Performance of an atmospheric plasma discharge reactor for inactivation of Enterocococcus faecalis and Escherichia coli in aqueous media

Several non-thermal plasma-based systems have been explored for the treatment of water. In this study, the performance of an atmospheric pressure gas-liquid phase air non-thermal plasma (NTP) reactor to inactivate both gram-positive (Enterococcus faecalis (E. faecalis)) and gram-negative (Escherichia coli. (E. coli)) bacterial species was studied. The time-dependent effects of different applied voltages (2 kV, 4 kV, and 6 kV) on microbial decontamination were investigated in addition to changes in solution pH, conductivity and electrode temperature. Moreover, reactive oxygen species (ROS), hydroxyl radical ((OH)-O-center dot) and ozone formed during NTP treatment were quantified. Scanning Electron Microscopy (SEM) analysis revealed alterations in the morphological structure of bacteria with NTP treatment. As compared with gram-negative bacteria, gram-positive bacteria was found to be more susceptible to NTP disinfection effects. Inactivation kinetics of E. faecalis and E. coli. was studied in detail and complete inactivation of E. faecalis and E. coli. was observed in 10 min (4 kV) and 15 min (6 kV), respectively. Results confirm that NTP treatment of water is a promising approach for the decontamination of pathogenic bacterial species.