Decentralized constructed wetlands for domestic wastewater treatment in developing countries: Field-scale case studies, overall performance and removal mechanisms

In most of the developing world, domestic wastewater is discharged into the aquatic environment prior to applying any treatment technologies, causing various public health concerns. In this regard, constructed wetlands (CWs) are an alternative decentralized sanitation systems, to be applied as economically viable and most suitable for the climate conditions of developing nations. This paper describes a comprehensive review on the potential application of CWs for sustainable treatment of decentralized domestic wastewater in developing countries (2014–2023). In this paper, 17 single-stage CWs, 8 hybrid and 9 CWs integrated with other techniques that were operated in pilot and full-scale case studies were reviewed. Besides, the pollutants removal mechanisms, challenges and factors affecting the performance of CWs treatment are also illustrated. However, further study is required (i) in optimizing, the scale-up, long-term performance of CWs, (ii) the application of an innovative filtration media and (iii) searching for the new and suitable wetland plants that accomplishes higher efficiency for domestic wastewater treatment.