关键词： 污水处理；氧化沟；污泥脱水

Plant design of urban sewage treatment up to 20 tons per day

Design general specification: The design is designed to deal with the wastewater of a medium-sized town, and the sewage plant is mainly responsible for the domestic sewage of the city. The design scale is daily treatment of 200,000 m3 of municipal wastewater. The water quality of the influent is: COD:~390mg/L, BOD5:~190mg/L, SS:~390mg/L, NH3-N:~50 mg/L, TN: ~65mg/L, TP: ~6mg/L. The treated wastewater is discharged into the nearby rivers, and its water quality complies with the secondary standards in the "Standard for Discharge of Pollutants from Municipal Wastewater Treatment Plants" (GB18918-2002). The specific content is: COD: ≤ 100 mg/L, BOD5 : ≤ 30 mg/L, SS: ≤ 30 mg/L, NH3-N: ≤ 25 mg/L, TN: - mg/L, TP: ≤ 3 mg/L, pH: 6~9.

Design standards:

Urban Pollutants Discharge Standards (GB 18918-2002)

"Outdoor Drainage Design Code" (GB 50014 - 2006)

"Sewage Recycling Engineering Design Code" (GB 50335-2002)

"Urban WWTP Auxiliary Buildings and Subsidiary Design Standards" (CJJ 31-89)

Design principle: Select the process and equipment with low operating cost, advanced technology, and reliable operation. Under the precondition of ensuring the quality of the effluent water body to reach the standard, try to save the cost of civil engineering; select the process technology and equipment selection, and fully consider the management Simple, easy to operate and convenient equipment maintenance to ensure that the entire processing system can be long-term and efficient and stable operation; strive to safe and secure, economical and practical, reduce labor intensity and operating costs; layout of the plane should be reasonable, close, try to save space, try to Use existing pipelines. The use of reliable and effective new materials and new technologies; the optimization of pipe network design methods suitable for retrofitting projects to optimize the layout of pipelines. Sewage treatment plants should prevent or minimize odors, noise, solid waste pollution, etc., to prevent further pollution of the environment.

Main technical material: This design selects Carrousel oxidation ditch process. The Carrousel Oxidation Ditch combines anaerobic, anoxic, and aerobic processes in a pool. Each part is pided into different systems through partition walls, but there are inseparable links between them. The process effectively utilizes the feature that the sewage can circulate in the oxidation ditch, so that the aerobic zone is successfully organically combined with the anoxic zone, and no dynamic reflux is achieved, and the mixed liquid required for removing the nitrate nitrogen will be removed. The energy consumption of the reflux is saved. Carrousel Oxidation Ditch has been widely used due to its ideal nitrogen and phosphorus removal capability, ability to resist impact loads, and ease of operation and management.

The content of this design specification includes comparison and selection of different process schemes for sewage treatment, clear process flow, design and calculation of major structures, layout and calculation of elevation of wastewater treatment plant, layout details of wastewater treatment plant plane, and economic analysis of the project, etc. . The main process of sewage treatment is: Medium grid - sewage lifting pump room - fine grid - grit chamber - oxidation ditch - second settling tank - UV disinfection - effluent. The main processes for sludge treatment are: sludge concentration - sludge dewatering - mud cake transport.Grid: Consisting of a series of parallel metal grids or screens, it can trap large suspended solids, fibers and solid particles, so as to ensure the normal operation of the subsequent processing unit and the water pump, and the subsequent treatment of various structures. The load is reduced, avoiding the obstruction of the sludge discharging pipeline.Sewage lift pumping station: The level of sewage can be increased to ensure that the sewage can flow smoothly through the entire process of sewage treatment and finally complete the treatment of wastewater. Grit chamber: It is used to remove some inorganic particles such as sediment with relatively large relative density (about 2.65) and particle size exceeding 0.21mm to avoid the impact on the smooth operation of subsequent structures.Oxidation ditch: Also known as the circulating aeration tank, it is changed by the activated sludge process and essentially belongs to delayed aeration activated sludge system.Sedimentation tank: For further separation of suspended solids, the sewage discharged from the oxidation ditch has basically been treated with organic pollutants, but there is still a large amount of sludge and flocs, etc. The precipitation and sedimentation of the sedimentation tank can precipitate the sludge. The bottom of the pool, and the clear upper water can be discharged into the disinfection tank.Disinfecting the pool: kill pathogenic bacteria in the water and some unhealthy microorganisms.Sludge thickening pool: Liquid sludge that has a moisture content of more than 95% is discharged from the secondary settling tank. After the reaction in the concentration tank, the moisture content in the sludge can be reduced and the volume of the sludge can be reduced. After the sludge concentration significantly reduces the volume of the sludge, the filter press system with a filter press is used to dry the sludge, further reducing the volume and weight of the sludge and facilitating the transportation to make it solid.