Urban water systems for sustainable cities

This thesis addresses the need to plan, design and manage infrastructure systems in light of sustainability objectives. With rising populations, sprawling suburbs and deteriorating infrastructure combined with environmental degradation, many cities worldwide face difficult choices in the development of infrastructure. A three-pronged approach is utilized in this thesis to explore some of these issues.;With the philosophical framework established, the next step is to understand the state of the environment. Estimation of environmental inputs and outputs is performed using complementary methodologies, materials flow analysis and life cycle assessment at two different scales. At the level of the city, the urban metabolism of the Greater Toronto Area is quantified and compared to other cities worldwide. Generally, inputs have increased at higher rates than outputs over the study years. At the level of urban water systems, an inventory of greenhouse gas emissions from Canadian municipal wastewater treatment plants is prepared using a life-cycle approach. Both on-site emissions due to the biological processes used and fossil fuels consumed and upstream emissions related to off-site production and transmission of fuels and the off-site production of electricity are included. The total on-site emission rate of carbon dioxide (CO2) is estimated at 669,000 tonnes/yr rising to over 1,000,000 tonnes CO2 equivalent emissions/yr once upstream emissions are included.;Finally, state of the environment reporting is combined with sustainability indicators in the development of a model for scenario and impact analysis for the City of Toronto urban water system. "What-if" scenarios are developed to assess the system-wide impacts of water distribution pipe renewal, sewer relining, demand management strategies and energy recovery from anaerobically digested wastewater biosolids. The impacts of climate change and population growth are also assessed. Initiatives targeted at the early stages of the urban water cycle have greater positive downstream impacts on selected environmental indicators. Specifically, strategies aimed at reducing water demand produce more significant system-wide benefits.;Firstly, a sustainability framework which focuses on key interactions and feedback mechanisms between infrastructure and surrounding environmental, economic and social systems is developed. A generic set of sustainability criteria and sub-criteria and system-specific indicators are proposed.