How did nitrate contaminate the groundwater?
Wastewater is water discharged from our home (sewer or septic tank), agriculture (farms and dairies), industries (such as food processing), or cities (public sewer system), and from surface or stormwater runoff. This wastewater carries contaminants (nitrate, pesticides, heavy metals, and organisms) that can be released into a river, a lake, or the soil where it seeps or moves slowly into the groundwater below the ground. At high enough concentrations, the contaminants can make groundwater supplies unusable for drinking water and, in some cases, for agricultural use.
In localized areas, nitrate is a major cause of unsafe drinking water. Nitrate seeps slowly into the groundwater from fertilizers or after being discharged as wastewater from animal feedlots, industrial facilities, municipal wastewater treatment plants, or leaky septic systems. For example, when fertilizer containing nitrate is applied to crops, not all nutrients in the fertilizer are absorbed by the plants. The excess nutrients then seep into groundwater supplies as nitrate.
Drinking water with high levels of nitrate can createhuman health risks, especially for infants and pregnant women. Because nitrate levels have been increasing in groundwater over the last few decades, some drinking water supplies are unhealthy and do not meet State drinking water standards.