Nitrogen removal from wastewater with a unique combination of N-damo and anammox processes

The aim of this project is the development of an integrated oxygen limited treatment system using a unique combination of the nitrite/nitrate-dependent anaerobic oxidation of methane (N-damo) and ammonium (anammox) processes. Through the integrated system it will be possible to remove ammonium, nitrite, nitrate, and methane simultaneously without the need for extra aeration and the addition of electron donors that are necessary for nitrogen removal in conventional wastewater treatment plants. Such a system would offer many advantages over current practice, including lower costs, lower production of biomass, lower energy consumption and greenhouse gas (e.g. CO2, CH4, N2O) emissions and a much smaller resource foot-print. Oxygen limited nitrogen removal systems have already been applied successfully worldwide for industrial wastewaters with high nitrogen load. The newly discovered combination of N-damo and anammox processes has not yet been used for application, but would offer the possibility to develop sustainable wastewater treatment systems especially at ambient (i.e. below 20 degree) temperatures. Microorganisms that couple the anaerobic oxidation of methane to the reduction of nitrite were recently discovered and named Methylomirabilis oxyfera. In addition, it was shown that N-damo bacteria formed stable cocultures with anammox bacteria and archaea. These cocultures removed methane, ammonium, nitrate and nitrite simultaneously better than each culture individually. By applying a combination of these microorganisms, the residual dissolved methane could be used to drive nitrogen removal instead of using costly external electron donors such as methanol. The present proposal will investigate the feasibility of the combined anammox/N-damo process as a new compact, low-cost, low-emission wastewater treatment system. The approach will consist of testing the proposed combined treatment system at laboratory. The effect of oxygen limited conditions and chemical oxygen demand (COD) surplus on the community composition, conversion rate of the biomass, and expression of genes will be determined. Design rules and a procedure for start-up will be formulated. The performance of the new combined nitrogen and methane removal system will be compared to other oxygen-limited systems with respect to investment and operation costs, energy consumption, sludge production, methane and nitrous oxide emissions, effluent quality and process stability. The research will be done in close cooperation between the Department of Microbiology of Radboud University Nijmegen, Paques BV and STOWA (Foundation for Applied Water Research).