Causes of Water Pollution
When toxic substances enter lakes, streams, rivers, oceans, and other water bodies, they get dissolved or lie suspended in water or get deposited on the bed. This results in the pollution of water whereby the quality of the water deteriorates, affecting aquatic ecosystems. Pollutants can also seep down and affect the groundwater deposits.
Sewage and Industrial waste discharge:
Domestic households, industrial and agricultural practices produce wastewater that can cause pollution of many lakes and rivers. Sewage is the term used for wastewater that often contains faeces, urine and laundry waste. Untreated sewage water in such areas can contaminate the environment and cause diseases such as diarrhoea.
Many industrial facilities use freshwater to carry away waste from the plant and into rivers, lakes and oceans. Pollutants from industrial sources include Asbestos, Lead, Mercury, Nitrates, Phosphates, Sulphur, Oils, Petrochemicals etc.
In the atmosphere, water particles mix with carbon dioxide, sulphur dioxide and nitrogen oxides, this forms a weak acid. When it rains the water is polluted with these gases, this is called acid rain. When acid rain pollutes marine habitats such as rivers and lakes, aquatic life is harmed.
Oil Spills: Oceans are polluted by oil on a daily basis from oil spills, routine shipping, run-offs and dumping. Oil cannot dissolve in water and forms a thick sludge in the water. This suffocates fish, gets caught in the feathers of marine birds stopping them from flying and blocks light from photosynthetic aquatic plants.