Brian Barton
Nitrate pollution in drinking water is a pressing issue that has various human-made and natural sources. While low levels of nitrate in drinking water are natural and safe, high concentrations can be harmful to human health and the environment. This is particularly dangerous for infants, who are at risk of developing methemoglobinemia, or blue baby syndrome, which can be fatal. With the implementation of the Safe Drinking Water Act in 1974, monitoring data for public water supplies in the US has provided a framework to support exposure assessments. However, the sources of nitrate pollution in drinking water remain diverse, including fertilizer, septic systems, animal waste, sewage systems, and agricultural activities.
| Characteristics | Values |
|---|---|
| Natural Sources | Plant decay, lightning, spinach, carrots |
| Human-made Sources | Fertilizers, sewage systems, animal waste, septic systems, landfills, animal feedlots, urban drainage |
| Health Effects | Methemoglobinemia (blue baby syndrome), thyroid problems, adverse pregnancy outcomes, cancers (colorectal) |
| Regulatory Standards | EPA standard: 10 mg/L nitrate, EU Nitrates Directive |
| Vulnerable Wells | Shallow wells, wells in sand, karst, fractured rock aquifers, dug wells with non-watertight casings |
| Prevention | Keep nitrate sources away from well, construct well in a safe spot, regular well inspection |
| Treatment | Alternative water sources (e.g. bottled water), avoid for infants under six months, do not boil nitrate-contaminated water |
Fertilizer
Nitrogen is a crucial nutrient that helps plants and crops grow, but high concentrations are harmful to people and nature. Nitrate pollution of ground and surface water bodies is generally linked with continually increasing global fertilizer nitrogen (N) use. Since the 1920s, humans have doubled the natural rate at which nitrogen is deposited onto the land through the production and application of nitrogen fertilizers. The major anthropogenic source of nitrogen in the environment is nitrogen fertilizer, the application of which increased exponentially after the development of the Haber-Bosch process in the 1920s. Most synthetic fertilizer applications to agricultural land occurred after 1980. Since approximately half of all applied nitrogen drains from agricultural fields to contaminate surface and groundwater, nitrate concentrations in our water resources have also increased.
In areas such as intensive feedlots, livestock waste constitutes a potent source of excess nutrients flowing into the environment. Rainfall or irrigation combined with excessive fertilizer N use in wheat, corn, and cotton resulted in high groundwater nitrate-N in agro-ecosystems. Due to relatively high nitrate-N levels in shallow wells located in agroecosystems, farmers were advised to drill deep drinking water wells to reduce the risk of nitrate pollution.
It is important to note that nitrate pollution in drinking water can have significant health impacts, especially on infants. Consuming too much nitrate can affect how blood carries oxygen and cause methemoglobinemia (also known as blue baby syndrome), which can result in serious illness or even death. Bottle-fed babies under six months old are at the highest risk of getting this illness.
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Septic systems
The impact of a septic system on local drinking water wells or surface water bodies depends on several factors, including its design, installation, maintenance, and proper usage. When a septic system fails, it can release untreated wastewater, which contains pathogens (e.g., E. coli), nutrients, and other harmful substances directly into the groundwater or onto the ground and into surface waters. This can result in contamination of surface waters and groundwater, with disease-causing pathogens and nitrates.
In some cases, the design of a septic system may require advanced treatment to reduce the impacts of nitrogen contamination or include disinfection when properties are close to surface waters. If the system is discharging directly into the groundwater without treating the wastewater, it can negatively impact water quality.
Wells located near septic systems are more vulnerable to nitrate contamination, especially if they are older wells (pre-1974), are in areas with agricultural activities, or have damaged or leaking casings or fittings. It is recommended that wells are constructed in safe spots away from potential nitrate sources and regularly inspected for damage.
To prevent and address nitrate contamination in well water, it is important to identify and remove potential sources of contamination, such as septic systems, and regularly test the water quality. Home water treatment systems can be considered, but it is still recommended that babies under six months old do not consume the treated water as a safety precaution.
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Animal waste
The use of fertilizers and animal waste decreases with an increase in altitude, as shown by regression analysis. The density of livestock, including cattle, sheep, pigs, and poultry, has been linked to higher nitrate concentrations in water. In the United Kingdom, an average annual increase of 0.7 mg/l has been observed in some rivers due to agricultural sources and livestock farming.
In the United States, the Environmental Protection Agency (EPA) has set a standard of 10 milligrams of nitrate per liter of drinking water (mg/L) to protect infants from methemoglobinemia, also known as blue baby syndrome. This condition can cause serious illness or even death, and infants under six months old are at the highest risk.
High levels of nitrate in drinking water, often above 10 mg/L, can be attributed to various sources, including animal feedlots, septic systems, and wastewater. Animal waste, when concentrated near the ground surface, can cause nitrate to seep into the groundwater, leading to contamination.
To prevent nitrate pollution in drinking water sources, it is crucial to keep nitrate sources, including animal waste, away from wells. Regular testing of well water is essential, especially if there is a possibility of contamination from nearby animal waste or agricultural activities.
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Sewage systems
Nitrate pollution from sewage systems can occur through several pathways. Firstly, sewage systems that are not properly maintained or treated can release high levels of nitrates into the environment. This is especially common in areas with outdated or overburdened wastewater treatment facilities, where the treatment process may not effectively remove nitrates before discharging the treated effluent.
Additionally, sewage systems that are not designed or operated correctly can contribute to nitrate pollution. For example, if sewage pipes are not adequately ventilated, it can create anaerobic conditions that promote the growth of nitrate-producing bacteria. Similarly, if sewage treatment processes are not optimized, they may not sufficiently remove nitrates, allowing them to persist in the treated water.
Moreover, sewage systems that are not regularly maintained and inspected can experience blockages, leaks, or breakdowns, which can result in the direct discharge of raw sewage into water bodies, leading to high nitrate levels. This is often observed in developing countries with inadequate sanitation infrastructure, but it can also occur in developed nations during heavy rainfall or when sewage systems become overwhelmed due to increased population or industrial activity.
Another critical aspect is the disposal of sewage sludge, also known as biosolids. When sewage sludge is not properly treated or managed, it can contain high levels of nitrates, which can then leach into groundwater or surface water sources. This is a significant concern, especially when sludge is applied to land as fertilizer, as the nitrates can then enter water bodies through runoff or infiltration.
To mitigate nitrate pollution from sewage systems, several measures can be implemented. Firstly, regular maintenance and upgrades of sewage infrastructure are essential, including pipes, treatment facilities, and disposal systems. Additionally, optimizing the treatment processes to ensure effective nitrate removal is crucial, utilizing advanced technologies such as catalytic reduction, which can achieve high nitrate conversion rates without generating additional waste.
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Agricultural activities
Agriculture is a major source of nitrate pollution in drinking water. Nitrogen-based fertilizers, animal manure, and human sewage are all concentrated near the ground surface, allowing nitrates to seep into groundwater and surface water sources. This is particularly true in agricultural areas, where nitrates from fertilized fields can run off into nearby water sources, contaminating drinking water supplies.
Since the 1920s, humans have doubled the natural rate at which nitrogen is deposited onto land through the production and application of nitrogen fertilizers. The development of the Haber-Bosch process in the 1920s led to an exponential increase in the application of synthetic fertilizers, with most applications occurring after 1980. As a result, almost half of all applied nitrogen drains from agricultural fields, contaminating surface and groundwater sources. This has caused nitrate concentrations in water resources to increase, with more than 80% of fertilizer used for agriculture, plants, and animal production being lost to the environment.
The use of low-cost, synthetic fertilizers is necessary to increase crop yields and meet the world's growing food demands. However, this has led to an excess of nitrogen in the environment, as more fertilizer is applied than crops can absorb. Nitrogen is water-soluble, so irrigation washes excess nitrates into the groundwater, leading to nitrate pollution in drinking water. This is a particular issue in the United States, where two-thirds of nitrogen pollution is caused by agricultural runoff.
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Frequently asked questions
The U.S. Environmental Protection Agency (EPA) standard for nitrate in drinking water is 10 milligrams of nitrate (measured as nitrogen) per liter of drinking water (mg/L).
Consuming too much nitrate can affect how blood carries oxygen and cause methemoglobinemia, also known as "blue baby syndrome". Bottle-fed babies under six months old are at the highest risk of getting this illness, which can result in serious illness or death.
Nitrate pollution in drinking water can come from natural sources as well as human activities. Natural sources include plant decay and lightning. Human activities that can cause nitrate pollution include the use of nitrogen fertilizers, combustion of fossil fuels, and agricultural runoff.
If you have a private well, it is important to regularly test your water for nitrate and other contaminants. If nitrate is detected, consider using an alternative source of drinking water, such as bottled water, especially for infants and young children. You can also treat your water with home water treatment systems, but it is recommended to consult with a professional before selecting and installing a treatment system.
In the United States, the Safe Drinking Water Act of 1974 provides a framework for monitoring public water supplies and protecting human health. In Europe, the EU Nitrates Directive aims to prevent nitrate pollution from agricultural sources and promote good farming practices.
