Kinetic degradation of anti-inflammatory drugs in ozone combined free active chlorine system

Abstract In this study, free active chlorine (HOCl/OCl-, FAC) was employed as an activator of ozone (O3) to remove typical non-steroidal anti-inflammatory drugs of aspirin (ASA) and phenacetin (PNT). The combination of FAC and O3 significantly improved the removal of pollutants. O3 molecules, hydroxyl radicals (·OH) and reactive chlorine species (RCS) contributed to the removal of target contaminants in O3/FAC system. By fitting the pollutant removal pattern with the experiment and model, the contribution of each oxidative species in O3/FAC system was measured. The average removal contribution of O3, ·OH, and RCS to ASA/PNT was 10.3%/8.4%, 53.8%/10.5%, and 35.9%/81.1%, respectively. Compared with O3 alone system, the average mineralization of pollutant in O3/FAC system increased from 20.6% to 34.0%. The formation of five typical CX3R-type disinfection by-products (DBPs) was evaluated with post-chlorine system. The maximum concentration of total DBPs was achieved at pH 6.0 of 12.5 μM, in which trichloromethane (TCMs) was the main component (accounting for 55.3%). This study provides a new method to remove contaminants based on the combination of O3 and FAC disinfectants.