Review on applicability of constructed wetlands in the South Asian region focusing on roles of media, macrophytes, microbes, pre-treatment and post-treatment.

This article examines the utilization and advancements of constructed wetlands (CWs) in South Asia (SA), focusing on their roles, costs, and efficacy enhancements through pre- and post-treatment units for various pollutants. Notable findings include Phragmites and Canna species as commonly used macrophytes, achieving high removal rates for various pollutants. CWs consistently remove total suspended solids, biochemical oxygen demand, chemical oxygen demand, emerging contaminants, and antimicrobial resistant bacteria at substantial rates. Anaerobic baffled reactors are effective pretreatment devices for high-strength wastewater. Moreover, CWs exhibit lower operational and maintenance costs compared to conventional treatment methods. However, the bibliometric analysis reveals limited regional cooperation in SA. Key challenges identified include the absence of guidelines for media, vegetation, and maintenance. The review underscores the necessity for further research in optimizing CWs' efficiency through land area management, plant selection, and enhanced design and operation and maintenance protocols. [ABSTRACT FROM AUTHOR]