Quality assessment and microbial monitoring of a full-scale direct potable reuse plant in Flanders, Belgium

ABSTRACT To ensure future drinking water supply security, alternative sources like treated wastewater are gaining attention. This study presents the first full-scale direct potable reuse (DPR) scheme using municipal WWTP effluent in Europe, located in Aalst, Belgium. Commissioned in 2025, the facility produces 50 m3/h of drinking water using a multi-barrier treatment train consisting of ultrafiltration, reverse osmosis (RO), UV disinfection, activated carbon filtration, and final disinfection by UV and chlorination. Comprehensive microbial monitoring during commissioning showed that bacteria, protozoa, and viral indicators were below reporting limits after treatment. Flow cytometry and phenotypic fingerprinting confirmed RO membrane integrity, showing a reduction in microbial concentrations from (1.02 ± 0.01) × 107 to (2.69 ± 0.05) × 104 cells/mL across the treatment train. Turbidity, organic carbon, (in)organic parameters, nutrients, metals, and organic micropollutants were significantly removed, and the final water met all drinking water standards. After an extended quality assessment, the reuse water was directly connected to the drinking water network for full-scale performance evaluation. The plant operated at a 63% overall recovery, with low chemical use and a specific energy consumption of 0.63 kWh/m3 drinking water produced, rising to 0.98 kWh/m3 when including pumping to the network. The RO concentrate met the discharge norms. This study demonstrates the safety and reliability of DPR.