Question

what is water pollution? in 1000 words

Answer 1

$\bf{\huge{\mathfrak{\boxed{\red{Water Pollution\:}}}}}$

Water pollution is defined as the addition of some substance (organic, inorganic, biological, and radiological) or factor (e.g., heat) which degrades the quality of water so that it either becomes health hazard or unfit for use.

Sources of Water Pollution and Effect of Water Pollutants:

$\huge{\boxed{\mathfrak\pink{\fcolorbox{red}{lawngreen}{Domestic Wastes :\:}}}}$

Raw sewage contaminates water with pathogens. Micro­organisms causing degradation of sewage take up most of the oxygen present dissolved in water.

• Surface Run-Off:

The pollutants present on the surface of land and fertilizers added to the soils” are washed down into water reservoirs and water courses during rains. This flow of fertilizer rich water into streams and lakes gives rise to eutrophication.

• Industrial Effluents:

They are industrial wastes which are allowed to pass into water bodies. The important toxic chemicals presents in them are:

• Mercury:

It is released during combustion of coal, smelting of metallic ores, chloralkali, paper and paint industries. Mercury is persistent. In water it gets changed into water soluble dimethyl form [(CH,) 2Hg)] and enters the food chain accompanied by biological or ecological amplification. Human beings feeding on poisoned animals and fishes develop a crippling deformity called minamata disease.

• Lead:

The sources of lead pollution are smelters, battery, industry, paint, chemical and pesticide industries, automobiles’ exhausts, etc. It is mutagenic and causes anaemia, headache, and bluish lines round the gums.

• Cadmium:

It shows biological amplification and accumulates inside kidneys, liver, pancreas and spleen. It causes renal damage, emphysema, hypertension, testicular necrosis and damage to placenta.

• Other metals :

Copper, zinc, nickel, titanium, etc. cause toxaemia and change in enzyme functioning.

Thermal Pollution:

Many industrial processes are causing thermal pollution leading to higher temperatures. These industries do not contaminate the water supply, but use a lot of water for cooling purposes and return this water to the stream at a higher temperature, which affect the biotic components in the aquatic habitat. Warmer water holds less oxygen (14 ppm at 0°C, 1 ppm at 20°C) and hence its Biological Oxygen Demand (BOD) increases. Green algae are replaced by less desirable blue-green algae. Trout eggs fail to hatch while Salmon does not spawn at higher temperature.

$\huge{\boxed{\mathfrak\pink{\fcolorbox{red}{lawngreen}{Prevention: \:}}}}$

Water pollution can be controlled to a large extent on the principle, “the solution to pollution is dilution.”

The various methods for the control of water pollution are discussed below:

1. The sewage pollutants are subject to chemical treatment to change them into non-toxic substances or make them less toxic.

2. Water pollution due to organic insecticides can be reduced by the use of very specific and less stable chemicals in the manufacture of insecticides.

3. Oxidation ponds can be useful in removing low level of radioactive wastes.

4. Thermal pollution can be reduced by employing techniques—through cooling, cooling ponds, evaporative or wet cooling towers and dry cooling towers. The purpose is that the waters in the rivers and streams should not get hot.

5. Domestic and industrial wastes should be stored in large but shallow ponds for some days. Due to the sun-light and the organic nutrients present in the waste there will be mass scale growth of those bacteria which will digest the harmful waste matter.