Constructed wetlands as nature based solutions in removing organic pollutants from wastewater under irregular flow conditions in a tropical climate

Constructed wetlands are considered as a promising wastewater treatment option. Though extensively studied, most field experiments reflect the performance of these systems in temperate and cold climates and in relatively controlled flow conditions. This study aims at evaluating the performance of a horizontal subsurface flow constructed wetland using indigenous macrophytes in a tropical climate (i.e., in East Africa, Ethiopia) under suboptimal conditions of flow. Two selected plant species, i.e., Cyperus papyrus (papyrus) and Scirpus validus (bulrush) were tested using the wastewater from a dormitory at Jimma University Campus in Ethiopia. The experimental period consisted of two (rather) well controlled phases with two non-controlled and non-sampled phases and one intentional disturbance phase in between. BOD5 removal was 81% in papyrus, 76% in bulrush and 48% in Control. TSS removal was 76% and 75% in papyrus and bulrush compared to 54% in the control. COD removal showed 65% and 62% in the planted beds and 32% in the control. TSS removal demands more controlled operations than other parameters. It was concluded that CWs can function well under irregular flow conditions and can be the technology of choice in low income countries particularly in tropical climates. (C) 2019 European Regional Centre for Ecohydrology of the Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved.