Optimization of nimesulide oxidation via a UV-ABC/H 2 O 2 treatment process: Degradation products, ecotoxicological effects, and their dependence on the water matrix

Abstract Nimesulide (Nim) degradation in ultrapure water (UW) and municipal sewage (MS) via UV-ABC/H 2 O 2 was investigated. The variables included in the experimental design were time, initial Nim, and initial H 2 O 2 concentrations. Resulting decreases in Nim concentration (monitored by high performance liquid chromatography (HPLC) using a photodiode array detector operating at a maximum UV absorbance of 300 nm), mineralization (from total organic carbon (TOC) measurements), and ecotoxicity (assays employing the bioindicators Daphnia similis , Artemia salina , and Allium cepa ) were also studied. Degradation rates of 90% or higher were found for 15–20 min reaction times, employing combinations of [H 2 O 2 ] = 50–150 mg L −1 and [Nim] = 8.5–15 mg L −1 prepared with MS. Mineralization rates of 70% and higher were attained within 60 min of reaction for [Nim] = 15 mg L −1 prepared in MS with [H 2 O 2 ] = 100 mg L −1 . Nim by-products were detected and possible degradation pathways proposed. Ecotoxicity evaluation using A. salina , D. similis , and A. cepa revealed that the treated samples had significantly lower toxicity. Exposure to treated samples resulted in survival rates of 79% for A. salina and over 90% for D. similis . No root growth inhibition was observed in A. cepa exposed to treated samples, whereas exposure to untreated samples inhibited root growth by 60%. Statistical analysis revealed elimination of cytotoxicity and reduction of genotoxicity against A. cepa . The results showed that the UV-ABC/H 2 O 2 process can be employed as a pre- or post-treatment method to remove Nim from contaminated wastewater.