Water-energy nexus: retrofitting urban areas to achieve zero pollution

A major paradigm shift is examined for building new and retrofitting historic communities striving towards appropriate consumption of resources and reduced pollution: reusing and recycling water; recovering energy, nutrients, and other resources from used water and solids; attaining a sustainable use of water resources; and attaining net zero greenhouse gas (GHG) emissions targets. The key global and regional footprints identifying the trends towards the sustainable water-energy nexus in future ecocities are defined. Three scales are examined: domestic (individual building), cluster (ecoblock) and regional levels. An integrated approach to urban design and the use of water resources is presented. The future hybrid (partially closed) system would reclaim clean water, nutrients and other resources, and produce additional energy. Methane- and hydrogen-based energy recovery and conversion to electricity in an integrated resource recovery processes are proposed. The triple bottom line analysis and willingness to pay can be used to determine quantitative social values of non-market commodities (i.e. ecological enhancement, sustainability, improvements in water quality and aesthetic assets, and the reduction of GHGs emissions). Urban retrofit solutions are outlined for reducing water use, creating net zero GHGs, eliminating pollution, and generating financial revenue through the recycling and recovery of resources.