RO membrane (reverse osmosis membrane), its micron is 0.0001 to 0.001mircon.
Once the water is under a certain pressure, it will flow from high concentration to low concentration.
The water molecules can go through the RO membrane, and the organic matters, salts, heavy metals ions
in colloids, bacteria, viruses and other impurities can not pass RO membrane,
so it can distinguish the pure water and the concentrated water.