Plasma activated water (PAW): Chemistry, physico-chemical properties, applications in food and agriculture

Cold plasma is an emerging non-thermal disinfection and surface modification technology which is chemical free, and eco-friendly. Plasma treatment of water, termed as plasma activated water (PAW), creates an acidic environment which results in changes of the redox potential, conductivity and in the formation of reactive oxygen (ROS) and nitrogen species (RNS). As a result, PAW has different chemical composition than water and can serve as an alternative method for microbial disinfection. This paper reviews the different plasma sources employed for PAW generation, its physico-chemical properties and potential areas of PAW applications. More specifically, the physical and chemical properties of PAW are outlined in relation to the acidity, conductivity, redox potential, and concentration of ROS, RNS in the treated water. All these effects are in microbial nature, so the applications of PAW for microbial disinfection are also summarized in this review. Finally, the role of PAW in improving the agricultural practices, for example, promoting seed germination and plant growth, is also presented. PAW appears to have a synergistic effect on the disinfection of food while it can also promote seedling growth of seeds. The increase in the nitrate and nitrite ions in the PAW could be the main reason for the increase in plant growth. Soaking seeds in PAW not only serves as an anti-bacterial but also enhances the seed germination and plant growth. PAW could potentially be used to increase crop yield and to fight against the drought stress environmental conditions.