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金沢大学理工研究域機械工学系, Wastewater from electroplating plants contains several metallic ions such as iron, nickel and zinc. In general, neutralization followed by sedimentation has been used for the treatment of electroplating wastewater. However, this process results in the production of large amounts of heavy metal sludge. The objective of this research is to achieve selective metal separation, metal recovery and reduction in sludge volume. We have examined the feasibility of a biological process using iron-oxidizing bacteria in the treatment of electroplating wastewater from steel works. It was proved that iron-oxidizing bacteria acclimated from activated sludge have the ability to oxidize ferrous ion (Fe2+) to ferric ion (Fe3+) in electroplating wastewater. A bioslurry reactor, which promotes both Fe2+ oxidation and Fe(OH)3 generation in the pH range from 3.0 to 4.0, showed an almost complete Fe2+ oxidization after 2 hours of hydraulic retention time. The produced Fe(OH)3 was recovered by sedimentation in the same pH range with almost no trace of nickel or zinc. Nickel and zinc hydroxides were easily recovered by sedimentation at pH 9.0.