France, March 22 -- At a pilot plant run by the Île-de-France Water Authority (Sedif), water is stripped of pesticides, forever chemicals and other pharmaceutical residues.  

This is done using "membranes", reveals Camille Pain-Le-Quere, an engineer for Franciliane, the company appointed by Sedif to manage its drinking water. She is responsible for monitoring the pilot facility. 

"A membrane is a filtering material which, under pressure, retains certain compounds in the water. These are spiral-wound membranes. The water goes in and the clean water comes out in the centre," she explains.  

"These membranes combine nanofiltration and reverse osmosis. And with nanofiltration, we're talking about 1/1000 of a micron...