VUT DigiResearch

Digiresearch is the VUT electronic open access archive. Its purpose is to collect, distribute and preserve the research performed by the VUT Research community

 

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Assessing the effectiveness of the water purification process in removing clostridium perfringens spores as a surrogate for protozoan parasites
(Vaal University of Technology, 2022-12) Schubart, Annah Lindiwe; Swanepoel, Annelie, Dr.; Marrengane, Zinhle; Ssemakalu, Cornelius Cano, Prof.
The World Health Organization (WHO) provides guidelines for assessing the microbiological risk associated with drinking water using a Quantitative Microbial Risk Assessment (QMRA). Microbiological risk in water may arise from pathogens such as protozoan parasites Giardia and Cryptosporidium. The risk presented by Giardia and Cryptosporidium in water is increased by the fact that these pathogens are resistant to disinfection by chlorine. It is costly to monitor treated water for the presence of Cryptosporidium and Giardia, therefore a surrogate was used to carry out the evaluations. This research first determined the efficacy of the conventional water treatment processes in removing Clostridium perfringens spores as a surrogate for protozoan parasites (Cryptosporidium oocysts and Giardia cysts). We estimated the number of protozoan parasites that can pass through the drinking water treatment barriers. This removal efficiency can then estimate the number of protozoan parasites that can survive drinking water purification. The study conducted a simulated jar test under predetermined conditions using three different coagulation combinations: (i) Polyelectrolyte, (ii) polyelectrolyte and slaked lime, and (iii) slaked lime and activated sodium silicate. The three regimens (polyelectrolyte, polyelectrolyte and slaked lime, and slaked lime and activated sodium silicate) were tested each at low temperatures (12.8 ± 0.4°C), normal temperatures (17.2 ± 0.9°C), and at high temperatures (20.3 ± 0.1°C). The three coagulant combinations (polyelectrolyte, polyelectrolyte and slaked lime, and slaked lime and activated sodium silicate) were also tested under normal temperature conditions at high water turbidity. Percentage and log reduction for C. perfringens spores were calculated for each water treatment unit. A percentage reduction for turbidity was calculated for each water treatment unit. Pre-experiments were conducted to determine the suitability of the filter membranes and media to be used for analysing the water samples for the study. The 0.45 μm filter membrane and the Perfringens Agar Base (PAB) were selected and used. Experiments conducted at low temperatures (12.8 ± 0.4°C) showed C. perfringens spore log reductions of infinity or 100% when the polyelectrolyte and a combination of polyelectrolyte and slaked lime were used. Under normal conditions (17.2 ± 0.9°C), C. perfringens spores log reductions of up to 2.0 or 98.9 ± 0.4% were observed using a combination of polyelectrolyte and slaked lime. However, when experiments were conducted at high temperatures (20.3 ± 0.1°C), C. perfringens spore log reductions of infinity or 100% were observed with the polyelectrolyte. At increased turbidity, C. perfringens spores log reductions of up to 2.0 or 99.1 ± 0.1% were observed with the polyelectrolyte. The lowest turbidity reduction of up to 24.1 ± 0.8% was observed when slaked lime and activated sodium silicate were used at 20.3 ± 0.1°C. The highest turbidity reduction of up to 99.0 ± 0.1% was observed using a combination of polyelectrolyte and slaked lime for high-turbidity water. This study showed that water purification steps could remove up to 100% of C. perfringens spores when a polyelectrolyte or a combination of polyelectrolyte and slaked lime are used under varying conditions. Therefore, this study recommends using a polyelectrolyte or a combination of a polyelectrolyte and slaked lime for water treatment under specified conditions. A polyelectrolyte and slaked lime combination is recommended for high-turbidity water.
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Mechanical and crystallisation properties of polyetheretherketone polymer from dry solid lubricants
(Vaal University of Technology, 2023-06) Ladipo, Taiwo Lolade; Nziu, P. K., Dr.; Masu, L. M., Prof.
Polyetheretherketone (PEEK) polymer suffers high viscosity during fused filament fabrication (FFF). Adding solid lubricants as fillers to PEEK should reduce its viscosity. However, very little research has been conducted on the tribological properties of PEEK printed using FFF. This study dealt with filament-making, tensile properties, crystallinity, and tribological characterisation of FFF-printed PEEK impregnated with dry solid lubricants. PEEK, graphite, and Molybdenum disulphide (MoS2) were sourced, tested, and analysed. Three active functional groups were found in the PEEK: oxy, phenyl, and carbonyl. While the MoS and graphite powder indicated sulfide and Carbon functional groups. The PEEK and both lubricants had an average particle diameter of 100 microns. Three weight ratios of each solid lubricant were mechanically blended into PEEK powder. Seven samples were prepared using a tabletop extruder. Each filament was 3D printed into 35 dog bones and seven discs for ultimate tensile testing, X-ray diffraction analysis (XRD), and disc on-pin testing. The diagrammatic Hermans-Weidinger approach with XRD analysis was used to evaluate the degree of crystallinity. It was established that the MoS2-filled PEEK is better than the graphite-filled PEEK. MoS2-filled PEEK reinforces as the weight content of MoS2 increases up to 104 MPa at 10 wt%. This reinforcement suggests perfect adhesion between PEEK and MoS2. On the other hand, the graphite-filled PEEK decreased in tensile strength to 36 MPa due to agglomeration at 10 wt% filling of graphite. No existing planar peaks were destroyed by introducing MoS2 and graphite, but a new peak was formed per solid lubricants and intensified on the increase of the solid lubricants. Generally, the MoS2-filled PEEK has the best-recorded crystallinity level at about 70% for 5 wt.% while the lowest recorded value was 3 wt.% of graphite valued at 31%. The tribological observation showed that the average response time for pure 3D-printed PEEK is about 950 seconds, indicating that FFF-printed PEEK has a weak capacity to minimise friction independently. Impregnating PEEK with MoS2 and Graphite decreases the response time by about 73%. However, the coefficient of friction of graphite-filled PEEK was initially reduced but started increasing after 5 wt.% due to agglomeration. The MoS2-filled PEEK has a minimum of 30 % decrease in the wear rate, while the graphite-filled PEEK initially decreases to 9% but later spikes to about 6% due to agglomeration. The agglomeration of Graphite in PEEK at a high weight fraction makes graphite a non-perfect choice for FFF compared to MoS2.
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Trade union members' perception of the effectiveness of and satisfaction with their unions in municipalities in Gauteng South
(Vaal University of Technology, 2021-10) Mbuli, Sibongile; Dhurup, M., Prof.; Joubert, P. A., Prof.
For decades, trade unions have been entrusted to represent and protect the interest of employees in a workplace. They have been the voices of employees throughout the globe. Throughout the years, they have successfully built strong relationships with their union members and obtained recognition in many organisations. Consequently, trade unions have negotiated better working conditions and better wages for their members. However, in recent years there have been numerous reports of membership decline in trade unions globally. The primary objective of the study is to determine trade union members’ perceptions of the effectiveness of and satisfaction with their trade unions in municipalities in Gauteng south. To achieve the objective of this study, a quantitative research approach was used to examine the relationship between union effectiveness and member satisfaction among 330 union members. Furthermore, means and factor analysis were performed to determine the level of union effectiveness and member satisfaction among union members and to establish the underlying factors of the constructs, respectively. Additionally, correlation analysis was conducted to determine the strength and direction of the relationship between factors. Finally, regression analysis was performed to confirm the predictive relationship between factors. The findings of this study showed a positive correlation between union effectiveness and the four factors of member satisfaction, namely, conditions of employment, representation of union members, education and training and member service. The positive relationship between union effectiveness and member satisfaction indicates that union effectiveness has a huge impact on member satisfaction. A predictive relationship was observed between three factors of member satisfaction, namely, conditions of employment, representation of union members, and education and training; however, no predictive relationship was observed between union effectiveness and member satisfaction. Based on the findings it was recommended that trade unions ought to do more for their members and to show that they have their best interests at heart. According to the findings, union members currently may feel neglected and not accurately represented by their trade unions.
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Determining South African National Parks' contribution to sustainable development goals in host communities: A case study of Kruger National Park
(Vaal University of Technology, 2023-03) Mabibibi, Mashudu Andra; Thwala, K. C., Dr.; Dube, K., Prof.
The study examines and evaluates the Kruger National Park’s role in assisting its host communities to meet their Sustainable Development Goals agenda. The study is triggered by the fact that the tourism industry is criticised for its unsustainable practices and exploitative proclivities. The existence of knowledge gaps on how the KNP operations and activities fullfil and lead to the realisation of SDGs, therefore, warrants research so as to generate information and strategies that are beneficial not only to the KNP only, but also to the communities that are located in its proximity. The study conducted between March and October 2021, used a case study reseach design in a mixed method approach to answer the research questions. The emperical work comprised of in-depth interviews (=30) with key informants identified by KNP gatekeppers; surveys (=70) with community members; a secondary literatire review; and observations of community projects done by host communities - artefacts sold within and outside the park, infrastructure developments in communities and agricultural practices in host communities. Thematic analysis was used to catergorise the data according to the corresponding SDG categories. The study found that despite hurdles such as climate change, diminished funding, and COVID-19, among other such factors, the Kruger National Park aided communities in meeting at least 15 of the 17 SDGs goals. The various projects of the KNP address all the SDGs except for SDG7 on affordable and clean energy and SDG 14 on life below water where no identified project could be directly linked to those SDGs. It was also found that some of the KNP’s flagship projects were ensuring economic emancipation, delivering quality education, and alleviating poverty and inequality, all of which interlink with conservation and environmental protection. The projects have also fostered some sense of ownership by local communities, a move which has helped improve relations between the park and host communities. The study recommends continuous monitoring of the role that protected areas can play in addressing the 17 SDGs. Continuous monitoring will allow for necessary interventions to be made at the policy and practical levels.
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Surface modification of biochar composite made from tea waste for the removal of selected organic pollutants from aqueous medium
(Vaal University of Technology, 2022-11) Mashoene, Tumelo Nortica; Lawal, A., Dr.; Taka, A. Leudjo, Dr.; Klink, M., Prof.
Domestic, agricultural, and industrial waste has been investigated as a substitute for activated carbon adsorbents. This research converted waste tea-based adsorbent, coupled with reduced graphene oxide, and further modified with deep eutectic solvents. This innovative biochar modification was investigated to overcome the limitations of the tea-waste biochar nanocomposite alone and the removal of organic contaminants from simulated wastewater. Fourier Transformed Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM–EDS), Brunauer, Emmett, and Teller (BET) surface area analysis, and pH at point of zero charge (pH PZC) was used to characterize the synthesized materials (biochar, biochar/reduced graphene oxide (biochar/rGO), biochar/reduced graphene oxide/deep eutectic solvent-cetyltrimethylammonium bromide (biochar/rGO/DES-CTAB), and biochar/reduced graphene oxide/deep eutectic solvent-glycerol (biochar/rGO/DES-glycerol)). The results showed that the principal material biochar was modified by a show of added functional groups and surface structural changes. The materials biochar, biochar/rGO, biochar/rGO/DES-CTAB, and biochar/rGO/DES-glycerol were applied for the removal of ZDV and phenol from the aqueous medium. Batch adsorption studies were conducted to optimize operating parameters such as adsorbent dose, solution pH, contact time, and initial concentration. Pseudo-first-order (PFO), Pseudo-second-order (PSO), and intraparticle diffusion (IPD) kinetic models were determined to investigate the mechanism of the adsorption process. The coefficient of correlation, R2, was used to determine the best fit of the kinetic models. The adsorption results showed that DES-glycerol-modified adsorbent was more efficient in removing the pollutants ZDV and phenol than biochar, biochar/rGO, and biochar/rGO/DES-CTAB adsorbents. In addition, the results showed that an acidic medium of pH 2.00 and a contact time of 1h30min and 30 min is sufficient for removing ZDV and phenol respectively, from an aqueous medium. The experimental data best fit into PSO models and assumed a variety of interactions between the adsorbent surface and adsorbate molecules and IPD wasn’t the only rate-determining step. The Langmuir and Freundlich models further examined the experimental data to assess the adsorbate-adsorbent interactions at equilibrium. Equilibrium experiments revealed that adsorption adhered to the Langmuir isotherm, demonstrating the homogeneity of adsorption sites. This study demonstrates the feasibility of the conversion and modification of common tea waste into a useful adsorbent for the remediation of organic contaminants from wastewater, thus creating an opening for the application of waste tea-based adsorbent in industrial settings.