Biological oxidation of ferrous iron is useful for the treatment of acid drainage containing high concentration of ferrous iron, since a hydroxide of ferric iron easily precipitates at pH 4 by adding CaCO₃.
The kinetics of ferrous iron oxidation was studied in batch experiments. The effects of dissolved oxygen and initial ferrous iron concentration on the rate of ferrous iron oxidation by Thiobacillus ferrooxiadns were expressed by Monod-type equations. The best support medium for the attachment of iron oxidizing bacteria was macroporous ion exchange resin IRA938. Then, the possibility of continuous oxidation of ferrous iron was tested with a fluidized bed reactor. By use of this resin as a support medium, the continuous experiments in the fluidized bed reactor with a retention time of 20 minutes showed that more than 90 % oxidation of ferrous iron had been maintained in the duration of two months.
Based on these experimental results, a mathematical model which describes the behaviour of ferrous iron in the fluidized bed reactor was developed. This model well expressed the effluent ferrous iron concentration at a steady state.

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Groundwater contamination with volatile chlorinated hydrocarbons (VCHs) was found in a metalware manufacturing district located in a central part of the Niigata Plain, Niigata, Japan. VCHs detected were trichloroethylene (TCE), tetrachloroethylene (PCE), 1, 1, 1-trichloroethane (MCF), cis-1, 2-dichloroethylene (cis-DCE) and 1, 1-dichloroethane (1, 1-DCA). VCHs concentrations in groundwater were ranged from <0.001 to 7.1 mg·l^-1 for TCE, <0.0010.036 mg·l^-1 for PCE, <0.0011.2 mg·l^-1 for MCF. Concentrations of cis-DCE and 1, 1-DCA were <0.015.1 mg·l^-1 and <0.010.61 mg·l^-1, respectively ; cis-DCE and 1, 1-DCA might be produced biodegradedly in soil from TCE and MCF, respectively.
Groundwater in alluvial aquifers was mainly of the carbonate hardness type, while groundwater quality in diluvial aquifers depended on the location. Although the diluvial aquifers were not polluted by VCHs, some of the alluvial aquifers contaminated by VCHs.
Concentrations of TCE and cis-DCE were determined for a year in groundwater from a well of 10 m depth at a metalware factory using VCHs. The VCHs concentrations in groundwater were varied with the amount of groundwater pumped up from both the investigated well itself and well set around it as well as with the groundwater level.

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[in Japanese]

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[in Japanese]

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