Advanced oxidation processes (AOPs) are mainly used for treating refractory industrial wastewater such as chemical, pharmaceutical, printing and dyeing, and pesticide wastewater. They are also widely applied in landfill leachate treatment, advanced treatment and upgrading of municipal wastewater plants, and drinking water purification. In addition, AOPs are suitable for wastewater reuse, zero-discharge pretreatment, decolorization, deodorization, and removal of persistent organic pollutants, antibiotics, and micro-pollutants. They also play an important role in oilfield produced water treatment, medical wastewater disinfection, and circulating water treatment.