Study On The Process Design For The Second Phase Construction Of Second Waste Water Treatment Plant In Xi'an

The second sewage treatment plant includes 150000 m3/d scale secondary treatment and 50000 m3/d of the depth of treatment, and put into operation in 2003 and in 1998 respectively. With the continuous development of urbanization, in order to control pollution, subject to control plan of the Weihe River, the existing facilities of the second wastewater treatment plant can not meet the scope of existing services to form the sewage flow. Hence, construction of Phaseâ…¡expansion project is necessary without delay. This paper analyzed and determined the requirement on water quality and quantity for the second phase expansion. Comprehensive comparative analysis recommended the second phase of the sewage sludge treatment process; on the reactor for water treatment process characteristics and the main parameters of analysis and calculation; on the treatment process and optimization of the main structures for comparison. The following results were obtained:(1) water pipe network with water penetration, coupled with the system flow measurement method, and further adoption of new accounting status of facilities, water quality treatment capacity, wastewater treatment tank to determine the scale of the second phase of 20 million m3/d, final scale of 45 million m3/d by 2025;â…¡phase of the depth of processing does not increase, forward to 25 million m3/d.The use of Minitab statistical software, the Anderson-Darling normality test was used to test the distribution of water quality data sequence and found sewage indicators in line with normal distribution, lognormal distribution of individual compliance; by cumulative frequency analysis, water quality is recommended BOD5=240mg/l, CODcr=450mg/l, SS= 380mg/l, NH3-N=35mg/l, TP=7.5mg/l.(2) To address water quantity and quality requirements as the basis, with status quo, program selection from the three treatment options recommended by the anaerobic pond+DE oxidation ditch process. And consider the first and second sludge, recommended temperature level in the gravity concentrate+anaerobic digestion+mechanical dewatering of sludge treatment process.(3) The load method of sludge, sludge age method and the method to calculate the kinetic parameters compared to determine the oxidation ditch volume of 162,243 m3, anoxic volume: oxidation ditch volume is 0.30; by operation cycle 8h, a cycle, each ditch aeration 5.5h, hypoxia 2.5h.(4) Using the technology of sewage treatment Operating cost of 0.55 yuan/m3, engineering has good social and economic benefits. (5) Manpower status of one, two and medium size and may increase the drainage standards, phased construction of the wastewater treatment plant layout planning, and strive to smooth the various convergence of technology, stage construction of the least interference.