Summarize the primary information regarding water pollution.

Water is essential for life. Without water,there would be no life. We usually take water for granted for its purity,but we must ensure the quality of water.
Pollution of water originates from human activities. Pollution reaches surface or ground water through different paths.
An easily identified source or place of pollution is called a point source,e.g.,municipal and industrial discharge pipes.
Non-point sources of pollution are those where a source of pollution cannot be easily identified,e.g.,agricultural run-off (from farms,animals,and crop-lands),acid rain,and storm-water drainage (from streets,parking lots,and lawns).
The major water pollutants and their sources are listed below:

Pollutant	Source
Micro-organisms	Domestic sewage
Organic wastes	Domestic sewage,animal excreta and waste,decaying animals and plants,discharge from food processing factories.
Plant nutrients	Chemical fertilizers
Toxic heavy metals	Industries and chemical factories.
Sediments	Erosion of soil by agriculture and strip mining.
Pesticides	Chemicals used for killing insects,fungi,and weeds.
Radioactive substances	Mining of uranium-containing minerals.
Heat	Water used for cooling in industries.