PDMS membranes for feasible recovery of dissolved methane from AnMBR effluents

This study aimed to evaluate the feasibility of degassing membrane (DM) technology for recovering dissolved methane from AnMBR effluents. For that purpose, a PDMS membrane module was operated for treating the effluent from an AnMBR prototype-plant, which treated urban wastewater (UWW) at ambient temperature. Different transmembrane pressures and liquid flow rates were applied for evaluating methane recovery efficiency. Maximum methane recoveries were achieved when increasing the vacuum pressure and reducing the liquid flow rate, reaching a maximum methane recovery efficiency of around 80% at a transmembrane pressure (TMP) of 0.8 bars and a treatment flow rate (QL) of 50 L h−1. The results revealed that the combination of PDMS DMs and AnMBR technology would allow to reduce the energy demand of UWW treatment, achieving net energy productions while reducing greenhouse gas emissions. Optimum operation was determined at a TMP of 0.8 bars and a QL of 150 L h−1 when combining energy, environmental and economic targets. Under these operating conditions, the combination AnMBR + DM resulted in energy requirements and greenhouse gases emissions of −0.040 kWh and 0.113 kg of CO2-eq per m3 of treated water, respectively, resulting in a DM payback period of around 10.5 years.