Urban Water and Energy Use From Current US Use to Cities of the Future

The article describes and estimates the carbon greenhouse gas and water footprint of the urban water sector to achieving the sustainability goals of future (eco) cities. Specifically, the article focuses on two goals of reducing water use by 50% and zero net carbon (GHG) emissions. Water conservation from the current use to an achievable sustainable use cannot be achieved by water conservation only. Further reduction of the water demand by desalination and high degree treatment (e.g., nanofiltration or reverse osmosis) requires a significant amount of energy and there is a limit on the maximum percent of water that can be reused in a closed water cycle. Cluster semi-distributed water delivery, reclamation and reuse with heat energy recovery is described, followed by presenting a proposal for a regional integrated resource recovery facility (IRRF) which reclaims water for ecologic flow, irrigation and other uses, produces biogas, hydrogen, electric energy, struvite and residual organic solids for soil conditioning. It was estimated that the contribution of the water sector towards the net zero GHG emissions goal could be about 10%.