ARS | Publication request: Effect of Zero-Valent Iron on Removal of Escherichia coli O157:H7 from Agricultural Waters

Submitted to: International Association for Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: March 17, 2008
Publication Date: August 5, 2008
Citation: Derevianko, A.M., Handlin, J., Yoskowitz, A., Jin, Y., Chiu, P., Sharma, M., Kniel, K. 2008. Effect of Zero-Valent Iron on Removal of Escherichia coli O157:H7 from Agricultural Waters. International Association for Food Protection.Abstract Book, p.25

Technical Abstract: A novel water filtration system using zero-valent iron (ZVI) is being investigated as a simple and inexpensive approach to reducing E. coli O157:H7 in water for both pre- and post-harvest processes. Purpose: This study was initiated to determine the effectiveness of zero-valent iron in the removal and inactivation of E. coli O157:H7 in a simulated irrigation system. Methods: The 2006 spinach and lettuce outbreak strains of E. coli O157:H7 (106 CFU/ml in 1600 ml artificial groundwater (AGW) of pH 5, 7.5 and 9) were pumped through sand (control) and iron columns with a flow rate of 1 ml/min at 4 deg C. An initial pulse of 10 pore volumes (PV) was pumped through the columns, followed by a flush of sterile AGW (20 PV). Effluent samples were collected at 4.5 and 9 minute intervals for the pulse and flush. One-ml samples from each tube were serially diluted in buffered peptone water and plated onto TSA with 50 ug/ml nalidixic acid in duplicate; bacterial concentrations were determined after 24 hours at 37 deg C. Following the experiments, the columns were dismantled and examined for the presence of E. coli. Results: Break-through curves at all pH values showed reduction of 1–2 logs of E. coli O157:H7 by the inclusion of zero-valent iron compared to sand. During the pulse, removal efficiencies by ZVI were 1.78 ± 0.11, 1.01 ± 0.19, and 1.5 ± 0.23 logs for pH 5, 7.5, and 9. Removal remained constant throughout the pulse. Bacterial inactivation by ZVI was observed to be 2.38 ± 0.67 logs as compared to sand column at identical locations. Significance: The ability of ZVI to remove and inactivate E. coli O157:H7 shows great potential for reducing irrigation water contamination. ZVI is currently being assessed for its effectiveness on wash water for leafy greens and the filtration system is being optimized for enhanced removal.