Study on a comprehensive evaluation method for the assessment of the operational efficiency of wastewater treatment plants

A fuzzy matter-element model, combined with the entropy weight of an index, has been used as an evaluation method to achieve a comprehensive assessment and analysis of the operational efficiency of wastewater treatment plants (WWTPs). The feasibility of the method had been validated based on actual operational data and instance from eight WWTPs located in a city in Northern China. According to the results of the comprehensive evaluation, the operational efficiency of the WWTP using an anaerobic/anoxic/oxic process was generally better than other wastewater treating technologies. And especially, the removal efficiencies of nitrogen and phosphorus pollutants were much higher for the process, which suits well the actual operational situation of Chinese WWTPs. Total nitrogen (TN) removal rate and the productive quantity of the excess sludge cake were identified as important factors in the evaluation of the operational efficiency for a WWTP. So the operation level of WWTP could be improved by increasing the TN removal rate and decreasing the excess sludge cake quantity. The developed method can evaluate and analyze the operational efficiency scientifically and objectively, and the evaluation results can be used to guide the construction, operation and management of WWTPs in The Three Gorge reservoir district of China.