## 3 Results and Discussion
### Treatment of Flowing and Circulating Liquid  
The evaporation of liquid reported above might be a problem for AALCA treatment; however, considering the high efficiency of RONS production and the moderate temperature of the liquid treated using the proposed method, AALCA treatment looks promising for practical PTW use. A possible approach to reduce the production cost of PTW and ameliorate the problems associated with heating and evaporation of the liquid is treatment by continuous flow of liquid. Treatment of a flow of DI water was performed using the same setup and two peristatic pumps, as shown in Figure 10. Pristine DI water was introduced to a dish at a flow rate of 10.25 mL/min using the first pump and PTW was evacuated from the dish at a flow rate of 10 mL/min using the second pump. The flow allowed for reducing the temperature of the liquid during treatment. It was found by thermographic measurements (Figure 10) that the temperature of the treated water was about 45 \({}^{\circ}\)C in the area of contact with plasma after 5 min of operation, which was significantly lower than the case of the 5 mL sample treatment. Figure 10 shows a thermographic image of plastic tubes with water on the input and output of the plasma treatment device. The temperature of the water increased from about 25 \({}^{\circ}\)C to about 30 \({}^{\circ}\)C during the treatment (similar results were confirmed by measurements using a thermocouple). The use of flow allows for a temperature of the produced PTW below 37 \({}^{\circ}\)C, which is safe for the human body and could be used in medical applications [47; 60]. Additionally, the difference in the flow rate allowed for compensation of the evaporation of the liquid and retention of the same level of liquid inside the dish, ensuring the same discharge gap and parameters of the plasma during treatment. Figure 9: Dependency of the number of surviving bacteria on the duration of incubation after mixture of _E. coli_ suspension with DI or tap water treated with AALCA, DI water treated with NEAPRS, or DI water treated with AALCA at a 10 mL/min flow. The treated water was collected from the output of the second pump and concentrations of RONS in the collected PTW were estimated using HPLC and ion chromatography. Estimated concentrations of H\({}_{2}\)O\({}_{2}\), NO\({}_{2}\)\({}^{-}\), and NO\({}_{3}\)\({}^{-}\) in the produced PTW were 9.6, 0.2, and 32.2 mg/L, respectively, as shown in Figure 7. The pH value of the produced PTW was about 3.25. The production rate of RONS was comparable to the treatment of stationary samples of 5 mL. Despite the reduced efficiency of production of NO\({}_{2}\)\({}^{-}\), the total amount of RONS in the case of the flow of water was still two orders of magnitude higher than the amounts observed for the case of conventional NEAPPJ or DBD [14, 20, 32, 43]. [PERSON] et al. reported PTW production by cold plasma treatment at ambient air of 50 mL of circulating liquid at a flow rate of 200 mL/min [18]. It is difficult to perform a direct comparison of results considering the difference in the flow ratio of the liquid and the experimental setup. It would take 5 min to produce 50 mL of PTW using AALCA with a 10 mL/min flow of the water used in the present work; therefore, the results of the present work were compared to the results reported by [PERSON] et al. for 5 min of treatment (0.4 of H\({}_{2}\)O\({}_{2}\), 0.2 of NO\({}_{2}\)\({}^{-}\), and 0.75 of NO\({}_{3}\)\({}^{-}\)) [18]. It can be clearly observed in Figure 7 that treatment with AALCA is more effective than the method reported by [PERSON] et al., and treatment of a liquid flow can be applied to produce a large volume of PTW. However, the concentration of NO\({}_{2}\)\({}^{-}\) in the produced PTW was lower than that of the fast treatment of stationary liquids with small volumes, and the ratio of concentrations of NO\({}_{2}\)\({}^{-}\) and NO\({}_{3}\)\({}^{-}\) depends on the flow rate, duration of treatment, and discharge parameters.