Chapter 7 - Recent advances in biological nitrogen removal from wastewater: Special focus on reactor configuration and nano-mediated microbial nitro-transformation

Abstract

Rapid industrialization, increasing anthropogenic activities, and unmanaged agricultural and industrial discharge over the years have caused overaccumulation of nutrients (e.g., nitrogen) in water bodies. The overaccumulation of nitrogen in aquatic system resulting in eutrophication and depletion of oxygen levels, thereby ultimately damaging the fabric of the aquatic ecosystem of water bodies. Biological nitrogen removal (BNR) exploiting microbial nitrification and denitrification process is more effective and cost efficient than their physicochemical counterparts. In the nitrification process, ammonium nitrogen gets oxidized to nitrite and then nitrate by the sequential action of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), respectively. Although multiple BNR processes such as Anammox, partial nitrification and denitrification, and Cannon (completely autotrophic nitrogen removal over nitrite) have been developed over the years, overall removal of nitrogen is not very enticing. Hence, novel strategies to improve the BNR efficacy through reactor reconfiguration, precise control of environmental and physicochemical factors, and nanoparticle (e.g., graphite and silver nanoparticles) mediated process intensification are warranted. This communication gives insight and special emphasis on reactor configuration and nanoparticle-mediated nitrogen transformation for the improvement of BNR processes.