UV Light Inactivation of Human and Plant Pathogens in Unfiltered Surface Irrigation Water

Abstract

ABSTRACTFruit and vegetable growers continually battle plant diseases and food safety concerns. Surface water is commonly used in the production of fruits and vegetables and can harbor both human- and plant-pathogenic microorganisms that can contaminate crops when used for irrigation or other agricultural purposes. Treatment methods for surface water are currently limited, and there is a need for suitable treatment options. A liquid-processing unit that uses UV light for the decontamination of turbid juices was analyzed for its efficacy in the treatment of surface waters contaminated with bacterial or oomycete pathogens, i.e.,Escherichia coli,Salmonella enterica,Listeria monocytogenes,Clavibacter michiganensissubsp.michiganensis,Pseudomonas syringaepv. tomato, andPhytophthora capsici. Five-strain cocktails of each pathogen, containing approximately 108or 109CFU/liter for bacteria or 104or 105zoospores/liter forPh. capsici, were inoculated into aliquots of two turbid surface water irrigation sources and processed with the UV unit. Pathogens were enumerated before and after treatment. In general, as the turbidity of the water source increased, the effectiveness of the UV treatment decreased, but in all cases, 99.9% or higher inactivation was achieved. Log reductions ranged from 10.0 to 6.1 and from 5.0 to 4.2 for bacterial pathogens andPh. capsici, respectively.