Relationship Between Surface Electrostatic Potential and Deposition of Airborne Bacteria

Recent work has demonstrated that airborne bacteria can carry high net charges which may influence their deposition onto surfaces. This paper investigated the relationship between surface electric potential relative to ground and the deposition rate of airborne bacteria. Nutrient-agar settle plates were charged to potentials of +/-5, +/- 2.5, and 0 kV and microbial deposition (CFU/cm²middoth) enumerated in an office restroom environment. Results showed that deposition rates were enhanced in proportion to the surface potential to a maximum of approximately twofold. The results were consistent with framework modeling of the relative contributions of electrostatic attraction (ESA), sedimentation, and diffusion deposition rates. It is concluded that ESA can significantly increase deposition rates under selected conditions. This has implications for health-care settings and may provide a basis for application of particle-deposition-reduction engineering controls that have been successfully employed in the semiconductor industry.