Water Pollution

Water pollution is defined as the contamination of water sources by substances that render the water unfit for drinking, cooking, cleaning, swimming, and other activities. Chemicals, trash, bacteria, and parasites are all examples of pollutants. All types of pollution eventually end up in the water. Water pollution is caused by one of four factors: sewage discharges, industrial activities, agricultural activities, and urban runoff, which includes stormwater.

Causes of Water Pollution

Sewage Water

Sewage water includes discharges from houses and other establishments.
The sewage contains human and animal excreta, food residues, cleaning agents, detergents, etc.
Domestic and hospital sewage contain many undesirable pathogenic microorganisms.

Biological Oxygen Demand (BOD)

It is the quantity of dissolved oxygen required by microorganisms for aerobic decomposition (in the presence of oxygen) of organic materials (waste or pollution).
The BOD increases with the amount of organic matter present (e.g., in sewage and polluted bodies of water).
One of the main reasons for treating wastewater prior to its discharge is to reduce its need for oxygen and thereby lessen its demand.

Dissolved Oxygen (DO)

The Presence of organic and inorganic wastes in water decreases the dissolved oxygen content of the water.
Water having DO content below 8.0 mg/L may be considered contaminated.
Water having DO content below. 4.0 mg/L is considered to be highly polluted.
DO content of water is important for the survival of aquatic organisms.
A number of factors like surface turbulence, photosynthetic activity, O2 consumption by organisms, and decomposition of organic matter are the factors that determine the amount of DO present in water.
The higher amounts of waste increase the rates of decomposition and O2 consumption thereby decreases the DO content of water.

Other Causes for pollution of water

Urbanization.
Deforestation.
Industrial effluents.
Social and Religious Practices.
Use of Detergents and Fertilizers.
Agricultural run-offs– Use of insecticides and pesticides.

Effects of Water Pollution in India

Water Pollution on Human Health

Domestic and hospital sewage contain many undesirable pathogenic microorganisms, and its disposal into water without proper treatment may cause an outbreak of serious diseases, such as typhoid, cholera, etc.
Metals like lead, zinc, arsenic, copper, mercury and cadmium in industrial wastewaters adversely affect humans and other animals.
Consumption of such arsenic polluted water leads to accumulation of arsenic in the body parts like blood, nails and hairs causing skin lesions, rough skin, dry and thickening of the skin and ultimately skin cancer.

Water Pollution on the Environment

Micro-organisms involved in biodegradation of organic matter in sewage waste consume a lot of oxygen and make water oxygen deficient killing fish and other aquatic creatures.
Presence of large amounts of nutrients in water results in algal bloom (excessive growth of planktonic algae. This leads to ageing of lakes
High concentrations of DDT disturb calcium metabolism in birds, which causes thinning of eggshell and their premature breaking, eventually causing a decline in bird populations.

Effects of Water Pollution on Aquatic Ecosystem

Polluted water reduces Dissolved Oxygen (DO) content, thereby, eliminates sensitive organisms like plankton, molluscs and fish etc.
Hot waters discharged from industries, when added to water bodies, lowers its DO content.

Eutrophication

The nutrient-enrichment of the lakes promotes the growth of algae, aquatic plants and various fauna. This process is known as natural eutrophication.
Human activities cause similar nutrient enrichment of lakes at an accelerated rate, resulting in the phenomenon known as cultural eutrophication.

Algal Bloom

Phytoplankton (algae and blue-green bacteria) thrive on the excess nutrients and cover nearly the entire surface layer. This is known as to as an algal bloom.
During the day, phytoplankton is photosynthetic, adding oxygen to the aquatic ecosystem. However, they consume far more oxygen at night due to their aggressive respiration.
As the population of phytoplankton is very high, algal blooms accelerate the rate of oxygen depletion.

Control Measures of Water Pollution

Sewage water and industrial effluents should be treat before releasing them into bodies of water..
Power plants should cool hot water before releasing it.
Domestic cleaning should be prohibited in tanks, streams, and rivers that supply drinking water.
Excess fertiliser and pesticide use should be avoid.
Organic farming and the effective use of animal waste as fertiliser should be encouraged.
Water hyacinth (an aquatic weed) can purify water by removing some toxic materials and heavy metals.
To clean oil spills in water, one can use bregoli, a byproduct of the paper industry resembling sawdust, along with an oil zapper and microorganisms.
Precipitation, the ion exchange process, reverse osmosis, and coagulation are some chemical methods that aid in the control of water pollution.