Overview of Theme 2
We developed a set of systems connecting “conversion to NH4+” and “separation and concentration of NH4+” to recycle organic nitrogen compounds, a major nitrogen component, in wastewater as an ammonia resource. To date, nitrogen compounds in wastewater have been biologically detoxified; however, the untreated portion is directly discharged into rivers. In this theme, we completely cease nitrogen discharge into natural environments using nitrogen removal processes and further achieve effective resource and energy recovery from concentrated ammonia water.
For technologies of microbial conversion from nitrogen compounds to ammonia, we developed a micro-aerobic conversion process and an anaerobic bioreactor (AnMBR) capable of efficient treatment under high ammonium concentrations. For concentration technologies, we established a membrane separation method based on a novel principle, such as osmotic pressure driving, and an adsorptive separation method capable of efficient adsorption and easy desorption. By combining these technologies, we developed an ammonia recovery process system. We demonstrated the possibility of effectively reducing nitrogen loads in natural environments using bioconversion technologies to prevent the excessive oxidation of nitrogen and concentration technologies that maximize the NH4+ recovery ratio.