Constructed wetlands as a sustainable solution for domestic wastewater treatment in Egypt

Abstract

Water scarcity and limited access to effective wastewater treatment represent critical challenges in arid and semi-arid regions, where water reuse is increasingly necessary to support agriculture and local communities. To address these challenges, a Nature-Based Solution (NbS) was implemented in El-Banger village near Alexandria of Egypt, where a sand biofilter system for civil wastewater treatment was previously unable to meet reuse standards. This study presents the design and evaluation of a new bench-scale Constructed Wetland (CW) that operated with a hydraulic retention time of approximately 20 h over a two-week experimental period, and integrated locally available macrophytes (Phragmites australis, etc.) with a multilayer filtering substrate. The bench-scale CW efficiently remediated the influent wastewater, achieving over 93 % Chemical Oxygen Demand (COD) removal, contributing to meet Egyptian standards for agricultural and gardening reuse, when considered together with the overall physicochemical and microbiological assessment. Moreover, pathogen counts, including Escherichia coli and Staphylococcus aureus, were reduced by more than three orders of magnitude, and solar-powered UV disinfection eliminated residual contamination. Toxicity and phytotoxicity tests using Daphnia magna and Solanum lycopersicum seeds confirmed the absence of adverse effects. Metagenomic analyses revealed functional bacterial taxa (e.g., Actinobacteria, Proteobacteria, Bacteroidetes) contributing to pollutant degradation, along with reduced fungal diversity post-treatment. These results confirm that our bench-scale CW, based on local materials and macrophyte consortia, can replace conventional wastewater treatments in the context of limited resources. However, future research should focus on system upscaling, long-term performance assessment under real operating conditions and the optimization of the CW plant efficiency for an optimal wastewater reuse in arid and Mediterranean regions.