Abstract
The goal of this case study is to demonstrate the application and utility of a developed System Dynamics (SD) model to assess the sustainability of strategic decisions for managing the wastewater collection (WWC) pipe network system for a medium-size municipality in Southern Ontario. Two asset management scenarios, suggested by the research-partnered municipality, are adapted based on the acceptable maximum fraction of pipes in the worst condition (ICG5) being equal to (1) 10% of the network-length/year, and (2) the initial 2.8% of network-length/year for the entire life cycle of the asset. The urban densification scenarios are restricted to a 50% urban densification rate. The least maximum rehabilitation rates of 1.41% and 1.85% of network length/year are found necessary to keep the ICG5 pipes fractions below the selected 10% and 2.8% thresholds, respectively. The maximum and minimum user fee-hike rates for WWC and wastewater treatment (WWT) services are adjusted to support the financial self-sustainability aspect. Results from the SD model, as presented over a 100 year simulation period, show that an accelerated rehabilitation strategy will have a lower financial cost with the lowest greenhouse gas (GHG) emissions. This study highlights the implications of integrating asset management of wastewater-collection and -treatment systems. Applying such an integrated SD model will help decision makers to forecast the future trends related to social, economic, and environmental performances of wastewater infrastructure systems, and evaluate the behavior of interrelated and complex WWC and WWT systems to find synergistic cost-saving opportunities while at the same time improve sustainability.
Highlights
The government of Canada has announced the $53 billion “New Building Plan” for rejuvenation of Canadian public infrastructure, the largest infrastructure investment in the nation’s history [1].The rehabilitation and expansion of municipal infrastructure, including water and wastewater systems, will not happen without consequences to social, environmental and economic systems
This study demonstrates the application and utility of system dynamics (SD) model developed by Mohammadifardi et al [2] to evaluate the future sustainability performance of policies and asset management strategies for wastewater infrastructure systems
The average affordability of the WWC and wastewater treatment (WWT) services for a residential user who is expected to use the services for 100 years; Life cycle cost of asset management to continue provisioning of the WWC and WWT services for the municipality; Life cycle greenhouse gas (GHG) emissions from WWC pipe network system and other infrastructure affected by the strategic decisions
Summary
The government of Canada has announced the $53 billion “New Building Plan” for rejuvenation of Canadian public infrastructure, the largest infrastructure investment in the nation’s history [1]. Water and wastewater utilities should consider the long-term sustainability impacts of their decisions when developing their policies and strategic asset management plans. This study demonstrates the application and utility of system dynamics (SD) model developed by Mohammadifardi et al [2] to evaluate the future sustainability performance of policies and asset management strategies for wastewater infrastructure systems. It is important to note that the presented SD model results should be treated as a forecast model that estimates future systems trends and the long-term sustainability performance over a 100-years forecasting period This model assumes steady state behavior and no shocks occur to the system over this 100 year forecasting period. It is inherently and inevitably assumed that the current socio-economic, political, environmental, and technological conditions will be at steady state so that the influence of strategic decisions on life cycle performance of wastewater infrastructure systems can be investigated
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