Enhanced Microbial Chromate Reduction Using Hydrogen and Methane as Joint Electron Donors.

•Chromate bio-reduction is enhanced by using H2 and CH4 as joint electron donors.•A higher chromate removal rate is achieved with a volume ratio of H2 to CH4 at 1:1.•Chromate reducers and bacteria metabolizing H2 and CH4 are detected.•Genes for Cr(VI) reduction (chrA), H2 and CH4 oxidation (hupL, mcrA) are harbored.•More abundant extracellular cytochrome c and intracellular NADH are detected.