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

Abstract

bFruit 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 michiganensis subsp. michiganensis, Pseudomonas syringae pv. tomato, and Phytophthora capsici. Five-strain cocktails of each pathogen, containing approximately 10 8 or 10 9 CFU/ liter for bacteria or 10 4 or 10 5 zoospores/liter for Ph. 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 and Ph. capsici, respectively.

Irrigation Water Quality—A Contemporary Perspective

“…Groundwater sources are generally considered less vulnerable to contamination by pathogenic microorganisms, while surface water and wastewater have a much higher potential for contamination. Farmers utilizing surface water for food crops, which are consumed raw should follow proper mitigation strategies to control contamination [132]. The method utilized for irrigation has a substantive role in pathogenic contamination of crops.…”

Evaluation of ultraviolet (UV‐C) light treatment for microbial inactivation in agricultural waters with different levels of turbidity

“…This indicated that the efficacy of the UV-C decreased with an increase in the turbidity of water. High levels of turbidity in water could affect the transmittance of UV light, influencing the efficacy of the UV-C treatment (Jones et al, 2014;Koutchma et al, 2009). The suspended particles in water can absorb and scatter the UV light, subsequently reducing disinfection efficacy (Andreadakis, Mamais, Christoulas, & Kabylafka, 1999;Jolis, Lam, & Pitt, 2001).…”

“…As the turbidity of groundwater and surface water is generally higher than municipal water (Topalcengiz, Strawn, & Danyluk, 2017), the efficacy of UV-C in these waters could be different. This study used a large volume of surface water and well water to simulate a water treatment system in agricultural settings (Jones, Worobo, & Smart, 2014). This study evaluated the efficacy of UV-C light treatment in reducing generic E. coli in surface water, well water, and their mixtures with different level of turbidity.…”

Ultrasound treatments improve the microbiological quality of water reservoirs used for the irrigation of fresh produce

“…Commercially available solutions found for these concerns are chemical disinfection such as sodium hypochlorite and calcium hypochlorite, UV-C light, filtration, electrochemical disinfection and ultrasounds (US) among others (Jones et al, 2014;Norton-Brandão et al, 2013). Among these methods, the efficacy of chlorination has been widely reported as the main technology used for the removal of biohazards to disinfect irrigation water (Suslow, 2013).…”

“…If the irrigation water is obtained from a surface water reservoir, it is considered as a high risk for pathogen contamination with foodborne pathogens such as Salmonella spp. and pathogenic Escherichia coli, because they are open to many routes by which microorganism causing plant disease or human food-borne illness can enter (Jones, Worobo, & Smart, 2014). This is the case of most of the irrigation water used in the south-east production area of Spain (Castro-Ibáñez, Gil, Tudela, Ivanek, & Allende, 2015).…”