Summary

With economic and population growth, industrialization, urbanization, and globalization, demand for natural resources such as water, energy, and food continues to increase, particularly in cities. Overconsumption of resources has led to degradation of the environment, a process that is interacting with and is further accelerated by a dangerous alteration to the climate. Fast growing cities worldwide already face severe technical difficulties in providing adequate infrastructure and basic services in terms of water and energy. This situation is set to become increasingly difficult with climate change impacts. The latter are increasingly affecting economically developing as well as developed countries. However, cities often have limited capacities to take comprehensive climate action. Hence, practicable, scalable, and adaptable solutions that can systematically target key entry points in cities are needed. The Water-Energy-Food (WEF) Nexus concept is one potential integrated urban planning approach offering cities a more sustainable development pathway. Within this concept, urban water reclamation with resource recovery offers a key potential: reclaimed products such as water, bioenergy, nutrients, and others are valuable resources for which markets are emerging. Reclaiming water can also reduce stress on natural resources and support the prevention of environmental pollution. Thus, it can support water, energy, and food security and the achievement of the United Nations Sustainable Development Goals. However, so far there are few implemented examples of urban water reclamation with resource recovery at urban scales. Examples of good practice in cities in China, India, and Europe highlight key enablers and barriers to the operationalization of water reclamation with resource recovery and implications in terms of environmental economics relevant for cities worldwide. These findings can support a systemic sociotechnical transition to a circular economy.