Effect of Ecological Imbalance on water.Â
A vitally important factor like water is also polluted because of various human activities. The main sources of water pollution are
- Domestic sewage
- Industrial effluents
- Chemicals (e.g. fertilizers, pesticides, herbicides, etc; the surface runoffs from agricultural fields)
- Mineral oils, etc.
The water pollutants may be classified as follows.
a)   Biological – Pathogens like viruses, bacteria, protozoa, worms, etc.
b)   Chemical – (i) Inorganic – e.g. nitrates, phosphates, chlorides and fluorides. (ii) Organic – e.g. pesticides, dyes, chlorocompounds, phenols, paints, plastics, etc.
(iii) Heavy metals – e.g. soluble heavy metal ions like Hg, Pb, cadmium, Cu, Zn, and their organometallic compounds.
c)   Physical – Heat from industries.
Consequences of water pollution.
- Decrease in the percentage of dissolved oxygen thereby affecting aquatic plants and animals. In addition, decomposition of organic waste in such water is done by anaerobic bacteria. This releases methane and other foul smelling gases.
- Consumption of water containing various aquatic pathogens causes diseases in plants, animals and humans.
- The nitrates and phosphates in polluted water cause algal blooms. These disrupt the balance of aquatic eco system.
- Water polluted with domestic sewage can spread diseases like cholera, typhoid, dysentery, diarrhea and number of other water borne diseases.
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