Recovering Ammonium Bicarbonate to Achieve Wastewater Treatment and Reuse in a Microbial Electrolysis Cell-Forward Osmosis-Coupled System

Wastewater is treated for contaminant removals and bioenergy recovery; however, the valuable resources in wastewater, such as nutrients and water, have not been well recovered for reuse. Extracting water from wastewater can be accomplished by using membrane processes, but the energy in organic compounds in the remaining concentrates was not recovered. Nitrogen recovery from wastewater requires energy-intensive processes such as struvite formation. Herein, a new concept of a microbial electrolysis cell (MEC)-forward osmosis (FO)-coupled system was proposed for wastewater treatment and recovery of both clean water and nitrogen with low energy consumption. In an MEC, the organic compounds were degraded while the generated electricity facilitated the recovery of ammonium nitrogen that was collected to prepare ammonium bicarbonate. In the FO, the generated ammonium bicarbonate was used as draw solutes to extract clean water from the MEC anode effluent. The feed concentrates from FO could return to MEC anode for further recovery. The performance of the above concept was investigated with both synthetic solution and leachate. The recovered ammonium from the MEC could reach a concentration of 0.86 mol L-1, and with this draw solution, 50.1 ± 1.7 % of the MEC anode effluent could be extracted in the FO. The results have successfully demonstrated the feasibility of coupling an ammonia-recovering MEC with FO for treating high-strength wastewater and recovering valuable resources with low energy consumption.