The United States has one of the safest drinking water supplies in the world, according to the Centers for Disease Control and Prevention (CDC). However, as an article from the Oregon Public Broadcasting website observed, additional water purification may be called for in certain situations:
During Portland’s boil water notice, it emerged that people with compromised immune systems should consult their doctors about drinking tap water — even when no warning is in effect.
Dr. Paul Lewis, the interim health officer for Multnomah County, says people with HIV/AIDS, or who’ve undergone an organ transplant or who are going through chemotherapy, are at particular risk of infection.
“Water is not sterile and as a result, if you have one of these special conditions, even normal otherwise healthful drinking water could potentially be dangerous,” said Lewis.
And that includes bottled water.
The Centers for Disease Control and Prevention says that to protect against cryptosporidium, for example, immuno-compromised people should only drink water that’s been distilled, cleaned through reverse osmosis, or put through a one-micron filter.
Understanding Reverse Osmosis
As the article pointed out, reverse osmosis is one way to rid water of such harmful pathogens. What exactly is this process, though?
In nature, a liquid that has a higher solute concentration passes through a permeable membrane towards a liquid with a lower solute concentration. The permeation will cease once the two liquids achieve equilibrium (that is, they have the same amount of solute). This, in a nutshell, is osmosis.
Reverse osmosis flips the process on its head by applying pressure on the liquid that has a higher concentration of solute (including bacteria) so that it passes through a superfine filter (membrane) towards a tank with clean water. According to AXEON Water Technologies, a reverse osmosis water filter system removes up to 96.5% of total dissolved solids, resulting in pure water that even people with weakened immune systems can safely drink.
Filters are the Key
To achieve such effective water purification, a new reverse osmosis water filter needs to be installed in the system first. There are many variants available, such as those made with activated carbon (effective in removing suspended particles and volatile organic compounds) or zeolite (ideal for sediment reduction), just to name a few.
Point-of-Use or Point-of-Entry
Homeowners also have a choice of where to install the reverse osmosis filtration. Point-of-entry installation places the system after the water meter, i.e. where the water first enters the home. As such, the entire water supply is purified. A point-of-use system, on the other hand, purifies water as it comes out of the kitchen or bathroom tap, so the device treats water only as needed instead of on a wholesale basis.
(Source: People With Compromised Immune Systems Must Always Be Careful About Drinking Water, Oregon Public Broadcasting, May 27, 2014)