Many industrial processes produce chemical wastes. These include acids, alkalis, organic solvents, detergents, oils, dyes, and heavy metals (e.g mercury, copper and lead). Normally, these wastes should be treated and made harmless before they are emptied into rivers, lakes and seas. Often , to cut production costs, this is not done. The effect of these chemicals on the aquatic ecosystem is extremely harmful. Factories , mining and smelting works, refineries and power plants are the main sources that pollute water with chemical wastes.
Unlike sewage, most industrial chemical wastes are non biodegradable. They remain in the water and cause extensive damage to aquatic plants and animals. Certain chemicals like mercury compounds tend to accumulate in organisms and are passed along food chains. They become concentrated in the bodies of the final consumers. After a period of time, the final consumers shown sign of mercury poisoning. A real example of such mercury poisoning that affected humans (final consumers in the food chain). This shows how pollution affects a functioning ecosystem, and how far reaching its effects are!
Thermal pollution:
Several industries like oil refineries , steel, mills, power plants and breweries use water for cooling their plants. Usually water from a nearby river PR lake is pumped in and used for the cooling process. The resulting warm water is then emptied back into the river or lake. This causes an increase in the temperature of the water, causing less oxygen to dissolve in it. Many types of fishes which have a small tolerance range for oxygen die. This upsets and delicate balance of the aquatic ecosystem, and changes occur in the typed of plants and animals that are found in the affected habitat.
