Effect of pre-coagulation using different aluminium species on crystallization of cake layer and membrane fouling

Abstract

Pre-coagulation could mitigate the membrane fouling, and thus we used different Al coagulants as a pre-treatment for ultrafiltration to explore their effects on the morphology of the membrane cake layer and fouling. Parallel bench-scale tests, using three different species of Al (AlCl3, PACl15, and PACl25), with and without humic acid, were operated continuously for a long period to investigate the effects of floc aging (~13 days). Specifically, the presence of humic acid affects the cake layer by influencing the rate and extent of floc crystallization, as greater crystallization leads to greater fouling (bio-fouling was excluded in this study). The fouling rate (indicated by the trans-membrane pressure at constant flux) varied with Al species and was found to increase as follows: PACl15 < PACl25