Comparative efficiency of oxidation processes to remove acesulfame in water treatment plants supplied by surface water sources

Abstract

Abstract The effects of oxidizing agents during water treatment on the concentration of an artificial sweetener were evaluated in full-scale conditions. Five drinking water treatment plants (DWTPs) located in a northern environment with high seasonal variations which use different raw water sources and different combinations of oxidants (ozone, chlorine, UV radiation) were investigated through the removal of the artificial sweetener acesulfame (ACE) along their treatment chains. In total, 98 sampling campaigns were conducted at these DWTPs. Raw water (impacted by variable tidal and hydrodynamic conditions), partially treated water within the DWTPs, and fully treated drinking water were sampled during eight months over the period of higher variability of source water quality. Results showed ACE concentrations in raw waters vary on a seasonal basis: higher in winter and summer (when rivers have low water discharges) and lower during spring and fall. Multi-barrier treatment systems under study were effective for the removal of acesulfame due specifically to the effect of ozone and chlorine during oxidation steps, while no removal was observed using physico-chemical (coagulation flocculation, filtration) and UV treatments. Depending on the number of treatment steps that involved ozonation or chlorination and the position of these oxidative processes in the treatment chain, removal of ACE varied from 24% to 90% in the plants under study. The results indicate that increasing oxidant doses would result in better removal of ACE and other contaminants, but these strategies must consider unknown transformation products, potentially with greater toxicological effects than their precursors.