Date of Award

3-2020

Document Type

Thesis

Degree Name

Master of Science in Nuclear Engineering

Department

Department of Engineering Physics

First Advisor

Larry W. Burggraf, PhD

Abstract

Aerosols produced by turbulent mechanical mixing and bubble aeration at Waste Water Treatment Plants (WWTPs) become bioaerosols with the entrainment of biological materials. Bioaerosols become a public health risk when human pathogens are present. This study evaluated bioaerosols containing Bacillus globigii (BG) spores, and the effects that aeration rate and the addition of Free-Floating Carrier Media (FFCM) had on the amount of BG spores collected following aerosolization. A series of laboratory-scale experiments investigated two different sizes of floating polystyrene spheres as FFCM and four different aeration rates. When the differences in compared aeration rates were sufficiently large, a positive correlation was observed between increasing aeration rate and increasing bioaerosol production. The maximum increase from 0.50 to 1.00 L/min resulted in a 97.58% increase in the percent of starting BG spores captured after aerosolization. The addition of FFCM of both sizes reduced the amount of BG spores captured when compared to the control. Smaller spheres (0.42 cm diameter) consistently attenuated BG bioaerosol emissions more effectively than those with larger (1.91 cm) diameters, with a mean control efficiency of 93.03% compared to 83.95%. Statistical analysis showed a significant increase in the ability of smaller diameter FFCM to attenuate bioaerosol production at the two higher investigated aeration rates. This study was the first, to the author’s knowledge, to investigate multiple effects on bioaerosol production where the aerosol contained strictly bacterial endospores. As a part of a larger investigation including laboratory scale and pilot-scale WWTP research, this study is the first in a series of studies intended to investigate the effect of experimental scale on bioaerosol production. Results related to effects due to scale can be applied to better predict bioaerosol behaviors in operating treatment plants.

AFIT Designator

AFIT-ENP-MS-20-M-110

DTIC Accession Number

AD1101480

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