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This study was designed to develop some predictive models for the dielectric properties of the chemicals and chemical reactions and make use of dielectric properties and microwave irradiation in the chemical reactions. Specifically, the dielectric properties of the following systems were investigated at microwave frequencies of 2450 and 915 MHz: (1) C1--C5 alcohols, (2) glucose aqueous solutions, (3) lysine aqueous solutions, (4) mimicked esterification reaction model systems of parahydroxybenzoic acid with methanol, 1-propanol and 1-butanol in the presence of para-toluene sulfonic acid as a catalyst, (5) Maillard reaction model system consisting of glucose, lysine and water. / The dielectric properties of the model systems showed that they depended on the frequency applied, concentration of the material, and temperature. Most of the predictive models showed that there exists a linear or quadratic relationship between dielectric constant and concentration or temperature. However, the quadratic equation is better than the linear one to describe the variation of the loss factor with temperature or concentration. / Esterification showed great advantages for the use of microwave irradiation in chemical reaction. It included reduction in reaction time, and provided distinct temperature profiles due to microwave environment during chemical reactions. The reason for rate enhancement of this type of reaction was also demonstrated from the temperature profile. / Microwave-assisted solvent free Maillard reaction model system, consisting of glucose and lysine, demonstrated that the heating method applied was not one of the crucial factors, but the temperature level was important during the chemical reaction. / The relationship of loss factor with yield of reaction showed that it is possible to use dielectric data to analyze, and monitor the chemical reaction. It provided a new methodology to analyze the reaction. / The relationship between the loss factor, loss tangent and the reaction time, and concentration of the material showed that it is also possible to use dielectric data at microwave frequencies of 2450 and 915 MHz to study chemical reactions, especially the kinetics.

Cheese ripening is a costly and lengthy process. Increasing the enzyme pool in the cheese curd has been shown to accelerate the cheese ageing process, enhance flavour and texture. The characteristics of two lactic acid bacteria attenuated by pulsed electric fields were studied in a milk system and in cheese slurry. The potential of accelerating cheese ripening via the addition of starter cultures attenuated by pulsed electric fields (PEF) was studied. / Pulsed electric field treatment was performed in a static treatment chamber using bi-polar waveform with a field intensity of 20 kV and 2 mus pulse width. The number of pulses ranged from 10 to 500. Evaluation of the starter cultures was assessed through the analysis of acidifying abilities, survival fractions, enzymatic activities and proteolysis (RP-HPLC and Cd-ninhydrin) in water soluble nitrogen extracts following the different attenuation treatments. / Pulsed electric fields significantly affected the general viability of the cells through a delayed acidification and an inhibition of enzymatic activity. A study in cheese slurry systems showed that the cultures under investigation were not able to provide an increased proteolysis levels following PEF treatment. The results of this study also suggest that optimal PEF treatment varies for each LAB strain and that the Lactococcus strains do not possess high enough proteinase and peptidase activities to be beneficial for the acceleration of cheese ripening.

Microorganisms have the potential to remove heavy metals from polluted waters and effluents and may be used in clean-up processes. Microbial associations were enriched for and adapted to grow in nutrient solutions containing various concentrations of different metals. As immobilised cells are known to be more stable and more efficient in metal uptake than are corresponding planktonic or free-living cells the attachment of the microbial associations was investigated using a model stream and it was found that biofilm development was better on rough surfaces such as ground glass and polystyrene than on smooth surfaces such as unetched glass plates and glass beads. When comparing metal uptake by planktonic and attached microorganisms, attached populations were found to have a greater metal-uptake capacity. The uptake of individual metals from various metal combinations was tested with various proportions of pregrown metal-adapted microbial populations as inoculum and it was found that a particular metal was taken up more readily by microbial associations which had previously been exposed to that metal. Lead (Pb2+) appeared to be taken up more readily than copper (Cu2+) or cadmium (Cd2+) while Cd2+ was more actively removed than Cu2+ from solution. pH also affected metal uptake and the optimum range for Cu2+ uptake by the Cu2+ -adapted microbial association was found to be between 5.8 and 7.0. Dead microbial biomass was investigated and found to have efficient metal uptake capacity. Living mycelium from an isolated Aspergillus species showed poor uptake of Cu2+ initially, but when this fungus was pregrown and subsequently killed by moist heat treatment the non-living mycelium was efficient in removal of Pb2+ and Cu2+ ions. The optimum mycelial biomass concentration for metal uptake was also determined. The mechanism of metal uptake by this Aspergillus species was determined, using electron microscopy and EDX techniques, to be metabolism-independent biosorption onto the hyphal surface. Thus the microbial associations and fungal cultures used in this study were shown to have the potential for use in the removal of heavy metals from polluted waters. / Thesis (Ph.D.)-University of Natal, Pietermartizburg, 1995.

Customs administrations, worldwide, are adopting the trend towards risk-based processing of international cargoes as a means of facilitating trade. This has lead to the introduction of innovative processes ably supported by technology to realize improvements in customs effectiveness and overall efficiency. Widespread use of e-commerce in trade-customs transactions and exchanges, likewise necessitates complimentary technical support where Customs has need to intervene in a specific import, export or transit consignment. South African Revenue Service (SARS) is presently developing and enhancing its core competencies through training of its personnel in the disciplines of risk management, anti-smuggling and post clearance audit. It therefore becomes essential that these capacity building initiatives be complimented with the most appropriate tools for conducting cargo examination. The current physical examination process and inspection techniques are both time consuming and costly for business and render the goods liable to damage and theft. Recent historical events, specifically the 9/11 tragedy in New York, has caused international organizations such as the G8 and World Customs Organization (WCO) to consider the implications and effects of terrorism on international maritime transportation. The G8 adopted a Co-operative Action Plan on Security covering all aspects of transportation security and the WCO adopted a Resolution on Security and Facilitation of the International Supply Chain. Both initiatives aim to ensure safer and more secure maritime trade on the global scale. Fundamental to SARS Customs ability to successfully implement such measures are the following: Availability of advance electronic customs data Automated risk profiling and targeting capability Availability of non-intrusion inspectional devices (X-ray cargo scanners) to examine cargo. These three criteria are essential for SARS to participate in supply chain security initiatives and to facilitate the transportation of international consignment. Accordingly this research project explores how the external and internal environment impacts on SARS. It further critically analyses the core competencies and resource strengths of SARS. To support SARS in its effort and in its process of starting a project to improve controls and facilitation of goods at ports of entry within the Republic, this study explores and expounds on infrastructure and business application needs of SARS. Finally the research project concludes with a recommendation of the most effective approach towards the implementation of cargo scanner 'shared, outsourced service." / Thesis (MBA)-University of Natal, Durban, 2003.

With the exceptions of mixing and heating mechanisms, and the recycling of settled solids, no radical changes or improvements have been made to conventional anaerobic digesters treating municipal sewage. These digesters usually function with a hydraulic retention time of 30 to 60 days and at a total solids concentration of 2.6 %(m/v). Volumetric loading is limited since high loadings effect the displacement of the slow growing methanogens. Thus, the hydraulic retention time is coupled to the solids retention time. A crossflow microfiltration unit has been constructed at Northern Waste Water Treatment Works, Durban, to concentrate sludge from a conventional anaerobic digester and, thus, facilitate operation with a higher solids concentration. In addition, this process should result in the retention of the active biomass which would otherwise be lost as a waste product of the treatment process. The solids retention time is, thus, decoupled from the hydraulic retention time. The net result could be higher volumetric loadings, increased microbial activity and increased volatile solids destruction and, hence, improvement in the efficiency of anaerobic digestion of sewage sludge. To test these, different experiments were conducted to specifically determine the effect of higher solids loads. Preliminary experiments were undertaken to determine the biodegradability of primary sludge from the Northern Waste Water Treatment Works. Results showed that primary sludge of 76% VS could be reduced to approximately 48 to 50% VS during an experimental period of 85 days. Reduction of the first 20% VS was rapid if conditions were optimum but subsequent reduction from 55 to 50% VS was slow. It was calculated that approximately 0.88 l gas was produced for every g volatile solids catabolised. Further experiments were conducted to investigate the effects of different solids concentrations on microbial activity. The results showed that the volume of gas produced increased as the solids concentration increased from 2 to 6%(m/v). Digesters with solids concentrations of 6 to 13%(m/v) produced similar volumes of gas. Digesters with solids concentrations of 6 to 13%(m/v) TS produced approximately 300 ml more gas than the control during the 20 days experimental period. The rate of gas production also increased as the solids concentration increased. However, digesters containing 11%(m/v) and 13%(m/v) TS produced similar rates. These results indicate that the introduction of concentrated sludge into the digester improves digestion efficiency. Finally, a semi-continuous digester was operated at a 30 days retention time and at optimum temperature to investigate the efficacy of digesters with increased solids concentrations. The results showed that the rate of gas production increased as the solids concentration increased from 2%(m/v)(control) to 3.8%(m/v). However, the digester operated with 4.7%(m/v) TS produced gas at a rate lower that the digester with 3.8%(m/v) TS. The volatile solids concentrations of all four digesters were similar, indicating neither favourable nor unfavourable effects from increased solids concentrations. The digesters operated with 3.8%(m/v) and 4.7%(m/v) TS produced higher concentrations of volatile acids than the control. The alkalinity concentrations (>_4000 mg t-1 ) were similar for all four digesters. / Thesis (M.Sc.)-University of Natal, Durban, 1995.

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