0.29 L CH4/g COD removed for simulated MWW and 0.18 L CH4/g COD removed for real MWW. The observed filtration resistance rate (approximately 1 × 108 m–1 h–1) was one to two orders of magnitude lower than those reported for MWW treatment by anaerobic membrane bioreactor approaches. Operation at low transmembrane pressure and high flux was possible without intervention to control fouling for over 450 days. If the lab-scale results reported here can be achieved at the full-scale level, the recirculating anaerobic dynamic membrane bioreactor will allow for net positive energy generation over a range of MWW characteristics (0.180 to 0.658 kWh/m3). Therefore, we conclude that the recirculating anaerobic dynamic membrane bioreactor strategy deserves further study as an emerging option for low-footprint, energy-positive treatment of dilute wastewaters like MWW.