Abstract
The iron-oxidizing bacterium, Thiobacillus ferrooxidans, is not halotolerant and cannot oxidize ferrous ions (Fe2+) to ferric ions (Fe3+) in electroplating wastewater containing high concentrations of chlorine ions. T. ferrooxidans cannot be used for the treatment of such electroplating wastewater. The acclimation of iron-oxidizing halotolerant bacteria has been studied to treat electroplating wastewater containing ferrous ions and a high concentration of chlorine ions. Iron-oxidizing bacteria that are halotolerant and able to oxidize Fe2+ to Fe3+ were obtained from the activated sludge of a steel works coke-oven wastewater treatment plant. A long-term experiment using artificial wastewater containing 20,000 mg · l-1 chlorine ions showed the stable performance of the Fe2+ oxidation ability by iron-oxidizing bacteria acclimated to seawater. It seems that the acclimated iron-oxidizing bacteria can be used for the treatment of electroplating wastewater. An analysis of genomic DNA extracted from the acclimated sludge of the reactor showed the existence of an analog of the iron-oxidizing bacterium, Thiobacillus prosperus.
