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Ozonation, or advanced oxidation processes (utilising ozone decomposition products as oxidants) are widely used in industrial waste water and drinking water treatment plants. In these applications the use of ozone is based on ozone and its decomposition by-products being strong oxidants. A case study revealed that several waterworks in South Africa successfully utilise ozone as a pre-oxidant for the treatment of raw waters. South Africa holds more than three quarters of the world’s viable chromium ore (chromite) reserves. Subsequently the Cr-related industry-within is considerable in size and a major producer of large volumes of waste materials. Chromium also occurs commonly in other industrial waste materials (e.g. fly ash and clinkers originating from coal combustion) and is a natural occurring element in natural sediments, since chromium is the 21st most abundant element in the earth’s crust with an average concentration of approximately 100 ppm. Considering the abundance of natural and anthropogenic Cr-containing materials in South Africa the possibility exists that some of these materials might be suspended in raw water entering water treatment facilities. In this dissertation, the possible oxidation of non-Cr(VI) Cr-containing materials suspended in water during ozonation, is presented within the context of water treatment applications (Chapter 4). The results indicate that in situ formation of hazardous Cr(VI) is possible during aqueous ozonation. pH had a significant influence, since the decomposition products of aqueous O3, i.e. hydroxyl radicals that form at higher pH levels, were found to be predominantly responsible for Cr(VI) formation. Increased ozonation contact time, water temperature and solid loading also resulted in elevated Cr(VI) concentrations being formed. Occasionally these values exceeded the drinking water standard 50 ppb Cr(VI). The results therefore indicate the importance of removing suspended particulates from water prior to ozonation. Additionally, pH-control could be used to mitigate the possible formation of Cr(VI) during ozonation. In Chapter 5, exploratory work is presented on the possibility of utilising Cr(VI) formation via ozonation as a means of recovering chromium from Cr-containing waste materials. Such a study is of particular interest within the local context, considering the large volumes of waste produced by the Cr-related industry in South Africa. This exploratory work is based on the fact that unlike Cr(0) and Cr(III), most Cr(VI) compounds are relatively soluble in water. Cr(VI) is a carcinogen if inhaled, however the probability of negative health effects are substantially reduced if it occurs in solution. Thus a hydrometallurgical route of recovering Cr-units via Cr(VI) generation represents the safest route with regard to Cr(VI) exposure. Such a hydrometallurgical route could also addresses the limitations of the physical separation methods currently applied, which fails to recover fine Cr-containing solids. The degree of Cr2O3-liberation achieved in this exploratory work was relatively low. However, the Cr2O3-liberation achieved for the ferrochromium slag (15%) indicated some promise, considering the limitations of this exploratory work. Several steps can be considered in future studies, which would in all likelihood improve the Cr2O3-liberation further. / Thesis (MSc (Chemistry))--North-West University, Potchefstroom Campus, 2012

Ozonation, or advanced oxidation processes (utilising ozone decomposition products as oxidants) are widely used in industrial waste water and drinking water treatment plants. In these applications the use of ozone is based on ozone and its decomposition by-products being strong oxidants. A case study revealed that several waterworks in South Africa successfully utilise ozone as a pre-oxidant for the treatment of raw waters. South Africa holds more than three quarters of the world’s viable chromium ore (chromite) reserves. Subsequently the Cr-related industry-within is considerable in size and a major producer of large volumes of waste materials. Chromium also occurs commonly in other industrial waste materials (e.g. fly ash and clinkers originating from coal combustion) and is a natural occurring element in natural sediments, since chromium is the 21st most abundant element in the earth’s crust with an average concentration of approximately 100 ppm. Considering the abundance of natural and anthropogenic Cr-containing materials in South Africa the possibility exists that some of these materials might be suspended in raw water entering water treatment facilities. In this dissertation, the possible oxidation of non-Cr(VI) Cr-containing materials suspended in water during ozonation, is presented within the context of water treatment applications (Chapter 4). The results indicate that in situ formation of hazardous Cr(VI) is possible during aqueous ozonation. pH had a significant influence, since the decomposition products of aqueous O3, i.e. hydroxyl radicals that form at higher pH levels, were found to be predominantly responsible for Cr(VI) formation. Increased ozonation contact time, water temperature and solid loading also resulted in elevated Cr(VI) concentrations being formed. Occasionally these values exceeded the drinking water standard 50 ppb Cr(VI). The results therefore indicate the importance of removing suspended particulates from water prior to ozonation. Additionally, pH-control could be used to mitigate the possible formation of Cr(VI) during ozonation. In Chapter 5, exploratory work is presented on the possibility of utilising Cr(VI) formation via ozonation as a means of recovering chromium from Cr-containing waste materials. Such a study is of particular interest within the local context, considering the large volumes of waste produced by the Cr-related industry in South Africa. This exploratory work is based on the fact that unlike Cr(0) and Cr(III), most Cr(VI) compounds are relatively soluble in water. Cr(VI) is a carcinogen if inhaled, however the probability of negative health effects are substantially reduced if it occurs in solution. Thus a hydrometallurgical route of recovering Cr-units via Cr(VI) generation represents the safest route with regard to Cr(VI) exposure. Such a hydrometallurgical route could also addresses the limitations of the physical separation methods currently applied, which fails to recover fine Cr-containing solids. The degree of Cr2O3-liberation achieved in this exploratory work was relatively low. However, the Cr2O3-liberation achieved for the ferrochromium slag (15%) indicated some promise, considering the limitations of this exploratory work. Several steps can be considered in future studies, which would in all likelihood improve the Cr2O3-liberation further. / Thesis (MSc (Chemistry))--North-West University, Potchefstroom Campus, 2012

Studies were undertaken to investigate the suitability of several molecular and physiological responses as biomarkers of UV-B exposure in several marine macroalgal species. Investigations into the sensitivity of mature plants and the reproductive unicells were also carried out. Furthermore, experiments were conducted to determine the interaction between UV-B radiation and the antifouling compound Irgarol 1051 in both a fouling alga and two non-target algal species. Chlorophyll fluorescence, in vivo thallus absorptance and ion leakage were investigated for their suitability as physiological biomarkers of UV -B exposure in the intertidal alga Enteromorpha intestinalis and the subtidal alga Palmaria palmata. DNA damage (measured by Random Amplification Polymorphic DNA fingerprinting, RAPD) and the cellular stress response (measured by induction of the heat shock 70 protein, HSP 70) were evaluated as molecular biomarkers of UV-B exposure. Measurements of thallus growth were used as a measure of adverse biological effects. Fv/Fm ratio showed potential as a sensitive, nonspecific general biomarker of UV-B exposure in both E. intestinalis and P. palmata. In vivo absorptance at wavelengths corresponding to chlorophyll a, phycoerythrin and/or carotenoids, as well as phycoerythrobilin and phycocyanin decreased in a dose-response dependent manner with UV-B exposure. These changes were associated with decreases in growth rate in P. palmata. The RAPD technique used for measuring DNA damage, showed potential as a tool for assessing UV -induced toxicity. These results illustrated that utilising several responses from different levels of biological organisation offer greater possibilities for detecting UV-B induced effects than do single responses. Experiments with 12 h old reproductive unicells of E. intestinalis demonstrated that asexual zoospores were up to 6 times more sensitive to UV-B exposure than mature thalli (measured as variable fluorescence). After 1 hour exposure to elevated UV-B (equivalent to 27% ozone depletion) reproductive unicells experienced decreases in variable fluorescence, accompanied by a 50 % inhibition of germination success and 16.4 % reduction in growth rates. Moreover, consistent patterns of greater sensitivity in the sexual reproductive part of the life cycle compared to the asexual part of the life cycle emerged throughout the experiments. The interactive relationship between UV-B radiation and the s-triazine Irgarol 1051 was investigated in multi-factorial experiments. Inhibitions in optimal quantum yield of approximately 20% were found after exposure to UV-B or Irgarol 1051 (applied singly). When these two stressors were applied simultaneously, however, an additive effect resulting in further reductions of up to 19.6 % compared to a single treatment occurred. These decreases in Fv/Fm were accompanied by up to a 38.5 % reduction in growth rates. Simultaneous exposure of the same stressors to two non-target macroalgae, P. palmata and P. umbilicalis, revealed that these algae were less sensitive to Irgarol 1051 compared to E. intestinalis. However, similar additive effects measured as reductions in both Fv/Fm ratio and growth rates occurred after simultaneous exposure. These results underline the importance of investigating combination effects between UV-B radiation and xenobiotic compounds, if an under-estimation of the ecological implications of elevated UV-B exposure in the marine environment is to be avoided.

Thesis (Ph. D.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed February 6, 2008) Includes bibliographical references (p. 140-144).

Diss. (sammanfattning) Umeå : Univ., 2007. / Härtill 4 uppsatser.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references. Also available via the Internet.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references. Also available via the Internet.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.