Water Pollution

Water pollution can be defined in many ways. Usually, it means one or more substances have built up in water to such an extent that they cause problems for animals or people. Oceans, lakes, rivers, and other inland waters can naturally clean up a certain amount of pollution by dispersing it harmlessly.

Water covers two-thirds of the earth’s surface and makes up 75% percent of the human body. A water body is said to be polluted when toxic substances damage it, making it undrinkable and also dangerous for organisms to live in it. Harmful substances, like sewage, silt, toxic chemicals and domestic waste, are called water pollutants. They spoil the quality of water by altering its smell and colour, and render it unfit for drinking.

Pollution can enter a body of water in many ways, such as domestic sewage, agricultural run-off containing fertilisers and pesticides, eroded soil, acid rain, chemicals released from industries or other wastes from cities and towns. At places along the Ganga, people bathe, wash clothes and even defecate in the water. They also throw huge quantities of garbage, flowers, idols of gods and goddesses, untreated sewage, animal carcasses and non-biodegradable polythene bags directly into the river.

Chemical contamination of water due to chemicals, such as compounds of arsenic, fluorides and lead, cause plants and animals to die. The soil is also affected by polluted water, causing changes in its acidity, and, therefore, the growth of plant life.

Polluted water is unsuitable for drinking, recreation, agriculture and industry. Contaminated water destroys aquatic life and reduces its reproductive ability.

Thus, water pollution is all about quantities: how much of a polluting substance is released and how big a volume of water it is released into. A small quantity of a toxic chemical may have little impact if it is spilled into the ocean from a ship. But the same amount of the same chemical can have a much bigger impact pumped into a lake or river, where there is less clean water to disperse it.

Water pollution drastically reduces the quantity of dissolved oxygen in water, which results in the death of aquatic organisms. Anaerobic micro-organisms release gases like methane and hydrogen sulphide, leaving a foul-smelling, waste-filled body of water. The large quantities of chemicals that are washed in from the fields are responsible for the excessive growth of algae. Once the algae die, it serves as a food for bacteria. As a result, a lot of oxygen in the water is used up and many aquatic organisms die. Water that is suitable for drinking is called potable water. Sewage treatment plants treat wastewater to purify it before releasing it back into rivers and lakes. Municipal bodies treat water before supplying it to our households.