Effects of Operating Parameters on the Efficacy of Engineered Water Nanostructures (EWNS) in Inactivating Escherichia coli on Stainless-Steel Surfaces

Abstract

HighlightsThe efficacy of EWNS to disinfect surfaces was assessed at a bacterial concentration similar to pig barns.Liquid pH, liquid conductivity, and applied voltage were found to directly affect the efficacy of EWNS.The efficacy increased as liquid flow rate and distance between needle tip and counter electrode decreased.An E. coli reduction of 3.0 log was achieved on a stainless-steel surface after 15 min exposure to EWNS.Abstract. Several studies have shown the potential of engineered water nanostructures (EWNS) generated using a capillary electrospray system to inactivate foodborne bacteria; however, there is a lack of data on EWNS performance in inactivating microbes in livestock facilities. Thus, this laboratory-scale study investigated the effects of operating conditions on the efficacy of EWNS in inactivating Escherichia coli (E. coli) on coupons made of stainless steel, a common surface material in pig barns, at a bacterial concentration similar to levels found on pig barn surfaces. The electrospray module was composed of a capillary needle that was connected to a high-voltage power supply. The efficacy of the technology in inactivating E. coli was assessed with various operating parameters (i.e., applied voltage, distance between needle tip and counter electrode, and liquid flow rate, pH, and conductivity). The efficacy of the EWNS was found to be directly related to the liquid pH, liquid conductivity, and applied voltage, but inversely related to the liquid flow rate and distance between the needle tip and counter electrode. An E. coli reduction of 3.0 log was obtained after 15 min exposure to EWNS under the following operating conditions: liquid flow rate of 1 µL min-1, pH of 12, liquid conductivity of 14.72 mS cm-1, 2 cm distance between the needle tip and counter electrode, and -7.6 kV applied voltage. The results of this study can serve as an initial basis for the application of EWNS on surfaces in a real barn environment, where the presence of other factors, such as gases, dust, and other organic matter and microbial species, must be taken into account. Keywords: Electrospray, Engineered water nanostructures, E. coli, Stainless-steel surface, Surface decontamination.