Understanding the water-energy-carbon nexus in urban water utilities: Comparison of four city case studies and the relevant influencing factors

Although it is not at once evident, water supply and sanitation services provided by urban water and wastewater utilities consume a considerable amount of energy. Energy is an operational sine qua non in water treatment and distribution, wastewater collection, and treatment prior to disposal. How does the urban environment influence the water-energy-carbon nexus? The authors have tried to answer this question by referring to four case studies – based on the cities of Nantes (France), Oslo (Norway), Turin (Italy) and Toronto (Canada). Climate, technology and geography, inter alia, play important roles in shaping the water-energy-carbon nexus in different parts of the world. On the basis of an understanding of these differences and their influences, the authors have attempted to provide directions for process, program and policy interventions. For instance, Nantes needs to make an effort to restrict the use of herbicides and pesticides in order to improve the quality of water in the river Loire and thereby reduce the energy demand for treating raw water. Turin is a part, would do well to invest in more efficient wastewater treatment facilities, thus reducing the energy burden significantly on the upstream, while incurring a higher demand on the downstream. [Display omitted] •Energy is a sine qua non in the urban water sector.•Water-energy nexus is influenced by climate, technology and geography.•Multi-faceted approach is beneficial for systems analysis.•Two cities are never alike and need to contextually studied.•Turin, Oslo, Nantes and Toronto are compared in the paper.