Study On The Upgrading And Reconstruction Of Wastewater Treatment Plant In The Zhashui

The "Discharge standards of water pollutants for key industries of Hanjiang and Danjiang River Basin in Shaanxi Province"(DB61/942-2014) has been implemented in Shaanxi Province, Since May 1,2015. The standard clearly stipulates that the effluent of municipal wastewater treatment plant whose effluent quantity is larger than 2000m3/d executes the level A in first grade standard of " Discharge standard of pollutants for municipal wastewater treatmentplant "(GB18918-2002). Located in Zhashui Danjiangkou Hanjiang River Basin Conservation Area, the Zhashui wastewater treatment plant’s effluent quality can be up to standard of the level B in first grade before reconstruction. But due to the implementation of the new standard, its effluent quantity can not be up to the standards of the country and local region. When the effluent is discharged into the QianYou River, the water quality of Han River basin will be polluted deeply. Therefore, the treatment facility must be redesigned and reconstructed to make sure that the effluent quantity is up to the standard of level A in first grade.First of all, this article analyzes a series of process used in the wastewater treatment at home and abroad, introduces the process used in the wastewater treatment plant of Zhashui at present, and points out some problems existing in the wastewater treatment plant. Secondly, based on the detailed analysis of the data of quality and quantity influent and effluent in the wastewater treatment plant of Zhashui, the optimum design about water quality and Technology Programme is put forward, introducing The process, process characteristics and design parameters of the optimum solution are also introduced detailed in this article. The main conclusions of this article are as follows:(1)The actual water quality of effluent in Zhashui wastewater treatment plant is up to the standard of level B in first grade. The quantity of effluent in quo: COD=27.7mg/L, BOD5=11.9 mg/L, SS=13 mg/L, NH3-N=4.4 mg/L, TN=9.3 mg/L, TP=0.7 mg/L. The COD, NH3-N and TN are close to standard of level A in first grade.(guaranteed rates are 98%, 78.3% and 100%, respectively), the guaranteed rate of BOD5, SS and TP reaching the standard of level A in first grade is not high(the guaranteed rates are 18.9%, 10% and 5.5%, respectively).(2)The removal efficiency of all indicators in Zhashui wastewater treatment plant renovation project are: COD≥83.4%, BOD5≥94.5%, SS≥90%, NH3-N≥80%, TN≥62.5%, TP ≥92.8%, and emphasis lies in four indicators: BOD5, NH3-N, SS and TP. The aim to improve the removal efficiency of SS and TP can be achieved by adding advanced treatment system(chemical phosphorus removal, sedimentation, filtration, etc.). By transforming the biochemical treatment system, NH3-N and BOD5 removal efficiency can be improved.(3)The transformation of Zhashui wastewater treatment plant for biological treatment systems are as follows:(1)increasing a blower with the same performance in the blower room, which can improve aeration amount to 86.6m3/min, and replacing the aerobic zone head of the CAST tank;(2)replacing the high-speed stirrer in the CAST anaerobic pool area with perfect installation;(3)adding a return pump station in the aerobic zone of the CAST tank, making the mixture reflux ratio increases to 150% to 200 %, strengthening denitrification capacity;(4)puting 100 mm diameter filler suspension in the aerobic zone of the CAST tank, and the total dosage is 1925m3, accounting for 25% of the tank volume.(4)The advanced treatment system after secondary biochemical treatment system will be added. The process of coagulating sedimentation + filtration + UV disinfection(original) will be recommended after technical and economic comparison to remove SS and TP further. With the SS concentration reducing, other contaminants will be removed too.