Evaluation Model Construction And Early Warning System Development Of Urban Black And Odor River

Urban black and odor rivers have the characteristics of low DO concentration,high concentration of organic pollutants and NH₃-N,usually accompanied by water turbidity and peculiar smell,they have a greater impact on urban landscape and river ecosystem.At present,there is a risk of rebound in the governance of black and odor rivers in cities.The establishment of a long-term guarantee mechanism can effectively prevent the recurrence of black and odor rivers.As an important means in the long-term guarantee mechanism,the black and odor early warning system often uses the evaluation model as the research basis.The main control factors of black and odor in urban rivers are screened out,the models for black and odor evaluation are established,the dynamic physical model of urban rivers is constructed,and the threshold value of black and odor early warning is established.Finally,the early warning system for black and odor in urban rivers is developed,the main contents were summarized as following:（1）We investigated and sampled the black and odor rivers in 11 cities of Sichuan Province,and conducted an indoor analysis.It is found that the black and odor do not always occur at the same time;The surrounding environment has little influence on the physical and chemical factors of the river.By means of Correlation Analysis,One-way ANOVA and Factor Analysis,the main control factors of blackening in urban black and odor river channel are COD,TFe and DO,and the main control factors of blackening are TP,COD,NH₃-N and DO.（2）According to the characteristics of black and odor river pollution in the city,the independent evaluation model of black and odor water was established.In the traditional model evaluation of the surveyed rivers,it is found that the evaluation results of different models vary greatly,and there are limitations in the independent evaluation of black and odor.In this paper,the fuzzy comprehensive evaluation model is improved by MATLAB.NH₃-N,COD,TP and DO are used as the factor set of the improved fuzzy comprehensive evaluation model,and the optimization analytic hierarchy process is introduced to realize the odor evaluation of urban rivers.Based on Python language,a blackness evaluation model based on K-means clustering is developed,and gray model is introduced to quantify the blackness.The actual accuracy of the evaluation is 85.7%.（3）The physical model of urban river was constructed,and the indoor experiment of black and odor in urban river was carried out under different organic pollution concentration load.It is found that the blackening and stinking of water bodies do not occur at the same time,and they do not always exist at the same time,this difference is closely related to the concentration of iron and sulfur in water;Water self-purification ability is poor under high organic pollution concentration;When the organic wastewater load is more than 0.9 g/L,it will exceed the self purification capacity of the water body.and the water body can not eliminate black and odor by means of reoxygenation under such conditions;Combined with Multiple Linear Regression model,the screening value and control value of water body odor are 27.2 and 34 respectively,and the screening value and control value of blackness are 29.6 and 23.7 respectively.When 27.2≤OT≤34,the water body has the risk of stinking,when 23.7≤CH≤29.6,the water body has the risk of blackening.（4）The early warning system of black and odor river course in the city has been developed.The system is based on Python development environment,black and odor water evaluation model and early warning threshold,third party libraries such as Py Qt,Numpy and Matplotlib are combined,the database of black and odor river pollution based on SQLite is established to provide data support for the system.And put forward the construction principle of urban black and odor water body early warning system operation mode.