Increasingly, domestic and industrial wastewater has been. discharged into natural water system without sufficient treatments, worsening the self-Purification capacity . Dissolved oxygen concentration of the surface water would be remarkably decreased due to excessive. organics, nitrogen and phosphorus. Furthermore, eutrophication has severely affected the surface water quality and fishery. , And threatening human health in the. developing countries . Hardly-biodegradable, organic pollutants are refractory to be. removed , Degrading the organoleptic characteristics of surface water and even producing. Toxic by-Products with Chemical disinfectants . Subsequently, the water quality is deteriorated.