Does Reverse Osmosis Remove Nitrates?

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Nitrate contamination in drinking water is concerning, but luckily, removing this contaminant at home is fairly easy – or it is when you have the right treatment system.

In this guide, we’ve answered the question, “Does a reverse osmosis system remove nitrates?”

πŸ“Œ Key Takeaways:

  • Nitrate is a harmful contaminant that gets into water from fertilizer runoff, leaking septic tanks, animal waste, and erosion of deposits in the environment.
  • Reverse osmosis (RO) water purification is an effective method of greatly reducing nitrates in drinking water.
  • An RO system filters nitrates, and up to 99.99% of total dissolved solids, in a process called membrane separation.
  • Good alternatives to RO filters for reducing nitrate levels are ion exchange systems and water distillers.

πŸ€” Do Reverse Osmosis Systems Remove Nitrates?

Reverse osmosis filters are the most effective at-home water filtration systems for nitrate removal.

These systems are often called water purifiers because of their ability to remove high concentrations of TDS (total dissolved solids) from tap water.

Since nitrates are a kind of dissolved solid, they’re effectively reduced in an RO system.

Under sink reverse osmosis system

πŸ“Š How Much Nitrates Do Reverse Osmosis Systems Remove?

A reverse osmosis system is unlikely to eliminate nitrates entirely, but this water treatment method should reduce nitrates by up to 95%.

The amount of nitrates removed by RO depends on a few factors including:

  • The age of the RO membrane – A newer membrane will reduce a higher concentration of nitrates than an older, degraded membrane.
  • The membrane quality & pore sizeThe higher the membrane quality and the smaller the pore size, the more nitrates can be removed.
  • The concentration of nitrates in drinking water – The more nitrates in the water supply, the higher the likelihood that some will slip through the membrane.
  • The other contaminants present in the water – Certain other impurities may reduce the RO membrane’s ability to remove nitrates.

There’s no set percentage for nitrates removal that applies to all RO systems. To find out how much nitrate a specific RO filter removes, look at third-party test results for the system. Or, if this information isn’t available online, contact the manufacturer directly.

πŸ”Ž How Do Reverse Osmosis Filters Remove Nitrates?

A reverse osmosis water filtration system removes nitrates with a process known as membrane separation.

There are a few stages in an RO system, including a sediment filter and two carbon filter cartridges – but these aren’t capable of reducing nitrates.

It’s the RO semi-permeable membrane that traps nitrates and effectively separates them from water.

The membrane has tiny pores (as small as 0.0001 microns), which only water molecules and a select few tiny impurities can pass through. Nitrate particles are too large to pass through these pores, so they rebound off the membrane and are flushed out of the system in a wastewater solution.

Wondering whether reverse osmosis systems can remove nitrates and nitrites? The answer is yes – both nitrate and nitrite particles are, for the most part, too large to slip through the RO membrane’s pores, and are separated from the pure water particles.

RO systems provide consistent access to purified water. That means, whenever you turn on your faucet, you’ll have nitrate-free water on tap.

Illustration of a membrane filtration process in a reverse osmosis system
Membrane Separation Process in a Reverse Osmosis System

🧐 Should You Use A Reverse Osmosis Filter For Nitrate Removal?

Reverse osmosis systems are the best solution for treating a water supply with elevated nitrate levels.

Many folks love these systems because they don’t just reduce one or two contaminants – they remove virtually everything, eliminating the potential health risks of water impurities and producing bottled water quality from your faucet.

However, they do have some setbacks.

For instance, RO systems are most commonly found as under-sink or countertop units, so they provide point-of-use treatment for drinking water only.

There are some whole-house RO filters, but they cost $4,000+, making them inaccessible to many. That means you probably won’t be able to reduce nitrates in your entire home’s water supply with reverse osmosis.

RO systems also waste water and require multiple filter changes per year, and you might not want the extra expense of this kind of system compared to other water treatment solutions.

πŸ‘¨β€πŸ”§ We recommend reading up on reverse osmosis systems and how they work, then deciding whether or not these systems are the best nitrate reduction solution for you.

Usws defender whole house ro system after installation

🚰 Alternatives To RO For Reducing Nitrates

Before you invest in an RO water filter for reducing nitrates, make sure you know what other water treatment systems you can use for this purpose.

Ion Exchange Systems

If you’re looking for a way to remove nitrates from whole-home water supplies, consider an ion exchange system.

The most well-known ion exchange system is the water softener. Water softeners exchange sodium ions with hard water ions (known as the ion exchange process), effectively reducing these minerals in water.

An ion exchange system for nitrate reduction works similarly, exchanging chloride ions with nitrate ions on a charged resin bed. When the chloride is used up and the resin is saturated with nitrates, the system regenerates, recharging the resin with a sodium chloride solution.

The biggest setback of this water treatment system is that it can only effectively remove nitrates from water if the water’s sulfate levels are low. Ion exchange technology is biased towards removing sulfate ions, so if your primary goal is removing nitrates, you’ll probably need a pre-treatment solution for sulfates.

Water Distiller

Will boiling water remove nitrates alone? No, but if you distill the water by boiling it, then condensing it into a separate container, you can effectively reduce your water’s nitrate levels.

You don’t have to do these processes manually if you have a water distiller. Simply add drinking water to the boiling chamber of this countertop unit, then switch it on and wait for the water to boil.

The boiling water will begin to evaporate, and this water vapor travels through a cooling corridor and condenses, drop by drop, into a clean carafe. The majority of impurities (including nitrates) are trapped in the boiling chamber because they’re unable to evaporate and condense at the same temperatures as water.

Like reverse osmosis, water distillation is a highly effective method of reducing all drinking water impurities, greatly improving water quality.

Imber isla distiller performance

πŸ“‘ Final Word

The Environmental Protection Agency (EPA) has set a Maximum Contaminant Level of milligrams of nitrogen per liter (mg/L) for nitrate-contaminated water.

Nitrates are considered a primary water quality contaminant because of their numerous health effects (including damage to red blood cells and a dangerous disorder known as blue baby syndrome). So, you’re doing the right thing by looking into how to remove this contaminant from your drinking water.

If you haven’t already, get your private drinking water tested and find out the concentration of nitrates present. From there, you can decide whether reverse osmosis or another form of water treatment is the best solution to remove this harmful impurity.

Water testing with tap score
  • Laura Shallcross
    Senior Editor

    Laura is a passionate residential water treatment journalist who holds an undergraduate degree in Print Journalism and a master’s degree in Creative Writing. Over a span of 5 years she's written on a range of topics including water softening, well water treatment, and purification processes.

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