With more than 30 years’ experience in the residential and commercial water treatment space, Mark Nelson is a Class 1 Drinking-Water Operator and a CBWA (Canadian Bottled Water Association) Certified Plant Operator. As founder and president of Nelson Water in Ottawa, Mark focuses on dealing with challenging water treatment system designs for problem water. He also heads the largest water bottling plant in the city of Ottawa with a delivery network throughout the Valley.
The reverse osmosis (RO) filtration process is a mystery for most people and there are a lot of myths surrounding this filter method. But, in reality this is less difficult to understand if you have a basic grounding in the subject matter. In this article, we will explain what RO filtration is, how it works and why it may be a good fit for your home.
What is RO Filtration?
RO filtration is a purely mechanical filter process that removes a wide variety of contaminants. So, no chemicals are added to the water and many are removed to make the water exceptionally clean. In fact, RO water is almost pure H20 with a purity of around 99.9% which is impressive.
How Does RO Filtration Work?
At the heart of the RO filtration system, there is a semi-permeable membrane filter with very tiny pores that allow water molecules to pass through. Most molecules of contaminants, such as: chemicals, metals and more cannot pass through. If they do, they are only present in trace quantities that represent no threat to health.
To make the system work the incoming water must be placed under pressure and forced through the RO membrane filter. The water pressure is increased to around 35 lbs psi (pounds per square inch). But, even under this pressure only small volumes of water are cleaned and this makes RO water untenable as an on-demand system.
To get around this problem, the purified water is stored in a tank which is usually located under the kitchen sink. A point-of-use faucet is connected and the pure water can be used for drinking, cooking and other tasks. If you like clean ice for your chilled beverages, you will love RO water because it contains no impurities.
What About the Contaminants?
The contaminants that are removed from the water accumulate on the surface of the RO filter membrane. As you can imagine, over time they will begin to clog the pores of the filter and this will degrade the performance and efficiency. To prevent this problem, the system periodically flushed the contaminants into the drain.
Does the RO Filtration System Use Other Filter Types?
Yes. Most modern RO filtrations systems have a four stage filter process to remove the contaminants and to protect the system from potential damage. Let’s take a look at these filter stages in the order that they are installed to process the incoming water:
1. The Pre-Filter
This is also known as a sediment filter, it’s placed at the front of the system to catch certain particulates that could damage the following filter stages. The particulates that it will remove, include: silt, sand, rust, and other suspended solids that may be 1 micron in size. A well functioning pre-filter will extend the lifespan of the entire RO filtration system.
2. The Carbon Filter
This filter stage will absorb a number of organic contaminants, such as: chlorine, chloramine (chlorine mixed with ammonia), herbicides, pesticides and other chemicals. This is important, because these chemicals can damage the semi-permeable membrane filter that’s next in line.
3. The RO Filter
This is a semi-permeable filter, the material used for this filter is usually polypropylene and it’s tightly wrapped to make the filter pores smaller. The RO filter removes some impurities that other filters cannot, including; asbestos, dissolved solids, bacteria, heavy metals, lead, pharmaceutical byproducts and more. But, the cleaned water may taste stale to many people because the minerals and other contaminants are stripped away. For this reason, a final filtration stage is required to give the water a final polish.
4. The Granulated Activated Carbon (GAC) Filter
These filters absorb any remaining pollutants that may affect the taste, odor and appearance of the RO water. They add some much needed character to make the water palatable and easier to use for drinking, cooking or baking.
What About the Healthy Minerals?
There is a common and pervasive myth that RO water is unhealthy because the mineral content is removed. To a certain extent this is true, but the full extent of these concerns is vastly overstated. It’s important to understand that most particulates that are removed from the water during RO filtration have the potential to be harmful. Some calcium and magnesium in drinking water is desirable because they are healthy minerals. But, the body doesn’t absorb these minerals easily in this format when compared to food. When minerals have been processed through plants, the inorganic minerals are converted to organic minerals that are extremely beneficial for health. So, a healthy diet should be orientated to the consumption of mineral rich foods and the mineral content of drinking water is less important.
Is a RO Filter System Necessary?
Yes. Even though public water is cleaned and disinfected to a basic standard there are still substantial risks to consider. Any break along our aging water infrastructure network can allow contaminants to enter our water supply. Certain emergent or secondary contaminants are not fully understood or identified as health risks and they are not removed. Another problem is the chlorine and chloramine that is used to kill bacteria and other harmful microorganisms. These are effective chemical disinfection agents, but in recent years there have been concerns about the health risks of chlorine byproducts. More study is needed, but these byproducts may be linked to certain types of cancer.
How Long Will a RO Filter Last?
The lifespan of a RO filtration system is 10-15 years and it will be at the upper limit of that range if the essential annual maintenance needs are met. It’s important to service and sanitize the system to ensure that it’s working at optimal efficiency. The RO membrane filter will require replacement every 2-3 years depending on the water quality and the volume used. The other three filters tend to last for 6-9 months before they need replacement.
If you want to install a RO filter system or your existing system requires maintenance, contact your local water treatment specialist today.