Water pollution and its control


Water makes up 70% of the earth but the bioavailability of water is a mere 3%. Bioavailability is the overall amount of water fit for domestic use. The poor availability of water is linked with the degree of water pollution in a given reservoir of water. Water pollution is one of the growing issues in many countries.  "It refers to the pollution of various water sources and reservoirs (water bodies such as canals, tanks, ponds, rivers, and oceans) because of pollutants".

Water pollutants

A pollutant is a causative agent, the most common water pollutants are the domestic wastes, industrial effluents, wastes generated from thermal plants, agricultural wastes, biological wastes generated by plants and animals, and oil leakage from ships. Water pollutants can be chemical, microbial or physical in nature but in most cases, chemical agents are being diverted into rivers, ponds, and other water reservoirs. Most common toxic chemicals that pollute water are sulphur, carbon, and ammonia. In an aquatic ecosystem, water pollution is caused by the disproportionate growth of algae, bacteria and fungal organisms. Some of the important water pollutants are explained below.

  1. Domestic Sewage: Household human activities generate a lot of waste called domestic sewage. Worldwide, about 6 billion kilograms of garbage is released into the oceans every year. Domestic sewage contains biodegradable organic matter formed by bacterial decomposition. Microbes involved in the biological decomposition of organic wastes consume a lot of oxygen available in the water. Consequently, many aquatic species die because of oxygen deficiency. Aquatic oxygen deficit is a result of gradual depletion of available oxygen levels in the water. On the other hand, the non-biodegradable impurities such as suspended soil, colloidal wastes and dissolved materials released into ponds, rivers and oceans make water worse. Industrial effluents rich in some chemical-based salts; nitrates and phosphates combine with the toxic metals like lead and mercury result in the death of fish and other useful aquatic species. The proportion of the organic compounds present in the polluted water makes it odorous, distasteful and unfit for use.

  2. Agricultural wastage: Agriculture is a great contributor of toxic wastes. Various farming activities result in the toxic by-products. Modern farming is accountable to release a lot of deadly chemicals into the water in the form of pesticides and weedicides.  As a result, these sprays along with the chemical-based manures, water loses its quality. The sprays also cause soil pollution to make it infertile. When water flows through such soil, the chemicals will move to the water bodies like tanks, ponds, rivers, etc. Sewage water and agricultural run-off encompass nutrients like nitrogen and phosphorus, which aids in the development and growth of plankton called eutrophication. Eutrophication results in the depletion of oxygen levels in the water bodies resulting in the death of aquatic fauna. The presence of multiple nutrients in waters results in the excessive growth of planktonic algae, and this phenomenon is known as an algal bloom. Algal bloom gives a distinct colour to the water bodies which again is not a good sign.

  3. Industrial Effluents: Some of the toxic substances encountered in the industrial waste causes biomagnification. Biomagnification is a process wherein the amounts of toxic substances passed on from one trophic level keeps increasing through each successive level. This is because the toxic substances accumulated by an organism cannot be metabolized or excreted, instead, it automatically passed on to the higher trophic level. If we take mercury and DDT, the concentration of DDT will be increased at every successive trophic levels. If the DDT levels are at 0.003 ppb ( parts per billion) in water, it can reach 25 ppm by the time the chemicals enter the birds and this is called bio-magnification.  When DDT accumulates beyond the absolute levels in our system, they become very potent ending up with the destruction of species. Increased levels of DDT can disturb calcium metabolism in birds resulting in thinning of their eggshell and premature breaking and the ultimate result is the deterioration of bird populations. DDT also has the ability to interfere with brain function and the normal functioning of vital organs such as the heart, lungs and kidneys.


Coliform levels in water 

Coliforms are the type of bacteria found in the gut (digestive tracts)  of animals, including humans, unfortunately, the polluted water contain coliform bacteria making it unfit for consumption.  Many rivers in India suffered a huge blow becasue of high levels of coliform organisms. Some of the rivers most affected by this are  Ghaghara River, Chambal, Mahi, Vardha, Yamuna, Ganga, Gomti, and Godavari. In a normal scenario, the coliform must be well-below 104 MPN/100 ml, this makes water potable. From the past 14 years, about 47%  of water quality monitoring companies reported the coliform levels as high as 500 MPN/100 ml which is highly dangerous.  To prevent the ill effects from coliform water, treatment of domestic sewage and subsequent utilization of treated sewage for irrigation is important. Optimistically, Indian wastewater treatment plant market is growing rapidly at the rate of 10 to 12 per cent which is further boosted by supplying water treatment equipment by the USA.


Effects of water pollution

It is always necessary to control water pollution as it can also lead to some of the deadly diseases like jaundice, cholera, typhoid, dysentery, dengue, malaria, etc and many of them take a long time to cure. Water pollution results in the depletion of oxygen levels in the water. Such a phenomenon will further lead to the death of aquatic plants and animals as the bio-availability of oxygen is low in the water bodies. Death of biological organisms in the water, in turn, result in biodiversity destruction. Water pollution can lead to chronic diseases of the gastrointestinal system, skin and some other infectious diseases. The crops grown from such water are is highly toxic, as a result, the lifespan of the individual's will be in stake. 


Prevention and management of water pollution

It is very important to control and manage the pollutants in order to save the existing species. The pollution must be prevented at source; avoid activities that generate a lot of unwanted pollutants. Biological methods like growing invasive plant water hyacinth will help to control and remove BOD, suspended solids, nutrients such as phosphorous and nitrogen. Some of the water pollution management measures are:

  1. All the domestic wastes and wastewater must be treated before releasing them into the rivers and lakes.

  2. Drinking water and irrigation water must be separated and treated accordingly.

  3. All the water bodies must be kept clean through a scheduled cleaning.

  4. Drinking water reservoirs must not be used for washing cattle, bathing, and other purposes. 

  5. Planting trees help to reduce acid rain and pollution of groundwater.

  6. Rainwater harvesting is obligatory because it will conserve the water for the future and reduce wastage of fresh water.


Further reading


Air pollution


Noise pollution


Environmental issues

4 . 

 Management of natural sources            



  1. What is bioavailability of water?

  2. List down the most common pollutants responsible for water pollution

  3. What is the one major issue that most of the rivers in India facing?

  4. Explain the strategies to manage water pollution.

  5. What is Eutrophication, how does it affect water?

  6. What are the effects of water pollution?




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