Water distribution system design and rehabilitation under climate change mitigation scenarios

The water industry is a heavy consumer of electricity to pump water. Electricity generated with fossil fuel sources produce greenhouse gas (GHG) emissions that contribute to climate change. Carbon taxation and economic discounting in project planning are promising policies to reduce GHG emissions. The aim of this research is to develop novel single- and multi-objective optimization frameworks that incorporate a new gene-coding scheme and pipe ageing models (pipe roughness growth model, a pipe leakage model, and a pipe break model) to examine the impacts of a carbon tax and low discount rates on energy use, GHG emissions, and design/operation/rehabilitation decisions in water systems. Chapter 3 presents a new algorithm that optimizes the operation of pumps and reservoirs in water transmission systems. The algorithm was applied to the KamalSaleh transmission system near Arak, Iran. The results suggest that a carbon tax combined with a low discount rate produces small reductions in energy use and GHG emissions linked to pumping given the high static head of the KamalSaleh system. Chapter 4 presents a new algorithm that optimizes the design and expansion of water distribution networks. The algorithm was applied to the real-world Fairfield water network in Amherstview, Ontario, Canada. The results suggest that a carbon tax combined with a low discount rate does not significantly decrease energy use and GHG emissions because the Fairfield system had adequate installed hydraulic capacity. Chapters 5 and 6 present a new algorithm that optimizes the optimal rehabilitation type and timing of water mains in water distribution networks. In Chapter 5, the algorithm is applied to the Fairfield network to examine the impact of asset management strategies (quantity and infrastructure adjacency discounts) on system costs. The results suggest that applying discounts decreased capital and operational costs and favored pipe lining over pipe replacement and duplication. In Chapter 6, the water main rehabilitation optimization algorithm is applied to the Fairfield network to examine the impact of a carbon tax and low discount rates on energy use and GHG emissions. The results suggest that adopting a low discount rate and levying a carbon tax had a small impact in reducing energy use and GHG emissions and a significant impact in reducing leakage and pipe breaks in the Fairfield system. Further, a low discount rate and a carbon tax encouraged early investment in water main rehabilitation to reduce continuing leakage, pipe repair, energy, and GHG costs.