Water 4.0—the next revolution in urban water systems

In his 2014 book, Water 4.0, UC Berkeley environmental engineer David Sedlak identifies four "revolutions" in the development of urban water systems. The first revolution—Water 1.0—was the Roman innovation of piping potable water in and sewage out of population centers, an advance adopted throughout European and North American cities. The second revolution—treating drinking water to kill infectious microbes—protected millions of urban dwellers from cholera, typhoid and ot