## 4 Water Sterilization and Disinfection  
As mentioned earlier, conventional water treatment methods cannot satisfactorily remove all contaminants. For instance, species that are resistant to Cl (e.g., bacteria spores and protozoa) are not eliminated by conventional methods, although AOPs can be used with traditional techniques such as filtration to decompose these contaminants. Furthermore, NTAPP species (charged species, reactive species, and UV photons) have significant effects on sterilization and microorganism disinfection. Previous studies have demonstrated that the interaction between plasma and water can produce H\({}_{2}\)O\({}_{2}\), which has wide scope to disinfect the various microorganisms such as viruses, molds, and bacteria. It is worth noting that some chemical and physical parameters of the liquid (e.g., overall hardness and total dissolved solid, and conductivity) change slightly due to interaction with the plasma [44]. Substantial research has been conducted in this area in recent years. The present article reviews numerous research papers concerning the interaction of plasma with wastewater to inactivate bacteria. [PERSON] et al. [87] used an AC-driven microplasma jet array under atmospheric pressure with a repetition frequency of several kilohertz to inactivate resistant _Pseudomonas_ sp. HB1 cells in water. The results showed that the species with short lifetimes (such as charged particles and OH radicals) in microplasma jets could effectively inactivate resistant _Pseudomonas_ sp. cells. With 108 colony-forming units (CFUs) in an 80 mL suspension, all _Pseudomonas_ sp. cells were killed within 6 min of plasma remedy. Various studies have been conducted on the elimination of _Escherichia coli_ in wastewater using NTAPP. Similarly, [PERSON] et al. [88] considered the effects of cold plasma produced in a closed chamber on _Escherichia coli_ inactivation under atmospheric pressure. All samples in this research were directly and indirectly treated with plasma, and the impacts of treatment and post-treatment time were investigated. The results demonstrated that this plasma configuration can eliminate high concentrations of _Escherichia coli_ in water in several seconds. An important benefit of this approach is the absence of post-processing pollution. Plasma treatment directly leads to the complete inactivation of bacteria. Meanwhile, [PERSON] et al. [89] used water-pulsed NTAPP for water disinfection (_Escherichia coli_ inactivation). Their results indicated that the liquid conductivity had a significant role in the creation of plasma containing reactive species and UV emission and revealed its effect on disinfection. The disinfection effect was dramatic when the conductivity of water was up to 1.5 mS/cm. This study indicated that during water sterilization, OH radicals has strong chemical sterilizing power. However, because of the short lifetime of OH radicals, which is only a few milliseconds, it is difficult to use OH radicals to disinfect pathogenic microbes directly. [PERSON] et al. [43] investigated the effects of various ROS with short lifetimes on yeast cell inactivation in a liquid and showed that \({}^{1}\)O\({}_{2}\), OH radicals, and O\({}_{2}\)\({}^{-}\) are the three main particles created in a plasma-liquid system. Based on the experimental results, OH radicals has the least contribution to plasma inactivation among the plasma species. In contrast, O\({}_{2}\)\({}^{-}\) and plasma acid play major roles in inactivation. It is worth noting that in the plasma-liquid interaction, \({}^{1}\)O\({}_{2}\) is a more significant antimicrobial factor than the species mentioned earlier (i.e., OH radicals and O\({}_{2}\)\({}^{-}\)). It should be noted that despite the strong oxidizing properties of OH radicals, it does not have the capacity for significant diffusion [43]. Because of its short life and high reactivity, it can only react with nearby particles.