## 3 Water Purification  
Traditional water treatment methods cannot remove various pollutants such as halogenated hydrocarbons, aromatic compounds, pentachlororophenol, pesticides, herbicides, and more recently pharmaceuticals. The effective decontamination of wastewater and unpurified water from natural sources is a major social concern [78]. The conventional strategies for water filtration and sanitization, although successful at eliminating numerous toxins, are less capable of absolute purification. Recent exploration has revealed the presence and risky nature of destructive natural mixtures present in many water supplies, which cannot be eliminated by customary decontamination methodologies [79]. These contaminants include endocrine-disrupting compounds and pharmaceutical drugs as well as by-products of manufacturing processes and certain pathogenic microorganisms, which are robust against filtration and chlorination and are directly correlated with human health, causing hormone disruption, cancers, and birth defects [78; 79]. Among these substances are volatile organic compounds, which can become stuck in air and water and thus can pollute surface and groundwater resources and threaten the drinking water supply. This concern regarding the tainting of our water supply demands the presentation of new, productive, and viable water purging technologies capable of eliminating these contaminants. To check for these pollutants, innovations and techniques that completely remove water pollution will be necessary. NTAPP discharges have recently been used to resolve this issue. Plasma reactions can occur in wastewater via two mechanisms: plasma formation in contact with the liquid surface and production directly within the liquid. In the first mechanism, the plasma interacts directly with the liquid surface at the liquid-gas interface. The chemical reactivity in plasma is evolved using the interface reactions and transport of reaction species from the gas phase to the liquid phase. The second mechanism can be implemented via the propagation of streamer discharge either within bubbles generated by external gas injection or in microbubbles produced by the field [50]. NTAPP is a source of charged particles, radicals, excited and reactive species, shockwaves, ultrasound, and UV radiation, which are not generally harmful to health or the environment. These species can significantly inactivate bacteria and destroy viral infections by degrading organic molecules. In recent years, different kinds of plasma with various reactor geometries have been studied for water treatment applications. It has been shown that a straightforward gas-phase discharge in contact with liquid water is better than breaking the discharge using submerged electrodes in the water. In 2017, [PERSON] et al. [50] designed a micro discharge plasma jet (MDPJ) with a simple geometry and low power consumption. Their discharge system consisted of a high voltage power supplier, high voltage electrode, grounded electrode, dielectric tube, and developed reactor. The authors showed that the stable production of plasma and active species such as RONS is key for water purification using an MDPJ. When a gas enters the inner electrode, the gas velocity increases due to the increasing gas flow rate, and consequently, the length of the plasma jet increases as well [50]. The reactive species produced by plasma jets, such as O, H\({}_{2}\)O\({}_{2}\), OH radicals, NO, and NO\({}_{2}\), offer strong sterilization of _Escherichia coli_ and thereby contribute to water purification [80]. Even a low amount of H\({}_{2}\)O\({}_{2}\) can be used as a strong oxidizing agent for pathogen sterilization. Nitric and nitrous acid, which are generated by NO\({}_{2}\) and NO, are the main chemical species that cause acidification of the treated fluid.