Bacterial decontamination of coastal seawater by means of electrical discharges

Summary form only given. Discharge of ships´ ballast water has introduced nonindigenous, species, including microorganisms into receiving waters around the globe. Multiple technologies have been proposed to decontaminate ballast water, including UV radiation, heating and chemical dosing. We have studied the bacterial decontamination effect of two types of electrical discharges in water: spark discharges and diffuse (glow) discharges. The effect was studied in coastal sea water collected at several locations in Norfolk, VA. The water was placed in a plexiglass chamber, which contained the electrodes, one or five pairs of cylindrical tungsten pins with diameters of 3 mm. The distance between the pins was set at 3 mm. They were connected to a simple, capacitive discharge circuit with an air spark gap as switch. The applied voltage was 7.5 kV, corresponding to an energy of 160 J dissipated in the water. Depending on the number of electrodes used, two different types of discharges were observed. With only one pair of pin electrodes, a spark discharge developed, similar to spark discharges in gases. With five pairs of pin electrodes, the electrical discharge generated a glow-like plasma between the electrodes. The lethal effect on the bacteria in the load was evaluated using a bioassay (plate counts of aerobic, heterotropic bacteria).