Motivation of reactive oxygen and nitrogen species by a novel non-thermal plasma coupled with calcium peroxide system for synergistic removal of sulfamethoxazole in waste activated sludge

Large amounts of antibiotics are concentrated in waste activated sludge (WAS) and released into the environment. It is thus critical to develop advanced sludge treatment technology to remove these antibiotics. Dielectric barrier discharge (DBD) combined with calcium peroxide (CaO2), as an innovative technology to attenuate sulfamethoxazole (SMX) in sludge, was investigated. Evident synergistic effects between DBD and CaO2 were observed on the SMX degradation with a synergistic factor of 2.02. Moreover, the energy consumption of DBD/CaO2 was significantly lower than that of DBD alone. At a typical CaO2 dosage of 0.1 g/g TS and discharge power of 64.5 W, the highest SMX removal of 96% was achieved within 50 min. The synergistic effects of DBD/CaO2 could be associated with the base catalysis of H2O2 and O3, UV-base-photolysis, peroxone oxidation, and photocatalytic H2O2. DBD/CaO2 generated various reactive oxygen species (ROS) and nitrogen species (RNS) that participated in SMX removal. The contributions of these reactive species followed the sequence of e- > •OH > •O2- > 1O2 > ONOO-. Based on the detected transformation by-products and their variations during treatment, a plausible SMX degradation pathway in sludge was proposed. Besides, DBD/CaO2 also promoted sludge disintegration, dewatering, heavy metal removal, sludge reduction, sludge solubilization, and acetate-enriched volatile fatty acid (VFA) production. Therefore, DBD/CaO2 exhibited great potential for controlling antibiotic, as well as promoting sludge reduction, decontamination, and resourcization.