Jan. 1, 2014 - Dec. 31, 2015Award Number
John Buchanan, Ph.D.
University of Tennessee
Water used for frost protection and irrigation is one of the most likely points of pathogen contamination during fruit and vegetable production. Previous studies have focused on chemical rather than microbiological water-quality parameters. Consequently, a knowledge gap exists regarding surface water sanitary quality and the risks associated with the timing and method of application. In response to FDA’s proposed standards for surface water quality, we propose to evaluate the adequacy of three in-line methods for disinfecting frost protection and irrigation water. An ultraviolet light module, a chlorine dioxide injection system, and a peroxyacetic acid injection system will be evaluated based on the reduction of indicator microorganisms (E. coli and fecal coliforms) and the presence or absence of pathogens (Shiga Toxigenic E. coli [STEC]) in a double- cropping system with strawberry and cantaloupe. These disinfection techniques will be compared to non-disinfected, pond water with cattle access and populations of all organisms of interest. In addition to evaluating populations of microorganisms pre- and post-treatment, we will also sample plant tissue during flower, early fruit, peak fruit, and late harvest to determine transfer rates of foodborne pathogens. Yield and quality characteristics for each crop among disinfection treatments will also be compared.
There is currently a need to evaluate disinfection systems in real-world scenarios that can be readily implemented to mitigate food safety risks with irrigation water. This project will conduct in-field evaluations of three irrigation-water disinfection methods: ultraviolet light (UV), chlorine dioxide (ClO2) and peroxyacetic acid (PAA). While these systems have been utilized in wastewater treatment, food processing, and in agriculture water systems a lack of knowledge exists regarding how they will perform when utilized for in-line treatment of surface water to mitigate foodborne pathogens, in this case Shiga Toxigenic E. coli (STEC). The project team will establish a series of plasticulture and bare-ground research plots containing double-cropped strawberries and cantaloupes, and irrigate these crops from a pond that also serves to water beef cattle, with populations of fecal coliforms, generic Escherichia coli as well as Shiga Toxigenic E. coli (STEC). This same pond water and experimental configuration will also be used to frost protect the strawberries. During irrigation and frost protection, water will pass through a sand filter and then be divided across four water treatment systems (UV light, ClO2, PAA and a non-disinfected control). An in-line UV light module will be mounted into the UV irrigation system. Likewise, in-line injectors will be used for the ClO2 and PAA systems. Each research plot will have the ability to be drip and overhead irrigated.
During frost protection and irrigation, water samples will be taken from the pond and from the irrigation discharge to evaluate disinfection effectiveness. The team’s research will determine the inactivation of STEC, E. coli, and fecal coliforms in treatment systems as compared to the control. In addition, the transfer and survival of these organisms onto strawberries and cantaloupe in a drip and overhead irrigation setup will be determined. Plant tissue samples will be taken during flower, early fruit, peak fruit, and late harvest. Strawberries will serve as the model crop for frost protection; cantaloupes will provide a late season model crop and will demonstrate differences in potential pathogen contamination between drip and overhead irrigation, as well as bare-ground and plasticulture systems. Yield and quality for each crop among disinfection treatments will also be compared to evaluate treatment impacts on total and marketable yield. The project deliverables will include inactivation rates of STEC, E. coli, and fecal coliforms for each irrigation water disinfection system as well as information regarding transfer of these organisms to produce and impact on produce yield and quality when utilizing indirect and direct irrigation methods and plasticulture and bare-ground cultivation techniques.