Experiment and Mechanism Analysis of Pretreatment Process Control Membrane Fouling

Abstract:

The roles of three kinds of pretreatment technology (ozone+online coagulation+ultrafiltration (process 1), ozone+ultrafiltration (process 2), and ozone+prechlorination+ultrafiltration (process 3)) in delaying the ultrafiltration membrane fouling were explored in this paper. The results show that the critical flux of three processes are 86.5, 59.8 and 68.1 L?(m2?h)-1, respectively. Of the three processes, the critical flux of process 1 is the largest, with the longest stable operation time (about 190 h), and can control membrane fouling to a certain extent. This can be explained by the adsorption that organic pollutants are adsorbed by colloidal particles, which can reduce the contact and interaction between organic pollutants and membrane interface by the membrane sieving intercept. Process 3 is followed with the best performance in controlling and alleviating membrane fouling due to the change of organic molecular characteristics under the effect of NaClO: 1) membrane’s flux declined and hydrophilichydrophobic property changed; 2) the increasing electronegativity of cake layer promotes the waterbackwash to remove the remaining matters and dissolves the organic matter, which results in a good transmembrane pressure recovery. By scanning with the electron microscopy (SEM), it is found that the soft filter cake layer is adhered on the surface of the ultrafiltration membrane and membrane hole is blocked by pollutants. The infrared spectroscopy study finds that the membrane surface properties are changed as some groups on membrane are oxidized by oxidation pretreatment and chemical cleaning.