Environment: New Water

The Seine is a river of filth; yet Parisians willingly drink its waters. The Moskva traces an equally grimy course through Moscow, but Muscovites will soon be able to hold a glass under the kitchen faucet and savor Moskva water straight. The citizens of Singapore and Amsterdam, too, will shortly be able to drink from their polluted rivers. Between the stream and the lip, in all these cases, is a remarkable process developed in France that changes effluent into elixir.

The key ingredient in the process is not chlorine, which purifies most of the U.S. water supply, but a gas called ozone...