A Study of Plasma Inactivation Effects on Desulfovibrio Bastinii in Liquid Using Dielectric Barrier Discharge

Sulfate-reducing bacteria (SRB) can lead to severe environmental and industrial problems, especially in the oil and gas industry, because of they produce corrosive, reactive, and toxic sulfide. In this paper, dielectric barrier discharge (DBD) plasma was used to inactivate Desulfovibrio (D. bastinii, a common SRB) in liquid. The influences of different parameters including discharge gases (e. g., oxygen, air, nitrogen, and argon), change of pH value and temperature, the produced hydrogen peroxide and ozone, on the inactivation were investigated in details. Our experimental results showed that the germicidal efficiency (GE) of oxygen plasma was superior to those from others gases such as air, nitrogen, and argon. With oxygen as the discharge gas, almost 100% SRB were killed in less than 4-min plasma exposure. The GE reached to 6.20, 6.01, and 2.82 after the same exposure period under air, nitrogen, and argon discharging, respectively. It was found that plasma reactive species including hydroxyl radical, oxygen radicals, N atom, NO, and NO2 had profound effects on plasma inactivation of SRB by reacting with various macromolecules in only minutes such as cellular envelope and even the intracellular organization of SRB. Leakage of intracellular proteins, nucleic acid, the production of malondialdehyde, and damages to the cell microstructure structure of SRB after plasma treatment were observed to prove the inactivation mechanisms. These results showed that the DBD plasma is an efficient way in the inactivation of SRB in liquid. On the other hand, the change of pH value and temperature, produced hydrogen peroxide or ozone themselves played far less roles in plasma inactivation of SRB. In addition, the pulsed electric field and ultraviolet photons also made a little contribution to SRB inactivation.