What is Water Pollution

Water pollution is an undesirable change in the state of water, contaminated with harmful substances. It is the second most important environmental issue next to air pollution. Any change in the physical, chemical and biological properties of water that has a harmful effect on living things is water pollution. It affects all the major water bodies of the world such as lakes, rivers, oceans and groundwater.

Pollution of the water bodies disturbs the ecosystem as a whole. Polluted water is not only unsafe for drinking and other consumption purposes, but it is also unsuitable for agricultural and industrial uses. The effects of water pollution are detrimental to human beings, plants, animals, fish and birds. Polluted water also contains virus, bacteria, intestinal parasites and other pathogenic microorganisms. Using it for drinking purpose is the prime cause for waterborne diseases such as diarrhea, dysentery and typhoid.

What are the Sources of Water Pollution?

The important sources of water pollution are domestic wastes, industrial effluents and agricultural wastes. Other sources include oil spills, atmospheric deposition, marine dumping, radioactive waste, global warming and eutrophication. Among these, domestic waste (domestic sewage) and industrial waste generate maximum pollutants, which make their way to groundwater and surface water bodies.

Domestic Sewage: Domestic sewage is wastewater generated from household activities. It contains organic and inorganic materials such as phosphates and nitrates. Organic materials are food and vegetable waste, whereas inorganic materials come from soaps and detergents. Usually people dump household wastes in the nearby water source, which leads to water pollution. The amount of organic wastes that can be degraded by the water bodies is measured in terms of Biological Oxygen Demand (BOD). BOD is nothing but the amount of oxygen needed by microorganisms to decompose the organic waste present in the sewage. The higher the amount of BOD, the more water is polluted with organic waste and vice versa. Many people are not aware of the fact that soaps and detergents enrich the water bodies with phosphates. These phosphates often lead to algal bloom and eutrophication, which are common problems in stagnant water bodies such as ponds and lakes. Algal bloom and eutrophication lead to the suffocation of fish and other organism in a water body.

Industrial Effluents: Wastewater from the manufacturing and processing industries causes water pollution. The industrial effluents contain organic pollutants and other toxic chemicals. Some of the pollutants from industrial source include lead, mercury, asbestos, nitrates, phosphates, oils, etc. Wastewater from food and chemical processing industries contribute more to water pollution than the other industries such as distillery, leather processing industries and thermal power plants. Also, dye industries generate wastewater which changes the water quality especially water color. Since the water color is changed, there is alteration in the light penetration, thereby disturbing the aquatic plants and animals. Many of the big industries have come up with wastewater treatment plants. However, it is not the case with small-scale industries. It is very difficult to treat wastewater from the industries.

Let's take the example of Minamata disease in which more than 1,784 people died and many more suffered due to consumption of fish, contaminated with methyl mercury. It was caused by release of methyl mercury from Chisso Corporation's chemical factory. The disease continued to affect animals and humans for over 30 years, from 1932 to 1968.

Agricultural Waste: Agricultural waste include manure, slurry and sewage runoffs. Most of the agricultural farms use chemical fertilizers and pesticides. The runoffs from these agricultural fields cause water pollution to the nearby water sources such as rivers, streams and lakes. The seepage of fertilizers and pesticides causes groundwater pollution, which is commonly known as leaching. Although the quantity of agricultural waste is low, the effects are highly significant. It causes nutrient and organic pollution to both water and soil. Nutrient pollution causes an increase in the nitrates and phosphates in the water bodies, which again leads to eutrophication.

Depending upon the origin, sources of water pollution are classified as point source and non-point source. Point source pollution discharges the harmful waste directly into water bodies, for example, disposal through wastewater treatment plants. On the other hand, non-point source pollution delivers indirectly through other ways, for example, water pollution from acid rain.

How to Prevent Water Pollution?

Although 71% of earth's surface is covered with water bodies, we don't have enough water to drink. Many researches have been done on water purification systems in order to have safe drinking water. However, there are about 1 billion people, who don't have proper excess to drinking water. Therefore, water needs to be conserved and prevent from pollution in order to make it safe for drinking and other consumption purposes. Reducing the amount of water use can help conserve water as well as save money.

The effective way to prevent water pollution is to include eco-friendly household products such as low-phosphate detergents and other toiletries, improving housekeeping, turning off the water tap when not in use, disposing the household wastes in proper sites far away from the water sources, etc. Last but not the least, planting more trees can also prevent water pollution by reducing soil erosion and water runoff. Educating people about water pollution is an important approach to reduce water contamination.