Membranes

Membrane filters act as a barrier to separate contaminants from water, or they remove the particles contaminating the water. Reverse osmosis, ultrafiltration, and nanofiltration all use a membrane in their different filtration processes.

What is membrane filtration?

Filter membranes have different configurations. There are reverse osmosis (RO) membranes, ultrafiltration (UF) membranes, and nanofiltration (NF) membranes. They all approach the membrane filtration process a little bit differently.

How does a membrane filter work?

Reverse osmosis applies pressure to a semipermeable membrane that allows the water molecules to pass through while flushing the dissolved inorganic compounds to the drain. So it separates the water into two pathways.

Ultrafiltration doesn't separate the water like a reverse osmosis membrane. It actually is just an ultra-fine particulate or sediment filter. With mechanical filtration particulate down to 0.025 microns cannot pass through the ultrafiltration membrane.

Nanofiltration membrane technology works very similar to reverse osmosis, except the filtration is not quite as fine.

How often should you replace a membrane filter?

Reverse osmosis membrane: Every two or three years, depending on the water quality. As the RO membrane rejects more minerals, some of those minerals start to come out of solution and clog the surface area of the membrane. If you feed the RO system with softened water, then the membrane could last five years, if you replace the filters on a regular basis.

Ultrafiltration membrane: Every other year for a point-of-use (POU) application. UF membranes do collect contaminants as they filter.