How does a reverse osmosis filter work?

The best way to understand how RO works is to first grasp the concept of osmosis. Osmosis is the natural process of passing water through a semi-permeable membrane. The process forces water to move from a lower concentration region to a higher concentration region. This can be seen in how plants absorb water. In reverse osmosis, however, the opposite is true. Water is forced to move to lower concentration instead of increasing concentration because the RO membrane prevents contaminants from passing through it.

The reverse osmosis filter system is more effective in removing dissolved solids, particles, and solvents than other filtration methods because of the pressure applied and the selective feature of the membrane. It employs the semi-permeable membrane technique in conjunction with a series of carbon filters. These are classified as pre-filters or post-filters depending on where they are in the filtration process. The water with the lowest concentration of contaminants is known as permeate, while the water with the highest concentration is known as brine or waste.

Stages of the RO system

A typical RO system has one to five filtration stages. The most common are three, four, or five-stage RO systems. As expected, 5-stage reverse osmosis provides the highest level of water purification by reintroducing essential minerals in the fifth stage. All reverse osmosis systems operate on the same basic principles, which include one or more sediment filters, a carbon filter, and the RO membrane.

1st Stage – Sediment filter

This is typically the first (prefilter) stage in the RO filtration process. It is the stage at which visible contaminants like silt, debris,  dirt, dust, and other sediments are separated from water coming from a water supply source (e.g. well or tap)

2nd / 3rd Stage – Pre-carbon filters and RO membrane

The carbon filter and the RO membrane works to remove chlorine, Volatile Organic Compounds (VOCs), and other impurities that may affect the color or odor of water. These stages include the pre-activated carbon filters, the RO membrane, and the activated carbon filters.

4th Stage – Semi-permeable membranes

At this stage, further removal of harmful chemicals (such as fluoride, lead, and chromium) and other elements occurs as water is forced through the semipermeable RO membrane. This stage removes about 95 to 98% of Total Dissolved Salts (TDS) in water.

5th Stage – Post filtration

Here, the water passes through a final filtration membrane that removes any more particles that may have escaped all other filtration stages. Most 5-stage RO systems use a remineralization process to add vital minerals that may have been removed back into the water at this stage. At the 5th stage, our RO water filters use granular activated carbon filters with a unique mix of carbon derived from burnt coconut shells.

6th Stage – Enhanced alkaline filtration

The water produced at the 5th stage of the RO process is pure, healthy, and safe to drink. However, some RO filters include the sixth stage for remineralization and alkalinization. Because the RO process is thought to have stripped certain minerals from the water, the 6th stage is included to add back essential minerals while also reducing water acidity to make it alkaline. Alkaline water has numerous benefits, including increased hydration and antioxidant properties.