Economic and Life Cycle Assessment of Electrodialysis, Denitrification, and Anammox for Nitrogen Removal in Municipal Wastewater Treatment

Abstract

Technologies to remove nitrogen from wastewater are employed to preserve drinking water and prevent environmental damage. Nitrification/denitrification and partial nitrification-anammox are two accepted wastewater nitrogen removal techniques for wastewater treatment plants. These processes require energy for aeration and can release fugitive greenhouse gases in the form of nitrous oxide. Electrodialysis could potentially be used as an alternative to remove ammonium from waste streams but previous experimentation has concluded that concentrate flows experience rapid scaling and fouling of membranes. A newly-patented electro dialysis technique, however, uses monovalent-selecting membranes to exceed previous technological limitations with the goal of extracting ammonium ions from sewage for market as ammonium-based fertilizer while limiting scale from poly valent ions. This life cycle assessment compares the three technologies and compiles literature values to attempt to compare the state of the art of municipal nitrogen removal to the new electrodialysis technique, accounting for the offset of Haber Bosch-derived ammonia. Nitrogen removal and recovery by electrodialysis is estimated to carry both lower initial capital costs and lower operation costs than traditional technologies. Electrodialysis is also projected to be environmentally favorable compared to the state of the art, projecting electricity savings similar to anammox and, with the offset of industrial ammonia manufacture, net negative emissions in several environmental categories.