| As China’s urbanization process has been speeding up,the total amount of wastewater discharged continues to increase,while the treatment is lagging behind.According to China’s environmental statistics,the quantity of China’s wastewater discharged had reached to 73.5 billion tons in 2015,while the treatment rate was 80.1%.The removal rate of chemical oxygen demand（COD）and ammonia nitrogen（NH）in industrial wastewater and domestic sewage were only 70.2%and 38.9%.The treatment and disposal rate of sludge in a safe and harmless way was very rare,which seriously damaged the environment.Furthermore,the penetration rate of urban sewers was only 60%,which means the urban wastewater transportation and treatment capacity need to be improved immediately.The lagging of wastewater treatment has become a powerful resistance factor for China to achieve regional water pollution control,and has seriously restricted the sustainable development of society and economy.The State Council has released a series of policies and technical regulations related to wastewater treatment as well as a"schedule"for pollution control.A strengthened urban wastewater treatment,improved wastewater transportation and treatment capacity,and promoted sludge treatment and disposal are emphasized by the government.According to the macroscopic production process of urban wastewater treatment,this paper proposes a performance evaluation mechanism for urban wastewater treatment with multi-objective orientation.With static analysis and comparison of wastewater transportation and treatment capacity,treatment of wastewater and sludge,wastewater pollutant discharge,as well as the construction and decomposition of dynamic productivity,this study discovers the weak links in key environmental protection cities’wastewater treatment.Then according to their differences,this paper points out the priorities on wastewater treatment in different types of cities.The main research work and conclusions are as follows:（1）Proposing an analytical framework for wastewater treatment environmental production technology.Based on environmental production technology and combined with wastewater treatment processes,this study puts forward an environmental production technology of wastewater treatment:let operating costs,wastewater transportation capacity,quantity of wastewater discharged and wastewater treatment capacity as inputs,let the quantity of wastewater treated as desired outputs,while the quantity of sludge produced,quantity of CODand NH discharged as undesired outputs.The latter three variables are strong disposed.With this production technology,the static efficiencies of wastewater treatment under multi-objective guidance and the dynamic efficiency of total factor productivity of wastewater treatment are investigated.（2）Providing an evaluation mechanism for wastewater treatment with multi-objective orientation.Traditional efficiency evaluation is single-objective oriented and focuses on a particular aspect of wastewater treatment,which makes it hard to measure or compare the efficiencies among input-output variables,and the efficiency assessment would not be comprehensive.In this paper,a multi-objective orientation is proposed,that is the maximization of wastewater transportation and treatment capacity,the maximization of wastewater treated with the minimization of sludge produced,as well as the minimized quantity of wastewater pollutant discharged.With this orientation,the construction efficiencies of wastewater transportation and treatment capacity,the technical efficiencies of wastewater and sludge treatment,and the discharge efficiencies of wastewater pollutants are can analyzed in 68 megacities from 2006 to 2015.The results show that:the overall construction efficiency of wastewater transportation capacity in key cities is always lower than that of wastewater treatment capacity.Sludge treatment efficiency is significantly lower than that of wastewater treatment（except 2007）.The total discharge efficiency of COD and NH is similar and relatively low.The weaknesses existing in static wastewater treatment efficiencies are wastewater transportation capacity,sludge treatment and wastewater pollutant discharge（especially COD）.（3）Applying decoupling analysis and LMDI approach to wastewater treatment research.Decoupling analysis and LMDI decomposition are often applied to the study on CO2 emission.By extending Tapio decoupling concepts,this paper constructs decoupling models respectively between urban population and wastewater transportation or treatment capacity,economic development and the quantity of wastewater treated or sludge produced,economic growth and wastewater pollutants discharge.Then the decoupling relationship between variables is judged according to the redefined decoupling state.The results show that:during the decade from 2006 to 2015,there is a strong expansive coupling between urban population and wastewater transportation capacity in China’s key cities,as well as the wastewater treatment capacity,and the latter has a higher decoupling value.The decoupling state between economic development and the quantity of wastewater treated or sludge produced is strong expansive coupling as well,but the latter state is not optimal.On the contrary,the optimal strong decoupling appears between COD discharge and economic growth,while the overall state between NH discharge and economic growth is weak expansive decoupling.Furthermore,a simple additive LMDI decomposition method is adopted to investigate the influence of each driving factors.The results indicate that:the intensity of wastewater transportation（treatment）capacity construction,wastewater（sludge）treatment and pollutant control are major driving factors respectively for the growth rate of wastewater transportation and treatment capacity,the quantity of wastewater treated and sludge produced,and the quantity of wastewater pollutants discharged.（4）Proposing SBM and Luenberger index to decompose the total input and output factors of wastewater treatment productivity.With Malmquist or Malmquist-Luenberger productivity index to analyze the total factor productivity,the contribution of each input output variables cannot be examined.Based on Liu&An,this paper combines the SBM model and Luenberger productivity index to estimate and decompose the dynamic wastewater treatment performance.Through this approach,the influence factors of total factor productivity,efficiency improvement and technology progress can be analyzed systematically.The empirical results show that:the pollutant discharge,such as sludge,COD and NH,mainly contributes to the inefficiency of wastewater treatment in China’s key cities.In the analysis period,the growth of total factor productivity of wastewater treatment in key cities mainly stems from the improvement of efficiency rather than technological progress,while the efficiency amelioration depends more on the improvement of pure efficiency rather than the change of scale efficiency.The productivity of different regions are quite different.The sequence of TFP is the Middle region>the Northeast>the East>the West.Owing to the reduction of pollutant’s discharge,the TFP of wastewater treatment reveals a growth from 2006 to 2015.The improvement of wastewater treatment efficiency is mainly attributed to the quantity of wastewater treated and NH discharged,while the progress of technology is mostly related to COD discharged. |
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