Progresses and challenges in sulfur autotrophic denitrification-enhanced Anammox for low carbon and efficient nitrogen removal

Autotrophic nitrogen removal couple process based on anaerobic ammonium oxidation (Anammox) has been applied to treat various high-ammonia and low-carbon wastewater for its advantageous ability to remove nitrogen. However, high concentrations of NO3−-N in the effluent is a drawback that prevents the total nitrogen from meeting the discharge standard. For this reason, coupling sulfur autotrophic denitrification (SADN) with Anammox for the advanced treatment of NO3−-N to achieve a completely autotrophic biological nitrogen removal process that is independent of organic matter has become a major focus of research in recent years. To reduce SO42−-S in the SADN process, the short-cut SADN (SSADN) process was pioneered for controlling NO3−-N reduction in the NO2−-N phase. This method also serves as an efficient anaerobic autotrophic process that simultaneously removes biological nitrogen from wastewater containing NH4+-N and NO3−-N. This article reviews the control parameters of SSADN and the forms of coupling with Anammox, analyze the directional transformation of nitrogen and sulfur in the coupling process and the complex competition of substrates, and finally evaluate application bottlenecks that limit its industrialization, which are necessary to address for furthering the development of this process.