Outline of the biological treatment using iron and manganese
oxidizing bacteria Groundwater often contains iron, manganese
and arsenic originating from natural geological layer and / or
mineral resources. We have applied biological iron and manganese
removal system utilizing iron and manganese oxidizing bacteria
(IRB hereafter) to arsenic removal. The conventional biological
iron and manganese treatment by IRB colonizes indigenous IRB in
groundwater on filter media by continuous percolation of
groundwater. The IRB oxidizes dissolved ferrous iron and
manganese ions to particulate form, which are subsequently
deposited on the filter media or filtered out by the underlying
filter media. In FY 2005, simultaneous removal of iron and
arsenic was achieved in our pilot-scale test treating
groundwater that contained arsenic, iron and manganese of
geological origin. Removal of manganese, however, was low then.
Biological oxidation of manganese reportedly occurs in the
region shown in the pH-Eh diagram (Fig.1). The low