## 3 Water Purification
Different techniques can be used for color removal, such as oxidation-reduction, coagulation-floculation-sedimentation-filtration, and the use of activated C or adsorption-absorption. These processes have important effects on the water treatment cost and require additional media or chemical compounds. Figure 6: (**a**) Block diagram of water treatment and (**b**) water treatment with NTAPP (reprinted from [44]). Importantly, [PERSON] et al. [83] showed that dissolving O\({}_{3}\) and OH radicals in the water by maximizing the chemical processes occurring in the O\({}_{3}\) plasma system can remove color without additional chemical media. It has been proven that O\({}_{3}\) plasma can treat peat water by reducing the color level in the water [83]. An additional review by [PERSON] et al. [41] presented an overview of the limitations and future of advanced oxidation technology using plasma for water treatment. They stated that plasma is produced on the liquid surface due to the liquid-gas interactions. This production method can be performed in different ways, including through glow discharge electrolysis, DBD, and gliding arc discharge. Due to the ability of plasmas to undergo AOPs, this technology has been considered for the decomposition of organic-compound-polluted water. [PERSON] et al. [84] reported the effects of spark plasma discharge on sulfate-reducing bacteria and the inactivation of acid-producing bacteria in water and described the residual effects of plasma treatment on bacterial inactivation. They investigated both clear and dark produced water. The cost of energy for 1-log reduction of acid-producing bacteria in both clear and dark waters was 1.5 kJ/L in the flow rate range of 0.063-0.315 L/s used in the flow tests. Their work stated that the energy efficiency of bacterium inactivation in clear water depends on the type of plasma. Meanwhile, [PERSON] et al. [85] used a prototype of plasma technology for water purification and indicated that it could decrease water source contamination mainly due to sewage spill by the industrial sector. To remove pathogens from contaminated water, the prototype converted the liquid water into plasma. The properties in plasma leading to pollutant destruction are UV radiation, shock waves, and electric fields. The plasma used in this work was obtained by applying an AC power supply to high voltage electrodes. Further new technology for water treatment, as the first kind of direct plasma system that produces plasma in contact with water, is corona discharge [86]. This technology employs plasma discharge to generate RONS in a powerful and efficient manner. The solution is chemical free, using electric energy to generate strong oxidants from the air and water itself. Therefore, it can readily destroy dissolved organic pollutants in water while effectively removing color and odor. Creating an economical alternative to conventional ozonation was the original motivation for using plasma directly in water treatment. The main idea was to generate oxidant species at the right positions in the water and use the power of OH radicals. The formation of such species is a considerable benefit. This technology has advantages such as that the solution is chemical free, and that electric energy is used to generate strong oxidants from the air and water itself. In addition, unlike UV-based approaches, the process is insensitive to turbidity, and unlike chlorine and peroxide techniques, corona discharge has no need for chemical logistics, storage, or usage.