Reverse Osmosis and The Purification of Drinking Water

As the perfect choice for water purification, Reverse Osmosis (RO) systems never fail to amaze us with clean, drinking water! A lot of household systems around the globe are reverse osmosis ones, and they don’t only improve water but also our way of living with it.

Water Purification Systems Filters

These systems commonly use the following filters:

  • a sediment filter to entrap particles like calcium carbonate and rust (sometimes a second sediment filter with tinier pores is also included.)
  • an activated carbon filter to block organic chemicals as well as chlorine, which will strike and break down thin film composite membranes and a second carbon filter to collect those chemicals that weren’t removed by the RO membrane
  • an RO filter which is also a thin film composite membrane
  • an ultraviolet (UV) lamp that sterilizes microbes which may escape the filtering process conducted by the RO membrane

Recent purification systems include nanomaterials and membranes.

CTA and TFC Membranes

Some systems don’t use a carbon filter, and a cellulose triacetate (CTA) membrane is utilized instead. CTA is a paper by-product membrane which is joined to a synthetic layer and is tailored to make contact with chlorine in the water. These need a little amount of chlorine in the water source to hinder bacteria from forming on the water. The usual rejection rate for CTA membranes is 85 to 95 percent, which means 85-95% of the contaminants are removed every use and if the system is functioning properly.

Cellulose Acetate Membrane Filter

CTA filter (Source:

However, CTA membranes are prone to decaying unless they’re preserved by chlorinated water. On the other hand, thin film composite (TFC) membranes are likely to break down when chlorine is present. TFC is made of synthetic material, and it demands chlorine to be dismissed before the water goes into the membrane. To protect TFC membranes from the damage caused by chlorine, carbon filters can be utilized as pre-treatment in RO systems. TFC membranes live longer than CTA ones, and they also have a higher rejection rate of 95 to 99 percent.

TFC RO Membrane

TFC RO Membrane (Source:

Membrane Pore Sizes

Depending on the filter type, the sizes of membrane pores may range from 0.1 to 5,000 nm (4×10−9 to 2×10−4 in).

Particle filtration can reject particles that are 1 µm (3.9×10−5 in) or bigger. Meanwhile, microfiltration can remove particles of 50 nm or larger. Ultrafiltration can get rid of particles that are roughly 3 nm or greater, and nanofiltration can remove particles of 1 nm or larger. Reverse Osmosis (RO) is in the last category of membrane filtration called hyperfiltration and can get rid of particles larger than 0.1 nm.

RO Systems and Water Purification

People living in rural areas without clean water can benefit much from portable RO systems. Because rural folks use river or ocean water for their everyday needs, RO systems can be advantageous for them since these water systems are tailored to purify water. With RO systems, they can drink healthy water that’s unpolluted, and therefore become healthier.

APEC Top Tier ROES-50

RO systems are also used in the manufacture of bottled mineral water. To get rid of the microorganisms and pollutants, the water first goes through a reverse osmosis system.

In European countries, they don’t just rely on RO systems alone. To eradicate contaminants, people use complete reverse osmosis systems which may include extra water treatment stages that utilize UV light or ozone to prevent microbiological contamination.