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

In this paper, we present the evaluation of a DBD reactor that generates an energy per pulse of 65.3 mJ in order to inactivate E. coli ATCC 8739 at 103, 106, and 108 CFU/mL order concentrations and E. cloacae CDBB-B-963 at 103 and 107 CFU/mL order concentrations, in a volume of water flowing continuously. Particularly, experimentation is focused in 500 mL, under atmospheric pressure. The DBD reactor was coupled to a peristaltic pump type, a cooling jacket, containers for water in treatment and cooling fluid, and systems to monitor the experimental conditions. The implementation of the experiments was carried out at three different fluid flow rates: 2.0±0.1, 3.5±0.1, and 4.4±0.1 mL/s; in each of them the time required to carry out a cycle of treatment corresponded to 256±7, 143 ± 2, and 113 ± 1 s, respectively. During the DBD application, water flowed continuously at recirculation mode, promoting the continuous oxygen injection at 8.3 mL/s. In the three established fluid flow rates, the efficacy of treatment reached 100% in inactivation of E. coli bacteria at 103 and 106 order concentrations at the end of the first cycle of treatment. At 108 CFU/mL order concentration, complete inactivation of E. coli bacteria was achieved at the end of the fourth cycle of treatment. Meanwhile, E. cloacae bacteria showed an inactivation of 100% at the end of the first cycle of treatment at 103 order concentration; when the order concentration increased to 107, the efficacy of the process depended on the fluid flow rate, at 3.5 ± 0.1 and 2.0 ± 0.1 mL/s survival was 0% at the end of the first cycle of treatment; nevertheless, at the highest (4.4 ± 0.1 mL/s), an additional cycle was required.