The impacts of pollutants depend upon its properties and amount. Pollutants bring about physical and chemical changes that make the Water Rivers, lakes and ponds useful for drinking and harmful to aquatic life. Some of the main effects of pollutants are:
(i) The biological effects of chemical pollutants are varied; compounds of mercury, arsenic, and lead are poisonous, some compounds are corrosive. Organic sulphur compounds interfaces with nitrification.
Inorganic nitrates and phosphates stimulate excessive plant growth in lakes and reservoirs. The organochlorine pesticides are highly persistent and pass through food chains. They mainly accumulate in fatty tissues and affect the nervous system. The broad spectrum pesticides cause mass destruction of aquatic life, (ii) Change in colour is a very common effect. This is produced by dyes, inorganic substances like chromium and iron compounds.
(iii) Turbidity due to very fine suspended matter or colloidal substances makes water unfit for drinking and for industrial use.
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(iv) Pollution caused by industrial effluents containing iron, free chlorine, phenol, manganese, detergents, oils, hydrocarbons and decomposition products. Unpleasant odour occurs due to presence of chlorine, phenol, hydrogen sulphide, ammonia, algae and micro-organisms.