The Influence Of Floc Morphology Characteristics On The Prediction Of Membrane Fouling In The Coagulation-ultrafiltration Process

At present,coagulation ultrafiltration technology is widely used in drinking water treatment because of its high retention and easy operation.However,membrane fouling is still a key problem hindering its development and application.The essence of membrane fouling is the interaction between pollutants and membrane surface.At present,the prediction and analysis of membrane pollution mainly adopts the XDLVO theory system.However,the application scope of the theory is limited and the application conditions are different from the actual interface.In this paper,the floc surface morphology is introduced to consider the influence of interface roughness on membrane pollution The situation of membrane fouling under different solution conditions and roughness was analyzed by energy angle prediction.Although XDLVO theory can predict and analyze membrane fouling to a certain extent,the morphology of floc surface will have a greater impact on the prediction results in the process of coagulation.In this study,the surface of rough humic acid(HA)flocs was simulated by sine wave sphere model,and the interface interaction energy between different rough degree of HA flocs and PVDF membrane was quantitatively simulated by SEI junction,xdlvo theory and composite Simpson rule,so as to make up for the shortage that only two smooth planes could be analyzed by xdlvo theory alone.The fitting degree of energy calculation results and experimental results under different roughness conditions is 0.85,0.89 and 0.91 respectively,which can reach above 0.85,.That means the model is suitable for the simulation of the interaction energy of floc interface in coagulation membrane filtration system,and the fitting degree of rough floc is higher than that of completely smooth floc and membrane pollution trend,that is to say,the introduction of floc surface morphology can characterize the membrane pollution trend by the interaction between floc and membrane interface A higher degree of confidence.In addition,considering that the surface of humic acid flocs is rough and irregular and has fractal characteristics,the fractal dimension of flocs is introduced in this study,and the fractal plane is simulated by using the modified two variable WM function.On the basis of the smooth sphere surface,the coordinate transformation is carried out,and the overlapping differential plane is simulated by MATLAB.On this basis,the interface between the rough flocs surface and the PVDF membrane surfaceis calculated from the perspective of energy,the influence of floc morphology including particle size and fractal dimension on membrane fouling was studied.The experimental results show that when the floc size is large and the fractal dimension is relatively low,the total interaction energy between the floc and the membrane surface is the highest,that is,the trend of membrane pollution is reduced,and membrane pollution is not easy to occur.