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A Pilot-scale Evaluation of Soluble Manganese Removal Using Pyrolucite Media in a High-Rate Adsorptive Contactor
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Soluble manganese (Mn) is a common water contaminant which can cause discoloration of water and staining if not treated properly in a water treatment plant. The â natural greensand effectâ is one of the proven methods for efficient removal of Mn from water. Therefore, research is ongoing to develop different ways to effectively create the natural greensand effect in a post-filtration sorptive contactor for application at water treatment facilities. The research reported by Zuravnsky (2007) focused on the use of oxide-coated media in a post-filtration contactor and served as a starting point for the research reported in this thesis. As a part of the work conducted by Zuravnsky (2007), a preliminary model was formulated to predict soluble Mn removal via adsorption and oxidation onto large-size MnOx(s)-coated media. A major part of the current research was to calibrate the proposed model in predicting the soluble Mn removal performance by incorporating a statistical non-linear regression method to estimate a best-fit value for the fitting parameter kr, the rate constant associated with Mn oxidation by free chlorine. The research work included an 18-week pilot-plant study conducted at a water treatment facility in Newport News, VA. A contactor column loaded with 27â of pyrolucite media was operated at varying applied water conditions. Hydraulic loading rate (HLR), temperature, pH and influent free chlorine concentration were the operational parameters that were varied and their effect on the Mn removal performance evaluated. The resulting data were then used in the model to aid in its calibration and to obtain the best-fit kr values corresponding to effective Mn removal for the various operating conditions. Soluble Mn removal in the contactor column was directly dependent on solution pH and initial free chlorine concentration. The applied water temperature and HLR also had a small impact on the Mn removal profiles observed. On analyzing the results obtained from the model, it was noted that the best-fit kr values for the pilot plant data increased with increasing solution pH (When temperature = 200C and the initial Cl levels were below 1.5mg/L). Also, the Mn uptake capacity of the pyrolucite media increased with both an increase in initial Mn concentration and solution temperature. Long-term operation of the contactor also resulted in significant head loss accumulation in the upper portion of the contactor column, most probably due to MnOx(s) deposition on the media and partial blockage of contactor void spaces. Media fluidization was necessary to address this operational issue.
- Masters Theses