Performance Evaluation Of Urban Sewage Treatment Plants

In recent years,the construction of urban sewage treatment plants in China has developed rapidly.At the same time,disparitities in operation results and management quality have occurred in various plants.Therefore,it is urgent to establish a performance evaluation system to monitor and improve the operation of urban sewage treatment plants.In this study,data envelopment analysis(DEA),analytic hierarchy process(AHP)and life cycle assessment(LCA)are used to carry out scientific and effective evaluation on urban sewage treatment plants from multiple aspects,with a view to provide more choices and references for decision-makers and managers.It is expected that this work will promote the application and development of sewage treatment performance evaluation in China.Firstly,an SBM-DEA model based on cluster benchmarking is established to evaluate 861 sewage treatment plants in China.The average efficiency score of the sample plants is 0.611.Among them,170 samples are relatively efficient,which can be regarded as the best practice and benchmark in China’s sewage treatment,and provide improvement targets for inefficient plants through the projection at the frontier.Judging from the improvement rate,there is still more than 30% room for saving in the three input indicators.The Kruskal-Wallis test shows that the influent COD concentration and capacity load rate have significant influence on the plant performance.Secondly,a comprehensive performance evaluation of eight sewage treatment plants in Wuxi demonstration area is conducted based on the AHP method,involving four criterion-level elements and fourteen indicators.The performance scores and ranking of related projects are obtained,and the stability of evaluation results is proved by sensitivity analysis.From the perspective of various indicators,these eight plants have poor performance and large differences in indicators such as sewage reuse rate,sludge production,and infrastructure costs,which need to be paid more attention.In addition,MSBR and MBR processes are recommended for small and medium sewage treatment projects,and AAO processes are selected for large sewage treatment projects.Finally,this study integrates the life cycle environmental impact and life cycle costing to evaluate four typical sewage treatment processes in China.The results show that the trends of the four technologies on eleven environmental impact types are basically the same.Marine aquatic ecotoxicity potential contributs the most to the overall environmental impact,accounting for more than 70%.Contribution analysis indicates that electricity and flocculant consumption are the main processes responsible for the environmental and economic burden.AAO process is the optimal sewage treatment scheme with the smallest potential environmental impact and economic load.