Water Pollution Causes - Practice Questions & MCQ

Water is the important constituent of life-support systems. Water is the most important natural resource. 80% of the earth's area is occupied by water. However, hardly 2.5% makes up the total world's supply of freshwater including the frozen water in the polar ice caps and glaciers. Water is needed for irrigation, industry, domestic needs, shipping and for sanitation and disposal of waste. The conservation and keeping up a good supply of water is this very essential. Man has, however, polluted much of this limited supply of water by industrial wastes, sewage and a number of synthetic chemicals. Many rivers of the world receive heavy flux of sewage, domestic waste, industrial effluents, agricultural wastes, etc, which contain substances varying from simple nutrients to highly toxic materials. Polluted water is the water which has more negative qualities than it has positive ones, i.e, it is no longer fit for any use. 

Causes of Water Pollution : Pathogens, Organic wastes, Chemical Pollutants

(i) Pathogens: The most serious water pollutants are the disease causing agents called pathogens. Pathogens include bacteria and other organisms that enter water from domestic sewage and animal excreta. Human excreta contain bacteria such as Escherichia coli and Streptococcus faecalis which cause gastrointestinal diseases.

(ii) Organic wastes: The other major water pollutant is organic matter such as leaves, grass, trash etc. They pollute water as a consequence of runoff. Excessive phytoplankton growth within water is also a cause of water pollution. These wastes are biodegradable.

(iii) Chemical Pollutants: As we know that water is an excellent solvent, water-soluble inorganic chemicals that include heavy metals such as cadmium, mercury, nickel etc constitute an important class of pollutants. All these metals are dangerous to humans because our body cannot excrete them.