| The existing sewage treatment plant generally has the problems such as low operating efficiency, low standard rate, blind expansion of scale, inadequate facilities, inadequate operation management. TPS method is used to analyze the technical, economic and environmental benefits of the seventh sewage treatment plant in Kunming City. At the same time, it points out the shortage of the plant in the process of operation combined with the material flow and energy flow analysis. And AHP is used to integrate technical, economic and environmental indicators for a comprehensive evaluation in order to provide technical reference for the planed and built sewage treatment plant.The comprehensive evaluation index system of urban sewage treatment plant was established through three aspects, including technical benefit, economic benefit and environmental benefit. AHP method was used to integrate the technical indicators, economic indicators and environmental indicators to carry out a comprehensive evaluation for the urban sewage treatment plant, and the score was 83, indicating that the overall operation of the plant was good.The influent quantity and NH3-N concentration was relatively stable, but the concentration fluctuations of other pollutants concentrations were large. The treatment process had a good treatment effect on COD, BOD5, SS, NH3-N, TP, but the removal of TN needed to be improved. The stability of effluent NH3-N, BOD5, TP were poor, but the standard rate was greater than 95%. The fluctuation of other effluent concentration such as COD, SS, TN is small. The average value of TN was close to the limit, and the standard rate was less than 95%. Therefore, the nitrogen pollutant index was to be the focus of control, and the optimization measures should be further developed.Material balance analysis showed that the carbon balance rate was 67%, in which the removal efficiency of COD was 19.4% in the denitrification process, suggesting that it could not be ignored. Nitrogen balance rate was 99%, with removed of 57.7% in the denitrification process. The key of strengthening TN removal was to improve the denitrification process. Moreover, pollutants removal contribution of the anaerobic/anoxic process should be considered in A2/O process design and operation process, and it plays a guiding role in reducing operating costs and environmental impact. Phosphorus balance was 28.9%, indicating that TP could not be removed effectively in the process of biochemical treatment, and the removal was mainly depended on chemical removal process.Electricity costs was the first in the overall cost, the unit electricity cost of the sewage was 0.203kwh/m3, relatively low. The correlation of the electricity cost and the influent quantity and the amount of pollutant removal was poor. The management and control of the main energy consuming equipment in the plant had certain hysteresis. The second was the cost of reagents, which mainly concentrated in the sludge treatment and advanced treatment process. Chemical cost of unit sludge was 102.1yuan/m3. The correlation daily removal CODeq and dried mud quantity change was not significant. According to the characteristics of influent quality and quantity, the real-time control of operation parameters and process equipment was the key to energy saving and consumption reduction.Unit Flow EP was 0.006kg PO43-/m3, TN is the largest source of EP emissions, accounting for 81% of total emissions, indicating that the plant should be further optimization of nitrogen removal. The annual amount of GHG was 2.6 ×107kgCO2eq/yr, the power consumption was the largest source of GHG emissions, accounting for 57% of the total emissions. Energy flow analysis showed that the energy consumed in the process accounted for 90% of total energy consumption, which the energy in denitrification and biological oxidation process consumed 15% and 26.9%, respectively. |
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