Biogenic sulfidation-mediated de-passivation and reactivation of zero-valent iron: Synergism of sulfate-reducing bacteria and Shewanella towards trichloroethylene degradation

SRB-mediated biogenic sulfidated ZVI had a higher sulfidation degree. • Shewanella -mediated biogenic sulfidated ZVI promoted iron redox cycling. • SRB- Shewanella biogenic sulfidated ZVI degraded 98.8% TCE in low-nutrient conditions. • The synergistic system enhanced carbon utilization and key enzyme activities. Zero-valent iron (ZVI) for groundwater remediation is severely limited by surface passivation, while biogenic sulfidation is a promising eco-friendly modification. However, research on biogenic sulfidated ZVI (BS-ZVI) mainly focuses on sulfate-reducing bacteria (SRB), neglecting multi-strain synergism. Herein, we constructed BS-ZVI systems with SRB (denoted as BS-ZVI SRB ) and Shewanella oneidensis MR-1 (denoted as BS-ZVI MR-1 ) to compare their trichloroethylene (TCE) degradation performance, and develop a “SRB- Shewanella ” synergistic system. 95.7% and 96.2% of TCE were degraded by BS-ZVI SRB (0.43 d −1 ) and BS-ZVI MR-1 (0.45 d −1 ), respectively. BS-ZVI SRB had a higher sulfidation degree and the polysulfides inhibited the hydrogen evolution reaction (HER). The active dissimilatory iron reduction (DIR) behavior in the BS-ZVI MR-1 system suppressed the surface passivation. Notably, the “SRB- Shewanella ” maintained 95.2%-98.8% TCE degradation efficiency under oligotrophic conditions (chemical oxygen demand (COD) = 45.7 mg/L-47.3 mg/L), with improved carbon-source utilization and enzymatic activity. Overall, this study offers fundamental theoretical insights and parametric references for the development of in-situ BS-ZVI remediation technology. Download: Download high-res image (537KB) Download: Download full-size image