You cannot beat reverse osmosis water units when it comes to cleaning up water contaminated with salt. In that case they are worth the headaches. However, 95% of us get our water for a city utility company or from a chlorinated well that does not have a salt water problem. For us there is great news! Newer systems, called selective filtration, are simpler to install and use, cost less and produce healthier water than reverse osmosis. We will check out both systems in this article and you can decide.
Reverse osmosis (RO) systems work by pushing water against a semi-permeable membrane with pores so small that only objects the size of a water molecule, or smaller, will pass through. As a matter of fact, the pores are so small they will even reject a large part of the water itself along with minerals and most contaminants. In most RO systems, the rejected water is simply wasted. Typically, this amounts to about two or three wasted gallons for every gallon filtered.
Hard water or water with excessive minerals is a problem in many water supplies and the fact that RO systems remove these minerals is another plus for these systems. However, it also has been found to cause another problem.
You see, it seems water with no minerals is not good. That makes sense since nowhere on earth does pure water exist naturally. We need trace minerals like calcium and potassium, for example, in order to stay healthy. And, pure H2O is slightly acidic, so, when we drink this water it will try to get back to a neutral state by stealing minerals such as calcium from our teeth, bones or cells. In this case it produces calcium carbonate as its neutralizing element.
Health experts also tell us that cancer cells seem to grow only in a slightly acidic environment and, for that reason, they feels there is a long-term health risk associated with drinking demineralized water.
If you do decide on a RO system, be certain it comes with a carbon filter. This is because chlorine, a deadly poison, along with herbicides, pesticides, THMs, SOCs, drugs, etc., are made up of molecules smaller than water’s so they will not be removed by reverse osmosis systems.
If the water pressure in your home is too low, reverse osmosis systemes will require the addition of an inline booster pump in order to operate properly.
If you want to have more than just drinking water from an RO system you will need to add a storage tank, since these systems only filter a gallon or so of water per hour. In order to keep a constant pressure on the system a tank with a diaphragm is normally used.
By the time you put all the storage tanks, extra pumps (if needed), and filters together you are going to have a good sized unit. Anytime you have a lot of components you are likely going to be dealing with extra initial and operating costs, and maintenance issues.
Like I said, where they are good (with brackish water), RO systems are very good. But, as they have progressed to solve chemical problems, flow rate problems, etc.; they have become very Rube Goldberg like.
Now, let’s look at an alternative to reverses osmosis, the selective (or multi-stage) filtration system.
In selective filtration systems, carbon is mixed with a filter resin that has been chemically charged, and this mixture is then compressed into a solid block that has very small, submicron pores. The carbon, or course, removes chemicals and drugs that might be present in the water.
This carbon has a huge filtering capacity. They say a cubic foot of compressed activated carbon like this has a filtering area of five square miles! Plenty of capacity to clean up chemicals, and it also takes care of things like Cryptosporidium and Guardia (chlorine-resistant Cysts), and any remaining inorganic contaminants, with the submicron pores.
Why does the adsorption area have the chemically charged resin?
As water passes across the resin, positively charged heavy mineral ions in the water, like lead or mercury, for example, are forced to break their bonds with water, and attach to the chemically charged resin like little magnets. Lighter minerals like calcium and potassium stay put.
There you have it, the water is cleaned but it still has its nutritious trace minerals. Selective filtration systems are quick, so there is no need for holding tanks with diaphragms. Nor is there any need for booster pumps, electricity, backwashing, etc., and, if installed correctly, they operate virtually maintenance free.
Be sure you consult a technical representative for any system you are considering if the water you want to treat has extreme problems. They folks will invariably have a good solution. Also, please note that selective filtration is not designed to treat salt water.