Study On Purification Of Heavily Polluted River Water By Contact Oxidation Bypass Treatment Process

With the acceleration of urbanization,urban rivers are seriously polluted,and the black odor of rivers is serious.Regardless of the needs of the people’s livelihood environment or the requirements of the national planning policy,the treatment and elimination of the black and odorous river channel has been very urgent.The bypass treatment technology has the advantages of quick effect and short construction period,and is widely used in the treatment of urban polluted rivers.Compared with super-magnetic separation,BAF,MBR and other bypass treatment technologies,coagulation sedimentation and contact oxidation bypa ss treatment technology have the advantages of low operating cost and simple operation and management.This topic selects the coagulation sedimentation-contact oxidation combination process through literature research,for a severely polluted actual river water in Shenzhen,and the main pollutants（COD,NH₃-N,SS,etc.）reach the Class A Standard of Pollutant Discharge Standards for Urban Sewage Treatment Plants to conduct a pilot test.On the basis of the small test experiment,carring out engineering construction and conducting follow-up studies to investigate its actual performance in engineering application;Aiming at the high cost of disposal of pharmacy and sludge in the production test to improve the technical.The results of the small test showed that the coagulation sedimentation-contact oxidation combination process had a good purification effect on the heavily polluted river water,under the optimal operating conditions of PAC dosage of 50 mg/L,gas-water ratio of 7:1 and HRT of 2 h,the main pollutants such as COD,NH₃-N and SS in the effluent can meet the Class A standard.The results of the productive test of the coagulation sedimentation-contact oxidation process showed that the process technology had a stabl e treatment effect on the heavily polluted river water in practical engineering applications,the main pollutants such as COD,NH₃-N and SS in the effluent can meet the Class A standard.The optimal operating conditions were:PAC dosage of 30⁶0 mg/L,the gas-water ratio of the contact oxidation biofilter was 10:1,the hydraulic retention time was 2.5 h,the backwashing cycle of the first-order contact oxidation biofilter was 4 d and the backwashing cycle of the secondary contact oxidation biofilter was 7 d.The running cost analysis showed that the actual project ton water cost was 0.965 yuan,and the pharmacy fee and sludge disposal fee account ed for a relatively high proportion,each accounting for about 1/3,and the alkalinity addition cost accounted for 76.92%of the total pharmacy fee.Aiming at the high cost of disposal of chemicals and sludge in the production test,proposing the pre-denitrification-contact oxidation combined process improvement proposal.The small test showed that the improved process has better processing effect and can save processing cost.Under the optimal operating conditions of reflux ratio of 150%,hydraulic retention time of 4 h and gas-water ratio of 5:1,the main pollutions such as COD,NH₃-N and SS in the effluent were all stable to meet the Class A standard.According to the actual engineering design scheme with a treatment scale of 3000 m³/d,compared with the coagulation sedimentation-contact oxidation process,the main investment cost of the pre-denitrification-contact oxidation process increased by 0.08 yuan,and the operating cost per ton of water was saved 0.5 yuan,the total cost of processing tons of water saved 0.42 yuan..