Nutrients (TN and TP) causing eutrophication, have continuously been managed in Korea. In the case of TP, the most severe regulation was strengthened to 0.2mg/L, whereas in the case of TN, regulation was still insufficient at 20mg/L. In the United States, TN management is regulated by season, item, and period. In Germany, the size of the sewage treatment plant and in Japan, the standard of effluent water quality differs according to the sewage treatment plant construction method (Im and Gil., 2018). Considering the current state of international TN regulation, domestic TN regulation is expected to be strengthened soon, like TP.
In order to treat such nitrogen, most treatment plants in Korea currently use the “nitrification-denitrification” process or a modified method based on it. However, the “nitrification-denitrification” method is a very traditional technology and over the past decades there has been dramatically changed “nitrogen technology”. “Nitrification-denitrification” is classified as “Nitrogen 1.0” in the US WERF (Water Environment Research Foundation). The one step advanced technology in this technology is a “nitritation-denitritaion” and is expressed as “Nitrogen 2.0.” A representative method is the SHARON (Single reactor for High activity Ammonium Removal Over Nitrite) technology, and there is no method applied in a full-scale treatment plant in Korea. Although the “Nitrogen 2.0” technology is economical enough, the ANAMMOX technology called “Nitrogen 3.0” appeared and ANAMMOX technology quickly emerged as the attractive technology abroad. More than 140 ANAMMOX full plants have already been installed worldwide for the treatment of recycle water (Joss A et al., 2009; Winckel et al., 2019; Roots P et al., 2019; Chen K et al., 2020; Yang S et al., 2021; González-Martínez A et al., 2021; Wan X and Volcke E. 2022).
More recently, ANAMMOX research is being conducted towards mainstream applications. In Belgium, there is a case of modeling the application of mainstream ANAMMOX for energy independence in sewage treatment plants (MingshengJi et al., 2020), in Spain, the effect of COD on mainstream ANAMMOX was studied (MaitePijuan et al., 2020), and in Switzerland, 20 ANAMMOX reactivity was evaluated for DO shock at degrees and below 14 degrees. (Robert Niederdorfer et al., 2021) In China, in Mainstream, NO3 is made through general nitrification and NO2 and NH4 are met in the process of denitrifying the NO3. The ANAMMOX process was studied (Rui Du et al., 2020). In the case of Mainstream ANAMMOX, no real-scale research results have been released yet, but the pilot-scale research results were a case of installation at Dohaven WWTP at Delft University of Technology in the Netherlands in 2019 (Maaike Hoekstra et al., 2019) and a case of research on a scale of 8 tons in 2021 at Zurich Institute of Technology in Switzerland (Damian Hausherr et al., 2021).
Most studies in the field of mainstream ANAMMOX have only focused on nitritation for low ammonium nitrogen. However, in this study, A3O (Anaerobic-ANMMOX-Anoxic-Oxic) process was developed, treating nitrite (nitritated from recycle water), and ammonium nitrogen (from incoming general sewage in mainstream). In other words, instead of insisting on using low-concentration nitrogen which is unfavorable for nitritation, a method of using high-concentration nitrogen advantageous for nitrite oxidation was derived (Im and Gil., 2019, Im et al., 2014). It has been operated stably for a long period of more than about 1,500 days, and the results of this study are expected to be used as basic data for the full plant application of Mainstream ANAMMOX.