Recovery of iron reactivity for removal of Cr(VI) using iron-reducing consortium

Iron particles, oxidized by Cr(VI), were not effective for additional Cr(VI) removal, but the removal rates of Cr(VI) dramatica Ily increased when iron-reducing consortium were added to the oxidized iron. The elevated removal rate was even greater than that f or iron particles. Addition of iron-reducing consortium to the oxidized iron generated ferrous ions, indicating recovery in the reactivity of iron particles as the ferrous ions could reduce additional hexavalent chromium to trivalent chromium, which is less toxic and immobile compared to hexavalent chromium. The iron-reducing consortium itself could also remove hexavalent chromium via reduction reaction as modest amount of Bacillus sp., which are known hexavalent chromium-reducing bacteria, were found. Combined effects of bacillus sp. and ferrous ions accelerated the removal rate of Cr(VI). Waste leaves were used as alternative substrate in this research and they supported the activity of iron-reducing consortium in the presence of the oxidized iron. Al though the activity of iron-reducing consortium supported by waste leaves was lower (approximately one order of magnitude) than that supported by nutrients, the removal rate of Cr(VI) was sufficiently high indicating waste leaves could be used as a nutrient source for iron-reducing consortium.