WIReDSpace

Welcome WIReDSpace(to Wits Institutional Repository on DSpace)

For queries relating to content and technical issues, please contact IR specialists via this email address : openscholarship.library@wits.ac.za, Tel: 011 717 4652 or 011 717 1954

 

Communities in WIReDSpace

Select a community to browse its collections.

Now showing 1 - 5 of 19

Recent Submissions

No Thumbnail Available
Item
The removal of diclofenac, cypermethrin, ibuprofen and naproxen from wastewater using advanced membrane technology
(University of the Witwatersrand, Johannesburg, 2024) Ngwamba, Pamela Nadia; Biyela, Precious
In recent years, emerging contaminants (ECs) such as pharmaceuticals, personal care products, endocrine-disrupting compounds, industrial additives, pesticides, nanomaterials, surfactant retardants, surfactants, and their metabolites and transformation products have been widely detected in both wastewater and water bodies. These compounds originate from a diverse range of point and non-point sources, consistently introducing them into wastewater and directly and/or indirectly introducing them to water bodies and the broader environment. The ECs have garnered attention due to their potential environmental impact and potential to induce adverse health effects. Conventional wastewater treatment processes are often not adequate to efficiently remove these compounds, thus leading to residual concentrations entering aquatic ecosystems and eventually, reaching drinking water systems. Although extensive research has been done over the past decade, there is limited literature covering the effects of long-term exposure to ECs, especially their metabolites and by-products, their fate, and toxicity levels. Consequently, additional research is imperative to establish limits and facilitate the regulation of these ECs. Advanced treatment methods, including ozonation, activated carbon filters, and membranes, have proven effective in eliminating ECs from wastewater. It must be noted that the efficiency of these advanced processes varies significantly. Despite extensive testing of various technologies, limitations still exist. Although most of the advanced treatments are highly effective, none of them have the ability to remove a mixture of ECs effectively. This variation is attributed to the nature of the compounds (e.g., hydrophobicity/hydrophilicity and solubility) and operational parameters like temperature, hydraulic retention time, and solids retention time. Nanocomposite membranes have been identified as a viable technology for the removal of ECs from wastewater due to their unique properties and enhanced performance when compared to conventional membranes. They are highly selective and efficient, additionally, they can be designed to specifically remove ECs such as pharmaceuticals, pesticides, and endocrine disruptors. Furthermore, they show greater antifouling properties, reducing the accumulation of contaminants on the membrane surface and extending the lifespan of the membrane, thereby lowering maintenance costs and improving operational efficiency. The aims and objectives of the research report were to compile a comprehensive literature review that highlights the importance of removing ECs from the environment; prepare and characterise four different flat-sheet membranes using polyvinylidene fluoride (PVDF) and imidazolium-based polymeric ionic liquids (PILs) and testing the membranes to determine the retention time and effectiveness of the prepared membranes in removing four different iv pharmaceutical products which are diclofenac, cypermethrin, ibuprofen, and naproxen. The hypothesis assumed that the imidazolium-based PILS/PVDF flat sheet membranes would yield a removal efficiency greater than 90%. This expectation was achieved, and all the membranes achieved a removal efficiency greater than 90%. Various studies have shown that nanocomposite membranes yield high removal rates. The synthesised membranes had better features than PVDF alone. The PVDF alone was found to have the largest pore size and the least retention time, although the removal efficiency was high. The blended membranes lead to higher porosity and retention times. They had smaller pore sizes as compared to plain PVDF; hence, the retention time was increasing. The higher the concentration of the imidazolium, the lower the contact angle measured; this is an indication of a more hydrophilic membrane surface. Hydrophilic membranes are less prone to fouling. The method investigated in this report is simple and can be easily reproduced. Based on the findings of this research report, the methods employed are precise, accurate, highly sensitive, and rapid.
No Thumbnail Available
Item
Determining the parameters for the sizing of sediment traps in the city of Johannesburg
(University of the Witwatersrand, Johannesburg, 2024) Raliengoane, Mankoe Francis; Fitchett, Anne
Urban land practices usually involve soil compaction and vegetation removal as cities expand and grow. This has led to increased flood peak flows and high stormwater runoff volumes associated with sediments, nutrients and other pollutants that load downstream water resources. To address these issues, there has been a growth of practices involving Sustainable Drainage Systems (SuDS) for managing stormwater runoff quantity and quality from urban areas. For example, this involves the application of attenuation ponds, and wetlands which temporarily store urban stormwater runoff, thereby reducing the sediment loads, pollutants, and release of peak flows to the downstream water resources at flow rates that mimic the pre-development flow patterns. This practice is gaining momentum in South African urban areas, which are supported by the policies and legislation set up by local authorities to address stormwater management. However, these stormwater application practices often do not perform according to their design capacities because they get filled with sediments and their effectiveness in attenuating peak flows is reduced. Therefore, it is important to reduce sediments coming into these structures by applying sediment traps and basins located at the head of such structures. The sediment trap’s main function is to slow down the stormwater runoff and help in the reduction of sediments before stormwater runoff is discharged out of the construction site and other disturbed areas. The City of Johannesburg Stormwater Management By-laws and Stormwater Design Manual have limited information for the management of sediment using sediment traps and basins and which parameters need to be considered when sizing sediment traps. Therefore, the main aim of the current research was to determine the parameters that should be considered when sizing sediment traps specifically for the city of Johannesburg. The following parameters: design rainfall, daily rainfall, catchment area, evaporation, land cover and land use, percentage of permeable and impermeable areas, topographical data, peak flow, runoff volume, catchment topography, soil types and infiltration characteristics, sediment particle size distribution, sediment settling velocity, sediment loading rate/yield were modelled through Personal Computer Stormwater Management Model (PCSWMM), ArcSWAT ArcGIS, and Excel Spreadsheet Models. Further, the sensitivity analysis was undertaken using different values of imperviousness and infiltration rates while observing peak flow and runoff volume changes in PCSWMM outputs. Modelling in PCSWMM showed that peak flows and runoff volumes increased due to an increase in the values of the imperviousness used. However, the range of infiltration rates for the soils in both sub- catchments S22 and S23 did not change the peak flows and runoff volumes. Though it was not the scope of the current study, it was observed that higher infiltration rates than the ones that were determined from the sub-catchments S22 and S23 indeed reduced peak flows and runoff volumes. On the other hand, particle settling velocity showed that gravel particles took a short time to settle and required a smaller sediment trap iii storage capacity. In comparison, silt particles took longer to settle and required a larger sediment trap storage capacity. Lastly, sediment yield from both sub-catchments S22 and S23 showed that sediment yield is driven by rainfall, whereby months with high rainfall had higher sediment yield than the months with low rainfall. It is therefore, concluded that the following parameters: design rainfall, daily rainfall, evaporation, land cover and land use, percentage of permeable and impermeable areas, topographical data, contributing catchment area, peak flow, runoff volume, catchment topography, soil types and infiltration characteristics, sediment particle size distribution, sediment settling velocity, sediment loading yield should be considered by the engineers, designers and planners when sizing sediment traps in the City of Johannesburg and possibly in other places as well.
No Thumbnail Available
Item
The impact of incorrectly sized bulk meters on water consumption and municipal revenue
(University of the Witwatersrand, Johannesburg, 2024) Rabé, Magdeleen; Ilemobade, A.
South Africa is a water-scarce country, characterised by lower-than-average rainfall and high water consumption rates, with Non-Revenue Water increasing despite water conservation efforts. Literature shows that bulk water meters are often incorrectly sized, increasing Apparent Losses from metering inaccuracies, resulting in revenue loss and negating the municipality’s water conservation and water demand management initiatives. This study investigates the impact of incorrectly sized bulk water meters (sized 40mm – 150mm installed at non-residential and multi-residential facilities) on municipal revenue by analysing flow logging data and metered consumption characteristics of 42 users. The methodology combines flow logging to analyse actual water consumption characteristics, assessment of meter operating flow ranges for optimal sizing, calculation of weighted accuracy for Apparent Loss estimation, and literature review on meter sizing and alternatives to consider regarding fire demand requirements. Highlights from this study are (a) the consumer profiling findings underscore the importance of aligning meter size with consumer water use patterns: consumption below the meter’s starting flow is observed at 50% of the stands analysed in the dataset, indicating over-sized meters; (b) 57% of the stands had on-site leakage, occurring at low flow rates where meters are most inaccurate; (c) two examples demonstrate the impact of incorporating fire demand, resulting in meter size changes from a 15mm to 100mm, and a 25mm to 150mm, respectively; (d) resizing meters for 35 stands is estimated to result in an additional municipal revenue gain of R636,876.92 within one year. Overall, the study highlights the importance of accurate meter sizing for reducing Non-Revenue Water, improving revenue generation, and enhancing water conservation efforts.
No Thumbnail Available
Item
Assessment of in-service durability performance of natural draft cooling towers in a petrochemical environment
(University of the Witwatersrand, Johannesburg, 2024) Shaw, Kyle Lloyd; Otieno, Mike
Effective temperature control is an important operation requirement in petrochemical processes, where Cooling Towers (CT) play a key role in efficiently lowering water temperature for reuse in various chemical processes. Natural draft cooling towers function as heat extraction systems, dissipating thermal energy from hot water into the atmosphere through cold air. However, many reinforced concrete cooling towers have exhibited signs of deterioration over time, such as cracking, corrosion, and structural misalignment, posing the risk of structural failure. To address these issues, structural condition assessment programs, aiming to inspect, repair, and monitor cooling towers to prevent structural collapse are of significant importance. The focus of this study investigates the durability of natural draft cooling towers in an aggressive petrochemical environment. With a focus on Sasol Secunda Natural Draft Cooling Towers, the research aims to identify and characterize the various concrete deterioration mechanisms, quantify durability parameters, and explore mitigation measures for both new and existing cooling towers. Concrete deterioration is a significant concern in structures exposed to harsh environments, affecting their global stability and service life. The study examines the role of cover concrete quality in resisting corrosive agents and assesses durability using South Africa's three durability index (DI) tests, including water sorptivity, chloride conductivity, and oxygen permeability. The study comprised of on-site assessments and laboratory testing methods to determine the durability performance of cooling towers. The approach includes the three durability index tests. On-site assessments include visual inspections and non-destructive testing (NDT) near areas displaying signs of deterioration. The significance of this research relies on the operational efficiency of cooling towers in petrochemical plants, their vulnerability to harsh conditions, and the need for durability design considerations at Front End Loading (FEL) engineering and planning. It aims to shift from prescriptive to performance-based design approaches and provide insights for maintenance and mitigation strategies. This study contributes to the knowledge of concrete durability in challenging environments, aiming to enhance the longevity and performance of critical industrial infrastructure, particularly natural draft cooling towers.
No Thumbnail Available
Item
Unlocking Sustainability: An Exploration of the Potential for Food Waste Conversion into Energy and Value-Added Products for Effective Landfill Diversion in South Africa
(University of the Witwatersrand, Johannesburg, 2024) Pereira, Gabriel Philip Alves; Fitchett, Anne
This research report examines the potential for transforming food waste into energy and value-added products as a sustainable strategy for diverting waste from landfills in South Africa. The study uses a social cost-benefit framework to evaluate various waste conversion technologies, including anaerobic digestion, aerobic composting, vermicomposting, and black soldier fly larvae, within South Africa's unique socio- economic and environmental landscape. The study combines quantitative waste composition analyses with technology evaluations, revealing significant landfilling costs and underscoring the economic and environmental urgency of strategic food waste diversion. Highlighting gate fees' critical role, the findings advocate adjusting these fees to incentivise sustainable waste management practices. Notably, Black Soldier Fly larvae and Vermicomposting technologies emerge as dual-benefit strategies for waste reduction and resource recovery. The report calls for policy and infrastructure advancements to enable the broad adoption of these technologies, emphasising their importance in achieving sustainability and economic objectives.