For several decades, nutrient pollution has harmed numerous streams, rivers, lakes, bays, and coastal waterways, causing major environmental and human health consequences as well as economic effects. When there is too much nitrogen and phosphorus in the water, algae grows faster than ecosystems can cope. The algae die and sink to the bottom of the lake or stream, where they decompose and release carbon dioxide into the atmosphere and hydrogen sulfide into the water. The by-products of this process cause a stench that attracts birds which eat the algae but also spread their toxic substances throughout the ecosystem.
The problems caused by excessive nutrients are not limited to lakes and streams though. Overloading of ponds and marine areas with nutrients causes the same types of problems, only on a larger scale. The more abundant organisms will be algae instead of plants because they use up all available nutrients faster than those species dependent on them. This will decrease the amount of food available for other organisms so that they start to suffer from malnutrition. Finally, some organisms will be completely excluded from the polluted area because they cannot tolerate these high concentrations of chemicals.
In conclusion, excessive nutrients can have harmful effects on the environment due to algal blooms that consume large amounts of oxygen and cause fish kills. Fish with higher metabolism rates such as salmon are particularly sensitive to changes in oxygen levels so they would be the ones most affected by an algal bloom.
Significant increases in algae wreak havoc on water quality, food resources, and habitats, as well as the oxygen required by fish and other aquatic life. Algae also produces toxins that can harm humans if they are ingested.
The most common method of removing nutrients from wastewater is through biological treatment processes. In this process, bacteria break down some pollutants (such as ammonia), while others are removed by sedimentation or filtration. Biological treatment processes are effective at reducing nutrients but cannot remove all contaminants with ease. For example, bacterial treatment processes will not remove heavy metals or synthetic chemicals from water.
In addition to biological treatment processes, several technologies have been developed to reduce the level of nutrients in wastewater before it is released into natural waterways. These include physical methods such as grit removal and chemical methods such as nitrification/denitrification. Grit removal uses large quantities of energy to sift out small particles from wastewater before it enters a treatment plant. This practice reduces the amount of debris entering treatment facilities and makes cleaning them easier. Chemical methods are used to treat wastewater after it has entered a treatment facility. Commonly used chemicals include chlorine to disinfect the water and ammonia for nitrogen removal.
Ammonia is the product formed when nitrogen compounds are broken down by bacteria.
Nutrient contamination occurs when too many nutrients, primarily nitrogen and phosphorus, are supplied to bodies of water and function as fertilizer, creating excessive algal development. Excess nutrients can cause more significant issues, such as inadequate quantities of oxygen dissolved in the water. The amount of nutrients in fertilizers has increased dramatically over time, so there is now a greater potential for excess nutrients to enter our waterways.
Excessive nutrients can also be introduced into waterways through sewage discharge. The EPA estimates that 31% of the nitrogen and 18% of the phosphorus entering our waters comes from municipal sources. The other source of contamination is agricultural runoff - 79% of farmers comply with some form of nutrient management policy, but even those that do not use excess nutrients and thus contribute to excessive loads.
Runoff contains nutrients that promote plant growth (such as nitrogen) and those that cause algae blooms (such as phosphorus). If the amount of nitrogen or phosphorus in runoff exceeds what a water body can handle, it will lead to excessive amounts of both nutrients in the water, which is called an "excessive nutrient load."
The most effective way to reduce the amount of nutrients in wastewater is to recycle treated water rather than sending it directly to streams or other bodies of water. Recycling reduces the amount of nitrogen and phosphorus entering treatment plants' facilities.
Fertilizers and manure from agricultural areas, as well as sewage and runoff from our cities, are rapidly making their way into rivers, poisoning them with an overabundance of nutrients. When there are too many nutrients in the water, they can fuel enormous algal blooms, particularly hazardous algae. These algae produce toxins that can be harmful to humans if they get into the water. Also, if you eat the algae, you could be eating enough phosphorus or nitrogen compounds to cause harm.
Another danger is that we're taking away the natural ability of soil to hold water. If it doesn't rain or seep into the ground, these fields need to be irrigated. This requires using even more energy than is used in traditional agriculture, since most irrigation needs are today met by electricity. Electricity comes from fossil fuels, so again, we're leaving a carbon "footprint" behind every time we eat a salad.
Finally, we're taking water from other parts of the world to grow our foods. Since agriculture accounts for about 40 percent of global greenhouse gas emissions, this has a huge impact on climate change.
The list goes on and on. The point is, we need to think carefully about how we use our resources, especially water. Water is vital to life; we must take care not to use it up too quickly.