Civil Engineering

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A review of the engineering properties of concrete with paper mill waste ash — towards sustainable rigid pavement construction.
(Silicon) Pillay, Deveshan L.; Oladimeji B., Olalusi; Mostafa, Mohamed M.H.
The drastic surge in urbanisation and construction-related activities is increasing the demand for cement and aggregates, especially for concrete production. Concrete is utilised for a wide variety of structural applications, including rigid pavements construction, due to its superior strength and durability performance. However, the production of cement and concrete increases carbon footprint; and the source of natural aggregates depletes. Hence, there is an increased demand for pavement designs that incorporate sustainable materials and maintain a consistent level of service. In rigid pavements construction, this can be achieved with the integration of alternate binder systems, such as paper mill ash (PMA). This paper presents a systematic review of the engineering properties of PMA as a partial cement replacement material for sustainable concrete production. The review is focused on the influence of PMA on the engineering properties of concrete. The main advantages and limitation of using PMA were highlighted and discussed. Grey areas for possible research exploit were also identified. Based on the superior tensile (2.68 – 3.98 MPa) and flexural (4.04 – 5.01 MPa) strength results documented in the various works of literature reviewed, it can be concluded that PMA is a feasible alternative binder material for rigid pavement applications. This, coupled with its negligible CO2e emission value, indicate that PMA is beneficial to the sustainability and serviceability states of rigid pavements. The viewpoint of this review will be useful for researchers for their future studies and guide stakeholders in the construction industry to have more understanding of PMA concrete.
The advancement of the waste resource optimization and scenario evaluation model: the inclusion of socio-economic and instituitonal indicator.
(2018) Kissoon, Sameera.; Trois, Cristina.
This study explored Novice Teacher Educators (NTEs) experiences of Relational Learning in a private Higher Education Institution (HEI) in South Africa. The main purpose of this study was to gain a deeper understanding of how NTEs involved in initial teacher education experience Relational Learning in a private HEI. It further attempted to gain an insight of how these experiences of Relational Learning influenced their learning as teacher educators and their work as NTEs in a private HEI context. Literature used in this research highlighted the need to develop competent NTEs due to the increase demand for access into higher education institutions, public and private, the limited structured induction and mentoring for NTEs and the limited research on the relational experiences of NTEs. Key debates on national and international higher education contexts were also foregrounded. The literature review also focused on understanding the phenomenon of Relational Learning as a progressive approach to learning, through and about relationships. Relational Learning is viewed as a catalyst for learning with others. Situated Learning Theory (SLT) and Relational Cultural Theory (RCT) was employed as the theoretical framework for the study. The study focuses on six NTEs who are newly appointed teacher educators in their first three years of employment primarily involved in the teaching of pre-service teachers (or student teachers) in a private HEI's as research context. The NTE participants moved from a school context into a HE context. This research study is a qualitative interpretive case study. All six NTEs that participated in this research were purposively selected by the researcher. Criteria used to select participants included NTE being in their first three years of their higher education careers and being able to access technologically devices. A qualitative approach was used to generate data and the data generation instruments used were questionnaires, individual semi structured interviews and a collage with presentation. The data generation process took three months and data generated was validated for authenticity by each participant by member checking. The findings of the data revealed that NTEs experienced many challenges in their first few months of being NTEs and considered this to be an exceptionally overwhelming shift. To overcome these difficult times NTEs moved to develop relationship with colleagues and more than often self-selected their mentors to guide and assist them as there was limited structured and mentoring with the institution. The relationship developed between NTE and self-selected mentor is a growth fostering relationships as foregrounded in Relational Cultural Theory. The xiii. findings of this research showed that mutual relationships between NTEs and teacher educators paved the way for NTE to become active members of communities of practice (COP). The responsibilities of HEIs is to provide relational opportunities for NTEs so they may ease into the profession. Relational opportunities such a mentoring, inductions, conversations and social activities to name a few have a fundamental role to play in enculturating a NTEs into HEI. Relational Learning has a pivotal role to play in the growth and development of NTEs thus improving the quality of teacher education
Alternative binder materials for rigid pavements – an investigation into the structural and sustainability effects of partial cement replacement with pulp and paper mill waste ash in concrete pavements.
(2021) Pillay, Deveshan Loganathan.; Mostafa, Mohamed Mostafa Hassan.; Olalusi, Oladimeji Benedict.
Abstract available in PDF.
Anaerobic digestion of energy crop (cassava)
(2019) Sawyerr, Nathaniel Olugbenga.; Trois, Cristina.; Workneh, Tilahun Seyoum.; Okudoh, Vincent Ifeanyi.
Global energy demand is on the rise due to continuous increases in population, economic growth, and energy usage. Methane production through anaerobic digestion of organic materials provides a resourceful carrier of renewable energy, as methane can be used instead of fossil fuels for both heat and power generation and also as vehicle fuel, thus cutting down the emissions of greenhouse gases and hence contribution in the slowing down climate change. Several studies have been done on biogas, but in South Africa, these are biased towards industrial wastewater. Therefore, there is need to explore other alternatives for biogas generation. Furthermore, the sustainability of anaerobic digestion processes depends on the availability and the identification of the optimal substrate. The use of cassava in South Africa provides a great potential for the production of bioenergy especially biogas, due to its suitable chemical composition. Cassava codigested with other feedstock could be an alternative substrate for various communities for the production of biogas in South Africa. Since cassava is yet to be listed as a staple food crop in South Arica, its peels and other by-products from its processing can be suitable for renewable energy production for small medium enterprises (SMEs). This study’s overall objective was that of establishing the suitability of cassava tubers as an alternative source of biomass feedstock for biogas production in South Africa. The specific objectives of the study were: 1) Comparing the yield and rate of biogas production of cassava peels inoculated with cattle manure using a batch digester under anaerobic digestion conditions addressed in chapter four and five of the thesis; 2) Investigate the biogas yield and rate of different co-digestion ratios of cassava with vegetable and fruit waste using batch digestion under anaerobic digestion conditions presented in chapter six; 3) Optimize the production of biogas through process optimization by maintaining the optimum temperature during fermentation and compare inexperiments subjected to different treatment or treatment combinations and, 4) While chapter seven addresses the objective of using the experimental results to design an upscale system using baseline data information from experiment. Several feedstocks (i.e. cassava tuber, cassava peels, vegetable and fruit waste and cattle manure) were identified and analysed using the American Standard Methods for examination of Water and Wastewater (ASTM). Cassava was selected as it has several advantages compared to other crops, including the ability to grow on degraded land and where soil fertility is low. It also has the highest yield of carbohydrate per hectare (4.742 kg/carb) apart from sugarcane and sugar beet, which makes it suitable for bioenergy (biogas) generation. In the first instance, a batch experiment of were cassava peels were digested anaerobically with and without cattle manure to determine whether cassava peels (CP) in combination with cattle manure (CM) at different ratios shows better biogas yield. The following ratio combinations of mixture were used 100:0, 0:100, 80:20 and 20:80 (CM:CP). A theoretical methane production was conducted using elemental composition and the results were compared with the experimental ones. The test of biogas yield was conducted using an anaerobic digester of 600 ml at mesophilic (35 ± 1 °C) temperature. In the second experiment a 50 litres anaerobic digester was used to investigate the biogas yield of peeled cassava tuber compared to unpeeled cassava tuber that yield biogas of 635.23 L/kg VS and 460.41 L/kg VS respectively. This was based on the finding of the first experiments of biogas yield from cassava peels. The biogas yield with and without inoculum was measured and the biogas yield were modelled using two different models namely modified Gompertz and cone model. Finally, in parallel with the previous batch experiments another set of batch experiments were carried out under anaerobic conditions at mesophilic (35 ± 1 °C) temperature in a 600 ml digester, this experiments was conducted by co-digesting cassava (CB) with vegetable and fruit waste (CB:VF) at different ratios (100:0, 60:40, 40:60 and 50:50). The cumulative biogas yield were modelled for kinetics using modified Gompertz model. Based on the results obtained from the experimental study cassava co-digested with vegetable and fruits at a ratio of 40:60 which was found to produce the maximum yield, a mathematical design (upscale system) was designed. This designed biogas plant could be located in several communities especially those close to the landfills to reduce the cost of transportation from source. The study’s results revealed that: • co-digestion influenced biogas production and methane yield. The final cumulative methane yields by the co-digestion of CM and CP at the CM:CP mixing ratios of 80:20 and 20:80 were 738.76 mL and 838.70 mL respectively. The corresponding average daily methane yields were 18.42 mL/day and 20.97 mL/day. This indicates that CP enhanced the production of methane in the co-digestion process with the 20:80 CM:CP ratio. • the feedstock of peeled cassava with inoculum, produced 28.75% more biogas yield when compared to peeled cassava without inoculum. This results highlights the important of inoculum in the anaerobic digester. • peeling the cassava tuber increase the biogas yield by 38% compared to the unpeeled tuber • cassava biomass co-digested with vegetable and fruit waste increased the methane yield compared to the mono-digestion with the highest methane production was achieved from the co-digestion of cassava biomass with vegetable & fruit waste at 40:60 ratio (CB: VF) Although several challenges hampering the smooth implementation of biogas generation in South Africa, this study concludes that cassava (peeled and unpeeled) co-digested with fruit and vegetables waste has potential to generate biogas thereby presenting a substantial opportunity to promote bioenergy production from cassava considering in many rural areas the needs for fuel and electricity are not satisfied fully. Finally, cassava anaerobic digestion facility at different scales could enhance additional benefits like the integration of nutrients and residual carbon into the land as fertilizer.
The analysis of connected back to back mechanically stabilised earth walls.
(2019) Ramjee, Amit Kantillal.; Scussel, Dario.; Drosopoulos, Georgios A.
Back to back mechanically stabilised earth walls (MSEW’s) are designed independently as there is a lack of design guidance in the British Standard - Code of practice for strengthened/reinforced soils and other fills (BS8006-1:2010) for their analysis and design. Designers are sometimes tempted to have continuous reinforcement from each face of the back to back MSEW’s to save time and money especially when narrow back to back MSEW’s cause an overlap of reinforcement from each wall face. Unfortunately, the design guidance available is few and far between with vague recommendations presented by various authors and organisations. This dissertation focuses mainly on the forces generated in the reinforcement of the MSEW’s. A case study of an existing back to back MSEW with continuous reinforcement between the walls was first carried out using BS8006-1:2010 and finite element methods (FEM). The FEM analysis was carried out using the finite element modelling software package Plaxis 2D. Thereafter, a study using FEM was carried out to investigate the effects on the forces generated in the reinforcements for various types of geometries. The different geometries varied by having back to back MSEW’s with independent reinforcement, continuous reinforcement, and overlapping reinforcement. The forces generated in each configuration was then compared to forces that would have been calculated had the MSEW’s been designed using BS8006-1:2010. Conclusions and recommendations are then provided which would assist a designer wanting to have continuous reinforcement in a back to back MSEW.
Analysis of the water distribution main replacement conundrum in Durban.
(2012) Scruton, Simon Robert.; Stretch, Derek Dewey.
The optimisation of the decision of when to replace water distribution mains is a complex task. There are numerous drivers in the decision making process (informed by financial data, performance data and water quality data) and hundreds of variables and performance indicators that can be considered when trying to reach an optimised decision. Most of the assets under consideration are buried and the internal and external pipe conditions are not easily assessable, forcing the Utility to rely on the available direct and indirect variables from which conclusions on the reliability of the mains are to be inferred. The cost of mains replacement is relatively low but the assessment cost, if carried out can be relatively high. The total value of a metropolitan distribution network typically runs into billions of rands but the impact of an individual pipe failure is generally low. The distribution network is comprised of many different pipe materials and components, of different pressure classes, made by different manufacturers, installed by numerous contractors with different skill levels under differing quality control regimens over many years. To add to this complexity, various parts of the network are operated at different static pressures and varying velocities. Some sections of the network are isolated more often than others and at times there can be large pressure surges that the network is subjected to by either the Utility or Consumer. These pressure surges are known to have a marked detrimental effect on the network. False markers also exist that can give rise to totally incorrect decisions and therefore performance data cannot be accepted at face value and needs to be scrutinised and cleansed to increase its reliability prior to being utilised in decision making process. This important step has been missed by much of the research carried out to date. In the Durban context, a further complication is caused by consumers tampering with the water mains and also not reporting leaks. This has a negative effect on the performance of the water main that can cause it to be flagged for replacement, but its replacement will not result in an increase in performance if the social issues are not resolved first. The aim of this research is to make recommendations on the methodology to be employed to improve network performance and thereby delay the point at which the water mains are to be replaced for as long as possible. These recommended activities will be carried out to remove false markers and improve upon the quality and reliability of the data available on the network performance. A further output is to make recommendations regarding the minimum data that can be reasonably collected and analysed in order to determine an optimised result. The recommendation of which mains should be targeted for replacement should result in the highest benefit for the utility as well as the consumers. By implication, this will result lowest long term capital and operational expenditure and thus the lowest long term tariffs charged to the consumers whilst complying with the water quality criteria and service level targets.
An analysis on optimizing the use of sustainable urban drainage systems to provide non-potable water supply in the Isipingo region.
(2019) Ndebele, Bulelani.; Kumarasamy, Muthukrishna Vellaisamy.
Population growth and urbanisation lead to increased water demand and stress on water resources. The increased demand implies an increased water treatment cost, utilities therefore charge higher tariffs consequently reducing consumer affordability and accessibility. Furthermore, many countries experience drought and intermittent water supply, low revenue collections and high operational costs. The National Water Act (Act 36, 1998) endeavours to find a balance between water conservation or demand management, water safety, affordability and accessibility. Potable water in many countries, including South Africa, is being used for non-potable purposes which is wasteful and threatens the exhaustion of potable water reserves. This research looks at sustainable urban drainage systems as a possible solution for providing an alternative water supply. The methodological approach involves setting up a PCSWMM model to investigate the optimal use of SUDS systems in the Isipingo region. Required data such as monthly water supply volume, GIS information for characteristics of the region, water supply pipe network was collected from eThekwini municipality data base. Weather data such as rainfall, temperature and humidity were collected from South African Weather Services. The current System input Volume (SIV) in Isipingo region was estimated as 11 780 000 Kilo Litres per year from logged data between July 2018 and July 2019. The water treatment costs required by the utility for Isipingo baseline volume is R5.33 /KL according to eThekwini municipality’s master plans. A water balance model was constructed to illustrate the existing scenario. Different SUDS controls were then added onto the existing scenario to analyse the SUDS impact on the water balance components such as the baseline supply volume, water treatment cost and non -potable water demand. Results show that the municipal water supply demand reduces by an average of 74% across the use of the different SUDS scenarios. The water treatment costs reduce from R62 787 400 per year to an average of R 25 057 409,59 which is the treatment cost saving due to the SUDS interventions. The challenges with SUDS include initial installation and maintenance costs, the lack of adequate utility planning and design standards. However, SUDS reduce the risk of flooding, water pollutants, stress on potable water supply and contributes to the tourism economic activity through pleasing aesthetics for recreational areas and job creation. Therefore, the use of SUDS in diverting storm water for alternative non-potable usage is a viable option.
Anthropogenic impacts and biophysical interactions in Lake St Lucia.
(2013) Chrystal, Robynne Angela Lawrie.; Stretch, Derek Dewey.
The St Lucia estuarine lake system in South Africa is part of a UN- ESCO World Heritage site and a Ramsar wetland of international importance. Like many estuarine systems worldwide St Lucia has experienced signi cant anthropogenic impacts over the past century including catchment land use changes, water diversions/abstractions and inlet manipulation. In addition, the system has recently su ered losses in species diversity and abundance following unprecedented hy- persaline conditions and desiccation. Questions regarding its sustain- ability have motivated a reevaluation of management decisions made in the past and of options for the future. To understand the func- tioning of the system, it is necessary to analyse it holistically in terms of the physical processes and their interaction with the biology. This study focusses on aspects of the biophysical interactions in the estu- arine complex, and aims to provide new knowledge to underpin the development of improved models for predicting the response of the system to anthropogenic interventions. A model for the water and salt budgets was used to investigate what if scenarios in terms of past anthropogenic interventions, in particular the e ects of diverting the Mfolozi River from St Lucia. Furthermore, the risks of hypersalinity and desiccation were assessed for each sce- nario. Integrating these modeled scenarios with observed biological responses to physicochemical changes suggested that large long-term changes in the ecological structure can be expected in the di erent management scenarios. To validate this, the ecosystem response to changing environmental responses was quantitatively assessed using ecological network analysis. Long-term simulations show that the separation of the Mfolozi and St Lucia mouths had a signi cant impact on the functioning of the St Lucia system. The Mfolozi plays a pivotal role in maintaining a more stable mouth state regime and provides a vital source of freshwater during dry conditions. The con guration of the Mfolozi/St Lucia inlet plays a key role in the physico-chemical environment of the system and in uences the system's susceptibility to desiccation and hypersaline conditions. Ecosystem indices revealed that the water level, salinity and mouth state have a signi cant impact on species abundance and diversity as well as the ecological structure and functioning of the system. In addition, ecosystem indices show that the system recovers rapidly during favourable conditions. The arti cial separation of the St Lucia and Mfolozi inlets underpins the most signi cant impacts on the water and salt budget of the lake and its reversal is key to the sustainability of the system.
The applicability of C&D waste material in South Africa road construction.
(2015) Zedda, Valentina.; Trois, Cristina.; Everitt, Philip Robert.
In contrast to developed countries, South Africa is starting to adopt the practice of using recycled rubble from civil engineering demolition works in road construction. This change is due to environmental considerations, but somewhat unique nature of the South African road construction techniques requires a careful classification of these alternative materials and a rigorous study. In this study the possibility of reclaiming the Construction and Demolition (C&D) waste produced in the Durban Metropolitan Area was investigated. A lack of policies for the reuse of waste produced by the civil industry caused the storage of large quantities of C&D waste in the metropolitan landfill sites. In order to decrease this volume the rubble can be reused as construction material for road works. Without alteration in collection process, the C&D waste should be kept sorted according to its nature in landfill site to keep its characteristics as homogeneous as possible. Moreover, specific tests performed in this thesis confirmed the viable construction properties of this material such as non-plasticity and bearing capacity that conform to the South African construction standard. The suitability of the C&D materials in civil works is further demonstrated by the analysis of the rubble generated by the deconstruction of the Natal Command, an ex-military area, in Durban. The demolition of the study area has followed a rigorous procedure of deconstruction. This approach allowed the principal components of the waste (Concrete and Masonry) to be kept separated. Laboratory tests accurately assessed the geotechnical properties of concrete, masonry and of a blend of them which were previously identified as suitable aggregates for unbound road base or sub-base layers. These materials are considered as A1a in AASHTO classification and as G4 in COLTO classification. In addition to the standard test of characterisation, the risk of polluting the environment was assessed. An instrumented embankment was built in accordance with South African road compaction standards using blend material. This enabled the verification of the behaviour of C&D material in real-word working conditions. The instrumentation recorded the stresses, strains and moisture at three depths of the embankment during the passage of trucks at different predetermined speeds. The results of the monitoring were analysed and correlated to the results coming from the full performance material characterization carried out in laboratory. This study will thus enhance knowledge of the behaviour of C&D material and also provide a useful tool to the designer in the planning stages as well as information for contractors involved in C&D road construction application.
Application of a quantitative precipitation estimation algorithm for the s-band radar at Irene, South Africa.
(2014) Becker, Erik Hermanus.; Pegram, Geoffrey Guy Sinclair.
Flash floods are the number one cause of death and damage with regard to natural disasters in South Africa (Poolman, 2009). Thus, the South African Weather Service (SAWS) and the National Disaster Management Centre (NDMC) embarked on a collaborative project for the implementation of the South African Flash Flood Guidance system (SAFFG) in flash flood prone regions (de Coning & Poolman, 2011). The SAFFG is dependent on accurate precipitation estimates from radars and therefore much emphasis has been placed on the performance of the Quantitative Precipitation Estimation (QPE) fields. Weather radars offer the public efficient means of measuring precipitation remotely. Although the measurements are indirect radar remains the best alternative in capturing the spatial variability associated with precipitation at high temporal and spatial resolutions. A methodology proposed by Chumchean et al., (2006) was selected to be implemented and compared against the existing radar precipitation field of the Gematronik 600S S-band Doppler radar at Irene, South Africa. The methodology proposes a process that includes a rainfall classification algorithm. This algorithm separates convective from stratiform precipitation with the intent to assign different Z-R relations to the two different types of rainfall (Chumchean, et al., 2008). A technique for smoothing accumulations was also included into the algorithm, which is based on optical flow techniques (Bowler, et al., 2004). Reflectivity data from the Irene radar together with in situ rain gauge data within a 300 km radius of the radar location were obtained for the South African summer rainfall season from October 2010 to March 2011 for evaluation of the QPE field. One and twenty-four hour accumulations were compared to the corresponding rain gauge totals and the resulting evaluation scores are compared to the existing precipitation field to determine any improvements. The study showed that by applying specific Z-R relationships to both convective and stratiform precipitation yields better results than using a single relationship only. Smoothing the precipitation with optical flow vectors further decreases the QPE error at both one and twenty-four hour accumulations. Overall the dual Z-R relationship with the optical flow smoothing yields the smallest error and is an improvement from the previous algorithm.
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.
Application of multi-criteria decision analysis integrated with GIS and air pollution model inputs for schools site selection.
(2019) Abera, Yared Getachew.; Kumarasamy, Muthukrishnavellaisamy.
Schools site selection is an essential process which needs knowledge of different fields. The process involves scientific justification, judgment and a finding of suitable land, which consider financial, social, ecological and political perspectives, that limit conflicts and supports agreement among the decision makers. Lack of scientific analysis may negatively impact on the economy, health, and safety of the public. However, reports revealed that finding of school location managed without utilization of scientific analysis thus prompted the development of schools in unsuitable areas and caused pupils to face several problems such as long walking distance, heavy traffic, presentation to sound and air pollution (Bukhari et al., 2010). Addis Ababa is the largest city in Ethiopia, and the city needs additional schools to meet the minimum pupil section ratio as per the national standard to improve education excellence (CGAAEB, 2018). Currently, most of the existing schools placed in the central part of the city; thus such scientific analysis is vital to give insight for the decision makers and planners to improve the site selection process for new schools, to provide a fair distribution of education access and utilizing a limited available resource. Nowadays, the application of GIS and Remote sensing datasets widely used to support the site selection process. In this study GIS integrated with MCDA and Remote Sensing, techniques have been used to select suitable school locations. MCDA is a tool that devoted to improving the decision-making process using various qualitative and quantitative criteria goals or objectives of a contradictory nature. This study attempts to use an air pollution model integrated with Remote Sensing, Geographical Information System (GIS) for Multi-Criteria Decision Analysis (MCDA) to identify optimal sites for new schools. The MCDA was done using Analytical hierarchy process (AHP), which classify criterions in hierarchical level and assigns a relative weight to each criteria using pairwise comparison. The selected criteria in this study decompose into three main groups, namely Economy, Accessibility, and Environmental Safety. Besides, Landsat 8 OLI/TRIS satellite image was used to quantify the annual mean concentration of Particulate matter with diameter 10 μm (PM10) for Environmental safety criteria. Subsequently, using Weight overlay tool, the criteria maps combined based on their relative influence, which is obtained from AHP to produce the final map, and the map reclassified as not suitable, less suitable, suitable and most suitable, using Arc GIS 10.4 reclassify tool. The resulting map of the annual mean concentration of PM10 shows that the concentration amounts on airports, factories, and road structures are high. The criteria weights obtained are 54%, 30% and 16% for Economy, Environmental Safety, and Accessibility respectively. The ultimate suitability map shows that 3.89% of the study area is most suitable, 57.47% is suitable, 38.48% is less suitable, and 0.08% is unsuitable, the most suitable areas laid on the city’s north-east and south-east part, which are away from existing schools. Therefore, this study successfully suitability model has been used to allocate an optimal place for new schools to be built in Addis Ababa capital using GIS integrated MCDA with Air pollution model input.
The application of pole mounted amorphous core transformers to the electrical distribution network.
(2017) Naidoo, Jasoda.; Swanson, Andrew Graham.
With the drive to save money when supplying electricity to customers, utilities are looking for solutions to decrease losses on distribution lines while maintaining good quality of supply. Amorphous core transformers are known for having the lower no-load losses compared to cold rolled grain orientated transformers and hence may be an important technology to decrease losses on the distribution network. The amorphous material is easily magnetised, however this comes at the expense of a lower saturation point and the transformer may need to be designed at a lower peak flux density. Inrush currents are a phenomenon that occurs when a transformer is switched on. The combination of the voltage switching angle and the remnant flux lead to an overflux and subsequent saturation of the core material, this leads to a high current. The purpose of this dissertation is to investigate the performance of amorphous core transformers installed on distribution lines, where they are switched onto the network from the high voltage side, and conclude if they are a suitable replacement for cold rolled grain oriented steel core. Inrush currents have been investigated through a circuit model developed in Alternative Transients Program/Electromagnetic Transients Program (ATP/EMTP) to determine the currents for various designs of transformers. The model consists of the non-linear component related to the core used as well as the air core of the high voltage winding. The circuit model has been validated through an experiment. A study was undertaken to understand the difference in the forces between amorphous core transformers and cold rolled grain orientated, this was investigated in Finite Element Method Magnetics (FEMM) by determining the distribution of magnetic flux. Additionally, as the inrush current is only seen on the high voltage winding and not the low voltage winding, the models were compared to the forces due to short-circuit currents, where there is current on both high voltage and low voltage windings and a different magnetic flux distribution. The position of the tap winding was of interest as it results in an unsymmetrical force distribution.
An assessment of carbon emissions reduction potential through zero waste activities in South African municipalities.
(2010) Jagath, Rohini.; Trois, Cristina.
The inception of global warming has resulted in mitigation efforts across all relevant sectors. Waste management activities produce approximately 12% of methane emissions in South Africa. The current scope of waste management favours sustainable strategies targeting zero waste and waste diversion, however landfill disposal of municipal solid waste (MSW) is still the primary strategy employed by South African municipalities. This study evaluated the greenhouse gas (GHG) impacts of various waste management scenarios that included recycling, composting, anaerobic digestion, and landfill gas recovery through case studies of the eThekwini Municipality (Mariannhill landfill) and uMgungundlovu District Municipality (New England Road landfill) MSW streams. Each waste management strategy was assessed on the basis of GHG emissions, landfill space savings and economic feasibility. A waste stream analysis (WSA) was conducted to obtain both the qualitative and quantitative data required. The results of the WSA determined that the biogenic fraction of the MSW stream for typical South African municipalities varies between 32-40% while the recyclable fraction ranges between 38-44%. The Waste Resource Optimisation Scenario Evaluation (WROSE) model was developed for the quantification of GHG emissions and is based on the US EPA emissions factors for landfill disposal, landfill gas recovery, recycling and composting. An emissions factor was derived to include the GHG impacts of anaerobic digestion using a streamlined life cycle analysis approach. The results confirmed that recycling, anaerobic digestion and composting all produce GHG reductions, in comparison with the baseline scenario of landfill disposal, and a combination thereof through Mechanical Biological Treatment (MBT) produced the greatest net GHG reductions (between -63,338 to -71,522 MTCO2e/annum for the New England Road MSW stream, and -71,280 to -86,123/annum MTCO2e for the Mariannhill MSW stream). The results indicated that the implementation of MBT scenarios would produce landfill space savings of 94,375 to 103,302 m3 for the Mariannhill landfill, extending the landfill lifespan by 12-14 years, while savings of 73,399 – 74,100 m3 could be realised for the New England Road landfill, extending the landfill lifespan by 2-3 years. The study concluded that while the focus of waste management has changed and zero waste/waste diversion goals require alternative waste management methods to be implemented, the capital and operational costs of some technologies are the main barrier for implementation in developing countries, and that the environmental and social benefits should be evaluated further to truly gauge the costs/benefits involved.
Assessment of heavy metal contamination in soils around Krugersdorp mining area, Johannesburg, South Africa.
(2020) Mkhize, Thabani Armstrong.; Friedrich, Elena.
The mining industry remains a driving force of the South African economy, making a significant contribution to economic activity, job creation and foreign exchange earnings. However, in the process of mining and mineral production, millions of tons of waste are produced making this sector the potential source of air, soil and water pollution. There are more than 270 waste dumps known as tailing dams in the Witwatersrand Basin alone, covering 400 square kilometres in surface area (Oelofse et al., 2007, Rosner, 1999). Poor management of these tailing dams and waste rock dumps lead to uncontrolled release of acid mine drainage that in some cases cause soil degradation and water contamination around these sites. The aim of this study was to assess pollution levels of As, Cd, Cu, Cr, Pb, Hg, Ni and Zn in soils from the mining area of Krugersdorp and to compare them with the South African and international standards. The geo-accumulation index (Igeo), the single ecological risk factor (Er), and potential risk index were calculated to assess the degree of contamination by these metals in soils. Thirty one soil samples were collected from eleven different sites around the Krugersdorp area. Twenty three were collected from the Krugersdorp Game Reserve, four from private farmland, two from Mintails Gold Mine and two from Rand Uranium Mine. All collected samples were properly marked and identified by their sampling locations using a Global Positioning System (GPS). Samples were acid digested using microwave oven according to U.S EPA 3052B protocols and analysed for arsenic (As), cadmium (Cd), copper (Cu), chromium (Cr), lead (Pb), mercury (Hg), nickel (Ni) and zinc (Zn) with Inductively Coupled Plasma – Optical Emission Spectrometry technique (ICP-OES). The concentration levels of heavy metals in soils were in the range of 4.1-155.5 mg/kg for As, 0.1-0.7 mg/kg for Cd, 13.4-119.1 mg/kg for Cu, 54.0-147.0 mg/kg for Cr, 0.02-1.36 mg/kg for Hg, 24.1-168.9 mg/kg for Ni, 5.5-82.5 mg/kg for Pb, and 12.5-641.0 mg/kg for Zn. Three sampled sites (KS7, KS8 and KS10) recorded high contamination levels by heavy metal compared with the relevant South African standard and other international standrads. The geo-accumulation index assessment revealed that the soils vary between uncontaminated to the extreme pollution soil category. The ecological risk factor (Er ) mean values of As, Cd, Cr, Pb and Zn revealed low ecological risk to soils, while values for Cu and Hg indicated moderate ecological risk. Ni values indicate a considerable ecological risk. The potential ecological risk index (RI) values of three sites (KS1, KS5, and KS9) indicated low ecological risk. RI values for KS3, KS6 and KS11showded that these sites posed moderate ecological risk. Considerable ecological risk was displayed by sites KS2, KS4 and KS8, while RI values of site KS7 and 10 displayed very high ecological risk. These results indicate that the anthropogenic mining activities have polluted the area with heavy metals. As a result a series of recommendation are forwarded in order to rehabilitate the quality of the soils affected.
Assessment of permeable reactive barriers alternative media for the remediation of nitrate-contaminated ground-waters.
(2013) Zorgani, Abdulmutaleb Esseid.; Trois, Cristina.
The increase in the contamination of ground-water (GW) with nitrates in both developing and developed countries mainly results from agricultural activities and improper sanitation systems, and is a recent phenomenon that has become a source of great health concern, particularly in regions where people rely on the ground-water as their primary water source. Due to the advantages of using Permeable Reactive Barriers (PRB) including its cost-effectiveness as well as its capability to remove or mitigate the spread of large spectrum of contaminants (including nitrates), a significant increase has been observed in the use of this subsurface treatment technology compared to other methods. However, identifying more economic and reliable reactive media to be used instead of the costly conventional PRB materials is now of key importance. Two local soils namely Berea Red Sand (BRS) and Umgeni Sand (US) were the main focus of this research. In addition to these soils, Zero Valent Iron (ZVI) was also used in this study. Through the use of batch experiments the feasibility of the nitrate reduction was investigated by five substrates including 100% ZVI, 100% BRS, 100% US, mix of 75% ZVI + 25% BRS, and mix of 50% ZVI + 50% BRS. Five concentrations of nitrate synthetic solution including 10 mg/l, 25 mg/l, 50 mg/l, 100 mg/l, and 500 mg/l were used to simulate nitrate-contaminated ground-water. All the batch experiments were performed under semi-aerobic and uncontrolled pH conditions, and only one solid/liquid ratio of 1:10 was used. The two mixes (mix of 75% ZVI + 25% BRS, and mix of 50% ZVI + 50% BRS) exhibited a nitrate removal efficiency of 100%, with all the different initial concentrations that were used with it; besides these two mixes, none of the other substrates showed this performance. 100% ZVI; however, managed complete nitrate reduction when the 10 mg/l and 25 mg/l concentrations were used. Finally, it was concluded that the benefits of using BRS in combination with other materials such as ZVI in the PRB field are promising.
An assessment of radar, gauge and kriged gauge rainfall data in Free State, South Africa.
(2019) Gutsa, Tadiwanashe Simpson.; Kumarasamy, Muthukrishna Vellaisamy.; Pegram, Geoffrey Guy Sinclair.
In the last decades, flooding has caused significant damages and death in South Africa. Flooding is associated with heavy rainfall events which vary largely in space and time. The forecast of such phenomena requires quality rainfall data to generate output with a reasonably high degree of confidence. This study aims to document the difference of rainfall estimates derived from radar, rain gauge and a kriged rain gauge network. A review on the use of weather radar in hydrological studies shows that there is an opportunity of using radar estimates in near-real time flood forecasting and warning applications. The quality of radar rainfall estimates is assessed using pluviometer rain gauges and a daily kriged rain gauge surface in the Vaalsub-catchment in the Free State, South Africa. The study uses data from the MRL5 S-band radar located at Bethlehem and from rain gauges within weather stations operated by South African Weather Services (SAWS). The analysis assesses the effect of rainfall seasonality, radar range dependencies and storm variation on the quality of estimated rainfall accumulations. In addition,gauge density is analysed to determine the effect it has on the performance of kriging estimation.During the research notable spatial rainfall variation and areas with quality radar estimates have been identified. The results show that there exists a seasonal bias between radar and rain gauge estimates with the radar underestimating low intensity gauge rainfall pronouncedly during the winter rainfall events by an average of 31%. The underestimation of rainfall by the MRL5 radar increases as we move away from the radar tower. During the summer rainfall events the radar estimates are almost similar to point gauge estimates especially during late summer (February and March) . Radar underestimation of winter rainfall is probably due to overshooting of the tops of stratiform rainfall by the radar beam. Correlations are high between MRL5 radar and rain gauges during summer rainfall events ranging between 0.7 and 1. Results from this study provide information to guide on the application and selection of rainfall estimation techniques.
An assessment of the strength and durability characteristics of recycled plastic pavers.
(2022) Maharaj, Kiash.; McLeod, Christina Helen.; Friedrich, Elena.
The generation of waste is reaching record highs and displays a consistent uptrend over the last decade, and despite high generation rates, landfilling is still the dominant disposal method for waste in South Africa. However, these materials may have potential for reuse in several applications, and industries are considering their viability. One such industry is the construction and engineering industry, which has seen an increase in research into the application of waste materials. This study explores the use of HDPE, PP, and glass waste as an alternative material for making concrete pavers. The study uses local waste materials to assess the density, durability, and mechanical strengths of the resulting paver, called Eco-pavers, and compares them to regular concrete pavers for accuracy. The pavers are made of a 50/50 blend of recycled plastic and glass aggregate, which has not been widely studied as a replacement for cement or stone aggregate. The Eco-pavers demonstrate a low water absorption rate of 0.28%, compared to the 4.5% of concrete pavers. After immersion testing in various chemicals over a 180-day period, the pavers show no signs of degradation either structurally or visually. The Eco-pavers are suitable for use as impermeable pavers, as they did not allow any infiltration during the permeability test. The flexural strength assessment resulted in an average breaking stress of 7.9 MPa, which is greater than the prescribed minimum. However, the pavers' average compressive strength is 12.47 MPa, which is below the minimum criterion of 35 MPa for pavers, and therefore needs improvement. In summary, this study explored the use of recycled plastic and glass waste in manufacturing Eco-pavers as an alternative to traditional concrete pavers. The resulting pavers demonstrated low water absorption, chemical resistance, and impermeability, making them suitable for impermeable applications. However, the compressive strength of the pavers needs improvement. While their short-term use is unlikely to release microplastics, further research is needed to determine their long-term impact.
An assessment of water services in a peri-urban area of Umtata.
(2001) Ntuli, MzwaBantu.; Otieno, Fredrick Alfred Ochieng.
No abstract available.
The breaching of temporary open/closed estuaries.
(2007) Parkinson, Michael.; Stretch, Derek Dewey.
Intermittent breaching of sand barriers at temporary open estuaries plays a key role in the functioning of these systems. Breaching events lead to large and rapid changes in the physico-chemical environment which in turn triggers major biological responses. The breaching process can cause significant morphological changes as strong breach outflows can scour large quantities of accumulated sediments from an estuary. Simple laboratory experiments are reported that investigate the temporal evolution of the breach and the scaling of the breach characteristics namely the breach width W, volume Vb, formation time Tf and peak outflow Qp. The experiments were specifically designed to investigate the influence of the outflow volume S, the hydraulic head H and the barrier breadth B on the breach characteristics. The breach width W was found to be proportional to S1/3, whilst the breach volume Vb was found to be proportional to HBS1/ 3. The breach formation time Tf was found to be proportional to (g/S1/3)-1/2 (H/S1/3)-3/2 (B/S1/3)1 and the peak outflow Qp was found to be proportional to (gS5/3)1/2 (H/S1/3)3/2 (B/S1/3)-1. These scalings are also shown to be consistent with observed breach characteristics for actual estuaries and earth dam failures where outflow volumes are typically six orders of magnitude larger than for the models.

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