The feed water contained 10 mg/L ferrous ions, with/without 3 mg/L manganese ions. Before membrane filtration, a NaOCl solution with 20 mg/L as Cl was injected into the feed solution to oxidize the ions. The injected NaOCl was mixed with the feed water at different velocity gradients (G) (i.e., G = 200 s−1 and 600 s−1) for 5 min.