Escherichia coli Reduction in Water by Zero-Valent Iron-Sand Filtration Is Based on Water Quality Parameters

Improving the microbial quality of agricultural water through filtration can benefit small farms globally. The incorporation of zero-valent iron (ZVI) into sand filters (ZVI-sand) has been effective in reducing E. coli, Listeria spp., and viruses from agricultural water. This study evaluated ZVI-sand filtration in reducing E. coli levels based on influent water type and the percentage of ZVI in sand filters. A ZVI-sand filter (50% ZVI/50% sand) significantly (p < 0.001) reduced E. coli levels in deionized water by more than 1.5 log CFU/mL compared to pond water over six separate trials, indicating that water type impacts E. coli removal. Overall reductions in E. coli in deionized water and pond water were 98.8 +/- 1.7% and 63 +/- 24.0% (mean +/- standard deviation), respectively. Filters constructed from 50% ZVI/50% sand showed slightly more reduction in E. coli in pond water than filters made from a composition of 35% ZVI/65% sand; however, the difference was not statistically significant (p = 0.48). Principal component analysis identified that the turbidity and conductivity of influent water affected E. coli reductions in filtered water in this study. ZVI-sand filtration reduces Escherichia coli levels more effectively in waters that contain low turbidity values.