| Summary: | 碩士 === 東海大學 === 環境科學與工程學系 === 107 === The quality of indoor air has drawn increasingly more attention because of its impact on the well-being of people who are exposed to the indoor contaminants. The presence of airborne and surface-bound bacteria is one of the primary concerns of indoor air quality. Various methods such as ultraviolet irradiation and chlorination have been commonly applied to inactivate bacteria. These methods, however, may be harmful to the health of the people and the environment.
This study examines the effectiveness of applying hexavalent ferrate, a powerful and environmentally benign oxidant, for the inactivation of several types of bacteria, including Escherichia coli, locally collected airborne bacteria identified as Micrococcus sp. and Staphylococcus kloosii, and a known pathogen in Staphylococcus aureus. All bacterial inactivation experiments were performed by mixing a pre-determined range of ferrate dosage with the bacteria inoculated in liquid Luria-Bertaini broths under room temperature. The reactants at the various dilution levels were then transferred to agar plates for inoculation to determine the growth of tested bacteria. The applied potassium ferrate had a purity of 15% experimentally determined.
Statistically, E. coli was completely inactivated within 5 minutes when a ferrate dosage of 3 mg/L was applied, and within 3 minutes when 5 mg/L was applied. Applying ferrate with higher purity (73% and 90%) did not result in significantly different inactivated rate. In all cases, a reaction time of 3 minutes was needed to completely inactivate E. coli.
The two airborne bacteria Micrococcus sp. and S. kloosii were completely inactivated in 5 minutes with a ferrate dosage of 100 mg/L and 200 mg/L, respectively. In comparison, a higher ferrate dosage (500 mg/L) and longer reaction time (30 min) were needed to completely inactivate S. aureus. No complete inactivation of S. aureus was observed when the applied ferrate dosage was less than 500 mg/L, demonstrating the higher resistance of S. aureus to ferrate.
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