Measurement of electrical charges carried by airborne bacteria laboratory-generated using a single-pass bubbling aerosolizer

Bioaerosol generators are likely to produce electrostatically charged particles but there is few published data about electrical charges carried by laboratory-generated microorganisms. In this study, the objectives were to measure the fraction of neutral particles and the number of elementary charges per particle as a function of the aerodynamic diameter of airborne bacteria (Escherichia coli, Enterococcus hirae), produced by a “Liquid Sparging Aerosolizer”-type generator in a range from roughly 0.6 to 2 µm. The experimental setup includes an electrostatic precipitator and real-time devices (electrometer, APS, ELPI). Experimental results obtained for various operating conditions show that the higher the bubbling airflow, the greater the fraction of neutral particles in the bioaerosol (from around 30 to 50%) and the greater the absolute value of the average number of elementary charges carried by bacteria (from around -10 to -60 elementary units). To our point of view, a neutralization step, with expected negative effect on the viability of sensitive microorganisms, seems unnecessary. Our work suggests that the use of the neutral fraction downstream of an electrostatic precipitator is possible and may be advantageous instead of using bipolar neutralizers.