Preparation and Investigation of coumarin-based chemosensors towards sensing of ions using UV studies in aqueous systems
- Authors: Kotze, Tyla
- Date: 2024-04
- Subjects: Chemistry, Analytic , Water chemistry , Ionic solutions , Aquatic ecology , Geochemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64116 , vital:73654
- Description: Humanity's unrelenting expansion has shown little regard for the environment, and this has resulted in tons of toxic heavy metal cations and anions being released into the environment through industrial, agricultural, electronic, and mining dumping. The release of these toxic heavy metals can cause diseases and sometimes lead to death, especially in third-world countries with low-income that reside in informal settlements, who suffer the most. Furthermore, the release of these toxins eventually finds their way back into the environment through bioaccumulation in fish, plants and animals. Although there is an ever need for the growth of these industries; low-cost, sensitive, selective, and organic-based sensors is a positive step forward in highlighting the need for environmental restoration and remediation, whilst striving to avoid unnecessary disease and death through this development. In this project, coumarin-based chemosensors for the detection of cationic and anionic species in aqueous and organic media are described. This project involves the synthesis of six different coumarin-based ether derivatives (E2-E5) and coumarin-based ester derivatives (H1-H2). FT-IR, 1H NMR and 13C NMR were used to confirm the structures of all sensors. The abilities of these novel compounds as chemosensors for detection of cations and anions were investigated using UV-vis analysis. These compounds displayed a favourable interaction with Fe2+ and Fe3+ ions with an increase in absorbance. Ether derivatives E2-E5 did not display any degree of selectivity or sensitivity towards the chosen anions. It was found that in the presence of FeCl2, sensors H1 and H2 displayed a degree of selectivities and further investigations were therefore carried out. From the titration experiments, the limit of detection, limit of quantification and association constants were determined. Job’s plot analyses were performed to determine the binding ratios, which was supported by Benesi-Hildebrand studies. The binding ratio between the sensors and metal cations during complexation was found to be 1:1. Reversibility studies were carried out using EDTA to determine whether the sensors could be reused. Molecular Modelling studies were used to determine the most preferred binding sites. Lastly, real-life application screenings were also run to determine if the sensors will be able to be used in real-life scenarios. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Kotze, Tyla
- Date: 2024-04
- Subjects: Chemistry, Analytic , Water chemistry , Ionic solutions , Aquatic ecology , Geochemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64116 , vital:73654
- Description: Humanity's unrelenting expansion has shown little regard for the environment, and this has resulted in tons of toxic heavy metal cations and anions being released into the environment through industrial, agricultural, electronic, and mining dumping. The release of these toxic heavy metals can cause diseases and sometimes lead to death, especially in third-world countries with low-income that reside in informal settlements, who suffer the most. Furthermore, the release of these toxins eventually finds their way back into the environment through bioaccumulation in fish, plants and animals. Although there is an ever need for the growth of these industries; low-cost, sensitive, selective, and organic-based sensors is a positive step forward in highlighting the need for environmental restoration and remediation, whilst striving to avoid unnecessary disease and death through this development. In this project, coumarin-based chemosensors for the detection of cationic and anionic species in aqueous and organic media are described. This project involves the synthesis of six different coumarin-based ether derivatives (E2-E5) and coumarin-based ester derivatives (H1-H2). FT-IR, 1H NMR and 13C NMR were used to confirm the structures of all sensors. The abilities of these novel compounds as chemosensors for detection of cations and anions were investigated using UV-vis analysis. These compounds displayed a favourable interaction with Fe2+ and Fe3+ ions with an increase in absorbance. Ether derivatives E2-E5 did not display any degree of selectivity or sensitivity towards the chosen anions. It was found that in the presence of FeCl2, sensors H1 and H2 displayed a degree of selectivities and further investigations were therefore carried out. From the titration experiments, the limit of detection, limit of quantification and association constants were determined. Job’s plot analyses were performed to determine the binding ratios, which was supported by Benesi-Hildebrand studies. The binding ratio between the sensors and metal cations during complexation was found to be 1:1. Reversibility studies were carried out using EDTA to determine whether the sensors could be reused. Molecular Modelling studies were used to determine the most preferred binding sites. Lastly, real-life application screenings were also run to determine if the sensors will be able to be used in real-life scenarios. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
Biological longitudinal aspects of the Kabompo River, a significant tributary of the upper Zambezi sub-catchment, North-west Province, Zambia
- Janse van Rensburg, Lomarie Cathleen
- Authors: Janse van Rensburg, Lomarie Cathleen
- Date: 2023-03-29
- Subjects: Nutrient cycles , Stable isotopes , Redeye Labeo , Synodontis , Zambezi River Watershed Ecology , Aquatic ecology
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/422292 , vital:71928
- Description: The landscape of the Upper Zambezi Catchment in the remote North-Western Province of Zambia retains many natural features, but current and future anthropogenic activities threaten its integrity. Lack of information relating to the basic ecological functioning of the region hampers conservation efforts. Flooding from the adjacent woody-savanna and open grasslands in the Upper-Zambezi Catchment in the wet season drives crucial processes in the aquatic ecosystems such as the Kabompo River. This thesis describes aquatic food webs and describes the nutrient cycling in this river. A general introduction was based on the seasonality, river morphology, and biodiversity of the Kabompo River. There is no aquatic food web information available on this river. To address this knowledge gap, sampling of the principal food web components– vegetation, invertebrates, and fish – were collected in the dry season from August to September 2019 across six sites in the Kabompo River. Stable isotope analyses provided proxies for the food web structure at each site, and were the basis of longitudinal comparisons. The analyses suggest that the Kabompo River food webs follow the trophic ordination and nutrient cycling characteristic of the revised-Riverine Productivity Model. Food webs and community assemblages remain structurally similar between sites and provide some evidence of bottom-up productivity-driven trophic dynamics. To predict the possible landscape-scale processing of nutrient changes present for the aquatic ecosystems of the Kabompo River, a longitudinal comparison between a herbivore, Labeo cylindricus, and omnivore, Synodontis spp., fish species and their resources (primary producers and invertebrates) was done and showed archetypal fish food web trophic separation (2 ‰ to3 ‰) between species which remains consistent for the headwater sites. The nutrient values change at the convergence between the Kabompo Bridge and the Mwinilunga branches and show a decrease in the trophic separation of the sites below. This change becomes apparent from the last site, Watopa, where the trophic separation re-establishes (2 ‰ to 3 ‰) between the species. The trend suggests primarily autochthonous production in the headwater reaches, changing to allochthonous and autochthonous nutrient incorporation after the convergence of the two main branches. Permanent wetlands surrounding the convergence zones may be conducive to more primary producer activity and increased nutrient turnover. Permanent wetlands are a common feature of the Upper Zambezi Catchment tributaries, with the most notable lentic system the Barotse Flood Plains in the south, which shares reach-adjacent characteristics with the Kabompo River. Trends from the 2015 dry season identified for the Barotse Flood Plains support the findings of this thesis, where the δ13C values recorded reach depletion of -45 ‰. Management in the Upper Zambezi Basin and the Kabompo River comprises biannual assessments of water quality and quantity by the Zambezi River Authority, but not of the ecosystem process. This thesis may provide information to address the ecological (food webs and nutrient cycling) dynamics of the Basin rivers. As the first baseline information on the river's biology and ecology, it may present a comparative basis for future assessments under conservation management strategies. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
- Full Text:
- Date Issued: 2023-03-29
- Authors: Janse van Rensburg, Lomarie Cathleen
- Date: 2023-03-29
- Subjects: Nutrient cycles , Stable isotopes , Redeye Labeo , Synodontis , Zambezi River Watershed Ecology , Aquatic ecology
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/422292 , vital:71928
- Description: The landscape of the Upper Zambezi Catchment in the remote North-Western Province of Zambia retains many natural features, but current and future anthropogenic activities threaten its integrity. Lack of information relating to the basic ecological functioning of the region hampers conservation efforts. Flooding from the adjacent woody-savanna and open grasslands in the Upper-Zambezi Catchment in the wet season drives crucial processes in the aquatic ecosystems such as the Kabompo River. This thesis describes aquatic food webs and describes the nutrient cycling in this river. A general introduction was based on the seasonality, river morphology, and biodiversity of the Kabompo River. There is no aquatic food web information available on this river. To address this knowledge gap, sampling of the principal food web components– vegetation, invertebrates, and fish – were collected in the dry season from August to September 2019 across six sites in the Kabompo River. Stable isotope analyses provided proxies for the food web structure at each site, and were the basis of longitudinal comparisons. The analyses suggest that the Kabompo River food webs follow the trophic ordination and nutrient cycling characteristic of the revised-Riverine Productivity Model. Food webs and community assemblages remain structurally similar between sites and provide some evidence of bottom-up productivity-driven trophic dynamics. To predict the possible landscape-scale processing of nutrient changes present for the aquatic ecosystems of the Kabompo River, a longitudinal comparison between a herbivore, Labeo cylindricus, and omnivore, Synodontis spp., fish species and their resources (primary producers and invertebrates) was done and showed archetypal fish food web trophic separation (2 ‰ to3 ‰) between species which remains consistent for the headwater sites. The nutrient values change at the convergence between the Kabompo Bridge and the Mwinilunga branches and show a decrease in the trophic separation of the sites below. This change becomes apparent from the last site, Watopa, where the trophic separation re-establishes (2 ‰ to 3 ‰) between the species. The trend suggests primarily autochthonous production in the headwater reaches, changing to allochthonous and autochthonous nutrient incorporation after the convergence of the two main branches. Permanent wetlands surrounding the convergence zones may be conducive to more primary producer activity and increased nutrient turnover. Permanent wetlands are a common feature of the Upper Zambezi Catchment tributaries, with the most notable lentic system the Barotse Flood Plains in the south, which shares reach-adjacent characteristics with the Kabompo River. Trends from the 2015 dry season identified for the Barotse Flood Plains support the findings of this thesis, where the δ13C values recorded reach depletion of -45 ‰. Management in the Upper Zambezi Basin and the Kabompo River comprises biannual assessments of water quality and quantity by the Zambezi River Authority, but not of the ecosystem process. This thesis may provide information to address the ecological (food webs and nutrient cycling) dynamics of the Basin rivers. As the first baseline information on the river's biology and ecology, it may present a comparative basis for future assessments under conservation management strategies. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
- Full Text:
- Date Issued: 2023-03-29
Understanding the relationship between mangrove composition, stand dynamics and resource use in the Ntafufu estuary, Eastern Cape, as basis for sustainable resource use
- Mvakade, Monica, Rajkaran, Anusha
- Authors: Mvakade, Monica , Rajkaran, Anusha
- Date: 2020
- Subjects: Estuarine ecology -- South Africa -- Eastern Cape , Aquatic ecology , Marine sciences , Fresh water
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49215 , vital:41611
- Description: Traditionally, coastal communities along the Wild Coast in the Eastern Cape, used mangrove forests for their livelihoods and socio-economic needs. Mangroves along the Eastern Cape coast are threatened by both natural and human factors. The wood obtained from the mangroves by rural households was used as poles for house and fence construction, firewood, and traditional medicine. This is a threat to the status of several mangrove species in this and surrounding areas. The harvesting of mangrove trees will have a direct and indirect effect on the other biotic and abiotic components of the mangrove ecosystems. The Department of Agriculture, Forestry and Fisheries (DAFF) (currently the Department of Environment, Forestry and Fisheries, or DEFF), through the National Forest Act no 84 of 1998, was directly responsible for the wellbeing of the national forests in South Africa. This also includes the mangroves as a specific national forest type. Several estuaries with mangroves occur within state forests. The harvesting and clear-felling of trees for timber and land conversion and associated waste of harvested mangrove poles and laths causes the many changes in mangrove forests. The aim of this study was to develop a framework for sustainable management of the mangroves for the Mtambalala forest management unit. This was done in relation to the requirements of the current legislation, policy guidelines and business plan of the management authority. The aim was pursued through two specific objectives. The first objective was to understand the variation in the composition in different parts of the Ntafufu Estuary, and the population dynamics of the main mangrove species, as basis for the development of sustainable resource use practices. Plots along transects were used to measure seedling to adult ratios, population structure and abiotic characteristics. The second objective was to understand the community use and requirements of mangrove wood from the Ntafufu Estuary. A participatory approach was followed to collect demographic data from each community, the requirements of mangrove poles and behaviour of harvesters. This was used to set up a framework to guide the sustainable management of mangroves based on the current status and stand dynamics of the mangrove communities. There are three mangrove species found in the Ntafufu Estuary: Bruguiera gymnorhiza (black mangrove) regenerates under the mangrove canopy and forms layers of even-aged stands. Avicennia marina (white mangrove) does not regenerate under a mangrove canopy i.e. the seedlings establish outside the canopy. A few Rhizophora mucronata (red mangrove) trees exist in the lower intertidal zone and form multiple stems on stilt roots. The mangrove associate, Hibiscus tiliaceus (wild cotton tree- mangrove associate), forms dense clusters of scrambling stems. Some of the Avicennia individuals show signs of mangrove bleeding and one individual of Bruguiera showed indications of disease. Mngazana and Ntafufu Estuaries had the highest tree densities of 2594 and 1402 trees ha-1 respectively, typical of riverine mangrove forest. The seedling to adult ratio was high in this study: 12.8 for B. gymnorrhiza and 24.3 for A. marina. Abandoned cut stems and laths were found during the study. Bark harvested for traditional medicine and cattle feeding in mangroves was also prevalent and expected to reduce the health of the forest. Mangroves in the Ntafufu Estuary are expanding, and the population structure of the three mangrove species showed a healthy balance between young and mature stems. The harvesting of Black mangrove (B. gymnorrhiza) poles for mainly roof construction is relatively limited. As part of the functions of the DAFF, the use of the mangrove resources has to be balanced with the resource availability from the mangroves, and this should result in a healthy functioning mangrove forest. Development of a participatory forest management (PFM) plan for a forest estate and its forest management unit, require an understanding of the mangrove communities and their dynamics, and the current level of resource use associated with the mangroves. The study recommended that a Mangrove Pole Harvesters Group is needed to practice silviculture through guidance of relevant governmental personnel.
- Full Text:
- Date Issued: 2020
- Authors: Mvakade, Monica , Rajkaran, Anusha
- Date: 2020
- Subjects: Estuarine ecology -- South Africa -- Eastern Cape , Aquatic ecology , Marine sciences , Fresh water
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49215 , vital:41611
- Description: Traditionally, coastal communities along the Wild Coast in the Eastern Cape, used mangrove forests for their livelihoods and socio-economic needs. Mangroves along the Eastern Cape coast are threatened by both natural and human factors. The wood obtained from the mangroves by rural households was used as poles for house and fence construction, firewood, and traditional medicine. This is a threat to the status of several mangrove species in this and surrounding areas. The harvesting of mangrove trees will have a direct and indirect effect on the other biotic and abiotic components of the mangrove ecosystems. The Department of Agriculture, Forestry and Fisheries (DAFF) (currently the Department of Environment, Forestry and Fisheries, or DEFF), through the National Forest Act no 84 of 1998, was directly responsible for the wellbeing of the national forests in South Africa. This also includes the mangroves as a specific national forest type. Several estuaries with mangroves occur within state forests. The harvesting and clear-felling of trees for timber and land conversion and associated waste of harvested mangrove poles and laths causes the many changes in mangrove forests. The aim of this study was to develop a framework for sustainable management of the mangroves for the Mtambalala forest management unit. This was done in relation to the requirements of the current legislation, policy guidelines and business plan of the management authority. The aim was pursued through two specific objectives. The first objective was to understand the variation in the composition in different parts of the Ntafufu Estuary, and the population dynamics of the main mangrove species, as basis for the development of sustainable resource use practices. Plots along transects were used to measure seedling to adult ratios, population structure and abiotic characteristics. The second objective was to understand the community use and requirements of mangrove wood from the Ntafufu Estuary. A participatory approach was followed to collect demographic data from each community, the requirements of mangrove poles and behaviour of harvesters. This was used to set up a framework to guide the sustainable management of mangroves based on the current status and stand dynamics of the mangrove communities. There are three mangrove species found in the Ntafufu Estuary: Bruguiera gymnorhiza (black mangrove) regenerates under the mangrove canopy and forms layers of even-aged stands. Avicennia marina (white mangrove) does not regenerate under a mangrove canopy i.e. the seedlings establish outside the canopy. A few Rhizophora mucronata (red mangrove) trees exist in the lower intertidal zone and form multiple stems on stilt roots. The mangrove associate, Hibiscus tiliaceus (wild cotton tree- mangrove associate), forms dense clusters of scrambling stems. Some of the Avicennia individuals show signs of mangrove bleeding and one individual of Bruguiera showed indications of disease. Mngazana and Ntafufu Estuaries had the highest tree densities of 2594 and 1402 trees ha-1 respectively, typical of riverine mangrove forest. The seedling to adult ratio was high in this study: 12.8 for B. gymnorrhiza and 24.3 for A. marina. Abandoned cut stems and laths were found during the study. Bark harvested for traditional medicine and cattle feeding in mangroves was also prevalent and expected to reduce the health of the forest. Mangroves in the Ntafufu Estuary are expanding, and the population structure of the three mangrove species showed a healthy balance between young and mature stems. The harvesting of Black mangrove (B. gymnorrhiza) poles for mainly roof construction is relatively limited. As part of the functions of the DAFF, the use of the mangrove resources has to be balanced with the resource availability from the mangroves, and this should result in a healthy functioning mangrove forest. Development of a participatory forest management (PFM) plan for a forest estate and its forest management unit, require an understanding of the mangrove communities and their dynamics, and the current level of resource use associated with the mangroves. The study recommended that a Mangrove Pole Harvesters Group is needed to practice silviculture through guidance of relevant governmental personnel.
- Full Text:
- Date Issued: 2020
Epibenthic biodiversity, habitat characterisation and anthropogenic pressure mapping of unconsolidated sediment habitats in Algoa Bay, South Africa
- Authors: Truter, Hannah Jessie
- Date: 2019
- Subjects: Aquatic ecology , Marine sciences Conservation biology Ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43812 , vital:37049
- Description: Implementation of an ecosystem-based management approach for marine systems requires a comprehensive understanding of the biophysical marine environment and the cumulative human impacts at different spatio-temporal scales. In Algoa Bay, South Africa, this study describes the epibenthic communities occurring in unconsolidated marine habitats. It further investigates the potential abiotic factors that influence their distribution and abundance, compares epibenthic communities with existing habitat information and evaluates the protection status of the marine environment in the Bay. Seabed imagery, covering a total area of 171.4m², and sediment samples were collected from 13 stations from which 106 epibenthic species were identified. Multivariate analyses revealed two statistically distinct communities that did not align with the Algoa Bay benthic habitat types defined in the current National Biodiversity Assessment (NBA, 2012). Further assessment indicated that community differences were driven by the presence of rock substrate. A range of abiotic factors were tested against the epibenthic communities to explore patterns and identify potential drivers. The combination of abiotic factors depth, mean grain size, mean bottom temperature and mean bottom current explained 55% fitted variation in epibenthic data. The degree of long-term variability in several of these parameters were likewise identified as explanatory variables, including bottom temperature, current speed and dissolved oxygen. The link between abiotic factors and the epibenthic communities observed indicate that these variables can act as surrogates for habitat mapping in the future. The existing and proposed Marine Protected Area (MPA) in conjunction with the NBA 2012 habitat types does well in protecting the majority of habitats in the Bay, however there remain habitats that lack protection. Utilising the benthic communities and potential drivers identified in this study, the proposed MPA boundary delineations should be somewhat altered to include missing habitat types.
- Full Text:
- Date Issued: 2019
- Authors: Truter, Hannah Jessie
- Date: 2019
- Subjects: Aquatic ecology , Marine sciences Conservation biology Ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43812 , vital:37049
- Description: Implementation of an ecosystem-based management approach for marine systems requires a comprehensive understanding of the biophysical marine environment and the cumulative human impacts at different spatio-temporal scales. In Algoa Bay, South Africa, this study describes the epibenthic communities occurring in unconsolidated marine habitats. It further investigates the potential abiotic factors that influence their distribution and abundance, compares epibenthic communities with existing habitat information and evaluates the protection status of the marine environment in the Bay. Seabed imagery, covering a total area of 171.4m², and sediment samples were collected from 13 stations from which 106 epibenthic species were identified. Multivariate analyses revealed two statistically distinct communities that did not align with the Algoa Bay benthic habitat types defined in the current National Biodiversity Assessment (NBA, 2012). Further assessment indicated that community differences were driven by the presence of rock substrate. A range of abiotic factors were tested against the epibenthic communities to explore patterns and identify potential drivers. The combination of abiotic factors depth, mean grain size, mean bottom temperature and mean bottom current explained 55% fitted variation in epibenthic data. The degree of long-term variability in several of these parameters were likewise identified as explanatory variables, including bottom temperature, current speed and dissolved oxygen. The link between abiotic factors and the epibenthic communities observed indicate that these variables can act as surrogates for habitat mapping in the future. The existing and proposed Marine Protected Area (MPA) in conjunction with the NBA 2012 habitat types does well in protecting the majority of habitats in the Bay, however there remain habitats that lack protection. Utilising the benthic communities and potential drivers identified in this study, the proposed MPA boundary delineations should be somewhat altered to include missing habitat types.
- Full Text:
- Date Issued: 2019
The chemistry of a new water-recirculation aquaculture system with emphasis on the influence of ozone on water quality
- Authors: Stobart, Michael David
- Date: 1992
- Subjects: Water quality -- Environmental aspects -- Testing , Ozone -- Physiological effect , Aquatic ecology , Aquaculture
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5244 , http://hdl.handle.net/10962/d1005087 , Water quality -- Environmental aspects -- Testing , Ozone -- Physiological effect , Aquatic ecology , Aquaculture
- Description: Water quality changes that occur during establishment and maintenance of nitrification in two identical recirculating aquaculture systems containing rainbow trout are described. The time taken for the nitrification process to become established was 40-45 days. Mortality of fish attributed to elevated nitrite concentrations were recorded during the initial conditioning phase of the systems. Un-ionised ammonia concentrations did not attain lethal levels during this period. Nitrate concentrations accumulated slowly throughout the study, while the pH and alkalinity of the water decreased with progressive nitrification. Levels of carbon dioxide, calcium, dissolved and suspended solids remained relatively stable until the carrying capacity of the systems was increased, upon which they increased rapidly and general water quality deteriorated. Permanently elevated concentrations of ammonia and nitrite served as an indication that the carrying capacity of the systems had been exceeded. The use of ozone as a water enhancement treatment in aquaculture systems during one- and six-hour applications was also considered in this study. Ozonation significantly reduced nitrite levels at · low concentrations (0,1 - 0,15 mg/l), although they returned to pre-treatment levels within a few hours of cessation of the treatment. The formation of an unstable, intermediate product that reforms as nitrite in the absence of ozone, rather than the complete oxidation of nitrite to nitrate, is proposed. Ozonation also resulted in decreased dissolved solids, and improved the clarity and odour of the water. Ozone had no effect on ammonia concentrations (at pH > 7,0), or on nitrate or calcium levels, and did not conclusively increase the redox potential of the water. Residual ozone concentrations up to 0,04 mg/l in a sixhour treatment had no harmful effects on rainbow trout, and there were no signs of gas-bubble disease arising from supersaturation of the water with oxygen. Activated carbon filters were effective at removing residual ozone from the water after treatment. Treatment of the water with oxygen alone had no effect on nitrite concentrations.
- Full Text:
- Date Issued: 1992
- Authors: Stobart, Michael David
- Date: 1992
- Subjects: Water quality -- Environmental aspects -- Testing , Ozone -- Physiological effect , Aquatic ecology , Aquaculture
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5244 , http://hdl.handle.net/10962/d1005087 , Water quality -- Environmental aspects -- Testing , Ozone -- Physiological effect , Aquatic ecology , Aquaculture
- Description: Water quality changes that occur during establishment and maintenance of nitrification in two identical recirculating aquaculture systems containing rainbow trout are described. The time taken for the nitrification process to become established was 40-45 days. Mortality of fish attributed to elevated nitrite concentrations were recorded during the initial conditioning phase of the systems. Un-ionised ammonia concentrations did not attain lethal levels during this period. Nitrate concentrations accumulated slowly throughout the study, while the pH and alkalinity of the water decreased with progressive nitrification. Levels of carbon dioxide, calcium, dissolved and suspended solids remained relatively stable until the carrying capacity of the systems was increased, upon which they increased rapidly and general water quality deteriorated. Permanently elevated concentrations of ammonia and nitrite served as an indication that the carrying capacity of the systems had been exceeded. The use of ozone as a water enhancement treatment in aquaculture systems during one- and six-hour applications was also considered in this study. Ozonation significantly reduced nitrite levels at · low concentrations (0,1 - 0,15 mg/l), although they returned to pre-treatment levels within a few hours of cessation of the treatment. The formation of an unstable, intermediate product that reforms as nitrite in the absence of ozone, rather than the complete oxidation of nitrite to nitrate, is proposed. Ozonation also resulted in decreased dissolved solids, and improved the clarity and odour of the water. Ozone had no effect on ammonia concentrations (at pH > 7,0), or on nitrate or calcium levels, and did not conclusively increase the redox potential of the water. Residual ozone concentrations up to 0,04 mg/l in a sixhour treatment had no harmful effects on rainbow trout, and there were no signs of gas-bubble disease arising from supersaturation of the water with oxygen. Activated carbon filters were effective at removing residual ozone from the water after treatment. Treatment of the water with oxygen alone had no effect on nitrite concentrations.
- Full Text:
- Date Issued: 1992
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