Organics and nitrogen recovery from sewage via membrane-based pre-concentration combined with ion exchange process

Abstract

This study proposes the recovery of organics and nitrogen from sewage through membrane-based pre-concentration (MPC) combined with ion exchange (IE) process. Unlike conventional activated sludge process, MPC–IE redesigned organic carbon flow to increase chemical oxygen demand (COD) conversion for energy recovery via anaerobic digestion (AD). This process also achieved nitrogen recovery instead of destruction. Membrane-based pre-concentration of COD was conducted using actual sewage for one month. As high as 65% COD was recovered. Batch IE adsorption and regeneration experiments were conducted. However, these experiments recovered only 37.5% NH4-N because of the selectivity of IE for hard ions over ammonium. Despite the low rate of recovery, the process could achieve a total of 0.38kWh/m3 energy recovery by combining energy production with anaerobic digestion of pre-concentrated organics (0.26kWh/m3) and energy saving via nitrogen reuse (0.12kWh/m3). Highly efficient energy and nitrogen recovery from sewage via MPC–IE process was expected after optimization.