Study On Flocculation And Sedimentation Of Cohesive Fine Sand Under The Action Of Flocculant

Flocculation is a common phenomenon in nature,which has a significant impact on the transport,distribution,and migration of substances in the water environment.Especially in the application of water treatment and environmental science,it has significant scientific significance and practical value.This article studies the static water flocculation and sedimentation characteristics of viscous fine sand under different sediment concentrations using a single flocculant and a composite flocculant through flocculation and sedimentation experiments;The optimal concentration dosage of single flocculant and composite flocculant under different sediment concentration conditions,as well as the optimal ratio of composite flocculant,were obtained respectively;Based on the floc settling rate formula established using the adsorption isotherm equation,a floc settling rate formula that can reflect the influence of changes in flocculant concentration and sediment concentration has been established.The specific research results are as follows:(1)Through the self-designed flocculation sedimentation experimental device,taking the flood siltation sediment in Yangling reach of Weihe River in Shaanxi Province as the research object,the sedimentation experiment was conducted under the condition of constant temperature of 20 ± 0.1 ℃.The sedimentation process of flocs was recorded by high-speed camera,and the floc sedimentation velocity of sediment flocculation sedimentation was analyzed,which can provide a rich data source for further analysis and determination of floc particle size,effective density and fractal dimension.(2)The experiment observed the flocculation and sedimentation process of viscous fine particle sediment with different concentrations under different single flocculant concentrations.The results show that the optimal concentration of inorganic polymer polyaluminum chloride flocculant PAC does not change with the change of sediment concentration,all of which are 0.08g/L;The optimal dosage concentration of organic polymer anionic polyacrylamide flocculant APAM is divided into two stable stages and one sensitive stage as the sediment concentration changes.The sediment concentrations in the two stable stages are 10-70kg/m3 and 80-90kg/m3,respectively.The optimal dosage concentration of the flocculant does not change with the sediment concentration,which is 0.08g/L and 0.1g/L,respectively.The sediment concentration in the sensitive stage is 70-80kg/m3,and the optimal dosage concentration of the flocculant can be selected using interval interpolation;The organic polymer cationic polyacrylamide flocculant CPAM is the most sensitive to sediment concentration.The optimal dosage of the flocculant is divided into three stable stages and two sensitive stages as the sediment concentration changes.The sediment concentrations in the three stable stages are 10-30kg/m3,40-60kg/m3,and70-90kg/m3,respectively.The optimal dosage of the flocculant is 0.08g/L,0.1g/L,and 0.12g/L,respectively.The sediment concentrations in the two sensitive stages are30-40kg/m3 and 60-70kg/m3,respectively,The optimal concentration of the flocculant can be selected using interval interpolation based on the experimental data of this study.(3)Through experiments on the flocculation and sedimentation process of sediment under different sediment concentrations and composite flocculant concentrations,it was found that the composite flocculant has better flocculation and sedimentation effects than a single flocculant.Especially when the ratio of inorganic polymer polyaluminum chloride PAC and organic polymer cationic polyacrylamide CPAM is 2:1,the flocculation and sedimentation rate of the composite flocculant is greater,and the expenditure is more reasonable,On the premise of ensuring the sedimentation rate of flocs,it can also save resources,and its floc particle size generation is larger,so the composite flocculant has a more prominent flocculation effect.(4)When the ratio of inorganic polymer polyaluminum chloride PAC to organic polymer cationic polyacrylamide CPAM is 2:1,and the sediment concentration is30kg/m3,60kg/m3,and 90kg/m3,respectively,the optimal dosage ratios of the composite flocculant are 0.08g/L,0.08g/L,and 0.1g/L.The optimal concentration of flocculants can be divided into two stable stages and two sensitive stages as the sediment concentration changes.The sediment concentrations in the two stable stages are 30-60kg/m3 and 60-90kg/m3,respectively.The corresponding optimal concentrations of flocculants are 0.08g/L and 0.1g/L,respectively;The sediment concentrations in the two sensitive sections are less than 30kg/m3 and greater than90kg/m3,respectively.The optimal concentration of flocculants can be selected using interval interpolation based on the experimental data of this study.(5)Based on the floc settling rate formula established using the adsorption isotherm equation,a floc settling rate formula that can reflect the influence of single flocculant concentration and changes in sediment concentration was established,using sediment concentration and flocculant concentration as parameter variables.By fitting the flocculent formula of different sediment concentration changes under three different types of flocculants,it can be seen that the flocculation coefficient is mainly determined by the sediment concentration and flocculant concentration;The relationship between flocculation coefficient and sediment concentration and flocculant concentration is a quadratic function;The fitting empirical formula R2 of flocculation coefficient of inorganic polymer polyaluminum chloride PAC,organic polymer anionic polyacrylamide APAM and organic polymer cationic polyacrylamide CPAM is 0.8225,0.7513 and 0.7991,respectively.Both of them have strong correlation.The experimental data validation shows that the formula has high calculation accuracy.