Evaluating the role of hydraulic retention time (HRT) in pollutant removal efficiency using <i>Arundo donax</i> in vertical subsurface flow constructed wetlands
Ali Meawad Ahmed, Sabreen L. Kareem
Abstract
This research explores the effectiveness of phytoremediation as a sustainable method for sewage treatment, focusing on the performance of Arundo donax in a subsurface vertical flow constructed wetland at the Al-Muamirah treatment station in Hilla, Iraq. The study presents an alternative to conventional sewage treatment systems, particularly suited for resource-constrained regions. Key pollutants such as biochemical oxygen demand (BOD), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), and total suspended solids (TSS) were analyzed to assess removal efficiencies. Data were collected over a period from October 2023 to March 2024 using a batch-mode system with an influent flow rate of 0.05276 m³/day (± 0.016 m³/day). Optimal hydraulic retention times (HRT) were identified at 5 days for BOD, COD, and TSS, while TN and TP required extended retention of 8 days due to their reliance on slower microbial and adsorption processes for effective removal. A control unit, lacking plant integration, was used for comparative analysis. The results demonstrated that Arundo donax achieved removal efficiencies of 91% for BOD, 84.28% for COD, 68.37% for TN, 73.42% for TP, and 89.23% for TSS, significantly outperforming the control setup. These findings emphasize the critical role of optimized HRT in enhancing pollutant removal, particularly for nutrients like TN and TP, and underscore the potential of Arundo donax as an eco-friendly solution for wastewater management.