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Monitoring nitrate concentration in drinking water

Why too much nitrate in drinking water is harmful and what can be done about it.

Plants in potting soil

Nitrogen from nitrates is a necessary nutrient for plants to survive. However, excessive concentrations are harmful to humans and nature. An excessive nitrate concentration should therefore be avoided in drinking water in particular.

How nitrate gets into groundwater

Nitrate is a natural compound that is created in the atmosphere and is completely harmless to start off. Nature makes use of nitrate in a natural cycle for fertilising plants.

What has fertiliser got to do with it? 

It must be said that people disturb this cycle as an imbalance is created by ever-increasing artificial and local fertilisation, such as the use of fertiliser for agricultural purposes. If more fertiliser is applied than the plants can absorb, then nitrate enters rivers and lakes via rainfall, and then gets into our groundwater.

Agriculture fertilizer

Excessive nitrate can be hazardous to health 

About 80% of the benchmark value for nitrate is taken in via our food, such as by eating vegetables, fruit and meat. If drinking water with a high nitrate content is also consumed over a prolonged period, this can be harmful to humans.

It is therefore recommended by the EU and WHO to have a limit of 50 mg/l nitrate in drinking water. In Switzerland, the Water Protection Ordinance (GSchV) even prescribes a nitrate limit of 25 mg/l, to protect babies from high concentrations in particular. Infants do not create enough of the necessary enzyme for breaking down nitrate in the body. In countries where these thresholds are being exceeded, it is recommended that babies are given water that is particularly low in nitrates.

Unpolluted water is becoming scarce

For this reason, water suppliers who currently do not have high levels of nitrate in their water and therefore have no need to process it can consider themselves fortunate. For others, who already have nitrate in raw water due to agriculture, the situation will become tougher over the coming years. After all, with increasing population growth, the demand for water will exceed the available water resources in many places in the future. Even back in 2019, 13% of the groundwater measuring points in the EU already showed nitrate values above the limit of 50 mg/l. In many places, therefore, considerable efforts will be necessary to be able to continue to reliably supply drinking water of appropriate quality.

Two person taking Nitrate Samples

How can nitrate be removed from water? 

Almost all nitrates are soluble in water and chemically extremely stable, meaning that they can only be removed with considerable technical effort. However, only a few of the existing technologies seem suitable for providing denitrified water for the supply of drinking water systems. 

For example, they remove the nitrates from the water by reverse osmosis, distillation or strongly basic anion exchange resins. However, this results in highly concentrated brine residues, which cause problems during disposal and therefore significantly increase operating and maintenance costs. When all the nitrate gets into waste water then the problems start once again, namely, with the extraction of raw water.

Suitable measures have a sustainable effect

In the long term, systems that do not require technical processing are therefore the better, more sustainable and less expensive alternative. That said, they do require corresponding accompanying measures, such as protecting well shafts, land use management, which monitors or even forbids the agricultural use of water in the area where it is taken, deactivation of wells if nitrate levels are excessive or mixing up various water sources.

Nitrate monitoring with Bürkert

And this is exactly where Bürkert’s strength comes in: from the analysis of well water, the quality inspection of drinking water to blending different wells – customers get everything from a single source with us. 

Type 8905

Online water analysis system

Type 8905
  • Continuous analysis of drinking water and industrial process water
  • Based on the modular Bürkert cube and backplane technology
  • Fieldbus connection for versatile industrial communication
  • Fieldbus connection for versatile industrial communication, data exchange via mobile gateway
  • Extremely low-maintenance and long service life thanks to MEMS technology

 

We use our MS09 nitrate sensor to ensure this when it comes to nitrates as well.

Type MS09

Nitrate sensor

Type MS09
  • UV photometer for nitrate monitoring
  • Reagent-free optical measurement
  • EDIP sensor: compatible with Type 8905/8906 measurement stations
  • Xenon flash lamp, 3 channels for optical measurement with reduced interference
  • Nano-coated glasses to reduce maintenance

How does our nitrate sensor work?

This optical sensor consists of a lamp and a detector that measures the strength of the light. The lamp shines through a gap, through which water continuously flows, directly onto the detector. If there is nitrate in the water, this is determined by the absorption of UV light at 212 nm. 

In addition, the sensor measures absorption at 254 nm and 360 nm to test the impact of organic matter and turbidity. This makes the sensor insensitive to cross-influences in the water. In order to prevent incorrect measurements due to other turbid materials such as sand or clay, this area is recorded separately with a second detector, then calculated. This helps to accurately check the sources in terms of legal requirements or to monitor the necessary preparation steps if water is already contaminated.

A smart Bürkert system solution: water blending

Water Blending Bürkert

As well as measurement, we at Bürkert also focus on the controlling and monitoring of fluids. Solutions are therefore used to help mix up water of differing qualities. For example, if there is a source with a high nitrate concentration, our solution for water blending enables dilution with sources that demonstrate a low nitrate concentration. This is usually cheaper than treating the highly contaminated source. 

The worsening of water quality is unfortunately a rather unedifying trend that cannot be stopped – the challenges facing water suppliers will become increasingly stringent. This is why we are focusing on providing our customers support in this area so the quality of drinking water can be ensured in the future, protecting our most important foodstuff.