Evaluating Pilot-Scale Floating Wetland for Municipal Wastewater Treatment Using Canna indica and Phragmites australis as Plant Species

Abstract

Floating treatment wetlands (FTWs), also called constructed floating wetlands or floating islands, are a recent innovation in constructed wetlands (CWs) inspired by natural wetlands. In FTWs, emergent plants grown hydroponically on buoyant mats are used for wastewater treatment, which makes them far more economical than other CWs. The objective of this study was to evaluate the performance of FTWs for the treatment of municipal wastewater from an urban drain using native plant species Canna indica and Phragmites australis. A pilot-scale experiment was carried out using four FTW treatment cells with different plant coverages for pollutant removal: C1 (Canna indica, 100% coverage), C2 (Phragmites australis, 100% coverage), C3 (Phragmites australis, 50% coverage), and C4 (control). Overall, treatment cells with Canna indica and Phragmites australis showed reductions in BOD5, COD, EC, TDS, NO3−, and PO43− compared with the control. Maximum BOD5 and COD removal was 53% and 50%, respectively, at 50% coverage of Phragmites australis (C3). The maximum reduction in NO3− (61%) was achieved using Canna indica at 100% coverage (C1). Conversely, moderate removal of PO43− (27%) was obtained in the control (C4) with a visibly high amount of algal growth, indicating the influence of algae on pollutant removal. This study highlights the significance of Phragmites australis for organic matter removal and Canna indica for nutrient removal, mainly NO3− from municipal wastewater. Furthermore, this study suggests that FTWs perform well for BOD5 and COD removal at 50% plant coverage (Phragmites australis) and NO3− removal at 100% coverage (Canna indica).