Novel biological nitrogen removal process for the treatment of wastewater with low carbon to nitrogen ratio: A review

Low carbon to nitrogen ratio (C/N) wastewater contains low organic carbon sources, leading to incomplete removal of nitrogen (N) and phosphorus (P) in the processes of denitrification and anaerobic P release. Due to N and P pollutants in water bodies, there is a serious threat to sustainable development, human health, and water ecosystems. Hence, it is of great significance to develop the energy-saving, efficient, and sustainable N and P removal technology. As functional microorganisms of simultaneous nitrification, denitrification, and phosphorus removal (SNDPR) process, glycogen accumulating organisms (GAOs) and phosphorus accumulation organisms (PAOs) can fully store the carbon source of raw wastewater as the intracellular carbon source while performing N and P removal. Additionally, with the novel autotrophic biological N removal technologies such as anaerobic ammonium oxidation (Anammox), ferric ammonium oxidation (Feammox), and nitrate-dependent ferrous oxidation (NDFO), the inorganic carbon sources (CO2, HCO3-, CO32-) can be used as carbon sources, thus achieving N removal. These novel biological nitrogen removal (BNR) processes effectively solve insufficient carbon sources in wastewater with low C/N. In this paper, the recent findings and potential applications of the novel technologies such as SNDPR, Anammox, Feammox, and NDFO are reviewed, and the effectiveness and development trends of the novel technologies in wastewater treatment are discussed. Besides, a new process model is developed for the deep treatment of wastewater in practical engineering. Finally, the development opportunities and challenges of the novel BNR process in future practical engineering applications are summarized and forecasted.