Masters Degrees (Civil Engineering)

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A numerical study of bacteria transport through porous media using the green element method.
(2000) Ramsuroop, Suresh.; Onyejekwe, Okey Oseloka.
The continued widespread contamination of the subsurface environment by microbial pathogens and chemical wastes has resulted in an increased interest in the factors that influence microbial transport through porous media. In this work a numerical study is undertaken to determine the influence of various processes that contribute to microbial transport in porous media. The evaluations were conducted by the simulation of a typical macroscopic transport model, using a novel numerical technique referred to as the Green Element Method (GEM). This computational method applies the singular boundary integral theory of the Boundary Element Method (BEM) to a discretised domain in a typical Finite Element Method (FEM) procedure. Three models are presented to evaluate the effects of the various parameters and factors: a constant porosity model was formulated to verify the GEM formulation against an analytical solution, a variable porosity linear model was developed and used for the simulation of the transport process involving first order type clogging, and a variable porosity nonlinear model used to evaluate effects of nonlinear type clogging. All three models were validated by simulations in specific applications in which analytical or deduced solutions were available. The parameters and factors evaluated included the effects of substrate concentrations, decay rates, source concentrations (boundary conditions), flow velocity, clogging rates, dispersivity, point and distributed sources, and nonlinear clogging. The results show that the trends predicted were consistent with the trends expected from theory. The conditions that enhanced bacteria transport included high velocities, low decay rate constants, high substrate concentrations, and low clogging rates. The range of dispersivities investigated showed little variation in the bacteria concentration in the longitudinal direction. Reduction in porosity resulted in retardation of the migrating plume. Conditions that led to significant loss in porosity are high bacteria loadings and high growth rates. The GEM formulation showed no restrictions or limitations in solving transient linear and transient nonlinear applications. In the nonlinear application, the Newton Raphson algorithm was successfully used for the iterative solution procedures. In addition, the GEM formulation easily facilitated the application of distributed and point sources in the problem domain.
Rural road maintenance through labour-based lengthmen system in Zambia.
(2000) Mwango, Abraham.; Little, Robert.
Rural road maintenance has received little or no attention in Zambia for a long time, resulting in an adverse impact on the economy. Meanwhile Road Authorities have continued to use traditional capital-intensive periodic and routine maintenance at the expense of scarce foreign exchange. The system has not performed well, hence the current state of roads. Labour-based methods for routine maintenance under the Lengthmen System used in Kenya, Lesotho and other developing countries in the Sub-Saharan Africa have proved to be technically and economically viable. In this report the author examines the desirability of using the Labour-Based Lengthmen System as an alternative to the existing capital -intensive methods in Zambia. This is done through rev iewing rural road maintenance in Zambia and then carrying out a comparative analysis of the same bctween Zambia, Kenya and Lesotho The comparative analysis shows that Zambia is not performing well when compared to Kenya and Lesotho. Meanwhile, the Lengthmen System is more desirable compared to other methods under the current economic conditions. Recommendations, based on the comparative analysis, have been given to improve rural road maintenance in Zambia.
Gaseous and particulate emissions.
(2000) Beebal, Nisha.; Lutchmiah, Johnny Soobramoney.
The need to limit sulphur dioxide, nitrous oxides and particulate matter emissions from fossil fuel combustion processes is now a major factor in the design, construction and operation of plants. Over the past 5 to 10 years, most developed countries have introduced legislations to control these. emissions. This report was done to investigate emissions of sulphur dioxide (S02), nitrogen oxides (NOx) and particulate matter from coal fired power plants. S02 emissions contribute to an air pollution load that has been found to be linked to respiratory and heart problems. It increases the formation of acid precipitation, called acid rain. NOx oxides to nitrogen dioxide (N02). N02 acts as an irritant to the respiratory tract, alveoli of the lungs and causes chest pains. Toxic elements concentrate on fine particulate matter because of their high surface-area to volume ratio. These particles penetrate and settle onto the lung wall, leading to respiratory disorders and lung diseases. Due to the strict legislative requirements, flue gas detoxification processes were investigated. They include: • Wet scrubbing • Spray dry scrubbing • Dual-alkali • Well man-Lord • Activated carbon • Magnesium oxides • Selective catalytic recovery • Circulating fluidised bed combustion • Electromembrane desulphurisation A study was done to show the possible cost implications associated with the wet scrubbing, spray dry scrubbing, selective catalytic recovery, circulating fluidised bed and electromembrane desulphurisation process. A variety of methods were used to calculate cost, due to costs being difficult to obtain. Most of the information was based on European, Asian and American installations. The objective of this economic analysis was to compare the different technologies. Because of the assumptions used, costs were always "order of magnitude" estimates. Capital and operating costs were calculated for these technologies, but they can only be used as an indication of costs and to allow for comparisons between the technologies. The costs were converted using the January 2000 exchange rates. Due to this, costs may be more inflated than what would normally be expected due to equipment being purchased earlier than January 2000. Of the processes investigated, the circulating fluidised bed process was found to be the most economical. There is no inexpensive route for the removal of sulphur dioxide, nitrous oxides and particulate matter. The most suitable detoxification process will depend on the legislative requirements per country. South Africa is a signatory of the Montreal Protocol and the Framework for Climatic Change. Legislations for gaseous emissions were not considered a priority. Currently, Eskom's drive is to electrify townships rather than spend money on detoxification processes. However, future legislations may require more stringent control measures.
Costing calculation of operation and maintenance in community water supplies.
(2001) Mwangi, Patrick Nduati.; Otieno, Fredrick Alfred Ochieng.; Ndiritu, John Gatherv.
Studies of community water have been on the increase since the International Drinking Water Supply and Sanitation Decade, 1981 - 1990. However there is some key areas of community water supply that still require research as the literature survey in this thesis illustrates. The Operation and Maintenance of community water supplies has been identified to be as important in sustainability of the services as the institutional factors. Due to the increased number of failure of the community water supplies to continue operation after short periods of time compared to urban water supplies, effort is required to identify the least amount of in puts to ensure continued operation. Through literature survey and field collection of data on management of existing projects a model was developed in order to calculate the minimum amount of funds required for the operation and maintenance. The research showed that the current monthly charges by water committees were sufficient to operate and maintain the systems. The initial calculations using the model also revealed that the current charges would not be sufficient to pay replacement costs. The presence of subsidisation through materials and labour by the central government requires planners to study each project thoroughly before the determination of monthly costs. The conclusion was that further research and data collection was required for the determination of the replacement cost. The model was found to be capable of assisting planners, managers and engineers in the calculation of the cost of operation and maintenance of community water supplies.
An assessment of water services in a peri-urban area of Umtata.
(2001) Ntuli, MzwaBantu.; Otieno, Fredrick Alfred Ochieng.
No abstract available.
Ultimate load and deflection behaviour of cellular beams.
(2001) Warren, Juliet.; Dougherty, B.
Cellular beams were developed in 1987 and are an adaptation of castellated beams having many of the same advantages and disadvantages. There are no published results of tests on cellular beams and there is only one recognised method of analysis and design. Full scale destructive tests were carried out for this investigation on eight cellular beams. Beams loaded at midspan and at the third points were tested. Failure load, failure mode and deflections were obtained for each beam. The existing analysis method as well as three new methods for both ultimate load behaviour and deflections were checked against the experimental results. The existing method of analysis was found to be over-conservative in predicting failure loads and inaccurate in predicting deflections. The analysis method which best predicted the failure loads and modes was the design chart which was developed for this investigation. The theoretical method which best predicted the deflection was the Vierendeel method which was also developed for this investigation.
Numerical and experimental study of transient heat transfer through concrete.
(2001) Mabuya, Thabo Gordon.; Onyejekwe, Okey Oseloka.
The increase in temperature of developing concrete as a result of heat liberated by cementing reactions is the primary cause for thermally induced cracks in large concrete elements. It is very essential, in engineering to predict the temperature rises in order to be able to minimise the potential of crack formation. This thesis covers the experimental determination of the heat of hydration curve using the adiabatic calorimeter and experimental determination of transient heat transfer obtained from measurement of temperature variations in concrete at its early ages of hydration. The measured temperature profiles from a one-dimensional heat transfer scenario are then compared with the predicted temperature profiles. The adiabatic hydration curve of a concrete beam sample is used as input into a numerical technique known as the Green Element Method for the calculation of temperature profiles. Time-based boundary conditions are imposed on the equation governing the model and will be solved using the Green Element Method coded in Fortran Power Station 4.0.
A linear catchment model for real time flood forecasting.
(2001) Sinclair, D. S.; Pegram, Geoffrey Guy Sinclair.
A linear reservoir cell model is presented which is proposed as a good candidate for real time flood forecasting applications. The model is designed to be computationally efficient since it should be able to run on a P.C and must operate online in real time. The model parameters and forecasts can be easily updated in order to allow for a more accurate forecast based on real time observations of streamflow and rainfall. The final model, once calibrated, should be able to operate effectively without requiring highly skilled and knowledgeable operators. Thus it is hoped to provide a tool which can be incorporated into an early warning system for mitigation of flood damage, giving water resources managers the extra lead-time to implement any contingency plans which may be neccssary to ensure the safety of people and prevent damage to property. The use of linear models for describing hydrological systems is not new, however the model presented in this thesis departs from previous implementations. A particular departure is the novel method used in the conversion of observed to effective rainlfall. The physical processes that result in the rainfall to runoff conversion are non-linear in nature. Most of the significant non-linearity results from rainfall losses, which occur largely due to evaporation and human extraction. The remaining rainfall is converted to runoff. These losses are particularly significant in the South African climate and in some regions may be as much as 70-90 % of the total observed rainfall. Loss parameters are an integral part of the model formulation and allow for losses to be dealt with directly. Thus, input to the model is observed rainfall and not the "effective" rainfall normally associated with conceptual catchment models. The model is formulated in Finite Difference form similar to an Auto Regressive Moving Average (ARMA) model; it is this formulation which provides the required computational efficiency. The ARMA equation is a discretely coincident form of the State-Space equations that govern the response of an arrangement of linear reservoirs. This results in a functional relationship between the reservoir response constants and the ARMA coefficients, which guarantees stationarity of the ARMA model.
Environmental study of the rehabilitation of the Monze-Zimba Road in Zambia.
(2001) Samu, Silupumbwe Justine.; Joslin, Paul.
It is very unfortunate that despite laws that require adequate incorporation and integration of environmental concerns at all phases of the economic developmental projects in Zambia, the research findings of this dissertation show that they are not applied well. The dissertation consists of six chapters. The Introduction (Chapter One) gives a general overview of Zambia, its geographical position in relation to other African countries, its macro and micro economic policies and its economic needs for a sound transport infrastructure. It also gives a rationale for the Monze-Zimba road rehabilitation project. Chapter Two reviews and states existing policies, legal, strategies and the institutional framework for environmental management and protection in Zambia. It also states and identifies key institutions involved in administering the various environmental laws/regulations and briefly refers to applicable International Conventions. Chapter Three gives a descriptive overview of baseline information - particularly within the catchment area of the road - regarding the biophysical, socioeconomic and cultural environments. The baseline studies provide insights into the normal background environmental variability such that appropriate monitoring programmes can be designed. It is now abundantly and evidently clear that the despoiling of the environment has negative repercussions on the health and wellbeing, culture and economic opportunities of humans. Chapter Four, therefore, provides in-depth discussions of each of the major impacts identified, their nature and scale and appropriate practical measures for their mitigation. The measures are incorporated into an Environmental Management Plan. Chapter Five addresses the environmental monitoring of the impacts resulting from the activities of the road. The Conclusion (Chapter Six) gives substantiated opinions on the overall findings of the research. Recommendations are given to the government of Zambia and all stakeholders on the best ways that environmental issues should be handled at all levels of society.
Turbulent mixing and dispersion in environmental flows.
(2002) Venayagamoorthy, Subhas Karan.; Stretch, Derek Dewey.
Stably stratified flows are common in the environment such as in the atmospheric· boundary layer, the oceans, lakes and estuaries. Understanding mixing and dispersion in these flows is of fundamental importance in applications such as the prediction of pollution dispersion and for weather and climate prediction/models. Mixing efficiency in stratified flows is a measure of the proportion of the turbulent kinetic energy that goes into increasing the potential energy of the fluid by irreversible mixing. This can be important for parameterizing the effects of mixing in stratified flows. In this research, fully resolved direct numerical simulations (DNS) of the Navier-Stokes equations are used to study transient turbulent mixing events. The breaking of internal waves in the atmosphere could be a source of such episodic events in the environment. The simulations have been used to investigate the mixing efficiency (integrated over the duration of the event) as a function of the initial turbulence Richardson number Ri = N2L2/U2, where N is the buoyancy frequency, L is the turbulence length scale, and u is the turbulence velocity scale. Molecular effects on the mixing efficiency have been investigated by varying the Prandtl number Pr = V/K, where v is the viscosity and K is the scalar diffusivity. Comparison of the DNS results with grid turbulence experiments has been carried out. There is broad qualitative agreement between the experimental and DNS results.· However the experiments suggest a maximum mixing efficiency of 6% while our DNS gives values about five times higher. Reasons for this discrepancy are investigated. The mixing efficiency has also been determined using linear theory. It is found that the results obtained for the very stable cases converge on those obtained from DNS suggesting that strongly stratified flows exhibit linear behaviour. Lagrangian analysis of mixing is fundamental in understanding turbulent diffusion and mixing. Dispersion models such as that of Pearson, Puttock & Hunt (1983) are based on a Lagrangian approach. A particle-tracking algorithm (using a cubic spline interpolation scheme following Yeung &Pope, 1988) was developed and incorporated into the DNS code to enable an investigation into the fundamental aspects of mixing and diffusion from a Lagrangian perspective following fluid elements. From the simulations, the ensemble averaged rate of mixing as a function of time indicates clearly that nearly all the mixing in these flows occurs within times of order 3 Vu. The mean square vertical displacement statistics show how the stable stratification severely inhibits the vertical displacement of fluid elements but has no effect on displacements in the transverse direction. This is consistent with the Pearson, Puttock & Hunt model. The important link that asymptotic value of the mean square vertical displacement is a measure of the total irreversible mixing that has occurred in the flow is made. However the results show that the change in density of the fluid elements is only weakly correlated to the density fluctuations during the time when most of the mixing occurs, which contradicts a key modeling assumption of the PPH theory. Improvements to the parameterization of this mixing are investigated. Flow structures in stably stratified turbulence were examined using flow visualization software. The turbulence structure for strong stratification resembles randomly scattered pancakes that are flattened in the horizontal plane. It appears that overturning motions are the main mechanism by which mixing occurs in these flows.
Experimental cadmium contamination of the echinoid Stomopneustes variolaris (Echinodermata: Echinoidea) : influence of dosage and distribution of the metal in the organism.
(2002) Bachoo, Santosh.; Moodley, Ganas Kandasamy.
Cd levels were measured in three different body compartments of the echinoid Stomopneustes variolaris after exposure to concentrations of 5 ug 1l, 20 ug 1l and 50 ug 1l Cd for a period of two weeks. The body compartments investigated included the intestine, gonads and skeleton. The gonads did not exhibit dose-dependent bioaccumulation. The levels of cadmium in the intestine and skeleton were significantly different between the treatments, suggesting that dose dependent bioaccumulation had occurred in these compartments (except in the skeleton where higher levels -were recorded for those exposed to 20 ug 1l than those exposed to 50 ug 1l) The levels recorded in the intestine were higher than those recorded in the gonads and skeleton at the higher Cd exposures of 20 and 50 ug 1i. The levels accumulated in the gonads and skeleton were not significantly different from each other. A separate group, exposed to 20 ug 1`1Cd over a period of two weeks, was placed in uncontaminated seawater to determine if the echinoids were capable of bioremediation. Bioremediation was found to lower the Cd levels in the gonads, but not in the intestine and skeleton. Cadmium levels for the three body compartments were also recorded from specimens collected from the field, indicating the presence of this element in the environment. In addition to using atomic absorption spectroscopy (AAS), energy dispersive X-ray analysis (EDX) was used as a comparative technique to detect the presence of Cd in the skeleton of the urchin. Cadmium was detected in the skeleton with AAS, but not with EDX. S. variolaris proved to be a capable biomonitor of Cd contamination.
Application of digital imaging in measuring cross track drift of vessels entering a port.
(2002) Patel, Sahil Ramesh.; Stretch, Derek Dewey.
Durban is the busiest container port in Africa and there are plans for significant expansion during the next few years. This expansion includes the widening of the port entrance channel to accommodate larger "post-panamax" vessels. Complex crosscurrents near the port entrance, coupled with severe wind and wave conditions, may lead to the intermittent closure of the port which in turn could lead to significant economic implications. Information on the nature of the crosscurrents and how they affect the ships could assist harbour pilots in developing their skills and reduce the risks associated with steering ships into the port. The research involved a case study to develop an innovative new method for directly measuring the effect of wind, waves and crosscurrents on ships entering the port. The technology is based on the application of digital image processing to track the position of ships as they manoeuvre in the port approach channel. The key innovation of this research is the extraction of the heading direction of the ship from the image data. The angle between this heading direction and the true velocity vector (the "crab angle") is then a direct measure of the cross-track drift velocity (CTDV) due to the combined effects of wind, waves and currents. The crosscurrents are usually the main contributing factor to the cross-track drift. The aim of this research was to develop a fully automated image processing system for real-time ship monitoring, and to determine cross-track drift within a wide range of weather conditions and ship parameters. The methodology presented in this research allows the spatial structure of the CTDV along the harbour approach channel to be studied. The relationship of the CTDV to local surface winds was analysed. For deep draught vessels, measured CTDVs were found to be poorly correlated to surface winds. The spatial structure of the measured CTDVs shows distinct regions along the approach channel where vessels experience significantly larger drift velocities. In summary, with the software tools developed by this research, digital images can be captured automatically and analysed to produce ship tracks and crab angles. From this information an extensive database for ship manoeuvring in the approach channel can be developed and the safety and efficiency of port operations improved.
Monitoring the health of the rivers of the Durban Metropolitan Area using fresh water invertebrates. A pilot study.
(2002) Nunkumar, Shamilla.; Dickens, Christopher William Spencer.; Olorunsogo, F.
This document is aimed at all parties involved with conservation, planning and management of rivers within the Greater Durban Metropolitan Area, South Africa. The intentions of this study were to provide information on the health of the rivers using freshwater invertebrates and to identify areas where investigative efforts should be focused. In doing so, this document incorporates two data processing methods or techniques used in biomonitoring, the South African Scoring System (SASS) Rapid Bioassessment Technique (RBA) version 4 and the Integrated Habitat Assessment System (IHAS version 2c). The history, current status and future prospects and potential benefits of biological indicators both globally and in South Africa are reviewed and discussed. The RBA (SASS4) involved the standardised collection of samples using the "kick and sweep" technique from defined habitat types at representative sites on river stretches using a standardised net following defined methods. The total score per site is calculated for each family represented in the sample, which is then summed to give the SASS4 score. Lower scores are given to families with a high level of tolerance for polluted waters. The Average Score Per Taxon (ASPT) computation is obtained by dividing the SASS4 total by the number of taxa (families) in the sample. Both scores were considered when determining water quality impairment. The number and abundance of the different taxa and the number of biotopes present were considered as other measures of the river condition. The presence of numerous families of highly tolerant organisms (sludge worms and leeches) usually indicated poor water quality as represented in the Umlaas River, iSiphingo River, Tongati River, and the Ohlanga River. Several different types (or taxa) of stoneflies, mayflies and caddisflies (higher biodiversity) indicated a healthy site for example the iLovu River. Moderate river sites were characterized by declination in invertebrate diversity. Invertebrate diversity declines as the degradation of water quality increases. The manner in which SASS4 scores varied with "degree of anthropogenic impact" showed that the assessment does yield results, which follow water quality changes, provided that when SASS4 scores are less than 50, little attention is given to ASPT. At intermediate and high impacted sites ASPT did not follow habitat quality. However at low impacted water quality sites both SASS and ASPT tended to be greatest where habitat quality was the best. This study has identified that water quality "appears" to have a greater effect on macro invertebrate communities than the physical habitat and SASS distinguished sites with differing levels of water quality. This method was not designed to enable the exact nature of the disturbance to be determined, and it was intended that once an impairment of water quality had been established, it would be further assessed via intensive chemical and other studies. The use of more ecological indicators for example the inclusion of IHAS (version 2c) allowed a more comprehensive assessment of river health and more confidence could be linked to the outcome.
Prediction, management and control of odour from landfill sites.
(2002) Laister, Guy.; Stretch, Derek Dewey.
Due to the spread of urbanisation and increased environmental awareness, odour has become a major problem in communities surrounding landfills. The aim of this research was to investigate odour emissions from landfills and develop a management tool that operators could use to assist in minimising the impacts of odour. The management tool would be in the form of real-time predictions of odour concentrations in the vicinity of a source. The Bisasar Road landfill in Springfield, Durban was a case study site for the research. The methodologies used in this project can be divided into three broad categories. Firstly, flow visualisation experiments were conducted on the case study site to investigate the effects of complex terrain and the results compared to predictions from a dispersion model. Secondly, source characterisation was done on-site. Sources of odour were identified using a portable odour monitor (Electronic nose). Sources of odour were then sampled using sorbent tubes and analysis done using Gas Chromatography - Mass Spectrometry. Thirdly, numerical dispersion modelling was done. Five available dispersion models were assessed and compared against one another in order to select the most suitable model for this application. A software management tool or 'Odour Management System' (OMS), was designed and implemented on a computer at the Bisasar Road landfill. Qualitative results of the flow visualisation experiments show that terrain does have an effect on a dispersing plume path for short-range predictions. Comparisons between the flow experiments and model predictions are qualitatively consistent. Quantitative results were not obtained for the emission flow rate and emission concentration of landfill gas. The chemical composition of the fresh waste gas was determined. ADMSTM(Advanced Dispersion Modelling System) was found to be the most suitable dispersion model for this application. The OMS has been installed on-site to produce odour concentration graphics every ten minutes. A fence line odour control misting system has been installed along approximately 600 metres of the landfill border based on work done as part of this project. Weather conditions and information provided by the OMS, assist in running the odour control system economically.
Estimating pedestrian accident risk using conflict techniques and digital imaging.
(2003) Dookhi, Revash.; Roebuck, Christopher S.
Accidents are a complex process involving many contributory factors. The understanding of the accident process has often been sought by the use of accident data. Although accident data provide a direct relationship to estimating accident risk, there are many drawbacks associated with the use of these data. The major drawback with the use of accident data is the very fact that traffic engineers have to wait for accidents to occur before any interventions can be made. This alone is significant as the time span required to collect a sample size is often a three-year period. The many deficiencies with accident data have led to alternative measures such as traffic conflict techniques (TCT's) to estimate accident risk.In this investigation. traffic conflict techniques were used to estimate accident risk. There are four basic traffic conflict concepts and the development of these techniques was based on the accident process. The aim of this investigation was to highlight the differences between these concepts and to assess the applicability of these concepts to vehicle-pedestrian conflicts. The investigation was based on applying the various conflict techniques to data obtained at three intersections in the Durban CBD. In order to record the data an innovative method of using digital imaging was employed. This led to the development of a computer program to analyse conflict events. Analysis of the intersections based on the conflict techniques indicates that the intersections of Pine-Field and Commercial-Grey have a high probability of road users being involved in a "serious event" once there is an interaction between them. However, the probability for Commercial-Albert intersection is low thus indicating a safe intersection for vehicle-pedestrian interactions. The number of "serious events" at these locations was found to be related to the interacting traffic volumes - the conflict rate increases with increasing traffic volume. The use of conflict-volume models and accident models together with the conflict concepts agree that the accident risk is related to the conflicting traffic volumes and speed of the road users.
An investigation into the technical feasibility of using vegetated submerged bed constructed wetlands for the treatment of landfill leachate.
(2003) Olufsen, Jonathan Simon.; Trois, Cristina.; Schreiner, Hilson Deneys.
Landfill leachate treatment in South Africa is still in its early stages; research has been conducted but primarily at pilot scale level. Current legislation in South Africa does not prohibit the discharge of landfill leachate into the sewer line, despite the high risk of methane explosions and corrosion of the sewer pipes. Thus, to date, the off site channelling of landfill leachate into the sewer lines for further dilution in municipal wastewater treatment plants is the most common practice. Due to the development of stricter environmental regulations, the design of sustainable landfills is leading to the 'treatment at source' concept. Increasing public pressure is also forcing new landfills to be situated in remote areas where there is no avaliable sewer line to discharge into and 'treatment at source' will be required. Due to these developments, coupled with the lack of full scale leachate treatment experience in South Africa, Durban Solid Waste (The waste service unit of the Durban metropolitan), in an attempt to develop the knowledge and practical experience required for leachate treatment, undertook a research project to investigate the use of nitrification/denitrification pilot scale sequencing batch reactors (SBR) to treat leachate from the Bisasar Road and Mariannhill Landfills. The successful completion of the trials proved that the full removal of nitrogen compounds could be easily achieved, under South African climatic conditions, in a single sludge SBR system. The system was found to be simple to operate and required low maintenance. However, the final effluent required further treatment before it could meet the general discharge standards into natural watercourses. Being South Africa, a 'low gross income' country, it became necessary to consider an appropriate, cost effective and technically feasible 'polishing' treatment system. It was decided that a pilot scale treatment trial, using vegetated submerged bed constructed wetlands, be undertaken to assess the applicability and feasibility of such a passive system for the 'polishing' of the effluent from the pilot scale sequencing batch reactors. The wetland systems were found to be affected by many interrelating climatic factors. The trials concluded that the wetlands could not achieve the required discharge standards, in terms of concentration. However, it also showed that the effluent organics posed no oxygen demand or toxic threat to a receiving environment. The trials showed the ability of the wetlands to behave as mass removal systems, which could achieve the required mass removal efficiency in terms of mass output per day.
Coastal water quality.
(2003) Mardon, David W.; Stretch, Derek Dewey.
This research focuses on the pathogenic pollution of coastal recreational waters. Pollution of this resource can have serious social and economic implications. The health of the public could be compromised and there may be associated adverse impacts on the tourism industry. A section of coastline along the Durban Bight and including some of the nation's premier bathing beaches, was used for a case study. The water quality condition of the beaches was evaluated against both local and international marine recreational water quality standards. Most of Durban's bathing beaches were found to have good water quality. However beaches situated close to stormwater drains regularly experience poor water quality conditions. The relationships between beach water quality, the pollution sources and environmental factors such as rainfall were quantified. A weak correlation was found between rainfall and beach pathogenic pollution levels. No correlation was found between successive fortnightly beach samples indicating that the time scales of coastal dispersion processes are significantly shorter than the beach monitoring period. The research also indicates a need to update the SA marine water quality standards. The exclusive use of Escherichia coli (E.coli) as the indicator of faecal pollution is inconsistent with international trends towards the use of Enterococcus, which is a more robust pathogen indicator for marine environments. The main aim of the research was to develop a model to predict the water quality conditions of beaches. The Coastal Water Quality Model (CWQM) is intended to serve two functions: firstly to provide daily estimates of pathogenic pollution levels for beach management (e.g. closure under poor water quality conditions), and secondly to provide decision-makers with a tool for predicting the effects of changes on future water quality conditions. The CWQM was formulated as a stochastic state-space lumped advection diffusion model. A Kalman Filter was used for state estimation. Parameter estimation using the Extended Kalman filter was investigated but found to be unsatisfactory due to large input uncertainties and sparse measurements. An alternative statistical fitting procedure was therefore used for parameter estimation. The model was shown to produce accurate predictions of pathogenic pollution for the case study site. To further demonstrate it's utility. it was used to evaluate options for improving the poor water quality at Battery Beach. The results show that a constructed wetland could be effective in this case.
Modelling flood inundation in the Mlazi river under uncertainty.
(2003) Mkwananzi, Nokuphumula.; Pegram, Geoffrey Guy Sinclair.
The research project described in this dissertation studies the modelling techniques employed for the Mlazi River in the context of flood analysis and flood forecasting in order to model flood inundation. These techniques are applicable to an environment where there is uncertainty due to a lack of historical input data for calibration and validation purposes. This uncertainty is best explained by understanding the process and data required to model flood inundation. In order to model flood inundation in real time, forecasted flood flows would be required as input to a hydraulic river model used for simulating flood inundation levels. During this process, forecasted flood flows would be obtained from a flood-forecasting model that would need to be calibrated and validated. The calibration process would require historical rainfall data correlating with streamflow data and subsequently, the validation process would require real time streamflow data. In the context of the Mlazi Catchment, there are only two stream gauges located in the upper subcatchments. Although these stream gauges have recorded data for 20 years, the streamflow data does not correlate with disaggregated daily rainfall data, of which there are records for at least 40 years. Therefore it would be difficult to develop the forecasting model based on the rainfall and streamflow data available. In this instance, a more realistic approach to modelling flood inundation involved the integration of GIS technology, a physically based hydrological model for flood analysis, a conceptual forecasting model for real time forecasting and a hydraulic model for computation of inundation levels. The integration of modelling techniques are better explained by categorising the process into three phases: Phase 1 Desktop catchment modelling: A continuous, physically based simulation model (HEC-HMS Model) was set up using GIS technology. The model applied the SCS-UH method for the estimation of peak discharges. Synthetic hyetographs for various recurrence intervals were used as input to the model. A sensitivity analysis was implemented and subsequently the HEC-HMS model was calibrated against output SCS-UH method and peak discharges simulated. The synthetic hyetographs together with results from the HEC-HMS model were used for validation of the Mlazi Meta Model (MMM) used for real time flood forecasting. Phase 2 Implementation of the Inundation Model: The hydraulic model (HEC-RAS) was created using a Digital Elevation Model (DEM). A field survey was conducted for the purpose of capturing the roughness coefficients and hydraulic structures, which were incorporated into the model and also for the confirmation of the terrain cross sections from the DEM. Flow data for the computation of levels of inundation were obtained from the HEC-HMS model. The levels of inundation for the natural channel of Mlazi River were simulated using the one dimensional steady state analysis, whereas for the canal overbank areas, simulation was conducted for unsteady state conditions. Phase 3 Creation of the Mlazi Meta Model (MMM): The MMM used for real time flood forecasting is a linear catchment model which consists of a semi-distributed three reservoir cell model (Pegram and Sinclair, 2002). The MMM parameters were initially adjusted using the HEC-HMS model so that it became representative of the Mlazi catchment. This approach sounds unreasonable because a model is being validated by another model but it gave the best initial estimate of the parameters rather than using trial and error. The MMM will be further updated using record radar data and streamflow data once all structures have been put in place. The confidence in the applicability of the HEC-HMS model is based on the intensive efforts applied in setting it up. Furthermore, the output results from the calibrated HEC-HMS model were compared with other reliable methods of computing design peak discharges and also validated with frequency analysis conducted on one of the subcatchments.
A universal method for assessing intrinsic expansiveness of soils.
(2004) Habte, Kebreab Berhane.; Schreiner, H. D.
Many of the attempts made over the past six decades to find a universal system for assessing expansiveness of soils using soil index data have failed to follow the basic principles of soil mechanics. By overcoming most of these limitations Gourley and Schreiner (1993a) developed a new procedure that allows comparison of intrinsic expansiveness of soil samples prepared to have stable micro-fabric and consistent stress history. In this research, the same procedure is used on twenty-seven natural clayey soil samples of varying geological, geomorphological and geographical origin obtained from Kenya, Sudan, Eritrea and South Africa. Each of these samples was tested for Atterberg limits, volume change behaviours and soil suction. Statistical analysis was conducted on different soil parameters derived from these tests to obtain a significant relationship with their intrinsic expansiveness using measured swell. The analysis confirmed that most of the significant relationships obtained contain swell index, C*5' showing the identicalness of the soil properties responsible for volume change behaviour of both saturated and unsaturated clayey soils. Depending on the cost and the significance, the analysis recommended three major models that can be used as a screening system in the assessment of intrinsic expansiveness. For any soil it is possible to obtain preliminary information regarding its intrinsic expansiveness using the cheapest of the recommended models that needs liquid and plastic limit tests and hydrometer analysis, which are the routine tests of geotechnical site investigation. A more detailed assessment can be achieved by including only t he shrinkage test. The most reliable assessment needs addition of consolidation test with the unloading stage. All of the models allow obtaining information regarding the intrinsic expansiveness of soils as early as site investigation stage for successful engineering design. Moreover, they are anticipated to promote worldwide exchange of information regarding these problematic soils.
A sustainable delivery approach for peri-urban and rural areas.
(2004) Mncwango, Zanele Racheal.
Challenges of implementing Integrated Development programmes can be seen in the difficulty in aligning different departmental budgets and processes in the implementation phase of projects. This has had many implications for development. However, the use of conventional and single sector approaches to meet development needs has been more apparent. The need to respond to a lack of basic services and poverty in rural and periurban has been growing. Absence of appropriate rural and peri-urban development approaches, and non-alignment of policy and budgets across government structures have resulted in the use of urban based models. This has culminated in the creation of settlements that are unable sustain themselves over time. The dissertation puts forward the hypothesis that "community development through the housing approach is not an appropriate development mechanism for rural and peri-urban areas". It also highlights problems faced in attempting peri-urban and rural areas. This is illustrated by a case study - Intathakusa Integrated Development Programme. This is a peri-urban and rural development programme located within the boundaries of eThekwini Metropolitan Area and is used to illustrate problems faced by a number of areas of similar nature. This project attempted to deliver integrated programmes within the urban edge and the peripheral parts of the city. Qualitative research methods facilitated an in-depth exploration of relevant issues in this dissertation. Development practitioners and community representatives were interviewed to elicit information on the challenges facing peri-urban and rural development and to explore possible alternatives. The dissertation concludes with suggestions for sustainable livelihoods approaches for rural and peri-urban areas. The research also acknowledges that the housing package is perhaps a basic requirement for rural and peri-urban areas. It acknowledges that housing offers a means through which a bundle of basic services (over and above a house) can be delivered. The research concludes by arguing that if this funding mechanism is to be used in rural and peri-urban areas, it should be repackaged to include bigger site sizes and agriculture.

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