Online nitrate measurement on groundwater for optimizing drinking water production

NT200 - groundwater nitrate control for drinking water suplply

This is the first article of our application notes series.

Today’s application describes how DTLI’s nitrate analyzer NT200 can be used to safely supply drinking water from groundwater, preventing potential nitrate pollution to affect the final water quality. This application was developed for the operating company of an international airport.

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An autonomous and valuable installation

Fast Return on Investment
Low operation costs
Low maintenance need
Long-time product lifecycle

To ensure the drinking water supply of the airport, the managing company has 2 potential water inputs :

The cheap one : they can use groundwater directly from the local aquifer
The expensive option : they can buy water from the public drinking water network.

The local groundwater can be easily treated to meet sanitary standards for water potabilization, except for nitrate concentration which can be problematic in that region.
Nitrogen fertilizers are applied extensively in agriculture to increase crop production, but excess nitrogen supplies can cause water pollution. Degradation of groundwater quality is then one of the damaging impacts of agricultural overapplication of nitrogen fertilizers. Continuous nitrate monitoring can prevent from delivering contaminated water to the population.
To respect the legal limit of 50 mg/L and avoid nitrate contamination of drinking water supply, which can pose immediate risks to human health, the supplier actually dilutes water from the aquifer with water they buy from the public network.

Degradation of groundwater quality is then one of the damaging impacts of agricultural overapplication of nitrogen fertilizers. Continuous nitrate monitoring can prevent from delivering contaminated water to the population.

Thus the operating company needs to automatize the mixing of the two water inputs in order to:

Respect the legal nitrate limit for the supplied water
Optimize the costs of the Drinking water supply

Here is Datalink Instruments solution :

We installed a NT200 nitrate analyzer to control the water supply mix. Thanks to its multiplexing option the NT200 performs direct measurement of nitrate concentration successively on the aquifer water input, on the water network input, and after the mixing point, at a frequency of 1h.
On a 4th channel the user defined an equation in function of the nitrate concentration on the 3 measurement points. Based on this channel, the analogic 4-20 mA output controls the water mix in an autonomous way.
In case the concentration on the mixed water exceeds the defined limit, the analyzer activates a threshold relay to alert the operational manager.
That way, the system automatically regulates the nitrate concentration below the 50 mg/L limit, using as much groundwater as possible, and completing with what it takes of public network water.