The Characteristics Of Membrane Fouling For Coagulation Microfiltration Process To Remove The Natural Organic Matter (NOM)

The application of membrane in water treatment makes the removal of the suspended colloid and bacteria efficiently. Microfiltration membrane is widely used because of its lower operation pressure and higher flux. The most important problem in the practical of water treatment with microfiltration is membrane fouling. Coagulation appears to yield some beneficial effects when it is combined with membrane filtration because of its low cost and simple operation, which can improve water quality, reduce membrane fouling and decrease cost.This study confirmed some particular dosages in the coagulation jar test. And the water coagulated with these coagulant dosages was filtered in a submerged membrane module. The study focused on the effects of a pre-coagulation microfiltration with different dosages of different coagulants on the reducing of membrane fouling, and then analysis with membrane filtration models about different coagulation mechanism of two monomer ferric coagulant dosages and optimum aluminous dosage was done. The main conclusions are as follows:1 ) Water pre-coagulated by ferric/aluminous coagulants before microfiltration membranes filtering can reduce the decline of flux. With the same dosage, polymer ferric coagulant has a better effect on the reduction of membrane fouling than monomer ferric coagulant and aluminous coagulants were just the opposite. The humic removal efficiency of the permeate water increased with the coagulation dosages of 0,0.1,0.2,0.3,0.6mmol/L, whereas the flux increased first until the optimum point, and then decreased. So the best dosage to get the best humic acid removal was not the best dosage for membrane fouling reduction.3) Aluminous coagulants whether the polymer or the monomer were more effective to reduce the flux decline than the ferric coagulants did. And in the small dosages,the polymer coagulants were more effective than the monomer.4) Water filtered without pre-coagulation can be simulated by the standard pore blocking model. And comparing the simulation results of three models of microfiltration membrane filtration process with coagulation as pre-treatment, it showed that the cake—standard blocking model was most suitable one to predict the decline of the flux. The filtration under the condition of sweep pre-coagulation because of low dosage had a better flux than the one under the condition of charge re-stabilization pre-coagulation because of the high dosage.