Ecotoxicity evaluation and removal of sulfonamides and their acetylated metabolites during conventional wastewater treatment.

The present study describes the evaluation of the risk posed by the occurrence of sulfonamides (SAs) in wastewaters. A fully automated analytical method based on on-line solid-phase extraction-liquid chromatography-tandem mass spectrometry (on line SPE-LC-MS/MS) was developed, validated and applied for the analysis of sixteen SAs and, for the first time in wastewaters and sewage sludge, five of their acetylated metabolites. Influent and effluent samples from twenty two different wastewater treatment plants (WWTPs) in Catalonia (Spain) and sewage sludge from fifteen of them were analyzed; removal rates (RE%) and half-lives (t(1/2)) for each SA were calculated. The estimated correlations between RE% and to the hydraulic retention time (HRT) of the different plants indicated no clear influence of HRT on removals. Sulfamethoxazole (SMX), sulfapyridine (SPY) and their corresponding acetylated metabolites were detected with the highest frequencies of detection and at the highest concentrations. The ecotoxicity of both SPY and AcSPY was evaluated for the first time through bioluminescent inhibition assays, resulting in a higher toxicity being attributed to the metabolite. Finally, the potential environmental risk posed by the levels of SAs detected was evaluated calculating the hazard quotients (HQ) to different non-target aquatic organisms in treated wastewaters. SMX was the only SA posing a risk to algae, with an HQ>10.