M.Sc. / Heavy metals occur naturally in the environment and are found in varying levels in all ground and surface waters. Some heavy metals are essential elements for the normal metabolism of organisms, while others are non-essential and play no significant biological role. Anthropogenic activities do, however, cause an increased discharge of these metals into natural aquatic ecosystems. Aquatic organisms are exposed to unnaturally high levels of these metals. Fish are relatively sensitive to changes in their surrounding environment. Fish health may therefore reflect and give a good indication of the health status of a specific aquatic ecosystem. Early toxic effects of pollution may only be evident on cellular or tissue level before significant changes can be identified in fish behaviour or external appearance. Histological analysis appears to be a very sensitive parameter and is crucial in determining cellular changes that may occur in target organs, such as the liver. The liver is a detoxification organ and essential for both the metabolism and excretion of toxic substances in the body. Exposure to heavy metals may cause histological changes in the liver. Fish liver histology could therefore serve as a model for studying the interactions between environmental factors and hepatic structures and functions. In this study, the effect of two heavy metals, cadmium (Cd) and zinc (Zn), on the histology of the liver of the South African freshwater fish species, Oreochromis mossambicus, was investigated. The aim of this study was to determine the toxic effect of cadmium and zinc on the histology of the liver, by identifying significant histological changes in the liver tissue, after exposing the fish to two concentrations of a mixture of cadmium and zinc, over both short and long-term exposure periods. Seventy two, adult O. mossambicus specimens were selected for the study. Two experimental exposures were executed under controlled conditions by means of a flow-through system in an environmental room. For each of the two exposures, twenty-four fish were exposed to different concentrations of cadmium and zinc. The remaining twenty-four specimens were used as a control group. The two respective metal concentrations selected for each exposure were 5% and 10% concentrations of both cadmium and zinc calculated from known LC50 values for cadmium chloride and zinc chloride. Liver samples were fixated in 10% neutrally buffered formalin and prepared for light microscopy analysis using standard techniques for Haematoxylin and Eosin (H & E) and Periodic Acid Schiff (PAS) staining. The liver histology of all seventy two specimens - including the forty eight exposed specimens and twenty four control specimens - were analysed, compared and documented. Although histological analysis can provide a clear indication of the degree of damage caused in the tissue(s) or organ(s) of exposed specimens, the need arises to quantify the histological results in studies where the effects of the exposing substance(s) are compared, to illustrate the possible decrease or increase in histological changes over time or the effect of two different concentrations of the same exposure substance on the histology of the liver. The histological results in this study were quantified in terms of a histological index. An index value representing the specific histological characteristics of the liver was assigned to each individual specimen indicating either normal histological structure (index value of 0-2) or a possible pathological response (index value of 3-6). Histological changes were identified in specimens exposed for 12, 18, 24, and 96 hours to both the 5% and 10% concentrations of cadmium and zinc, indicating a toxic response after the short-term metal exposures. Similar histological changes were identified in both the 5% and 10% exposed livers. These histological changes included hyalnization, vacuolation, cellular swelling and congestion of blood vessels. The liver histology of fish exposed over a long-term period of 672 hours, did, however, appear relatively normal in both the 5% and 10% exposure groups, indicating an adaptative, regenerative response. According to the results obtained, it was clear that exposure period did influence the degree of histological changes identified. The two metal concentrations did however seem to have similar histological effects and no definite variation could be identified in terms of 5% and 10% metal concentrations used. It can therefore be concluded that low concentrations of cadmium and zinc exposure caused histological alterations in the livers of exposed specimens and therefore allows the liver of O. mossambicus to be used as a biomarker of prior exposure to cadmium and zinc. / Dr. G.M. Pieterse

M.Sc. / Please refer to full text to view abstract

Les nanoparticules exposent beaucoup de propriétés uniques en comparaison de la possession de matériels (matières) en gros (vrac) à leur haute surface au ratio de volume. Des nanoparticules de sélénium élémentaires exposent aussi les nouvelles propriétés qui sont exploitées dans la formation de cellules solaires, des redresseurs de semi-conducteur et le déplacement (déménagement) de mercure et le cuivre. Cependant, la synthèse chimique de nanoparticules de sélénium élémentaires est coûteuse, exige des équipements spécialisés et utilise des produits chimiques toxiques. D'autre part, la production biologique de nanoparticules de sélénium élémentaires (BioSeNPs) peut être un remplacement(remplaçant) vert pour les chimiquement produits. BioSeNPs sont produit par la réduction microbienne de sélénite et selenate. La source du sélénium oxyanions peut être le wastewaters, où la réduction microbienne est employée comme une technologie de remédiation pour le déplacement (déménagement) de sélénium (...) / Nanoparticles exhibit many unique properties as compared to the bulk materials owning to their high surface to volume ratio. Elemental selenium nanoparticles also exhibit novel properties that are exploited in formation of solar cells, semiconductor rectifiers and removal of mercury and copper. However, the chemical synthesis of elemental selenium nanoparticles is costly, requires specialized equipments and uses toxic chemicals. On the other hand, biological production of elemental selenium nanoparticles (BioSeNPs) can be a green replacement for the chemically produced ones.BioSeNPs are produced by microbial reduction of selenite and selenate. The source of the selenium oxyanions can be the wastewaters, where microbial reduction is employed as a remediation technology for the removal of selenium. The formed BioSeNPs are colloidal poly-disperse particles with negative surface charge and are present in the effluent of the microbial reactor. However, the properties of these BioSeNPs are not very well understood. This knowledge would help us to produce better quality selenium nanomaterials, exploit produced BioSeNPs in the wastewater treatment and control the fate of these BioSeNPs in the microbial reactors. The characterization of BioSeNPs revealed the presence of the extracellular polymeric substances (EPS) on the surface of BioSeNPs. The EPS was identified to control the surface charge and to some extent the shape of the BioSeNPs. It was also found that the microbial reduction at 55 and 65 °C can lead to the formation of selenium nanowires as compared to nanospheres when the reduction takes place at 30 °C. These selenium nanowires are present in trigonal crystalline structure and are colloidal suspension, unlike the chemically formed trigonal selenium nanorods. This colloidal nature is due to negative ζ-potential values owning to the presence of EPS on the surface of biogenic selenium nanowires. Since proteins are a major component present in the EPS, the presence of various proteins on the surface of BioSeNPs was determined. The interaction of the various amino acids with the BioSeNPs was also evaluated.The interaction of heavy metals and BioSeNPs was studied with a view of developing a technology where BioSeNPs present in the effluent of an upflow anaerobic sludge blanket (UASB) reactor are mixed with heavy metals containing wastewater leading to removal of both BioSeNPs and heavy metals. It was found that Cu, Cd and Zn can be effectively adsorbed onto BioSeNPs. Cu was 4.7 times preferentially adsorbed onto BioSeNPs. The interaction of BioSeNPs with the heavy metals led to less negative ζ-potential of BioSeNPs loaded with heavy metals and thus better settling of BioSeNPs was achieved. The presence of BioSeNPs in the effluent of the microbial reactor treating selenium oxyanions containing wastewaters is undesirable due to higher total selenium concentrations. Thus, the attempts to capture of these BioSeNPs in the biomass/bioreactors were made. The activated sludge reactor system was investigated to aerobically reduce selenite to BioSeNPs and trap them in the activated sludge flocs. Around 80% of the fed selenium was trapped in the biomass. Sequential extraction revealed that the trapped selenium is BioSeNPs. The trapping of BioSeNPs in the sludge improved the settleability and hydrophilicity of the activated sludge flocs. When the UASB reactor were operated under mesophilic and thermophilic conditions, the total selenium concentration in the effluent under thermophilic conditions were lower than that of observed in mesophilic conditions suggesting better trapping of BioSeNPs.Keywords: Selenium, bioreduction, BioSeNPs, EPS, ζ-potential, heavy metals, activated sludge, UASB reactors, thermophilic

Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Numerous workers studied the impact of pollutants and agricultural chemicals, containing heavy metals such as copper (Cu), on soil microbes. It was found that elevated soil Cu levels do have a detrimental effect on soil bacterial populations however the filamentous fungi seemed to be less affected. Most of these studies were conducted in soils containing already relatively high Cu levels and the effect of this heavy metal on the nonfilamentous fungi (i.e. yeasts) was never investigated. The aim of this study was therefore to determine the impact of elevated Cu levels on filamentous fungi and yeasts occurring in soils containing relatively low natural Cu levels. A synthetic selective medium containing glucose as carbon source, thymine as nitrogen source, vitamins, minerals and chloramphenicol as anti-bacterial agent (TMV-agar), was used to enumerate ascomycetous and basidiomycetous Cu resistant yeasts in a sample of virgin soil containing ~ 2ppm Cu. Media that were used to enumerate Cu resistant filamentous fungi were malt extract agar, malt extract agar with streptomycin sulfate, maltyeast- extract-peptone agar with chloramphenicol and streptomycin sulfate, benomyl–dichloran-streptomycin medium for the enumeration of hymenomycetous fungi and two selective media for the isolation of mucoralean fungi. Cu resistant fungi able to grow on all of the above mentioned solid media supplemented with 32 ppm Cu occurred in the soil sample. To obtain an indication of the level of Cu tolerance of fungi present in this soil sample, a number of fungal isolates were screened for the ability to grow on a series of agar plates, prepared from glucose-glutamate-yeast extract agar, containing increasing concentrations of Cu. It was found that filamentous fungi and yeasts that were able to grow on this agar medium containing up to 100 ppm Cu were present in the soil. A series of soil microcosms was subsequently prepared from the soil sample by experimentally contaminating the soil with increasing amounts of copper oxychloride, were after fungal populations in the microcosms, including Cu resistant fungi, were monitored using plate counts. At the end of the incubation period, after 245 days, fungal biomass in the microcosms was compared by determining the concentrations of the fungal sterol, ergosterol, inthe soil. Generally, Cu had little impact on the numbers of filamentous fungal colony forming units on the plates, as well as on the ergosterol content of the soil. The numbers of filamentous fungi in the soil, including the Mucorales and hymenomycetes, seemed to be less affected by the addition of copper oxychloride than the numbers of soil yeasts able to grow on TMV-agar. The focus of the next chapter was on the response of yeasts in different soils to elevated levels of Cu in the soil. TMV-agar was used to enumerate yeasts in soil microcosms prepared from four different soil samples, which were experimentally treated with copper oxychloride resulting in Cu concentrations of up to 1000 ppm. The selective medium supplemented with 32 ppm Cu was used to enumerate Cu resistant yeasts in the microcosms. The results showed that the addition of Cu at concentrations ≥ ~1000 ppm did not have a significant effect on total yeast numbers in the soil. Furthermore, it was found that Cu resistant yeasts were present in all the soil samples regardless of the amount of Cu that the soil was challenged with. At the end of the incubation period, yeasts in the microcosms with zero and ~1000 ppm additional Cu were enumerated, isolated and identified using sequence analyses of the D1/D2 600-650bp region of the large subunit of ribosomal DNA. Hymenomycetous species dominated in the control soil, while higher numbers of the urediniomycetous species were found in the soil that received Cu. These observations suggest that urediniomycetous yeasts may play an important role in re-establishing overall microbial activity in soils following perturbations such as the addition of Cu-based fungicides. / AFRIKAANSE OPSOMMING: Vele navorsers het al die impak van besoedelingstowwe en landbouchemikalieë wat swaarmetale soos koper (Cu) bevat, op grond-mikrobes bestudeer. Dit is gevind dat verhoogde Cu vlakke ‘n nadelige effek het op grond-bakteriese populasies, maar dat die filamentagtige fungi geneig is om minder geaffekteer te word. Meeste van hierdie studies is gedoen met gronde wat alreeds relatief hoë Cu vlakke bevat het en die effek van hierdie swaarmetaal op die nie-filamentagtige fungi (d.i. giste) is nooit ondersoek nie. Die doel van hierdie studie was dus om die impak van verhoogde Cu vlakke op filamentagtige fungi en giste in gronde, wat natuurlike lae vlakke van Cu bevat, te bepaal. ‘n Sintetiese selektiewe medium wat glukose as koolstofbron, timien as stikstofbron, vitamiene, minerale asook chloramfenikol as anti-bakteriese agent bevat (TMV-agar), is gebruik om askomisete en basidiomisete Cu weerstandbiedende giste in ‘n monster ongeskonde grond, bevattende ~ 2dpm Cu, te tel. Media wat gebruik is om Cu weerstandbiedende filamentagtige fungi te tel, was mout-ekstrak agar, moutekstrak agar met streptomisiensulfaat, benomiel-dichloran-streptomisien medium vir die tel van hiemenomiseetagtige fungi en twee media vir die isolasie van mukoraliese fungi. Cu-weerstandbiedende fungi wat op al die bogenoemde media, aangevul met 32 dpm Cu, kon groei, het in die grondmonster voorgekom. Om die mate van Cu-weerstandbiedendheid van fungi wat in die grondmonster voorkom, te bepaal, is ‘n getal fungus-isolate op agarplate, voorberei met glukose-glutamaat-gis ekstrak agar, bevattende verhoogde konsentrasies Cu, nagegaan. Daar is gevind dat daar filamentagtige fungi en giste in die grond voorkom wat die vermoë het om op media bevattende 100 dpm Cu te groei. ‘n Reeks grond mikrokosmosse is dus voorberei vanaf die grondmonster deur om dit eksperimenteel te kontamineer met verhoogde hoeveelhede koper oksichloried, waarna die fungus-populasies asook die Cu-weerstandbiedende fungi in die mikrokosmos gemoniteer is deur middel van plaattellings. Aan die einde van die inkubasie periode, 245 dae, is die fungus biomassa in al die mikrokosmosse bereken deur die konsentrasie van die fungus sterool ergosterool te bepaal en dit met mekaar te vergelyk. Oor die algemeen het Cu min impak ten opsigte van diegetal filamentagtige fungi kolonie vormende eenhede die plate, asook op die ergosterool inhoud van die grond gehad. Dit wil voorkom of die getal filamentagtige fungi in die grond, insluitende die Mucorales en die hymenomisete, minder geaffekteer is deur die toediening van koperoksichloried as die aantal grondgiste wat op die TMV-agar kan groei. Die fokus van die volgende hoofstuk was dus op die reaksie wat giste in verskillende grondtipes gehad het op verhoogde Cu in die grond. TMV-agar is gebruik om die getal giste te bepaal in die grond mikrokosmosse van die vier verskillende grondmonsters, wat voorberei is deur om dit eksperimenteel met koper oksikloried te kontamineer tot en met Cu konsentrasies van 1000 dpm. Die selektiewe medium wat gesupplementeer is met 32 dpm Cu, is gebruik om Cu weerstandbiedende giste in die mikrokosmosse te bepaal. Die resultate toon dat die toevoeging van Cu by konsentrasies ≥ ~1000 dpm nie enige beduidende effek op die totale gis getalle gehad het nie. Daar is ook gevind dat daar Cu weerstandbiedende giste in die grond monsters voorkom gekom het ten spyte van die hoeveelheid Cu wat tot die grond toegevoeg is. Aan die einde van die inkubasie periode is die giste wat die die mikrokosmosse bevattende nul en ~1000 dpm Cu getel, geïsoleer en geïdentifiseer deur gebruik te maak van DNA volgorde bepaling van die D1/D2 600-650 bp areas geleë in die groter subeenheid van die ribosonale DNA. Hymenomisete spesies het in die grond kontrole gedomineer, terwyl hoër getalle uredinomisete spesies in die grond met addisionele Cu gevind is. Die resultate dui daarop dat uredinomisete giste dalk ‘n belangrike rol kan speel in die hervestiging van die oorwegende mikrobiese aktiwiteit in grond na skoktoestande soos die aanwending van Cu-gebaseerde fungisiede.

by Li Ka Ling. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 221-242). / Text in English; abstracts in English and Chinese. / by Li Ka Ling. / Acknowledgements --- p.i / Abstract --- p.ii / Contents --- p.vi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Literature review --- p.1 / Chapter 1.1.1 --- Heavy metals in our environment --- p.1 / Chapter 1.1.2 --- Major source of metal pollution in Hong Kong --- p.2 / Chapter 1.1.3 --- Chemistry and toxicity of copper ion --- p.9 / Chapter 1.1.4 --- Removal of metal ions from effluents by precipitation --- p.12 / Chapter 1.1.4.1 --- Metal ions in solution --- p.12 / Chapter 1.1.4.2 --- Precipitation of metal ions --- p.13 / Chapter 1.1.4.3 --- pH adjustment reagents --- p.15 / Chapter 1.1.4.4 --- Precipitation of complexed metal ions --- p.19 / Chapter 1.1.5 --- Other physico-chemical methods for the removal of metal ions --- p.21 / Chapter 1.1.6 --- Removal of metal ions by microorganisms --- p.24 / Chapter 1.1.6.1 --- Biosorption --- p.24 / Chapter 1.1.6.2 --- Other mechanisms for the accumulation of metal ions --- p.28 / Chapter 1.1.6.3 --- An attractive alternative for the removal and recovery of metal ions:biosorption --- p.30 / Chapter 1.1.7 --- Factors affecting biosorption --- p.37 / Chapter 1.1.7.1 --- Culture conditions --- p.38 / Chapter 1.1.7.2 --- pH of solution --- p.39 / Chapter 1.1.7.3 --- Concentration of biosorbent --- p.41 / Chapter 1.1.7.4 --- Initial metal ion concentration --- p.42 / Chapter 1.1.7.5 --- Presence of other cations --- p.43 / Chapter 1.1.7.6 --- Presence of anions --- p.45 / Chapter 1.1.8 --- Properties and uses of magnetite --- p.46 / Chapter 1.1.8.1 --- Physical and chemical properties of magnetite --- p.46 / Chapter 1.1.8.2 --- Use of magnetite for wastewater treatment --- p.48 / Chapter 1.1.8.3 --- Immobilization of cells on magnetite for metal ion removal --- p.49 / Chapter 1.2 --- Objectives of the present study --- p.54 / Chapter 2. --- Materials and methods --- p.57 / Chapter 2.1 --- Effects of physico-chemical factors on the precipitation of Cu2+ --- p.57 / Chapter 2.1.1 --- Reagents and chemicals --- p.57 / Chapter 2.1.2 --- Effects of equilibrium time --- p.59 / Chapter 2.1.3 --- Effects of pH --- p.60 / Chapter 2.1.4 --- Presence of anions and other cations --- p.61 / Chapter 2.1.5 --- "Presence of chelating agent, EDTA" --- p.61 / Chapter 2.2 --- Dissolution of metal sludge --- p.63 / Chapter 2.2.1 --- Dewatering and drying of metal sludge --- p.63 / Chapter 2.2.2 --- Dissolving of metal sludge by sulfuric acid --- p.63 / Chapter 2.3 --- Culture of biomass --- p.65 / Chapter 2.3.1 --- Subculturing of the biomass --- p.65 / Chapter 2.3.2 --- Culture media --- p.66 / Chapter 2.3.3 --- Growth and preparation of the cell suspension --- p.66 / Chapter 2.4 --- Immobilization of the bacterial cells on magnetites --- p.66 / Chapter 2.5 --- Metal ion removal studies --- p.71 / Chapter 2.5.1 --- Preparation of concentrated Cu2+ solutions --- p.71 / Chapter 2.5.2 --- Removal of Cu2+ in the concentrated Cu2+ solutions by magnetite- immobilized cells --- p.74 / Chapter 2.5.3 --- Effects of EDTA --- p.76 / Chapter 2.5.4 --- Effects of anions --- p.77 / Chapter 2.5.5 --- Effects of other cations --- p.78 / Chapter 2.6 --- Maximum removal efficiency of Cu2+ by magnetite-immobilized cells --- p.79 / Chapter 2.7 --- Recovery of adsorbed Cu2+ from magnetite-immobilized cell --- p.79 / Chapter 2.7.1 --- Desorption of Cu2+ from the immobilized cells using sulfuric acid --- p.79 / Chapter 2.7.2 --- Multiple adsorption-desorption cycles --- p.80 / Chapter 2.8 --- Treatment of electroplating effluent by magnetite-immobilized cells --- p.80 / Chapter 2.8.1 --- Removal and recovery of Cu2+ from electroplating effluent collected from rinsing baths --- p.80 / Chapter 2.8.2 --- Removal and recovery of Cu2+ from electroplating effluent collected from final collecting tank --- p.83 / Chapter 2.9 --- Data analysis --- p.84 / Chapter 3. --- Results --- p.86 / Chapter 3.1 --- Effects of physical-chemical factors on the precipitation of Cu2+ --- p.86 / Chapter 3.1.1 --- Effects of equilibrium time --- p.86 / Chapter 3.1.2 --- Effects of pH --- p.86 / Chapter 3.1.3 --- Presence of anions --- p.89 / Chapter 3.1.3.1 --- Cu2+-S042- systems --- p.89 / Chapter 3.1.3.2 --- Cu2+-Cl- systems --- p.89 / Chapter 3.1.3.3 --- Cu2+-Cr2072- systems --- p.89 / Chapter 3.1.3.4 --- Cu2+-mixed anions systems --- p.93 / Chapter 3.1.4 --- Presence of other cations --- p.93 / Chapter 3.1.4.1 --- Cu2+-Ni2+ systems --- p.93 / Chapter 3.1.4.2 --- Cu2+-Zn2+ systems --- p.96 / Chapter 3.1.4.3 --- Cu2+-Cr6+ systems --- p.96 / Chapter 3.1.4.4 --- Cu2+-mixed cations systems --- p.99 / Chapter 3.1.5 --- "Presence of chelating agent, EDTA" --- p.99 / Chapter 3.1.5.1 --- Cu2+-EDTA4 -mixed anions systems --- p.102 / Chapter 3.1.5.2 --- Cu2+-EDTA4--mixed cations systems --- p.102 / Chapter 3.2 --- Dissolution of metal sludge --- p.105 / Chapter 3.2.1 --- Dewatering and drying of metal sludge --- p.105 / Chapter 3.2.2 --- Dissolving of metal sludge by sulfuric acid --- p.105 / Chapter 3.3 --- Removal of Cu2+ in the concentrated Cu2+ solution by magnetite- immobilized cells --- p.109 / Chapter 3.4 --- Effects of EDTA on removal and recovery of Cu2+ by magnetite- immobilized cells --- p.109 / Chapter 3.4.1 --- Effects of EDTA --- p.109 / Chapter 3.4.2 --- Effects of EDTA after precipitation --- p.112 / Chapter 3.5 --- Effects of anions on removal and recovery of Cu2+ by magnetite- immobilized cells --- p.120 / Chapter 3.5.1 --- Effects of anions --- p.120 / Chapter 3.5.2 --- Effects of anions after precipitation --- p.120 / Chapter 3.5.3 --- Effects of anions in the presence of EDTA after precipitation --- p.124 / Chapter 3.6 --- Effects of other cations on removal and recovery of Cu2+ by magnetite-immobilized cells --- p.129 / Chapter 3.6.1 --- Effects of other cations --- p.129 / Chapter 3.6.2 --- Effects of other cations after precipitation --- p.137 / Chapter 3.6.3 --- Effects of other cations in the presence of EDTA after precipitation --- p.137 / Chapter 3.7 --- Maximum removal efficiency of Cu2+ by magnetite-immobilized cells --- p.142 / Chapter 3.8 --- Multiple adsorption-desorption cycle --- p.148 / Chapter 3.9 --- Treatment of electroplating effluent by magnetite-immobilized cells --- p.148 / Chapter 3.9.1 --- Removal and recovery of Cu2+ from electroplating effluent collected from rinsing baths --- p.148 / Chapter 3.9.2 --- Removal and recovery of Cu2+ from electroplating effluent collected from final collecting tank --- p.158 / Chapter 4. --- Discussion --- p.167 / Chapter 4.1 --- Effects of physical-chemical factors on the precipitation of Cu2+ --- p.167 / Chapter 4.1.1 --- Effects of equilibrium time --- p.167 / Chapter 4.1.2 --- Effects of pH --- p.168 / Chapter 4.1.3 --- Presence of anions --- p.169 / Chapter 4.1.4 --- Presence of other cations --- p.170 / Chapter 4.1.5 --- "Presence of chelating agent, EDTA" --- p.171 / Chapter 4.1.5.1 --- Presence of EDTA with anions --- p.174 / Chapter 4.1.5.2 --- Presence of EDTA with other cations --- p.174 / Chapter 4.2 --- Dissolution of metal sludge --- p.175 / Chapter 4.2.1 --- Dewatering and drying of metal sludge --- p.175 / Chapter 4.2.2 --- Dissolving of metal sludge by sulfuric acid --- p.175 / Chapter 4.3 --- Metal ion removal studies --- p.176 / Chapter 4.3.1 --- Selection of biomass --- p.176 / Chapter 4.3.2 --- Removal of Cu2+ in the concentrated Cu2+ solution by magnetite- immobilized cells --- p.178 / Chapter 4.4 --- Effects of EDTA on removal and recovery of Cu2+ by magnetite- immobilized cells --- p.182 / Chapter 4.4.1 --- Effects of EDTA --- p.182 / Chapter 4.4.2 --- Effects of EDTA after precipitation --- p.184 / Chapter 4.5 --- Effects of anions on removal and recovery of Cu2+ by magnetite- immobilized cells --- p.185 / Chapter 4.5.1 --- Effects of anions --- p.185 / Chapter 4.5.2 --- Effects of anions after precipitation --- p.188 / Chapter 4.5.3 --- Effects of anions in the presence of EDTA after precipitation --- p.190 / Chapter 4.6 --- Effects of other cations on removal and recovery of Cu2+ by magnetite-immobilized cells --- p.192 / Chapter 4.6.1 --- Effects of other cations --- p.192 / Chapter 4.6.2 --- Effects of other cations after precipitation --- p.195 / Chapter 4.6.3 --- Effects of other cations in the presence of EDTA after precipitation --- p.197 / Chapter 4.7 --- Maximum removal efficiency of Cu2+ by magnetite-immobilized cells --- p.198 / Chapter 4.8 --- Multiple adsorption-desorption cycles --- p.199 / Chapter 4.9 --- Treatment of electroplating effluent by magnetite-immobilized cells --- p.202 / Chapter 4.9.1 --- Removal and recovery of Cu2+ from electroplating effluent collected from rinsing baths --- p.202 / Chapter 4.9.2 --- Removal and recovery of Cu2+ from electroplating effluent collected from final collecting tank --- p.205 / Chapter 5. --- Conclusion --- p.213 / Chapter 6. --- Summary --- p.215 / Chapter 7. --- Recommendations --- p.219 / Chapter 8. --- References --- p.221

Excessive release of metals and metalloids into the environment is a major global environmental concern and there is need for environmentally friendly and cost effective methods for their removal. The present study investigated the adsorptive removal of zinc, lead, copper and nickel ions from synthetic aqueous solutions and various metals from three acid mine drainage (AMD) sites using chicken eggshells. Process parameters including the initial metal concentration were evaluated and the optimum conditions obtained were pH 7, adsorbent dose of 7 g and contact time of 360 minutes (for the removal of 100ppm metal ions). Under these conditions the percentage adsorptions were; 97% for lead, 95% for copper, 94% for nickel and 80% for zinc. Aluminium, iron, potassium, nickel and zinc ions all had percentage adsorptions above 75% in AMD Sample 1. Potassium had a 98.78% adsorption while magnesium, strontium and zinc had 72.33; 68.75 and 53.07% adsorption respectively in Sample 2. Arsenic, chromium, copper, iron, antimony and tellurium ions were above 75% for Sample 3. The study demonstrated the efficacy of chicken eggshells and presents it as a viable low-cost adsorbent for bioremediation. / Environmental Science / M. Sc. (Environmental Science)

The present study was carried out to determine the levels of heavy metals, Arsenic (As), Chromium (Cr), Cadmium (Cd) and Lead (Pb) in samples of water, sediments, and specimens from sheep known to graze and drink from Wonderfontein stream around the Khutsong area in the North West Province of South Africa. Determination of heavy metal levels was carried out using Atomic Absorption Spectrophotometer. Abundance of metals in water samples followed the trend As>Pb>Cd>Cr, while that in sediments followed the trend: Pb>As>Cr>Cd. Faecal levels were highest for Cr, followed by Cd, As then Pb, while serum levels were highest for As, Cd Cr and then Pb. The metal concentration in liver, kidney and muscle showed the following trends respectively: As>Cd>Cr>Pb ; As>Pb>Cd>Pb and As>Cd >Cr> Pb. The liver, kidney and muscle samples had higher concentration of As compared to other heavy metals. Generally, most samples showed a higher concentration in As. The mean concentrations of heavy metals in ppm were compared with European Commission Regulation, World Health Organisation, Korean Soil Environmental Conservation Act and the Australian New Zealand Food Standards maximum acceptable levels. The metal levels generally tended to be higher than the permissible levels and thus, public health risks. A survey conducted also revealed that the community in Khutsong does not have the knowledge on environmental contamination due to mining effluents and the effects thereof. The varying levels of water and sheep specimen contamination with As, Cd, Cr and Pb revealed in this study imply public health risks. Further biomonitoring, public and animal health studies are therefore indicated in this area. / Thesis (Msc in Agric Animal Health) North-West University, Mafikeng Campus, 2012

Estuaries are among the most productive and diverse of aquatic habitats supporting a rich variety of plants and animals. They are nursery areas for many species of fish harvested by recreational and subsistence anglers. The Swartkops River Estuary (SRE) is situated approximately 10 km north-east of Port Elizabeth and the only major well-preserved estuary within a city, thus unique to South Africa. The SRE is surrounded by highly urbanized and industrialized regions in the Eastern Cape. The aim of this study was to determine and interpret the presence, levels, and distribution of selected priority pollutants in the food web of the SRE. Different components within the SRE were analysed for the presence of environmental contaminants. Seven sites were selected, some coinciding with previous studies in the SRE. Three of these sites are major discharge points that discharge directly into the estuary. Sediment, mud prawn, sand gobies, bird eggs, and various fish species were analysed. Samples were collected in the middle and lower reaches of the estuary, the areas known to receive major pollution loads from neighbouring sources. Heavy metals found in the sediments were compared to previous studies. Bottom sediments and organisms surrounding major discharge points showed higher concentrations of pollutants and compared to previous studies, these concentrations seem to be increasing. Due to biomagnification, higher concentrations were generally found in the top predators although certain elements did not show this trend. Some heavy metal concentrations found in the fish exceeded of the food guidelines and may in turn pose a threat for subsistence users of the SRE. There are indications of multiple different pollution sources. Bird eggs had detectable quantities of polychlorinated biphenyls, but its implications need more investigation. / MSc (Zoology), North-West University, Potchefstroom Campus, 2014

Estuaries are among the most productive and diverse of aquatic habitats supporting a rich variety of plants and animals. They are nursery areas for many species of fish harvested by recreational and subsistence anglers. The Swartkops River Estuary (SRE) is situated approximately 10 km north-east of Port Elizabeth and the only major well-preserved estuary within a city, thus unique to South Africa. The SRE is surrounded by highly urbanized and industrialized regions in the Eastern Cape. The aim of this study was to determine and interpret the presence, levels, and distribution of selected priority pollutants in the food web of the SRE. Different components within the SRE were analysed for the presence of environmental contaminants. Seven sites were selected, some coinciding with previous studies in the SRE. Three of these sites are major discharge points that discharge directly into the estuary. Sediment, mud prawn, sand gobies, bird eggs, and various fish species were analysed. Samples were collected in the middle and lower reaches of the estuary, the areas known to receive major pollution loads from neighbouring sources. Heavy metals found in the sediments were compared to previous studies. Bottom sediments and organisms surrounding major discharge points showed higher concentrations of pollutants and compared to previous studies, these concentrations seem to be increasing. Due to biomagnification, higher concentrations were generally found in the top predators although certain elements did not show this trend. Some heavy metal concentrations found in the fish exceeded of the food guidelines and may in turn pose a threat for subsistence users of the SRE. There are indications of multiple different pollution sources. Bird eggs had detectable quantities of polychlorinated biphenyls, but its implications need more investigation. / MSc (Zoology), North-West University, Potchefstroom Campus, 2014

Thesis (M. Tech.: Biotechnology)-Dept. of Biotechnology and Food Technology, Durban University of Technology, 2008. xiv, 103 leaves : ill. / Phytoremediation is an emerging technology where specially selected and engineered metal-accumulating plants are used for bioremediation. Amaranthus dubius (marog or wild spinach) is a popular nutritious leafy vegetable crop which is widespread especially in the continents of Africa, Asia and South America. Their rapid growth and great biomass makes them some of the highest yielding leafy crops which may be beneficial for phytoremediation. This study was undertaken to evaluate the potential of A. dubius for the phytoremediation of Chromium (Cr), Mercury (Hg), Arsenic (As), Lead (Pb), Copper (Cu) and Nickel (Ni). Locally gathered soil and plants of A. dubius were investigated for the metals from a regularly cultivated area, a landfill site and a sewage site. Metals were extracted from the samples using microwave-digestion and analyzed using Inductively Coupled Plasma – Mass Spectroscopy (ICP-MS). Further experiments were conducted with plants from locally collected seeds of A. dubius, in a tunnel house under controlled conditions. The mode of phytoremediation, the effect of the metals on the plants, the ability of the plant to extract metals from soil (Bioconcentration Factor - BCF), and the ability of the plants to move the metals to the aerial parts of the plants (Translocation Factor - TF) were evaluated for the different metals. Finally, A. dubius was micro-propagated in a tissue culture system with and without exposure to the metal, and the effect was studied by electron microscopy.