Development and start up of a gas-lift anaerobic membrane bioreactor (Gl-AnMBR) for conversion of sewage to energy, water and nutrients

A lab-scale, gas-lift anaerobic membrane bioreactor (Gl-AnMBR) was developed and evaluated for its ability to treat and recover resources from sewage. Gl-AnMBR is a hybrid treatment technology that combines anaerobic biological process with low-pressure membrane filtration. A synthetic sewage, mimicking household wastewater, was used as feed to the 10 L suspended-growth bioreactor, which is coupled to a tubular PVDF ultrafiltration membrane (with biogas as sparge gas) for sludge/water separation. A series of rapid filterability assessments of flocculant anaerobic sludge was performed and a flux of 18 L/m2 h (LMH) could be obtained under the tested conditions. Under continuous operation (100 d), the flux gradually settled to a stable range of 10–15 LMH when weekly manual fouling control was applied. When frequent backwash (for 5 min every 4 h) was applied, an average flux of 50 LMH was sustained. Gl-AnMBR showed excellent removal efficiencies of sewage organic matter (up to 98% and 95% in chemical oxygen demand and organic carbon removal, respectively), while producing methane as biogas (4.5 L/d), which can be used for membrane scrubbing and energy recovery. The high-clarity permeate contained soluble nutrients derived from sewage organic matter (95.5% and 93.4% cumulative recovery for nitrogen and phosphorous, respectively, after 100 d), which may potentially be used for combined fertilization/irrigation (fertigation). The study demonstrates that Gl-AnMBR is a promising technology for wastewater reuse and resource recovery.