Deactivation of Escherichia coli with different volumes in drinking water using cold atmospheric plasma

Abstract

This experimental study aimed to evaluate the potential of cold atmospheric plasma jet to deactivate Escherichia coli from drinking water. We studied the effect of the volume of water samples on the performance of plasma jet on deactivation of E. coli of 1, 500, 1,000, 1,500, and 2,000 cubic centimetres. The results of deactivation of E. coli in 500 and 1,000 cc water samples were the same as one cc of a water sample and we observed 8-log reduction of E. coli using 50 W. In 1,500 and 2,000 cc water samples at 8 min using a power of 50 W, 4.5 and 2.9 log reduction of E. coli was achieved and while we used 20 W, 2.5 and 1.8 log reduction of E. coli bacteria was performed. This indicated that the increasing volume of water above 1,500 cc caused the reduction of the efficiency of E. coli removal. Also, increasing power caused to increase E. coli removal efficiency. In addition, we monitored changes in pH values and temperature during experiments. Using 20 W, the temperature was increased (natural temperature of the water was 22 • C) 2 • C after 8 min while applying 50 W, the temperatures were raised 5 • C. pH of the water after 8 min in the 1,000 cc water sample, with an input power of 20 W, decreased from 7.1 to 5.5; while the input power was 50 W, pH changed from 7.1 to 4.3. With an increase in plasma irradiation time, the number of E. coli had a significant decrease per min while using in samples of 1 cc. After 8 min, we observed 4-log reductions of E. coli with the input power of 20 W and 8-log reduction of bacteria with the input power of 50 W. In 1,500 and 2,000 cc of water samples using plasma radiation for 8 min, 2.5 log and 1.8 log reduction of E. coli was achieved, respectively. This means that an increasing volume of water above 1,500 cc needs more power and time to deactivate E. coli from the water.

Direct Treatment of Liquids Using Low-Current Arc in Ambient Air for Biomedical Applications

“…It was found that the number of surviving E. coli was about 2 × 10 3 mL −1 after direct plasma treatment for 10 s and decreased to the colony counting method detection limit of 10 mL 1 after 30 s, showing a 6-log reduction in the concentration of bacteria. As shown in Figure 8, the bactericidal effect of treatment with AALCA was significantly higher than the bactericidal effect of treatment with NEAPRS and APPJ, corona, or DBD discharges reported elsewhere [9,43,[49][50][51][52][53][54][55][56]. It was confirmed by thermographic observation that the suspension was heated by irradiation to temperatures up to 38 • C, which is below the temperature harmful for E. coli reported elsewhere, suggesting that heating of the sample was not involved in the sterilization process [57].…”