Utilization of Cathodic Hydrogen as Electron Donor for Chloroform Cometabolism by a Mixed, Methanogenic Culture

Currently there is considerable interest in using elemental iron (Fe0) for treatment of highly chlorinated organic compounds. Early studies found little microbiological contribution to degradation in laboratory and field tests. Most work since then has focused on abiotic processes. In studies conducted with a mixed, methanogenic culture, however, pseudo-first-order rate coefficients for chloroform degradation were at least 3.6 times greater in serum bottle incubations containing 40 mesh iron filings and live cells as compared to incubations containing Fe0 and killed cells, Fe0 and cell-free mineral medium, or Fe0-free incubations with live cells. CF cometabolism and methanogenesis was apparently supported using cathodic hydrogen produced by anaerobic corrosion of the added Fe0. The use of selective microbial inhibitors showed that H2-consuming methanogens and not homoacetogens were responsible for CF degradation. The sustainability of the process was established in a 60-day column study using steel wool as support for microbial growth. The observation that cathodically produced H2 can support reductive dechlorination by anaerobic bacteria may have significant practical implications.