Continuous Performance of Permeable Reactive Columns Combining ZVI/FeS2 with Microorganisms for Removal of Nitrate and Ofloxacin from Water
Groundwater contamination by nitrate and antibiotics has become a global concern. This study evaluated the continuous performance of permeable reactive barrier (PRB) columns packed with zero-valent iron (ZVI) and pyrite (FeS2) combined with denitrifying microorganisms (ZFM) for simultaneous removal of nitrate and ofloxacin (OFL). Control columns included soil (S), microorganisms (M), and ZVI/FeS2 (ZF). Over 30 days of continuous operation, the ZFM column achieved average removal efficiencies of 88% for nitrate and 78% for OFL, significantly higher than controls. The ZFM system maintained higher active iron concentration (0.68 mg·L−1) compared to ZF (0.48 mg·L−1), mitigated pH increase, and sustained lower oxidation-reduction potential (ORP), favoring stable performance. XRD and XPS analyses revealed that microbial involvement promoted FeS formation (2θ=30.1°) and reduced ZVI passivation, extending material lifespan. High-throughput sequencing showed that while overall microbial diversity remained stable, key functional populations including norank_f_Fermentibacteraceae, norank_f_Anaerolineaceae, Longilinea, and Anaerolinea increased in abundance by 2.93%, 0.55%, 1.53%, and 0.62%, respectively, enhancing nitrate and OFL removal. These findings demonstrate that integrating microorganisms with ZVI/FeS2 in PRB systems offers a promising approach for remediating combined nitrate and antibiotic contamination in groundwater.