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 10L 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 18L/m2h (LMH) could be obtained under the tested conditions. Under continuous operation (100d), the flux gradually settled to a stable range of 10–15LMH when weekly manual fouling control was applied. When frequent backwash (for 5min every 4h) was applied, an average flux of 50LMH 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 (4.5L/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 100d), 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. [Display omitted] ► A lab-scale gas-lift anaerobic membrane bioreactor (Gl-AnMBR), using a tubular PVDF membrane, was developed and studied over a 100d period to treat synthetic sewage. ► The permeate flux was 10–15LMH when the membrane was maintained weekly through manual backwash and cleaning. ► The permeate flux averaged 50LMH when the membrane was operated on an automated, scheduled backwash routine (5min duration at 4h interval). ► Gl-AnMBR removed 98% and 95% of COD and TOC, respectively. ► Most of the nitrogen (95.5%) and phosphorus (93.4%) added to the reactor were solubilized and recovered in the permeate after 100d.