Ecotoxicological Assessment of Advanced Wastewater Treatments Using Aquatic Model Organisms

The Directive (EU) 2024/3019 on urban wastewater treatment (WWT) imposes new, stringent targets for nutrients and pharmaceutical compounds, thereby requiring the implementation of tertiary and quaternary treatments and promoting water reuse. This study evaluated the ecotoxicological impacts of advanced wastewater treatments applied to the effluent from a WWTP after secondary treatment: ultrafiltration (UF), ultraviolet radiation (UV), ozonation (OZ), and non-thermal plasma (NTP). Ecotoxicity assays were conducted using Raphidocelis subcapitata (chronic tests) and Daphnia magna (acute and chronic tests), representing primary producers and consumers, respectively. For R. subcapitata, no significant growth inhibition was observed for most treatments, while growth was promoted due to the presence of nutrients, except for OZ, which produced inhibitory effects. In D. magna, acute toxicity was low for most treatments, except for OZ, which showed significant toxicity. An additional chronic exposure experiment was conducted for the NTP-treated effluent, inducing adverse effects on growth and reproduction of D. magna; in contrast, R. subcapitata showed no effects, demonstrating species-specific sensitivity and trophic-level-dependent responses. These findings demonstrate that although advanced oxidation technologies enhance water quality, they may cause sublethal and lethal ecotoxicity effects, highlighting the importance of ecotoxicological evaluations in risk assessment of quaternary treatments, framed by Directive (EU) 2024/3019.