Treatment of water and E. Coli suspensions by dielectric barrier discharge in argon/oxygen atmospheres

Summary form only given. It is well known that plasma treatment results in inactivation of microorganisms in suspension. Furthermore, it is a fact that plasma treatment of water results in acidification and generation of several species. In this study a surface dielectric barrier discharge arrangement was used. Liquids were treated in a lower shell of a petridish, they were non-stirred and have no direct contact with the plasma (distance between liquid surface and plasma arrangement was 5 mm). The plasma was ignited in argon atmosphere with different oxygen admixtures from 1 up to 40 %. The first aim of these investigations was to show the influence of the percentage oxygen admixtures on the inactivation of suspended E. coli by DBD treatment. Therefore E. coli have been suspended in physiological sodium chloride solution to reach a concentration of 10⁷ cfu ml^-1. Volumes of 5 ml of this microorganism suspension were plasma treated for 2 min, each, in different argon oxygen atmospheres and the numbers of viable E. coli were estimated and compared in correlation with the percentage oxygen admixtures. Furthermore, after DBD treatment for different times and in different argon oxygen atmospheres of 5 ml distilled water the pH decrease and concentrations of hydrogen peroxide were determined and compared with each other. Based on these results, it was observed that an inactivation maximum of E. coli was at an oxygen admixture of 4-5 % to argon atmosphere. The inactivation of E. coli and the generation of the detected hydrogen peroxide, as well as acidification, are discussed.