Aims: Zero-valent iron (ZVI) filters may provide an efficient method to mitigate the contamination of produce crops through irrigation water. Methods: A field-scale system was utilized to evaluate the effectiveness of a biosand filter (S), a biosand filter with ZVI incorporated (ZVI) and a control (C, no treatment) in decontaminating irrigation water. An inoculum of c. 8.5 log CFU 100 ml(-1) of Escherichia coli O157:H12 was introduced to all three column treatments in 20-l doses. Filtered waters were subsequently overhead irrigated to 'Tyee' spinach plants. Water, spinach plant and soil samples were obtained on days 0, 1, 4, 6, 8, 10, 13 and 15 and analysed for E. coli O157:H12 populations. Results: ZVI filters inactivated c. 6 log CFU 100 ml(-1) E. coli O157:H12 during filtration on day 0, significantly (P < 0 05) more than S filter (0.49 CFU 100 ml(-1)) when compared to control on day 0 (8.3 log CFU 100 ml(-1)). On day 0, spinach plants irrigated with ZVI-filtered water had significantly lower E. coli O157 counts (0.13 log CFU g(-1)) than spinach irrigated with either S-filtered (4.37 log CFU g(-1)) or control (5.23 log CFU g(-1)) water. Soils irrigated with ZVI-filtered water contained E. coli O157:H12 populations below the detection limit (2 log CFU g(-1)), while those irrigated with S-filtered water (3.56 log CFU g(-1)) were significantly lower than those irrigated with control (4.64 log CFU g(-1)). Conclusions:ZVI biosand filters were more effective in reducing E. coli O157:H12 populations in irrigation water than sand filters. Significance and Impact of the Study:Zero-valent ion treatment may be a cost-effective mitigation step to help small farmers reduce risk of foodborne E. coli infections associated with contamination of leafy greens.