Influence of non-thermal plasma reactor geometry and plasma gas on the inactivation of Escherichia coli in water

Abstract

The inactivation of bacteria Escherichia coli (E. coli) by non-thermal plasma (NTP) was investigated using argon, air and 1:1 mixture of air/Ar as plasma gas on five different reactors. The experiments were carried out in triplicate in each reactor, using 60 mL of distilled water pre-inoculated with E.coli. The physical-chemical analysis of pH, conductivity, nitrite, nitrate and temperature were performed soon after of 10 min of NTP treatment. The microbiological analysis of E. coli inactivation was performed using 100 μL samples withdrawn from the plasma reactor after 10 min and compared with the positive and negative control test results. The best performance were achieved whit the NTP reactors working with the upper electrode in the gas phase using 1:1 air/Ar and air as plasma gas. The results are linked with the E. coli inactivation due to membrane rupture by the NTP discharge followed by the attack of the reactive species produced in the solution. The E. coli inactivation was only partial using argon as plasma gas and the direct barrier discharge reactors showed partial inactivation even when air was used as plasma gas.

Keywords: Escherichia coli inactivation; Non-thermal plasma; Reactor geometry; Water treatment.