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Dissertation
Formaldehyde formation during ozonation of drinking water
Doctor of Philosophy (Ph.D.), Drexel University
Jul 1999
DOI:
https://doi.org/10.17918/00000515
Abstract
Ozone is used as an oxidant and disinfectant in water treatment practices. However, partial oxidation of natural organic material (NOM) by ozone produces oxygenated by-products of low molecular weight, such as formaldehyde. Formaldehyde is considered as problematic compounds by the water industry due to their potential adverse health effects. The main objective of this study is to investigate the kinetics and mechanism of formaldehyde formation from NOM. Humic material was used as NOM model, mainly because humic material is the major constituent of dissolved organic matter in natural waters, and may be the primary source of precursor material for aldehydes. This research attempts to provide specific information on the effect of water quality parameters, specifically, pH and alkalinity, and different sources of humic material on generation of formaldehyde. The results showed that formaldehyde started to form upon ozonation of humic and fulvic acids, reached a peak value after 20-30 minutes of ozonation under the experimental conditions, and then started to decrease with continued ozonation. The interaction of ozone with aqueous based fulvic acid produced higher concentrations of formaldehyde compared to different types of humic acids. Formaldehyde formation was not affected significantly by bicarbonate ion within the concentration range of 0.5 mM and 2 mM, but less formaldehyde was produced in the presence of 6 mM bicarbonate. Formaldehyde accumulated faster at pH 8.5 than at pH 5.8. Formaldehyde formation was hindered in the presence of Br-. It was also observed that formaldehyde after formation went through further oxidation to form formic acid and subsequently carbon dioxide. In order to understand the mechanism and the kinetics of the chemical reactions that lead to the formation and oxidation of formaldehyde during ozonation, pure solutions of formaldehyde and formic acid were ozonated in batch reactors. Experimental data were used to test the proposed mechanistic and kinetic models developed for oxidation of formaldehyde and formic acid. After successful verification, these models were expanded to an overall model to predict formaldehyde formation from humic material. Formaldehyde formation in four different synthetic solutions of fulvic and humic acids, and one natural water sample was predicted fairly well by the overall model.
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Details
- Title
- Formaldehyde formation during ozonation of drinking water
- Creators
- Zehra S. Can
- Contributors
- Mirat D. Gurol (Advisor)Charles Nathan Haas (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xv, 192 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- School of Environmental Science, Engineering, and Policy (1997-2002); Drexel University
- Other Identifier
- 991014970314704721