Reverse osmosis explained
Osmosis can generally be described as a process whereby a liquid (e.g. water) naturally and spontaneously passes through a semi-permeable barrier, which results in the liquid on the other side of the barrier becoming more concentrated than the original.
Reverse osmosis, by contrast (RO), is when the direction of the liquid flow is reversed. This is where a high concentration of liquid travels through a semi-permeable membrane to become a low concentration. Reverse osmosis also requires energy to force the liquid under pressure through the semi-permeable membrane.
In reverse osmosis water treatment, certain unwanted properties are pushed out. These are then discharged through the system’s wastewater stream.
Under law and by tightly controlled regulations and standard, tiny amounts of more than two dozen contaminants are permitted to be present in drinking water. However, while treated water is carefully monitored to be as clean as it can be, it is still possible for this same ‘wholesome’ water to gather contaminants as it travels beyond the water treatment plant, via the distribution network and into your home through domestic plumbing. For example, if a homeowner hasn’t replaced any lead pipes entering their old property, then that is one way their drinking water could be contaminated.
What do I need to know before installing a reverse osmosis (RO) system?
There are benefits and drawbacks to the use of any technology, so it is up to consumers to decide if a reverse osmosis drinking water system is right for their home, their lifestyle and budget.
The main benefit of installing a reverse osmosis drinking water system is that it can filter out trace inorganic chemicals, which have been left behind as part of a water company’s water treatment process (or added in the case of fluoridated water).
These inorganic chemicals include:
- Total dissolved solids (e.g. salts such as sodium and inorganic matter)
Many consumers find this more rigorous filtration process an attractive and a healthier proposition.
With its semi-permeable membrane pore size of approximately 0.0001 micron, a reverse osmosis system can also be highly effective in removing:
- Protozoa (single cell organisms)
- Bacteria (e.g. salmonella, E.Coli)
- Viruses (e.g. Hepatitis A, Coronavirus)
A reverse osmosis system can also soften the water, which may be a useful characteristic in a hard water area.
However, the removal of some trace minerals by a reverse osmosis system may result in your new RO water tasting differently from what you are used to.
Another factor in deciding whether to purchase a reverse osmosis water system is cost. According to the Drinking Water Inspectorate, 20-30% of the water coming into a reverse osmosis system is ejected (or recycled) as wastewater, which it claims may result in increased water bills. However, this increase is negligible, as 95% of domestic water used is not drinking water. For many people, this is manageable and acceptable in light of the perceived health benefits.
Outside of a domestic setting, large-scale reverse osmosis units are in operation all over the world, taking salt out of seawater and turning it into water for drinking, farming and industry.