Sorption of Boron and Chromium Onto Solids of Environmental Significance: Implications for Sampling and Removal in Water Treatment
|dc.contributor.author||Parks, Jeffrey L||en_US|
|dc.description.abstract||The chemistry, analysis, treatment, and occurrence of boron and chromium are of high interest since they are under consideration for revised MCLs in potable water. As a starting point to guide regulatory decision-making, a comprehensive review of boron in relation to potable water was undertaken. That work demonstrated that there were not proven cost-effective options for boron treatment.
In preparation for a national survey of boron and chromium occurrence, it was discovered that existing analytical protocols sometimes '"missed" much of the total chromium that was present in water. It was determined that this was due to incomplete dissolution of particulates during routine Standard Method analysis of drinking water at pH 2.0. A more rigorous hydroxylamine digestion was developed and applied to circumvent this limitation.
In relation to treatment, it was determined that sodium carbonate softening at pH 10.3 is a viable method of removing various inorganic contaminants including chromium from drinking water sources. The nationwide survey revealed that removals varied widely and were dependent on solution composition. Median removal of chromium was 92%. Linear and nonlinear empirical models were fit to crudely estimate the removal of various contaminants in the presence of other elements that are typically removed in the softening process (i.e. calcium, magnesium, silicon, iron, and aluminum). Boron was removed to a much lesser extent (median removal 2%) in this study, consistent with the general result of the literature review that enhanced treatments will be required for this contaminant.
Modified precipitative softening was examined as a potentially attractive option to remove boron from natural waters. It was discovered that in some cases when magnesium and silicon were present, and if the pH was 10.8 ± 0.2, very high levels of boron removal (up to 90%) could be achieved versus 10% typically observed for conventional processes. This can be exploited to remove boron in waters naturally containing high levels of magnesium and silicon, or by adding supplemental amounts of either magnesium or silicon when one constituent is deficient.
|dc.rights||I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Virginia Tech or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.||en_US|
|dc.title||Sorption of Boron and Chromium Onto Solids of Environmental Significance: Implications for Sampling and Removal in Water Treatment||en_US|
|thesis.degree.grantor||Virginia Polytechnic Institute and State University||en_US|
|dc.contributor.committeechair||Edwards, Marc A.||en_US|
|dc.contributor.committeemember||Widdowson, Mark A.||en_US|
|dc.contributor.committeemember||Dietrich, Andrea M.||en_US|
|dc.contributor.committeemember||Eick, Matthew J.||en_US|
|dc.contributor.committeemember||Vikesland, Peter J.||en_US|
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