Even though 71% of the earth’s surface is covered in water, only 3% is fresh water. The rest of the water is the salty water found in oceans. But even the 3% freshwater is still not safe for consumption without treatment because it is polluted by natural and manmade factors. That underscores the importance of water purification. There are many technologies for purifying water but UV water filtration and reverse osmosis are arguably the most popular.

The difference between UV water filtration and Reverse Osmosis is that UV filtration will only remove bacteria from water while reverse osmosis will remove bacteria as well as other contaminants such as heavy metals. Reverse Osmosis (RO) water filtration systems use a semi-permeable membrane to filter out large particles, molecules, and ions from water. Ultra-Violet (UV) water filtration systems on other hand use an energy band that uses UV light to kill bacteria in water.

Reverse Osmosis systems can eliminate up to 99% of dissolved solids and other contaminants like chlorine, fluorine, heavy metals (e.g. cadmium, barium, lead, mercury, and chromium) from water.

In addition to filtering out impurities, RO systems are known to improve the flavor of the water. This is, in fact, the secret as to why Starbucks water tastes so darn good. RO-filtered water is, therefore, safe for drinking and food preparation.

On the other hand, UV water filtration uses radiation rays on 10-400 nm units to purify drinking water. These radiation rays kill all waterborne microorganisms, making the water safe for human consumption. UV filters do not, however, remove other contaminants from the water.

The UV rays have no effect on the odor to taste of water except for some rare circumstances when the water has some chemicals that might oxidize under the UV light. However, such oxidation is only possible when the water is exposed to the UV lamp for long periods, which seldom happens under normal UV water filtration.

UV water filtration vs reverse osmosis comparison table

Reverse Osmosis Systems	UV Light Systems
RO filtration systems use reverse osmosis technology to filter out contaminants from water. Through this technology, water is forced through a semi-permeable membrane that allows water through while trapping the contaminants.	For UV filtration systems, ultraviolet light (10-400 nm) is passed through the water thereby killing microorganisms in the water.
RO systems are perfect for removing chemicals, sediments, heavy metals, and any microorganisms that might be larger than the pores on the membrane. However, these systems may not be the best for eliminating bacteria from water.	UV light systems are perfect for eliminating all kinds of microorganisms in water. They are however not as effective in eliminating other contaminants like chemicals and sediments
RO systems are not only inexpensive to purchase but maintain as well. Replacing the filters is required at least once a month but the cost is negligible.	UV light filtration systems are costly to buy and maintain. The lamp that provides the UV light needs to be replaced at least once a year and it is quite pricey.
Reverse Osmosis systems generally consume very little energy although that might depend on the model	The UV light system consumes even less energy than typical RO systems.
RO systems filter out the contaminants in water and this helps to improve the taste of the water	UV filtration systems are very effective in killing bacteria in the water but they do not filter them out. As such, UV systems do not improve the taste of water.
Ro systems come with an in-built pre-filtration system which means they can filter muddy water to make it clean	UV systems will only kill disease-causing microorganisms but they can’t filter muddy water.
RO water filtrations systems rely on electric power to boost the water pressure	A UV system can work with the normal water pressure

So which one is better – UV filtration or a reverse osmosis system?

As you might have noticed from the comparison table above, both UV and RO systems have their distinct pros and cons. So, there is really no one-size-fits-all.

The best system for you will depend on what you are trying to achieve.

For instance, an RO system would be great if you are off-grid and trying to purify muddy water. But if you want to deal with bacteria, viruses, and other microorganisms, a UV system is what you need.

But for the most part, you will probably need both solutions. For instance, even after using a UV system to eliminate microorganisms, you will still need to filter out heavy metals and other contaminants. And the good news is you don’t have to buy both systems – you can buy one filtration system that combines the best of both worlds!

For instance, the Express Water Ultraviolet Reverse Osmosis Water Filtration System (amazon link) will filter your water using reverse osmosis technology and then use a UV lamp to kill harmful bacteria.

Final thoughts

If you are unsure which type of contaminants you are dealing with, you might want to test your water first. Just get in touch with a local lab and they should be able to do the test and advise on your best course of action.

But if you feel up to the task, you can also use a DIY kit to test the water yourself. When looking for a test kit, get one that tests for all kinds of contaminants.

Here is a link to a good one that I found on Amazon. It tests for lead, bacteria, iron, copper, fluoride, mercury, chlorine, nitrates, hardness, zinc, manganese, and total alkalinity.