The effect of pre-ozonation on UF membrane fouling by the size fractioned sewage effluent

The effect of pre-ozonation on fouling control is related with ozone-induced particle aggregation/destabilization or the structural changes of organic materials. To clarify the mechanism of pre-ozonation on fouling and further optimize the use of pre-ozonation in real full-scale UF membrane operation system, the actual sewage effluent (SE) was filtrated to remove specific foulants with sand filter, 1.2 mu m and 0.45 mu m filter. Then, UF membrane fouling caused by the remaining foulants after pre-ozonation was further investigated. As for the SE pre-filtered by sand filter, the results revealed that pre-ozonation only slightly alleviated the fouling of UF membrane. After pre-oxidation with the ozone concentration lower than 1.53 mgO(3)/mg TOC, membrane flux dramatically decreased in the initial filtration stage, accompanying with an obvious increase of the irreversible fouling. With the increase of ozone concentration, the membrane flux was improved and the irreversible fouling was apparently decreased. Besides, the retention of total organic carbon by UF was strengthened with the increase of ozone concentration. As for the SE pre-filtered by the 1.2 mu m or 0.45 mu m filter, the effect of pre-ozonation on fouling control was obvious. Although a slight increase of the irreversible fouling was also observed under lower ozone concentration, the total fouling and the reversible fouling presented a continuously decrease with the increase of ozone concentration. SEM results revealed that the fouling alleviation by pre-ozonation was related to the aggregation of foulants. Pre-filtration before the hybrid process of pre-ozonation and UF is helpful for fouling alleviation and irreversible fouling control in processing the actual SE.