How to filter nitrates out of drinking water

Written by sarah metzker erdemir
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How to filter nitrates out of drinking water
Nitrates in the water supply can be dangerous. (Waterfall image courtesy of

While plants need nitrogen to grow, chemical fertilisers often provide more than the plants can use, and the excess nitrates can enter a well through the groundwater. Unlike chlorine, nitrates in your drinking water are tasteless and odourless, but they are potentially lethal to human babies, horses, young ruminant animals (sheep and cattle), and young pigs and chickens, because the nitrates in the water interfere with the babies' and animals' ability to absorb oxygen. That's why it's very important to keep your drinking water free of nitrates.

Skill level:

Things you need

  • Home water distiller
  • Reverse osmosis filter
  • Ion exchange filter
  • Bottled water

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  1. 1

    Use a home distillation system to filter nitrates out of drinking water. Distillers boil the water and collect the steam, which is safe to drink because nitrates and mineral contaminates stay in the boiling tank.

  2. 2

    Run tap water through a reverse osmosis filter. These filters use high pressure to force the water through a thin polyimide membrane, which collects and blocks the contaminated water and releases clean water.

  3. 3

    Remove nitrates with an ion exchange filter. Ion exchange filters are the most efficient, because they don't use much energy and they don't produce toxic waste water, unlike distillers and reverse osmosis systems. Ion exchange filters work by adsorption, a chemical process in which nitrate ions adhere to beads of resin that have been charged with chloride. The nitrate ions are exchanged for the chloride ions.

  4. 4

    Dilute the water. A small amount of nitrates is not toxic, so it's possible to dilute the water with bottled drinking water to reduce the amount of nitrates present.

Tips and warnings

  • Prevent nitrates from entering your groundwater by replacing chemical fertilisers with cow or chicken manure, and encourage neighbours to do the same. These manures naturally contain sufficient nitrates to support good plant growth, and there is less risk of excess nitrates running into your well water.
  • Because you can't taste or smell nitrates, the only way to detect them is through chemical testing. The water should be tested at different times of year, as the nitrate levels can vary, and it's especially important to test water in the late spring when fertiliser runoff from your farm or neighbouring farms is most likely to be present. Your health department or extension service can advise you on water testing, safe well placement and proper encasing of wells.
  • If you use distillation or a reverse osmosis system to remove nitrates, it is important to dispose of the waste water properly to prevent the nitrates from re-entering the groundwater. Do not dump waste down the drain or in the ground near wells.

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