# Plasma-Activated Tap Water Production and Its Application in Atomization Disinfection
## 3 Experimental Results
### Sterilization by PATW and PADW  
Figure 10 shows that the bactericidal effect of PATW and PADW (tap water and deionized water treated by plasma for 1 h) was almost the same. The concentration of _E. coli_ colonies on the culture medium in the control group was 10\({}^{7}\) CFU/mL, while in the experimental group, when PATW and PADW were mixed with E. coli for 15 min, the concentration of colonies dropped from the initial 10\({}^{7}\) CFU/mL to 10\({}^{2}\) CFU/mL. When the mixed reaction increased to 30 min, the concentration of colonies dropped from the initial 10\({}^{7}\) CFU/mL to 10\({}^{1}\) CFU/mL, and it was difficult to find surviving _E. coli_ on the medium. Therefore, the PATW and PADW both had a good bactericidal effect.  
Many short-lived vital bactericidal substances in PAW, such as superoxides, singlet oxygen, hydroxyl radicals, etc., are essential in sterilization [34, 35]. Storage often leads to the inactivation of these short-lived substances and affects the bactericidal effect of PATW [35]. Therefore, we studied the sterilization effect of PATW stored at low temperature (2 \({}^{\circ}\)C) and room temperature (30 \({}^{\circ}\)C) for 6 h and 24 h (Figure 11). Compared with the unpreserved PATW, the sterilizing ability of the PATW stored at 2 \({}^{\circ}\)C for 6 h did not change, while the sterilizing ability of the PATW stored at 30 \({}^{\circ}\)C decreased. When mixed with bacteria for 15 min, the bactericidal effect of PATW stored 2 \({}^{\circ}\)C was 6 orders of magnitude, while the bactericidal effect of PATW stored at 30 \({}^{\circ}\)C decreased to 4. When the reaction time increased to 30 min, the PATW stored at 2 \({}^{\circ}\)C still killed all E. coli in the culture medium, while less than 0.001% of _E. coli_ treated with PATW stored at 30 \({}^{\circ}\)C still survived.  
Figure 9: The **(a)** pH value and **(b)** conductivity of PATW and PADW as a function of activation time.  
The bactericidalal components in the PATW gradually decomposed, and the bactericidal effect of the PATW decreased by about 1 order of magnitude after 24 h of 2 \({}^{\circ}\)C and 30 \({}^{\circ}\)C storage (compare Figure 11a,b). Therefore, the PATW was suitable for storage at low temperatures for 24 h or for immediate use.  
We also used the disinfection door (Figure 12) to spray the atomized PATW onto the surface of clothes to study its disinfection effect. We evenly spread the E. coli solution on the surface of the clothes, used the disinfection door to atomize PATW for disinfection for 1 min and 2 min, respectively, and sampled and cultured the collected bacteria.  
Figure 12 shows the sterilization efficiency (the number of bacteria reduced after PATW treatment divided by the initial amount of bacteria) of treating the clothes with atomized PATW in the disinfection door for 1 min was 91.8%, and the sterilization efficiency increased to 96.7% for 2 min of treatment. By prolonging the preparation time of PATW and increasing the spray volume of PATW, the sterilization efficiency of atomized PATW might be further improved.  
Figure 10: Comparison of the number of surviving _E. coli_ after PATW and PADW treatment.