Water supplies meeting treatment requirements

Water Treatment & Nitrate


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Lake Superior


• Nitrate contamination is largely caused by fertilizer or manure sources and can cause adverse human health effects
• The maximum contaminant level for nitrate in public drinking water supplies is 10 mg/L for both the U.S. and Canada
• Approved methods of treatment for nitrate include ion exchange, reverse osmosis, and electrodialysis

Where does it come from?

Nitrate, a naturally formed compound of nitrogen and oxygen or ozone, can contaminate drinking water and cause adverse human health effects.[1] Nitrate levels in drinking water are largely due to contamination from chemical fertilizer, manure, or human waste.[2] Sources of contamination include septic tanks, animal feedlots, fertilizer inputs, or industrial waste.[3] Nitrate contamination is exacerbated in drinking water sourced from shallow groundwater or shallow wells near agricultural areas. [2,3,4] Nitrate concentrations are likely to increase with rain intensification and changes in land use practice such as tilling and chemical fertilizer use. [2,5]

How is it treated to meet applicable standards?

The maximum contaminant level (MCL) for nitrate in public drinking water supplies is 10 mg/L for both the U.S. and Canada[2,9] The EPA-approved methods of treatment for nitrate include ion exchange, reverse osmosis, and electrodialysis.[3,6] Boiling, mechanical filters, and chemical disinfection are not effective to treat drinking water for nitrate, meaning well users are mainly reliant on reverse osmosis or ion exchange.[3]

Reverse osmosis, where pressurized water is treated through a semi-permeable membrane, costs between 5-10 cents per gallon and is mainly used for household drinking or residential cooking water.[6] However, the American Water Works Association considers reverse osmosis an effective nitrate removal process for polluted agricultural groundwater supplies.[11] Electrodialysis, or the process of drawing nitrate ions through a membrane into brine waste water with electrical currents, remains costly, and complicated.[6]

Ion exchange is the process of removing nitrate from pressurized water moving through columns packed with an exchange resin. The resins can only be recharged at special facilities, making ion exchange an expensive option best used for treating large amounts of water. [6,7] Initial ion exchange unit costs range from $400 and $1,500[6], and larger facilities can cost upwards of millions of dollars.[8] Some large municipal facilities will use a combination of ion exchange and blending with nitrate-free water to remain below the Safe Drinking Water Standard. However, this requires sources of noncontaminated water, so other facilities utilize reverse osmosis, distillation10, or ion exchange in their process.[7]



  1. Zaveri, E., Russ, J., Desbureaux, S., Damania, R., Rodella, A.-S., & Ribeiro, G. (2020). The Nitrogen Legacy: The Long-Term Effects of Water Pollution on Human Capital. In The Nitrogen Legacy: The Long-Term Effects of Water Pollution on Human Capital. https://doi.org/10.1596/1813-9450-9143
  2. Ward, M. H., Jones, R. R., Brender, J. D., de Kok, T. M., Weyer, P. J., Nolan, B. T., Villanueva, C. M., & van Breda, S. G. (2018). Drinking water nitrate and human health: An updated review. In International Journal of Environmental Research and Public Health (Vol. 15, Issue 7). https://doi.org/10.3390/ijerph15071557
  3. Centers for Disease Control and Prevention. Nitrate and Drinking Water from Private Wells. Available online : https://www.cdc.gov/healthywater/drinking/private/wells/disease/nitrate.html (accessed 3 May 2021).
  4. Davidson, E. A., David, M. B., Galloway, J. N., Goodale, C. L., Haeuber, R., Harrison, J. A., Howarth, R. W., Jaynes, D. B., Lowrance, R. R., Thomas Nolan, B., Peel, J. L., Pinder, R. W., Porter, E., Snyder, C. S., Townsend, A. R., & Ward, M. H. (2011). Excess nitrogen in the U.S. environment: Trends, risks, and solutions. Issues in Ecology, 15.
  5. Hess, L. J. T., Hinckley, E. L. S., Robertson, G. P., & Matson, P. A. (2020). Rainfall intensification increases nitrate leaching from tilled but not no-till cropping systems in the U.S. Midwest. Agriculture, Ecosystems and Environment, 290. https://doi.org/10.1016/j.agee.2019.106747
  6. Dozier, M. C., Melton, R. H., Hare, M. F., Hopkins, J., Lesikar, B. J., Drinking Water Problems: Nitrates. Available online: https://agrilifeextension.tamu.edu/library/water/drinking-water-problems-nitrates/#:~:text=%20How%20is%20nitrate%20removed%20from%20drinking%20water%3F,water%20without%20wasting%20water.%20In%20the…%20More%20 (accessed on 3 May 2021).
  7. Des Moines Water Works, Treatment Process. Available online: https://dmww.com/water_quality/treatment_process.php (accessed on 3 May 2021).
  8. Vock, D.C. Iowa Farmers Won a Water Pollution Lawsuit, But at What Cost? Available online: http://www.governing.com/topics/transportation-infrastructure/gov-des-moines-water-utility-lawsuit-farmers.html (accessed on 3 May 2021).
  9. Government of Canada, Guidelines for Canadian Drinking Water Quality – Summary Table (2020). Accessible online: https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/water-quality/guidelines-canadian-drinking-water-quality-summary-table.html
  10.  Water Research Center, Nitrates and Nitrites in Drinking Water and Surfacewaters (2021). Accessible online: https://www.water-research.net/nitrate.htm#:~:text=Sources%20of%20Nitrate%20in%20Drinking%20Water%20Nitrogen%20is,convert%20various%20forms%20of%20nitrogen%20to%20nitrate%2C%20a
  11. AWWA MANUAL M46 REVERSE OSMOSIS AND NANOFILTRATION, SECOND EDITION (2007). Accessible online: https://www.awwa.org/Portals/0/files/publications/documents/M46LookInside.pdf