Nutrient pollution from industrial activity is an environmental problem that persists in
water bodies near urban settings, and has been a primary contributor to eutrophication,
bacterial contamination, and harmful algal blooms. Biogenic iron oxides offer a
potential solution to the treatment of lakes and rivers containing high concentrations of
phosphate, the limiting nutrient in aquatic systems. Soluble ferrous iron can act as an
electron donor for iron-oxidizing bacteria, which thrive in low-oxygen environments.
This results in the formation of insoluble ferric iron minerals, ideal adsorbents for
negatively charged phosphate. Conversely, iron-reducing bacteria reduce ferric iron to
form ferrous iron, resulting in the formation of secondary minerals depending on the
chemistry of the particular environment.
This project investigates the chemical conditions at which biogenic iron oxides have the
maximum adsorptive capacity, especially with respect to organic carbon content. A
simplified model of natural biogenic iron oxides was synthesized by co-precipitating the
mineral ferrihydrite (a common iron oxide) with the polysaccharide alginate, an
analogue to bacterial exopolysaccharides. At the levels of carbon investigated, organic
matter was not found to affect the adsorptive capacity of iron oxides at the C/Fe ratios
analyzed. Similarly, organic matter did not appear to significantly influence the rate of
reduction of ferrihydrite by the iron-reducing bacterium Shewanella putrefaciens CN32.
Presence of organics did however influence rates of reduction and the mineralogy of the
post-reduction precipitates. Phosphate adsorbed to iron oxides prior to microbial
reduction greatly increased both the rate and the extent of ferric iron reduced, and also
had an impact on the secondary minerals that formed (vivianite, green rust).
An improved understanding of these conditions could contribute to a more efficient
process by which iron-oxidizing bacteria are used for large-scale industrial water
treatment.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/37306 |
| Date | January 2018 |
| Creators | Meyers, Emily |
| Contributors | Fortin, Danielle |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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