Evaluation of Multiple Disinfection Methods to Mitigate Contaminated Irrigation Water

Outbreak of foodborne pathogens associated with fresh produce is a concern to produce growers. Irrigation water is one of the pathways of produce contamination. The U.S. Food and Drug Administration (FDA) proposed a set of guidelines for irrigation water that includes a maximum generic E.coli count lower than 126MPN/100mL. Irrigation is typically a continuous-flow process: water is withdrawn from a source and applied to a crop. In order to disinfect irrigation water, a process must be developed to provide treatment while the water is in the hydraulic network. However, studies related to the continuous flow irrigation water disinfection (CFIWD) system are lacking and this study focused on testing different disinfection treatments in CFIWD System. Water samples containing both generic E.coli and Shiga-toxin producing E.coli (STEC) were used to study different disinfection methods. Physical and chemical disinfection methods, including ultraviolet light treatment, peroxyacetic acid (PAA), chlorine dioxide (ClO₂) and UV/PAA combined treatment, were used in this investigation to analyze their disinfection efficiency in highly-contaminated water. Bacteria were enumerated before and after treatment. In general, all the treatments were able to inactivate generic E.coli and STEC. Turbidity, total nitrogen, total carbon and pH measurements were taken with all samples. Turbidity was the most significant parameter that negatively limited the efficacy of the UV treatment. Chlorine dioxide was found to have higher disinfection efficiency than PAA treatment. PAA/UV treatment did not show any synergistic effect for eliminating generic E.coli.