Abstract:Pollution from dewatered sludge affects municipal sewage treatment plants′ survival and development, and different intermediate water disposal methods have different impacts on the local water resources and environment. Therefore, it is important to study the comprehensive performance of sewage treatment and explore measures on promoting its sustainability through constructing a sewage treatment ecological system composed of a sewage treatment system, a dewatered sludge disposal system and a intermediate water disposal system. Emergy analysis method has been used to analyze this complicated system. The traditional emergy analysis method ignores the impacts of wastes disposal and discharge and has been improved for evaluating a sewage treatment ecological system. Ming-jing-tan sewage treatment ecological systems projects proposed, as cases, were analyzed by traditional and improved emergy analysis methods. The results show that the improved method is more practical for evaluating a sewage treatment ecological system; the nonrenewable resources emergy ratio (NR) and discharged wastes emergy ratio (WR) have the largest impacts on the sustainability, next comes from intermediate water reuse emergy ratio (IR)., The sewage treatment ecological system′s sustainability mainly depends on the three factors′ common contribution; wastes reuse can increase the sustainability of the sewage treatment ecological system. Different methods of wastes reuse have different impacts on the entire system′s sustainability due to different wastes reuse degree and different nonrenewable resources consumption; the emergy sustainable index (ESI) of the project “dewatered sludge land-filling + intermediate water discharge” is the lowest (0.32) and the ESI of the project “dewatered sludge making aerobic compost + intermediate water reuse” is the highest (1.05) among the eight projects proposed.