Use of different plants species in vertical-flow constructed wetland for organic matter removal from domestic wastewater

Background: In developing countries where the economic situation is less sustained, constructed wetlands might be suitable in the management of wastewater before the discharge into natural environments because of their possible generation of revenues that could support maintenance costs. However, organic matter (OM) removal in constructed wetlands using different species of plants often varies, and the contribution to organic matter removal by various pathways remains unclear. Aims: To demonstrate the effects of five local forage plants (i.e Andropogon gayanus, Chrysopogon zizanioides, Echinochloa pyramidalis, Pennisetum purpureum and Tripsacum laxum), and to determine the contributions of different pathways onto organic matter (OM) removal from synthetic domestic wastewater in vertical flow constructed wetlands (CWs). Methods: A pilot-scale composed of six beds constructed with bricks, and filled from bottom to top with 0.1 m gravel covered with cloth and 0.6 m white lagoon sand was used. Five beds were transplanted by local forage seedlings, while one was used as the control. 80 L of domestic synthetic wastewater was then applied on the beds intermittently over six months. Results: All of the five plants species grew well, improving thus organic matter removal, but those of P. purpureum provided a greater and fresher with 15.86 kg.m-2 and achieved the best Total Suspended Solids (TSS), 5-day Biochemical Oxygen Demand (BOD5), and Chemical Oxygen Demand (COD) with removal efficiencies around 93.81 %, 98.51 %, and 95.92 %, respectively. Likewise, OM amount decreased in the beds’ sediments from upper surface to the bottom. According to the mass balance approach, OM removal by sediment storage and microbial uptake were 12.26–49.97 % and 43.87–85.10 %, respectively. Regarding OM removal pathways, a slight difference between species of plants of CWs was observed, but microbial uptake remained mainly OM removal pathways. Nevertheless, sediment storage is a main OM removal pathway for some plants (e.g. C. zizanioides). Conclusion: Constructed wetlands transplanted with P. purpureum could be a cost-effective alternative method of wastewater treatment.