Reverse Osmosis Explained

The Future of Filtration

Reverse Osmosis is a popular method utilized in recycling and wastewater treatment, as well as consumer water filtration systems. It was back in the 1950s that scientists first considered the use of RO to desalinate ocean water, and although it worked, it was not practical due to the small volume produced. This changed when two UCLA scientists created hand-cast membranes made from cellular acetate, allowing larger quantities of water to move through the RO process more efficiently. In 1965, the first commercial RO desalination plant began running a small scale operation in Coalinga, California.

With a membrane that captures even the smallest particles, Reverse Osmosis (RO) is pretty amazing technology. Considered one of the best by the EPA, and shown to positively impact health, this technology is being implemented all over the world. From residential homes to large scale plants filtering millions of gallons per day, RO is at the forefront of clean water. Take a look behind the scenes.

What is Osmosis and how is it reversed?

The EPA describes Reverse Osmosis as units that “force water through a semi-permeable membrane under pressure, leaving contaminants behind. “ The process involves more than simply forcing water through a “screen”. RO requires a considerable amount of water pressure.

Get a visual of the process by checking out this video by the Government of South Australia, which uses RO to desalinate water in Adelaide.Water molecules are 10x smaller than contaminants

When you’re good – you’re good.

Reverse Osmosis is considered the best available technology by the EPA (BAT) when it comes to removing uranium, radium, and other radionuclides. It is the only type of filter capable of removing small contaminants like fluoride. The EPA states that RO filters “are effective in eliminating all disease causing organisms and most chemical contaminants”.

A few other ways RO is used:

  • The production of maple syrup – RO is used to separate the sugary concentrate from water in the sap.
  • The dairy industry uses RO filtration to concentrate whey and milk.
  • Wastewater goes through the RO process to create something drinkable, thereby earning the nickname, “toilet to tap” which may be unappealing, but provides developing nations with the ability to produce drinkable water.

As stated above, it’s also used to desalinate sea water. In Dubai, where fresh water is limited, large scale reverse osmosis filters converts about 416 millions of gallons of sea water to fresh water every day. Dubai’s groundwater supplies only 0.5% of the city’s water – that means the other 99.5% has to come from Reverse Osmosis.  In order to produce 416 million gallons of fresh water, the system has to pump about 2.8 billion gallons of water through it each day.

Dubai's main source of fresh water comes from reverse osmosis

What RO Can really doreverseOsmosis_feature

Reverse Osmosis filtering has been proven to have some seriously positive health impacts as well.

A classic example is this study which found that dialysis patients could prevent dementia (a comorbidity that occurred in 18 out of 258 patients) by simply using an RO filter. With no other treatment, scientists were able to improve the condition in 7 out of 9 previously exposed patients and prevent dementia in those whose water was treated from the start of the study.

Another study tracked the gastrointestinal health of 1400 families and found 14% more gastrointestinal illness in families drinking tap water than in those who were drinking water purified with reverse osmosis.

The Best Reverse Osmosis Water Filter

The best RO filters will have carefully engineered membranes that stand up to daily use. They filter for even the smallest particles, and include additional steps to ensure that the water it provides is both clean and healthy.

It’s important to do the research necessary to know how many contaminants an RO water filter truly removes.  The simple saying “don’t believe everything you read on the internet” goes a long way.  Look for NSF (National Sanitation Foundation) certifications. It should pass NSF/ANSI standards including NSF #42 for aesthetic effects and NSF #53 for health effects – read more about NSF standards here.

Consumer RO filtration systems generally do a good job of stripping out harmful contaminants, chemicals, minerals, and salt, but in the process, also strip the water of essential minerals. There is some disagreement on this issue, with some health experts stating that the amount of minerals in water is negligible anyway, so RO systems are a great option. However, the venerable World Health Organization and many other health experts have stated that water is an important source of minerals such as calcium, magnesium, and iron, especially for people in developing countries. The best water filter system is one that removes all the harmful particulates while remineralizing the water. That assures that it not only tastes great, but has the health benefits that essential minerals provide.


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