Does Reverse Osmosis Remove Nitrates from Water?
Written by: Gene Fitzgerald // Last Updated: Feb 22, 2023
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While nitrates are abundant, both naturally occurring and manufactured, an excess in your drinking water is a known health hazard, particularly to babies and the elderly.
In areas with a lot of agricultural industry and homes with well water, it is essential to check the level of nitrates in the water to determine if you need to filter them out.
A reverse osmosis system is a popular choice for this particular purpose.
But does reverse osmosis even remove nitrates from water? Let’s find out!
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Key Takeaways
- Yes, reverse osmosis does remove nitrates from water.
- The average nitrate reduction rate of a home reverse osmosis system is about 80 to 95%.
- Ion exchange and distillation are two more effective methods for reducing or eliminating nitrates in your water supply. Boiling water will only concentrate the nitrates.
- There are multiple things we can do to reduce the risk of nitrates ending up in our water supply, ranging from properly constructing private wells to minimizing our personal use of fertilizers.
Does Reverse Osmosis Remove Nitrates from Water?
A nitrate is essentially a salt, and RO filtration systems are excellent at removing salts.
Water will enter the RO unit and will be pushed through a semipermeable membrane that traps nitrates on one side while allowing the purified water to flow through the other.
This process removes about 80-95% of nitrates in the source water, which in most cases, will bring the nitrate level in drinking water down to a safe level.
So yes, reverse osmosis does remove nitrates.
How Well Does a Reverse Osmosis System Remove Nitrates from Water?
Reverse osmosis is one of the most effective methods for reducing the level of nitrates in your water supply. However, it will not remove all traces of them, only about 80-95% as mentioned before. For example:
- The AquaTru Water Filter has been certified to remove 87.2% nitrate.
- The Aquasana OptimH2O has been certified to reduce 82.40% of combined nitrate and nitrite.
This only becomes an issue if your source water has a very high level of nitrate in it. For example, if your source water has 100 ppm of nitrates, then filtration may only bring that level down to 15 ppm, which is over the recommended safe level.
This is why it is crucial to have your source water tested to see what you are working with and to determine the ideal filtration setup (you may end up needing more than one kind of filtration process).
Other Treatment Ways to Remove Nitrate from Water
Ion Exchange Filtration
Cation exchange is found in water-softening treatments, but a different kind of ion exchange can be used to remove nitrates.
Ion exchange filtration for nitrates is a resin filter coated with chloride ions, which will readily exchange themselves with nitrate and sulfate ions in the water.
After a certain amount of water has passed through, the resin will run out of ions to exchange, and the filter will no longer be effective. Obviously, this will happen faster if your water has a lot of nitrates it needs to trade. Good news is, just let your nitrate filter regenerate by backwashing with sodium chloride and it’s as good as new.
One downside: If your water is high in sulfate, the exchange process will favor the sulfate over the nitrate. This is why having your water checked to understand its composition is important, as this may not be an appropriate method for your particular water chemistry.
Water Distillation
Water distillation is considered by some to be the gold standard of water purification, as it is capable of eliminating almost all waterborne pathogens and contaminants. It works by heating the water until it becomes steam, then sending that steam into a cooling coil until it is liquid again.
The process of turning the water into steam tends to leave a lot of contaminants behind as they cannot move as a gas. The ones that can are removed by a carbon post filter.
Nitrates cannot survive the distillation process. The downside is that it is extremely slow and can take 6 hours to distill a gallon of water, so if you don’t have some stored, you may be stuck without it. Water distillers also consume quite a lot of energy when used on a daily basis.
Does Boiling Water Remove Nitrates?
It doesn’t, and it actually will concentrate the nitrates in your water. As with distillation, when the steam leaves the boiling water and dissipates, it won’t take the nitrates with it, and they will be left behind with your water in the kettle, meaning less water in the boiler but just as many nitrates.
Compared to distillation, which turns all the water to vapor, collects it, and turns it back into water, boiling water eliminates the vapor, and most of the water stays in its liquid state.
How About Water Softening?
While nitrate filters use a similar chemical process as a water softener, you cannot use a water softener to remove nitrates. This is because a water softener uses cation exchange to remove the minerals that make hard water, but a nitrate filter uses anion exchange based on chloride.
To use a water softener to remove nitrate, you will need nitrite-specific resin; most water softeners do not have that.
What Are Nitrates?
Nitrates are natural compounds found in the atmosphere, the soil, and in water. They are made up of nitrogen and oxygen and are usually created by decomposing plants and animal waste.
They can also be found in artificial sources such as inorganic fertilizers, herbicides, and pesticides. This is why nitrate concentrations in water supplies are often higher in areas with a lot of agriculture.
Where Do Nitrates Originate from? How Do They End Up in Our Water Supplies?
Nitrates are naturally occurring, and as they are soluble in water, rainwater and floods can introduce them to ground and surface water supplies.
While all rainfall will contain some nitrate or nitrogen, the use of inorganic fertilizers and animal manure on farmland can mean an increased concentration of nitrates in these areas.
Nitrogen can leach through the soil and get into groundwater and wells. The most common ways they end up in water supplies are due to agricultural runoff, industrial waste, fertilizer use, leaking septic tanks, and broken sewerage systems.
Nitrates are considered to be the most common contaminant for well owners. They are tasteless, colorless, and odorless but capable of causing illness in both humans and animals.
City Water
While the level of nitrates in city water is monitored, and the risk of excessive amounts in your municipal water is low, they may get into the tap water after the water has left the municipal plant. Sources include animal waste, fertilizers, or leakage from a private septic system.
Well Water
An increase in nitrates in private well water is thought to come from using artificial fertilizer and waste disposal from animal farming. Improper location and construction of wells are also issues, allowing a more accessible point of entry for nitrate-laden waste.
Bottled Water
The FDA regulation for allowable nitrate in bottled water is 45 ppm. Should bottled water exceed this, it is required to be labeled as having excessive nitrate. So, bottled water usually contains a ‘safe’ level of nitrate unless otherwise marked.
How Much Nitrate Is Considered Safe in Drinking Water?
According to the EPA, the nitrate maximum contaminant level in water should not exceed 45 ppm of nitrate or 10 ppm of nitrate-nitrogen. Water with less than that is considered to be safe for drinking. Water that has a higher concentration than the above could lead to health issues.
Health Effects of Too Much Nitrate in Water
The primary demographic of people who are at high risk for nitrate contamination are babies and the elderly. Too much nitrate can decrease the ability of red blood cells to carry oxygen around the body. Infants who are drinking baby formula mixed with tap water that is nitrate contaminated are at risk of developing ‘blue-baby syndrome’, also known as methemoglobinemia.
When a child is 0-4 months old, nitrate converts to nitrite in their stomachs. This then binds to oxygen molecules in the infant’s blood. It will cause a bluish skin color to develop around the eyes and mouth, and if it is caught at this early stage, it can be easily diagnosed and treated. However, if it is not detected, it can be fatal. It is less of a risk after the age of 6 months, as at that age, nitrate no longer converts to nitrite in the stomach.
It is also possible for pregnant women to pass methemoglobin to their developing fetus, causing low birth weight. Nitrate consumption from drinking water is not considered much of a health risk for generally healthy adults, as studies from the WHO have shown.
Further Reading:
How to Test for Nitrates in Water
It is recommended that your water be tested for nitrates, particularly if you have a private well or live in rural areas with a high amount of farming and agricultural activity.
Nitrates are tasteless, colorless, and odorless, so it can be particularly difficult to tell if they are in your water supply at unsafe levels.
A water test kit is the best testing method, which is then submitted to a laboratory for analysis. These test kits can assess dozens or even hundreds of possible water contaminants, including nitrate. Multiple samples of the water should be collected in vials, and the laboratory will test them the same way they test municipal water and bottled water.
Once you have already tested your water and installed the relevant water filtration systems, the water should be periodically tested for nitrate at home using test strips.
How Can You Prevent Nitrates from Getting into Your Water?
Reverse osmosis, water distillation, and ion exchange are good ways to remove or reduce nitrates from your drinking water, but it is challenging to eliminate them in other ways.
Installing a point-of-entry anion resin tank is an effective solution to removing nitrates from the water in your household. However, as discussed earlier, they need to be maintained regularly, and your water should not contain excess sulfur.
Some households will install both: The anion resin at the point of entry and a reverse osmosis system at their point of use. Having the water pass through two points of contaminant removal will purify the water further to ensure there is no trace of nitrate left in it.
Other methods to reduce the likelihood of nitrates getting into your water supply include:
- Construct your well far away from potential sources of contamination, and ensure your well is deep.
- Perform routine maintenance and inspection on your well from a professional.
- Do not use fertilizer or pesticides near your well.
- Have your well water tested on a routine basis to monitor the contaminants that may be present.
- Test your tap water regularly to make sure your filtration systems are working as they should.
- Keep granular and weed fertilizers on your lawn, not on paved areas, to ensure they are not washed into stormwater drains.
- Do not over-spray liquid herbicide, and avoid spraying it when it is windy.
- Catch the rinse water from cleaning your fertilizer equipment, and dispose of it on the lawn.
- Look into using organic fertilizer or DIY fertilizer.
If you have any questions about reverse osmosis nitrate removal please don’t hesitate to leave a comment below!
About the Author Gene Fitzgerald
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