Assessing constructed wetlands for water reuse in agricultural irrigation: a comparative study of treatment configurations

Water scarcity is one of the most critical challenges for sustainable development, with agriculture being the most vulnerable sector. Constructed Wetlands (CWs) offer an efficient and sustainable solution for water reuse, enabling the treatment of wastewater to produce irrigation-quality water and reducing reliance on freshwater sources. However, treatment performance of CWs can vary and may in some cases be insufficient to meet the water quality standards for safe agricultural reuse. This study addresses this gap by evaluating and comparing the treatment performance of seven CWs types and their combinations, including both single-stage and hybrid systems, aiming to identify optimal configurations and assess their suitability for agricultural irrigation in compliance with European legislation. The CWs are located at the Experimental Centre for New Water Technologies in Carrión de los Céspedes (Seville, Spain). The results showed that the performance of CWs differed significantly among configurations. Significant differences were observed for TSS, TDS, BOD₅, COD and nitrogen-related parameters, while phosphorus removal showed no significant variation among systems. Hybrid combinations of CWs showed high performance for the removal of solids, organic matter, and pathogens. The results also showed that four out of the five CWs configurations complied with the regulatory limits for TSS and BOD₅, while only one system achieved the standard for E. coli. The hybrid configuration VSSF + FWS CWs was the only system to meet all thresholds for safe agricultural irrigation, with average effluent of 6.5 mg/l for TSS, 4.5 mg/l for BOD₅ and 3.3E+02 CFU/100 ml for E. coli. Our findings show the potential of CWs, specially hybrid configuration, for wastewater treatment and safe agricultural water reuse.