Optimization Designing For Upgrade Of Hejing Sewage Treatment Plant

The problems which urban sewage treatment plants in Xinjiang encounter with atpresent are the renovation and expansion of original process, and many adoptoxidation pond process with the structure of the soil pond. On the design of suchworks, there need more considerations than new constructions, therefore a scientificand feasible method for these designs must be adopted.On the basis of site survey of sewage treatment plant in Hejing County,combined the evaluation of the existed sewage treatment plant and processing power,this paper proposes different solutions, and optimizes the selected gifted program byemploying scientific decision-making method. It will provide technical support for theupgrading and transforming of sewage treatment plants in Hejing County, at the sametime, provide reference for similar sewage treatment plant upgrading in Xinjiang.The main research methods and conclusions of the study are as follows.(1)Due to adopting the structure of soil pond, most of the designs of primarysettling tank in oxidation pond process have alternate structures, but the wall bearingcapacity is weak, and cannot carry on mechanical cleaning into the pool, so you mustremove cleaning residue manually; in addition, the management ability to execute insmall town sewage treatment plant is poor, and they usually do not dredge sludgetimely, making organic compounds merment in pools, which generates order gascontaining hydrogen sulfide gas, so produces secondary pollution. Therefore thispaper recommends not to use the primary settling tank process or to adopt reinforcedconcrete structure of the cell body instead when mentioning standard expansion.(2)In order to install HDPE film on oxidation pond wall, the wall inclined slopeis1:2or less. Compared with the equal area of concrete pond, its pool volume is muchsmaller. Mentioned standard expansion project is intended to expand the pool capacity,which will increase the cost of land acquisition, so new reinforced concrete pool canbe considered on the basis of the original soil pond.(3)Due to the fragile structure of the oxidation pond soil pond wall, we cannotinstall the equipment, but general aerators are always installed in the wall, so thechoice of aerator is the difficulty of the reform of oxidation pond aeration tank. By contrast the enhance aeration and suspension chain aerator, we found the latter investsless, and there are more applications.(4)This paper uses the net present value method to evaluate the project economicindicators, finding out that project investment costs and operating costs are the maineconomic indicators impacting the net present value; and uses table method to checkout the investment cost of the project, estimated operating costs in accordance withthe norms, calculated for different program’s net present value, the best option is theone whose net present value is the biggest. Select the project net present value of thisproject, but due to the lower parts of Xinjiang, land acquisition costs, moreeconomical use of the original cell body. The main factors are land acquisition costs,pool depth and water charges costs.(5)By AHP comparison between the alternative processes, we found thecomprehensive evaluation of oxidation ditch is better. Mainly due to thecharacteristics of the Xinjiang region, i.e. the winter is cold; the quality of urbansewage treatment staff is lower, coupled with the limited local funds, which lead toproject stability, the operation oxidation ditch process and the basis of investmentcosts become the main factors affecting these works. Therefore, the weight ofoxidation ditch process for the evaluation of the above factors is higher.(5)Net present value method and AHP joint decision-making process mentionedstandard oxidation pond expansion project works more objective, taking into accountthe multi-objective factors scene, making the process more scientific selected to meetthe practical requirements of the scene, with some promotional value.(6)When designing a process, we should be based on the actual situation to selectoxidation ditch type. Due to the higher pool depth, easy insulation and small footprint,Carrousel oxidation ditch is the preferred type; besides, we need to select the optimumparameters. We should calculate transformation biological pool of sewage pollutantremoval is calculated the sewage removal of pollutants in the transformationbiological pool, the calculated result of which is the design parameters of the designof the new bio-pool.In this paper, Xinjiang urban sewage treatment plant expansion project mentioned standard study design approach and decision-making methods anddevelopment of Xinjiang region fully into account the characteristics of the designproject more economical, less secondary pollution, more stable and meet localrequirements for the transformation of the Xinjiang region to provide similarreference from the wastewater treatment plant.