AN EXPERIMENTAL STUDY ON HIGH EFFICIENCY INTERCEPTION AND PURIFICATION FOR URBAN RAINWATER

In response to the water environment pollution caused by direct discharge of polluted rainwater into water bodies, an integrated collection and purification facility of rainwater was developed based on physical-chemical treatment in an unattended manner. The enhanced coagulation and sedimentation had been conducted onto the polluted rainwater by the facility’s operations such as rainwater collection, coagulant addition, aeration stirring and sedimentation. The study results showed that when PAC, with dosages of 150, 200, and 250 mg/L were respectively added to the polluted rainwater of three different concentrations, and the hydraulic retention time was 4.5 hours, the removal efficiencies of SS, COD and TP were more than 95%, 75% and 72%, respectively. The SS, COD and TP in effluent met the Class I-B standard of GB 18918—2002. Meanwhile, over 82% of total zinc and total lead removal rates were achieved by the facility, and the removal efficiency for total aluminum was 73% above. Moreover, the mass concentration of total zinc and total lead in the effluent of the facility was much lower than the maximum allowable emission concentration in GB 18918—2002. Additionally, the peak mass concentration of dissolved oxygen could reach 9.04 mg/L during the aeration stirring phase. The mass concentration of dissolved oxygen in discharged water was 3.75 mg/L. The treatment cost of the facility was RMB 0.08~0.11 yuan/m³ of polluted rainwater. The processes of mixing, reaction and separation were integrated through the facility, which realized the requirements of technical feasibility and economic rationality.