Research On The Expansion Project Of The Municipal Sewage Treatment Plant

The design processing capacity of Xi’an fourth sewage treatment plant in first phase is250000m3/d, but the quantity of influent increase gradually since the plant had been put intooperation in November2008. At the same time, sewage pipe network of Caotan ecologicaldistrict is improved, recently30000m3/d (220000m3/d in the future) of sewage will beendischarged into the Xi’an fourth sewage treatment plant through the pumping station, and thetotal quantity of influent will be beyond the capacity of the plant. Futhermore, the effluent ofplant is drained Caoyun open channel, then eventually flow into the Weihe river. According tothe three years control plan of Shaanxi Weihe, and Xi’an fourth sewage treatment plant shouldbe held more heavy processing tasks, therefore, the expansion project of Xi’an fourth sewagetreatment plant as soon as possible is very necessary. This project is used the sameprocess(inverted A2O) as that in the first phase, and the main structures contain thick and finegird, aerated grit chamber, primary settling tank, biological reaction tank, secondarysedimentation tank, contacting disinfection tank, sludge disposal is used the methods ofgravity concentration+mesophilic digestion+mechanical dewatering, and finally the cakewas landfill.Moreover, sewage is a stable and reliable renewable water resource, sewage reuse is animportant way of water to solve the water shortage in cities, deep treatment of sewage can beused in industrial enterprises, municipal sanitation, landscape and urban river landscape, etc.The reasonable exploitation and utilization of sewage resources reflected the principle " theoptimal use of the high quality and low quality water " and " scientific, economic use of thewater resource". So, planning and construction of the reuse system is very necessary duringthe plant expansion.To choose the suitable process, the quality and quantity of influent is measured, and theplant operation in the first phase are analyzed. At last best suitable plant was determinedthrough comparison of several existing traditional mature process. At the same time, the planreserved a lot of space for reconstruction and sewage reuse.