Full-Plant Deammonification for Low-Energy, Low-Carbon Nitrogen Removal

The successful application of full-plant deammonification could save wastewater utilities hundreds of millions of dollars in aeration and external carbon costs in the life cycle. Even the most efficient wastewater treatment designs with energy recovery systems usually do not yet achieve energy-neutral conditions. This paper describes an energy-neutral or even energy-positive wastewater treatment with reduction of external carbon for denitrification by applying the more efficient alternative biological pathway of the ANaerobic AMMonium-Oxidizing “anammox” bacteria in the main wastewater treatment process. “Deammonification” is a two-step process in which ammonia oxidizing bacteria (AOB) aerobically convert half of the ammonia to nitrite and anammox bacteria oxidize the ammonia using nitrite to produce nitrogen gas without the organic carbon substrate required for conventional heterotrophic denitrification. Deammonification is successfully used to treat ammonia-rich wastestreams such as dewatering sidestreams from anaerobically digested sludge. Full-plant, or mainstream deammonification is an innovative technology that can be compatible with existing wastewater infrastructure, often with minimal modifications. The implications of deammonification for sustainable, cost effective and energy positive wastewater treatment are extraordinary. Process flowsheets using mainstream deammonification maximize energy recovery by diverting more particulate organic carbon away from the nitrogen removal process and directing it toward anaerobic treatment where energy can be recovered through anaerobic digestion and methane capture. The combination of reduced energy and carbon demand for nitrogen removal with increased energy recovery from raw wastewater creates a significant reduction in external energy needed for wastewater treatment.Through demonstration and conceptual application at collaborating utilities, research is underway to develop an evaluation framework for implementing full-plant deammonification. The framework will be of immediate and beneficial use to the wastewater sector by advancing understanding and providing practical information to speed implementation.