Multi-objective Optimization Model of Sewage Treatment Plants Based on NSGA-II Algorithm.

It is important for regional sustainable development that how to enhance the sewage treatment capacity of cities and improve river water quality. This paper took the Nanming River n Guiyang as the study area, built a one-dimensional coupling simulation modal of water quantity and quality based on MIKE 11 software to study the distribution of ammonia-nitrogen concentration and the causes of water pollution. Also a multi-objective optimization modal of sewage treatment plants was constructed n consideration of cost and water quality for man polluted reaches, setting cost minimizing and water cleaning as optimization goals, and NSGA- II algorithm was adopted to quantitatively analyze the correlation between the investment of sewage treatment plants and ammonia-nitrogen concentration of the river. Then the multi-objective optimization scheme of sewage treatment plants was recommended. The results are shown as follows. 1 There are three areas where the ammonia-nitrogen concentration exceeds the standard, with a total of 5 .23 km of reaches polluted, mainly polluted by Plant 2,Plant 13 and Guancheng River. 2 According to the optimization model, the reasonable investment of the sewage treatment plants should be 628-~850 million yuan, with the maximum ammonia-nitrogen concentration between 1.39 mg/L and 1.50 mg/L. For every 0.01 mg/L decrease of ammonia-nitrogen concentration in the river, the investment of the sewage treatment plants needs to increase by 20 million yuan. 3 The discharge water quality of plant 2 and plant 13 is proposed to improve from the first-level A standard to the quasi-IV class, and four optimization schemes are proposed for the new sewage treatment plant to meet the multi-objective optimization scheme settings of the sewage treatment plant under different needs. [ABSTRACT FROM AUTHOR]