Beyond Targets: Benefits of a Multi-Assessment Approach in Determining Chemical Water Quality for Water Reuse

The multitude of organic micropollutants (OMPs) in treated wastewater (TWW) represents a significant challenge for water reuse. This study aimed to evaluate water quality using a combination of target analysis, effect-based methods (EBMs), and nontarget screening (NTS) to demonstrate the benefits of a comprehensive chemical risk assessment of TWW and to assess its reuse potential. OMPs were analysed in a pilot plant treating municipal wastewater, using a combination of ozonation, advanced oxidation with hydrogen peroxide, ceramic membrane filtration, and granular activated carbon. Target analysis showed that the treatment effectively removed OMPs, but negative removal was observed after activated carbon, likely due to desorption. After activated carbon, benzotriazole, caffeine, carbamazepine, diuron, fipronil, imidacloprid, linuron, MCPA, O-desmethylvenlafaxine, sulfamethoxazole, and venlafaxine had risk quotients >0.1, with fipronil consistently exceeding 1 and MCPA exceeding its drinking water guideline value. In vitro EBMs, covering oxidative stress, xenobiotic metabolism, cytotoxicity, estrogenicity, and thyroid disruption, detected effects in secondary TWW. EBMs revealed the ceramic membrane treatment’s ability to remove oxidative stress. Based on effect-based trigger values for surface and drinking water, risks for estrogenicity were only absent after the full treatment train. NTS showed that 26–37% of features were removed, driven by oxidative treatments, while membrane filtration and activated carbon effectively removed features introduced by the oxidative treatment. Hence, this study suggests that TWW reuse without advanced treatment is not recommended. The multiassessment approach applied here allowed more nuanced conclusions on water safety, underscoring its added benefit for water quality assessment for water reuse.