Influence of microbial floatation on membrane fouling due to particles and organic matters in submerged microfiltration

This study investigated the effect of microbubble floatation on the fouling of microfiltration membranes. Synthetic feed solutions containing either kaolin or alginic acid were used for the membrane filtration tests. A dissolve air flotation system using a pump-type microbubble generator was adopted as a pretreatment for microfiltration system. A multi-array submerged membrane filtration system was used to monitor the changes in transmembrane pressure with time under various operating conditions. Turbidity removal efficiency, particle counts, and fouling rate for the microfiltration membrane were measured after the microfiltration floatation. The effect of coagulant dose on the treated water quality and membrane performance was also investigated. Results showed that microbubble floatation without coagulant was effective to reduce membrane fouling by kaolin but it was not very effective to control fouling by alginate. With the aid of coagulant, microbubble flotation could control fouling by alginate. This is attributed to the removal mechanisms of foulants by microbubble floatation: suspended particles can be separated by the microbubbles without coagulant but dissolved organics can be only removed by the combined effect of coagulation and floatation.