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Desalination water supply planning – Optimisation of environmental impacts and costs using life cycle assessment

Pakzad Shahabi, Maedeh (2015) Desalination water supply planning – Optimisation of environmental impacts and costs using life cycle assessment. PhD thesis, Murdoch University.

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Abstract

Desalination is an integral component of water supply for many cities and regions around the globe. Although, desalination can offer a rainfall independent source of water and provide social benefits, it is energy intensive compared to conventional water sources and can have significant impacts upon the environment. Therefore an interdisciplinary approach is required when planning for water supply by desalination. A life cycle assessment of a desalination supply chain can be integrated into an optimisation framework to simultaneously consider all possible planning alternatives and find the combination of planning decisions that optimizes environmental and economic objectives. This thesis aimed to develop a desalination supply chain optimization life cycle framework to analyze the economic and environmental impacts and trade-offs for alternative planning scenarios. The framework used life cycle assessment and a levelised cost model to quantify and compare the supply chain environmental and economic impacts for a range of planning scenarios. The framework incorporated a mixed integer linear programming model to determine optimal planning decisions such as water capacity expansion of each type of desalination technology over a planning horizon, and optimal locations of new desalination plants while considering interdependencies among water distribution and treatment processes. The framework was tested for future seawater reverse osmosis desalination planning in the northern metropolitan area of Perth, Western Australia over the next 20 years.

Results indicated that, a decentralised desalination supply system with small and medium-sized SWRO plants integrated into the Perth metropolitan area could achieve a lower environmental and economic impact, when compared to a centralised supply system with a large desalination plant located far from final demand. Improving seawater quality by introducing beach well intake - a mature intake technology for smaller-sized plants - could further promote the decentralised supply system environmental and economic performance. The capital expenditure contribution to total cost for the treatment facilities in the decentralised supply system was found to be higher than for the centralised supply system. However, this was outweighed by the significant water distribution pipeline construction and operational expenditure savings and also the operational expenditure savings associated with lower chemical and electricity use in the beach well plants. Construction phase contribution to treatment facilities life cycle environmental impact for the decentralised supply system was found to be higher than for the centralised supply system due to diseconomy of scale in smaller-sized plants. However, this was outweighed by significant water distribution pipeline construction and operational environmental impacts savings. Smaller plants with beach well intake benefit from operational environmental impact savings associated with lower chemical and electricity use. Multi-staged construction of successive small plants compared to single-stage construction of a large plant provided better economic outcomes due to lower interest costs. However, multi-staged construction led to higher environmental impacts associated with diseconomy of scale in the plant construction phase.

The case study provided numerous insights that were only possible through the use of a life-cycle optimization framework. For example, in desalination planning for a metropolitan area with land scarcity for siting new plants, the factors of supply system configuration, land-use patterns, environmental impacts and economic costs are highly inter-related and decision makers can consider these as a whole rather than considering each separately. The transparency and flexibility of the framework allows professionals from different disciplines to test the scenarios in a quantitative manner, to understand potential planning implications.

Publication Type: Thesis (PhD)
Murdoch Affiliation: School of Engineering and Information Technology
Supervisor: Anda, Martin, Ho, Goen and McHugh, Adam
URI: http://researchrepository.murdoch.edu.au/id/eprint/29533
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