Risk-Based Chemical Contaminant Framework to Comply with the EU Nonpotable Reuse Regulation

Considering climate change impacts, nonpotable water reclamation offers a drought-proof water supply to support agriculture and enhance food security. To comply with the new EU water reuse regulation, this study developed a risk-based framework for chemical management in nonpotable water reuse, addressing indicator chemicals, relevant environmental end points, and risk mitigation strategies. Over two years, different effluent qualities (tertiary effluent + UV; secondary effluent + ultrafiltration (UF) + biological activated carbon (BAC) filtration + UV) and tap water (benchmark) were applied to irrigate raw-eaten crops at a demonstration site in Schweinfurt, Germany. Of six crops, tomatoes and celeriac showed the highest detection frequencies of trace organic chemicals (TOrCs). However, even with disinfected tertiary effluent, crop consumption did not pose a human health risk. Soil analysis and mass balance calculations indicated minimal groundwater contamination risk, highlighting soil’s role as a natural barrier against TOrCs. Benzotriazole, despite its high concentration in secondary effluent (∼170,000 ng L–1), was infrequently detected in crops (max. 17 ng g–1 in celeriac), occurred moderately in soil (3–1000 ng g–1), and in percolation water (550 ng L–1). An advanced multibarrier treatment such as tertiary filtration + ozonation + BAC is recommended if an elevated chemical risk exists.