Upgrading our inherited urban water systems

Environmental issues have to be discussed in the largest possible context. It is all too frequent that a miniature vision creates solutions with unanticipated detrimental effects in neighbouring fields of interest. It is noteworthy that the society has so few options, which may be identified by five verbs: no use, reuse, convert, contain and disperse. The future lies in analysis of the environmental issues in the context of total mass balance of important substances through society. Water is scarce only as long as it is lost by evaporation. The purpose of water usage is to pollute it, because the success of the past century has been to use water as a means of transport out of cities. It is a key issue that water usage can be diminished by demand control. There will still be polluted water to be purified. It is within the technological and economical range to purify water to a degree that would make it fit for urban reuse - to the point where the flow of water withdrawn from the environment can be diminished to a very small fraction of the present day withdrawal.