Study On The Sewage Treatment Design In Multi-industry Towns In South Of The Yangtze River

Development of small towns gradually moving to multi-industry coexist type, while the rapid development of a variety of industrial enterprises, the water pollution problems have become increasingly prominent, especially more pronounced in the southern river network-intensive areas, it has caused the local government and the masses attention. Sewage treatment plant is the last pass of urban sewage treatment, scientifically established design criteria and selection process is not only fundamentally affected the urban sewage treatment plant effluent quality whether the target, but also for operational stability after the completion of sewage treatment facilities, maintenance and management cost also have a profound effection. As for sewage feature multi-industry co-existed more complex small towns vary its sewage treatment system process design put forward higher requirements.This topic selected the typical southern region multi-industry coexist small town in Kunshan city, Palestinian cities and towns Shipai Business Park Sewage Treatment Plant Phase II expansion project designed to expand the research, including the status of running Shipai sewage treatment plant project analysis, phase II water determination, water quality demonstration analysis, comparison and design parameters of the second phase of treatment process optimization, a transformation of structures design process, and complete the engineering design.Shipai sewage treatment plants and sewage runoff include a variety of industrial-based industrial wastewater, sewage and industrial effluent water ratio of 4: 6. Design flow is 12,000 m3/d, the first part was 5,000 m3/d, and the second part is 7,000 m3/d. According to the water quality monitoring data in Shipai sewage plant project from 2012 to 2013, determined the design water quality main indicators BOD5、COD、SS、 NH3-N、TN、TP were: 220mg/L、400mg/L、200mg/L、35mg/L、25mg/L、5.5mg/L. According to "the Taihu Lake area of urban sewage treatment plants and key industrial sectors major water pollutant discharge limits"(DB32/1072-2007) limited standard, determined the implementation level of the sewage plant effluent indicators Class A standard, treated water is discharged to the final Maosha river.Through the comparison in technology and economic, the engineering sewage treatment process chosed mechanical pretreatment /Hydrolysis/CASS biological treatment and depth treatment combined process. For sewage treatment plant influent water quality changes and complicated situation, the traditional design parameters to optimize the adjustment. In CASS process as the core technology and detailed process design, it summed up a set of design parameters with a reference value. The main structures hydrolysis acidification tank design of water: 12,000 m3/d, effective volume: 5000rn3, the residence time is 8 hours, the size is 28.0x25.0x7.7 m; CASS biological pool for a pool in building a comprehensive formula by biological selection area, and oxygen zone and the main reaction zone of three parts, divided into four groups. CASS reactor volume ratio anaerobic zone: anoxic zone: the main reaction zone is1: 5:30, design sludge load 0.15 kg BOD5/kg MLSS · d; Mixture concentration is 3500mg/L, sludge age is 20 d, sludge reflux ratio of from 30% to 50%. CASS pool reaction the total effective tank volume is 4666m3; single-cell single effective volume is 1167m3. CASS reaction cell single-cell design size: 30.0x8.0x6.0m; effective depth is 5.0m; Decanter height is 1.25 m. Finally, the paper analyzed from the engineering economic, energy and environmental protection projects benefit in three aspects.Shipai sewage treatment plant during the renovation, to ensure the stable operation of the first phase of the project, the second phase project commissioning water quality standards are stable, operational data indicate that the sewage treatment system for BOD5, COD, SS, NH3-N and phosphorus have better removal, the indicators are to meet the "Taihu Lake area of urban sewage treatment plants and key industrial sectors major water pollutant discharge limits"(DB32/1072-2007) limit standard, and has a high resistance to shock loading capabilities. Processing system can reduce annual COD 1635 tons, SS 902 tons, NH3-N 127 tons, and more than 18 tons of total phosphorus.CASS process as the core of the mechanical pre-treatment/ hydrolysis acidification /CASS biological treatment solutions/depth treatment process are suitable for river area more intensive industries co-exist small town sewage treatment, sewage treatment plant for the diligent process parameter adjustment is successful design experience can provide reference for similar urban sewage plant.