Nitrates like phosphorous are a vital component for all living things. In animals, they form part of protein and DNA found in cells, they get nitrogen from eating plants and other animals. Plants also require nitrogen to live and grow, the get there nitrogen by absorbing it from water and soil.
Nitrate are naturally occurring, all aquatic organisms create waste and aquatic plants and organisms eventually die. This creates ammonia, bacteria in the water changes this ammonia to produce nitrite which is then converted by other bacteria to nitrate. Nitrates (NO3-) are formed by combining oxygen and nitrogen. Nitrates also come from the earth. Soil contains organic matter, which contains nitrogen compounds. Just like the ammonia in water, these nitrogen compounds in the soil are converted by bacteria into nitrates.
Excessive nitrate levels found in water course could come from human intervention. Agriculture is a high source of nitrate due to it being applied to crops to encourage plant growth. In addition, sewage treatment works and domestic application can also be a source of nitrates. Just like phosphorus, nitrates can run-off the surface during high rainfall and flood events, entering water course. Like phosphorous, nitrates can also lead to eutrophication and enrichment of water course. In addition, nitrates can also have adverse effects on human life. Nitrates can interfere with the ability of our red blood cells to carry oxygen and in infants are more at risk of nitrate poisoning than older children or adults. Therefore it is important to reduce nitrate levels in water course so that it is safe to drink.