78 / 2021-06-30 16:54:54

Nitrate-rich groundwater treatment by zero-valent iron and sawdust based mixotrophic denitrification

Nitrate contaminated water; Mixotrophic denitrification; Bacterial community; Zero-valent iron; Sawdust

Zero -valent iron reduction combining biodenitrification process (ICBD) has been proved to be a good method for nitrate removal from nitrate contaminated water. While the synergistic and promotive effects mechanisms of the ICBD were speculated. In this study, sawdust and zero-valent iron (Fe⁰) were used as co-electron donors to clarify the synergistic mechanism responsible for NO₃^- removal in ICBD, for which nitrate nitrogen transformation，products of Fe⁰ reactions and bacterial community structure were evaluated. Batch tests showed that nitrate-nitrogen at a concentration of 50 mg/L was effectively removed with an efficiency of 99.1% for 264 hours from simulated groundwater by the ICBD system. The nitrate removal rate promoted by the synergistic effects accounted for about 20 % of the total removal rate. The primary mechanism of nitrate removal in ICBD is biodenitrification dominated by heterotrophic denitrification and the most dominant genus was Magnetospirillum. The major role of Fe⁰ lied in Fe²⁺ and H₂ production through corrosion by H₂O and CO₂. Moreover，compared with sawdust based denitrification, adding iron can reduce the diversity of microbial community structure.