Effect of fouling reduction by ozone backwashing in a microfiltration system with advanced new membrane material

The effect of ozone back washing for membrane fouling reduction was experimentally investigated in a submerged metal membrane microfiltration system. A cleaning by intermittent ozone gas backwashing was effective in recovering the permeation flux. Intermittent ozone backwashing was highly effective than the air or permeates backwashing for flux recovery. Regarding the operational parameters, the increase of ozone gas flow rate was more effective than the increase of injection time under the conditions of same ozone dose. However, the backwashing cycle was longer, the effect of flux recovery by ozone backwashing decreased. Therefore, it is favorable to operate membrane cleaning before the foulant was consolidated on membrane surface.

Backwashing effect by ozonation for permeation flux recovery was experimentally investigated in a microfiltration membrane process. The results obtained from experiments are summarized as follows: Particle size and size distribution play an important role in membrane fouling and small particles cause much severer fouling than the larger particles. Fresh sewage with sonication caused greater fouling than that without sonication. Intermittent ozone backwashing can be used to clean membrane effectively for fouling caused by cake formation and internal pore blocking. The permeation flux with intermittent ozone backwashing showed significantly higher value than that in air backwashing during continuous filtration. Under the same ozone injection, gas flow rate increasing was more effective than the increase of injection time for the recovery of permeation flux. In continuous operation, flux recovery ratio by air backwashing was about 80%, while showed over 90% of recovery ratio with ozone gas. As the filtration/backwashing cycle was longer, the effect of flux recovery by ozone backwashing decreased. Therefore, it is favorable to operate membrane cleaning before the foulant is consolidated on the membrane surface.