Faculty of Science (ETDs)

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A comprehensive analysis of urban river pollution – the case of the Hennops river in Gauteng Province, South Africa
(University of the Witwatersrand, Johannesburg, 2023) Letseka, Thabiso Esaiah; Chimuka, L.; Richards, L.H.
The water quality of rivers is declining at an alarming rate due to pollution from anthropogenic activities associated with urbanization. To ensure ecological restoration and management of rivers, engaging in pollutant source apportionment, evaluation, and monitoring of water quality is of great significance. The study delivers a comprehensive assessment of the state of pollution in the Hennops river catchment facing pollution threats from rapid urbanization. The water quality assessment of the Hennops river was performed through chemical, microbiological, microplastics analysis and ecotoxicological approaches, spanning from upstream region in Tembisa to the downstream Hartbeespoort Dam. Standard methods were employed to assess physiochemical properties of the river’s water. Electrical conductivity and pH fell within the accepted criteria based on the standard water quality guidelines. However dissolved oxygen (DO) levels were below acceptable limits, ranging from 1.53 mg L-1 to 6.47 mg L-1. This signifies a substantial demand for oxygen in the river, likely due to the discharge of sewage from leaking pipes and wastewater treatment plants. This sewage introduces a high volume of organic matter, leading to an increased oxygen demand in the water. Microbiological pollution indicators were employed to assess the microbial water quality of the river. The study's findings revealed elevated bacterial counts, with Escherichia Coli (E. coli) reaching up to 2 250 cfu mL-1 upstream and decreasing to 30 cfu mL-1 downstream. These high counts suggest faecal contamination in the river water. Similar trends were observed with total coliform counts, high coliform counts 170 000 cfu mL-1 in the upstream which remained detectable even downstream and beyond the Hartbeespoort Dam, despite the dilution effects within the dam. The dam was identified as the primary repository for pollution originating upstream. Grab sampling followed by solid phase extraction (SPE) and the passive sampling using a Polar Organic Integrative Sampler (POCIS), were employed as sample preparation methods for preconcentration of methocarbamol, etilefrine, nevirapine, carbamazepine and venlafaxine from river water with subsequent analysis on Liquid Chromatography coupled to quadrupole time of flight mass spectrometry. Both methods yielded good figures of merit with limits of quantification in the range of 0.57 to 2.12 ng mL-1 for POCIS and 0.19 to 1.82 ng mL-1 for SPE. The compounds were detected in the water but at low levels (µgL-1 ), with detected concentrations of carbamazepine in the range 0.62 ng mL-1 – 0.32 ng mL-1 , methocarbamol detected in the range 0.11 ng mL-1 - 0.14 ng mL-1 and venlafaxine 0.50 ng mL-1 – 0.44 ng mL-1 using POCIS. The detected concentrations using SPE were in the range 0.13 ng mL-1 – 0.19 ng mL-1 for carbamazepine, while nevirapine and venlafaxine were detected although below limit of quantification. This underscores the advantage of using passive samplers, which enable the detection of fluctuating contaminant concentrations over time, in contrast to the one-time measurements obtained through grab sampling. In the case of microplastics in the water and sediment samples, five polymer types were identified: polyethylene (PE), polypropylene (PP), high density polyethylene, (HDPE), polyester and polystyrene. The predominant polymer type in surface water was PE (48.6 %), and that in sediment was PP (52.7 %). PE and PP were the most abundant polymer types in both phases, and as these also the leading polymers in plastics production. 80% of the identified microplastics were found to be fibre with most dominant sizes of 1-2 mm for sediments and 0.5-1 mm in water samples. The conducted tests deemed the river water not suitable for irrigation, drinking or recreational purposes and not capable to support aquatic life.
Comparative Analysis of Water Hyacinth Efficiency as Biosorbent and Phyto remediating Plant for Removal of Lead (Pb) Water Contaminants
(University of the Witwatersrand, Johannesburg, 2023-08) Nwagbara, Victor Uzoma; Parrini, Francesca; Newete, Solomon
One of the major problems facing the modern society is the issues of water contamination. The ability of aquatic plants to serve as both heavy metal biomarkers and phytoremediators has been advocated for many years. The purpose of this study was therefore to compare the efficacy of water hyacith as a biosorbent and phytoremediating plant for removal of lead from contaminated waters. Dry and fresh water hyacinth biomass were exposed to Pb-contaminated water at different time intervals of 1, 7, 14 and 21 days. The results showed that with the increase of the exposure time, the Pb removal capacity of the plant biomass also increased. The Pb water concentration in day 1 and day 7 were significantly different from those in day 14 and day 21 which were not significantly different from each other. The average Pb removal from the Pb-treated waters for the different time exposure of 1, 7, 14 and 21 days in the fresh water hyacinth biomass were 40%, 56%, 78 % and 79%, respectively, the highest reduction being in the latter. The biomass of the freshwater hyacinth roots had the highest Pd concentration compared to the shoot. On The other hand the average Pb removal by the dry water hyacinth biomass were 78.9 %, 78.5%, 78.3 % and 78.3% for day 1, 7, 14 and 21 respectively, showing no significant difference between the different time series exposure. This suggests the instant adsorption of Pb by the dry plant material from the first day of exposure, after which the active sites for adsorption saturates to accommodate any further Pb ion uptake. There were some plant stresses such as leaf chlorosis, and significant decrease in biomass weight and length of leaf-2 petiole in the lead-treated fresh water hyacinth plants compared to the controls (Pb-free water hyacinth plant). Thus, this study confirms that the largest removal by the dry water hyacinth biomass, occurred in the first day as opposed to the last day (day 21) by the freshwater hyacinth biomass.
Evaluating the Effectiveness of Green Drop Audit Criterion in Relation to Its Link to Enforcement Protocol in South Africa
(University of the Witwatersrand, Johannesburg, 2022-08) Tshongweni, Olwethu Lenox; Tutu, Hlanganani; Richards, Heidi L.
The Green and Blue Drop programs are incentive-based regulatory systems based on the Department of Water and Sanitation's (DWS) realization that rewarding positive behaviour is more efficient and effective than penalizing undesirable behaviour. The Green Drop was developed for the Wastewater Quality Management Regulation certification program. In contrast, the Blue Drop was developed for the certification program for the Drinking Water Quality Management Regulation (Burgess, 2021). Most municipalities have accepted them and have raised awareness about the need for better efficiency in the wastewater sector. The Sand River, in Polokwane wastewater treatment works (WWTWs), was chosen as the research area for this study. This particular river was selected based on the premise of continuous non-compliance of the wastewater treatment plant and the resulting pressure it puts on the Sand River by compromising its quality, with the DWS not having a successful way of regulating and enforcing the water user to abide by the rules of the license that has been issued. This study aims to evaluate the effectiveness of the Green Drop Program audits and assessments about their link to the regulatory system within the DWS. Additionally, a risk assessment and cumulative risk rating are used to assess wastewater discharge into the Sand River in the Limpopo Province. Based on the observation made during the study, it appears that within the DWS organizational arrangements, the lack of coordination among the sectors (compliance monitoring, water quality management, the green drop program, and enforcement), lack of accountability, and the regulatory requirement of cooperation within DWS sectors have hindered implementation. Some of the non-compliance factors may be due to the misuse of funds meant for infrastructure development and difficulties relating to capacity, procurement, and management of the WWTWs. Moreover, DWS's absence of interactive data management systems and business processes contributes to non-compliance. The Polokwane WWTW, directly linked to the Sand River, is overloaded and needs to comply with the Water Use Licence (WUL) conditions. For example, the 21 August 2022, this facility was found to be non-compliant by 69.01%, collectively with administration and technical conditions of the WUL issued to the facility (DWS, 2022c). In addition, this investigation discovered that the Polokwane facility, which has been operating outside of regulations for the past four years, therefore, as calculated in equation 7 could be responsible for 72.3% of the hazards to people's health, the quality of the river's water, and the aquatic ecosystem life in the Sand River in a single month. As much as some municipalities do not perform according to the desired standards, there have been a few noticeable, well-performing ones reported in the green drop report released in 2022. These include Langebaan WWTW (90%), Riebeek Valley WWTW (97%), Gansevallei WWTW (84%), and Wellington WWTW (95%), and this illustrates that the Green Drop Certification is achievable if the municipalities follow and adhere to the Water Use Authorization (WUA) issued them (DWS, 2022b). The DWS must integrate the internal structures or link sectors responsible for monitoring and regulating municipal water service facilities and incentivize performing facilities to improve their performance. Additionally, facilities with minor compliance issues, such as water quality, must be referred to the Water Quality Management (WQM) unit for further investigation and recommendations. However, those non-compliances of authorized wastewater treatment facilities that require regulatory attention must be referred to the compliance monitoring sector through the system for compliance monitoring. Lastly, those facilities that are not authorized must be directed to enforcement for further action. Therefore, using the Integrated Regulatory Information System (IRIS) as the umbrella body for both database and work-based information has an imperative role that can curb some of the issues faced by the DWS. Standard operating procedures (SOPs) should guide all interactions between these systems.
Inclusion of nano-silver compounds in RO membranes as solutions to fouling by microbes and natural organic matter during seawater desalination
(University of the Witwatersrand, Johannesburg, 2023-08) Nchoe, Obakeng Boikanyo; Moloto, Nosipho; Sikhwivhilu, Keneiloe; Tetyana, Phumlani
The access to safe and potable water has become a salient discussion for governments across the globe. This is due to pronounced levels of the decline in volumes of available freshwater. Attributions to this phenomenon are mainly climate change, eutrophication, discharge of untreated effluent, heightened irrigation, and industrialization. Currently exploited freshwater sources are rivers, lakes, dams, glaciers, and aquifers. However, inconsistent rainfall patterns have rendered some of these sources as ‘stressed’, which is exacerbated by exponential population growth and misallocation of available freshwater. In hindsight, seawater was identified as a possible source of potable water. However, the high levels of salinity and miscellaneous contaminants (i.e., pathogens and natural organic matter) necessitates treatment of seawater prior its usage. Therefore, the purpose of this work is to develop rugged polyamide thin film nanocomposite (TFN) reverse osmosis (RO) membranes with antifouling properties for seawater desalination. TFN were fabricated by the inclusion of silver-based (i.e., silver sulfide) nanoparticles during interfacial polymerization of the polyamide active layer. Silver compounds are known to have superior antibacterial and photocatalytic properties, due to plasmonic and photo absorption properties. For this reason, silver oxide (Ag2O), silver sulfide (Ag2S), and silver chloride (AgCl) nanoparticles (NPs) were colloidally synthesized. These were then characterized and evaluated in photocatalytic and antibacterial applications. Cytotoxicity studies were also done to determine which of these NPs pose less risk to human health. The consolidation of data from these applications advised which of these NPs would be suitable for incorporation into the polyamide layer to produce fouling resistant TFN. Microscopic analysis depicted well-defined shapes, with average sizes of 23.0±5.7 (Ag2O), 30.6±7.4 (Ag2S), and 10.6±7.2 nm (AgCl). X-ray diffraction determined Ag2O, Ag2S, and AgCl NPs to have cubic, monoclinic, and cubic lattices, respectively. Optical spectroscopy determined Ag2O, Ag2S, and AgCl NPs to have band gap energies of 2.97, 3.11, and 3.05 eV, respectively. These observations inferred that crystalline NPs that exhibit surface plasmon resonance (SPR) in the visible region were successfully synthesized. SPR is a desired characteristic for photocatalysts, and indeed Ag2O, Ag2S, and AgCl NPs achieved humic acid degradation (HA) efficiencies of 86.2, 88.1, and 76.5%, respectively. In antibacterial studies, the broth micro-dilution method indicated that the minimum inhibitory concentration (MIC) values against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) for Ag2O, Ag2S and AgCl NPs were 0.03125, 0.125, and 0.125 mg/mL, respectively. The well-diffusion tests showed that Ag2O NPs had the largest zones of inhibition (ZOI), followed by Ag2S, then AgCl NPs. These observations demonstrated the concentration-dependent mitigation of bacterial cell proliferation. The NPs were further tested for cytotoxicity against human embryotic kidney 293 (HEK 293) cells. It was found that the cytotoxic concentration that rendered 50 % viability (CC50) were 0.0302, 0.3606 and 0.3419, and were obtained for Ag2O, Ag2S and AgCl NPs, respectively. This data implied that Ag2O NPs were the most toxic, while Ag2S and AgCl NPs were least toxic. In light of the above, Ag2S NPs were selected to be incorporated into TFN RO membranes. TFN RO membranes were fabricated by the addition of three different concentrations of Ag2S NPs in the aqueous phase to form the active polyamide (PA) layer on a polysulphone (PSF) support, namely 20, 30, and 50 mg. Fourier transform infrared (FTIR) spectroscopy detected vibrational peaks at 1659 cm-1 (amide I C=O stretch), 1542 cm-1 (amide II C-N stretch) 1481 cm-1 (C-H bend), 1385 cm-1 (C-O stretch), 1242 cm-1 (C-N stretch), and 779cm-1 (aromatic C-H and C=C wagging). The presence of aromatic and amide functional groups corroborated the formation of the TFN active layer, which is responsible for RO filtration of dissolved ions in water. Moreover, atomic force microscopy (AFM) revealed that average surface roughness decreased with increased Ag2S NP loading. TFN loaded with 20, 30, and 50 mg Ag2S NPs recorded water contact angles (WCA) of 54.1, 45.4, and 43.3°, respectively. The WCA of thin film composite membranes (TFC) without Ag2S NPs was recorded to be 73.5°. This demonstrated that the inclusion of Ag2S NPs increased surface hydrophilicity. In addition, salt rejection and water flux were higher for 30 mg loaded TFN (98 % and 32.7 L/m2h) compared to those of TFC (97% and 24.8 L/m2h). The bacterial growth inhibition was observed to be significantly high for 30 mg loaded TFN (80 %) compared to that of TFC (38 %). These observations indicate that the inclusion of Ag2S NPs significantly enhanced the performance of RO membranes and cost effectiveness of desalination.
Tailored Fabrication of MXene/Chitosan Nanocomposites as Efficient Adsorbents for Heavy Metals Removal from Wastewater
(University of the Witwatersrand, Johannesburg, 2023-08) Ibrahim, Yassmin Ahmed Ismail; Eid, Kamel; Ozoemena, Kenneth Ikechukwu
MXene (Ti3C2Tx) has been extensively utilized in water purification systems, including toxic metal ions removal, owing to the unique layered structure and abundant oxygen surface groups. However, challenges such as aggregation and solubility of Ti3C2Tx nanosheets in water have prompted the need for innovative strategies. In this study, we introduce a i3C2Tx-incorporated chitosan matrix (MX/CS) adsorbent designed to address solubility concerns during water treatment. MX/CS adsorbents are tested towards the capture of “cadmium” (Cd 2+) and “Zinc” (Zn2+) ions in aqueous solutions at varied pH values (i.e., acid, neutral and alkaline), initial ions concentrations (25, 50 and 100 ppm), and varied Ti3C2Tx loading (i.e., 1, 5 and 10), to study the optimization adsorption parameters. In addition, the Ti3C2Tx nanosheets were activated/alkalinized at ratio (2:1, i.e., 2MX:OH/CS), where more negative-ions sites are provided, thus, enhancing the preferential sorption for heavy metal ions in terms of high adsorption capacities, and kinetics than the non-activated samples (MX-10/CS). Freundlich isotherms are predominated for the Cd2+ and Zn2+ ions adsorption on both adsorbents. A selectivity study reveals that Zn2+ ions got adsorbed faster on the adsorbents than Cd2+ ions because of its low atomic radii and electronegativity. Finally, the adsorbents will be generated and prepared for additional adsorption cycles to test their stability. The second part of this work is to present the novel fabrication of multifunctional hydrophobic polymeric foam MX nanocomposites for large-scale ultrafast wastewater treatment. Likewise, the foam nanocomposite will be tested for the adoption of multi-ions solution over wide pH rage to demonstrate the applicability of the novel adsorbent for large-scale applications. Overall, this research contributes to the advancement of water treatment technologies by enhancing the stability of MXene-based adsorbents and introducing an innovative fabrication method for hydrophobic polymeric foam MX nanocomposites. The outcomes demonstrate the applicability of these novel adsorbents for efficient and scalable water purification solutions.
The characterisation of borehole water properties and soil salinity across seasons for the period 2016-2020 with some links to rainfall and sugarcane yield in the Makhathini Irrigation Scheme, KwaZulu-Natal
(University of the Witwatersrand, Johannesburg, 2024) Ndwamato, Ramabulana Cassius; Scholes, Mary
The sugar business in South Africa has a strong socioeconomic development focus in rural regions, creating jobs, giving a source of revenue, and constructing transportation and communication networks. Despite its benefits, the sugar sector has faced several obstacles mostly by Small-Scale Growers (SSGs), which have led to a decline in sugarcane production. This study analysed borehole water properties such as electrical conductivity, water levels, and temperature at the Makhathini Irrigation Scheme in KwaZulu-Natal. The quality of water from the Jozini/Pongola Dam used for irrigation was also analysed, in addition to the salinity levels of the soil at the irrigation scheme. Water from nineteen (19) boreholes within the irrigation scheme between 2016 and 2020 was collected every three months from January and tested. Annual water quality data collected upstream (PR1) and downstream (PR2) of the dam were obtained from the Department of Water and Sanitation. One kilogram of soil was collected from six sampling points, respectively, within the Makhathini Irrigation Scheme and sent for testing at the Agricultural Research Council Institute of Soil Water and Climate. Rainfall data and annual sugarcane yield data were obtained and analysed. The ANOVA results showed a significant (p < 0.05) difference in electrical conductivity (EC) between all 19 boreholes in the five-year data. The Tukey test also confirmed the electrical conductivity’s significant (p < 0.05) variation across all boreholes during dry and wet seasons. The borehole water level analysis shows that no significant (p > 0.05) difference was observed in dry seasons, but there was a significant difference in the wet seasons. The Tukey test also confirmed that the borehole water levels varied significantly during the wet season for the five-year study period, suggesting that the water levels were shallow in the wet seasons compared to the dry season. The borehole water temperature analysis indicates no significant (p > 0.05) difference for all seasons from 2016 to 2020. The water collected at PR1 suggests that the water from the dam is of acceptable quality for irrigation, while the return flow to the Pongola River at sampling point PR2 had high SAR, EC, and PO4 - concentrations. Samples collected downstream (PR2) show signs of pollution. This suggests that water contamination occurs when water passes through the Makhathini Irrigation Scheme. A t-test analysis reveals that pH, NO3 - , and NO2 have no significant (p > 0.05) difference, but SAR, EC and PO4 - were significant (p < 0.05). The measured parameters were compared to the Department of Water Affairs and Forestry standards for the quality of water used in agricultural irrigation. The correlation analysis between rainfall, borehole electrical conductivity, borehole water levels, and sugarcane yields revealed that while rainfall influenced borehole electrical conductivity, water levels, and sugarcane yield, the effect was minimal, possibly due to irrigation volumes. Rainfall had a positive effect on sugarcane production and EC but a negative effect on water levels. Soil salinity analysis demonstrated an increase in the soil's electrical conductivity with each passing year. The ANOVA analyses for sugarcane yield and soil salinity reveal statistically significant differences (p < 0.05). The accumulation of salts in the soil at the Makhathini Irrigation Scheme, also seen by the contaminated return flow to the Pongola River, reduces sugarcane yields. Water properties of the sugarcane irrigation water affect the soil salinity in the irrigation scheme and, consequently, the decline in sugarcane production by small-scale growers.
Trimetallic nanoparticles immobilised on polymeric membranes for the degradation of organic pollutants in water
(University of the Witwatersrand, Johannesburg, 2021) Kgatle, Masaku; Moloto, Nosipho; Sikhwivhilu, Keneiloe; Ndlovu, Gebhu
Water is one of the most essential resources in the world, but its scarcity has become an issue of global concern. The scarcity of water is largely the result of climate change, water pollution and increasing population growth which limits the availability of water resources. Moreover, South Africa has been making headlines since 2010 due to water shortages experienced. It is, therefore crucial to find cost-effective ways to expand the water supply and address the issue of water pollution. This study seeks to tackle the problem of water pollution emanating from textile industries. Over the last few years, nanotechnology and membrane technology have appeared as some of the most widely used methods for the mitigation of water pollution problems. Particularly, nanoscale zerovalent iron (nZVI) has emerged as one of the most broadly used nanoparticles in wastewater treatment and remediation owing to its low-cost and high effectiveness. However, because of its ease of aggregation and consequent loss of reactivity, nZVI is coupled with one or more transition metals to produce multimetallic systems. Nanoparticles alone quickly agglomerate and form large micro-scale particles owing to the magnetic forces thus losing their mobility and chemical reactivity. To avoid these issues, the nanoparticles are stabilized on polymeric membranes. In this study, two trimetallic nanoparticle systems were synthesized, characterized and tested for catalytic activity. The polyvinylpyrrolidone (PVP)-stabilized Fe/Cu/Ag nanoparticles were synthesized by the sodium borohydride chemical reduction method. These nanoparticles were characterized using XRD, XPS, EDX and TEM. The XRD, EDX and XPS techniques showed the presence of all three metals, including iron oxides due to the oxidation of iron in air. The obtained TEM images showed the characteristic core-shell morphology of the nZVI-based nanoparticles. The evaluation of the catalytic activity of the nanoparticles was conducted using methyl orange (MO) dye as the model pollutant and this showed a remarkable degradation efficiency within few minutes. The effect of parameters such as MO solution pH, initial MO dye concentration and nanoparticle dosage in MO degradation was investigated. The nanoparticles were found to have performed better at lower pH, lower initial MO dye concentration and higher nanoparticle dosage. The degradation of MO dye was monitored using UV-Vis analysis and occurred within 1 min. The degradation was found to follow a pseudo first-order kinetic model and was vastly influenced by the studied parameters. The analysis of by-products and reaction pathway were done using LC-MS and this further confirmed that the degradation of MO was indeed rapid. The Fe/Cu/Ag trimetallic nanoparticles were demonstrated as suitable and effectual alternative for the remediation of textile dye wastewater. For the second trimetallic system, three different trimetallic nanoparticles (Fe/(Zn/Ag), Fe/Zn/Ag and Fe/ Ag/Zn) with different metal addition sequences were synthesized. The prepared nanoparticles were characterized using XRD, EDX and TEM analyses. The techniques proved successful synthesis of the nanoparticles and XRD and EDX showed the presence of the three metals together with the oxides. The evaluation of the catalytic reactivity of the nanoparticles was conducted in a series of batch experiments using MO dye as the model pollutant. About 100% of the MO dye was degraded by Fe/ Ag/Zn trimetallic nanoparticles within 1 min and the second-order rate constant obtained was 0.0744 ppm- 1min-\ the rate of reaction was higher than that of the other trimetallic systems. Using Fe/ Ag/Zn trimetallic nanoparticles, parametric tests were conducted at different MO solution pH, initial MO concentration and nanoparticle dosage. The results showed that the reactivity of the Fe/Ag/Zn trimetallic nanoparticles was highly dependent on the aforementioned parameters. Like the Fe/Cu/Ag system, the Fe/Ag/Zn performed better at lower pH, lower initial MO dye concentration and higher nanoparticle dosage. The overall kinetic study showed the removal of MO using Fe/Ag/Zn system to follow a second-order kinetic model. The elucidation of the degradation pathway and MO by-products identification were done using LC-MS and the mechanism of degradation displayed the degradation of methyl orange to proceed via azo-bond cleavage. Moreover, the Fe/ Ag/Zn nanoparticles proved to be effective at degrading methyl orange dye and can be used to treat azo-dye wastewater from textile industries. The Fe/Cu/ Ag trimetallic nanoparticle system was immobilized on a polymethacrylic acid grafted polyethersulfone (PMAA-g-PES) membrane to minimize the issue of recoverability and nanoparticle agglomeration. The nanocomposite membranes were prepared by loading different quantities of Fe/Cu/Ag trimetallic nanoparticles onto the PMAA-g-PES membrane for optimization purposes. Characterization was performed using FTIR, NMR, XPS, SEM/EDS and AFM analyses. The PMAA g-PES and nanocomposite membranes were found to have a porous top layer and a rough surface. Moreover, the addition of nanoparticles did not cause any significant changes in the membrane structure, however, further addition of nano particles led to the blockage of pores. The performance of the synthesized membranes was tested using pure water flux and MO (anionic dye) and methylene blue (MB) (cationic dye) dye removal capacity. The negatively charged membranes were found to have more affinity for MB dye than the MO dye and this was ascribed to the charge interaction between the membrane surface and the dyes. The nanocomposite with 5% Fe/Cu/Ag trimetallic nanoparticle loading on PMAA-g-PES membrane (M4-5% membrane) was found to have the best adsorption capacity with about 60% MB dye removal efficiency. Furthermore, the effect of process parameters such as pH, temperature and H2O2 concentration on the removal of MB was studied. The removal efficiency was found to be higher at higher pH and lower temperature. About 100% removal efficiency was obtained when the process was performed at pH 9 in the presence of H2O2 via adsorption and Fenton degradation. This showed that a hybrid of processes was convenient for the removal of MB dye by adsorption (primarily) and degradation using the nanocomposite membrane. Adsorption equilibrium data were assessed using the Langmuir, Freundlich and Temkin models; the Temkin model was the most convenient to explain the adsorption of MB onto M4-5% membrane. Moreover, lcinetic studies were performed on four kinetic models: pseudo first-order, pseudo second order, intraparticle diffusion and elovich models. The pseudo second-order was found to be the best suitable to explain the adsorption of MB onto M4-5% membrane. Thus, the adsorption of MB onto the nanocomposite membrane is an exothermic chemical process that occurs on a heterogeneous surface. Therefore, the nanocomposite membrane has the prospective to be applied in the removal of cationic textile dyes in the presence of an oxidiser.
Water quality assessment at Vaalkop Dam in North-West Province using multispectral remote sensing data
(University of the Witwatersrand, Johannesburg, 2022) Mthimkulu, Lindy Ndzumbululo; Adam, Elhadi
Water is a life-sustaining resource for all organisms. As much as nature share the value of water with human being it cannot supersede how human have become dependent on water for drinking, sanitation, farming, mining, and other industrial purposes such as power generation. Water is perceived as a vital component in the fight against poverty, the foundation of any successfully growing and developed country is also measured on water and sanitation provision (Basson et al., 1997). The water law in South Africa stresses that essential human and ecological necessities must be given (DWAF, 1998) and that the misuse of water from all perspectives should be feasible (New, 2002).

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