Investigation of an electrodeionization system for the removal of low concentrations of ammonium ions

Current interest exists for the development of an electrodialysis system for the removal of low levels (<200 ppm) of ammonium ions commonly found in recycled effluent streams in such diverse applications as expected in a space station and commercial fisheries. Ammonium ions are generated as a decomposition product of urea and over a time build up in concentration, thus rendering the water unsuitable for human consumption and supporting wildlife. Electrodeionization (EDI) was evaluated for this process because of the low concentrations of ammonium ions. The process was evaluated in a two-stage EDI system using a simulated aqueous waste stream. Using a two-stage unit, ammonium ion could be reduced from 200 ppm to less than 1 ppm. Volume was based on 225 Ib of water for a four-person team to be recycled over a 24 h period. Electrical consumption for the EDI treatment was found to be 5.04 Wh/lb based on processing 225 lb water/day.