Complete Perchlorate Reduction Using Methane as the Sole Electron Donor and Carbon Source
2015
Luo, Yi-Hao | Chen, Ran | Wen, Li-Lian | Meng, Fan | Zhang, Yin | Lai, Chun-Yu | Rittmann, Bruce E. | Zhao, He-Ping | Zheng, Ping
Using a CH₄-based membrane biofilm reactor (MBfR), we studied perchlorate (ClO₄–) reduction by a biofilm performing anaerobic methane oxidation coupled to denitrification (ANMO-D). We focused on the effects of nitrate (NO₃–) and nitrite (NO₂–) surface loadings on ClO₄– reduction and on the biofilm community’s mechanism for ClO₄– reduction. The ANMO-D biofilm reduced up to 5 mg/L of ClO₄– to a nondetectable level using CH₄ as the only electron donor and carbon source when CH₄ delivery was not limiting; NO₃– was completely reduced as well when its surface loading was ≤0.32 g N/m²-d. When CH₄ delivery was limiting, NO₃– inhibited ClO₄– reduction by competing for the scarce electron donor. NO₂– inhibited ClO₄– reduction when its surface loading was ≥0.10 g N/m²-d, probably because of cellular toxicity. Although Archaea were present through all stages, Bacteria dominated the ClO₄–-reducing ANMO-D biofilm, and gene copies of the particulate methane mono-oxygenase (pMMO) correlated to the increase of respiratory gene copies. These pieces of evidence support that ClO₄– reduction by the MBfR biofilm involved chlorite (ClO₂–) dismutation to generate the O₂ needed as a cosubstrate for the mono-oxygenation of CH₄.
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