| So far, there is still lack of effective and comprehensive methods for evaluating biological wastewater treatment systems. Taking a typical industrial wastewater biological treatment plant as an example, based on life cycle assessment (LCA), in this work an integrated approach was established for evaluating this plant in ther terms of the material and energy flows. The material and energy flows of carbon, nitrogen and phosphorus elements were analyzed on the basis of single-element regional observation and mathematical modeling methods. In this study, the LCA method, Fuzzy recognition approach and grey relational model were integrated to assess the potential environmental impact, performance and energy consumption of the wastewater treatment plant (WWTP), and a new method with a consideration of index system of environmental impact, energy recovery and operation performance for the comprehensive evaluation of WWTP was established. The main contents and results of this work are as followed:1. On the basis of in-depth analysis of anaerobic and aerobic units of the WWTP, a new method accounting for material and energy flow balance analysis was established by an integration of single-element regional observation and mathematical modeling methods. This method is found to be very effective to analyze the material and energy flows within the anaerobic and aerobic units.2. The results of material and energy flows analysis of the WWTP showed that the organic matters decomposed by microorganism in the anaerobic unit were mainly conversed into methane (CH4), followed by carbon dioxide (CO2), and only a small part for the synthesis of cells. Most of internal energy into the system was converted into the internal energy. In the aerobic unit, proportion of carbon into excess sludge was highest with a nitrogen distribution into residual sludge, denitrification and effluent. On the other hand, total phosphorus was mainly converted into the excess sludge with the dissipation and heat accounting for the larger proportion of the system internal energy. 3. With the hybid LCA system of flow and energy flow analysis, the environmental impacts of the WWTP during one-year period (July,2008-June,2009) was investigated. The results showed that the comprehensive index of environmental impacts for the anaerobic unit was lowest in February,2009 (97.89) and highest in August,2008 (112.50). On the other hand, the comprehensive index of environmental impacts for the aerobic unit was lowest during the period of August,2008 (12.34) and highest in December,2008 (13.45).4. With Fuzzy recognition approach and grey relational model, the operating performance and energy consumption of the WWTP were investigated. The results showed the optimization point for the anaerobic unit appeared in August of 2008 and the optimization point for the aerobic unit in February of 2009. Energy utilization ratio of anaerobic system was the biggest factor affecting the energy consumption, while carbon balance and organic acids in the effluent had relatively less impact on energy consumption. COD removal efficiency in the aerobic unit was the biggest factor affecting power consumption, followed by nitrogen and phosphorus. The results is useful for improving the WWTP operation.5. A new method with a considearation of index system of environmental impact, operational efficiency and energy recovery for the comprehensive evaluation of the WWTP was established and the optimized working conditions for the anaerobic and aerobic units were achieved. The comprehensive evaluation of the anaerobic unit was the best in July of 2008, and followed by August of 2008, while became worse from September to December of 2008. The LCA comprehensive evaluation results of the aerobic unit were in large fluctuations. The comprehensive evaluation index was higher in December of 2008, January and February of 2009, which was optimum operating time for the aerobic unit.
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