Analysis And Research On Runing Effect Of The Upgrading And Reconstruction In Xi’an Fifth Sewage Treatment Plant

The study is based on the Xi’an fifth sewage treatment plant upgrade project and aims tostudy the actual quality of the wastewater. It analyses the operating results before upgradingand then comes to a proper upgrade program through comparison. Also, it analyses the waterquality and operating results of the principal structures after upgrading in order to seekproblems and therefore propose solutions. The study reaches the following conclusions:1. The project of water in this plant conforms to the national level1-B standard beforeupgrading, but the removal rate of SS and TP are still not up to the standard, including thatthe SS is23%and TP is12%, this phenomenon restricts the normal operation and the waterquality of the plant seriously, also it increases the difficulty for the reconstruction of project inthe future.2. In order to upgrade the current situation of the plant, it is necessary to improve A2/Oreaction pool and increase the number of filter clothes and filter pools. Optimizing the currentsituation of treatment process and strengthening each processing unit are able to achieve thegoal of optimizing water quality. After three months of renovation, the removal rate pollutantsincreased significantly, the project of water have already conformed to the national level1-Astandard, including COD, SS, TN,NH3-N were97.6%,98%,78%and97%respectively, butthe TP was still not up to standard, the rate was33%.3. As we monitored and analyzed the running effect of the principal structures afterrenovation, we found that the effect of biological nitrogen removal was good between thebiological nitrogen and phosphors removal process in the plant, but the effect of phosphorusremoval rate was not good. After analyzing the cause, we suggested that it was required toreinforce platoon mud within the scope of the process, at the same time, to pay attention tothe DO control, and to provide good external conditions for microbial phosphorus removal.During the analysis of the effect of the cloth filter, we found that it would have obvious effectof the removal rate of SS when the plant increases the cloth filter, the average removal ratecan reach36%, further reduce the SS concentration, as well as optimize the effluent waterquality.4. According to the occasional situation of the exceeding standard of TP, it suggests to start the chemical phosphorus removal system, through the experimental analysis of this study,it can be made the following recommendations: Adding flocculants to the secondary settlingtank is able to reduce the amount of work, to make full use of chemicals, and to avoid thecase of sludge bulking. Through the comparison of the three common chemical flocculants, itis concluded that under the effect of different dose, the polymerized ferric chloride showsbetter removal effect, in the case of the optimal dose, the removal rate can reach65%, thebiggest TP concentration can be reduced to0.48mg/l. After the analysis of economic costs,treatment effect, it can be concluded that polymerized ferric chloride can be chosen asflocculent during the chemical phosphorus removal process in the plant.