The advance of heterotrophic nitrification aerobic denitrification microorganisms in wastewater treatment

Heterotrophic nitrification and aerobic denitrification (HNAD) microorganisms can accomplish simultaneous nitrification and denitrification in a single reactor, which significantly reduces area occupation and cost of construction compared to traditional autotrophic nitrification and anaerobic denitrification microorganisms. HNAD microorganisms were isolated from various habitats. Nitrogen removal of HNAD microorganisms was mainly through assimilation and dissimilation. The impacts of the initial ammonium concentration, carbon supply, C/N ratio, temperature, pH, dissolved oxygen (DO), and salinity have all been reviewed. It was surprising to find that HNAD microorganisms could both remove nitrogen and phosphorus. And the metabolic mechanism of phosphorus removal by HNAD microorganisms was also displayed. This review comprehensively introduces the metabolic mechanism of nitrogen and phosphorus of HNAD microorganisms as well as the effects of various external environments on nitrogen removal performance to guide the application of HNAD microorganisms in practical wastewater treatment. But the large-scale application of HNAD microorganisms is limited.