Theses and dissertations (Engineering and Built Environment)

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Application of kaolin-based synthesized zeolite membrane systems in water desalination
(2021-12-01) Aliyu, Usman Mohammed; Isa, Yusuf Makarfi; Rathilal, Sudesh
Accessibility to potable water worldwide is threatene, despite 71% of the earth’s surface being covered with water. However, 97% of the 71% is too saline for consumption. A usual way of treating salinity is by membrane desalination using reverse osmosis. The disadvantage of this approach is its high cost and short life span of the polymeric membrane used. Creating a new robust high-quality water treatment system using a ceramic membrane will address these challenges due to its robust mechanical properties. In this work, we synthesized different zeolites from South African kaolin under varying conditions such as crystallization time, ageing time and temperature and their effects on the properties of zeolites synthesized was investigated. Sample characterization confirmed the successful synthesis of ZSM-5 and zeolite A. In the synthesis procedure, metakaolin served as the alternative source of silica and alumina and was use to synthesize different types of zeolites under varying synthesis conditions. Synthesized samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and Brunauer–Emmett–Teller BET surface area. The properties of the synthesized ZSM-5 were influence by the synthesis parameters, typically, crystallization temperature, ageing time and crystallization time. Crystalline ZSM-5 zeolite produced at an ageing time of 24 hours, crystallization time of 48 hours and crystallization temperature of 180°C with Si/Al ratio of 43 and BET surface area of 282 m2 /g. After a 12-hour ageing period, Zeolite A produced at crystallization time of 20 hours, the crystallization temperature of 100°C, Si/Al ratio of 1.3 and BET surface area of 143.88 m2 /g. The findings indicate that aging influences the synthesis of zeolite A, as a relatively crystalline material formed at an ageing time of 12 hours, which continued to decrease as the ageing time was increased. We do not exclude the possibility of Ostwald ripening playing a role in this relationship. Subsequently, the efficiency of zeolite A and ZSM-5 zeolite in removing salt ions, Ca2+, K+ , Mg2+ , and Na+ from synthetic seawater was investigated at room temperature using a batch adsorption system. The effect of adsorbent dosage, agitation speed and contact time were consider. Dosages varied from 2.5 to 6.0 g/100 ml while the contact time varied from 30 to 180 minutes. The results obtained showed that a zeolite dosage of 6.0g/100 ml and agitation speed of 140 revolutions per minute (rpm) yielded a maximum removal efficiency of 89.7 % for Ca2+ and minimum removal efficiency of 1.8 % for Mg2+ at agitation rates of 30 and 120 minutes, respectively. Ion exchange of Na+ by Ca2+, K+ and Mg2+ in the zeolite framework was established. The preference of the overall ion-exchange selectivity of both zeolites A and ZSM-5 are in the order of Ca2+ > K+ > Na+ > Mg2+. Zeolite A showed higher removal efficiency compared to ZSM-5 zeolite. The results point out that the synthesized zeolite was able to desalinate the salt ions in synthetic seawater to a limit below the World Health Organization (WHO) recommended values. Consequently, zeolite synthesized from kaolin offers a cost-effective technology for the desalination of seawater. The desalination and material characterization results used in selecting a potential zeolite for use in reverse osmosis (RO). The material successfully deposited on etched alpha-alumina support to produce zeolite membrane by a hydrothermal technique using a modified in-situ method. Zeolite A and ZSM-5 membranes produced and applied in the RO unit for desalination. The RO membrane experimental results show potential in desalination of synthetic seawater. A machine-learning tool was use to predict the properties of the synthesized ZSM-5 as a function of the hydrothermal parameters. Finally, a techno-economic analysis of synthesizing zeolite using locally available kaolin at a capacity of 5 x 105 kg/yr. has shown that the plant is economically viable with rapid break-even and the payback period is less than 4 years.
Application of optimal control for power systems considering renewable energy technologies
(2021-03) Chetty, Dhanpal; Sharma, Gulshan; Davidson, Innocent Ewaen
Over the last decade, power generation from renewable energy sources such as wind, hydro and solar energies have substantially increased globally and in South Africa. Of all the renewable energy sources, wind energy appears to be the most promising, considering design and costs. However, due to the intermittent nature of wind, the increased integration of wind energy into existing power systems raises several control challenges related to load frequency control (LFC) and tie-line power system stability. The stability of modern power systems, incorporating wind energy generations, will be significantly enhanced with the development of LFC strategies based on modern control theory, which is the focus of this research. This thesis presents the design, modelling and analysis, of two LFC control strategies for interconnected power systems, having wind power integrations. The first design is an optimal control strategy, based on error minimization through full state vector feedback, for a two-area interconnected power system consisting of hydro-thermal generations. The second design is a model predictive control (MPC) strategy, based output vector feedback of system state parameters, for a two-area interconnected power system consisting of thermal generations in each area. Both designs include the active power support from doubly fed induction generator based wind turbines (DFIG) in conjunction with the combined effort of a thyristor control phase shifter (TCPS) and super conducting magnetic energy storage unit (SMES). Both control strategies were simulated in MATLAB Simulink and positive results were obtained. The results show that the optimal control strategy is enhanced with power integrations using DFIG based wind turbines combined with the TCPS-SMES units and the MPC strategy is very robust and provides better dynamic performances even with parameter variations and generation rate restrictions.
Appraisal of career development among female professionals in the South African construction industry
(2022-05-13) Zungu, Hlumelo T.; Aiyetan, Olatunji Ayodeji; Mewomo, M. C.
Every human being aspires to attain to the top of his or her career. Failure results in dissatisfaction, poor productivity, and lack of interest and proper engagement in the career. The study aims to appraise career development (CD) among female professionals in the construction industry in South Africa. The study was conducted among registered female professionals in the SA construction industry. The purposive sampling technique was employed in reaching the sample. The sample frame comprised of registered female professionals within the South African Council for Project and Construction Management Profession (SACPCMP). The total number of registered professionals is 158 and the whole population was taken as the sample size. The questionnaire to the study was administered to the respondents online using Google forms survey. A total of 67 questionnaires were returned filled, representing 42.4% achieved rate.The inferential statistics was used for data analysis. The findings indicated that gender discrimination has a significantinfluence on females’ participation in CD in the construction industry. Training and continuing education in the construction industry’s influences contribution to CD for female professionals, family, and social commitments are impediments to career development for female professionals. Passion mostly motivates the interest in the career choice of females in the construction industry and the factor that most enhances the successof female professionals in career development is education. Recommendations include that policies put in place should be such that women are represented at all levels and the opportunities are granted fairly to ensure that females are not discriminated against. Provision for training programs be made and salaries for femaleprofessionals should be adjusted such that there is an allowance to cater for domestic assistance. Females should pursue or obtain higher degrees to be successful in career development in the construction industry. These qualifications are such that females couldbe placed in managerial positions. Therefore, the following post-graduate programs are recommended: Construction Management, Human Resource Management, Industrial Psychology, and many others
Assessment of emerging technologies enhancing project delivery among medium and large construction firms in Durban
(2022-07) Mchunu Johannes S’thembiso; Anugwo, Iruka C.
The objective of this research was to assess the potential of emerging ICT technologies to enhance construction project design, procurement, and delivery among medium and large construction firms registered on the Durban Construction Industry Development Board (cidb) under grade 4-6 and grade 7-9 c. The study explored how construction companies can use various emerging Information and Communication Technology (ICT) technologies such as Internet of Things (IoT), 3D Printing, Virtual Reality (VR), Building Information Modelling (BIM), Robotics and wireless sensor technology, to improve construction project delivery in the eThekwini region. This study focused on one province, KZN and the eThekwini District Municipality, located on the east coast of South Africa. The questionnaires were formulated to evaluate construction contractors’ level of awareness, understanding, knowledge, and commitment to advance business operations using new emerging technologies presently linked to the Fourth Industrial Revolution (4IR). Data collection instruments used for this study comprised an online survey as well as paper-based questionnaires. The data was analysed using percentages, mean scores, and standard deviations, and each question was ranked using the SPSS Statistical Package. The analysis shows that awareness, and knowledge of, new emerging technologies among construction companies in Durban was significantly high within offices. However, awareness, and knowledge of, new emerging technologies was significantly low on construction sites. The study revealed that a remarkable number of respondents were of the opinion that the implementation of emerging ICT technologies and the 4IR would benefit project design, procurement and construction delivery. The study concluded that there is a high level of commitment to implement new emerging technologies among construction companies in Durban. The study recommended that construction companies in Durban should acknowledge the need to enhance business processes in construction and improve levels of performance and competitiveness by implementing new emerging technologies on construction sites. The study proposed that construction companies in Durban should implement new emerging technologies to improve the performance of the sector in KwaZulu-Natal.
Basic mathematical modelling for polymer woven fabric performance suitable for low energy filtration systems
(2019) Mncube, Blessing Thokozani; Rathilal, Sudesh; Pillay, Visvanathan Lingamurti
Water is one of the most important and essential resources that people usually misuse and take for granted until it is either gone or unsuitable to be utilized for domestic, industrial or agricultural purposes. The need to explore affordable purification technologies is essential. The filtration processes are innovative technologies that can be employed in water treatment systems or water purification technologies. However, the filtration technologies have one prime limitation factor of which is fouling and biofilm formed on the membrane surface sometimes internal. Recent advancements in polymer science and textiles have led to developing fabric material that can be used as membranes suitable for emerging economies. For years’ people do use fabric to purify river water especially women from rural areas. Yet non-woven materials are used as a membrane by industries as compared to woven fabrics. However, most non-woven fabrics are easily damaged when cleaned with a polymer brush and require periodical replacement. The tapeline and filter manufacture use a woven fabric as a backer before casting or putting a filter on the weave fabric. These prove the fact that any woven fabric can be modified for optimal use. On the other hand, most Engineers and scientists have not given much attention to woven fabrics as a result, woven fabrics are not employed as membranes. Some scientists and engineers believe that woven fabrics are not suitable for treating water for domestic use. Some believe that some woven fabrics can be used as membranes provided they are capable to remove unwanted materials like bacteria and pathogen. The aim of this study is to create a full understanding of the factors that affect the fabrics when used as membranes, especially when the polymer woven fabrics are used as filters to treat water and wastewater. It is essentially important to develop standardized procedures or models that accurately describe the textile woven fabrics behaviour when used as filters. The standardized models or procedures will assist engineers and scientists when developing filtration systems using woven fabrics. The first objective was to evaluate and compare the fabric types that can be used as filters or membranes in water and wastewater treatment processes. The second objective was to identify the applications for woven fabric membranes and evaluate the factors that play a critical role during the filtration process and relationship between those factors. The experimental investigations conducted were to evaluate the (1) main objectives; (2) effect of membrane orientation; (3) effect of feed quality on membrane performance; (4) effect on stable flux quality and quantity of the selected fabrics; (5) effect of fabric type on filtration or microfiltration processes; (6) effect of membrane fouling on membrane performance; (7) develop the basic model suitable in identifying the right fabric for any filtration system operating at low energy. The experimental investigations conducted were to evaluate the selected woven fabrics that were manufactured in South Africa, easy to clean with a polymer brush. Those woven fabrics were tested using South African river water and wastewater from treatment plants. When evaluating different feed solutions, bio-fouling was considered to be the major limiting factor of woven fabrics, but the feed with a lot of bio impurities can be modified for optimization processes. Laboratory apparatus and field apparatus was developed to analyze and evaluate the effect and behaviour of fabrics performance, and cake formed on the fabrics. The result clearly states that a solution or wastewater with a lot of biological organisms produce lower flux and also produces a lower critical/stable flux when compared with the solution with more incompressible solids or impurities. The result clearly shows that all selected fabrics can be used as filters however; the polyester fabric was the only fabric that can be used for microfiltration processes suitable to clean water for domestic use. This polyester fabric removes 99.995% of impurities from the polluted waters. The Permeate water quality coming from this polyester fabric was less than 1NTU, before and after stable flux. Other fabrics can be used as filters but not for microfiltration. These three fabrics are not capable of removing micro-impurities (less than 20 micrometres). The basic mathematical modelling Equation developed, proved that the membrane pore size, driving force, impurities size in polluted water, impurities nature and impurities concentration play major roles in the filtration process especially in stable flux formation. The simple Equation F = Ae−Bt + C was discovered to be suitable to evaluate the fabric performance, where C is the constant flux value, A is the maximum flux value and B is the part of the critical area or rate change. The Equation can be applied to most fabrics that are used as filters. Testing the maximum flux value was critical and achievable when using pure and clean water especially the distilled water. The results show that most solutions with high compressible impurities will take less time to reach a critical or stable flux. The solution or effluent or river water with more bio impurities and more bacteria will have less flux when compared with a solution with more incompressible impurities. Most polymer woven fabrics do not require any sophisticated technologies or additional chemicals to clean. It can be easily brushed with a polymer brush. Brushing the surface of the fabric with balanced tensile strengths in both warp and weft yarns will not rearrange, damage, or affect the pore size. Only sharp objects can damage the polymer fabrics. The knowledge of this report will assist in optimising the filtration system operation at low energy when using woven polymer fabrics as membranes for filtration. The basic mathematical model can be useful to engineers and scientists willing to use woven fabrics as membranes. Hence, mathematical modelling is one of the important tools of engineering optimization and design. This study focuses on the low energy (gravity-driven) systems that treat water and wastewater like Household Point of Use (POU) systems. Other POU systems were tested and compared to POU systems that are made of the Polymer woven fabric. Based on results, it can be concluded that POU's that uses polyester membranes (PWF-POU) are good prospects for area without sophisticated water or wastewater treatment systems since it removes almost all bacteria and impurities. Polyester woven fabrics can be used as a microfiltration membrane not only to process water or wastewater but also to process chemicals, oils, etc. The other selected fabrics that were made of polypropylene filaments need to be modification in order to operate at optimum when cleaning water for domestic and tertiary use. When modifying these polypropylene fabrics, the quality do improved.
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.
A case study : evaluation of adjudication as a dispute resolution method : NEC and FIDIC contracts
(2022-09-29) Mkhize, Zizodwa Zizo; Allopi, Dhiren
Construction development plays an important role in the development of South Africa, not only in respect of its built infrastructure, but also in its broader economic and social development. It also creates employment prospects on a broader scale. Construction contract adjudication has been introduced in South Africa by means of four forms of contracts endorsed by the Construction Industry Development Board. Amusan and Owolabi (2014) mention that the unfavourable outcomes of project objectives in terms of time, cost and quality are as a result of delays in construction projects. Although disputes may be unwanted, having suitable knowledge to manage disputes when they happen often provides better results for the disputants and the project. The study was conducted in an electricity generation organisation, which has various divisions and departments that develop and execute projects. Complex projects that require multiple interdivisional or external stakeholder interfaces are planned, developed and implemented in the Group Capital Division (GCD). The purpose of this research study was to evaluate whether the causes, practices and outcomes of the construction contract adjudication method for the Fédération Internationale des IngénieursConseils (FIDIC) were similar to those of New Engineering Contract (NEC) used for infrastructure construction projects. A mixed method by means of a case study was adopted to answer the research questions. Data were collected from an analysis of 33 study documents related to FIDIC and NEC contract case studies. The results of the study showed the following: 1) There are comparable causes of disputes among the two contracts, even though they vary in terms of ranking on each contract; 2) some of the disputes referred to adjudication could have been avoided; and 3) FIDIC and NEC complied with the adjudication practice, and the outcomes of the adjudications differed based on the merits of each case.
Catalytic conversion of alcohol-waste vegetable oil mixtures over aluminosilicate catalysts
(2018) Ganda, Elvis Tinashe; Isa, Yusuf Makarﬁ
Thermochemical catalytic conversion of ethanol-waste cooking oil (eth-WCO) mixtures was studied over synthesised aluminosilicate catalysts HZSM-5, FeHZSM-5 and NiHZSM-5. The thermochemical reactions were carried out at temperatures of 400° and 450°C at a fixed weight hourly space velocity of 2.5 h-1 in a fixed bed reactor system. Successful conversion of the eth-WCO mixtures was carried out over the synthesised catalyst systems and in order to fully understand the influence of the catalysts, several techniques were used to characterise the synthesised materials which include XRD, SEM, EDS, BET techniques. Results of the catalyst characterisation showed that highly crystalline solid material had been formed as evidenced by the high relative crystallinity in comparison with the commercial HZSM-5 catalyst at 2θ peak values of 7°- 9° and 23°- 24°. The introduction of metals decreased the intensity of the peaks leading to lower values of relative crystallinity of 88% and 90% for FeHZSM-5 and NiHZSM-5, respectively. However this was even slightly higher than the commercial sample which had a value of 86% with respect to HZSM-5 synthesised catalyst taken as reference material. There was no significant change in XRD patterns due to the introduction of metal. Elemental analysis done with energy dispersive spectroscopy showed the presence of the metal promoters (Fe, Ni) and the Si/Al ratio obtained from this technique was 38 compared to the target ratio of 50 set out initially in the synthesis. From the SEM micrographs the morphology of the crystals could be described as regular agglomerated sheet like material. Surface area analysis showed that highly microporous crystals had been synthesised with lower external surface area values ranging from 57.23 m2/g - 100.82 m2/g compared to the microporous surface area values ranging from 195.96 m2/g to 212.51 m2/g. For all catalyst employed in this study high conversions were observed with values of over 93 %, almost total conversion was achieved for some samples with values as high as 99.6 % with FeHZSM-5 catalysts. Despite the high level of conversion the extent of deoxygenation varied with lower values recorded for FeHZSM-5 (25%WCO) at 400°C and NiHZSM-5 (75%WCO) at 450°C with oxygenated hydrocarbons of 19.5% and 19.33% respectively. The organic liquid product yield comprised mostly of aromatic hydrocarbon (toluene, p-xylene and naphthalene) decreased with the introduction of metal promoters with NiHZSM-5 producing higher yields than FeHZSM-5. For the pure waste cooking oil (WCO) feedstock the parent catalyst HZSM-5 had a liquid yield of 50% followed by NiHZSM-5 with 44% and lastly FeHZSM-5 had 40% at 400°C which may be seen to follow the pattern of loss of relative crystallinity. An increase in operating temperature to 450°C lowered the quantity of organic liquid product obtained in the same manner with the HZSM-5 parent catalyst still having the highest yield of 38% followed by Ni-HZSM-5 with 36% and Fe-HZSM-5 having a value of 30% for pure waste cooking oil feedstock which may be attributed to thermally induced secondary cracking reactions. For all catalyst systems with an increase in the content of waste cooking oil from 25% to 100% in the feed mixture there was a linearly increasing trend of the liquid product yield. HZSM-5 catalyst increased from 14% to 50% while FeHZSM-5 increased from 16% to 40% and NiHZSM-5 increased from 12% to 44% at a temperature setting of 400°C with lower values observed at 450°C.Results obtained in this study show the potential of producing aromatics for fuel and chemical use with highly microporous zeolite from waste material such as waste cooking oil forming part of the feedstock.
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.
Collaborative approaches in achieving sustainable private-public transportation services in inner-city areas : a case of the Durban minibus taxis
(2022-05-13) Mabandla, Lonna S.; Musvoto, Godfrey Gombana; Moodley, Sogendren M.
Transportation is a catalytic feature within cities and is interdependent on land use activity by means of a feedback loop that is created between the two. The most catalytic example of this is public transportation routes internal to inner-cities: they draw focus to these areas by enhancing accessibility, therefore creating spaces that are conducive for business activity, while business activity also informs public transportation routes. It is for this reason that this dissertation focuses on public transportation within inner-city areas. Durban is the chosen case study where the dominating form of public transportation within the central business district (CBD) is minibus taxis. The paradox here is that minibus taxis still form part of the informal economy even though they are the leading form of public transportation in South Africa. There have been many attempts to formalise this industry in order for it to follow more regulatory practices, but minibus taxis are privately owned and operate within the capitalist economy. The interventions put in place were aimed to better integrate minibus taxis into the urban fabric of cities for the purpose of creating a more harmonious urban environment, but to date all attempts have failed to produce the intended outcome. This research explores ways in which public and private institutions can collaborate for the intention of creating a better public service. This is critical given that an informal economic entity is dominating the public spaces of South Africa. This research is inspired by the notion of the just city which has major sway in contemporary urban thinking. A just city embraces principles such as good access and heterogeneity in public spaces, amongst others, which are hugely influenced by transportation. The argument of this study is that the application of collaborative planning through a sustainable partnership between the public and private sector will improve the social and environmental sustainability of public transportation. This process is complicated however and one of the major challenges that exist within such collaborative endeavours are power dynamics. As a result, a key focus in the study is around power relations. Practically, power relations should be observed over a period of time, specifically when the different stakeholders engage with each other, so as to reflect valid data. However, a length data collection process was not possible to observe during the data collection phase of this research. Instead interviews were conducted focusing on existing procedural planning practices between the inner-city minibus taxi association (South and North Beach Taxi Association), the eThekwini Transport Authority(ETA), and the eThekwini Town Planning Department. Conclusions and recommendations were then generated based on these data
Comparative analysis of high voltage alternating current & high voltage direct current offshore collection grid systems
(2021-12-01) Pillay, Caleb Jordache; Musasa, Kabeya; Davidson, Innocent Ewaen
An increase in industries as well as the world’s population, is causing a strain on the electricity supply. This coupled with the fact that fossil fuel supplies are decreasing, is leading the world to new, greener methods of electrical energy generation. Offshore wind farms are being developed far offshore and solar farms are being developed in remote locations with intense sunlight. This allows for the optimal operation of these systems. HVAC collection systems for offshore wind farms have traditionally been used but imposes limitations on the transmission distance. Exuberant amounts of capital are required for greater distances. HVDC systems have started to be recognised as a viable method of transmitting this electrical energy at a much lower cost on longer distances. This study shows a comparative performance and cost evaluation of both HVAC and HVDC collection systems for offshore wind farms. It evaluates the efficiency of the wind farm based on system losses, determines the advantages, disadvantages, and cost implications of each system, and determines the best type of technology to be used in offshore applications. The study looks at a case of a 40 MW wind farm at a distance of 120 km offshore. A simulation is developed for each system using MATLAB simulation software to determine the performance of each system during normal operation and fault conditions. From these simulations, it was found that HVDC collection systems have much higher efficiency when compared to HVAC systems and perform better under both normal operation and fault conditions. HVDC systems also have a lower cost once the break-even distance point is passed. From the study, it is found that HVDC collection systems are much better suited to allow offshore wind farms to have a high efficiency as well as be located further offshore to allow for maximum wind usage. The technology can be used for other long-distance transmission systems and incorporated for other renewable energy generation systems.
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.
A comparative study of the construction of road formation layers using labour-intensive versus traditional mechanistic methods on road 1264 in KZN
(2022-05-13) Mkhize, Mongezi S.; Walker, Mark; Mckune, Tom
The urgent need to upgrade and construct roads in South Africa is one of the many critical utility provision challenges faced by the municipalities, consultants and departments involved in road construction. The biggest challenge that is faced by the government is to minimise unemployment and increase skills transfer through the training of inexperienced local communities on road construction. The road can be constructed using traditional mechanistic methods (TMM), commonly known as plant machines, which makes more use of plant machine than labour. On the other hand, the road can also be constructed using the labour-intensive construction (LIC) method which utilises more labour involvement during construction and minimal machine usage. The purpose of this research is to provide insight into the time and cost comparison between LIC and TMM of constructing road formation layers. Road D1264 in Bergville, KwaZulu-Natal will be used as a case study in the research to compare the difference between labour-intensive and traditional mechanistic construction of road formation layers, using cost and time to reach the same quality. This research aims to promote the use of LIC roadbed construction to be used more frequently in the road construction industry in South Africa. The Expanded Public Works Programme (EPWP) encourages road construction to be undertaken using labour- intensive methods to allow unemployed people to be given more job opportunities. Municipalities, consultants and departments involved with road construction will be assisted through this research in making informed decisions and selections thereafter of the most reliable road formation construction method in terms of time and cost. Available cost, time and quality data from the Road D1264 will be used to compare the construction of road formation layers using LIC versus TMM in KZN. The decision making process will lie in the hands of the municipalities and consultants based on the cost and time required to complete the project. Furthermore, a quantitative survey questionnaire was developed by the researcher. This questionnaire was aimed at the road construction technical experts in the Department of Transport, Department of Works, consultants and the roads departments of districts and local municipalities. The results of the survey questionnaires revealed that the road construction experts agree with the finding of this study that LIC is more expensive when compared to TMM. LIC is also more time-consuming than TMM. LIC and TMM produce the same quality. The survey questionnaire revealed that South Africa may be advancing over the years in the use of LIC methods; however, more education in the form of training, seminars and other methds of marketing must be undertaken, starting at the universities, municipal level, the Department of Transport, Department of Works, and consultants. The comparative research in this study using the available data from Road D1264 revealed that during the construction of the road formation layers, using LIC is more expensive when compared to TMM. LIC is also more time-consuming than TMM. LIC and TMM produce the same quality. But it cannot be ignored that LIC creates employment particularly for women, youth and the disabled within the community. LIC maximises the use of local materials and plant owners as suppliers of goods and services. LIC can be the country’s solution to unemployment and porvety.
Desalination of a local oil refinery effluent to meet discharge limits
(2021-12-01) Ezugbe, Elorm Obotey; Rathilal, Sudesh
The Sustainable Development Goal Six (SDG 6) – “ensure availability and sustainable management of water and sanitation for all” places huge responsibilities on stakeholders (industry, domestic and agricultural) to prioritize water saving, water reuse and proper wastewater treatment to make potable water accessible everywhere in the world. With the industrial sector consuming nearly 20% of the fresh water available, there is a corresponding generation of large volumes of effluents. This has been projected to increase, as population is skyrocketing and more economies are becoming more industrialized to accommodate the needs of the ever-increasing population. Over the years, stringent effluent discharge limits have been imposed on the industrial sector to minimize the pollution of the receiving environments, especially the water bodies. In addition, wastewater treatment for reuse is being encouraged, which will ease the stress on freshwater resources. The oil refinery industry is noted for the generation of large volumes of effluents. These effluents are heavy laden with toxic and refractory materials as well as high concentrations of salts which pose huge environmental risks and detrimental ripple effects on humans and animals if these effluents are not properly treated before discharge. Unfortunately, the use of conventional treatment methods to treat downstream oil refinery effluent (ORE) has been unsuccessful in the removal of these materials, especially the salts. This research therefore, aimed at desalinating the effluent from the effluent treatment plant (ETP) of a local South African waste oil refinery to meet discharge limits. The ETP, even though successful in the removal of organics (COD, turbidity and colour), consistently records high levels of sulphates, chlorides and carbonates as a result of the source of their raw material and other in-house processes that take place during the treatment process. The study assessed and compared the feasibility of applying three membrane processes, viz forward osmosis (FO), reverse osmosis (RO) and hybrid FO-RO systems in desalinating the ORE. The FO and RO were first run as standalone processes, where models were generated and used to optimize the important factors using the Box-Benhken design (BBD) of response surface methodology (RSM). Based on the optimized conditions, the hybrid FORO was investigated. The basis of comparison was their permeation fluxes, salt rejection and flux recoverability after membrane cleaning. A total of 45 experimental runs were conducted which catered for pure water flux tests of virgin membranes, optimization studies and confirmatory runs. The factors of interest for FO were feed solution flow rate (FS-FR) (7.5 – 9.4 L/h), draw solution flow rate (DS-FR) (7.5 – 9.4 L/h) and draw solution concentration (DS-C) (20, 35 and 50 g/L NaCl). With RO, focus was placed on operating pressure (14 – 18 bar), feed concentration and operating time (4-6 h). The results showed an average permeation flux of 3.64 ± 0.13 L/m2 h, Clenrichment (reverse solute diffusion (RSD)) of 35.5 ± 5.15%, SO4 2- rejection of 100%, CO3 2- rejection of 94.59 ± 0.32 and flux recovery of 86.01 ± 2.66% for FO. For RO, the average permeation flux achieved was 2.29 ± 0.24 L/m2 h, Clrejection efficiency was 90.54 ± 0.81%, SO4 2- rejection efficiency was 95.1%, CO3 2- rejection efficiency was 97.3 ± 0.4 and flux recovery after membrane cleaning was 62.52 ± 2.62%. The FO-RO hybrid process proved unsuccessful due to constraints from the filtration unit. As an intervention to make the hybrid process work, NF was used as the recovery process. However, results show a low permeation flux of 0.69 ± 0.10 L/m2h on average. From the results obtained, it was concluded that RO presents the best desalination option for treating the ORE using low pressure of between 14 – 18 bar. This will require no post treatment and there will be no contamination of feed due to RSD
Development and evaluation of flux enhancement and cleaning strategies of woven fibre microfiltration membranes for raw water treatment in drinking water production
(2015-08) Pikwa, Kumnandi; Rathilal, Sudesh; Pillay, Visvanathan Lingamurti
Woven Fibre Microfiltration (WFMF) membranes have several advantages over its competitors with respect to durability, making it a favourable alternative for the developing world and operation during rough conditions. Wide application of membrane technology has been limited by membrane fouling. The durability of the WFMF membrane allows more options for flux enhancement and cleaning methods that can be used with the membranes even if they are vigorous. Therefore, the purpose of this work was to develop and evaluate flux enhancement and cleaning strategies for WFMF membranes. Feed samples with high contents of organics and turbidity were required for the study. Based on this, two rivers which are Umkomaasi and Duzi River were identified to satisfy these criteria. A synthetic feed with similar fouling characteristics as the two river water was prepared and used for this study. The synthetic feed solution was made up of 2 g/ℓ of river clay in tap water and 0.5% domestic sewerage was added into the solution accounting for 2% of the total volume. A membrane filtration unit was used for this study. The unit consisted of a pack of five membrane modules which were fully immersed into a 100 litres filtration tank. The system was operated under gravity and the level in the filtration tank was kept constant by a level float. The study focused on evaluating the performance of the woven fibre membrane filtration unit with respect to its fouling propensity to different feed samples. It also evaluated and developed flux enhancement and cleaning strategies and flux restoration after fouling. The results were compared to a base case for flux enhancement and pure water fluxes for cleaning. The WFMF membrane was found to be prone to both internal and external fouling when used in the treatment of raw water (synthetic feed). Internal fouling was found to occur quickly in the first few minutes of filtration and it was the major contributor for the loss of flux from the WFMF membrane. The fouling mechanism responsible for internal fouling was found to be largely pore blocking and pore narrowing due to particle adsorption on/in the membrane pores. The structure (pore size, material and surface layout) of the WFMF membrane was found to be the main cause that made it prone to internal fouling. The IV major fouling of the WFMF membrane was due to internal fouling, a high aeration rate of 30 ℓ/min had minimal effect on the fouling reduction. An aeration rate of 30 ℓ/min improved the average flux by only 36%, where a combination of intermittent backwashing with brushing and intermittent backwashing with aeration (aeration during backwashing only) improved average flux by 187% and 135% respectively. Pre-coating the WFMF membrane with lime reduced the effects of pore plugging and particle adsorption on the membrane and improved the average flux by 66%. The cleaning strategies that were most successful in pure water flux (PWF) recovery were high pressure cleaning and a combination of soaking and brushing the membrane in a 0.1% NaOCl (desired) solution. PWF recovery by these two methods was 97% and 95% respectively. Based on these findings, it was concluded that the WFMF membrane is susceptible to pore plugging by colloidal material and adsorption/attachment by microbiological contaminants which took effect in the first hour of filtration. This led to a 50% loss in flux. Also, a single flux enhancement strategy proved insufficient to maintain a high flux successfully. Therefore, combined flux enhancement strategies yielded the best results.
Development of a small scale water treatment system for fluoride removal for rural areas
(2015) Dlamini, Thulani; Rathilal, Sudesh; Pillay, Visvanathan Lingamurti
Several areas in the world such as the United States of America, Sri Lanka, China, Argentina, Canada, Tanzania, Kenya, South Africa and many others have a problem of high fluoride content in drinking water. Generally fluoride levels above 1.5 ppm in water may result in dental and skeletal fluorosis in humans depending on quantity consumed (Fan et al., 2003; Meenakshi, 2004). Remote rural areas where there are no water treatment facilities are more vulnerable to this problem. Adsorbents such as activated alumina and FR-10 resin seem to have a potential for successful application in rural areas. These methods however require pre-treatment if the feed has high turbidity. A membrane based system called woven fabric microfiltration gravity filter (WFMFGF) developed by Durban University of Technology proved to be suitable for turbidity removal. The main objective of this research was to develop a small water treatment system for fluoride removal. The small water treatment system developed in this study consists of WFMFGF for pre-treatment and an adsorption column. The WFMFGF is made up of a 40 L container packed with 15 immersed flat sheet membrane elements. The operation of the WFMFGF is in batch mode, driven by varying static head. The static head variation results in flow rate variation through the system. This in turn result in variation of contact time, velocity as well as pressure drop in the fluoride removal unit. Specific objectives of the study were: (1) to establish the maximum and minimum flow rates through the WFMFGF system, the total run time before cleaning is required and the best cleaning method for this particular membrane system. (2) to evaluate and compare the performance of activated alumina and FR-10 resin on varying contact time, velocity and pressure drop on the fluoride removal unit. The adsorbents were also compared on adsorption capacity, cost and ease of operation. The minimum and maximum flow rates through the WFMFGF were found to be 5 l/hr and 100 l/hr respectively. It was found that the system can be run for more than a month before requiring cleaning. The suitable cleaning method was found to be soaking the membranes in 0.0225 percent sodium hypochlorite solution overnight and brushing them using a plastic brush. The comparison of the performance of FR-10 resin to activated alumina found that the adsorbents gave equal performance based on the given criteria. FR-10 resin had higher adsorption capacity, gave good quality treated water even with shorter contact time and operated at wider velocity range. Activated alumina on the other hand had an advantage of lower costs, lower pressure drop and ease of use. According to Pontius (1990), the performance of activated alumina can be improved by intermittent operation. Point of use (POU) systems are generally operated intermittently. This improves the fluoride removal efficiency of activated alumina giving it more advantage over FR-10 resin. Based on this activated alumina was selected as the best adsorbent for the system. After the adsorbent was selected, the adsorption column was designed. The column operation regime was 3.5 minutes minimum contact time and 1.17 to 7.8 m/hr velocity range. The activated alumina adsorption capacity was 1.53mg/g. The column had an inside diameter of 70 mm. It was packed with activated alumina to a bed height of 400 mm. The column inlet and outlet pipes were made of PVC with a standard pipe size of 20 mm outside diameter. A valve at the column inlet pipe allowed water to flow through the system.
Evaluation of small-scale batch biodiesel production options for developing economies
(2014-06-13) Chukwuka, Gabriel; Rathilal, Sudesh; Ramsuroop, Suresh; Pillay, Visvanathan Lingamurti
Biodiesel is a renewable fuel that can be produced from animal fats, vegetable oils or recycled used cooking oil. From the 1970’s, biodiesel received increased focus as an alternative to crude oil and its component products. Among various processes used for biodiesel production, transesterification of glyceride and alcohol in the presence of a catalyst to produce ester (biodiesel) and glycerin remains the most common. In Africa, biodiesel is currently produced industrially in a number of ways via different methods. In South Africa, there are a number of biodiesel production plants that are continuous processes with feed samples from different sources. Reviewing the batch systems for developing economies, various observations were made. Some produced biodiesel using batch systems at room or day temperatures, another used different temperatures, some also used flat based buckets for their mixing and so on. This becomes difficult for local producers who desired to produce biodiesel on a very small scale for their farms or business. Hence, the study was aimed at evaluation batch biodiesel systems and to come up with a simplified approach for a producer in a developing economy or a local user. The objectives of this study were as follows; To evaluate biodiesel production options, and hence develop a simplified process that can be used to produce biodiesel in developing economies. The criteria for evaluation will include: ease of operation, non-specialist equipment, range of feedstock, product quality and product yield. To evaluate various factors that affect these criteria and make recommendations that will enable a local producer to remain within an optimum range Compare the produced biodiesel properties against general biodiesel and petroleum diesel ASTM standard range Recommend simplified equipment design for a local producer Perform economic evaluation to establish cost required both for equipment and raw materials for a local producer. After literature review on the existing processes, base catalyzed transesterification was selected. This is because of the simplicity as well as ease of operation. Experimental trials commenced using feeds from pure vegetable oil (PVO) and waste vegetable oil (WVO) to familiarize biodiesel production, as well as study the behavior of each having the research criteria in focus. Various variables that affect ease of operation, product quality, and yield were also investigated. These include temperature, type of catalyst (KOH or NaOH), type of alcohol (Methanol or Ethanol), concentration of catalyst, and purity of alcohol, and nature of feed (PVO or WVO). The effect of temperature was compared against product quality, yield, and ease of operation. Other variables were also compared against the same criteria. Treatment of WVO because of impurity and moisture contamination associated with such samples was also studied. The product was then tested using some ASTM procedures to compare biodiesel quality to acceptable standards. Efficient reaction time is paramount for a quality biodiesel. It was observed that biodiesel required between 25 and 30 minutes for a complete reaction. Lower temperatures clearly affected the quality of biodiesel produced. Best operating range was found to be between 55 oC – 75 oC is usually recommended for a transesterification reaction to obtain optimum yield and quality. The use of KOH compared to NaOH yields similar results even though NaOH is usually selected because of the reduced cost. The use of methanol compared to ethanol also yields similar results, even though methanol is usually preferred due to cost. Purity of available alcohol is vital as its reduction from 99.5 % to 75 % during experimental trials, yielded poor quality biodiesel. This is mainly due to moisture content that usually gives room for bacteria growth and corrosion of fuel lines in engines. As long as a titration test is carried out on the feed, the use of WVO is a good option. Varying catalyst concentrations from 0.5 % to 1.75 % were considered and the best regimes identified. This test will enable a producer from a growing economy to use the appropriate reagent, which will ensure the transesterification reaction is complete. After comparing appleseed and cone based design, the latter was selected as it will eliminate any difficulty that a local producer might encounter in making the biodiesel batch. In terms of costs, it was discovered that the major costs to a local producer will be the biodiesel mixer and fittings which will be fixed costs. Other variable costs are considered to be affordable, as the cost of waste vegetable oil is very low as well as other industrial reagent grade that will be required. In summary, batch biodiesel production for a local user or developing economy is a very feasible exercise. One needs to ensure that the recommendations regarding pre-treatment of feed oil, basic reaction criteria and other generic parameters are considered during production.
Evaluation of veterinary antibiotics in a swine slaughterhouse wastewaters and their removal using advanced oxidation processes
(2020-01) Chollom, Martha Noro; Rathilal, Sudesh; Swalaha, Feroz Mahomed; Bakare, Babatunde F.
Antibiotics are found in low concentrations in water sources and surrounding environments. Despite their presence in low concentrations in the environment, they are associated with antibiotic resistant bacteria (ARBs) in water sources thus necessitating stringent legislations worldwide. The burden of ARBs has drawn worldwide attention into investigating this rising phenomena to better understand the seriousness of the effects of these contaminants. Studies conducted, however, have mostly been in the developed nations, and the focus has been on human pharmaceuticals. Information on veterinary pharmaceuticals is very limited, even though, the veterinary pharmaceuticals are known to cause as much havoc as human pharmaceuticals. Given the considerable impact that the veterinary antibiotics can have on humans and the environment, there is need for thorough investigations to be done regarding their detection and removal from water sources using biological and other appropriate technologies such as advanced oxidation methods. However, there is very little that has been done to date in this area globally and in South Africa in particular which highlights the novelty of this work. The findings of this study will therefore inform future decision making by policy makers and governments in handling these veterinary antibiotics in water sources. This study was divided into four phases covering the five objectives investigated. The first phase covered the first and second objectives, in which a suitable and sensitive analytical method was developed for the determination of veterinary antibiotics based upon solid phase extraction (SPE), ultrahigh liquid chromatography with photodiode array detectors (PDA) and mass spectrometry (MS) (UHPLC-PDA-MS). Four classes of antibiotics were selected: tetracycline, β-lactam, sulphonamides and fluoroquinolones. The studied antibiotics were extracted from slaughterhouse wastewater samples using strata-X cartridges. The extraction of antibiotics from water matrices was tested at several pH values. The best recoveries were obtained at pH 2. Depending on the nature of antibiotic, the limits of detection (LOD) and limits of quantification (LOQ) were in the range of 0.1–0.3 μg/L and 1.3–2.9 μg/L, respectively. The range of antibiotics detected in the wastewaters in effluents was 0.008 to 4.9 ng/L while in the influent, the range was 1 to 21 ng/L; thus higher concentrations were found in the influents as compared to effluents. This therefore confirmed the presence of these contaminants in the South African slaughterhouse wastewaters. The second phase entailed the investigation of the third objective which was to determine the possible mechanisms of removal of antibiotics from wastewaters using anaerobic digestion and to evaluate the biodegradation kinetics. A laboratory scale upflow anaerobic sludge blanket (UASB) reactor was employed to treat synthetic wastewater to explore the removal efficiencies of five veterinary antibiotics with an initial concentration of 50 µg/L. In a like manner, batch reactors were further used to evaluate the removal routes of the antibiotics. The UASB reactor was operated continuously under mesophilic conditions to evaluate its performance regarding the removal of organics; biogas production was also monitored. Organic loading rate (OLR) was varied from 8 to 9.2 kg.COD.m-3.d-1while keeping the hydraulic retention time (HRT) constant at 12 h. A chemical oxygen demand (COD) removal efficiency higher than 75% was achieved at an OLR of 9 kg.COD.m-3.d-1, with a HRT of 12 hours. About 80% of the antibiotics were removed during the continuous processes, however, a distinctive pattern of removal was not observed. The kinetic studies using a batch process showed that the removal route for the antibiotics was majorly adsorption to the sludge. Biodegradation occurred alongside adsorption but to a lesser degree. The kinetic data showed that the antibiotics degradation followed a first order kinetic model with half-lives that ranged from 6 to 77 days. Given the ineffectiveness of the biological process against the antibiotics, there was need to explore alternative wastewater treatment technologies. In this case adsorption and photocatalysis were investigated. Phase three presents the preparation and characterization of the integrated photocatalyst (IPCA). The adsorption properties of the IPCA, titanium dioxide (TiO2) and activated carbon (AC) were assessed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). These adsorbents were used to treat wastewater containing the target antibiotics. The effect of process variables such as adsorbent concentration, contaminant concentration and solution pH was investigated. The IPCA demonstrated good adsorption ability attaining removal efficiencies of over 50% while AC efficiency was over 60%. However, TiO2 demonstrated negligible adsorption performance. In the fourth phase, objective five was evaluated to determine the effectiveness of advanced oxidation processes (in this case photocatalysis) using IPCA and TiO2. The effect of process variables such as photocatalyst concentration and solution pH were investigated. It was found that photocatalysis attained almost 100% degradation of the target contaminants. Maximum removal efficiencies for both AC and IPCA were above 50% for an initial concentration of 100 mg/L. Adsorption using AC and IPCA followed the Langmuir and Freundlich isotherms, however, higher coefficients of correlation were obtained for the Langmuir isotherms for four of the antibiotics viz. AMO, CIP, ENRO and TET. The Freundlich model was the best fit for the SULFA in terms of the coefficient of correlation. With regards to the photodegradation, it was found that photocatalysis attained almost 100% degradation of the target contaminants. Complete degradation was achieved within half-lives of 60 to 102 minutes for all the compounds. Although both photocatalysts effectively degraded the contaminants, the IPCA had the unique advantages of possessing both adsorptive and photocatalytic properties. The activated carbon in the IPCA provided sites for the attachment of the antibiotics and TiO2 thus enhancing the photocatalytic performance. Apart from this, the IPCA can be easily recovered for reuse by decantation unlike the slurry TiO2. Therefore, the study demonstrated the effectiveness of the IPCA as a suitable photocatalytic material for the complete degradation of these antibiotics.
Geographic information system as a vessel for conventional and alternative forms of zoning
(2020-10-06) Kitching, Joseph; Musvoto, Godfrey Gombana
Given the well-documented rates of global urbanisation and the fact that sub-Saharan Africa is set to urbanise at the highest rate during the next few decades, it is easy to understand that urban management systems will increasingly be under pressure to operate efficiently, effectively and transparently in order to circumvent potential economic, social and environmental disasters. A land-use management system is one of the management systems in urban areas aimed at ensuring health and safety, environmental quality, sustainability, social equity, and amenity, amongst others. Since the beginning of the twentieth-century, a key tool of planners wishing to accomplish this, has been zoning. Although zoning has been abused, and heavily criticised for that, the objectives of zoning systems around the world echo noble values such as promoting environments that are safe from flooding and fire hazards, that encourage harmonious communities and economic growth, that preserve agricultural land, and protect the natural environment. Conventional zoning, which was significantly shaped by the US Supreme court’s village of Euclid decision, focuses on the separation of incongruent land uses. There are also several other types of zoning such a flexible Euclidean zoning, performance- based zoning and even no zoning. Amongst the novel types are form-based codes, which stem from the New Urbanism paradigm. Form-based codes focus more on the public realm and the appearance of spaces and structures rather than the use of space. Practically and problematically, both conventional and alternative zoning schemes are currently comprised of a map and a separate text document. The map depicts the geographic dispersion of zones, typically related to properties or zoning districts. The text document contains regulations pertaining to the various zones, procedures and definitions. Alongside the inefficient separation of regulation and map, are the variations within single zones where specific, locally important, regulations apply to some properties within the zone. Geographic information systems (GIS) have been evolving since the mid-twentieth century and have gained serious traction with the advent of the microcomputer. Defined by many as a system that captures, collects, manages, analyses and presents geographic data and attributes, it is essentially a database linked to a geographic component, In the case of zoning, it currently comprises geographic properties linked to attributes describing the zoning. The rigid, surveyed, property boundaries make the vector or discrete objects model ideal for the representation of zoning. The raster model – the other half of the debate – is useful in representing images supporting the regulations. Given the need for more efficient systems, the pervasiveness of corruption and poor capacity in municipal systems, the omni-present abuse of power, the need for an informed citizenry and laws that are comprehensible, this study aims to see if GIS can be used to represent the regulations in conventional and alternative schemes. To establish this, six sample cities from around the world, more than twenty conventional zones in the eThekwini municipality and two zones from the Daufuskie form-based code were assessed to determine what types of regulations are common and whether they could be represented as either geographic norms or attributes to geographic features. This study found that GIS is able to represent all regulations in conventional schemes and most of the regulations in alternative zoning. It also found that some regulations are naturally inclined to spatial representation, others as attributes, and still others as scanned attachments or hyperlinks. This implies that there is no need for the separation of regulations from property and the confusion and potential misinterpretation that are associated with current practices.
Hydrological modelling under limited data availability : a case study of Umdloti River, South Africa
(2016) Mashiyane, Thulasizwe Innocent; Adeyemo, Josiah
Due to the water scarcity in South Africa, new strategies in management planning are needed in order to sustain water resources. The increase of population and economic growth in South Africa has a negative effect on the water resources. Therefore, it should be well managed. The main concerns of the sustainability of water resources are hydropower, irrigation for agriculture, domestic and industries. Hence, the use of integrated water resources management in a single system which is built up by a river basin will help in water resources. This study was focused on water management issues: some of the principal causes of water shortages in UMdloti River are discussed. The current situation of water supply and demand at present is discussed. It also addressed some essential elements of reasonable, cooperative and sustainable water resources management solutions. Many developing countries are characterized as there is limited data availability, water scarcity and decrease of water levels in the dams. The eThekwini municipality is also having similar problems. Water resources have been modelled under this limited data using the hydrological modelling techniques by assessing the streamflow and observed data. The aim of the study was to address the issue of water management how water supply sources can be sustained to be manageable to meet the population growth demand considering the capacity of Hazelmere Dam demand downstream of the dam. Hydrological models, simulation, and decision making support systems were used to achieve all the research objectives. Hazelmere Dam has been modelled so that it can be used efficiently for the benefit of all users downstream of the dam for their economic and ecological benefits. Monthly reservoir inflow data for Hazelmere Dam was obtained from the Department of Water Affairs, South Africa. The nature of data is streamflow volume in mega liter (Ml) recorded for every month of the year. This was converted to mega cubic meter (Mm3) for use in the analysis herein. A period spanning 19 years of data (1994 – 2013) was used for the analysis. Six parametric probability distribution models were developed for estimating the monthly streamflow at Hazelmere Dam. These probability distribution functions include; Normal, Log-Normal (LN), Pearson III, Log-Pearson type III (LP3), Gumbel extreme value type1 (EVI) and Log-Gumbel (LG). It was observed that UMdloti River is smaller when compared with other rivers within the KwaZulu-Natal Province which could make it difficult to implement integrated water resources management. The hydro-meteorological data collected also has some limitations. The meteorological stations are far away to one another and this would make it difficult to attach their readings with the corresponding water basin. The comparison between the observed and simulated streamflow indicated that there was a good agreement between the observed and simulated discharge. Even though, the performance of the model was satisfactory, yet, it should not be generalized equally for all purposes. The erosion on the study area must be addressed by the stakeholders. It must be minimized in order to sustain the water resources of the UMdloti River. Erosion has a bad impact on the environment because it causes environmental degradation as well. Further investigations are recommended that account for the geological characteristics and the source of the base flow to make sure the rate of groundwater is sufficient for any future developments. Harnessing more energy from existing water sources within the frontier of the country is important in capacitating the South African Government’s commitment to reduction of the country’s greenhouse gas emissions and transition to a low-carbon economy while meeting a national target of 3,725 megawatts by 2030. This study also aimed to determine the amount of energy that can be generated from Hazelmere Dam on the uMdloti River, South Africa. Behavioral analyses of the Hazelmere reservoir were performed using plausible scenarios. Feasible alternative reservoir operation models were formulated and investigated to determine the best operating policy and power system configuration. This study determines the amounts of monthly and total annual energy that can be generated from Hazelmere reservoir based on turbines efficiencies of 75%, 85% and 90%. Optimization models were formulated to maximize hydropower generation within the constraints of existing abstractions, hydrological and system constraints. Differential evolution (DE) optimization method was adopted to resolve the optimization models. The methodology was applied for an operating season. The optimization models were formulated to maximize hydropower generation while keeping within the limits of existing irrigation demands. Differential evolution algorithm was employed to search feasible solution space for the best policy. Reservoir behavioural analysis was conducted to inspect the feasibility of generating hydropower from the Hazelmere reservoir under normal flow conditions. Optimization models were formulated to maximize hydropower generation from the dam. DE was employed to resolve the formulated models within the confines of the system constraints. It was found that 527.51 MWH of annual energy may be generated from the dam without system failure. Storage was maintained above critical levels while the reservoir supplied the full demands on the dam throughout the operating period indicating that the system yield is sufficient and there is no immediate need to augment the system.