Nitrates are often found in drinking water sources, especially in smaller public water supplies and private water wells. EPA has established the Maximum Contaminant Level (MCL) for nitrate, measured as nitrogen (N), at 10 mg/l, to help monitor at a level considered safe for consumption (nitrite, measured as N, has an MCL of 1 mg/l).
Although nitrates and nitrites may still contaminate consumers’ drinking water supplies after they have been municipally treated, domestic wells are at a higher risk of contamination as they are not federally regulated to monitor nitrate levels. Water dealers must educate their customers the right way and adequately understand certification criteria and system performance.
High levels of nitrate contamination can lead to such health concerns as “blue baby syndrome,” or infant methemoglobiemia. However, the greatest risks to infants from nitrate exposure occur when both microbial contaminants and nitrate are present in water.
Pionetics Corporation Vice President H. Martin Jessen explains that methemoglobin impairs the delivery of oxygen in the blood to tissues in the body and can cause headaches, dizziness, irritability and blue tones to the skin in adults.
Where is nitrate most prevalent?
Nitrates and nitrites are most often found in groundwater. Nitrate, which comes from nitrogen, can pass through the soil and potentially contaminate groundwater. Additionally, as notes Jessen, airborne nitrogen compounds given off by industry and automobiles are deposited on the land in precipitation and dry particles. “Nitrate can be present in groundwater for decades and accumulate to high levels as more nitrogen is applied to the land surface every year,” he says.
A national map, found at http://water.usgs.gov/nawqa/nutrients/pubs/est_v36_no10/est_v36_no10.html, shows the likelihood of nitrate contamination of shallow groundwater. “Mapped probabilities reflect regional patterns of nitrate sources and aquifer-susceptibility characteristics. High probabilities are most extensive in the High Plains, which can have high nitrate fertilizer loading and well-drained soils overlying unconsolidated, coarse-grained deposits.
“The areas yielding the highest probability of contamination are in the Midwest, Texas, the Pacific Northwest and California. The U.S. Environmental Protection Agency has estimated that across the nation as many as 52 percent of community water wells and 57 percent of domestic water wells are contaminated by a measureable amount of nitrates and nitrites. In some of California’s fastest growing regions, such as Los Angeles and the San Joaquin Valley, one in every three domestic wells has nitrate contamination in levels that far exceed public health limits,” says Jessen, adding that this has led to strict standards requiring municipal water systems to be responsive to the need for increased testing and treatment.
Research shows that the majority of high nitrate levels are in rural areas affecting smaller communities and individual well owners. According to Jessen, this trend should be no surprise given that the number one source of nitrate contamination has been agricultural activity.
“These smaller communities often lack the financial resources to plan, build and operate a centralized nitrate reduction facility,” asserts Jessen. “They often rely on federal and state grants for financial assistance but even securing funding from these sources is beyond their reach. And, of course, individual well owners have to take on the full burden of ‘solving their own problem.’”
Available water treatment solutions
Various point-of-use (POU) and point-of-entry (POE) technologies are available that can treat nitrate contamination. Jessen names a few, including disposable ion exchange cartridges, reverse osmosis (RO) systems and electrochemical de-ionizers. “There are many RO systems and cartridges on the certified product list. To date only one electrochemical de-ionization technology has been certified.” Organizations such as the WQA and NSF certify these products.
While RO has been a popular treatment option in the industry for many years, Jessen advises dealers to fully understand how the technology works when it comes to treating nitrates. “The problem for the water treatment industry is that the widely used RO technology is unable to reliably reduce nitrates to the MCL if the feedwater contains more than 50 ppm nitrate concentration,” he says, noting that other treatment technologies, such as ion exchange and electrochemical de-ionization, are more effective at nitrate reduction at all concentration levels because you are able to increase cartridge size or contact time. It is also possible to increase the effectiveness of an RO to reduce nitrates by adding an ion exchange polisher to the unit.
The bottom line: The most effective technology for reducing nitrates from water depends on the nitrate concentration. However, dealers must know the technologies’ abilities and limitations or be at risk.
Challenges in certification
According to Jessen, there is a level of miscommunication when it comes to understanding how the different technologies and products are certified as compared to how they perform in real-world applications. In fact, he believes the issue is so significant that dealers may be liable in a potential lawsuit for misinforming customers regarding health contaminant reduction applications.
“Certification testing is done under the NSF/ANSI certification protocol that calls for the challenge water to include nitrate levels of 30 parts per million (ppm). The different systems are evaluated and the results reported as percent reduction,” he explains. This means if the nitrate contamination level is 100 ppm and the product is certified for 80 percent reduction the product water will not meet the 10 ppm MCL required to be in compliance.
Several prominent organizations, such as WQA, continues Jessen, promote POE and POU as an immediate solution to provide nitrate reduction for these small communities and well owners. “The certification testing protocol does not provide an accurate picture of which products will be effective at these higher levels. This results in misinformation to consumers and government regulators who are responsible for compliance to the MCL.”
While reducing nitrates does offer a significant opportunity, dealers must make sure the technology they are installing is capable of reducing higher concentrations below the MCL without fail. As Jessen concludes, “This market is a ‘public health’ market and requires absolute reliability, notification of consumers when maintenance is needed and must also generally meet the ‘reasonable’ test in terms of water waste — quantity and proper disposal, solid waste management, energy consumption, etc.”