This study investigates the removal of natural organic matter (NOM) by alum coagulation, and the effect of ozonation on this process. The objectives of the research were: (1) to determine various properties of NOM that are important for its interaction with alum, and the effect of ozone on these properties, (2) to determine the calcium and aluminum binding capacities of unozonated and ozonated NOM, (3) to determine the sorption capacity of unozonated and ozonated NOM on aluminum hydroxide flocs, and (4) to use the data thus obtained to describe NOM removal by alum coagulation, and the effect of ozonation on this process. For the purpose of this research, NOM from a eutrophic raw water source (Forge Pond, Granby, MA) was isolated and fractionated into eight fractions based on relative hydrophobicity and acidity. The fractions isolated were: fulvic acid (FA), humic acid (HA), weak hydrophobic acids (WHYA), hydrophilic acids (HAA), hydrophobic bases (HYB), hydrophilic bases (HYB), hydrophobic neutrals (HYN), and hydrophilic neutrals (HN). The objectives of the research were met with a series of carefully controlled experiments conducted with raw water and the above fractions. It was postulated that the interactions between charged functional groups on NOM molecules and coagulants was responsible for the removal of NOM by alum coagulation. Two mechanisms for such removal are charge neutralization/precipitation and adsorption of NOM on aluminum hydroxide flocs. The acidic NOM fractions (FA, HA, WHYA and HAA) were negatively charged at all pH values, and hence interacted well with the positively charged aluminum hydroxide particles. Of all the NOM fractions isolated, the humic fractions (FA and HA) exhibited best adsorption on aluminum hydroxide flocs. The basic and neutral fractions (HB, HYB, HN and HYN) had little or no charge, and hence exhibited poorer adsorption than the acidic fractions. Calcium and aluminum complexation studies showed that the negative charge on most acidic fractions were only partially neutralized due to metal complexation. The charge on the basic and neutral fractions, on the other hand, were completely neutralized by metal complexation. Thus it was concluded that the charge neutralization/precipitation mechanism of NOM removal was only important for the basic and neutral fractions. Ozonation increased the charge of all NOM fractions. The adsorption of the acidic fractions on aluminum hydroxide flocs either remained unchanged or decreased upon ozonation. Hydrophilic neutrals (HN) on the other hand showed increased adsorption on aluminum hydroxide flocs on ozonation. It was also shown that in the case of Forge Pond water, increased NOM removal on ozonation may only be obtained if ozone is allowed to react with the non humic components of the NOM exclusively.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-8951 |
| Date | 01 January 1994 |
| Creators | Bose, Purnendu |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
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