Overview of material and energy flows in water infrastructures in context of urban metabolism

Urban water and wastewater infrastructures (UWIS) are an essential part of every city. They manage large flow streams of water, organic substances and nutrients from urban areas. Management of flow streams has a considerable energy demand, while there are large opportunities for energetic reuse of wastewater resources, which are not yet sufficiently exploited. Energetic reuse of wastewater resources can contribute to more sustainable urban energy systems. UWIS are also hot spots for emission of anthropogenic pollutants to the environment. On the way to a sustainable metabolism of cities, restructuring energy systems and reducing emission of anthropogenic pollutants are two important challenges. Both involve UWIS. This paper analyses material and energy flows in UWIS in Germany and explores their contribution to urban metabolism. We conclude by highlighting potential improvements by new technologies.