Research On Novel Sterilization Technology Using Pulsed Electric Field/Pulsed Plasma

High pulsed power supply matched with reactors containing different electrodes configures has two applications in water treatment: pulsed electric field (PEF) and pulsed non-thermal plasma (NTP).Firstly, effects of operation parameters (pulsed frequency, temperature, initial concentration, conductivity and electrode distance) on inactivation of bacteria in oil field injection water by PEF were investigated, and those parameters were optimized. In addition, the combination treatment of PEF and ultrasound was explored. It was verified that PEF could inactivate saprophytic bacteria, iron bacteria and sulfate reducing bacteria effectively. Synergistic effects were also observed in the combined treatment on inactivation of saprophytic bacteria and iron bacteria. Effects of conductivity, initial bacteria concentration and Fe²⁺ on inactivation of bacteria in oil field injection water by NTP were studied. Moreover, the effects of various gases bubbling (oxygen, nitrogen and air) on bacteria inactivation were investigated as well as the effect of aeration intensity. The inactivation efficiency was greatly enhanced by gas bubbling and oxygen was proved to be the most efficient. After 150 s discharge with oxygen bubbling at 667 m³/(m³h) aeration intensity, the inactivation efficiencies of saprophytic bacteria, iron bacteria and sulfate reducing bacteria achieved 1.85, 4.51 and 5.70 log reduction, respectively.Secondly, the effects of energy per pulse as well as the inactivation under continuous flow mode treatment were investigated when PEF and NTP were adopted for drinking water disinfection, respectively. The inactivation efficiencies of spark gap switch pulse source and thyratron pulse source matched with reactors were compared. In addition, the effects of humic acids on both PEF and NTP inactivation were studied. The results revealed that the NTP was more prone to be affected by organic compound.On the basis of the above research, PEF/NTP treatments were compared with ClO₂, UV, H₂O₂ and O₃ from the perspective of efficiency, cost, D-value and safe disinfection. Water containing humic acids and two actual waters were treated. Results showed that all the methods could inactivate bacteria efficiently and quickly except H₂O₂. ClO₂ and UV were prone to be affected by organic compound. When source water of water supply general company was treated, ClO₂ needed least time to achieve 1 log reduction. PEF and UV had no disinfection byproducts. PEF could destroy bacteria more completely than UV. Organic compound had less impact on PEF inactivation. It was confirmed that PEF was an efficient safe disinfection technology and NTP could be used for removal of bacteria and pollutant simultaneously.Finally, the change of cell structure caused by PEF and NTP were analyzed. It was found that the cell was destroyed more fiercely by NTP treatment. Mechanism of NTP inactivation was analyzed. It was confirmed that the inactivation of NTP was the combination of pulsed electric field, ozone and those free radicals. The free radicals played important role in inactivation by NTP.