causes of water pollution
Fertilizers / Nutrient Pollution
Many causes of pollution, including sewage, manure, and chemical fertilizers, contain"nutrients" such as nitrates and phosphates. Deposition of atmospheric nitrogen (from nitrogenoxides) also causes nutrient-type water pollution.
Chemical and Industrial Processes
Almost all bodies of water in the world have some level of pollution from chemicals andindustrial waste.Most hazardous liquid wastesolvents, heavy metals, and radioactive materialsareinjected directly into deep groundwater via thousands of "injection wells."
Heat
Heat is a water pollutant, increased water temperatures result in the deaths of manyaquatic organisms. These increases in temperature are most often caused by discharges of cooling water by factories and power plants.
Sewage
In developing countries, an estimated 90% of wastewater is discharged directly intoriversand streams without treatment.Even in modern countries, untreated sewage can send disease-bearing water into riversand oceans. Leaking septic tanks and other sources of sewage can cause groundwater andstreamcontamination.