Occurrence of Emerging Contaminant Acesulfame in Water Treatment System and Its Degradation during Ozone Oxidation

The occurrence of acesulfame (ACE) in two full-scale drinking water treatment plants (DWTPs) in Zhejiang Province, China, was investigated. The results showed that ACE was commonly detected in the raw water of the DWTPs at ND–0.125 and ND–0.093 μg/L, respectively. The maximum ACE removal efficiencies in the DWTP with traditional processes were less than 10%, whereas those in the DWTP with advanced ozonation treatment were 36.70–79.59%. Consequently, ACE degradation by ozone and the key influencing factors were examined. Laboratory-scale experiments were performed and revealed that ACE degradation followed a pseudo first-order kinetics pattern under all reaction conditions. The decomposition rate relied heavily on applied ozone dosage rate, pH, reaction temperature, and the presence of water matrix constituents. Higher ozone input, alkaline conditions, and higher temperatures favored ACE removal. Among four anions tested, CO₃^2- exhibited a greater inhibitory effect on ACE decomposition than the other three, namely Cl⁻, HCO₃⁻, and SO₄^2-, did. Scavenging tests confirmed that direct ozonation accounted for ACE degradation under acidic conditions, whereas the hydroxyl radicals produced by ozone under alkaline conditions gradually promoted ACE degradation with increasing pH. These findings demonstrated that ozonation is a technically viable technology for eliminating ACE from drinking water sources.