The efficacy of zero valent iron-sand filtration on the reduction of Escherichia coli and Listeria monocytogenes in surface water for use in irrigation

The use of surface and recycled water sources for irrigation can reduce demand on critical groundwater resources. Treatment or mitigation may be necessary for the use of these alternative water sources in order to reduce risk associated with microbial pathogens present in the water. In this study, the efficacy of a zero-valent iron (ZVI) sand filter was assessed for the reduction of Listeria monocytogenes and Escherichia coli in surface water. Water recovered from an agricultural pond was inoculated with E. coli TVS353 and an environmental L. monocytogenes isolate at 7 Log10 CFU/mL and horizontally filtered over a six-month period through a PVC pipe filter, filled with 35%:65% (volume:volume) ZVI:sand or sand alone. Filtered water was used to irrigate lettuce and bacterial persistence on lettuce leaves was determined for 7 days post-irrigation. Both ZVI:sand-filtered water and sand-filtered water contained significantly (p