Characterisation of engineered water nanostructures (EWNS) and evaluation of their efficacy in inactivating Escherichia coli at conditions relevant to livestock operations

Abstract

Exposure to bioaerosols in enclosed livestock facilities have been reported to pose health risks to workers and animals. Environment-friendly methods for reducing bioaerosol levels in enclosed animal production units could provide important environmental control options. In this study, laboratory-scale electrospray modules were developed to generate engineered water nanostructures (EWNS) to inactivate microbes. The EWNS were generated using three spray liquids (reverse osmosis (RO) water, saline water, and NaOH solution). The physicochemical properties (size, lifetime, reactive oxygen species (ROS) content) of the generated EWNS were characterised. Results showed that the average diameter of the EWNS droplets ranged from 40 to 45 nm. It was found that approximately 17% of the generated EWNS was still present after 4.5 h, and that the most predominant ROS generated was OH·. Furthermore, the efficacy of the generated EWNS in inactivating Escherichia coli was assessed under conditions relevant to livestock facilities. The electrospray modules were installed in an acrylic chamber, which was used to simulate the airspace in an animal barn. After 60-min treatment, reductions in E. coli concentrations inside the chamber were 69%, 64%, and 50% using RO water, saline water, and NaOH solution, respectively, at a ventilation rate of seven air changes per hour (ACH). At 15 ACH, the efficacy of the EWNS generated using RO water was 37%. The results show the potential of the EWNS technology as a microbial decontamination method for animal confinement buildings; however, in-barn tests are necessary before it can be fully implemented in commercial livestock barns. • An electrospray system was developed to generate nanosized EWNS. • The generated EWNS could remain airborne for hours. • The EWNS was found effective in inactivating Escherichia coli.