Theses and dissertations (Engineering and Built Environment)

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Alcohols conversion over transition metal based catalyts
(2018) Ndebele, Mthobisi Sbonelo; Isa, Yusuf Makarﬁ
Ethanol and butanol obtainable through fermentation of lignocellulose biomass have become promising alternative feedstock for production of fuels as they are biodegradable and sustainably regenerated via the photosynthesis cycle. The properties of hydrocarbons produced through alcohol conversion closely resemble those of gasoline. Catalytic systems are reported to play a vital role during alcohol conversion to hydrocarbons. In this study ethanol and butanol were used as a feedstock for production of hydrocarbons over Fe, Zn and Ni catalyst systems supported on zeolite ZSM-5 (Zeolite Socony Mobil-5) and activated carbon (AC). X- Ray Diffraction (XRD), Scanning Electron Microscope (SEM) coupled with Energy- dispersive X-ray spectroscopy (EDS) and Brunauer, Emmet, and Teller (BET) analyses were employed for catalyst characterization. XRD patterns confirmed the success of metal doping on ZSM-5 and activated carbon supports. Major peaks at 7.96° and 23.97° corresponding to ZSM-5 crystals were observed in ZSM-5, and AC was found to be amorphous. Impregnation with metals reduced the crystallinity of ZSM-5 supported catalysts. Whereas SEM analysis showed that catalysts supported on ZSM-5 exhibited irregular shapes and catalyst supported on activated carbon exhibited disordered structures. The BET analyses confirmed that the surface areas of promoted catalysts decreased after metal doping. Evaluation of the catalysts were carried out in a ½ inch stainless steel reactor at 400 °C and atmospheric pressure with a weight hourly space velocity (WHSV) of 2.5 h-1 (g feed)/ (g catalyst). The ZSM-5 support performed better than activated carbon support. More than 90% conversion was achieved over catalysts supported on ZSM-5. Production of hydrocarbons over catalysts supported on activated carbon were as a result of the active component. Conversion of feedstock was observed to produce more benzene, toluene and xylene (BTX) compounds with an increase in butanol content. 100% conversion was achieved with pure butanol and not more than 99.86% conversion was achieved with pure ethanol. Catalyst systems supported on HZSM-5 and activated carbon were successfully synthesised. Ethanol, butanol and ethanol-butanol mixtures were successfully converted to liquid hydrocarbons and the conversion was greater than 90%. On the promoted catalysts, production of BTX were suppressed and various metals were observed to perform differently.
The application of lean principles to mitigate greenhouse gas emissions in an automotive industry
(2020-09) Ramsunder, Keshav; Olanrewaju, Oludolapo Akanni
A common factor for industrial production is energy, and the level of energy consumed is typically used to measure the growth and economic development of countries. However, as the industrial sector expands and makes efforts to gain competitive advantage, there is a growing concern regarding energy consumption and the ecological burden related to energy use. Thus far, industry has relied on the Lean manufacturing paradigm to gain the contemporary benefits of profitability, flexibility, and increased efficiency. More recently, the association of Lean manufacturing and environmental impacts has grown in both the industrial and academic fields. The main aim of this research is to investigate the correlation between lean tools and their effect on Green House Gas emissions, ultimately measuring environmental performance. The research is quantitatively based and entails the study of a weld process production line at Toyota South Africa Motors. The environmental impacts of the production process were observed and measured before and after the implementation of three lean tools: Value Stream Mapping (VSM), Total Productive Maintenance (TPM) and Standardized Work. Comparing the outcomes, the study found significant differences in the pre-test and post-test of each lean technique applied. VSM allows one to visualize and magnify the environmental performance of the process, which allows for simple quantifying of environmental metrics. TPM brings to light that equipment that is regularly maintained to operate at optimum condition reduces non-value adding energy usage. However, in contrast, Standardized Work has shown minimal benefits within the context of this research. The findings of this research are beneficial as they contribute to gaining a better understanding of the way lean tools affect environmental performance. While the study contributes to the current body of knowledge, it can also enlighten Small to Medium Enterprises, practitioners and larger organizations to rethink current strategy and allow for simultaneous implementation of Lean Green operations.
Assessing the feasibility and effectiveness of rooftop rainwater harvesting in Winnie Mandela Madikizela Local Municipality
(2023-05) Nakin, Abongile Ongezwa; Walker, Mark; Ikegwuoha, DC
South Africa's primary source of water is surface water. The potability of this water is doubtful especially in rural areas. Evaluation of rainwater quality from various roof materials is crucial. Additionally, there is a need to evaluate the quantity and the economic viability of Rooftop Rainwater Harvesting (RRWH). Winnie Madikizela Mandela Local Municipality (WMMLM) of Nomlacu currently has 73.6% municipal water supply backlog. With the current challenges, it is important not only to explore ways to save water but also to generate own sources of water. This makes RRWH systems as a viable water resource, an option for alleviating water scarcity. The study aims to assess the feasibility and effectiveness of RRWH for domestic use in WMMLM. The target is to determine the potential of rainwater harvesting as a potable water supply and conservation alternative. Hydrological data was obtained from the Weather SA to facilitate the calculation of the quantity of rainwater that can be harvested per household. Moreover, catchment areas were obtained through QGIS to determine size and materials of the roof types. Thus, to analyse the impact of roof materials on water quality for human consumption and irrigation. According to the results obtained in this study, Turbidity and E. coli produced noncompliant results of (0.8 – 2.8 NTU) and (0 - >2420 MPN /100mL) respectively. Although within limits, Aluminium, Colour, and Zinc concentrations present higher values on zinc metal roof compared to tiled roofing material. This is due to the high radiation and good heat conducting capacity of the metal. Results also showed higher pH levels on tiled roofs (7.05 – 7.39) compared to zinc roofs (6.27 – 7.19), which is in line with the nature of concrete. The most significant and immediate threat to health that roof collected water poses is bacterial contamination. Therefore, it is important to regularly clean the system, use disinfection solutions like chlorine tablets and boiling water before consumption. Overall, Nomlacu area receives relatively high amounts of rainfall which is greater than country’s annual rainfall. The study showed that RRWH can meet the annual demand of rainwater and have an overflow of roughly 7211L/year which is equivalent to an approximate potential annual harvest of 124% when utilized to its optimal potential and at worst case scenario can alleviate the pressure from the municipal water supply system by at least 81%. Results showed that optimal rainwater harvesting can be achieved by using more than two storage tanks per household. This then makes it possible for the system to alleviate pressure from the municipal water supply. On the economically aspect, installing a RRWH system is financially feasible, it would spare the municipalities approximately 48.8% of the municipal water supply spend to supply water to the municipality should this project be a government initiative.
An assessment of the adoption of smart building concept in the Nigerian construction industry
(2022-05-13) Ejidike, Cyril Chinonso; Mewomo, M. C.
Technological penetration across developing countries has impacted the construction industry, with more construction stakeholders deploying various technologies into the building lifecycle's design, construction, management, and maintenance. The building sector has evolved by adopting and implementing smart tools for its operations over the past few years. Building information modelling (BIM), the internet of things (IoT), and smart devices (sensors) are game-changers that have helped to reduce the complexity of construction activity and increase productivity. Meanwhile, introducing the sustainable development concept in the construction industry has enabled the proper management of the earth's natural resources and provided a pathway for ecosystem balance alongside socio-economic development. Amid the skyrocketing population growth, urban sprawl, and globalization, the building industry is confronted with the challenge of providing adequate and holistic built infrastructures such as efficient energy management, good water supply, occupants' indoor comfort, and the management of construction waste. The smart building concept (SBCs), which employs sustainable construction whereby the built product is constructed according to best practices, including efficient energy use, the recycling of raw material, and the realization of a sustainable and carbon-free environment, has demonstrated the digitalization of sustainable development in the construction industry. Therefore, this dissertation seeks to asseeement of the adoption of smart building concepts in the Nigerian construction industry. The research poses the following questions: 1) What is the awareness level of construction professionals in the adoption of the smart building concept (SBCs) in the Nigerian construction industry? 2) What factors can enhance the awareness of the smart building concept among construction professionals in the Nigerian construction industry? 3) What factors enhance the adoption of SBCs among professionals in the Nigerian construction industry? 4) What are barriers to adopting SBCs in construction projects in the Nigerian construction industry? A random sampling technique in selecting the construction professionals. The total population of construction professionals within the study area is 5,108, comprising construction professionals of Architects, Builders (Mechanical, Electrical, and Structural), Engineers, and Quantity Surveyors practicing in Lagos state. The sample size selection was made using the Yamane formula (1967) for calculating sample size. Therefore, the sample for this study is 363. A well-structured questionnaire of 363 was administered to construction professionals to gather relevant data on the topic. The data collected were analyzed using the Kruskal Wallis H test and weighted mean, factor analysis, and binary regression analysis, and mean item score and agreement analysis technique. The key finding of the research indicated that construction professionals are generally aware of the smart building concept. Administration, education, organizational, and environmental factors were discovered to enhance the adoption of smart building concepts among construction professionals. Furthermore, the research indicates that energy and cost-saving, job creation, safety and security, and health care are the critical factors enhancing in adoption of smart building concepts among construction professionals in the Nigerian construction industry. Lastly, the research result discovered that the high cost of smart building materials, inadequate power supply, resistance to change from the use of traditional technology, poor maintenance culture, poor knowledge of smart building technology, inadequate well-trained labour in the practice of smart building construction, and inadequate finance schemes are the significant barriers to the adoption of smart building concept. Based on this research finding, the research recommends that construction professionals engage more in smart building concepts, propagating the country's awareness and development of smart building construction. Furthermore, the government should establish a common platform for the collaboration of all stakeholders, such as professionals in the construction industry and academia, by way of policymaking and funding of research and development towards implementing these smart technologies. It will go a long way for employment creation and improve the country's economy. This study contributes to the body of knowledge by discovering the critical factors that will aid the successful adoption of the smart building concept in the Nigerian construction industry.
Automatic detection of melanoma in dermoscopic images of skin lesions
(2023-05) Jooravan, Amith; Reddy, Seren
Melanoma, which is an aggressive form of skin cancer, has the highest mortality rate of all skin cancers, especially if there is a late diagnosis. The diagnosis of melanoma is usually conducted in two stages; initially an invasive biopsy of a skin lesion under concern is conducted and subsequently the respective removed tissue undergoes laboratory analysis. A crucial component of the first stage is the highly subjective process of determining which skin lesions require a biopsy. The biopsy process may be painful, costly and time consuming, however in healthcare, a case of false positive may result in a patient being unnecessarily alarmed, while a case of false negative, a type-2 error that does not detect a positive case, may have dire consequences. This is owing, in the main, to the survival rate of melanoma being correlated to the stage of the cancer when first diagnosed. This research proposes a non-invasive method to assist with the reduction of false negative classifications associated with skin lesions that are considered as benign candidates instead of melanoma. In this research, 218 dermoscopic images from the Interactive Atlas of Dermoscopy dataset were used. The selected lesions were in early stages of melanoma, being in situ or less than 0,76mm thick. Of these, 178 were used for training and 40 for testing. The training and test dataset were balanced, comprising a 50/50 split, for melanoma and non-melanoma cases. Three classification algorithms were considered in this research; these include k-nearest neighbours (KNN), Naïve Bayes and linear support vector machine (LSVM). To identify potential candidates of skin lesions for biopsy, the algorithms consider the asymmetry, border, colour, and diameter of the skin lesions; this is referred to as the ABCD rule. This research proposes the use of a LSVM machine learning algorithm to classify a skin lesion as being either melanoma or non-melanoma with a view of minimising false negative rate of the investigated classification algorithms. Classification accuracy of 87.5% and a false negative rate of 5% is achieved.
Bioremediation of acid mine drainage and crude contaminated soils
(2020-09) Anekwe, Ifeanyi Michael; Isa, Yusuf Makarﬁ
Pollution is one of the greatest ills plaguing the existence of the ecosystem which could lead to the annihilation of terrestrial and aquatic habitat if not remedied. Acid mine drainage (AMD) and crude oil are among the major land and water pollutants cause by industrial and human activities. The constant exploration, mining, and processing of mineral resources and prevalent use of petroleum products for economic purposes have contributed to contamination of soil and proximate water bodies which results in environmental degradation; thus, remediation becomes necessary. The treatment of AMD contaminated soils using the conventional methods has some room for improvement to meet the remediation purpose. Bioremediation technology provides a sustainable and eco-friendly approach to the treatment of contaminants. This study aims to evaluate the performance of different potential bioremediation techniques and conduct a comparative analysis of these methods for the treatment of AMD and crude oil-contaminated soils. The treatment approach for both pollutants comprises of soils separately contaminated with AMD and crude oil before the application of bioremediation techniques. For the biostimulation study, contaminated soils were amended with varying ratios of the brewery or municipal wastewaters (BWW and MWW), while the bioventing (BVT) treatment involved wastewater amendment and supply of atmospheric air from the vadose zone at 3L/min at 30 minutes intervals every 48 hours. The bacteria strain Pseudomonas aeruginosa ATCC 15442 used for the study which was inoculated at 5%(w/w) was cultured in two different media for respective treatments and wastewater was amended as an extra energy source for bioaugmentation (BAU) study while Bioattenuation (BAT) which received no amendment was used as a control treatment for the study. The treatments were conducted in plastic bioreactors under mesophilic conditions for 28 days and samples were collected from each treatment system on weekly basis to analyse for sulfate, heavy metals, and total petroleum hydrocarbon (TPH) reduction. The result of the study showed that the amendment of contaminated soils with wastewater increased alkalinity in the system which enhanced microbial activities for effective remediation which recorded 52.43 and 51.23% average TPH and metal removal efficiency for the BSTc treatment. Also, the combined application of bioremediation techniques was more effective than single application as the introduction of oxygen into the treatment system with wastewater amendment increased the TPH and metal removal efficiency by an average of 12.98 and 13.17% respectively but efforts to enhance sulfate removal by air-injection (BVTa) proved abortive with 17.20 and 14.67% removal efficiencies less than BSTa and BAUa respectively as sulfate-reducing bacteria thrive in an anaerobic environment. However, P. aeruginosa ATCC 15442 adopts the sorption process in the reduction of hydrocarbon and metal toxicity with 42.02 and 41.81% average removal efficiencies respectively and the amendment extra nutrient (wastewater) increased the removal efficiency of these pollutants by 25.24 and 16.23% respectively. The results of the study inferred that wastewater (BWW and MWW), air-injection and P. aeruginosa ATCC 15442 showed great potentials in the degradation and removal of TPH, metals and sulfate contaminants, hence, can serve as a viable strategy for the remediation of AMD and crude oil polluted soils while improving waste management and amelioration of pollution aftermath faced by communities involved in mining and oil production and/or processing. There is a need for optimization to ensure effective remediation while further study is required to validate large scale application.
The biosorption of chromium and copper from AMD contaminated water using banana peels as a biomass adsorbent
(2022-09-29) Mzimela, S'thembile; Musonge, Paul; Bakare, Babatunde F.
The presence of heavy metals in water from industrial activities negatively affects human health. Metal accumulation in human bodies is toxic and can lead to carcinogenic effects when consumed for prolonged periods. There is no acceptable method for permanently removing heavy metals in water. As a result, water for human consumption and domestic use from various water sites contains harmful heavy metals. This study investigates the removal of hexavalent chromium (Cr6+) and copper (Cu 2+) from drinking water through the adsorption process using banana peels as biomass material. Banana peels were evaluated for their ability to remove heavy metals from water as a cheaper alternative resource to conventional adsorbents such as activated carbon. Cr6+ and Cu2+ are some of the most common heavy metals found in potable (drinking) water and they were chosen for this study amongst other heavy metals. Batch studies were conducted using water that was synthesized with the chosen metals. Parameters such as pH, agitation speed, biosorbent dose, initial metal concentration, and contact time were varied to determine their effect on biosorption. pH was varied between 2 and 7, agitation speed was varied between 100 and 200 rpm, dosage was varied between 1 and 6 grams, initial concentration was between 5 and 100 mg/L and contact time was also varied between 5 and 140 minutes. Each variable was done one factor at a time while keeping other values constant. The height of the column for column studies was studied between 5 and 30 cm at constant pH “4”, 5mg/L initial metal concentration and volumetric flowrate of 4mL/min. Results from the study showed that pH for both Cr6+ and Cu2+ was highest at pH “4” with % removal of 65% and 94%, respectively. Agitation speed had a high % removal at 180 rpm for Cr6+ (67%) and 160 and 180 rpm for Cu2+ (95%). Increase in biosorbent dose also increased biosorption efficiency from 17% to 95% for Cu2+ across the range, and from 58% to 65% for removing Cr6+ . In the study of initial metal concentration, banana peels performed better at lower metal concentrations for both metals. Highest % removal efficiency for Cr6+ was found at 5 mg/L at 64% and for Cu2+ at 10, 15 and 20 mg/L at 95%. Contact time between 5 and 140 minutes found that equilibrium was reached within 30 minutes for Cr6+ and within 50 minutes for Cu2+ . Adsorption equilibrium isotherms and kinetics were studied for both metals and found that the biosorption of Cr6+ followed the Freundlich isotherm and Langmuir isotherm models with R 2 of 0.99 and 0.95 respectively, and the process kinetics followed the pseudo-second-order kinetic reaction with R 2 of ~ 1. The biosorption of Cu2+ followed the Langmuir isotherm model with R 2 of 0.96 and Langmuir qm of 15.41 mg/g and the process kinetics followed the pseudo-first-order kinetic reaction as well as the intra-particle diffusion model with both R 2 of 0.98. Banana peels were characterized for their properties and the Fourier transform infrared (FTIR) spectroscopy identified the functional groups in the peels which were hydroxyls, carboxylic acids, alkanes, and amines. Most of the groups were active in the removal of Cr6+ and Cu2+. The scanning electron microscopy (SEM) identified the surface of the peels to be rough with uneven areas and the energy-dispersive x-ray spectroscopy (EDS) analysis identified the elements present in the peels which were carbon (C), oxygen (O), potassium (K), chloride (Cl) and silicon (Si). The x-ray diffraction (XRD) was used to identify the phase of the peels and it was found that the peels were amorphous with some crystallinity containing a crystal salt called sylvite. The Brunauer–Emmett–Teller (BET) analysis identified the pores of the banana peels to be mesoporous with a pore size of 2.9 nm, a surface area of 5.69 m2 /g, and a pore volume of 0.002605 cm3 /g. Column experiments in a fixed-bed column were studied for the removal of Cr6+ and the breakthrough time tb increased from 10 min at 5cm to 420 min at 30 cm. The mass transfer zone HB also increased from 0.206 at 5 cm to 7.426 at 30 cm. Other column performance indicators such as the adsorbent exhaustion rate (AER) and the number of volumes processed (NBV) showed that biosorption was efficient and dependent on bed height for better performance. The process favoured the Adams-Bohart model with R2 ranging between 0.94 to 0.98 and the Yoon-Nelson model with R2 ranging between 0.93 and 0.97. It can be concluded from this study that banana peels have the ability of removing Cu and Cr in potable water and has provided some insight for scaling-up of adsorption columns.
Biosorption of Fe2+ from potable water using natural and modified sugarcane bagasse
(2023-05) Ndebele, Nompumelelo Lindi Gelsiah
Even though some metals are crucial for the health and development of human bodies, their presence in higher concentrations is worrisome because it has a detrimental effect on people's health. These heavy metals cause cancer and cannot be broken down by biological processes. The removal of heavy metals from water using traditional techniques; such as reverse osmosis, precipitation, ion exchange; has been the subject of extensive investigation. However, because these processes are so expensive to run, a lot of research is currently focusing on using agricultural biomasses to remove these heavy metals. Dumping of this agricultural waste (sugarcane bagasse) in landfills creates dangers of spontaneous combustion, because of microbial activities. The functionality of circular economy depends on waste resources being utilized to their fullest potential, with almost no production of recoverable waste. In a circular economy, sugarcane bagasse is utilized as a fuel source for the boilers that generate process steam and electricity in the sugar mill facilities. Sugarcane bagasse is used in the manufacturing of paper and paper goods, as well as in the agricultural sector. Stakeholders across the value chain, from product design to waste management, This study fulfils the functionality of the circular economy where it looks at extracting the valuable components of the sugarcane bagasse, then further using the sugarcane bagasse to remove heavy metals from potable water. In this study, the adsorption capacities of unmodified and modified sugarcane bagasse for removing Fe2+ from potable water were investigated in batch experiment studies. Sugarcane bagasse comprises cellulose, hemicellulose and lignin. In order to determine the effect of removing/ extracting each component from the sugarcane bagasse, sugarcane bagasse was pretreated with different concentrations of sodium hydroxide and sulphuric acid, ranging between 0.5 wt% and 2.5 wt%, predominantly used to extract lignin and hemicellulose. A cellulosic structure was left behind after the simultaneous removal of both amorphous components (the lignin and the hemicellulose) using the combined pretreatments of sodium hydroxide and sulfuric acid. The advantages of extracting or eliminating these components came from their high value in many sectors. Lignin is used in the paper business and costs between R11 300 and R17 420 per ton, hemicellulose is used in the pharmaceutical sector and costs between R500 and R1000 per ton, and cellulose is utilized in the textile sector. The concentrations of all chemical pretreatments used on the sugarcane bagasse ranged from 0.5 to 2.5%, with alkaline pretreatments intended to extract lignin, acid pretreatments intended to extract hemicellulose, and combination pretreatments intended to remove both lignin and hemicellulose. While cellulose content increased from 32.02 to 65.65% after sodium hydroxide pretreatment, lignin and hemicellulose content reduced from 22.30 and 24.30% to 7.56% and 13.63%, respectively. Lignin and hemicellulose concentration for the sulphuric acid pretreatment went from 22.30 and 24.30% to 14.90% and 13.63%, respectively, while cellulose content went from 35.02 to 65.65%. After the sugarcane bagasse underwent chemical pretreatments, batch studies were conducted on both the natural and chemically pretreated sugarcane bagasse in order to determine how the removal of lignin, hemicellulose, and cellulose affected the performance of the biosorbents in the biosorption of Fe2+ from drinkable water. To assess the efficacy of natural and modified sugarcane bagasse on the Fe2+ removal, the operational parameters investigated in the batch experiments were initial concentration ranging from 1 to 30 mg/L; pH ranging from 2 to 7, contact time ranging from 5 -100 minutes, and adsorbent dose ranging from 0.2 to 1.4 g. For every variation investigation, one variable was varied at a time while keeping the other variables constant. The experimental runs done were repeated thrice and average values are reported throughout the study. According to the biosorption results, 1% NaOH was the best performing biosorbent for the alkali-pretreatment. The most effective biosorbent for the acidpretreatment variation was 2.5% H2SO4. The optimal combination for the pretreatment was (0.5% NaOH + 0.5% H2SO4). Regarding initial concentration variations, all biosorbents were most effective at a concentration of 1 mg/L, where natural sugarcane bagasse was able to remove 50% of Fe2+, 1% NaOH was able to remove 99.7% Fe2+, 2.5% H2SO4 removed 75.93% Fe2+, and the combined-pretreated biosorbent of (0.5% NaOH + 0.5% H2SO4) removed 87.17% Fe2+ . The increase in biosorbent dose led to an increase efficiency of the natural and chemically pretreated biosorbents. The highest removal of Fe2+ was obtained at 1 g (both for the natural and for all the pretreated biosorbents), with 32.2% for the natural; 79.04% for the 1% NaOH; 58.79% for the 2.5% H2SO4 and 70.73% for (0.5% NaOH + 0.5% H2SO4). Results of the study also showed that the highest removal of Fe2+ for the pH variation of 2-7 was at pH “6” for both the natural and pretreated biosorbents. For the variation of the agitation speed, the highest Fe2+ removal was at 160 rpm with 52% Fe2+ removal for the natural sugarcane bagasse. The Langmuir and Freundlich adsorption isotherms were used to study the biosorption mechanisms. Good correlation coefficients (R 2 ) of > 0.95 were obtained for both the Langmuir and Freundlich isotherms for both the natural and modified sugarcane bagasse, indicating that the biosorption followed both homogeneous and heterogeneity interaction between Fe2+ ions and active functional groups of the surface and pores of the biosorbents. Biosorption results for the natural sugarcane bagasse best fitted with the Langmuir isotherm with qmax of 0.770 mg/g, R 2 of 0.987 and RL of 0.938. The alkali and acid-pretreated biosorbents favoured both the Langmuir and Freundlich isotherms with R 2 > 0.95; RL < 1 and 1 𝑛 < 1. The highest qmax of 9.199 and 5.743 mg/g was obtained at 1% NaOH and 2.5% H2SO4, respectively. The combined pretreatment fitted best with only the Langmuir isotherm with R 2 of 0.987, the R 2 of the Freundlich isotherm was less than 0.9. The biosorption of Fe2+ followed both the pseudo-first-order and pseudo-second-order kinetic reactions with 𝑞𝑒(𝑒𝑥𝑝) in close proximity to 𝑞𝑒(𝑐𝑎𝑙𝑐) and R 2 > 0.9. These results showed that sugarcane bagasse had great adsorption capacity after removing the valued components, namely, lignin and hemicellulose. Characterization studies, which included FTIR, XRD, BET and SEM, were also carried out on the natural and pretreated bagasse before and after adsorption experiments. FTIR confirmed the existence of carbonyl, hydroxyl and carboxyl functional groups as major groups responsible for the adsorption of Fe2+ onto the natural and pretreated sugarcane bagasse. XRD revealed that the natural structure of the sugarcane bagasse was of native cellulose consisting of both amorphous and crystalline regions; this structure became more crystalline after the chemical pretreatments as the crystallinity index increased from 39.04% to 66.85% at 1% NaOH; 57.47% at 2.5% H2SO4; and 57.92% at (0.5% NaOH + 0.5%H2SO4). The natural sugarcane bagasse structure featured rough surfaces, according to SEM data, and the main constituents were silicon (Si), carbon (C), and oxygen (O). According to the BET data, employing 1% NaOH, 2.5% H2SO4, and (0.5% NaOH + 0.5% H2SO4), respectively, the initial surface area of 0.904 cm3 /g rose to 1.503, 1.233, and 1.376 cm3 /g and the pore size of 56.33 ̊A increased to 99.63, 93.680, and 99.10 ̊A. According to the EDS data, sodium hydroxide pretreatment performed better in terms of adsorption, followed by combined pretreatment and sulphuric acid. The natural sugarcane bagasse, 1% NaOH, 2.5% H2SO4, and (0.5% NaOH + 0.5% H2SO4) were able to biosorb 0.77, 7.89, 1.63, and 3.8% Fe2+, respectively.
Characterisation of concrete with expanded polystyrene, eggshell powder and non-potable water : a case study
(2023-05) Mncwango, Bonke; Allopi, Dhiren
Urbanisation has brought many benefits but it has also highlighted the global lack of housing alongside global natural resource scarcity. Lack of housing on the surface appears to be a singular problem, however in reality it represents a number of society’s biggest challenges such as crime, pollution (as a result of inadequate waste disposal strategies), unhygienic living conditions, as well as numerous health problems. Governments across the world have made various attempts at addressing the issue of lack of housing, including embarking on large scale social and public housing initiatives, building smaller homes for the homeless, as well as removing certain regulatory barriers to allow more houses to be built at a reduced timeframe. These advances have assisted many individuals and families globally, however, there are still many individuals and families that government housing-aid or housing initiatives have not yet reached. These individuals and families are faced with solving their housing crisis on their own, with their own resources. Globally, concrete remains a supreme building material in the construction industry and therefore is a primary factor of consideration for solving the housing crisis, especially for those who have no financial assistance or aid from government. Concrete’s composition is simple: cement, fine aggregate, coarse aggregate and water. The intricate interaction between all four components is meant to stand the test of time. Unfortunately, it is not only the earth’s diminishing natural resource reserves which are causing a decline in the popularity of conventionally produced concrete, but it is also the irreparable harm that it is causing to the environment. The process of concrete production requires large volumes of cement, and cement remains one of the biggest producers of carbon dioxide. Carbon dioxide is a greenhouse gas which in excessive amounts creates a cover that traps the sun’s heat energy in the atmosphere. Another major criticism of conventional concrete is the requirement that it be produced with clean water which is of a drinkable standard. This criticism is justified when considering the extreme water shortages that are experienced by many low to middle income countries around the world. The amount of financial and human resources that local authorities invest in cleansing water to bring it to a drinkable standard is often overlooked. It is obvious that it is less expensive to use water directly from a river in its natural state than using it after it has undergone numerous cleansing processes by local authorities. There have been a notable number of advances in making concrete more resource-efficient and environmentally friendly. These include the advent of lightweight concretes such as expanded polystyrene concrete. Expanded polystyrene concrete not only saves the amount of aggregate that would normally be required in conventional concrete, it also has excellent acoustic and thermal properties, thereby reducing energy consumption which in turn saves money. However, even with such excellent properties, expanded polystyrene concrete still fails to address two of concrete’s major criticisms which are related to the amount of cement used as well as the amount of clean potable water required for mixing. Therefore, by building on the qualities of expanded polystyrene concrete, this research investigates the potential of lowering the amount of cement required in a concrete mix through the use of eggshell powder. Eggshells are a waste product found everywhere in the world and are readily available in almost limitless quantities. The use of eggshells in concrete to lower the amount of cement required will not only achieve a reduction in the amount of carbon dioxide that is produced in the process of producing concrete, it will also assist in contributing toward solving the escalating waste disposal crisis that currently exists for many waste types such as eggshells. It is common for communities to reside close to a river or a natural flowing watercourse, so this research included river water as a variable. Four different concrete mix scenarios were tested to ascertain through experimentation whether the strength properties of concrete that contains expanded polystyrene, eggshell powder and natural river water in various proportions could in any way compare to a conventionally produced concrete mix. In order to comprehensively study material behaviour in this case, sieve analysis, bulk density, fineness modulus, moisture content as well as specific gravity tests were performed on all aggregates used. Furthermore, in order to achieve the required analytical depth for the materials being studied, x-ray diffraction and energy dispersive spectroscopy tests were conducted. As a means of conducting further trend analysis on the different experimental mixes, logarithmic regression models were developed. Through analysis of the output attained from the aforementioned strategies, this research study found that when cement was substituted by eggshell powder at a percentage of 5 % and simultaneously when coarse aggregate was also substituted by expanded polystyrene at a percentage of 5 %, all mixed with non-potable water, the compressive and flexural strength outcomes marginally differed from the strength outcomes of conventionally produced concrete. Furthermore, the substitution of stone by EPS at a percentage of 10 % when mixed with river water was comparable to the substitution of stone by EPS at a percentage of 10 % when mixed with potable water. The results showed that there was a difference of not more than 1.4 MPa and 0.3 MPa in compressive and flexural strength respectively amongst the averages obtained at each age tested. Study results show that the substitution of potable water by non-potable water reduced both the compressive and flexural strength of the concrete when the mix did not contain eggshell powder. However, when eggshell powder was included in the mix, the strength outcomes of the compressive and flexural strength of the concrete mix was comparable to that of conventionally produced concrete. There may be many reasons why it is important to not deviate from convention in the production of numerous products such as concrete; nevertheless, the value of experimentation as demonstrated in this research is that experimentation can give rise to a variety of innovations accompanied by a wealth of solutions to the environmental and socio-economic issues that the world is currently faced with.
Chemical oxygen demand (COD) fractionation for process modelling considerations and optimization
(2021-03) Jwara, Thandeka Yvonne Sthembile; Musonge, Paul; Bakare, Babatunde F.
Wastewater treatment is a critical chain in the urban water cycle. Wastewater treatment prevents the toxic contamination of water bodies. The notable consequences of contamination are the loss of aquatic life, upsurge of eutrophication due to nutrient overload, and potential loss of human life as a result of waterborne diseases. Wastewater works (WWW) are therefore an intrinsic component of protecting the urban water cycle and ensuring that water resources are preserved for future generations. The operation of a WWW is subject to compliance with the national legislative requirements imposed by the Department of Water and Sanitation (DWS) to ensure the preservation of water resources. These requirements oblige water and sanitation departments to employ innovative design, control and optimization of WWW. Wastewater modelling packages have presented the opportunity to simulate the wastewater treatment processes in order to maintain and sustain legal compliance with the DWS. The successful implementation of a simulation package for wastewater process optimization and modelling depends on an accurate characterization also known as fractionation of the organic fractions of the WWW influents. This thesis is a result of a comprehensive study reported for Darvill wastewater work. Darvill WWW is a 60 ML/D plant which has been receiving flows of up to 120 ML/D. The importance of the study was to motivate for the upgrade of the wastewater work to account for the increased hydraulic, organic and nutrient loading into the plant. The study looked at the application of the World Engine for Simulation and Training (WEST) and all studies required to generate data that will serve as input with the understanding the current state of Darvill WWW in terms of performance. The study presents the fractionation outcomes of the primary wastewater effluent organic matter as chemical oxygen demand (COD) and the performance by assessing the biological nutrient removal process (BNR) using BNR efficiencies in addition to the development of the Darvill WWW WEST model with the aid of the probabilistic fractionator. The fractionation was achieved through the oxygen uptake rate experiments using the respirometry method. Experiments yielded the following results: biodegradable COD (bCOD) (70.5%) and inert COD (iCOD) (29.5%) of the total COD. Further characterization of the bCOD and iCOD yielded the readily biodegradable fraction (SS) at 75%, slowly degradable (XS) at 25%, particulate inert (XI) was 50.8% and the inert soluble SI at 49.2%. The COD fractions were used and served as input to the development and evaluation of the Darvill WEST model. Calculations of BNR efficiencies were used to evaluate the effects of high inflow to the biological treatability of the activated sludge for the period September 2016 - November 2017. It was found that at inflows above design capacity, the nutrient removal efficiency reduced from an expected 80-90% to an average of 40% with an average soluble reactive phosphorus (SRP) removal efficiency being 64%. A data input file for the period of January – June 2016 was created to serve as input into WEST to develop a baseline average model for the Darvill WWW plant. The model results predicted a mixed liquor suspended solids (MLSS) concentration of 6475 mg/L for the plant during the study period this was comparable with the plant MLSS concentration of 6700 mg/L at the time which was above the design concentration of 4500 mg/L. This was largely due to the plant operating under nutrient overload conditions. The final effluent (FE) concentration in the defractionation model was found to be COD = 41.28 mg/L, ammonia (NH3) = 22.02 mg/L, Total Suspended Solids (TSS) = 32 mg/L, SRP = 2.16 mg/L. Most of these results were expectedly non-compliant to the discharge limits imposed by the DWS with the exception of COD. The plant FE measurements were COD = 45.1 mg/L, NH3 = 3.4 mg/L, TSS = 20.9 mg/L, SRP= 6.67 mg/L. The COD and TSS prediction were comparable to the model prediction however there were limitations in the models ability to predict NH3 and SRP. The model does not account for changes in dissolved oxygen (DO) and temperature as these parameters are kept constant for the purpose of this study. The model assumes a temperature of 20 oC and a DO concentration of 2 mg/L for the aerobic reactor, 0.01 mg/L for the anaerobic reactor and 0.1 mg/L for the anoxic reactor. The model assumes that with the nutrient overload, oxygen compensation occurs within the reactor to maintain a constant DO concentration within the units. This limits the model in the prediction of actual instance where the overload would deplete the DO and where other competing reactions would give rise to greater non-compliances as well as biological growth’s impairment due to cold weather conditions.
Comparative study of anammox-mediated nitrogen removal in three reactor configurations
(2021-05-27) Kosgey, Kiprotich Eric; Pillai, Sheena Kumari Kuttan; Kiambi, Sammy Lewis; Bux, Faizal; Chandran, Kartik
Anaerobic ammonium oxidation (ANAMMOX) is an efficient and cost-effective process developed for biological nitrogen removal from wastewater. However, widespread application of the ANAMMOX process for wastewater treatment remains constrained due to the slow growth of ANAMMOX bacteria, propensity for out-competition by fast growing microbes, and its sensitivity to environmental and operational conditions. Consequently, understanding the influence of mixing conditions in different reactor configurations on this process is paramount in its improvement. This study focused on the comparative analysis of ANAMMOX-mediated nitrogen removal in a hybrid up-flow anaerobic sludge blanket reactor (H-UASB), moving bed biofilm reactor (MBBR) and a gas-lift reactor (GLR). The study involved experimental study of nitrogen removal, bacterial population dynamics and physical properties of the bacterial biomass within the reactors, as well as the description of process performance and the growth of nitrifying and ANAMMOX bacteria in the reactors using a calibrated mechanistic model. All the reactors were operated for 535 days using the same synthetic feed under anaerobic conditions. K1-type carrier materials were added to each reactor for biofilm development. The concentrations of ammonium (NH4 + ), nitrite (NO2 - ) and nitrate (NO3 - ) in the effluent from the reactors were determined colorimetrically. Among the three reactors, MBBR displayed the highest nitrogen removal efficiency (NRE) during the study (66±36%), and contained the lowest concentration of free ammonia (FA) (19±22 mg-N/L) and free nitrous acid (FNA) (0.001±0.001 mg-N/L). In comparison, the NRE and the concentrations of FA and FNA in H-UASB during the study were 63±28%, 91±41 mg-N/L and 0.006±0.004 mgN/L, respectively, while in the GLR, they were 54±39%, 28±29 mg-N/L and 0.002±0.002 mg-N/L, respectively. Based on the ratios of NO2 - consumed to NH4 + consumed, and the ratios of NO3 - produced to NH4 + consumed, the start-up of ANAMMOX process was faster in the MBBR (144 days) compared to H-UASB (193 days) and GLR (272 days). MBBR also displayed less fluctuations in the NREs and nitrogen removal rates (NRRs) during the study compared to H-UASB and GLR. The microbial communities in the suspended biomass in the reactors were characterised using high-throughput sequencing on an Illumina MiSeq platform on days 125, 192, 260, 309 and 535, while the microbial communities in the biofilms were only characterised on day 535 (last day) due to slow biofilm development. Gradual increases in the relative abundance of ANAMMOX bacteria were observed in the suspended biomass in all the reactors between days 125 and 309, which corroborated the observed increases in the NREs. The relative abundance of ANAMMOX bacteria remained consistently higher in H-UASB during the study than in MBBR and GLR. On the contrary, the highest relative abundance of ammonia oxidising bacteria (AOB) was observed in the suspended biomass in the MBBR on day 125 at approximately 38%, while the highest relative abundance of nitrite oxidising bacteria (NOB) and complete ammonia oxidising (COMAMMOX) bacteria was recorded in the suspended biomass in the MBBR at approximately 30% and 5%, respectively. In all the reactors, the relative abundance of AOB in the biofilms and the suspended biomass was comparable on day 535. In addition, on day 535, higher relative abundance of NOB was observed in the biofilms in both GLR and H-UASB at approximately 7% compared to the suspended biomass, while their abundance in the suspended biomass in the MBBR was comparable to that recorded in the biofilms. Furthermore, in both H-UASB and MBBR, higher relative abundance of ANAMMOX bacteria was observed in the suspended biomass compared to the biofilms on day 535, while comparable abundance was observed in the GLR. The highest total microbial diversity (Shannon and Simpson indices) and evenness (Pielou’s Evenness) was observed in the suspended biomass in the MBBR. Granulation of the suspended biomass was observed in both GLR and H-UASB, while the suspended biomass in the MBBR was flocculent. In the MBBR, the colour of the biomass had turned brown on day 125, while the biomass in H-UASB and GLR on this day was tawny and dark-tawny, respectively. However, on day 309, the biomass in all the reactors had turned red, corroborating the highest relative abundance of ANAMMOX bacteria observed during the study. Faster attachment of biomass on the carrier materials in MBBR was observed in the course of study compared to H-UASB and GLR. On the last day, the concentrations of the biomass on the carrier materials in the MBBR was also higher (12 mg/carrier) in the MBBR than in the H-UASB (8 mg/carrier) and GLR (10 mg/carrier). Activated sludge model 1 (ASM 1), which was modified by separating the activities of Nitrospira spp. from those of Nitrobacter spp. as well as by adding both ANAMMOX and COMAMMOX bacterial activities, was used to describe process performance in the reactors. The modified ASM 1 was able to predict the trends in the effluent concentrations of NH4 + , NO2 - and NO3 - in all the reactors. In addition, the correlation of the actual relative abundance of nitrifying and ANAMMOX bacteria, with the model-predicted relative abundance, was positive. The model also indicated higher heterotrophic activities in both GLR and MBBR compared to H-UASB, an indication that continuous mixing in MBBR and alternation of plug-flow conditions with internal gas circulation in GLR favoured heterotrophic bacterial growth. However, the model was limited in predicting the fluctuations in bacterial abundance and the fluctuations in the effluent concentrations of NH4 + , NO2 - and NO3 - in the reactors. The obtained results indicate that better-mixed conditions in the MBBR led to comparable relative abundance of nitrifying bacteria between the biofilms and the suspended biomass, while plug-flow conditions in the H-UASB favoured ANAMMOX bacterial growth in the suspended biomass and the nitrifying bacterial growth in the biofilms. The alternation of internal gas circulation with plug-flow conditions in the GLR also favoured the growth of nitrifying bacteria in the biofilms. Overall, nitrogen removal in H-UASB was likely dominated by ANAMMOX process, while nitrogen removal in MBBR and GLR was as a result of combined ANAMMOX and sequential nitrification-denitrification processes. The novelty of this study stem from the impact of mixing conditions on process performance and microbial ecology of ANAMMOX-mediated systems.
The construction, development and evaluation of a portable ferro- precipitator
(1994) Sunjka, Ivan; Coertze, Dirk J.; Rawlins, Mark
This dissertation is concerned with the construction of the locally developed Ferro-precipitator which can be utilised outside a laboratory environment. The American developed Ferrograph machine, besides being expensive (R42 000 + GST in 1984), can only be used inside a dust free, temperature controlled room. As lubricants in machinery moving parts play an important role in their performance and durability many methods of evaluating the health of machines have been devised, but none by themselves can give a complete picture of what is happening inside the machine. Various methods of oil analysis have been studied in this dissertation for comparison and/or complementary purposes, so as to establish the role of the Ferro-precipitator in the context mentioned. Spectrometric, Debris and Radio Tracer methods are based on quantitative aspects of wear particle analysis, whereas the Magnetic Plug method shows visibly large wear particles in the very high wear pattern range. A further aspect to consider is the fact that the Spectrometric analysis method, which is the most common and comprehensive method available in South Africa, is laboratory orientated. This means that an oil sample has to be taken from a machine and then sent to a laboatory for analysis. Besides being time consuming from the time the samples are taken to the time when the results are known, the Spectrometric analysis method is also very expensive. The Ferro-precipitator that has been developed, is sensitive to particle size and to the rate at which these particles are generated. This is due to the phenomenon that a varying magnetic field strength will attract different size ferrous particles accordingly. This concept was validated by manufacturing ferrous particles of various sizes, firstly by grinding and secondly by sieving. These particles, in both cases, were passed through the Ferro-precipitator in a medium of oil, and graphs of density versus distance along the slide were plotted. The graphs showed distinct variations between particle sizes. The manufactured particles were also statistically evaluated by establishing the correlation between the machined and/or the sieved particles to the optically measured particles. The sensitivity of the Ferro-precipitator was further demonstrated by comparing results obtained from an engine test carried out under controlled conditions using the Spectrometric method. If developed further, the Ferro-precipitator .could, be used in the field, which would eliminate the time lost due to samples being sent ot a laboratory. Also the cost of the machine would be a fraction of the price of the Ferrograph and/or the Spectrometer. An in-depth study of particle morphology can be carried out on the wear particles deposited on the slide, with the aid of a Scanning Electron microscope using its X-Ray attachment. The potential for such a study was demonstrated on the engine test performed for this dissertation.
Crash modeling of a light composite aircraft
(2014) Moletsane, Moeletsi Augustinus; Jonson, David
ABSTRACT The study presented here was focused on the crash analysis of light composite aircraft on relatively survivable accidents. The crash analysis approach was based on the numerical simulation using the finite element software (MSC.Dytran). The aircraft crash environment, impact terrain, impact angles and material properties were identified, and later introduced into the aircraft crash model. The background on composite materials is discussed and more focus was given to their response at high strain rates. The modeling methodology is also discussed with more emphasis on the finite element analysis approach and the failure theories behind composite materials. The failure criteria are based on assumptions considered for the classical lamination theory, and each of the failure theories in MSC.Dytran were evaluated before being introduced into the crash model. The Tsai-Wu failure criterion was found to be capable of predicting the progressive ply failure of the composite lamina. The Ravin 500 light composite aircraft model was used for the purpose of this study and four crash scenarios of impacting the aircraft onto the soil model were considered. The aircraft was impacted at the same crash velocity but different flight path angles were considered. The 10⁰, 15⁰, 20⁰ and 30⁰ crash angles together with a crash velocity of 22m/s were used. The impact approach was influenced by the previous literature; it shows that the structural damage of an aircraft during crash accident is affected largely by the crash angle. The results of each crash scenario are presented and mainly focused on the failure response of the aircraft structure. The conclusion on the crashworthiness of the Ravin 500 light composite aircraft is also drawn based on the numerical work. Details regarding the future work or recommendations for the design philosophy and means of improving the crashworthiness of the light composite aircraft are also presented. In addition, more emphasis is focused in the occupant’s space within the aircraft.
Crashworthiness analysis of a composite light fixed-wing aircraft including occupants using numerical modelling
(2017) Evans, Wade Robert; Jonson, Jon David; Walker, Mark
The development and validation of reliable numerical modelling approaches is important for higher levels of aircraft crashworthiness performance to meet the increasing demand for occupant safety. With the use of finite element analysis (FEA), development costs and certification tests may be reduced, whilst satisfying aircraft safety requirements. The primary aim of this study was the development and implementation of an explicit nonlinear dynamic finite element based methodology for investigating the crashworthiness of a small lightweight fibre reinforced composite aircraft with occupants. The aircraft was analysed as it crashed into soft soil and the FEA software MSC Dytran was selected for this purpose. The aircraft considered for the purposes of this study was based on a typical four-seater single engine fibre-reinforced plastic composite aircraft. The definition of a survivable accident is given by Coltman [1] as: “an accident in which the forces transmitted to the occupant through his seat and restraint system do not exceed the limits of human tolerance to abrupt accelerations and in which the structure in the occupant’s immediate environment remains substantially intact to the extent that a liveable volume is provided for the occupants throughout the crash sequence”. From this definition, it was determined that the FEA models must primarily provide an assessment on the crashworthiness of the aircraft in terms of the structural integrity of the airframe to ensure a minimum safe occupant volume and the tolerance of humans to abrupt (de)accelerations. An assessment of other crashworthiness factors have been ignored in this study, such as post-crash hazards (e.g. fire) and safe egress for the occupants. Stockwell [2] performed a dynamic crash analysis of an all-composite Lear Fan aircraft impacting into concrete with the explicit nonlinear dynamic finite element code MSC Dytran. The structural response of components was qualitatively verified by comparison to experimental data such as video and still camera images. The composite fuselage materials were represented with the use of simplified isotropic elastic-plastic material models, and therefore did not account for the anisotropic properties of composite materials and the associated failure mechanisms. The occupants were represented as lumped masses; therefore occupant response could not be investigated. Malis and Splichal [3] performed a dynamic crash analysis of a composite glider impacting into a rigid surface with MSC Dytran; however further model verification was required. The 50th percentile adult male (occupant of average height and mass) Hybrid III anthropomorphic test device (ATD), also referred to as a crash test dummy, was represented in the analyses with the Articulated Total Body (ATB) model integrated within MSC Dytran. Various injury criteria of the ATB model were evaluated to determine the crashworthiness of the glider. Bossak and Kaczkowski [4] performed global dynamic crash analyses of a composite light aircraft crash landing. Representative wet soil, concrete and rigid impact terrains were modelled using Lagrangian-based finite element techniques and only the vertical velocity component of the aircraft was considered to simplify analyses. It was assumed that the previous use of only a downward vertical velocity component was a result of possible numerical instabilities which commonly occur with the use of Lagrangian solvers when considering problems with large deformations, which is a characteristic of crash analyses (i.e. the addition of a horizontal velocity component may result in severe element deformation of the soft soil terrain, resulting in premature analysis termination). Analyses of the occupant were performed in separate local models, using accelerations derived from the global analyses results. The real-time interactions between the occupant and aircraft therefore could not be investigated, which is considered a major disadvantage. Impact analyses of helicopters into water were performed by Clarke and Shen [5], and Wittlin et al. [6]. Both these papers showed promising results with the use of Eulerian-based finite element techniques to model the water. Additionally, combined horizontal and forward velocity components were assigned to the fuselages with success. It must be noted that the fuselages were modelled as rigid bodies; therefore the effect of structural failure on analyses could not be investigated. Fasanella et al. [7] performed drop tests of a composite energy absorbing fuselage section into water using Eulerian, Arbitrary Lagrange Eulerian (ALE) and Smooth Particle Hydrodynamics (SPH) meshless Lagrangian-based finite element techniques to represent water. Successful correlation between experimental and numerical data was achieved; however, structural failure could not be modelled with the Eulerian-based finite element technique due to analysis code limitations at the time. A “building block” approach was used in this study to develop accurate numerical modelling techniques prior to the implementation of the full-scale crash analyses. Once the blocks produced satisfactory results in themselves, they were then integrated in order to achieve the abovementioned primary aim of this study. The sub-components (or blocks) were the occupant (viz, FEA of the human bodies’ response to impact), (FEA of) soft soil impact and (FEA of) fibre-reinforced plastic composite structures. This approach is intuitive and provides key understanding of how each sub-component contributes to the full-scale crash analyses. Published literature was reviewed, where possible, as a basis for the development and validation of the techniques employed for each sub-component. The technique required to examine the dynamic response of an occupant with MSC Dytran, integrated with the ATB model, was demonstrated through the analysis of a sled test. The numerical results were found to be comparable to experimental results found in the literature. An Eulerian-based finite element technique was implemented for soft soil impact analyses, and its effectiveness was determined through correlation of experimental penetrometer drop test results found in the literature. An investigation into the performance of the Tsai-Wu failure criterion to capture the onset and progression of failure through the layers of fibre reinforced composite laminates was conducted for an impulsively loaded unidirectional laminate strip model. Based on the results obtained, the techniques implemented for each sub-component were deemed valid for crashworthiness applications (viz. to achieve the project aim). Full-scale crash analyses of impacts into rigid and soft soil terrains with varying aircraft impact and pitch angles were investigated. Typical limitations encountered in previously published works were overcome with the techniques presented in this study. The aircrafts’ laminate layup schedule was explicitly defined in MSC Dytran, thereby eliminating the inherent inaccuracies of using isotropic models to approximate laminated composite materials. The aircraft was assigned both horizontal and vertical velocity components instead of only a vertical component, which increased the model accuracy. Numerical instabilities, due to element distortion of the terrain when using a Lagrangian approach, were eliminated with the use of an Eulerian soft soil model (Eulerian techniques are typically used to model fluids where large deformations occur, which is a characteristic of crash analyses). Structural failure was successfully implemented by coupling Lagrangian and Eulerian solvers. The ATB model allowed for the real-time interactions between the occupant and aircraft to be investigated, unlike previously where analyses of the occupant were performed in separate local models using accelerations derived from the global analyses results. The results obtained from the crash analyses provide an indication of the forces transmitted to the occupant through the seat and restraint system, and the aircraft’s ability to provide a survivable volume throughout the crash event. The explicit nonlinear dynamic finite element based methodology was successfully implemented for investigating the crashworthiness of small lightweight composite aircraft, satisfying the primary aim of this study. Chapter 1 provides a review of fibre reinforced composite materials, the finite element method (FEM), ATDs and associated analysis codes, human tolerance limits to abrupt (de)accelerations, and crash dynamics and environment. The review of the FEM initially focuses on the fundamentals of FEA and then on the features specific to MSC Dytran as it is used throughout this study. Chapter 2 discusses the development of suitable numerical modelling techniques at the sub-component level and the implementation of these techniques within the full-scale crash analyses. Chapter 3 presents and discusses the full-scale crash analyses results for three impacts into rigid terrain and three impacts into soft soil terrain with varying aircraft pitch and impact angles. The results obtained from the crash analyses provide an indication of the forces transmitted to the occupant through the seat and restraint system, and the aircraft’s ability to provide a survivable volume throughout the crash event. Chapter 4 provides a conclusion of the work performed in this study and highlights various areas for future work.
Decomposition of methane into carbon and hydrogen over Ni-Li/CaO catalysts
(2018) Musamali, Ronald Wafula; Isa, Yusuf Makarﬁ
Overdependence on fossil-based fuels and their effect on environment is a global concern by energy stake holders. Bulk of present day hydrogen comes from gasification of coal, steam reforming and partial oxidation of hydrocarbons. Steam reforming accounts for over 50% of world hydrogen production despite producing carbonaceous gases which are harmful to the environment and poisonous to both; proton exchange fuel cells and alkaline fuel cells. Natural gas is a preferred feed for hydrogen production, because it is abundantly available on earth. Catalytic decomposition of ammonia can produce clean hydrogen but ammonia itself is an air pollutant. Catalytic decomposition of methane into carbon and hydrogen is an attractive option to producing clean hydrogen because its products are carbon and hydrogen. In this work, five different catalysts comprising of varying quantities of nickel and lithium, supported on calcium oxide were synthesized by incipient wetness impregnation method and designated according to weight % as; 30%Ni/CaO, 37.5%Ni-12.5%Li/CaO, 25.0%Ni- 25.0%Li/CaO, 12.5%Ni-37.5%Li/CaO and 50%Li/CaO. The synthesized catalysts were characterized by (XRD, SEM, BET and TEM) and tested for methane decomposition. From the XRD patterns of the synthesized catalysts, distinct crystalline phases of CaO and NiO were positively identified in 50%Ni/CaO according to their reference JCPDS files. Introduction of Lithium hydroxides improved the crystalline structure of the Ni/CaO catalyst. SEM analyses of the catalyst material using Image-J software confirmed that all catalyst materials were nanoparticles ranging from 3.09-6.56nm. BET results confirmed that, all the catalysts are mesoporous with pore sizes ranging from 20.1nm to 45.3nm. Introduction of LiOH to Ni/CaO generates mesoporous structures by destructing the lattices of the CaO structure during the formation of Ni-Li/CaO species. Particle size distribution in TEM analyses revealed that, a higher nickel loading in the catalyst favours the formation of carbon nanotubes while higher lithium hydroxide loading favours the formation of carbon fibres (CF). Low yield of carbon fibres from methane decomposition on unsupported Ni catalyst in 50%Ni/CaO was attributed to the presence of large Ni particles with low index planes which were incapable of dissociating the unreactive methane molecule. The aim of this work was to synthesize a catalyst for use in decomposition of methane into carbon and hydrogen, that addresses drawbacks of traditional solid metal catalysts such as sintering and coking. From the experimental results, 37.5%Ni-12.5%Li/CaO catalyst recorded 65.7% methane conversion and 38.3%hydrogen yield while 50%Ni/CaO recorded the lowest methane conversion of 60.2% and a hydrogen yield of 35.7% at 650℃. Outstanding performance of the 37.5%Ni-12.5%Li/CaO catalyst is attributed to the incorporation of lithium hydroxide which provided more catalyst active sites and a molten environment for proper dispersion of the nickel metal. The solid 50%Ni/CaO catalyst readily deactivated due to coking unlike the supported molten 37.5%Ni-12.5%Li/CaO catalyst in which methane decomposition reaction took place by both surface reaction and chemisorption.
Development and evaluation of woven fabric immersed membrane bioreactor for treatment of domestic waste water for re-use
(2014) Cele, Mxolisi Norman; Rathilal, Sudesh; Pillay, Visvanathan Lingamurti
Increased public concern over health and the environment, the need to expand existing wastewater treatment plants due to population increase, and increasingly stringent discharge requirements, have created a need for new innovative technologies that can generate high quality effluent at affordable cost for primary and secondary re-use. The membrane biological reactor (MBR) process is one of the innovative technologies that warrant consideration as a treatment alternative where high quality effluent and/or footprint limitations are a prime consideration. MBR processes have been applied for the treatment of industrial effluent for over ten years (Harrhoff, 1990). In this process, ultrafiltration or microfiltration membranes separate the treated water from the mixed liquor, replacing the secondary settling tanks of the conventional activated sludge process. Historically, energy costs associated with pumping the treated water through the membranes have limited widespread application for the treatment of high volumes of municipal wastewater. However, recent advancements and developments in membrane technology have led to reduced process energy costs and induced wider application for municipal wastewater treatment (Stephenson et al., 2000). This report describes a small and pilot scale demonstration study conducted to test a woven fabric microfiltration immersed membrane bioreactor (WFM-IMBR) process for use in domestic wastewater treatment. The study was conducted at Durban Metro Southern Wastewater Treatment Works, Veolia Plant, South Africa. The main objective of this project was to develop and evaluate the performance of an aerobic woven fabric microfiltration immersed membrane bioreactor (WFM-IMBR) for small scale domestic wastewater treatment. The experiments were oriented towards three sub objectives: to develop the membrane pack for immersed membrane bioreactor based on WF microfilters; to evaluate the hydrodynamics of WF membrane pack for bioreactor applications; and to evaluate the long-term performance and stability of WFM-IMBR in domestic waste water treatment. The literature was reviewed on membrane pack design for established commercial IMBR. The data collected from literature was then screened and used to design the WF membrane pack. Critical flux was used as the instrument to measure the WF membrane pack hydrodynamics. Long-term operation of the WFM-IMBR was in two folds: evaluating the performance and long term stability of WFM-IMBR. The membrane pack of 20 flat sheet rectangular modules (0.56 m by 0.355 m) was developed with the gap of 5 mm between the modules. The effects of parameters such as mixed liquor suspended solids or aeration on critical flux were examined. It was observed that the critical flux decreased with the increase of sludge concentration and it could be enhanced by improving the aeration intensity as expected and in agreement with the literature. Hence the operating point for long term subcritical operation was selected to be at a critical flux of 30 LMH and 7.5 L/min/module of aeration. Prior to the long term subcritical flux of WFM-IMBR, the operating point was chosen based on the hydrodynamic study of the WF membrane pack. The pilot scale WFM-IMBR demonstrated over a period of 30 days that it can operate for a prolonged period without a need for cleaning. Under subcritical operation, it was observed that there was no rise in TMP over the entire period of experimentation. Theoretically this was expected but it was never investigated before. Good permeate quality was achieved with 95% COD removal and 100% MLSS removal. The permeate turbidity was found to be less than 1 NTU and it decreased with an increase in time and eventually stabilized over a prolonged time. Woven fibre membranes have demonstrated great potential in wastewater treatment resulting in excellent COD and MLSS removal; low permeate turbidity and long term stability operation. From the literature surveyed, this is the first study which investigated the use of WF membranes in IMBRs. The study found that the small scale WFM-IMBR unit can be employed in fifty equivalence person and generate effluent that is free of suspended solids, having high levels of solid rejection and has acceptable discharge COD for recycle. Future work should be conducted on energy reduction strategies that can be implemented in WFM-IMBR for wastewater treatment since high energy requirements have been reported by commercial IMBRs.
Development and validation of a pilot juice extractor technique to process green sugarcane with brown leaf
(2020-03-12) Balkissoon, Simiksha; Rathilal, Sudesh
Annually, approximately 90% of the sugarcane planted in South Africa is burnt prior to harvest. The burning of sugarcane is a pre-harvesting technique that is well known to the sugar industry and one that has proven to be efficient. Due to the numerous associated disadvantages that exist, such as the public nuisance of soot and smoke, soil damage and its contributions to air pollution, it is foreseen that government legislation will become more stringent, prohibiting the burning of sugarcane, thereby forcing the industry to consider other alternatives. Processing green sugarcane with brown leaf is one of the sustainable alternatives to be considered which would introduce a beneficial option for both the sugar industry and the environment. For this alternative to be recommended as a viable option, an investigation was required to determine the effects of processing green sugarcane with brown leaf in a sugar factory specifically in alignment with their current juice extraction systems (diffusers). Conducting such experiments on a commercial diffuser presented several challenges. A novel approach was undertaken to develop a pilot juice extraction technique to access and quantify the effects of processing green sugarcane with varying quantities of brown leaf in a sugarcane diffuser on a more controlled scale. Efforts were made to simulate conditions in a diffuser and thereby produce a juice that would closely represent the quality of juice extracted from a sugarcane diffuser. A pilot juice extractor technique was designed, fabricated and its performance verified before determining suitable operating conditions for further experimental work. Experimental juice extraction systems and the applicability of the system to the proposed work was evaluated. The outcome of an extensive review of the literature revealed that the pilot juice extractor design had to be based on an upward forced-flow, submerged column with a steam jacket and electrical heating option. The pilot extractor showed good ability in differentiating between juices extracted from burnt and green sugarcane with and without brown leaf. The extracted juice quality was assessed and compared on the key analytes present in the extracted juice such as gravity purity (sucrose/brix), colour, conductivity ash, reducing sugars (fructose and glucose) and non-sucrose content. An experimental design allowed for key operating conditions of time (30, 45 and 60 minutes) and temperature (75 °C, 0 °C and 85 °C) to be tested. Suitable operating conditions for the pilot juice extractor, which emanated from the experiments, included a temperature of 80 °C and a retention time of 30 minutes. In addition, the juice concentrations in the pilot extractor were found to be different (higher or lower) to the concentrations of analytes present in the juice extracted from two established methods, namely cold digestion and press methods, for most juice quality parameters. The pilot juice extractor performance was subsequently validated against a South African commercial diffuser for 16 different consignments of sugarcane of different varieties and included both green and burnt sugarcane. The diffuser draft juice was compared to the juice obtained from the pilot extractor, cold digestion and press processes. Due to a lack of green sugarcane samples tested at the factory, the correlations between draft juice and the extractor were derived for burnt sugarcane only. The pilot extractor juice quality for burnt sugarcane compared more favourably, in terms of the concentrations of the analytes, with the draft juice quality rather than the quality of the juice extracted from the cold digestion and pressing methods. The investigation of the effects of varying quantities of brown leaf on the quality of juice extracted and the effect on the sugarcane density and percolation rate was carried out using the pilot juice extractor. The tests considered included four different sugarcane varieties (N12, N16, N47 and N39) to obtain a good representation of the different types of sugarcane that is processed in sugar factories. Results showed that an increase in brown leaf content adds to colour, conductivity ash and non-sucrose content and reduces purity, sugarcane density and percolation rates across all tested varieties. The pilot juice extractor presents a suitable method that can be utilised in future studies to assess factory specific combinations of sugarcane varieties, type (burnt or green) and the effects of adding brown leaf in a diffuser, in an effort to understand any potential factory processing impacts. This will aid factories in preparation for how best to handle the situation should they be required to process green harvested sugarcane with brown leaf in the near future.
Development of a hybrid fuzzy-mathematical cleaner production evaluation tool for surface finishing
(2007) Telukdarie, Arnesh
The metal finishing industry has been rated among the most polluting industries worldwide. This industry has traditionally been responsible for the release of heavy metals such as chrome, nickel, tin, copper etc into the environment. The application of cleaner production systems to a range of industries, including the metal finishing industry has provided significant financial and environmental benefits. An example of a successful application cleaner production in the metal finishing industry is the reduction in the typical water consumption from 400 1/m² to less than 10 1/m² of plated product. The successful application of cleaner production to the mental finishing industry has encountered many barriers. These barriers include the need for a highly skilled cleaner production auditor and the need for rigorous plant data to effectively quantify the cleaner production potential of the company under consideration. This study focuses on providing an alternate user-friendly audit system for the implementation of cleaner production in the mental finishing industry. The audit system proposed eliminates the need for the need for both a technical auditor and rigid plant data. The proposed system functions solely on plant operator inputs. The operator’s knowledge is harnessed and used to conduct an efficient and effective cleaner production audit. The research is based on expert knowledge, which was gained by conducting audits on some 25 companies using traditional auditing tools. This company audits were used to construct a database of data that was used in the verification of the models developed in this study. The audit is separated into different focus components. The first system developed was based on fuzzy logic multi variable decision-making. For this system the plant was categorized into different sections and appropriate fuzzy ratings were allocated based on experience. Once the allocations were completed multi variable decision analysis was used to determine the individual variable impact. The output was compared and regressed to the database equivalent. Operator inputs can then be used to determine the individual category outputs for the cleaner for the production rating for the company under consideration. The second part of this study entails the development of mathematical models for the quantification of chemical and water consumptions. This was based on the present and ideal (cleaner production) plant configuration. Cleaner production operations are compared to present operations and potential savings quantified. Mathematical models were developed based on pilot scale experiments for the acid, degreaser and zinc plating process. The pilot experiments were carried out on a PLC controlled pilot plant. These models were developed form factorial experimentation on the variables of each of the plating processes. The models developed aid in the prediction of the relevant optimum consumptions. The key challenge in traditional evaluation systems has been the quantification of the plant production. The most effective measure of production is by means of the surface area plated. In this study a novel approach using the modeled acid consumption is proposed. It was assumed that the operator inputs for the above models would not be precise. The models developed allowed for input variations. These variations were incorporated into the model using the Monte Carlo technique. The entire cleaner production evaluation system proposed is based on an operator questionnaire, which is completed in visual basic. The mathematical model was incorporated into the visual basic model. For the purpose of model verification the mathematical models were programmed and tested using the engineering mathematical software, Mat Lab. The combined fuzzy logic and mathematical models prove to be a highly effective means of completing the cleaner production evaluation in minimal time and with minimal resources. A comparative case study was conducted at a local metal finishing company. The case study compares the input requirements and outputs from the traditional systems with the system proposed in this study. The traditional model requires 245 inputs whilst the model proposed in this study is based on 56 inputs. The data requirements for the model proposed in this study is obtained from a plant operator in less than one hour whilst previous models required high level expertise over a period of up to two weeks. The quality of outputs from the model proposed is found to be very comparable to previous models. The model is actually found to be superior to previous models with regards predicting operational variations, water usages, chemical usages and bath chemical evolution. The research has highlighted the potential to apply fuzzy-mathematical hybrid systems for cleaner production evaluation. The two limitations of the research were found to be the usage of a linear experimental design for model development and the availability of Mat Lab software for future application. These issues can be addressed as future work. It is recommended that a non-linear model be developed for the individual processes so as to obtain more detailed process models.
Development of a new static synthetic apparatus for phase equilibrium measurements
(2017) Naicker, Sivanna; Ramsuroop, Suresh
Phase equilibrium data plays a significant role in the design and optimization of industrial separation schemes, such as distillation and absorption units. These separation processes are utilised for the purification of valuable chemicals, which play a pivotal role in daily human life. Separation units are operated at various conditions of temperature and pressure, however it is common for most units to operate in the moderate pressure region (100-500 kPa). On the contrary, there is a lack of phase equilibrium data available in the moderate pressure region, thus prompting an interest in this area. In this study, a new static synthetic cell was tested, and the experimental apparatus was successfully set up and commissioned. Some key features of this design include a total working cell volume of 60 cm3 (which reduces the amount of chemicals required compared to conventional static synthetic cells) and equilibrium is achieved faster. In addition, two high-accuracy Teledyne Isco pumps were utilised for the feed loading, as it is vital that the volume of chemicals dispensed into the cell be accurately determined. The necessary calibrations were conducted and the overall uncertainties were found to be 0.06 K, 0.36 kPa and 0.1 ml for temperature, pressure and volume respectively. The following test systems were measured to determine the reproducibility of the apparatus and to verify the experimental technique: • water (1) + 2-butanol (2) at 323.16 K • n-hexane (1) + 2-butanol (2) at 329.21 K • n-pentane (1) + 1-propanol (2) at 317.18 K • n-pentane (1) + 2-butanol (2) at 303.17 K • n-pentane (1) + ethanol (2) at 303.11 K The test systems measured produced a good fit with the literature data, and thus the experimental apparatus was commissioned. New systems, previously unmeasured in the open literature, were measured in this study. These systems include: • n-hexane (1) + perfluoro-n-heptane (2) at 313.21 and 333.12 K • n-pentane (1) + 2-propanol (2) at 313.11, 323.11 and 333.12 K The data was modelled on Aspen Plus®. Since the method of operation is of the static synthetic type, no analysis of the vapour and liquid phases took place, and instead an algorithm was developed using the combined method (γ-ϕ) together with the method of Barker (1953), to convert the overall composition (zi) to liquid mole fraction (xi). The Wilson and Non-Random Two-Liquid (NRTL) activity coefficient models together with the Ideal Gas law and Hayden O’Connell second virial coefficient were utilised to regress the data. For both the fluorinated and alkane + alcohol systems, the experimental i data produced an excellent fit with the activity coefficient models. For both systems, azeotropes were observed, indicating poor separation of these binary combinations at specific mole fractions. This is due to the boiling point of both components being similar under certain conditions. The calculated pressure residuals were well within the overall combined uncertainty for pressure, whilst the calculated temperature residuals were slightly above the overall combined uncertainty for temperature.
The development of road safety assessment screening procedures for the City Tshwane Metropolitan Municipality
(2020-06) Sarjoo, Arvin Ramsunder; Allopi, Dhiren
The word “accident” is a familiar term used to describe a collision involving one or more transportation vehicles that results in property damage, injury or death. The term implies a random event that occurs due to no specific reason other than human error or unforeseen circumstances. The American National Highway Traffic Safety Administration (NHTSA) suggests replacing the word “accident” with “crash” as the word “crash” implies that the collision could have been prevented or minimised by improving driver behaviour, vehicle design, roadway geometry or the environment (Garber and Hoel 2015: 150). In the global context, South Africa, as is characteristic of many developing countries with limited resources, faces the challenge to proactively managing, reducing and eliminating the high incidence of road crashes, injuries and fatalities. Due to an absence of routine Road Safety Assessment and Audit procedures within the relevant departments at the City of Tshwane Metropolitan Municipality (CTMM), the main aim of this research was to develop procedures with measurable benefits which would promote a safer road environment. The data analysis and findings describe statistically significant relationships between Average Daily Traffic (ADT) as the independent variable and Accident Frequency as the dependant variable. The linear regression models and equations as developed allowed for the prediction of crash rates and the prioritisation of CTMM road safety projects. The findings indicated significant increases in accident rates on higher order roads (typically traffic signalled controlled intersections) with factors such as a greater number of intersection conflict points, greater pedestrian volumes and increased intersection saturation or volume/capacity levels contributing to higher accident rates. Intersection controls and traffic safety measures such as traffic circles, traffic signals, and traffic signs were assessed for effectiveness in reducing the Rate of Accidents per Million of Entering Vehicles (RMEVs). The research highlights the vulnerability of Non-Motorised Transport (NMT) (particularly pedestrians) which contributed to approximately 40% of all accident fatalities (Department of Transport 2016: 31). The recommendation therefore is for a road safety assessment and screening process to focus and allocate greater resources in the effort to proactively reduce the number of pedestrian fatalities.