Re‐activation of aged‐ZVI by iron‐reducing bacterium Shewanella putrefaciens for enhanced reductive dechlorination of trichloroethylene

BACKGROUND Zero valent iron (ZVI) has been extensively applied in the remediation of groundwater and wastewater contamination. This study aimed to investigate the depassivation effect of iron‐reducing bacterium Shewanella putrefaciens on aged ZVI towards the dechlorination of trichloroethylene in aqueous solutions. RESULTS Both mmZVI and nZVI showed high reactivity towards TCE until they were passivated. Lepidocrocite was identified as the main corrosion product of nZVI, while green rust was identified as the main corrosion product of mmZVI. More importantly, the combination of iron‐reducing bacteria with aged mmZVI generated greater enhancement of TCE removal than the combination with nZVI. Better bacterium–mineral association conditions determined by SEM and the release of ZVI in the core of aged mmZVI counted for the depassivation effect of iron‐reducing bacterium on aged mmZVI. Moreover, dialysis bag experiments indicated that Shewanella putrefaciens could employ both indirect and direct mechanisms of electron transfer to iron oxide, and the addition of metal chelating agent promoted the iron reducing process greatly. Synergistic mechanisms between dissimilatory iron reducing bacteria (DIRB) and aged ZVI was proposed. CONCLUSION This study demonstrated that the contaminants reduction ability of aged ZVI could be recovered to some extent by DIRB and DIRB influenced the long‐term performance of ZVI. © 2017 Society of Chemical Industry