Title page for ETD etd-05032012-122257


Type of Document Master's Thesis
Author Bierlein, Kevin Andrew
URN etd-05032012-122257
Title Modeling Manganese Sorption and Surface Oxidation During Filtration
Degree Master of Science
Department Environmental Engineering
Advisory Committee
Advisor Name Title
Little, John C. Committee Chair
Knocke, William R. Committee Member
Tobiason, John E. Committee Member
Keywords
  • manganese
  • filtration
  • oxidation
  • sorption
Date of Defense 2012-04-30
Availability unrestricted
Abstract
Soluble manganese (Mn) is a common contaminant in drinking water sources. High levels of Mn can lead to aesthetic water quality problems, necessitating removal of Mn during treatment to minimize consumer complaints. Mn may be removed during granular media filtration by the “natural greensand effect,” in which soluble Mn adsorbs to manganese oxide-coated (MnOx(s)) media and is then oxidized by chlorine, forming more manganese oxide. This research builds on a previous model developed by Merkle et al. (1997) by either neglecting the empirically determined available fraction of sorption sites (referred to as the “simple” model), which took into account the fact that some adsorption sites in the porous media were inaccessible, or by explicitly accounting for the transport and reaction processes within the porous structure of the MnOx(s) coating (referred to as the “mechanistic” model). Both models were applied to experimental data and used to evaluate the oxidation rate constant, which was the only unknown parameter. An inverse relationship between the fitted reaction rate constant and chlorine concentration was observed, showing that the oxidation reaction does not depend on chlorine concentration for the experimental conditions considered. In a sensitivity analysis, the adsorption isotherm and reaction rate were found to have the greatest impact on predicted Mn removal. The simple model should prove useful for designing contactor units for manganese removal, provided its limitations are clearly understood, while the mechanistic model should be able to resolve differences in the various types of oxide coating (internal porosity, surface area and coating thickness) and will allow a more fundamental and mechanistically-consistent evaluation of the appropriate form of the oxidation rate expression. However, further research is needed to more completely characterize the adsorption and reaction mechanisms over the range of conditions commonly encountered in water treatment plants.
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