Current status and future prospects of simultaneous nitrification and denitrification in wastewater treatment: A bibliometric review

A total of 516 documents were identified by using the suitable search strings in Scopus database and it showed that the annual publications related to simultaneous nitrification and denitrification (SND) in wastewater treatment increased steadily between the years 1985 and 2021. Through countries co-authorship analysis, it can be observed that China and Ministry of Education China were the most productive country and institution, respectively. The keywords analysis also revealed that there are still limited studies of SND in treating various types of wastewaters, including piggery wastewater and others. In addition, literature review regarding the functional microorganisms presents in the SND system and the factors influencing the SND performances were provided in this study. Extensive studies should be conducted in future to investigate suitable technologies and optimum operational conditions for different types of wastewaters to promote the development of SND in wastewater treatment.