Advances in microbially mediated manganese redox cycling coupled with nitrogen removal in wastewater treatment: A critical review and bibliometric analysis

Nitrogen (N) pollution has emerged as one of the major threat to global sustainable development and has received increasing attention. Manganese (Mn) is the third most abundant transition metal on earth and microbially mediated Mn redox cycling coupled with N removal (MMnRCCNR) is a promising alternative that is not only economical and efficient but also has a low environmental impact. This review discusses the key influencing factors, theoretical basis, and mechanisms of Mn species as key mediators driving the biogeochemical cycle. In addition, the application and development trend of Mn redox cycling in the treatment of polluted water are summarized and presented, especially the combination of simultaneous N and micropollutant removal. The research hotspots and trends of Mn redox cycling mediated biological N removal are analyzed by bibliometric methods and the current research gaps, challenges, and future directions are identified. Overall, this review is expected to provide guide for further development and optimization of Mn redox-mediated microbial N removal processes, which will help to develop cost-effective N removal processes in the future to treat contaminated water.