Control Effectiveness of Electrostatic Precipitation on Airborne Microorganisms

Abstract

Because there is an increasing incidence of microorganism infections, more concerns are made in microorganism engineering control for airborne infectious diseases. Electrostatic was considered to be promising to inactivate or kill microorganisms. In this investigation, the influences of microorganism species, relative humidity, gas flowrates, and electric voltage on control effectiveness of electrostatic precipitator (ESP) were evaluated in a laboratory test chamber. A Collison nebulizer generated Escherichia coli , Bacillus subtilis spores , cells of C. famata var. flareri , and Penicillium citrinum . The control effectiveness of this negative ESP was determined as the ratio, N S /N 0 , where N S and N 0 were the colony concentrations collected by Anderson one-stage samplers with and without ESP operation. The experimental results indicated that control effectiveness of ESP varied in a wide range. The microorganism penetration through the ESP decreased (from 81% to 42%) as the voltage of the discharge electrode increased (from +5 kV to +10 kV) at a flowrate of 60 L/min. At a fixed electrode voltage (+10 kV), microorganism penetration increased from 42% to 70% as the flowrate increased from 60 to 90 L/min. Regarding microorganism species, it was indicated that bacterial removal effectiveness was lower than those of fungus aerosols. This might be related to smaller aerodynamics sizes of bacterial aerosols. In regard to relative humidity effects, it was observed that control effectiveness of ESP at 85% relative humidity were higher than those observed at 65% relative humidity. This might be related to higher corona current observed at higher relative humidity at the same voltage. In addition, control effectiveness of ESP was demonstrated to be lower at higher gaseous flowrates and lower electric voltage.