Because of the pore structure change and blocking of the ceramic membrane pores, deactivation of ceramic membranes occurred after repeated use. A pore blocking mechanism has been observed from the SEM study that in the first stage of deactivation, the membrane pore sizes became smaller due to the accumulation of the unremoved chemicals, and the pore neck parts were closed and/or blocked. Finally, the pore structures changed to the broken piece of long and thin elliptical shapes. Two regeneration methods were explored and tested in attempts to recover useful activity for the deactivated membranes. Relatively fresh membranes, including intermediately used membranes, can recover fluxes as much as 70 percent of fresh membrane flux by chemical treatments such as acetone acid treatment, while the severely deactivated membranes were partially regenerated by an oxidation method followed by the acetone and acid treatment.