Evaluating the Impact of Climate Change Mitigation Strategies on Water Distribution System Design and Optimization

Abstract

In response to growing environmental concerns, policy makers in Canada have been developing climate change mitigation strategies that will enable Canada to meet medium and long-term greenhouse gas (GHG) emission reduction targets. The water industry is energy- and carbon-intensive, thus the magnitude and long-term uncertainty of proposed carbon mitigation policies could have implications for water distribution system capital planning decisions that are made today.

The intent of this thesis was to examine the implications of discount rate and carbon price uncertainty on cost, energy use and GHG emissions in the design/optimization of the Amherstview water distribution system in Loyalist Township, Ontario, Canada. A non-dominated sorting genetic algorithm is coupled with the hydraulic solver EPANET2 in a single-objective optimization approach to identify network expansion designs that minimize total cost as the sum of: i) capital cost of installing new and parallel pipes and of cleaning and lining existing pipes; ii) operation cost of electricity for pumping water; and iii) carbon cost levied on electricity used for pumping water. The Amherstview system was optimized for a range of discount rates and carbon prices reflective of possible climate change mitigation strategies in Canada over the next 50 years. The problem formulation framework was developed according to a “real-world” municipal approach to water distribution system design and expansion. Decision variables such as pipe sizes are restricted to “real-world” commercially-available pipe diameters and parameter values are chosen according to engineering judgment and best-estimates. Parameter uncertainty is characterized by sensitivity analysis rather than the more computationally-demanding and data-intensive Monte Carlo simulation method. The impact of pipe material selection on energy use and GHG emissions was investigated for polyvinyl chloride and cement-mortar lined ductile iron pipes. Results from this first-ever study indicate that the discount rate and carbon prices investigated had no significant influence on energy use and GHG emissions in the Amherstview system. Pipe material selection was also found to minimally affect the amount of GHG emitted in the Amherstview system.