Thesis (Ph.D.)--University of Melbourne, Dept. of Earth Sciences, 2001. / Typescript (photocopy). Includes bibliographical references.

Thesis (M. Sc.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 75-77).

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

M.Sc. / Atmospheric emissions of dust and chemicals from gold mine tailings are ongoing environmental management issues on the Witwatersrand, where residential areas have developed in proximity to dumps. Residual amounts of cyanide, used as a chemical in the gold extraction process, are deposited with the mineral tailings. This study deals with the evaluation of population exposure to cyanide vapour emitted from gold mine tailings dams, an issue of environmental impact and public health concern. The first part of this study deals with the determination of the emission factors of cyanide vapour from three selected gold mine tailings dams: one under reclamation; one no longer operational; and one fully operational as a slimes deposition site. These three sites are located in the Boksburg area of the Ekurhuleni Metropolitan Municipality. Twelve samples were collected in all: six from the Cason (2628AAL91) mine dump (under reclamation in 2006); four from the ERPM tailings complex [comprising the dormant deposits 4/L/47, 4/L/48, 4/L/49 and 4/L/50, which are north of the N17 national highway; and the 2628ACL1 deposit, which is south of the N17]; and two from the Rooikraal (active) deposition site. All samples were collected in the year 2006. In the second part of the study, the obtained emission factors were used in an Industrial Source Complex dispersion model to measure the degree of population exposure to cyanide vapour for communities that are in proximity to the operational gold mine tailings dams in the Johannesburg Metropolitan Municipality. In the third part, a health risk assessment was carried out for communities in proximity to the selected gold mine tailings dams. The study revealed the average flux (± std. dev.) of Cason to be (4.7 ± 0.8) x 10-7 g m-2 s-1, the average flux of ERPM (3.9 ± 0.6) x 10-7 g m-2 s-1, the average flux of Rooikraal (1.7 ± 0.2) x 10-5 g m-2 s-1. The concentrations of cyanide vapour emitted from the older tailings deposits (sand) that are under reclamation and the dormant slimes dams are very low (and pose little health risk to occupants of adjacent land). However, HCN emission factors from operational tailings dams, which are receiving continuous depositions, are 3 to 80 times higher than the emission factors from dormant mine tailings. Ambient cyanide concentrations near the active tailings deposits may sometimes exceed selected international health standards. The average hourly, daily and annual dispersion model calculations for the Nasrec tailings deposition sites in Johannesburg revealed that 117 938, 18 722 and 8 130 people respectively were exposed to hydrogen cyanide concentrations that were above international (Ontario, Canada) standards. This raises environmental concerns that require institution of cyanide monitoring and setting of emission limits applicable to South African legal and environmental circumstances. These conclusions are based on a small number of emission factor determinations and hence these findings should be regarded as provisional. Further testing and verification are required for emission factors from a larger number of dormant, reworked and active tailings dams.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016. / Anthropogenic activities that utilise cyanide in various chemical forms have resulted in the disposal of cyanide-contaminated effluents into drainage systems that ultimately reach wastewater treatment plants (WWTP), without prior treatment. Cyanides (CN) and soluble salts could potentially inhibit biological processes in WWTP, which are responsible for the removal of contaminants from incoming wastewaters. The removal of nitrogenous compounds from such waters in processes such as nitrification and denitrification is among the core biological processes used to treat wastewaters in WWTP. Electroplating and mining industries are among the perpetrators of cyanide contamination of WWTP. The presence of these hazardous contaminants results in the alteration of metabolic functions of the microbial populations that are utilised in WWTP, thus rendering the wastewater treatment process ineffective. In this study, bacterial isolates that were able to carry out nitrification and aerobic denitrification under high salinity cyanogenic conditions were isolated from poultry slaughterhouse effluent. These strains were referred to as I, H and G. The isolated bacterial species were found to be able to oxidise ammonium nitrogen (NH4-N) in the presence of free cyanide (CN-) under halophilic conditions. Isolates I, H and G were identified using the 16S rDNA gene and were identified to be Enterobacter sp., Yersinia sp. and Serratia sp., respectively. Furthermore, Response Surface Methodology was used to optimise the physicochemical conditions suitable for the proliferation of the isolates for free-cyanide degradation, nitrification and aerobic denitrification.

Thesis (M.P.H.)--University of Michigan, 1944. / Cover title: The effect of certain industrial wastes on anaerobic decomposition.

Thesis (M.P.H.)--University of Michigan, 1944. / Cover title: The effect of certain industrial wastes on anaerobic decomposition.

Thesis (DTech (Chemical Engineering))--Cape Peninsula University of Technology, 2017. / The high rate of industrialisation in most developing countries has brought about challenges of wastewater management especially in the mineral processing industry. Cyanide has been used in base metal extraction processes due to its lixiviant properties thus, its presence in wastewater generated is inevitable. Furthermore, partial and/or the use of unsuitable treatment methods for such wastewater is a potential hazard to both human and the environment. There are several reports on biotechnological treatments of cyanide containing wastewater but few mineral processing industries have adopted this approach. Hence, the thermodynamic study of biodegradation of cyanide containing wastewater was undertaken. The primary aim of this study was to explore the application of bioenergetic models and biological stoichiometry to determine the functionality and thermodynamic requirements for cyanide degrading isolate (Fusarium oxysporum EKT01/02), grown exclusively on Beta vulgaris, for a system designed for the bioremediation of cyanidation wastewater. Chapter 2 reviews some of the applicable thermodynamic parameters such as enthalpy, entropy, heat of combustion, heat capacity, Gibbs energy, including stoichiometry models in relation to their applicability for microbial proliferation in cyanidation wastewater. The chapter places emphasis on the application of agro-industrial waste as a suitable replacement for refined carbon sources for microbial proliferation in bioremediation systems because such systems are environmentally benign. The choice of using agro-industrial waste is due to organic waste properties, i.e. agro-industrial waste is rich in nutrients and is generated in large quantities. Chapter 3 presents the materials and various standardised methods used to address the research gaps identified in chapter 2. For an organism to degrade free cyanide in wastewater, it must be able to survive and perform its primary function in the presence of such a toxicant. Chapter 4 exemplifies both molecular and biochemical characteristics of Fusarium oxysporum EKT01/02 isolated from the rhizosphere of Zea mays contaminated with a cyanide based pesticide. The molecular analyses confirmed the fungal isolate to be Fusarium oxysporum EKT01/02 and the nucleotide sequence of the isolates were deposited with National Centre for Biotechnology Information (NCBI) with accession numbers KU985430 and KU985431. The biochemical analyses revealed a wide substrate utilisation mechanism of the isolate dominated by aminopeptidase including nitrate assimilation capabilities. A preliminary investigation showed free cyanide degradation efficiency of 77.6% (100 mg CN-/L) after 5 days by the isolate. The excess production of extracellular polymeric substance (EPS) was attributed to the isolates’ strive to protect itself from cyanide toxicity.

Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Chemical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology 2014 / Environmental legislation focusing on wastewater disposal in industries that utilise cyanide and/or cyanide-related compounds has become increasingly stringent worldwide, with many companies that utilise cyanide products required to abide by the Cyanide International Code associated with the approval of process certifications and management of industries which utilise cyanide. This code enforces the treatment or recycling of cyanide-contaminated wastewater. Industries such as those involved in mineral processing, photo finishing, metal plating, coal processing, synthetic fibre production, and extraction of precious metals, that is, gold and silver, contribute significantly to cyanide contamination in the environment through wastewater. As fresh water reserves throughout the world are low, cyanide contamination in water reserves threatens not only the economy, but also endangers the lives of living organisms that feed from these sources, including humans. In the mining industry, dilute cyanide solutions are utilised for the recovery of base (e.g. Cu, Zn, Ni, etc.) and precious metals (e.g. Au, Ag, etc.). However, for technical reasons, the water utilised for these processes cannot be recycled upstream of the mineral bioleaching circuit as the microorganisms employed in mineral bioleaching are sensitive to cyanide and its complexes, and thus the presence of such compounds would inhibit microbial activity, resulting in poor mineral oxidation. The inability to recycle the water has negative implications for water conservation and re-use, especially in arid regions. A number of treatment methods have been developed to remediate cyanide containing wastewaters. However, these chemical and physical methods are capital intensive and produce excess sludge which requires additional treatment. Furthermore, the by-products that are produced through these methods are hazardous. Therefore, there is a need for the development of alternative methods that are robust and economically viable for the bioremediation of cyanide-contaminated wastewater. Biological treatment of free cyanide in industrial wastewaters has been proved a viable and robust method for treatment of wastewaters containing cyanide. Several bacterial species, including Bacillus sp., can degrade cyanide to less toxic products, as these microorganisms are able to use the cyanide as a nitrogen source, producing ammonia and carbon dioxide. These bacterial species secrete enzymes that catalyse the degradation of cyanide into several end-products. The end-products of biodegradation can then be utilised by the microorganisms as nutrient sources. This study focused on the isolation and identification of bacterial species in wastewater containing elevated concentrations of cyanide, and the assessment of the cyanide biodegradation ability of the isolates. Thirteen bacterial isolates were isolated from electroplating wastewater by suppressing the growth of fungal organisms and these species were identified as species belonging to the Bacillus genus using the 16S rDNA gene. A mixed culture of the isolates was cultured in nutrient broth for 48 hours at 37°C, to which FCN as KCN was added to evaluate the species‟ ability to tolerate and biodegrade cyanide in batch bioreactors. Subsequently, cultures were supplemented solely with agro-waste extracts, that is, Ananas comosus extract (1% v/v), Beta vulgaris extract (1% v/v), Ipomea batatas extract (1% v/v), spent brewer‟s yeast (1% v/v) and whey (0.5% w/v), as the primary carbon sources. Owing to the formation of high ammonium concentration from the cyanide biodegradation process, the nitrification and aerobic denitrification ability of the isolates, classified as cyanide-degrading bacteria (CDB) was evaluated in a batch and pneumatic bioreactor in comparison with ammonia-oxidising bacteria (AOB). Furthermore, the effects of F-CN on the nitrification and aerobic denitrification was evaluated assess the impact of F-CN presence on nitrification. Additionally, optimisation of culture conditions with reference to temperature, pH and substrate concentration was evaluated using response surface methodology. Using the optimised data, a continuous biodegradation process was carried out in a dual-stage packed- bed reactor combined with a pneumatic bioreactor for the biodegradation of F-CN and subsequent nitrification and aerobic denitrification of the formed ammonium and nitrates. The isolated bacterial species were found to be gram positive and were able to produce endospores that were centrally located; using the 16S rDNA gene, the species were found to belong to the Bacillus genus. The species were able to degrade high cyanide concentration in nutrient broth with degradation efficiencies of 87.6%, 65.4%, 57.0% and 43.6% from 100 mg F-CN/L, 200 mg F-CN/L, 300 mg F-CN/L, 400 mg F-CN/L and 500 mg F-CN/L respectively over a period of 8 days. Additionally, the isolates were able to degrade cyanide in an agro-waste supported medium, especially in a medium that was supplemented with whey which achieved a degradation efficiency of 90% and 60% from 200 mg F-CN/L and 400 mg F-CN/L, respectively over a period of 5 days. The nitrification ability of the isolates was evaluated and the removal of NH4 +/NO3 - by the CDB and AOB in both shake flasks and pneumatic bioreactor was determined to be pH dependent. The maximum NH4 +/NO3 - removal evaluated over a period of 8 days for CDB and 15 days for AOB, observed at pH 7.7 in shake flasks, was 75% and 88%, respectively, in the absence of F-CN. Similarly, the removal of NH4 +/NO3 - in a pneumatic bioreactor was found to be 97.31% for CDB and 92% for AOB, thus demonstrating the importance of aeration in the designed process. The nitrification by CDB was not inhibited by cyanide loading up to a concentration of 8 mg FCN/ L, while the AOB were inhibited at cyanide loading concentration of 1 mg F-CN/L. The CDB removed the NH4 +/NO3 - in PBSs operated in a fed-batch mode, obtaining efficiencies >99% (NH4 +) and 76 to 98% (NO3 -) in repeated cycles (n = 3) under F-CN (≤8 mg F-CN/L). The input variables, that is, pH, temperature and whey-waste concentration, were optimised using a numerical optimisation technique where the optimum conditions were found to be: pH 9.88, temperature 33.60 °C and whey-waste concentration 14.27 g/L, under which 206.53 mg CN-/L in 96 h can be biodegraded by the microbial species from an initial cyanide concentration of 500 mg F-CN/L. Furthermore, using the optimised data, cyanide biodegradation in a continuous mode was evaluated in a dual-stage packed-bed bioreactor connected in series to a pneumatic bioreactor system used for simultaneous nitrification including aerobic denitrification. The whey-supported Bacillus sp. culture was not inhibited by the free cyanide concentration of up to 500 mg F-CN/L, with an overall degradation efficiency of ≥99% with subsequent nitrification and aerobic denitrification of the formed ammoniu and nitrates over a period of 80 days.