Abstract:Rural sewage treatment is an important task of the New Rural Construction in China, which also plays a key role in improving the rural ecological environment. In this study, using system dynamic (SD) model and Powell optimization model, a SD-Powell coupled model with simulation and optimization function was set up to simulate and predict the amount of pollutant discharge, and to establish the functional relationship of pollutant reduction and cost. Taking Changzhou City in Jiangsu Province as a case study, the calculated results indicate that COD and ammonia emissions will reach up to 16583 t and 2551 t in 2020 respectively, increased by 4.60% and 4.59% compared to 2008. The 51 towns in Changzhou City were divided into four categories of control units using clustering method. The treatment cost functions for COD and ammonia in different control units were obtained, with the treatment cost in four units varying from 348 kg to 413 kg per ten thousand Yuan RMB for COD, and 54 kg to 65 kg per ten thousand Yuan RMB for ammonia. The total cost will be 168.7 million RMB Yuan if the pollutant reduction rate in the whole area reaches 100%. The results show that the pollutant reduction rate by cost optimization was better than the cost average allocation. Compared to average allocation results, the method used in this study could increase reduction effectiveness of the two pollutants COD and ammonia by 6.4% and 7.4%, respectively. The optimal treatment cost was between 10and 168.7 million RMB per year under different reduction rates and the treatment cost for priority unit was in the order of I>IV>II >III.