Study on Inactivation of Escherichia Coli by Double Dielectric Barrier Discharge

A dielectric barrier discharge reactor with planeparallel electrode was utilized to disinfect the bacterium Escherichia coli (E.coli) to figure out the efficiency and mechanism of inactivation. During the treatment, a satisfactory potential for inactivation was observed. The inactivation rate reached 100% without any gases ventilated after 15 min of treatment and 100% with 0.6 L/min air after 9 min of treatment. The plasma was generated by a high-voltage alternating current regulator. The output power was around 33.8 W per cycle and the power utilization efficiency was 57.6%. The atmospheric sources of sole nitrogen or sole oxygen were not favorable for the bacterial inactivation, while air plasma presented better inactivation results. It indicates that the presence of active species containing nitrogen and oxygen, generated from the air plasma, or other active species derived from NOx, such as ONOOH, which is produced by NO2 and OH, plays a more important role on bacterial inactivation. The ventilation result is different from others' studies. Moreover, scanning electron microscopy was used to observe the E. coli cell topography alternation. After discharge, E. coli seemed to be more shrunken and blurred. Cells finally collapsed and part of them got stuck to each other.