The effect of microbubbles on membrane fouling caused by different foulants

Previously, we presented a water treatment technology using microbubbles (MBs) in membrane filtration in order to reduce membrane fouling and to improve the filtration flux. In this study, we investigated the effect of foulants in this system. Water samples from five rivers and three model foulant solutions were used, and water quality indicators such as dissolved organic carbon (DOC), ultraviolet absorbance (E260), and specific UV absorbance (SUVA) of these solutions were analyzed. Correlations between the flux enhancement by MB and DOC, E260, and SUVA in the five river water samples indicated that MBs were effective for river water samples with fewer foulants, and that an increase in the amount of highly aromatic hydrophobic substances in the river reduced the MB effect. In the experiments using humic acid, guar gum, and bovine serum albumin (BSA) as model foulants, it was found that MBs enhanced the reduction of fouling from the initial stage in the cases of humic acid and guar gum, while in the case of BSA, the MB effect was not clear in the initial stage and then became more pronounced. The relation of the flux enhancement by MB and DOC for the humic acid solution was roughly in agreement with the relations obtained from river water samples.