| In China,the deterioration of water environment has resulted in the general shortage of water resources and serious ecological consequences.According to the current technical research,long-distance water delivery,desalination treatment,urban sewage recycling can be used as an important supplement to clean water sources.Daqing is located in the inland closed area,and its water resources are relatively poor.With the acceleration of urban construction,the water demand for residents’ living,industrial and agricultural production will increase year by year.For Daqing City,the reuse of sewage after advanced treatment is more important than the development and construction of new self-propelled water source,because it is more in line with the objective reality of poor water in Daqing city.Therefore,it is of great significance to reuse the discharged water of sewage treatment plant after advanced treatment and develop the second water resource of Daqing city.In this project,a sewage treatment plant in Daqing Oilfield is selected as the research water plant.The water quality of the water plant is relatively stable and reliable,but due to the aging of equipment,weak automation capacity and its own process and other factors,the nitrogen and phosphorus in the water quality sometimes exceed the standard.The main reason for the low removal efficiency of total nitrogen is that the carbon source of the sewage treatment plant is not enough.When the sewage treatment plant was initially set up,methanol was added to the denitrification filter as the carbon source.Then,methanol is highly toxic and volatile,which brings potential safety hazards to the health of employees and the production of the unit.Therefore,the sewage treatment plant did not add any carbon source to denitrification,so the denitrification filter of the sewage treatment plant is only It plays a filtering role and fails to realize the denitrification function.Firstly,in view of the actual problem that the total phosphorus emission of the factory water exceeds the standard,three kinds of dephosphorizing agents,polysilicate aluminum chloride,polyaluminium chloride and polyaluminium ferric chloride,are tested in beaker and field.Finally,adding 80 mg / L PAC as coagulant,the removal rates of SS and TP in the effluent of sedimentation tank are 60.3% and62.1%,respectively.The effluent TP is less than 1mg / L,and the effluent ss of the sedimentation tank is about 90 mg / L,which can effectively remove SS and TP in the reaction tank.Through the test,it is finally determined that 8h will be used as the sludge scraping cycle of daily production and operation when the polyaluminium chloride with the dosage of 80 mg / L is used as the coagulant.Secondly,according to the actual situation of denitrification filter without carbon source,the paper compares the use of sodium acetate and glucose in denitrification filter,and explores the effect of different dosage of chemicals on denitrification effect.When the carbon nitrogen ratio of sodium acetate is 5.5,the denitrification effect is the best,the removal rate of total nitrogen is 81.3%,and the TN of effluent is less than 15 mg / L.When the ratio of glucose,carbon and nitrogen is 7,the denitrification effect is the best,the removal rate of total nitrogen is 76.5%,and the TN of effluent is less than 15 mg / L.Therefore,from the actual treatment effect,the carbon source sodium acetate has more advantages.After the feedback results of the preliminary commissioning of the subject water plant,it is shown that the effluent TP can be reduced to 1mg / L and TN can be reduced to below 15 mg / L by adding appropriate coagulant and carbon source with appropriate carbon nitrogen ratio.The experimental study on the removal efficiency of quartz sand filter and quicksand filter is carried out on this basis.Through the commissioning,start-up,operation and optimization of the two experimental devices,further reduce the SS,BOD5,TN,TP and other indicators in the effluent,and compare the effluent with the water quality standards such as landscape water and green water.In the study,it is found that both experimental devices can further remove the pollutant index in the influent.In consideration of the factors such as no backwashing process,high load resistance and stable effluent effect of the quicksand filter compared with the quartz sand filter,the research of the project is determined to make the water plant reach the standard of medium water reuse,and the quicksand filter is better than the quartz sand filter.By carrying out the above research work,the water plant can ensure the sewage treatment effect from the aspects of phosphorus removal agent and carbon source selection,dosage control,etc.according to the commissioning results of quartz sand filter and flow sand filter experimental device,it can be concluded that Daqing sewage recycling is feasible. |
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