## 6 Conclusions and Future Perspectives  
This review summarized studies on various applications of plasma in water purification. Plasma production methods have been investigated extensively, and comparative research on the effectiveness of different discharge methods has also been conducted. These studies have shown that the interaction between the plasma and liquid could be used as an innovative water management solution that could eliminates contaminants in drinking water. Enhancing knowledge based on the advancements made in these research areas is essential to eliminate the gap between wet laboratory studies and business practice. Moreover, as these studies have addressed relatively unfamiliar questions, more thorough investigations are required to elucidate the mechanisms involved in plasma interactions with toxic substances in water. It is worth noting that further advances in this field will require more complex analytical methods. The present results define the role of non-thermal atmospheric pressure plasma in various wastewater management functions, with the purpose of overcoming several critical obstacles. Most of the above-mentioned literature has dealt with single-component treatments, but the use of organic molecule combination treatments is particularly unfocused. The exclusion efficacies of the considered compounds may not be transferable to actual situations when applied to organic molecules mixtures, and reactive species interactions among pollutants may appear. Because of these limitations, plasma processes are currently used only with air treatment inside clean rooms. Among these, one of the major concerns is effective plasma dose determination that can be used in treatment procedures. An effective plasma dose is described by working gas composition, plasma source configuration, biological target structure, and dose determination provides maximal progressive effect with minimal matrix damage. Nonetheless, the research reports included here emphasize the possibility of widespread use of plasma application for water purification. These findings are particularly interesting for industrial-scale applications rather than traditional waste air treatment processes based on economic traits. The scaling up plasma to industrial levels could be attained by attachment of numerous discharge components. Another major benefits of increasing the size of plasma devices from the laboratory scale to the industrial scale is the increased plasma-liquid interface size. The most effective devices for water treatment are those in which thin liquid layers are exposed to plasma because the plasma-liquid interface determines the treatable throughput. These configurations considerably increase the amount of plasma induced in the water. Furthermore, reactors with high throughput are convenient for practical applications. Conceptualization, A.B., Z.D., P.L., N.K., E.H.C. and N.K.K. ; formal analysis, E.H.C. and N.K.K. ; investigation, A.B., Z.D., P.L. and N.K. ; resources, E.H.C. and N.K.K. ; writing--original draft preparation A.B., Z.D., P.L. and N.K. ; writing--review and editing, A.B., Z.D., P.L., N.K. and N.K.K. ; supervision, E.H.C. and N.K.K. All authors have read and agreed to the published version of the manuscript. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Plasma Source** & **Chemical Pollutants** & **Refs.** \\ \hline DBD reactor & Bisphenol A and tributyltin & [98] \\ DBD device & Organophosphate pesticide(dimethoate & [99] \\  & and dichlorvos) & [99] \\  & Saline and azo dye (AR 73) & [100] \\  & & \\  & & \\  & & \\  & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Treatment approaches used for different pollutants. **Funding:** This report is financially supported by the National Research Foundation under Ministry of Science and ICT (NRF-2016K1A4A3914113), (NRF-2021R1C1C1013875) of Korean Government and Research Grant from Kwangwoon University in 2021. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable.