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Nitrates in water

Nitrāti ūdenī

The presence of nitrates in fruits and vegetables is a widely discussed topic today but the question about their presence in the water is less frequently topic. Although nitrates and nitrites in the water at normal level are not harmful, however, the water with a high concentration of these substances is harmful. They create an insufficient supply of oxygen to human tissues, negatively affects the functioning of the nervous system, causes problems with the gastrointestinal tract and other problems.

In this week’s article we will talk about what are nitrates and nitrites, how do they get into the water, why are they dangerous and what solutions are suitable for water purification from nitrates?

What are nitrates, nitrites and how do they get into water?

Nitrates and nitrites are naturally occurring chemicals that have similar structures. They are both composed of nitrogen and oxygen, but nitrates contain three oxygen atoms while nitrites contain two oxygen atoms.

Nitrates and nitrites are found in the soil as well as in surface and underground water. They are related to both natural nitrogen cycle processes in nature and man-made impacts.

The natural release of nitrates into the water occurs with microorganisms, when  proteins of animal and plant origin breaking down (ammonium compounds are oxidized to nitrites and nitrates when exposed to air). Usually the content of such pollutants is low and does not significantly affect the water condition. Man-made influences (fertilizers, industrial effluents) are the main reason nitrates end up in the water. Agricultural fertilizers dissolve well in the water and pollute surface waters, while gases produced by industrial enterprises interact with the water and oxygen to form nitric acid (“acid rain”). When nitric acid reacts with minerals, nitrates are formed which end up in water bodies.

As for nitrites, they characterize the microbiological contamination of water with sewage. Usually their increased concentration can be observed in waters located near cattle grazing fields.

Why are nitrates in water dangerous?

An increased concentration of nitrates in the human body forms methemoglobin. Nitrate ions oxidize the hemoglobin in erythrocytes and interfere with the transport of oxygen to human tissues, thereby affecting the functioning of the nervous system and enzyme synthesis.

For a healthy person the level of methemoglobin is usually no more than 3-4%. When its content increases to 10%, adults and children experience cyanosis (blue color of the skin) caused by insufficient saturation of tissues with oxygen (hypoxemia). When the level of methemoglobin reaches 20-50%, pronounced cyanosis, headache, shortness of breath, weakness, tachycardia, dizziness and loss of consciousness are observed in the body. For children the symptoms are more pronounced, they are especially dangerous in the first six months of life. With 25-40% and higher levels of methemoglobin in the blood children have a high risk of mortality. Most infant deaths have been recorded when water containing 70-250 mg/l nitrate was used for drinking and formula making. Such water is often found in well water.

Nitrates and nitrites also can cause gastrointestinal problems as well as affect fetal development. Therefore, it is dangerous for mothers during pregnancy to drink water with a high nitrate content.

How much nitrates are in water?

The maximum permissible nitrate concentration in the drinking water is 50 mg/dm³, while the permissible nitrite concentration is 0.5 mg/dm³. These are values that will not cause adverse effects in the body and will not affect the offspring.

Water from wells and surface sources often contains nitrate concentrations that exceed permissible limit values. About half of the wells have elevated nitrate levels. In tap water nitrates usually meet the standards, while the water from deep wells (artesian) is the safest in terms of nitrate contamination.

Increased attention should be paid to areas used for growing crops in the summer. It is also useful to know that water contaminated with nitrates has a very pleasant taste and they do not determine the taste characteristics of the water.

Water purification from nitrates

The two main methods of water purification from nitrates are:

  • reverse osmosis;
  • ion exchange.

The reverse osmosis filter membrane contains pores in size of 0.001 – 0.0001 micron. Thanks to them the membrane is able to retain up to 99.8% of impurities, including nitrates and nitrites. The Ecosoft product range includes both large equipment used in the production of drinking water and food as well as systems for domestic use. You can get acquainted with the detailed assortment of products on our website (see the following links A, B and C).

The principle of ion exchange is based on the properties of synthetic polymer resins. The principle of ion exchange is based on the properties of synthetic polymer resins. Ion exchange filters provide anion exchange in water (nitrates, chlorides, sulfates, etc.) for hydroxide ions OH-. Such water filters, which contain ion exchange resins or their mixtures, are called complex purification systems.

Conclusions

Despite the fact that the permissible concentration of nitrates is quite high, nitrate content in water of 20 mg/l and more for children (especially in the first six months of life) can be even life-threatening. In order to reduce the risk of nitrate poisoning, it is not recommended to consume well water without prior treatment and it is necessary to monitor water sources regularly .

Read also: The water for children.

 

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