Constructed wetlands (CWs) system is currently regarded as established eco-technologies to treat various types of wastewater in developed nations over the past decades due to virtue of its simplicity, cost effectiveness, based on natural processes, eco-friendly and green development. With the goal of promoting green and sustainable systems to support human well-being as well as favourable with sustaining environmental management systems, the application of CWs has become more relevant. The application of CWs is very significant especially in tropical and sub-tropical regions in developing countries, which produced satisfactory treatment efficiencies than to those in temperate regions, due to availing facility of very conducive to higher biological activity and productivity. The present paper therefore highlights the concept of CWs with removal mechanism, recent practice, applications, and research of treatment wetlands especially for tropical regions in developing countries. In the present review, the performance of contaminant removal shown to be very competent and consistent across all types of CWs. The hybrid systems appeared more efficient in the removal of TSS (92%), COD (81%), NH4-N (76%), NO3-N (78%) and TN (73%), as compared to other types of CWs. VSSF CWs removed pollutants more efficiently than HSSF CWs in terms of TSS (87%>71%), BOD (90%>81%), NO3-N (62%>44%) and TN (57%>48%), but HSSF CWs showed better removal for COD (76%>62%), TP (65%>61%) and NH4-N (66%>58%) as compared to VSSF CWs. Compared to other types of CWs, both HSSF and VSSF CWs showed superior TP removal. VSSF systems showed the best BOD removal (90%) among all the CWs types.
Constructed Wetlands, Wastewater Treatment, Developing Countries, Tropical Region, Removal Mechanism
