Nitrate removal

Nitrate removal – we ensure clean water.

Nitrogen compounds such as nitrate have been used intensively as fertilisers in agriculture for decades. However, overfertilisation leads to nutrient surpluses that enter the groundwater via the soil. The result: rising nitrate concentrations in drinking water.

Legal limits

The Drinking Water Ordinance (TrinkwV) sets a limit value for nitrate of 50 mg/l for nitrate (Section 6 (2) TrinkwV). For nitrite, a limit value of 0.1 mg/l applies, whereby the combined concentration of nitrate and nitrite must not exceed 50 mg/l. The requirements are particularly strict for water used to prepare baby food – here, the maximum value is 10 mg/l.

In the public sector, municipal water suppliers ensure compliance with these limits. In the area of private water supply – for example, private wells – the operators themselves are responsible for this. Exceedances in these areas require targeted nitrate removal.

Health significance

Nitrate itself is not acutely toxic. However, it can be converted into nitrite in the human body, which promotes the formation of methaemoglobin, especially in infants. This can lead to cyanosis – a life-threatening disorder affecting oxygen transport in the blood. It is therefore essential to reliably reduce nitrate levels in drinking water.

Methods for nitrate removal

The removal of nitrate from water is technically possible, but depends on the method used. Common methods include:

• Ion exchange
  Nitrates are removed by an anion exchange resin and replaced with chloride ions. The total salt content of the water remains largely unchanged. The process is effective, but not completely selective – sulphate can also be removed.

• Reverse osmosis
  A semi-permeable membrane separates water from dissolved substances. Nitrate is almost completely removed, as are many other salts. The process is very effective but energy-intensive. Nanofiltration

• Nanofiltration
  Similar to reverse osmosis, but with larger pore sizes. Nitrate is largely removed, while some other minerals are retained.

• Biological processes
  Here, nitrate is broken down into harmless nitrogen compounds by microorganisms under anaerobic conditions – particularly interesting for large-scale industrial applications.

• Electrodialysis
  This electrochemical process separates ions using electricity through selective membranes. It is particularly suitable for industrial applications.

Areas of application

Nitrate removal processes are not only used in drinking water treatment, but also in wastewater treatment, in the food industry, in agricultural animal husbandry, aquaristics and fish farming.