Ordinary mechanical or carbon filters cannot effectively remove nitrates and nitrites. A specific physico-chemical separation is required, using one of three technologies: ion exchange, reverse osmosis or nanofiltration.
How to remove nitrates and nitrites from water in 2026?
1. Ion exchange (anion-exchange filtration)
The most common method for targeted removal of nitrates and nitrites. Water flows through a layer of special resin (anion exchanger), which selectively exchanges nitrate or nitrite ions for harmless chloride ions.
- Advantages: high efficiency, relatively low operating costs.
- Maintenance: the resin is regularly regenerated with a solution of ordinary salt (NaCl).
2. Reverse osmosis (RO)
A technology working on the principle of a molecular sieve. A membrane with a pore size of 0.0001 micron lets only water molecules through, while nitrates and other contaminants are sent to the drain.
- Advantage: very high efficiency – up to 98%
- Disadvantage: it also removes beneficial minerals from the water, which requires subsequent remineralisation, and that is usually not very effective.
3. Nanofiltration: the modern H2O nanotec standard
Nanofiltration is the “golden mean”. Its pores are small enough to eliminate nitrates, nitrites, microplastics, pesticides and medicine residues, but unlike reverse osmosis it keeps essential minerals (calcium, magnesium) in the water.
Chemistry and origin: why are nitrates found in water?
While microbiological contamination of water (bacteria) often shows up immediately, chemical contamination by nitrates and nitrites is a silent threat. It affects not only owners of private wells in agricultural areas but sometimes also users of public water supplies. In this expert overview we look at the chemistry of these substances, their impact on the human body and effective technologies for removing nitrates from water.
Nitrates (NO3−) are a natural part of the nitrogen cycle. The problem arises when their concentration is excessive, which is almost exclusively the result of human activity:
- Agriculture: excessive use of nitrogen fertilisers and their subsequent run-off into groundwater.
- Wastewater: seepage from septic tanks, cesspits and poor-quality sewers (a common problem in older housing areas, described in our article on well water filters).
- Nitrites (NO2−): these are much more toxic and occur less often in deep water because they are unstable and oxidise to nitrates. Their presence in a well signals recent faecal contamination or ongoing bacterial processes.
Health risks: from methaemoglobinaemia to carcinogenic threats
The toxicity of nitrates lies in their reduction to nitrites in the digestive tract.
- Infant methaemoglobinaemia: nitrites react with haemoglobin (the blood pigment) and convert it into methaemoglobin, which cannot carry oxygen. Infants, whose enzyme system is not yet fully developed, are at risk of oxygen deficiency (cyanosis) at higher concentrations. The enzyme system stabilises at around 2 years of age.
- Nitrosamines: in the stomach, nitrites can react with secondary amines to form N-nitroso compounds, which are classified as potential carcinogens increasing the risk of digestive tract cancer.
Drinking water limits in the EU
Limits for drinking water in the European Union are set by Directive (EU) 2020/2184. Stricter values are recommended for water used to prepare infant food.
| Target group | Nitrate limit (NO3−) | Nitrite limit (NO2−) |
|---|---|---|
| Adults (drinking water limit) | 50 mg/l | 0.5 mg/l |
| Infants and pregnant women (recommendation) | 10 mg/l | 0.1 mg/l |
The difference: tap water vs. your own well
For tap water, the supplier is responsible for meeting the limits. Even so, in some areas values are close to the 50 mg/l limit, which is not suitable for families with small children.
With private wells, all responsibility lies with the owner. Surveys in the Czech Republic show that up to 70% of private wells there do not meet the nitrate limits, especially in areas of intensive agriculture. Important: boiling water does not remove nitrates!
FAQ – nitrates and nitrites in drinking water
How can I detect nitrates in water without a test?
Nitrates are colourless, tasteless and odourless. The only reliable detection method is a laboratory water analysis or a certified home photometer.
Is an ordinary filter jug enough for nitrates?
Ordinary activated carbon jugs do not remove nitrates. You need special cartridges with anion-exchange media or systems based on nanofiltration or reverse osmosis (RO).
Is water with nitrates safe for bathing?
Yes, nitrates are not absorbed through the skin in dangerous amounts. The main risk is drinking the water and using it for cooking.
How often should a nitrate filter be regenerated?
The regeneration frequency depends on the inlet concentration and total water flow. Automatic stations regenerate by themselves; under-sink filters follow the manufacturer’s instructions, usually after a specified volume of water has passed through.
How do I remove nitrates from water?
Ordinary mechanical or carbon filters cannot effectively remove nitrates and nitrites. A specific physico-chemical separation is required using one of three technologies: ion exchange, reverse osmosis or nanofiltration.
Recommended solutions from the H2O nanotec online shop
Based on an analysis of your water source, we recommend the following specialised systems:
- Point-of-use kitchen filter: dedicated nitrate removal filter – an ideal under-sink solution using ion exchange. It is regenerable, which gives the media a service life of up to 6 years at minimal cost.
- Premium purity: IMT-NC9 nanofiltration – a top-class unit that deals with nitrates comprehensively together with viruses, bacteria and heavy metals, producing water suitable even for babies with a balanced mineral content.
- Combined solution: if your water also shows microbiological contamination (E. coli), it is necessary to install ultrafiltration upstream, which mechanically captures bacteria without using chemicals.
Written by:
RNDr. Jiří Polman CSc., Managing Director
