Performance assessment of two horizontal-flow constructed wetlands for greywater treatment in Lebanon

ABSTRACT In response to the increasing pressures on the existing water resources in Lebanon, several constructed wetlands have been implemented across the country, showing promising results in water treatment. This experiment focuses on two newly completed constructed wetlands in the Bekaa Valley, assessing their efficiency in treating greywater and evaluating the potential of effluent reuse in irrigation or other non-potable applications. Influent and effluent samples were analyzed, and results showed removal of about 87–92% of total suspended solids (TSS), 65–68% of chemical oxygen demand (COD), 47–53% of biochemical oxygen demand (BOD), and a 59–76% of phosphorus. The results of this experiment were later compared against local and regional standards and case studies, which revealed comparable results for TSS and total phosphorus (TP) removal to other Lebanese, regional, and Mediterranean studies, as well as lower BOD and COD removal, highlighting the importance of further optimization. Future research should explore extended monitoring periods, plant maturity, and design adjustments to target the most stringent reuse standards. This study emphasizes the role of decentralized nature-based solutions (NBSs) for water treatment in regions with declining public water services.