Evaluation of water quality, selected metals and endocrine-disrupting compounds in the rivers and municipal wastewaters of Eastern Cape province, South Africa
- Authors: Farounbi, Adebayo Ibikunle
- Date: 2021-04
- Subjects: To be added
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/177327 , vital:42810 , DOI 10.21504/10962/177327
- Description: South Africa is developing with increasing population, and so is the demand for use and access to water resources. Surface water is critical to the country because it provides about 77% of the needed water resources. Low rainfall (about 450 mm annually) with little runoffs to boost the rivers aggravates the problems of surface waters. Expansion of industrial and agricultural activities coupled with the population pressure had an impact on water quality, availability and the state of aquatic ecosystems in the country. Water management is a challenge in South Africa because of the socio-economic pressure and other factors such as mine wastewater, eutrophication, salinisation, and emerging contaminants. This research investigated some water quality parameters of Bloukrans, Buffalo, Swartkops and Tyhume Rivers in Eastern Cape Province of South Africa for three seasons. The parameters investigated include the physicochemical properties, functional groups of organic compounds, presence of endocrine-disrupting compounds and heavy metals in the rivers and wastewater effluents from wastewater treatment plants (WWTPs) released into these rivers. The aims were to determine the concentrations of these parameters in the rivers and wastewater effluents, compare the concentration levels with recommended values for aquatic lives, domestic and agricultural purposes, thereby contributing to the effective management of water in South Africa. Water samples were collected for analyses at upstream, midstream and downstream reaches of the rivers. In contrast, wastewater influent and effluent samples were obtained from wastewater treatment plants releasing effluents to the rivers. Some physicochemical parameters were studied onsite with specialised meters while others analysed in the laboratory with ultraviolet (UV) spectroscopy. Chemical functional groups in the samples were determined with Fourier-transformed infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopies. The Endocrine-disrupting compounds and heavy metals were determined with liquid chromatography coupled to a mass spectrometer (LC-MS/MS) and inductively coupled plasma with a mass spectrometer (ICP-MS) respectively. Method validation and calibration for all the spectrometry yielded good linearity (r2 > 0.99). The results showed high oxygen demand above the concentration recommended by the South Africa Department of water affairs and forestry (DWAF) for Alice and Uitenhage wastewater effluents, midstream and downstream river samples. Phosphate concentrations were higher than the recommended level in wastewater effluents. Sulphate concentration in the Bloukrans River was higher than the recommended value. The pH values of rivers at midstream and downstream reaches were higher than 8.0 except in Bloukrans River, where it was around 7.0. The functional group analyses show the presence of substituted aromatic compounds, alkyl halides, chlorobenzenes, vinylidenes, amides, amines, urethanes, cycloalkanes, acetonitriles, methenamine, imidazole and phenolic compounds among others, in the samples. The presence of these functional groups in the water samples is an indication of pollution by volatile organic compounds, persistent organic pollutants and pharmaceuticals. Results of LC-MS/MS analysis show that endocrine-disrupting compounds (EDCs) were present in the rivers and wastewaters samples. Descriptive statistics showed the mean concentrations of the EDCs in the samples as nonylphenol > dichlorophenol > bisphenol A > triclosan > octylphenol > imidazole > atrazine > triazole > estrone > estradiol. The results of the heavy metal analysis show that chromium had the highest mean concentration in the samples. The mean metals concentrations in the samples were in the order of Cr > Ni > Mn > Cu > As > Pb > Cd > Hg > Zn. The results showed an increase in the concentrations of metals in the rivers over the years. The chromium, manganese, nickel, copper, zinc, arsenic, cadmium, lead and mercury concentrations in the lower reaches of the rivers and wastewater effluents were higher than the values recommended by the United Nations Environmental Programme (UNEP) and DWAF. Improvement is necessary in wastewater treatment and adequate legislation on chemical usage. Some chemicals banned in developed countries, such as atrazine, were encountered in this study. , Thesis (PhD) -- Faculty of Science, Institute of Water Research, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Farounbi, Adebayo Ibikunle
- Date: 2021-04
- Subjects: To be added
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/177327 , vital:42810 , DOI 10.21504/10962/177327
- Description: South Africa is developing with increasing population, and so is the demand for use and access to water resources. Surface water is critical to the country because it provides about 77% of the needed water resources. Low rainfall (about 450 mm annually) with little runoffs to boost the rivers aggravates the problems of surface waters. Expansion of industrial and agricultural activities coupled with the population pressure had an impact on water quality, availability and the state of aquatic ecosystems in the country. Water management is a challenge in South Africa because of the socio-economic pressure and other factors such as mine wastewater, eutrophication, salinisation, and emerging contaminants. This research investigated some water quality parameters of Bloukrans, Buffalo, Swartkops and Tyhume Rivers in Eastern Cape Province of South Africa for three seasons. The parameters investigated include the physicochemical properties, functional groups of organic compounds, presence of endocrine-disrupting compounds and heavy metals in the rivers and wastewater effluents from wastewater treatment plants (WWTPs) released into these rivers. The aims were to determine the concentrations of these parameters in the rivers and wastewater effluents, compare the concentration levels with recommended values for aquatic lives, domestic and agricultural purposes, thereby contributing to the effective management of water in South Africa. Water samples were collected for analyses at upstream, midstream and downstream reaches of the rivers. In contrast, wastewater influent and effluent samples were obtained from wastewater treatment plants releasing effluents to the rivers. Some physicochemical parameters were studied onsite with specialised meters while others analysed in the laboratory with ultraviolet (UV) spectroscopy. Chemical functional groups in the samples were determined with Fourier-transformed infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopies. The Endocrine-disrupting compounds and heavy metals were determined with liquid chromatography coupled to a mass spectrometer (LC-MS/MS) and inductively coupled plasma with a mass spectrometer (ICP-MS) respectively. Method validation and calibration for all the spectrometry yielded good linearity (r2 > 0.99). The results showed high oxygen demand above the concentration recommended by the South Africa Department of water affairs and forestry (DWAF) for Alice and Uitenhage wastewater effluents, midstream and downstream river samples. Phosphate concentrations were higher than the recommended level in wastewater effluents. Sulphate concentration in the Bloukrans River was higher than the recommended value. The pH values of rivers at midstream and downstream reaches were higher than 8.0 except in Bloukrans River, where it was around 7.0. The functional group analyses show the presence of substituted aromatic compounds, alkyl halides, chlorobenzenes, vinylidenes, amides, amines, urethanes, cycloalkanes, acetonitriles, methenamine, imidazole and phenolic compounds among others, in the samples. The presence of these functional groups in the water samples is an indication of pollution by volatile organic compounds, persistent organic pollutants and pharmaceuticals. Results of LC-MS/MS analysis show that endocrine-disrupting compounds (EDCs) were present in the rivers and wastewaters samples. Descriptive statistics showed the mean concentrations of the EDCs in the samples as nonylphenol > dichlorophenol > bisphenol A > triclosan > octylphenol > imidazole > atrazine > triazole > estrone > estradiol. The results of the heavy metal analysis show that chromium had the highest mean concentration in the samples. The mean metals concentrations in the samples were in the order of Cr > Ni > Mn > Cu > As > Pb > Cd > Hg > Zn. The results showed an increase in the concentrations of metals in the rivers over the years. The chromium, manganese, nickel, copper, zinc, arsenic, cadmium, lead and mercury concentrations in the lower reaches of the rivers and wastewater effluents were higher than the values recommended by the United Nations Environmental Programme (UNEP) and DWAF. Improvement is necessary in wastewater treatment and adequate legislation on chemical usage. Some chemicals banned in developed countries, such as atrazine, were encountered in this study. , Thesis (PhD) -- Faculty of Science, Institute of Water Research, 2021
- Full Text:
- Date Issued: 2021-04
The effect of various substrate pretreatment methods on the enzymatic degradability of a Eucalyptus sp. – a potential feedstock for producing fermentable sugars
- Authors: Thoresen, Mariska
- Date: 2021-04
- Subjects: Cellulose , Cellulase , Enzymes , Hydrolysis , Eucalyptus , Biomass energy
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/178580 , vital:42952 , DOI 10.21504/10962/178580
- Description: Over the past few years, there has been a global urgency to make the transition from conventional fossil fuels to renewable energy in order to meet the world’s increasing energy demands. Lignocellulosic biomass is currently at the forefront of intensive biofuel research due to its renewable nature. Lignocellulose valorisation into value added products such as bio-ethanol is a multistep process. The first step requires the biomass to go through a recalcitrance-reducing step (pretreatment), after which, enzymatic hydrolysis is required to break down the polysaccharides into simple sugars for fermentation. However, the recalcitrant structure of biomass and the low hydrolytic activities of the enzymes (glycoside hydrolases) on the substrate pose major technical and economic obstacles to the biomass conversion process. Since this process remains more expensive compared to petroleum-based fuels, lignocellulose has been intensively investigated in terms of its cost efficiency and effective decomposition. Although improvements to this process are ongoing, with some of the first commercial facilities producing cellulosic ethanol in 2013 and 2014, there is still a deep sense of urgency to render the facilities more economically feasible. Some important factors that determine the yield and rate of enzymatic hydrolysis include the type of enzymes used, enzyme recognition with the substrate, substrate composition and crystallinity. In this context, the major focus of this study was to develop a deeper understanding of how enzymes co-operate (synergise) at a molecular level using model substrates. This knowledge was then used as a basis for understanding how these enzymes synergise on more natural, complex substrates. This study specifically focused on how different pretreatments affect the chemical and structural properties of Eucalyptus. Lastly, we wanted to develop an effective method of enzyme recycling as a means to reduce the high process costs in biomass saccharification. Enhancing cellulose hydrolysis through enzyme synergy is essential for achieving higher hydrolysis rates, and numerous research efforts have focused on trying to elucidate the enzyme mechanisms required to design optimal enzyme cocktails. Despite the extensive amount of research carried out over the past few years, little is known about the enzymatic machinery underpinning the synergistic interactions between bacterial and fungal cellulases - neither is it understood why only a limited number of Cellobiohydrolases (CBHs) and Endoglucanases (EGs) exhibit synergism. Therefore, the first part of the study evaluated and compared the synergistic relationships between cellulases from different GH families and microbial sources (cross-synergism), i.e. cellobiohydrolase I (CBHI) from Hypocrea jecorina (Cel7A), CBHI from Trichoderma longibrachiatum (Cel7A), CBHI from Clostridium stercorarium (Cel48A), CBHII from a microbial source, CBHII from Clostridium thermocellum (Cel5A), endoglucanases (EG) from Bacillus amyloliquefaciens (Cel5A), EG from Thermotaga maritima (Cel5A), EG from Trichoderma reesei and a β-glucosidase from Aspergillus niger (Novozyme 188). An aim of this study was to provide insights into how the molecular mechanisms of different GH families govern synergism. The results showed that cellulases from different GH families and microbial sources exhibit different substrate specificities, which influence their synergistic interactions with other enzymes. Based on these observations, this study agreed with evidence that not all endo- and exo-cellulase interactions are synergistic, and that the extent of synergism is dependent on the composition of the cellulase systems from various sources and their compatibility in the cellulase cocktail. From the enzymes assessed in this study, an optimal enzyme cocktail (CelMix) was formulated which was composed of Egl 68%, Cel7A 17%, Cel6A 6%, βgl 9%. This method of screening for maximal compatibility between exo- and endo-cellulases from different GH families constituted a critical step towards a better understanding of the specific interactions between the enzymes of interest and how they synergise at the molecular level. Consequently, this information may assist in the design of improved synergistic cellulose-degrading cocktails for industrial-scale biomass degradation. The enzyme synergy studies provided a basis for the second part of this study, where it was assessed how these optimised enzyme cocktails would perform on complex substrates. It is well-known that lignocellulosic substrates are highly recalcitrant to microbial degradation, and although extensive research has been performed to understand biomass recalcitrance, the key features of biomass which hinder enzymatic hydrolysis are yet to be elucidated. In this study, we explored the effect of eight (8) different pretreatment methods on the enzymatic hydrolysis of a Eucalyptus sp. – a potential feedstock for biofuel production. This study was performed to increase our understanding of the relationship between biomass architecture and hydrolysis yield potential. Our results demonstrated that pretreatments induce changes at a micro- and macro-level in the cell walls of Eucalyptus, and that cellulose accessibility, cellulose crystallinity and the changes in the lignin S/G ratio played an important role in the enzymatic activity on the biomass. Thus, this study provided insight into important cellulose structural features related to biomass recalcitrance arising from various pretreatment methods, which may ultimately be used for the development of more efficient conversion technologies for better, more competitive bio-refineries. Lastly, a simple and yet effective method for desorbing the adsorbed cellulases on lignocellulosic substrates was established for better understanding cellulase adsorption and desorption in order to develop an effective enzyme recycling strategy. Various reagents were assessed to determine how effective they were in promoting enzyme desorption. Tris-HCl buffer (pH 9.0; 0.05 M) was the most effective method for promoting enzyme desorption and retained a substantial amount of hydrolytic activity after elution. However, minor activity loss was observed due to irreversible binding, which was further confirmed by SDS-PAGE analysis. With this information available, the feasibility of recovering the enzymes from the solid fraction after enzymatic hydrolysis of steam pretreated Eucalyptus was evaluated by two different approaches, i.e.: i) re-adsorption of the entire hydrolysed insoluble biomass fraction (no desorption) to fresh biomass (recycling approach 1 - RA1) and ii) re-adsorption of alkaline elution desorbed enzymes from hydrolysed biomass to fresh biomass (recycling approach 2 - RA2). The recycling performance of RA1 and RA2 achieved > 95% of the initial sugar liberation for three continuous rounds, whilst successfully reducing enzyme loadings by 50% and 40% for RA1 and RA2, respectively. This study presented a simple and effective pathway for improving the economic feasibility of fermentable sugar production for biofuels. In conclusion, this study has contributed to expanding our knowledge and providing new insights into factors relating to the biomass conversion process, including enzyme synergism, pretreatment methods and enzyme recycling strategies. Ultimately, the knowledge and information gained from this study can be used as a platform for the development of more efficient conversion technologies for better, more competitive bio-refineries. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Thoresen, Mariska
- Date: 2021-04
- Subjects: Cellulose , Cellulase , Enzymes , Hydrolysis , Eucalyptus , Biomass energy
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/178580 , vital:42952 , DOI 10.21504/10962/178580
- Description: Over the past few years, there has been a global urgency to make the transition from conventional fossil fuels to renewable energy in order to meet the world’s increasing energy demands. Lignocellulosic biomass is currently at the forefront of intensive biofuel research due to its renewable nature. Lignocellulose valorisation into value added products such as bio-ethanol is a multistep process. The first step requires the biomass to go through a recalcitrance-reducing step (pretreatment), after which, enzymatic hydrolysis is required to break down the polysaccharides into simple sugars for fermentation. However, the recalcitrant structure of biomass and the low hydrolytic activities of the enzymes (glycoside hydrolases) on the substrate pose major technical and economic obstacles to the biomass conversion process. Since this process remains more expensive compared to petroleum-based fuels, lignocellulose has been intensively investigated in terms of its cost efficiency and effective decomposition. Although improvements to this process are ongoing, with some of the first commercial facilities producing cellulosic ethanol in 2013 and 2014, there is still a deep sense of urgency to render the facilities more economically feasible. Some important factors that determine the yield and rate of enzymatic hydrolysis include the type of enzymes used, enzyme recognition with the substrate, substrate composition and crystallinity. In this context, the major focus of this study was to develop a deeper understanding of how enzymes co-operate (synergise) at a molecular level using model substrates. This knowledge was then used as a basis for understanding how these enzymes synergise on more natural, complex substrates. This study specifically focused on how different pretreatments affect the chemical and structural properties of Eucalyptus. Lastly, we wanted to develop an effective method of enzyme recycling as a means to reduce the high process costs in biomass saccharification. Enhancing cellulose hydrolysis through enzyme synergy is essential for achieving higher hydrolysis rates, and numerous research efforts have focused on trying to elucidate the enzyme mechanisms required to design optimal enzyme cocktails. Despite the extensive amount of research carried out over the past few years, little is known about the enzymatic machinery underpinning the synergistic interactions between bacterial and fungal cellulases - neither is it understood why only a limited number of Cellobiohydrolases (CBHs) and Endoglucanases (EGs) exhibit synergism. Therefore, the first part of the study evaluated and compared the synergistic relationships between cellulases from different GH families and microbial sources (cross-synergism), i.e. cellobiohydrolase I (CBHI) from Hypocrea jecorina (Cel7A), CBHI from Trichoderma longibrachiatum (Cel7A), CBHI from Clostridium stercorarium (Cel48A), CBHII from a microbial source, CBHII from Clostridium thermocellum (Cel5A), endoglucanases (EG) from Bacillus amyloliquefaciens (Cel5A), EG from Thermotaga maritima (Cel5A), EG from Trichoderma reesei and a β-glucosidase from Aspergillus niger (Novozyme 188). An aim of this study was to provide insights into how the molecular mechanisms of different GH families govern synergism. The results showed that cellulases from different GH families and microbial sources exhibit different substrate specificities, which influence their synergistic interactions with other enzymes. Based on these observations, this study agreed with evidence that not all endo- and exo-cellulase interactions are synergistic, and that the extent of synergism is dependent on the composition of the cellulase systems from various sources and their compatibility in the cellulase cocktail. From the enzymes assessed in this study, an optimal enzyme cocktail (CelMix) was formulated which was composed of Egl 68%, Cel7A 17%, Cel6A 6%, βgl 9%. This method of screening for maximal compatibility between exo- and endo-cellulases from different GH families constituted a critical step towards a better understanding of the specific interactions between the enzymes of interest and how they synergise at the molecular level. Consequently, this information may assist in the design of improved synergistic cellulose-degrading cocktails for industrial-scale biomass degradation. The enzyme synergy studies provided a basis for the second part of this study, where it was assessed how these optimised enzyme cocktails would perform on complex substrates. It is well-known that lignocellulosic substrates are highly recalcitrant to microbial degradation, and although extensive research has been performed to understand biomass recalcitrance, the key features of biomass which hinder enzymatic hydrolysis are yet to be elucidated. In this study, we explored the effect of eight (8) different pretreatment methods on the enzymatic hydrolysis of a Eucalyptus sp. – a potential feedstock for biofuel production. This study was performed to increase our understanding of the relationship between biomass architecture and hydrolysis yield potential. Our results demonstrated that pretreatments induce changes at a micro- and macro-level in the cell walls of Eucalyptus, and that cellulose accessibility, cellulose crystallinity and the changes in the lignin S/G ratio played an important role in the enzymatic activity on the biomass. Thus, this study provided insight into important cellulose structural features related to biomass recalcitrance arising from various pretreatment methods, which may ultimately be used for the development of more efficient conversion technologies for better, more competitive bio-refineries. Lastly, a simple and yet effective method for desorbing the adsorbed cellulases on lignocellulosic substrates was established for better understanding cellulase adsorption and desorption in order to develop an effective enzyme recycling strategy. Various reagents were assessed to determine how effective they were in promoting enzyme desorption. Tris-HCl buffer (pH 9.0; 0.05 M) was the most effective method for promoting enzyme desorption and retained a substantial amount of hydrolytic activity after elution. However, minor activity loss was observed due to irreversible binding, which was further confirmed by SDS-PAGE analysis. With this information available, the feasibility of recovering the enzymes from the solid fraction after enzymatic hydrolysis of steam pretreated Eucalyptus was evaluated by two different approaches, i.e.: i) re-adsorption of the entire hydrolysed insoluble biomass fraction (no desorption) to fresh biomass (recycling approach 1 - RA1) and ii) re-adsorption of alkaline elution desorbed enzymes from hydrolysed biomass to fresh biomass (recycling approach 2 - RA2). The recycling performance of RA1 and RA2 achieved > 95% of the initial sugar liberation for three continuous rounds, whilst successfully reducing enzyme loadings by 50% and 40% for RA1 and RA2, respectively. This study presented a simple and effective pathway for improving the economic feasibility of fermentable sugar production for biofuels. In conclusion, this study has contributed to expanding our knowledge and providing new insights into factors relating to the biomass conversion process, including enzyme synergism, pretreatment methods and enzyme recycling strategies. Ultimately, the knowledge and information gained from this study can be used as a platform for the development of more efficient conversion technologies for better, more competitive bio-refineries. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2021
- Full Text:
- Date Issued: 2021-04
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