Microplastics-derived dissolved organic matters accelerate photodegradation of sulfamethazine in wastewater ultraviolet disinfection process

• Photodegradation of antibiotic was enhanced by dissolved organic compounds from microplastics. • Photosensitization of quinone and aromatic structures in MP-DOM caused the critical effects. • •OH and 1 O 2 were the key species in the combined photodegradation of SMT by MP-DOM. • Only •OH with lower concentration was detected and worked in single SMT system. • The fate of pollutants in wastewater and environment will be affected by co-existing MP-DOM. As an extensively detected pollutant in wastewater, microplastics (MPs) can produce abundant dissolved organic matter (DOM) in wastewater treatment, especially in ultraviolet (UV) disinfection, which may further affect the fate of antibiotics. This study collected the DOM from photoaging of polystyrene, polypropylene and polyethylene terephthalate (MP-DOM), and investigated the effects and mechanisms of MP-DOM on the photodegradation of sulfamethazine (SMT) during UV disinfection. Results showed that three MP-DOM all accelerated photodegradation of SMT, with degradation rates from 0.0057 min -1 in single system to 0.0077−0.0090 min -1 in combined systems. The critical effects were mainly related to the photosensitization of quinone and aromatic structures in MP-DOM, which absorbed UV energy to generate abundant reactive oxygen species (ROS). •OH and 1 O 2 were the key species to enhance photodegradation of SMT, but different producing abilities of ROS by various MP-DOM mainly depended on the components of DOM. Besides, the photodegradation of SMT was enhanced by MP-DOM more significantly in real wastewater due to the synergistic effect of wastewater components and MP-DOM. This study firstly revealed the important role of MP- DOM in the degradation of antibiotics, which will deepen our understanding of the environmental behavior of MPs with the associated products more holistically.