Nitrates and other chemical impurities in water - what do they mean and how do we remove them?
Water can be completely transparent, odorless, and tasteless, yet still contain dissolved chemical substances that can only be detected through laboratory analysis.
Such substances become particularly important in the case of well water, spring water, and other groundwater sources, as water naturally dissolves various minerals as it moves through soil and rocks. Additionally, agricultural activities, fertilizers, sewage systems, and other sources can introduce nitrates and other undesirable compounds into the water.
One of the most important indicators of this kind is nitrate content.
What are nitrates?
Nitrate (NO₃⁻) is a natural nitrogen compound and a normal part of the nitrogen cycle. In small amounts, it naturally occurs in soil, water, and plants.
The problem arises when the concentration of nitrate in water significantly increases.
Sources of nitrate contamination in groundwater include:
- Intensive use of nitrogen fertilizers;
- Animal manure and agricultural runoff;
- Malfunctioning or improperly located septic tanks;
- Sewage leaks;
- Decomposition of organic waste;
- Surface pollution entering groundwater.
According to USGS water studies, nitrogen compounds originating from fertilizers, manure, and wastewater can seep into the soil and eventually reach groundwater. Aquifers located close to the surface are particularly vulnerable to such contamination.
Why are nitrates particularly important in well water?
Groundwater often appears very clean. Nitrate contamination may cause no:
color change, turbidity, odor, or particular taste.
That is why a visual assessment of water is not sufficient.
A well should be checked with particular care if there is agricultural land, a fertilizer application area, animal housing, a septic tank, or another potential source of contamination nearby. The WHO also emphasizes the protection of wells from septic systems, manure, and surface runoff.
What amount of nitrate is permissible in drinking water?
According to the Technical Regulations for Drinking Water in force in Georgia, the maximum permissible level of nitrates is defined as:
Nitrate (NO₃⁻) - 50 mg/L
The same regulations specify for nitrites:
Nitrite (NO₂⁻) - 0.2 mg/L
The regulations also set limit values for arsenic, lead, cadmium, mercury, nickel, chromium, fluorides, and other chemical substances. You can view the Georgian Technical Regulations for Drinking Water here.
In the WHO Guidelines for Drinking Water Quality, the guideline value for nitrate is also 50 mg/L, as NO₃⁻.
In some foreign laboratory reports, you may encounter a different notation - for example, nitrate as nitrogen / NO₃-N. In such cases, the numbers should not be directly compared to results expressed as NO₃⁻, as a different calculation unit is used. For example, the US EPA sets the maximum nitrate level at 10 mg/L as nitrogen, which corresponds to approximately 44 mg/L NO₃⁻.
Why can a high nitrate content be a problem?
Some of the nitrate in the body can be converted to nitrite. Nitrite, in turn, can interfere with the normal transport of oxygen by hemoglobin.
The most vulnerable group is infants, especially those under six months of age, when water with high nitrate content is used to prepare infant formula. This condition is called methemoglobinemia and is often known as "blue baby syndrome."
The WHO's guideline value of 50 mg/L for nitrate is set precisely with the protection of the most vulnerable groups in mind.
Therefore, high nitrate content is not merely a matter of water "quality" or taste – it is one of the important chemical parameters for safety when evaluating drinking water.
Nitrates are not the only invisible chemical problem
Water can contain dozens of different dissolved substances. Some are of natural origin, while others enter the water as a result of human activity.
Important parameters can include:
- Arsenic;
- Lead;
- Cadmium;
- Mercury;
- Nickel and Chromium;
- Fluorides;
- Chlorides and Sulfates;
- Sodium;
- Nitrates and Nitrites;
- Pesticides and other organic compounds.
Some of these primarily affect the taste, corrosiveness, or technical properties of water, while others are health-regulated contaminants. Therefore, "water has many minerals" and "water is chemically contaminated" are not the same thing.
Does TDS show how safe water is?
This is one of the most common misunderstandings.
TDS - Total Dissolved Solids shows the total amount of dissolved substances in water, but it does not show what specific substances are in the water.
For example, a significant portion of the TDS in one water sample may consist of calcium, magnesium, and bicarbonates, while another water sample may have different dissolved ions.
Therefore:
Low TDS ≠ automatically safe water
and
High TDS ≠ automatically dangerous water.
In the EPA classification, a TDS value of 500 mg/L is presented as a Secondary Drinking Water Standard – meaning it primarily relates to taste, mineralization, sediment, and other aesthetic/technical characteristics, and not to determining the concentration of a specific hazardous substance.
You cannot use a TDS meter to determine, for example, how much nitrate, arsenic, or specific heavy metals are in the water.
For this, a chemical laboratory analysis is required.
How to find out if there are nitrates in the water?
The most reliable way is laboratory testing.
In the case of well or spring water, it is advisable that the analysis is not limited to TDS, hardness, or pH alone.
Depending on the water source and environment, it may be necessary to check indicators such as:
Nitrates, nitrites, ammonium, iron, manganese, hardness, chlorides, sulfates, arsenic, heavy metals, and microbiological indicators.
The Georgian Technical Regulations also specifically highlight nitrogen forms—ammonia, nitrate, and nitrite—among the parameters for chemical water monitoring.
Which filter removes nitrates?
Not all water filters work the same way.
This is particularly important in the case of nitrates, as nitrate is a dissolved ion in water.
Mechanical filter - no
A 5, 10, or 20 micron mechanical cartridge is effective for sand, rust, sediment, and other solid particles.
But it cannot remove dissolved nitrate.
Activated carbon - not the primary technology for nitrate removal
Activated carbon is very effective against many organic substances, chlorine, taste, and odor problems, but a regular carbon filter is not designed to remove strongly soluble ions like nitrate.
Ultrafiltration - no
Ultrafiltration is effective for retaining very small particles and microorganisms, but dissolved nitrate ions pass through the membrane.
Reverse Osmosis - one of the effective solutions
Reverse Osmosis - RO is a membrane technology used to reduce dissolved salts and many other chemical components from water.
The WHO directly lists among effective technologies for nitrate removal:
- Reverse Osmosis;
- Ion Exchange;
- Biological denitrification;
- Electrodialysis.
According to WHO data, these technologies can significantly reduce nitrate in properly designed systems; at the same time, conventional coagulation, sedimentation, filtration, and chlorination are not effective for nitrate removal. You can view WHO technical information here.
Penn State Extension also identifies reverse osmosis, appropriate ion exchange, and distillation as methods for nitrate reduction in household settings.
Does boiling water remove nitrate?
No.
Boiling does not remove nitrate from water.
Moreover, when part of the water evaporates, nitrate remains in the remaining water and its concentration can increase. The WHO therefore warns that prolonged boiling is not a solution when dealing with nitrate problems.
This is an important distinction compared to microbiological contamination: heat can inactivate many microorganisms, but dissolved chemical substances do not simply disappear from water.
Why is water analysis necessary before selecting a filtration system?
The selection of a water filtration system should not be based on just one indicator.
For example, the main problem in one well might be:
Hardness and iron,
In another:
Nitrates and microbiological contamination,
And in a third, several chemical parameters simultaneously.
In these cases, the required technologies are completely different.
That is why the correct sequence for treating well water and natural spring water is:
Water analysis → problem identification → selection of appropriate technology → proper system design.
Not the other way around.
The main thing to remember
Clear and good-tasting water does not always mean that its chemical composition is ideal.
Nitrates and many other dissolved substances can be present in water without you noticing them by color, odor, or taste.
If you use well or spring water, periodic laboratory testing and knowing the actual composition of the water are especially important.
And if an analysis reveals an exceedance of nitrates or other chemical indicators, the filtration technology must be selected according to the specific results.
At Aquarea, you can provide us with a laboratory analysis of your water, and based on it, we will select the appropriate treatment and filtration system.