Reducing effluent discharge and recovering bioenergy in an osmotic microbial fuel cell treating domestic wastewater

Osmotic microbial fuel cells (OsMFCs) are an emerging concept that integrates forward osmosis into an MFC for simultaneous wastewater treatment, bioenergy recovery, and water extraction. Previous studies of OsMFCs have demonstrated the proof of concept and examined different draw solutes as catholytes. This study investigated the performance of an OsMFC treating actual domestic wastewater. The OsMFC achieved water flux of 1.06–1.49 LMH and reduced wastewater effluent by 24.3–72.2% depending on hydraulic retention time. Increasing the recirculation rate of the catholyte from 100 to 3000 mL/min slightly improved water flux to 2.15 LMH. The low water flux was likely due to inefficient reactor configuration, membrane fouling, and concentration polarization. The OsMFC constantly produced bioelectricity and achieved a maximum power density of 28.2 W/m3 from an acetate solution, or 4.5 W/m3 from domestic wastewater. Preliminary energy analysis suggested the OsMFC has the potential to produce more energy than was consumed by the pumping system, thereby creating an energy-neutral wastewater treatment system. After operating the OsMFC for more than 100 days, the FO membrane was analyzed for fouling using electrochemical techniques, imaging, and water flux tests, and the results revealed microbial fouling and abiotic scaling on the surface and inside the FO membrane.

► An osmotic microbial fuel cell is developed to treat domestic wastewater.
► Wastewater effluent can be greatly reduced due to osmotic water extraction.
► Bioenergy recovered from wastewater can potentially support pumping system.
► Low water flux is likely due to low shear effect and membrane fouling.