The fouling resistances (Rf) of Fe and Fe–Mn oxides formed at low and high mixing intensities are shown in Fig. 8. The Rf increased with progressing filtration cycles as a result of increased pore plugging within the membrane after filtration, even though backwashing had been carried out. With each additional filtration cycle, the Rf for Fe/Mn-oxide layer became much more severe than that for Fe-oxide layer. Other work has suggested that the formation of Mn oxides within membrane pores causes major irreversible fouling during membrane filtration [for recycling Fe–Mn oxides] [6]. As shown in the SEM images in Fig. 9, after four membrane filtration cycles pore plugging or narrowing caused by Fe–Mn oxides is more severe than that by only Fe oxides. Moreover, the ratio of Fe and Mn oxides within the membrane determined by EDS is approximately 10:3, suggesting that Rf would increase when Mn oxides were completely formed and plugged within membrane. However, the Rf of membrane filtration with Fe or Fe–Mn oxides is insensitive to mixing intensity during/with chlorination in each filtration cycle. Although the oxides formed at high mixing intensity are smaller than those formed at low mixing intensity, most of Fe and Fe–Mn oxides particles formed at low and high mixing intensities during prechlorination are larger than the size of MF membrane pores. As a result, only a few small oxide particles would penetrate the pore of membrane during filtration, resulting in limited difference in Rf for the membrane filtration by low and high mixing-intensity. These results show that the magnitude of irreversible fouling during microfiltration for Fe/Mn-oxide suspensions increases more rapidly than that for Fe-oxide suspensions with increasing filtration cycle regardless of mixing intensity during chlorination.