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ENHANCED DECHLORINATION OF SOLVENTS IN THE PRESENCE OF PURE CULTURES OF METHANOGENIC BACTERIA AND ELEMENTAL IRON

It has also been demonstrated that elemental iron (Fe0) can facilitate the abiotic reductive dechlorination of chlorinated aliphatics. Furthermore, studies have shown that methanogenic bacteria are capable of growth on elemental metals, including iron, which serves as the sole electron donor for growth. This occurs via the production of hydrogen gas (H2) by the reduction of water-derived protons, using electrons liberated during the oxidation of Fe0 to Fe2+.

Hydrogen then serves as the electron donor for the methanogens. A combined system of elemental iron plus methanogens could be expected to provide a low-maintenance treatment system which would exploit the dechlorinating abilities of both the biological and abiotic agents present. Research in our laboratory has demonstrated that an iron (Fe0)-methanogen combination increases the rate and extent of CT and CF removal.

Experiments with pure cultures of Methanosarcina barkeri, Methanosarsina thermophila, and Methanosaeta concilii have elucidated the mode of this enhancement. Hydrogen can serve as an electron donor for growth, but even when the organism can't use H2 for growth, enhanced dechlorination occurs. Direct contact between the Fe0and organism appears necessary for enhanced dechlorination. An extracellular factor (protein?) produced by Methanosarcina themophila is implicated in some of the enhanced dechlorination.

Key words: dechlorination, methanogens, elemental iron