Faculty of 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.
Applications of artificial intelligence to photovoltaic systems : a review
(MDPI AG, 2022) Mateo Romero, Héctor Felipe Mateo; González Rebollo, Miguel Ángel González; Cardeñoso-Payo, Valentín; Alonso Gómez, Victor Alonso; Redondo Plaza, Alberto Redondo; Moyo, Ranganai Tawanda; Hernández-Callejo, Luis
This article analyzes the relationship between artificial intelligence (AI) and photovoltaic (PV) systems. Solar energy is one of the most important renewable energies, and the investment of businesses and governments is increasing every year. AI is used to solve the most important problems found in PV systems, such as the tracking of the Max Power Point of the PV modules, the forecasting of the energy produced by the PV system, the estimation of the parameters of the equivalent model of PV modules or the detection of faults found in PV modules or cells. AI techniques perform better than classical approaches, even though they have some limitations such as the amount of data and the high computation times needed for performing the training . Research is still being conducted in order to solve these problems and find techniques with better performance. This article analyzes the most relevant scientific works that use artificial intelligence to deal with the key PV problems by searching terms related with artificial intelligence and photovoltaic systems in the most important academic research databases. The number of publications shows that this field is of great interest to researchers. The findings also show that these kinds of algorithms really have helped to solve these issues or to improve the previous solutions in terms of efficiency or accuracy.
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.
Barrier and biodegradable properties of corn starch-derived biopolymer film filled with nanoclay fillers
(SAGE Publications, 2016-12-18) Mohan, T. P.; Devchand, Kay; Kanny, Krishnan
The objective of this work is to study the effect of nanoclay fillers on the biodegradation and barrier properties of corn starch polymer-based biofilm. Starch derived from corn plant source was used to prepare a biofilm by plasticization method. The barrier properties, namely, water absorption, moisture permeation, oxygen permeation and swelling of unfilled and nanoclay-filled corn starch biofilms were examined. The results indicate: ∼22% reduced water absorption, 40% reduced moisture uptake, 30% reduced oxygen permeation and 31% reduced swelling for 2–3 wt.% nanoclay-filled biofilm, when compared with unfilled biopolymer. The biodegradation result of unfilled and nanoclay-filled film series indicates that the nanoclay addition delays the biodegradation and is a function of nanoclay content in the film. The tensile, dynamic mechanical analysis and biodegradable studies were conducted on the biopolymers before and after water absorption, and the result shows that the nanoclay-filled biopolymer increased these properties when compared with unfilled biopolymer even after water absorption and is dependent on the nanocomposite structure and morphology as examined by X-ray diffraction and transmission electron microscopy analysis.
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.
A controlled deflection routing and wavelength assignment based scheme in Optical Burst Switched (OBS) networks
(Walter de Gruyter GmbH, 2020-07-05) Nleya, Bakhe; Khumalo, Zephaniah Philani; Mutsvangwa, Andrew
Abstract - Heterogeneous IoT-enabled networks generally accommodate both jitter tolerant and intolerant traffic. Optical Burst Switched (OBS) backbone networks handle the resultant volumes of such traffic by transmitting it in huge size chunks called bursts. Because of the lack of or limited buffering capabilities within the core network, burst contentions may frequently occur and thus affect overall supportable quality of service (QoS). Burst contention(s) in the core network is generally characterized by frequent burst losses as well as differential delays especially when traffic levels surge. Burst contention can be resolved in the core network by way of partial buffering using fiber delay lines (FDLs), wavelength conversion using wavelength converters (WCs) or deflection routing. In this paper, we assume that burst contention is resolved by way of deflecting contending bursts to other less congested paths even though this may lead to differential delays incurred by bursts as they traverse the network. This will contribute to undesirable jitter that may ultimately compromise overall QoS. Noting that jitter is mostly caused by deflection routing which itself is a result of poor wavelength and routing assigning, the paper proposes a controlled deflection routing (CDR) and wavelength assignment based scheme that allows the deflection of bursts to alternate paths only after controller buffer preset thresholds are surpassed. In this way, bursts (or burst fragments) intended for a common destination are always most likely to be routed on the same or least cost path end-to-end. We describe the scheme as well as compare its performance to other existing approaches. Overall, both analytical and simulation results show that the proposed scheme does lower both congestion (on deflection routes) as well as jitter, thus also improving throughput as well as avoiding congestion on deflection paths.
Degree accreditation report auto-generation by logic encoding and processing
(2021-11-10) Chetty, Manimagalay; Rawatlal, Randhir
Maintaining the accreditation profile of an academic programme is a key activity in so-called professional degrees such engineering, commerce and law. The complexity of the accrediting criteria tends to rise over time as accrediting bodies require quantitative evidence of competence of increasingly specific graduate attributes. Evaluation of graduate attributes may therefore require complex logic processing which challenges the human capacity. This has the negative side effect of discouraging curriculum revision not for pedagogic reasons but simply due to the complexity of evaluating complex logic patterns against a data set whose structure is shifting. These challenges can be overcome through the application of logic encoding and processing. A computing system is better suited to such processing tasks since logic processing is fundamental and well-established to such systems. On the other hand, the efficient representation of a complex accreditation logic rule base then becomes the challenge. This paper describes the representation of the accreditation logic of eight engineering academic programmes at the Durban University of Technology through the AutoScholar Advisor System in preparation for evaluation by the Engineering Council of South Africa. It is shown that the system generates accurate reports even with deeply nested logic structures and with changes in curriculum over time.
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
Design optimization of anisotropic pressure vessels with manufacturing uncertainties accounted for
(Elsevier, 2013-04) Tabakov, Pavel Y.; Walker, Mark
Accurate optimal design solutions for most engineering structures present considerable difficulties due to the complexity and multi-modality of the functional design space. The situation is made even more complex when potential manufacturing tolerances must be accounted for in the optimizing process. The present study provides an original in-depth analysis of the problem and then a new technique for determining the optimal design of engineering structures, with manufacturing tolerances accounted for, is proposed and demonstrated. The numerical examples used to demonstrate the technique involve the design optimization of anisotropic fibre-reinforced laminated pressure vessels. It is assumed that the probability of any tolerance value occurring within the tolerance band, compared with any other, is equal, and thus it is a worst-case scenario approach. A genetic algorithm with fitness sharing, including a micro-genetic algorithm, has been found to be very suitable to use, and implemented in the technique.
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.