Construction And Application Of Validation Method For Evaluating The Suitability Of Coagulants For Waterworks

In recent years,the development of coagulant industry in China is very rapid.However,at present,the selection and evaluation means of coagulants are relatively simple,so the coagulants suitable for the target water body cannot be selected quickly and accurately.Therefore,it is of great theoretical and applied value to establish the evaluation model of coagulants for screening coagulants and ensuring the safety of water supply.In this paper,various types of aluminum coagulants were used to carry out the corresponding coagulation test study on the water of the diversion reservoir?Queshan reservoir?with different water quality characteristics,and the removal efficiency and flocculation characteristics of each index were analyzed,and several representative evaluation indexes were selected.SPSS mathematical analysis software was used to summarize and analyze the experimental results,and finally the representative test indexes used in the evaluation model were determined.A comprehensive evaluation model for coagulant screening was established by fuzzy comprehensive evaluation method.On the basis of the existing problems of water supply plants,a complete set of flocculant evaluation and validation method is constructed by using the established evaluation model,and the application is verified by taking the actual water plant as an example,which provides theoretical support for the evaluation of coagulants,model construction,selection of reagents and dosage adjustment of water supply plants in the future.Firstly,a variety of aluminum coagulants were used to conduct a coagulation beaker test on water of Yellow River diversion reservoir with different water quality characteristics,to explore the changes of various indexes and the corresponding flocculation characteristics when different agents were used,and to screen the model evaluation indexes according to the test results.Comprehensive experimental results show that the turbidity,TOC,fluorescent water indexes such as organic matter and the types of drugs and dosing amount is a strong correlation,and the coagulation effect is good reflection ability,after considering the turbidity,COD_Mn,UV₂₅₄ removal efficiency and so on three conventional index as a model for evaluating the representative indexes of coagulation effect.In addition,through the study of flocculant characteristics,it is found that flocculant particle size,fractal dimension and other indicators are closely related to flocculant coagulation effect.Finally,two special indexes,Zeta potential and flocs particle size,were selected as alternative indexes.After using SPSS mathematical analysis software to analyze the index correlation,it is found that Zeta potential and flocs particle size are highly correlated with the three selected conventional indexes,and the correlation coefficient is above 0.7,and there is no substitution relationship with other indexes.Therefore,turbidity,COD_Mn,UV₂₅₄,particle size and Zeta potential were selected as the main evaluation indexes of the model after comprehensive consideration.Fuzzy comprehensive mathematical analysis method is selected as the basic method to construct the model,and the traditional method is supplemented and modified by expert evaluation and analytic hierarchy process to ensure the reliability of the model.The gorsi distribution function is used as the main method to calculate the membership degree.Through expert evaluation and hierarchical analysis,the weight of each evaluation factor(turbidity,COD_Mn,UV₂₅₄,particle size and Zeta potential)was finally determined to be 0.098,0.16,0.062,0.417 and 0.263,respectively.In addition,after the model was built,it was also used to evaluate and verify three coagulants,namely,polyaluminum chloride,aluminum sulfate and polyaluminum chloride,under the same conditions.The results showed that the evaluation results of the three coagulants were as follows:?0,0.16,0.223,0.263?,?0,0.0939,0.223,0.263?and?0.417,0.205,0.263,0.16?.The comparison shows that the evaluation result of PAFC is the best,followed by PAC,which is the same with previous research results,indicating that this model is relatively scientific and effective.In this paper,a set of flocculant evaluation and verification method suitable for water supply plants is established,which can be used to evaluate and verify the coagulant and dosage used in water supply plants at the present stage.The system starts with the applicability of coagulants,USES the established evaluation model to evaluate the coagulants suitable for the target water body,and then tests the product eligibility.After the end of the beaker test,the pilot test is introduced to verify the system,which effectively avoids the safety risks and unnecessary economic losses caused by the direct use of coagulants in production.System practical application results show that:the raw water turbidity is 2.9⁹.8 NTU,COD_Mn is2.25³.45 mg/L,polyaluminium chloride?PAFC?iron coagulant for the target water has better applicability,beaker and pilot test results showed that the agent the best additive quantity of 4 mg/L,but the comprehensive analysis of its treatment effect and economic index,find to add content increases the marginal benefit is not ideal,not equal to 2 mg/L.The production verification test also verified this conclusion.Under the condition of 2 mg/L dosage,the removal rates of turbidity,TOC,COD_Mn and UV₂₅₄ were 89.87%,7.5%,33.01%and 44.57%,respectively,and the effluent effect could reach the national standard stably.By comparing the system verification results with the actual operation of the water plant at the present stage,it is found that the coagulant and dosage selected for the water plant at the present stage are scientific and reasonable.