Thesis (Ph. D.)--University of Hong Kong, 2007. / Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Also available online.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

In the past, water treatment plants have stopped the application of pre-filter oxidants to create a bioactive filtration process to remove soluble Mn. After the cessation of pre-filter oxidants, a Mn desorption phenomenon was seen where effluent Mn exceeds influent Mn concentrations. The reason for the sudden increase in effluent Mn was not known, but it was hypothesized that Mn-reducing bacteria on the filter media play a substantial role in this phenomenon. The primary goal of this research was to assess the role of Mn-reducing microorganisms in the desorption of MnOx(s) from coated filters once pre-filtration chlorine ceased. A secondary objective included the development of a molecular detection method for Mn-reducing microorganisms in laboratory and environmental samples. Bench-scale filter column studies were completed to investigate the impacts of Mn-reducing microbial populations on desorption of Mn from MnOx(s) coatings. Secondarily, the effects of influent carbon loading and MnOx(s) age on Mn desorption were investigated. In situ vial assays were created to gain insight into the impacts of MnOx(s) age on Mn reducing microorganism bioavailability. Lastly, a qPCR detection method was developed that targeted the mtrB gene. Results determined that microbially mediated Mn desorption was possible when sufficient numbers of Mn-reducing microorganisms were present on the MnOx(s) surface and that those organisms contributed to the Mn desorption phenomenon. qPCR detection methods were able to show a greater number of Mn-reducing microorganisms in studies where Mn desorption was observed. Lastly, MnOx(s) age was shown to play an important, but unexplained, role in bioavailability. / Master of Science

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Physics / Master / Master of Philosophy

No description available.

No description available.

No description available.

Master of Science - Science / The analytical methods for speciation of manganese in three different types of matrices (water, milk and blood serum) was studied. Supported liquid membrane (SLM) extraction was optimized and successfully used for the extraction and preconcentration on Mn(II) from water, milk and blood serum. The extractant used was 15% (v/v) DEHPA with an organic membrane modifier, 10% (v/v) TOPO. All determinations of Mn(II) were carried out using Adsorptive Stripping Voltammetry. A SLM membrane probe was developed and used for the extraction of Mn(II) from smaller water, milk and blood serum samples. Membrane probe depth was optimized: probe depth - 2mm below donor solution. The membrane probe yielded higher extraction efficiencies compared to the flat spiral disk SLM unit. The Adsorptive Stripping Voltammetry method used for the determination of Mn(II) in water was optimized and used in other applications (determination of Mn(II) in aged and fractionated blood serum). The optimum conditions obtained: pH = 7.5-8.0, deposition potential = -(1.9V-2.0V), deposition time = 45-65s, equilibration time = 5s, stirring speed = 2000rpm, and no gelatin addition. The AdSV optimized parameters were then used for the analysis of Mn(II) in aged whole and fractionated blood serum. Size exclusion chromatography was used to obtain the blood serum fractions. It was determined that with aging, the concentration and thus extraction efficiency of free Mn(II) in blood serum matrix decreases. The spiked blood serum fractions were extracted and Mn(II) was determined with adequate reproducibility.