Faculty of Engineering and Built Environment
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Item Simultaneously colliers and coal-fired wastewater treatment as well as energy production through reverse electrodialysis(2024-05) Ngobese, Thobeka; Ngema, Peterson Thokozani; Kaniki, Armel Tumba; Nkosi, NkululekoOne primary sector contributing to the country’s economic development is coal mining. As the country’s primary energy source, coal dominates the country’s energy mix. Conversely, the devastating environmental impact of this industry cannot be ignored. An ever-increasing population and economic growth exacerbate this problem further. This energy resource, “coal”, is mined using large quantities of water, resulting in salted wastewater and further contaminating groundwater. South Africa (SA) is experiencing water shortages because of climate change, which coal directly contributed to, so it has no choice but to implement mitigation plans instead of preventing it to ensure its sustainability. Therefore, it is in this context that led to the motive for this current research. This study uses reverse electrodialysis (RED) technology to mitigate and address this environmental challenge sustainably. A vital advantage of this technology is its ability to produce power while purifying wastewater. This advantage makes it a valuable energy mix that can substantially reduce and alleviate coal-fired emissions. The study aimed to investigate the desalination and power generation process for treating synthesised coal mining and colliers using a RED stack. The study’s hypothesis was tested by using small laboratory-scale RED stacks. This study used synthetic wastewater to mimic SA’s colliery mine and coal power plant wastewater. A performance assessment of the RED stacks was conducted under varying system temperatures, solution concentrations, and flow rates. 20 to 40 °C system temperatures, 1 to 2 mol/L solution concentrations, and 896 to 1550 mL/min flow rates were used. Within the specified experimental ranges, an empirical tool, response surface methodology (RSM), was used to minimise the number of experiments while obtaining sufficient experimental data. The selected process parameters were converted into dimensionless codified data in three levels. A general full factorial design type recommended 18 experimental runs. The influence of each selected parameter was examined individually in the first part of this study. A range of 2.31 to 10.75 W/m2 and 3.94 to 16.13 wt.% power density and salt removal were obtained at the selected experimental ranges. These results corresponded to a membrane flux range used in this study. The membrane flux data was used to assess scale-up feasibility and cost estimation for the RED technology Statistical analysis was performed using the historical data design (HDD) option provided by RSM software to examine the combined influence of the investigated parameters on power density and salt removal. The results recommended that the 2FI model, as the highest order with significant terms, can describe the desalination and power density. A good agreement was found between experimental data and data generated by empirical models, with a less than 3% deviation. A regression (R2) analysis was performed to determine the accuracy and reliability of the developed empirical models. An accuracy level of 95% was obtained in predicting experimental data within the experimental range for these models. Against this brief, the two factor interaction (2FI) acquired by the model elucidates that this model is not recommended since it cannot make accurate predictions, as 0.6949 as well as 0.8704 for salt removal percentage and power density, respectively, indicate a relatively low value for regression. The combined effects and significance of input parameters were assessed with a three-dimensional surface (3-D) and a contour plot. The assessment revealed that power density and salt removal were less affected by the increase in flow rate than by solution concentration and system temperature. The feasibility of the technology was further explored by optimising input variables since the membrane flux data alone cannot provide detailed information on the technology’s potential. Increasing RED parameters, such as pumping at higher flow rates, frequently requires more energy; therefore, pumping costs may increase if the operating parameters necessitate higher solution flow rates, affecting the RED system’s overall running costs. The temperature, concentration, and flow rate were optimal through RSM software at 40℃, 1.93 mol/L and 896 mL/min. This high temperature will accelerate scaling effects, leading to technical failure if the technology is used to treat or produce electricity on a large scale. Consequently, this technology would be more expensive. However, this does not exclude the possibility of replacing current conventional technologies with this technology. After RED technology has been conceptually designed and cost analysis, including sensitivity analysis, has been conducted, a realistic conclusion can be drawn. The effect of divalent ions was investigated in further detail using these optimal conditions. The synthetic coal mine wastewater was prepared by adding Ca2+ and SO4 2- , maintaining NaCl concentration and increasing divalent ions. Deionised water simulating lower concentrations likely affected the overall performance of the RED stack in this study. In this case, further investigation into the effect of lower concentrations should be recommended to examine improving the performance of RED stacks at even lower concentrations. It will also be possible to assess if they are effective on wastewater containing low salt levels. This study does not recommend the HDD method for optimising the experimental results. However, further investigation should be conducted to accurately develop models that would produce a reliable model with acceptable prediction ability. In this manner, similar experimental investigations can be conducted more quickly.Item Performance analyses of wastewater treatment plant : a case of Hazelmere water treatment plant(2023-09) Mkhize, Nonsindiso; Seyam, MohammedThere is still an existing gap in the assortment and treatment of domestic wastewater; where wastewater treatment plants exist, they frequently operate beneath a set of guidelines. This prompts the discharge of pollutants into natural water bodies, establishing an adverse consequence on the climate and on human wellbeing. The performance of wastewater treatment plants is a fundamental parameter to be observed and assessed. This allows for better comprehension of the plans and operating challenges in water treatment plants. The results from assessment evaluations might be used for strategic planning aimed at upgrading plant operations and promoting adjustment necessities for better plant output. In this study, the Hazelmere Wastewater Treatment System's performance was evaluated from 1999 to 2018. The study’s principal objective was to evaluate the exhibition of the treatment plant in terms of the expulsion of microbial and chemical contaminations. Secondary data from the plant’s data records were used in the analysis. The study was also aimed at developing a predictive model which can be used to estimate future trends and parameters. Since long-term forecasting may produce more variations and higher errors, the forecast is only made for the next three years. The analysis conducted by this study revealed that the Hazelmere wastewater treatment plant's performance met the predetermined criteria. The measured values of E. coli, turbidity, and iron were higher than the benchmark focus requirements established (recommended) by international standards. The expulsion of turbidity for the period under study all satisfied World Health Organization (WHO) and South African National Standards (SANS) for discharge [≤ 1 NTU]. Iron removal also satisfied the WHO/SANS standards for release at [≤2 mg/L]. From 1999 to 2018, the effluent produced by the wastewater treatment plant was pathogenfree, with a recorded annual average of 0MPN/100mL. As a result, E. coli removal efficiency was at 100% during the mentioned period. Given the cost of running the plant, it is crucial that enhancements are made to expand the plants performance. Potential enhancements must adhere to criteria such as low speculation and upkeep costs, an increase in the plant's water-driven limit, and being simple to work with and maintain. The findings revealed that the proposed stochastic model can accurately and consistently predict the concentrations of the plant's wastewater parameters. Hence, if consideration is given to the nature of the input factors of the model, stochastic demonstrating can be utilized to help support wastewater plants. This will lead to a reduction in the number of experiments performed to analyze the pollutants and thus minimizing plant operating costs.Item Wastewater treatment and photo-reduction of CO2 using an integrated magnetized TiO2 anaerobic- photocatalytic system(2022-09-29) Tetteh, Kweinor Emmanuel; Rathilal, SudeshConventionally, the treatment of municipal wastewater involves a sequence of treatment units aimed at reducing pollutants to acceptable discharge levels. Herein wastewater treatment plants in South Africa’s municipalities are being challenged recently due to emerging contaminants (nanomaterials, pesticides, antibiotics, COVID-19 RNA, etc.) that impede their efficiency. This calls for robust technological water solution systems targeted at promoting sustainable water supply and mitigating anthropogenic gas (CO2) emission via biogas production. Against this background, the novel of this study is aimed to develop an integrated AD-AOP (anaerobic digestion – advanced oxidation process) magnetized system to improve wastewater for reuse with biogas production and nanoparticles recoverability benefits. To obtain an optimal balance between robustness and cost-effectiveness of the integrated system, a series of feasibility and engineering works were explored. The first phase involved the synthesis via a co-precipitation technique, characterization, and applicability of the magnetized-photocatalysts (MPCs) for wastewater treatment. Analytically, the scanning electron microscopy and energy dispersive X-ray (SEM/EDX), Fourier transforms infrared spectra, X-ray diffraction (XRD), and Brunauer- Emmett-Teller (BET) techniques showed the tailored MPCs were successfully magnetized. Among the MPCs studied, Fe-TiO2 (with a BET surface area of 62.73 m2 /g) was found as the best with greater potential for above 75% decontamination of the wastewater and methane yield. In the technological design and evaluation, Fe-TiO2 was examined using biochemical methane potential (BMP), biophotocatalytic (BP), biomagnetic (BM), and biophotomagnetic (BPM) systems. Due to the external magnetic field influence on the BPMs, it was found very promising for future adventures. Above all, the novel integrated AD-AOP magnetized system proof of concept showed great potential for recoverability of the MPCs for reuse, reducing the toxicological effects of trace metals (27 elements considered), and improving water and biogas quality. The bioenergy economy of the integrated AD-AOP magnetized system demonstrated net energy being able to subsidize the energy required by the UV-lamp of the AOP system. Conclusively, this finding provides an insight into synthesizing novel MPCs and their applicability for wastewater remediation and biogas production. Also kinetics modeling and response surface methodology (RSM) optimization coupled with artificial neural network (ANN) predictability showed the potential to develop an optimized integrated AD-AOP magnetised system towards the treatment of industrial wastewater, biogas production , and CO2 emission reduction. The prospects necessitate a techno-scientific revolution to upscale the current integrated system into a pilot scale with smart-online monitoring towards improving the wastewater circular economy.Item Bioremediation of acid mine drainage and crude contaminated soils(2020-09) Anekwe, Ifeanyi Michael; Isa, Yusuf MakarfiPollution is one of the greatest ills plaguing the existence of the ecosystem which could lead to the annihilation of terrestrial and aquatic habitat if not remedied. Acid mine drainage (AMD) and crude oil are among the major land and water pollutants cause by industrial and human activities. The constant exploration, mining, and processing of mineral resources and prevalent use of petroleum products for economic purposes have contributed to contamination of soil and proximate water bodies which results in environmental degradation; thus, remediation becomes necessary. The treatment of AMD contaminated soils using the conventional methods has some room for improvement to meet the remediation purpose. Bioremediation technology provides a sustainable and eco-friendly approach to the treatment of contaminants. This study aims to evaluate the performance of different potential bioremediation techniques and conduct a comparative analysis of these methods for the treatment of AMD and crude oil-contaminated soils. The treatment approach for both pollutants comprises of soils separately contaminated with AMD and crude oil before the application of bioremediation techniques. For the biostimulation study, contaminated soils were amended with varying ratios of the brewery or municipal wastewaters (BWW and MWW), while the bioventing (BVT) treatment involved wastewater amendment and supply of atmospheric air from the vadose zone at 3L/min at 30 minutes intervals every 48 hours. The bacteria strain Pseudomonas aeruginosa ATCC 15442 used for the study which was inoculated at 5%(w/w) was cultured in two different media for respective treatments and wastewater was amended as an extra energy source for bioaugmentation (BAU) study while Bioattenuation (BAT) which received no amendment was used as a control treatment for the study. The treatments were conducted in plastic bioreactors under mesophilic conditions for 28 days and samples were collected from each treatment system on weekly basis to analyse for sulfate, heavy metals, and total petroleum hydrocarbon (TPH) reduction. The result of the study showed that the amendment of contaminated soils with wastewater increased alkalinity in the system which enhanced microbial activities for effective remediation which recorded 52.43 and 51.23% average TPH and metal removal efficiency for the BSTc treatment. Also, the combined application of bioremediation techniques was more effective than single application as the introduction of oxygen into the treatment system with wastewater amendment increased the TPH and metal removal efficiency by an average of 12.98 and 13.17% respectively but efforts to enhance sulfate removal by air-injection (BVTa) proved abortive with 17.20 and 14.67% removal efficiencies less than BSTa and BAUa respectively as sulfate-reducing bacteria thrive in an anaerobic environment. However, P. aeruginosa ATCC 15442 adopts the sorption process in the reduction of hydrocarbon and metal toxicity with 42.02 and 41.81% average removal efficiencies respectively and the amendment extra nutrient (wastewater) increased the removal efficiency of these pollutants by 25.24 and 16.23% respectively. The results of the study inferred that wastewater (BWW and MWW), air-injection and P. aeruginosa ATCC 15442 showed great potentials in the degradation and removal of TPH, metals and sulfate contaminants, hence, can serve as a viable strategy for the remediation of AMD and crude oil polluted soils while improving waste management and amelioration of pollution aftermath faced by communities involved in mining and oil production and/or processing. There is a need for optimization to ensure effective remediation while further study is required to validate large scale application.Item Prospects of synthesized magnetic TiO2-based membranes for wastewater treatment : a review(MDPI AG, 2021-06) Tetteh, E. Kweinor; Rathilal, S.; Asante-Sackey, D.; Chollom, Martha NoroGlobal accessibility to clean water has stressed the need to develop advanced technologies for the removal of toxic organic and inorganic pollutants and pathogens from wastewater to meet stringent discharge water quality limits. Conventionally, the high separation efficiencies, relative low costs, small footprint, and ease of operation associated with integrated photocatalytic-membrane (IPM) technologies are gaining an all-inclusive attention. Conversely, photocatalysis and membrane technologies face some degree of setbacks, which limit their worldwide application in wastewater settings for the treatment of emerging contaminants. Therefore, this review elucidated titanium dioxide (TiO2), based on its unique properties (low cost, non-toxicity, biocompatibility, and high chemical stability), to have great potential in engineering photocatalytic-based membranes for reclamation of wastewater for re-use. The environmental pathway of TiO2 nanoparticles, membranes and configuration types, modification process, characteristics, and applications of IPMs in water settings are discussed. Future research and prospects of magnetized TiO2-based membrane technology is highlighted as a viable water purification technology to mitigate fouling in the membrane process and photocatalyst recoverability. In addition, exploring life cycle assessment research would also aid in utilizing the concept and pressing for large-scale application of this technology.