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An experimental study of ATCC (American Type Culture Collection) 8739 Escherichia coli bacteria inactivation in water by means of pulsed dielectric barrier discharge (PDBD) atmospheric pressure plasmas is presented. Plasma is generated by an adjustable power source capable of supplying high voltage 25 kV puises, -30 Fs long and at a 500 Hz frequency. The process was conducted in a ~152 cm³ cylindrical stainless steel coaxial reactor, endowed with a straight central electrode and a gas inlet. The bacterial concentration in water was varied from 103 up to 108 E. coli cells per millilitre. The inactivation was achieved without gas flow in the order of 82% at 108 colony-forming units per millilitre (CFU mL-1) concentrations in 600 s. In addition, oxygen was added to the gas supply in order to increase the ozone content in the process, raising the inactivation percentage to the order of 90% in the same treatment time. In order to reach a higher efficiency however, oxygen injection modulation is applied, leading to inactivation percentages above 99.99%. These results are similarly valid for lower bacterial concentrations. [ABSTRACT FROM AUTHOR]

We propose a novel combined system of pulsed dielectric barrier discharges (PDBDs) and silver-modified natural zeolite (Ag–zeolite) in liquid in bubbles. The system was tested with the Escherichia coli bacteria immersed in water. In order to evaluate the efficiency of the system in bacterial inactivation a microbiological analysis was carried out; 9.82-ln of bacterial reduction was obtained using the combined system, whereas 0.43-ln of bacterial reduction was obtained using Ag–zeolite alone, and 6.26-ln with PDBD. The elapsed time was 10 minutes for the three treatments. [ABSTRACT FROM AUTHOR]

• The development of a DBD reactor to evaluate the bacterial inactivation in water. • Efficiency of treatment with a 6 log10 reduction for E. coli and S. typhi. • 12 kV with oxygen was the minimum voltage to inactivate E. coli and S. typhi. This work presents the study of the voltage and oxygen effect on bacterial inactivation in water using a pulsed dielectric barrier discharge (DBD) under atmospheric pressure, where Escherichia coli (E. coli) and Salmonella typhi (S. typhi) bacteria were used as model microorganisms. A cylindrical DBD reactor was developed and tested in applications to assay the efficiency of bacterial inactivation in water on a volume of 500 mL flowing continuously throughout the system assisted with a peristaltic pump at 4.4 ± 0.1 mL/s. The efficiency of the treatment reached a 6-log 10 reduction for both E. coli and S. typhi bacteria at 106 CFU/mL of concentration at the end of the first cycle of treatment at a minimum voltage of 12 kV with oxygen bubbling gas, concluding that there was a minimum voltage to produce inactivation of E. coli and S. typhi samples. Bacterial inactivation without the oxygen condition contrasted with the high rate of inactivation with oxygen at relatively low voltage discharges. [ABSTRACT FROM AUTHOR]