Automatically Regenerable Point of Entry Nitrate Reduction System

Nitrate levels, in all water worldwide, are rising due to the use of inorganic fertilizers. Nitrate concentrations are also rising in ground water in the United States, especially in the farming states. This is of great concern because private, self-supplied drinking water systems, which primarily draw from ground water, are not federally regulated. It is the responsibility of well owners to test and treat their well water for nitrates and other pollutants.

Roughly 20 percent of the U.S. population has wells as a main source of drinking water.¹ While nitrate does occur naturally, concentrations exceeding 3 mg/L are generally indicative of manmade pollution. Since 1962, the U.S. Environmental Protection Agency (EPA) has set an enforceable standard, called maximum contaminant level (MCL), for nitrate in drinking water at 10mg/L (ppm). This regulatory limit for nitrate was set to protect against infant Methemoglobinemia, a disease of the blood where the red blood cells have diminished capacity to carry oxygen to the body. However, the adverse health effects of Nitrate appear at much lower concentrations as well. These include colorectal cancer, bladder and breast cancer, and thyroid disease. Some of these harmful effects start at drinking water concentration at 5 mg/L. Risk of specific cancer and birth defects may be increased when nitrates are ingested under conditions that increase the formation of N-nitroso compounds. Several well-regarded epidemiological studies have linked above mentioned cancer and health effects at levels less than one-tenth of the legal limit.

Earlier this year, the EPA suspended plans to reevaluate its outdated nitrate standard. Approximately, 6.5 percent of the U.S. ground water contains nitrate concentrations greater than 5 mg/L. The EPA has found over 1,000 public wells in violation of the current MCL standard. A 2006 United States Geological Survey (USGS) study suggests that more than 1 million private wells are located in areas where the ground water is at risk of being above the current MCL for nitrate.

Recently (2021), Environmental Working Group published a peer-reviewed analysis of the health and economic impacts of this widespread nitrate contamination from agriculture.² They estimated that nitrate contamination could cause 12,500 cases of cancer each year, and treating those cases could cost up to $1.5 billion a year.³

Needless to say, there is an urgent need to develop convenient and effective nitrate removal filter systems that address the problems described above.

Need for a Certification Standard for Automatically Regenerable POE Nitrate Removal Systems

Large scale, regenerable municipal systems for removing nitrate by synthetic anion exchange are known; however, self-generating point of entry (POE) systems to reduce nitrate using anion exchange for residential and commercial systems are not currently available. These present two problems, described below, that were not addressed by any of the currently available standards. Hence, an ASSE Listing Evaluation Criteria (LEC) Working Group was created and chaired by me. This group developed a protocol that addressed the following new criteria for testing and certifying the automatic regenerable POE nitrate removal system, using NSF/ANSI 53 (Drinking Water Treatment Units – Health Effects) for reduction requirements (30 mg/L influent to be reduced to less than 10 mg/L), but still utilizing the currently available architecture of a regenerable contaminant reduction system:

1. Nitrate Dumping:
   Depending on the quality of influent water, anion exchange systems — if not regenerated correctly — can dump or increase the amount of nitrate in the drinking water if anion, such as sulfate, are exchanged by the resin. Thus, the ASSE LEC document must have a rigorous test to show that the system in question does not release nitrate when challenged by high enough sulfate concentration after the anion exchange system is exhausted. The test called for the concentration of the sulfate in the test water of at least 250-265 mg/L, and after the exhaustion of the anion exchange resin required the effluent Nitrate concentration to be no more than 1 mg/L higher than the influent concentration. EPA has a Maximum Secondary Contaminant Level (SMCL) of 250 mg/L. EPA estimates, that at most, about 3 percent of the public water systems in the U.S. may have sulfate levels of 250 mg/L or greater.
   
2. No Untreated Nitrate Water Bypass:
   Currently, POE systems such as water softeners have electronic controllers that use a bypass valve during the regeneration of aesthetic contaminant, such as calcium hardness. This bypass valve allows the availability of hard water for consumption during the regeneration cycle. For non-health related contaminant regeneration, Section 3.5 of ASSE 1087 (Commercial and Food Service Water Treatment Equipment Utilizing Drinking Water) requires bypass flow to be at least 50% of the service flow and shall not be reduced to zero at any time during the regeneration, ensuring some availability of water. Bypass valves in current commercial systems are not very accurate and can be subject to failure. In the case of health effect contaminants, such as Nitrate, we cannot have any uncertainty regarding the untreated water during the regeneration cycle, and it must not be available for consumption. So, a reliable “No Untreated Nitrate Water Bypass Valve” that will completely shut off the flow of untreated water during the regeneration cycle is mandated. The new LEC document requires installation of such a valve (as seen in the cover photo of this article) and requires a test to show that the flow through the nitrate reduction system is completely stopped at the start of the regeneration cycle and does not resume until the six seconds into the fill phase of regeneration.

Creation of New ASSE LEC 2008 Standard for Regenerable Nitrate Removal System Using Anion Exchange

Incorporating the two above requirements of nitrate dumping and “No Untreated Nitrate Water Bypass,” ASSE LEC 2008, Listing Evaluation Criteria for Point of Entry Anion Exchange – Nitrate Reduction, was created. In addition, other standard tests, such as nitrate reduction capacity per NSF/ANSI 53, salt used for regeneration, nitrate dumping and automatic regeneration failure, service flow and flow capacity, backsiphonage, 24-hour pressure loss, pressure shock (water hammer), structural integrity, and cycle tests were also incorporated.

Automatically Regenerable Nitrate Reduction System

Companies, including Brita-Pro Corporation, have begun commercializing Automatically Regenerable Nitrate Reduction Point of Entry Systems Using a Nitrate Selective Anion Exchange Resin, taking advantage of the newly completed ASSE LEC 2008 document for certification. Some of the features they’re able to claim are:

1. Reduces Nitrate to EPA’s MCL limit of 10 mg/L, or lower if desired.
2. Features a microprocessor to automatically regenerate the anion exchange resin at exhaustion.
3. Performance third-party certified under ASSE LEC 2008.
4. The active anion exchange media is Nitrate selective and is not affected by sulfate ion concentration up to 265 mg/L.
5. Tested to show that there is no nitrate dumping on exhaustion when challenged with sulfate concentration of up to 265 mg/L.
6. Tested for the operation of microprocessor for automatic regeneration.
7. Stops the flow of untreated Nitrate water during the regeneration cycle lasting about 1.5 hours.
8. Customized to individual needs and household size and water consumption. Also allows for changes in concentration of Influent and Effluent Nitrate concentrations.
9. Certified for lead-free systems, material safety, structural integrity, flowrate, pressure loss, and service flow.
10. Has approximately 1,800-2,000-gallon capacity between the automatic regenerations for 1 cubic ft system.

There is an urgent need for a safe, reliable, convenient, and automatically regenerable POE systems to remove nitrate from well water. But there has not been a standard that includes special features necessary for a health effect pollutant, such as nitrate, until now. ASSE LEC 2008 has filled that void.

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Resources

1. https://www.epa.gov/nutrient-policy-data/estimated-nitrate-concentrations-groundwater-used-drinking
2. Mary H. Ward et.al. in Int. J. Res. Public Health 2018, 15,1557-Drinking Water Nitrate and Human Health: Updated Review
3. https://www.ewg.org/release/ewg-nitrate-pollution-us-tap-water-could-cause-12500-cancer-cases-each-year