Nitrates and nitrites are measured separately. In a water analysis report, the nitrate concentration is compared to the limit of 50 mg/L, and that of nitrites, to the limit of 0.50 mg/L, also taking into account the condition regarding their simultaneous presence.
These requirements are set out in European Directive on the quality of water intended for human consumption and in Government Ordinance No. 7/2023, through which the directive is transposed in Romania.
The analysis shows you the nitrate and nitrite concentrations in your water. Based on this, you can determine whether you need a nitrate reduction cartridge.
What is the difference between nitrates and nitrites?
Nitrates and nitrites are forms of nitrogen found in water. The nitrate ion has the formula NO₃⁻, and the nitrite ion, NO₂⁻. The difference in composition is one oxygen atom, but the two parameters are evaluated separately.
Biological processes in the environment can transform one form into the other. Check the parameter name. The measured value and unit of measurement on the analysis report then allow you to compare the result with the corresponding limit.
| Parameter | nitrate | nitrite |
|---|---|---|
| Ion formula | NO₃⁻ | NO₂⁻ |
| Maximum value at the tap | 50 mg/L | 0.50 mg/L |
| Additional requirement at the exit of the treatment plant | 0.10 mg/L |
Also check the unit of measurement. The values in the table are expressed as nitrates and nitrites, while a result presented in another form, for example relative to nitrogen, needs interpretation before being compared to these thresholds.
Where do nitrates get into water?
European Environment Agency identifies mineral fertilisers and animal manure as the main sources of nitrates in groundwater in the European Union. The agency estimates that around 80% of the nitrogen discharged into the EU aquatic environment comes from agriculture.
Some of the nitrogen that is not taken up by plants can leach through the soil into groundwater. Some supply systems use this water as a source, and operators monitor the quality of the water distributed.
Data on nitrate sources explains why this parameter is monitored. Consult the analysis for your area. It describes the water in your supply area, and analysis of a tap sample provides information about the water in your home.
How to read limits and combined condition
For nitrates and nitrites, the check includes:
- Nitrates: at most 50 mg/L.
- Nitrites: maximum 0.50 mg/L at the tap. At the outlet of the treatment plant, the value of 0.10 mg/L applies.
- Combined condition: [nitrate]/50 + [nitrite]/3 ≤ 1, with both concentrations expressed in mg/L.
Also check the combined condition. This applies in addition to the individual limits, and for a sample with 40 mg/L nitrate and 0.3 mg/L nitrite, the calculation looks like this:
40/50 + 0,3/3 = 0,8 + 0,1 = 0,9.
The result is below 1, and both values are also below the individual tap limits. The example therefore complies with the requirements for these two tap parameters. The full potability assessment also includes the other parameters in the analysis.
Where to find the values for your home water
The water operator publishes analysis bulletins for the areas it supplies; if you can't find the report for your address on the website, you can request it directly. Check the analysis date and sampling point. These identify the sample to which the result refers.
Ask the laboratory for collection instructions. If you choose to analyze a sample from your home's tap, the sampling method must allow for the correct evaluation of the parameters you want to measure.
The taste and appearance of water cannot indicate the level of nitrates or nitrites. Use the measured values. Article Is tap water in Romania drinkable? explains in more detail the checks and reading of analysis bulletins.
The choice of equipment follows the parameter in the analysis. For nitrites, the reduction capacity is checked separately in the equipment documentation, as nitrates and nitrites are different parameters.
Which Olympus models have a nitrate cartridge?
The nitrate cartridge contains resin. The Olympus antimicrobial range includes dual and triple models that use it alongside the basic ceramic cartridge, and with the dual model you choose between the additional nitrate and lime cartridge. The triple model includes both.
| Exemplary | Additional steps over the basic cartridge | Price |
|---|---|---|
| Double filter Olympus for countertop | limestone or nitrates, your choice | 670 lei (134 €) |
| Double filter Olympus for under the counter | limestone or nitrates, your choice | 870 lei (174 €) |
| Olympus triple filter for countertop | limestone and nitrates | 920 lei (184 €) |
| Olympus triple filter for undercounter use | limestone and nitrates | 1,170 lei (234 €) |
The ceramic activated carbon cartridge provides the basic filtration. For this, Olympus claims to retain chlorine, pesticides, heavy metals, asbestos fibers, hexavalent chromium, arsenic, lead and cadmium, while allowing mineral salts and trace elements to pass through. Each additional stage has its own role. The nitrate cartridges described here reduce nitrates, and the limescale cartridges reduce water hardness.
Antimicrobial protection concerns the inside of the device. The manufacturer claims to destroy up to 95% of the microbes inside the device within two hours.
On standard models, the nitrate cartridge has a red thread and costs 225 lei (45 €). The GIGA models have white thread and cost 300 lei (60 €).
How to maintain your nitrate cartridge
Regeneration is done with water and salt. The frequency of this operation depends on the nitrate concentration in the water entering the filter and the volume consumed as the resin is used.
In the instructions, the Olympus indicates regeneration at approximately 150 liters for water with up to 55 mg/L nitrates and shorter intervals for higher concentrations. The value of 55 mg/L is a guideline for cartridge maintenance, not the legal limit for drinking water., which remains 50 mg/L.
Follow the model's instructions. According to them, more frequent regeneration and a lower flow rate favor nitrate reduction, and if you choose the device to correct a measured concentration, the result is verified by analyzing the filtered water.
The procedure includes holding the cartridge for 30-45 minutes in a container of saline solution, followed by rinsing and reassembly. The Guide replacement cartridges Olympus shows the steps and quantities indicated by the manufacturer. Change the resin cartridge every 10-12 months. This term remains valid even when you regenerate it regularly.
Nitrate reduction by reverse osmosis
Another option in the range is reverse osmosis filter Olympus, at €250, equipped with a separate tank and tap for filtered water. It has four stages.
According to the product description, the third-stage membrane retains nitrates and dissolved salts, including calcium and magnesium salts. The choice of such a system is made based on the composition of the water resulting from its analysis and the parameters you want to reduce.
To compare the capacity, assembly and maintenance of models, consult the 7 criteria for a good water filter.
Frequently asked questions
What is the difference between nitrates and nitrites?
The nitrate ion has the formula NO₃⁻, and the nitrite ion, NO₂⁻. They are different parameters, with distinct limits in tap water: 50 mg/L for nitrates and 0.50 mg/L for nitrites. The analysis must be interpreted separately for each, together with the combined condition required by law.
What is the limit for nitrates in drinking water?
The limit is 50 mg/L. Directive (EU) 2020/2184 and Government Ordinance No. 7/2023 provide for this value for nitrates, the limit of 0.50 mg/L for nitrites at the tap and the combined condition [nitrate]/50 + [nitrite]/3 ≤ 1.
Which Olympus filter do I choose for nitrate reduction?
A double model equipped with a nitrate cartridge or a triple model, which also includes a limescale cartridge. The range also includes a reverse osmosis system. The choice and maintenance are determined according to the water analysis and the product instructions.
How often do I regenerate the nitrate cartridge?
The manufacturer indicates approximately 150 liters for concentrations up to 55 mg/L and shorter intervals at higher concentrations. These values describe cartridge maintenance, not potability limits. The resin cartridge is replaced every 10-12 months.
Does filtered water retain minerals?
The ceramic cartridge with activated carbon allows the passage of mineral salts and trace elements. The final composition also depends on the other stages: the limescale cartridge reduces hardness, and the reverse osmosis membrane reduces dissolved salts.
Choose according to the analysis result
Keep the analysis report when comparing Olympus antimicrobial filters. The measured concentration, consumption and required maintenance are the benchmarks for choosing choosing the right model.
