Enhanced ammonia recovery from wastewater by a transmembrane electro-chemisorption system directly connecting anode chamber and cathode chamber with gas permeable membrane

Abstract

A transmembrane electro-chemisorption (TMECS) system was developed via directly connecting anode chamber (AnC) and cathode chamber (CaC) with a hydrophobic gas permeable membrane (GPM). The special structure of the TMECS system with AnC and CaC at two sides of GPM contributed to both forming localized extreme pH layers at two sides of GPM and using electrical field forces to enrich NH4+, thus realizing on-site utilization of authigenic acid and base to enhance the ammonia recovery from wastewater. Increasing applied voltage (from 2.0 to 6.0 V) and salt concentration (from 80 to 500 mM) could improve the system performance by promoting water splitting and reducing internal resistance, respectively. The system showed wide applicability for the influent ammonia concentration (from 560 to 5000 mg NH4+-N/L) with the ammonia removal and recovery efficiencies of 61.9 %–77.1 % and 78.5 %–91.9 % at 24 h, respectively. For high influent ammonia concentration (5000 mg NH4+-N/L), a specific energy consumption of 21.8 kWh/kg N could be reached. Moreover, the system can be easily scaled up by stacking the TMECS units. Therefore, the system shows good prospects in saving chemicals, wide applicability and easy scale-up for ammonia recovery from wastewater.