Study On Seasonal Variation Trend Of Water Quality Of Mudan River Downstream And The Emission Reduction Benefit Of Nitrogen And Phosphorus Of Sewage Treatment Plant

The comprehensive evaluation research on the variation trend of aquatic environment quality is one of the most important bases to work on water pollution control planning and rational use of water resources. It is the construction of urban centralized sewage treatment plants that makes sure the healthy water cycle by reducing pollutants emission. In this thesis, the Mudanjiang sewage treatment plant was taken as the research subject and systematic study was conducted on nitrogen and phosphorus emission reduction as well as environmental benefits based on the operational condition of the treatment process. The research results will provide a valuable reference for the emission reduction of urban drainage in China.This study combined cluster analysis with principal component analysis method to analyze the seasonal variation of pollution factors in the lower reaches of the Mudanjiang River Basin. Besides, environmental function area weighted grey correlation method was adopted to comprehensively evaluate the water quality in different water periods. The variation of water quality in Mudanjiang with different water periods and sections was well known by investigation and research, which will supply basic data to the estimation of emission reduction circumstance in Mudanjiang sewage treatment plant.Based on existence form and variation trend of nitrogen and phosphorus pollutants in on-site monitoring section in the lower reaches of the sewage treatment plant, the prediction models of different section between the section of Mudanjiang sewage treatment plant and Chai river bridge section in Mudanjiang were established, combined with one-dimensional and two-dimensional water quality prediction model, before its application to the water quality estimation with advanced treatment.The model can not only predict the variation of water quality with time and space but also provide scientific instruction for nitrogen and phosphorus emission reduction. The study result indicated different degrees of emission reduction of nitrogen and phosphorus pollutants at sections downstream with advanced treatment in the sewage treatment plant.To explore the influence on water quality caused by nitrogen and phosphorus pollutants desorbed from the sediment downstream the Mudanjiang sewage treatment plant section, the water samples and corresponding sediment samples were simulated in laboratory. It turned out that the sediment between the research section posed no threat to the water quality in phosphorus concentration. In fact, sediment still had some adsorption capacity for phosphorus from the point of loosely absorbed inorganic phosphorus. Whereas the concentration of ammonia nitrogen and total nitrogen both reached the standard value and there is even a rise in the section of Hualin town. To strengthen the research on treatment effect of total nitrogen and ammonia nitrogen in Mudanjiang sewage treatment plant will decrease the sediment of nitrogen and reduce the risk of secondary pollution on water caused by desorption of nitrogen pollutants in sediment.The study on influence of different factors showed: while the ambient temperature rose and the concentration of dissolved oxygen reduced, the amount of ammonia nitrogen released from sediment to overlying water increased, and the concentration of ammonia emitted from wastewater treatment plant should be strictly controlled. when the ambient temperature was low or high, or at anaerobic conditions, the amount of TP release was larger, and the concentration of TP release should be strictly controlled. When the downstream water was under the stirring condition, the amount of other pollutants (Ammonia, nitrate, total phosphorus) besides orthophosphate release increased, pollutants emission concentration should be strictly controlled to prevent sediment from polluting overlying water body.