Design Of Upgrading And Extension Project Of Sewage Treatment Plant In Yixian County

Yixian County is located in the southwest of Liaoning Province.In recent years,with the great strides in industrialization and the expansion of urban development,the total amount of domestic wastewater and industrial wastewater generated and discharged has gradually increased.Although the first phase of the Yixian sewage treatment plant has been put into operation,most of the existing sewage discharge directly causes serious pollution of urban rivers,which not only pollutes the urban environment but also pollutes the groundwater resources and endangers human health Regional economic development.In addition,the sewage is discharged into the Daling River through the urban water body,which has brought serious impact on the living of the residents along the coast.The ecological balance of the water body is also threatened.Therefore,it is necessary and meaningful for the design and construction of the scale extension of Yixian sewage treatment plant.This paper has carried out the design and research work for the Upgrading and Extension of Sewage Treatment Plant in Yixian County with 20 million m³/d.The influent water quality of the plant is COD_Cr 340mg/L,BOD₅170mg/L,suspended solids 210mg/L,total nitrogen 45mg/L,ammonia nitrogen 2 mg/L and total phosphorus 5mg/L,which is biodegradable better high turbidity water.Therefore,the wastewater treatment process designed in this paper is:first-level pretreatment+second-level biochemical treatment+advanced treatment+disinfection.Among them,the primary treatment uses coarse grid?sewage lifting system?fine grid?swirling grit chamber.The secondary treatment reformed the original A/O process and added the A²/O process.At the same time,it used an activated sludge-suspended filler composite process?MBBR?to enhance nitrogen and phosphorus removal;the advanced treatment process selects micro-flocculation+filtration process,after it was processed and then into the filter cloth filter;chlorine dioxide was used to disinfect the treated sewage,the sludge generated in the whole process was transported,and finally the stacked screw-type sludge dewatering machine was selected and used.Processing.The plant's optimal wastewater treatment process was finalized:influent?coarse grid?sewage lifting system?fine grid?swirling grit chamber?modified A/O and newly built A²/O biochemical pool?MBBR membrane pool?chlorine dioxide disinfection?daling river.Sludge treatment process:biochemical pond surplus sludge+MBBR membrane pool sludge?sludge buffer pool?sludge thickening and dewatering?sludge shed?mud cake transport.The quality of the effluent treated by this process can reach the Class A standard in the“Emission Standard of Pollutants for Municipal Wastewater Treatment Plants”?GB18918-2002?.Among them,the specific parameters of the design were as follows:?1?The first-phase treatment plant of the wastewater treatment plant has already set up a first-class treatment structure,and the accounting met the requirements for the upgrading of this standard.Therefore,no new construction is required,and the existing rotary coarse grid was still used.Rotary fine grid,swirling grit chamber.?2?The modified A²/O biochemical pool process parameters were as follows:a new A²/O biochemical pond with a mixture concentration of 3.2 g/L,an anoxic section with a capacity of 420 m³,a residence time of 1.01 h,and an anaerobic section.The pool capacity was 820m³,and the residence time was 1.97h.The anoxic stage pool capacity was 940m³ and the residence time was 1.88h.The aerobic stage pool capacity was 4380m³ and the residence time was 8.76h.?3?One new secondary sedimentation tank with a diameter of 25m and a residence time of 3h.?4?The maximum dosage of PAC is 60mg/l,the average dosing amount is 25mg/l,and the dosing concentration is 10%;the chlorine dioxide disinfection method is adopted for the effluent,and the average dosing amount is considered to be 7mg/l.There are two sets of chlorine dioxide generators in the chlorination room and one is prepared by one.The preparation capacity is:Q=5000g/h,N=3.0kW.The process plan of the wastewater treatment plant in this paper could reduce the BOD₅ volume by about 1,168 tons/year,the COD_Cr volume by about 2,117 tons/year,and the SS volume by about 1,460 tons/year.The total investment of the plant was451,027,000 yuan.It has been assessed that the internal rate of return of all investment in the project is higher than 5%,and the investment recovery period is less than 15 years.With the general awareness of environmental protection,the construction of urban drainage facilities has gained public support and public sentiment.The construction of the sewage treatment project has been prepared for the construction of the sewage treatment plant technically,economically,and financially,so the project is necessary and feasible.