Relationships between pumping costs and water quality in optimal operation of regional multiquality water distribution systems
- Authors: Mala-Jetmarova, Helena
- Date: 2016
- Type: Text , Thesis , PhD
- Full Text:
- Description: The operation of regional multiquality water distribution systems (WDSs) is a complex task involving multiple objectives in order to meet customer water quantity and quality requirements. These objectives, often conflicting, include scheduling of pumps to minimise pumping costs and mixing different quality waters from sources to ensure adequate quality water for customers. Evolutionary algorithms have been successfully applied to optimise operation of regional WDSs. Although a considerable reduction in pumping costs was demonstrated in past studies, other legitimate objectives, for example water quality, were not considered on an equal basis as they were included as a constraint. This single-objective approach precludes the tradeoffs between the objectives being obtained, so any insight on how to operate such a system cannot be provided should pumping costs and water quality be considered on equal basis. A multi-objective approach is applied in this thesis to optimise operation of regional multiquality WDSs considering pumping costs and water quality as legitimate objectives. Two optimisation models with increasing complexity are proposed. The first model considers two objectives, the pumping costs and a general water quality objective. The second model includes three objectives, the pumping costs and two water quality objectives for turbidity and salinity. The optimisation models are applied to three example networks from the literature using numerous scenarios and water quality data from the Wimmera Mallee Pipeline, Australia. A methodology is proposed to find the optimal solution for the multi‐objective optimisation of the WDS, which links a network simulator with a multi-objective genetic algorithm. Prior to optimisation, the performance of algorithm parameters is evaluated and their sensitivity analysed, for which a new methodology is developed. The following results were obtained. For the two-objective optimisation problem, there is a tradeoff with a competing nature between pumping costs and water quality. It means that reduction in pumping costs cannot be achieved without deterioration of water quality delivered to customers and vice versa. For the three-objective optimisation problem, interestingly, there is not a unique type of tradeoff (either competing or non-competing) between a particular pair of objectives. It is dependent on network hydraulics in combination with water quality at sources and customer water quality requirements. General principles behind the tradeoffs are formulated based on new categorisation of sources, so called consistent/inconsistent water quality (CWQ/IWQ) sources, in relation to customer water quality requirements. A practical approach for system operational strategy is developed for the purpose of long-term operational planning. It enables an operator to schedule supply from multiple sources with minimum pumping costs and customer water quality requirements being satisfied as much as possible, for all predicted water quality scenarios in the system.
- Description: Doctor of Philosophy
- Authors: Mala-Jetmarova, Helena
- Date: 2016
- Type: Text , Thesis , PhD
- Full Text:
- Description: The operation of regional multiquality water distribution systems (WDSs) is a complex task involving multiple objectives in order to meet customer water quantity and quality requirements. These objectives, often conflicting, include scheduling of pumps to minimise pumping costs and mixing different quality waters from sources to ensure adequate quality water for customers. Evolutionary algorithms have been successfully applied to optimise operation of regional WDSs. Although a considerable reduction in pumping costs was demonstrated in past studies, other legitimate objectives, for example water quality, were not considered on an equal basis as they were included as a constraint. This single-objective approach precludes the tradeoffs between the objectives being obtained, so any insight on how to operate such a system cannot be provided should pumping costs and water quality be considered on equal basis. A multi-objective approach is applied in this thesis to optimise operation of regional multiquality WDSs considering pumping costs and water quality as legitimate objectives. Two optimisation models with increasing complexity are proposed. The first model considers two objectives, the pumping costs and a general water quality objective. The second model includes three objectives, the pumping costs and two water quality objectives for turbidity and salinity. The optimisation models are applied to three example networks from the literature using numerous scenarios and water quality data from the Wimmera Mallee Pipeline, Australia. A methodology is proposed to find the optimal solution for the multi‐objective optimisation of the WDS, which links a network simulator with a multi-objective genetic algorithm. Prior to optimisation, the performance of algorithm parameters is evaluated and their sensitivity analysed, for which a new methodology is developed. The following results were obtained. For the two-objective optimisation problem, there is a tradeoff with a competing nature between pumping costs and water quality. It means that reduction in pumping costs cannot be achieved without deterioration of water quality delivered to customers and vice versa. For the three-objective optimisation problem, interestingly, there is not a unique type of tradeoff (either competing or non-competing) between a particular pair of objectives. It is dependent on network hydraulics in combination with water quality at sources and customer water quality requirements. General principles behind the tradeoffs are formulated based on new categorisation of sources, so called consistent/inconsistent water quality (CWQ/IWQ) sources, in relation to customer water quality requirements. A practical approach for system operational strategy is developed for the purpose of long-term operational planning. It enables an operator to schedule supply from multiple sources with minimum pumping costs and customer water quality requirements being satisfied as much as possible, for all predicted water quality scenarios in the system.
- Description: Doctor of Philosophy
Optimising water quality outcomes for complex water resource systems and water grids
- Authors: Dey, Sayani
- Date: 2023
- Type: Text , Thesis , PhD
- Full Text:
- Description: As the world progresses, water resources are likely to be subjected to much greater pressures than in the past. Even though the principal water problem revolves around inadequate and uncertain water supplies, water quality management plays an equally important role. Availability of good quality water is paramount to sustainability of human population as well as the environment. Achieving water quality and quantity objectives can be conflicting and becomes more complicated with challenges like, climate change, growing populations and changed land uses. Managing adequate water quality in a reservoir gets complicated by multiple inflows with different water quality levels often resulting in poor water quality. Hence, it is fundamental to approach this issue in a more systematic, comprehensive, and coordinated fashion. Most previous studies related to water resources management focused on water quantity and considered water quality separately. However, this research study focused on considering water quantity and quality objectives simultaneously in a single model to explore and understand the relationship between them in a reservoir system. A case study area was identified in Western Victoria, Australia with water quantity and quality challenges. Taylors Lake of Grampians System in Victoria, Australia receives water from multiple sources of differing quality and quantity and has the abovesaid problems. A combined simulation and optimisation approach was adopted to carry out the analysis. A multi-objective optimisation approach was applied to achieve optimal water availability and quality in the storage. The multi-objective optimisation model included three objective functions which were: water volume and two water quality parameters: salinity and turbidity. Results showed competing nature of water quantity and quality objectives and established the trade-offs. It further showed that it was possible to generate a range of optimal solutions to effectively manage those trade-offs. The trade-off analysis explored and informed that selective harvesting of inflows is effective to improve water quality in storage. However, with strict water quality restriction there is a considerable loss in water volume. The robustness of the optimisation approach used in this study was confirmed through sensitivity and uncertainty analysis. The research work also incorporated various spatio-temporal scenario analyses to systematically articulate long-term and short-term operational planning strategies. Operational decisions around possible harvesting regimes while achieving optimal water quantity and quality and meeting all water demands were established. The climate change analysis revealed that optimal management of water quantity and quality in storage became extremely challenging under future climate projections. The high reduction in storage volume in the future will lead to several challenges such as water supply shortfall and inability to undertake selective harvesting due to reduced water quality levels. In this context, selective harvesting of inflows based on water quality will no longer be an option to manage water quantity and quality optimally in storage. Some significant conclusions of this research work included the establishment of trade-offs between water quality and quantity objectives particular to this configuration of water supply system. The work demonstrated that selective harvesting of inflows will improve the stored water quality, and this finding along with the approach used is a significant contribution to decision makers working within the water sector. The simulation-optimisation approach is very effective in providing a range of optimal solutions, which can be used to make more informed decisions around achieving optimal water quality and quantity in storage. It was further demonstrated that there are range of planning periods, both long-term (>10 years) and short-term (<1 year), all of which offer distinct advantages and provides useful insights, making this an additional key contribution of the work. Importantly, climate change was also considered where it was found that diminishing water resources, particularly to this geographic location, makes it increasingly difficult to optimise both quality and quantity in storage providing further useful insights from this work.
- Description: Doctor of Philosophy
- Authors: Dey, Sayani
- Date: 2023
- Type: Text , Thesis , PhD
- Full Text:
- Description: As the world progresses, water resources are likely to be subjected to much greater pressures than in the past. Even though the principal water problem revolves around inadequate and uncertain water supplies, water quality management plays an equally important role. Availability of good quality water is paramount to sustainability of human population as well as the environment. Achieving water quality and quantity objectives can be conflicting and becomes more complicated with challenges like, climate change, growing populations and changed land uses. Managing adequate water quality in a reservoir gets complicated by multiple inflows with different water quality levels often resulting in poor water quality. Hence, it is fundamental to approach this issue in a more systematic, comprehensive, and coordinated fashion. Most previous studies related to water resources management focused on water quantity and considered water quality separately. However, this research study focused on considering water quantity and quality objectives simultaneously in a single model to explore and understand the relationship between them in a reservoir system. A case study area was identified in Western Victoria, Australia with water quantity and quality challenges. Taylors Lake of Grampians System in Victoria, Australia receives water from multiple sources of differing quality and quantity and has the abovesaid problems. A combined simulation and optimisation approach was adopted to carry out the analysis. A multi-objective optimisation approach was applied to achieve optimal water availability and quality in the storage. The multi-objective optimisation model included three objective functions which were: water volume and two water quality parameters: salinity and turbidity. Results showed competing nature of water quantity and quality objectives and established the trade-offs. It further showed that it was possible to generate a range of optimal solutions to effectively manage those trade-offs. The trade-off analysis explored and informed that selective harvesting of inflows is effective to improve water quality in storage. However, with strict water quality restriction there is a considerable loss in water volume. The robustness of the optimisation approach used in this study was confirmed through sensitivity and uncertainty analysis. The research work also incorporated various spatio-temporal scenario analyses to systematically articulate long-term and short-term operational planning strategies. Operational decisions around possible harvesting regimes while achieving optimal water quantity and quality and meeting all water demands were established. The climate change analysis revealed that optimal management of water quantity and quality in storage became extremely challenging under future climate projections. The high reduction in storage volume in the future will lead to several challenges such as water supply shortfall and inability to undertake selective harvesting due to reduced water quality levels. In this context, selective harvesting of inflows based on water quality will no longer be an option to manage water quantity and quality optimally in storage. Some significant conclusions of this research work included the establishment of trade-offs between water quality and quantity objectives particular to this configuration of water supply system. The work demonstrated that selective harvesting of inflows will improve the stored water quality, and this finding along with the approach used is a significant contribution to decision makers working within the water sector. The simulation-optimisation approach is very effective in providing a range of optimal solutions, which can be used to make more informed decisions around achieving optimal water quality and quantity in storage. It was further demonstrated that there are range of planning periods, both long-term (>10 years) and short-term (<1 year), all of which offer distinct advantages and provides useful insights, making this an additional key contribution of the work. Importantly, climate change was also considered where it was found that diminishing water resources, particularly to this geographic location, makes it increasingly difficult to optimise both quality and quantity in storage providing further useful insights from this work.
- Description: Doctor of Philosophy
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