Study on the Effect of Calcium Ion Concentration on Coagulation/Sedimentation-nanofiltration Membrane Fouling Mechanism
Membrane technology has been widely used in municipal wastewater plants for the secondary effluent reuse,with the advantages of high efficiency,economic space occupation and clean process;however,the problem is membrane fouling,and it has become a major difficult point in promoting the application of membrane separation technology,so to overcome the difficulties is the key point at present.In this study,to explore the mechanism of Ca2+concentration on membrane fouling in coagulation/sedimentation-NF process,the simulated secondary effluent of municipal wastewater plant was used as the raw water,and the ion-concentration was changed by adding CaCl2,and the membrane fouling process under different concentra-tion conditions was analyzed by the membrane fouling model and membrane fouling index,and the interface mechanism in the membrane fouling process was quantitatively analyzed at the microscopic level by combining xDLVO theory.Consequently,the results showed that as the Ca2+concentration was 120 mg/L,the membrane flux was at its lowest point,and the irreversible and irreversible membrane resistance were at their highest values,corresponding to the peak of the membrane fouling index.Accord-ingly,the compactness of the cake layer on the membrane surface was also the highest,which indicated the severity of mem-brane fouling;at the same time,in the condition of ion-concentration,the energy barrier between the contaminants in the feed-water and the NF membrane,as well as the energy barrier between the contaminants in the feed-water and the existing contami-nants on the membrane surface,were all at their lowest values.In this way,the lowering of the energy barrier further boosted the formation of membrane fouling and made the fouling process more easily occur in this Ca2+concentration condition.
万方数据
维普
