S₂O₈^2-/UV-C and H₂O₂/UV-C treatment of Bisphenol A: Assessment of toxicity, estrogenic activity, degradation products and results in real water

The performance of S₂O₈^2-/UV-C and H₂O₂/UV-C treatments was investigated for the degradation and detoxification of Bisphenol A (BPA). The acute toxicity of BPA and its degradation products was examined with the Vibrio fischeri bioassay, whereas changes in estrogenic activity were followed with the Yeast Estrogen Screen (YES) assay. LC and LC-MS/MS analyses were conducted to determine degradation products evolving during photochemical treatment. In addition, BPA-spiked real freshwater samples were also subjected to S₂O₈^2-/UV-C and H₂O₂/UV-C treatment to study the effect of a real water matrix on BPA removal and detoxification rates. BPA removal in pure water was very fast (≤7min) and complete via both H₂O₂/UV-C and S₂O₈^2-/UV-C treatment, accompanied with rapid and significant mineralization rates ranging between 70% and 85%. V. fischeri bioassay results indicated that degradation products being more toxic than BPA were formed at the initial stages of H₂O₂/UV-C whereas a rapid and steady reduction in toxicity was observed during S₂O₈^2-/UV-C treatment in pure water. UV-C treatment products exhibited a higher estrogenic activity than the original BPA solution while the estrogenicity of BPA was completely removed during H₂O₂/UV-C and S₂O₈^2-/UV-C treatments parallel to its degradation. 3-methylbenzoic and 4-sulfobenzoic acids, as well as the ring opening products fumaric, succinic and oxalic acids could be identified as degradation products. BPA degradation required extended treatment periods (20min) and TOC removals were considerably retarded (by 40%) in the raw freshwater matrix most probably due to its natural organic matter content (TOC=5.1mgL^-1). H₂O₂/UV-C and S₂O₈^2-/UV-C treatment in raw freshwater did not result in toxic degradation products.