Abstract: Biotic lowpH Fe(II) oxidation can be an effective component of the remediation system for acidic coal mine drainage. However, application of such system is limited because of uncertainties associated with Fe behavior and fate. By monitoring biogeochemical process at an acidic coal mine drainage site, we obtained enriched indigenous sediment microbes to explore the behavior and fate of Fe and other metals under microbialmediated condition in a chemostatic bioreactor. As the results illustrate, transformation of Fe species was the major biogeochemical process both at field site and in a bioreactor. At pH<2.7, redox reactions were more prone to produce soluble Fe(III); whereas, at 2.7<pH<4.2, insoluble Fe(III) species were preferentially produced. Under acidic conditions, no significant transformation involving other metal ions was detected in active bioreactors. The sediments generated in the reactor were mainly composed of schwertmannite and goethite, and mineralogical transformation moved towards to NaJarosite with increasing addition of acid or base. Our study helps to guide application of similar microbial processes to remediate contaminated waters and provides scientific significance for the sludge recovery and reuse effort.

Key words: acid mine drainage, Fe(II) oxidation, bioreactor, schwertmannite