Energy in the urban water cycle: Actions to reduce the total expenditure of fossil fuels with emphasis on heat reclamation from urban water

In the urban water cycle, water supply, transportation, treatment and disposal are services that consume a considerable amount of energy. This paper reviews and summarizes state of the art measures applied in different parts of the world to reduce the energy consumption related to urban water. Based on a literature review, an overview of the energy balance in the urban water cycle in some regions of the world is presented. The balance shows that water heating is the largest energy expenditure with approximately 80% of the total primary energy demand in the residential sector of the cycle, while the remaining 20% of energy is spent by waterworks on pumping and treatment. Examples of measures to reduce the consumption of energy are presented according to a philosophy of actions in order to achieve energy efficient processes. The emphasis is on technologies and case studies to recover the energy from urban water, as well as some factors that influence the deployment of the technologies.