Discovering research evolution and emerging trends in ammonium wastewater treatment technologies: a bibliometric analysis

Various integrated treatment methods have been extensively studied by researchers worldwide to effectively remove ammonium from different types of wastewater. In this study, a bibliometric analysis was conducted using VOSviewer software to provide an overview of the research trends in ammonium wastewater treatment technologies, based on data extracted from the Scopus database. The objective of this study is to analyse the growing interest in current ammonium removal technologies in terms of annual publications, leading journals, prominent authors, countries and institutions, author keywords, treatment methods, reactors, wastewater types, and novel approaches. A total of 1,451 publications were recorded between 1972 and 2020, indicating a continued increase in future publications. China emerged as the leading country, with the highest number of publications on this topic. Among 3,100 retrieved keywords, the most active keyword was "wastewater treatment" with 183 occurrences and has a strong link with keywords such as "nitrification". The keywords "anammox", "ion exchange", and "electrochemical oxidations" had the highest occurrences among biological, physical and chemical treatment methods. Besides, the keywords "sequencing batch reactor" and "domestic sewage" were found to be the most frequently used in studies on bioreactors and wastewater related to ammonium treatment. Several novel treatment methods, including "comammox", "feammox", and "advanced oxidation" were recorded as having the most recent publication years. This study provides information on ammonium removal technologies and helps future scholars to develop new ideas in the field of wastewater treatment.