By Rick Andrew

Nitrate contamination can be an issue for water supplies impacted by agricultural activities. Flooding after heavy rains and runoff can cause elevated nitrate concentrations in surface waters and nitrate can seep into groundwater as well. For example, the city of Columbus, OH had a drinking water advisory for two weeks in June due to high nitrate levels in certain parts of the distribution system, caused by heavy rains and agricultural runoff into area rivers serving as a source for the drinking water supply.

Health effects associated with nitrate contamination in drinking water are most severe for the very young. Infants under six months old exposed to nitrate in drinking water can potentially develop blue baby syndrome, or methemoglobinemia, which results in a blue discoloration due to decreased oxygen-carrying capacity of hemoglobin. In severe cases death can occur.

In 2013, the NSF Joint Committee on Drinking Water Treatment Units was approached by The Community Water Center and Clean Water Action, two non-profit groups focused on improving access to clean and safe drinking water. They shared concerns regarding high levels of nitrate contamination that were being detected in many agricultural regions in California, such as the Tulare Lake Basin and Salinas Valley. According to the research cited by these groups, in the highest agricultural-production regions of California (specifically at these locations) 2.6 million people depend on groundwater for drinking water. In these regions, however, there is very high nitrate contamination in the groundwater, primarily because of agricultural application of synthetic fertilizer and animal manure.1 The non-profit groups asked the Joint Committee to consider developing requirements for a nitrate reduction claim under NSF/ANSI 58 Reverse Osmosis Drinking Water Treatment Systems for POU RO systems intended to be used to treat water contaminated with high concentrations of nitrate.

Standards development process in motion
Initial discussion was held by a task group that included participants from the manufacturing, regulatory and non-profit sectors. The group reviewed information regarding nitrate concentrations that was available at the time and discussed the technological feasibility for POU RO systems to perform effectively on water supplies potentially contaminated with these concentrations of nitrate. The group decided that technically this could be feasible and they also decided to collect additional data to best evaluate the concentrations of nitrate being detected in drinking water supplies in the California agricultural areas.

Additional data was collected and shared prior to the 2014 Joint Committee meeting, where additional discussion on the subject occurred. Ultimately, the task group developed a protocol essentially based on the existing nitrate/nitrite reduction test method in NSF/ANSI 58, but using higher concentrations of nitrate/nitrite based on an analysis of the nitrate concentration data that had been reviewed. The logic behind establishing the nitrate concentration to be used for this test was to set it at the 95th percentile of concentrations being detected in drinking water, which is consistent with the logic behind the contaminant reduction requirements for all of the health claims in NSF/ANSI 53, 58 and 62.

The task group established draft requirements. Several laboratories conducted validation testing according to the draft requirements and the results of the validation testing were reviewed and discussed by the task group. Ultimately, the task group recommended the draft requirements be adopted into NSF/ANSI 58 by the joint committee. This process has now been completed and the next edition of NSF/ANSI 58, which is expected to publish in the next few months, will include these new requirements.

Key points of the new requirements
There are several important points to consider that frame the new requirements:

  • Nitrate and nitrite reduction claims are tied together under NSF/ANSI 58, because the two exist in equilibrium when present in drinking water. The maximum permissible product-water concentration is a combination of the two, based on the US EPA MCL for nitrate and nitrite. Although the new requirements are based primarily on issues with nitrate, nitrite is also required to be included in the test challenge water.
  • The existing requirements for nitrate/nitrite reduction were not removed from NSF/ANSI 58. Claims based on these existing requirements may still being made. It is possible to make claims either on the existing requirements or the new requirements.
  • Manufacturers must be clear about which claim, if either, is being made. This is done by describing the challenge concentrations in several places in the product literature.
  • If systems with claims under the new requirements include booster pumps to assure sufficiently high net driving pressure, then clarifying statements indicating that a booster pump is necessary are required in the product literature.
    V57_N11_Water Matters Figure 1Figure 1 summarizes the requirements for the existing nitrate/nitrite reduction claim, as well as the new high-nitrate reduction claim. Figure 2 includes the verbiage required in the installation, operation and maintenance instructions and on the performance data sheet if the system includes a booster pump.

V57_N11_Water Matters Figure 2A process to help provide solutions
Once the standard publishes, it will be available for certification to help provide relief for those consumers in areas affected by high levels of nitrate contamination. The consensus standards development process used to introduce new requirements to the NSF/ANSI Drinking Water Treatment Units standards provides a vehicle to enact positive changes. These changes can reflect new problems that have been identified with drinking water supplies, or to reflect a better understanding of existing problems based on newer studies or data. In any case, groups or individuals can share their concerns and information with the NSF Joint Committee on Drinking Water Treatment Units and utilize an organized, scientific approach to help establish and implement real solutions.


  1. Thomas Harter et al., Addressing Nitrate in California’s Drinking Water, UC Davis, March 2012.

Andrew_Rick_mugAbout the author
Rick Andrew is NSF’s Director of Global Business Development–Water Systems. Previously, he served as General Manager of NSF’s Drinking Water Treatment Units (POU/POE), ERS (Protocols) and Biosafety Cabinetry Programs. Andrew has a Bachelor’s Degree in chemistry and an MBA from the University of Michigan. He can be reached at (800) NSF-MARK or email: [email protected]


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