The reaction of nitrate-dependent Fe(II) oxidation depended on abiotic and microbial mechanism simultaneously. Even though the thermodynamics conditions were favorable, the kinetics of abiotic aqueous Fe2+oxidation under circumneutral pH condition was still relatively slow without catalytic ions or reaction interfaces (Buresh and Moraghan, 1976; Picardal,2012). Thus, the nitrate-dependent Fe(II) oxidation in CWs mainly depended on microorganisms. However, some microorganisms could not reduce NO3−by oxidizing Fe(II) if organic carbon sourceswere unavailable