Inactivation of Escherichia coli in water by pulsed dielectric barrier discharge in coaxial reactor

Abstract

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 pulses, ∼30 μs long and at a 500 Hz frequency. The process was conducted in a ∼152 cm 3 cylindrical stainless steel coaxial reactor, endowed with a straight central electrode and a gas inlet. The bacterial concentration in water was varied from 10 3 up to 10 8 E. coli cells per millilitre.The inactivation was achieved without gas flow in the order of 82% at 10 8 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.

Effect of humic acid on E. coli disinfection in a microbubble-gas plasma reactor

“…An alternative approach for bringing about disinfection is the use of atmospheric pressure plasmas (APP), which generate a wide range of reactive species in addition to UV [8]. APPs have predominantly been investigated for their disinfective properties, making them highly applicable for inactivating microorganisms in wastewater [9,10]. Gils and co-workers investigated the inactivation of bacteria suspended in aqueous media by means of an atmospheric pressure plasma jet that generated both reactive oxygen species (ROS) and reactive nitrogen species (RNS) [11].…”

“…Numerous reactor configurations have been proposed to maximize mass transfer of reactive species into the liquid phase [10,13]. With the importance of high rates of mass transfer having been established, a novel microbubble-dielectric barrier discharge (DBD) plasma reactor has been developed to produce a wide range of reactive species in-situ (inside the plenum chamber for aeration) and bringing about their dispersion using microbubbles.…”

Experimental Evaluation of DBD Reactor Applied to Bacterial Inactivation in Water Flowing Continuously

“…Additionally, E. cloacae can attach to particles to protect it when chlorination is applied to water [6]. The effects of E. coli and E. cloacae bacteria involve diseases such as diarrhea, nausea, and headaches and can severely affect people with exposed immune systems, even causing death [1], [7]- [9].…”

“…In our previous studies [7], [20]- [23], inactivation of E. coli bacteria applying an energy of 100-117 mJ per pulse by DBD was achieved. Specifically, in the process carried out by [7], a volume of 15 mL of water was kept under static conditions in a DBD reactor.…”

“…Specifically, in the process carried out by [7], a volume of 15 mL of water was kept under static conditions in a DBD reactor. High performances were obtained for inactivation of E. coli bacteria: at 10 3 CFU/mL, 99.99%; at 10 6 CFU/mL, 99.96%, and at 10 8 CFU/mL, ∼90%, with 240, 360, and 600 s of exposure times, respectively, when oxygen was injected continually.…”