Are combined AOPs effective for toxicity reduction in receiving marine environment? Suitability of battery of bioassays for wastewater treatment plant (WWTP) effluent as an ecotoxicological assessment

• The selected battery of bioassays to assess the different WWTPs' effluents is recommended.
• Multibarrier treatment (MBT) reduced the toxicity of the tested effluents.
• pT–Value confirmed the toxic reduction in the effluents after the MBT.
• Mortality of Sparus aurata and the embryo-larval of Paracentrotus lividus are the most sensitive bioassays.
• D2 and D3 were the most toxic WWTP regarding the pT-Method scale.

Ecotoxicological assessment of three different wastewater treatment plant (WWTP) effluents D1, D2 and D3 was performed before and after tertiary treatment using combination of advanced oxidation processes (AOPs). A multibarrier treatment (MBT) consisting of microfiltration (MF), hydrogen peroxide photolysis (H2O2/UVC) and catalytic wet peroxide oxidation (CWPO) was applied for all effluents. Sparus aurata, Paracentrotus lividus, Isochrysis galbana and Vibrio fischeri, representing different trophic levels, constituted the battery of bioassays. Different acute toxicity effects were observed in each WWTP effluents tested. The percentage of sea urchin larval development and mortality fish larvae were the most sensitive endpoints. Significant reduction (p < 0.05) of effluent's toxicity was observed using a classification pT-method after MBT process. Base on obtained results, tested battery of bioassays in pT-method framework can be recommended for acute toxicity preliminary evaluation of WWTP effluents for the marine environment.

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