Envis Centre, Ministry of Environment & Forest, Govt. of India

Printed Date: Tuesday, July 23, 2024

Water Pollution

The Water (prevention and control of pollution) act 1974 define water pollution as "water pollutions" means such contamination of water or such alteration of the physical, chemical or biological properties of water or such discharge of any sewage or trade effluent or of any other liquid, gaseous or solid substance into  water (whether directly or indirectly) as may, or is likely to, create a nuisance or render such water harmful or injurious to public health or safety, or to domestic, commercial, industrial, agricultural or other legitimate use, or to the life and health of animals or plants or of aquatic organisms; In spite of the various increases undertaken for control of pollution, water pollution continues to rise on the lakes, rivers and other water bodies of modern India. The water quality of most of the rivers is below the prescribed C.P.C.B. Standards.

The spread of infectious disease by water pollution is a well-known hazard which is controlled by public health authorities in advanced countries and need not concern a discussion on industrial effluents, except to point out that microbiological growth is dependent on the concentration of certain trace elements. Whether or not these elements, in any way, influence the geographical variations in the prevalence of certain infectious diseases, is unclear. Investigations are presently under way, and these could eventually be reflected in changes in the practice of water treatment, just as dental recommendations have, sometimes, led to the adjustment of fluoride levels. Similarly, research on heart and blood vessel diseases has shown that they seem to be more prevalent in soft water regions.

Of far more concern to most engineers is the need to control toxic materials in water effluents. Radioactive isotopes are obviously a danger, although not immediately toxic in any likely doses. The pathological effects depend on the chemistry of the isotope: Strontium90, for example, is dealt with by the body as if it were calcium and becomes localized in the bones, while phosphorus 32 is treated as if it were the stable isotope phosphorus 31 and may get incorporated into the chromosomes of dividing cells, possibly causing mutation or cancer. Toxic ions are currently receiving much attention, since cyanide, lead, cadmium, arsenic, mercury, manganese and chromium are all among the industrial wastes which may be released. Although heavy metal may be discharged in highly diluted form, they can come back to man in a concentrated form if they are absorbed and retained by plants or animals and these creatures serve as food for other animals. The metals, thus, pass up the food chain, becoming progressively more concentrated each predator eats many prey. That is why heavy metals, dumped in the sea, are especially likely to be found in the largest amounts in large predator fish like the tuna. The other animals, responsible for concentrating toxic metals, are shellfish which filter large volumes of sea water and may retain some constituents.

The dangers to health from, heavy metals depend, to some extend, on the form in which they occur. Mercury, for example, is not accumulated by animals as a metal or ion, but in organometallic form, such as methyl or dimethyl mercury. Methylation of mercury by micro-organisms occurs readily in the environment, especially at the bottom of lakes and seas, and, thus, there is always a danger that wastes discharges, as relatively inert, may reappear in a more alarming form.
Another type of water pollution occurs when chemicals persist in the environment. An immense number of synthetic compounds are now made and used; many of these, if discharged, are readily metabolized by micro-organisms, and cause no health danger unless present in high concentrations. Some, however, are not degraded and persist with the potential to build up in concentration of their discharge is continued. Examples of these include some plastics, the halogenated hydrocarbon, pesticides and some types of detergents. The latter can become an indirect public health danger, if allowed to build up to levels, that impair the efficiency of water purification plants. At one time or another, humans have been poisoned fatally by each of the common pesticides, though this has resulted from the deliberate or accidental ingestion of large amounts. Through pollution, people, now, contain a few parts per million of chlorinated hydrocarbons in their fat tissue, but no adverse effects on health have been detected at this level. If only medical aspects were considered, it would be concluded, in general, that pesticides have greatly increased health throughout the world through control of disease bearing pests and augmentation of food production.

Foreign materials either of national or man made origin, contaisundatery water sources andin excess of the ophmain ossimitative capacities of the system in any be harmful to like because of their toxicity by accunmtalive potential and in the seduction of the normal oxygen level of water. Pollutants may also seep down and affect the groundwater deposits.

The water (Prevention and context of Pollution) Act 1974 has prescribed that it is the duty of every local body and industry to ensure that effluents conform to prescribed standards and are discharged only with a proper consent of the State Pollution Control Board.

Source of Pollution

Polluting substances in natural sources of water have their origins sin a great variety of places, For convenience, these sources of contamination of natural waters are classified here as natural, agricultural, mining municipal and industrial.

Natural Pollution

This type of pollution is either accidental or occasional. Aerial contaminants, like gases and dusts, get transferred to a body of water in the form of rainfall, soil silt, stripped from the land by heavy rainfall, or melting snow, or as soluble salts, leached from the earth by surface streams, Leachates from animal excreta, decaying bodies of plants and animals, and the decay of large quantities of organic matter as in swamps or deep ponds also introduced appreciable quantities of microorganisms.

Agricultural Pollution

Soil and silt-washings from land surfaces were mentioned earlier as a form of natural pollution; agricultural development of land may multiply the quantity of such pollution many fold. Use of fertilizers, insecticides, herbicides and weed killers, in agricultural practices, poses serious pollution problems as most of them are resistant to natural degradation. Warrick has described stream pollution that resulted in a series of fish kills, causes by the use of insecticides in the cotton fields of northern Alabama during the late summer of 1950.

Mining Pollution

Fines or tailings from ore washing are disposed off in wate4 suspensions, which are ultimately transferred to the natural stream and which, thus, gets polluted. In addition to inert suspended solids, mining operations, sometimes, produce soluble toxic materials. An outstanding example of this stream pollution which is today one of our major unsolved problems, is the acid drainage from coal mines.

Municipal Pollution

Municipal wastes, mainly domestic sewage, includes the discharges from toilets, wash rooms, kitchens and similar areas in dwellings, institutions, commercial and industrial buildings. Its principal pollutional characteristics are pathogenic bacteria, suspended solids and oxygen consuming organic matter, In urban areas, these are generally disposed of collectively, thus, overburdening the receiving water sources.

Industrial Pollution

Water is an essential raw material in almost all manufacturing plants, though only a small part of it may appear in the final product. The remainder becomes a waste material contaminant, to a smaller or large degree, depending on its usage in the plant. After entering the natural water resources, it contaminates them. Industries which are considered the principal sources of pollution may be classified as apparel, food and drugs, chemicals, materials and energy.

Effect of Effluent Natural Sources of Water

Pollution of natural waters by sewage and industrial wastes is objectionable and damaging for many reasons. Of primary importance is the possible hazard to public health and safety. Of lesser consequence but still very real are damage to aesthetic and intangible attributes of the stream and destruction of the economic value of clean natural waters. Considering all these ill aspects of water pollution, different pollution control agencies in the world have proposed limits in relation to various pollution parameters for different uses.
Effects of pollution on public health and safety, effect on aquatic and other life, damage to property and other economic losses are now briefly described.

Effect on Public Health and Safety

The principal hazards to public health, from polluted streams, are mainly due to the presence of pathogenic  bacteria from domestic sewage, toxic materials (acids, alkalis, specific poison like cyanide and heavy metals, salts), and materials from industrial wastes. Danger to public health from polluted waters comes not only from direct use of the water but also from consuming food, for example, fish, that have lived in the polluted stream. Many poisonous substances are absorbed by fish, often in a concentrated form. Hence eating of fish from polluted water may be even more hazardous than drinking the water.

Effect on Aquatic and Other Life

Pollution of natural waters may be disastrous to fish and other organisms naturally inhabiting the stream. Organic wastes under the influence of bacterial action deplete the dissolve oxygen by consuming it in biochemical oxidation reaction. This may suffocate the fish and other aquatic animals which require the presence of an appreciable concentration of dissolved oxygen. With mild pollution, fish may acquire a flavour that renders their flesh unfit for use as food; whereas with more severe contamination; the fish sicken or die. The latter may also be a result of the presence of substances that are not in themselves toxic but cause asphyxiation by injuring the gills. Suspended solids such as silt and coal have been particularly troublesome in this respect.

Damage to Property

Discharge of acids and occasionally of other industrial wastes leads to damage of property through corrosive attack. Corrosion of steel objects such as ships, damage to concrete structures in the stream and corrosion of piping, pumps, valves and other equipments in plants, using contaminated water as cooling water, are quite common.

Other Economic Loss

Polluted streams which are used as the only source of municipal or industrial water require substantial treatment at considerable cost for the removal of suspended solids, taste, odour, color, hardness and specific chemicals present. If hot streams are used as a source of water supply, the cost of cooling is also added.


Domestic wastewater, industrial effluents and agricultural runoff contribute to water pollution.

Domestic wastewater… Increasing water consumption by burgeoning urban population coupled with poor wastewater treatment facilities, and lack of sanitation facilities in urban and rural areas contribute substantially to the water pollution in UP. Lack of adquate sewage collection, treatment and disposal facilities contributes to enhanced levels of biological pollution of the lakes, streams and rivers. Water contamination leads to may water related diseases, and subsequently to social and economic burden on the state.

Lack of toilet and drainage facilities…

Biochemical oxygen demand … 

BOD from industry … 

Fertilizer and pesticide runoff from agriculture… The green revolution ushered by the development of high yielding varieties and associated development of high yielding varieties and associated development of water resources and application of agricultural chemicals, has mad India self sufficient in food grains. But the negative impacts of use of agricultural chemicals, often used indiscriminately, on water environment are being felt now. The fertilizer run off leads to nutrient enrichment in the receiving water bodies resulting in eutrophication. The pesticides get accumulated in the food chain, with increasing concentrations along the food chain (bio-magnification). This in turn affects various species in the food chain, including man.

Effects of water pollution
The effects of water pollution are not only devastating to people but also to animals, fish, and birds. Polluted water is unsuitable for drinking, recreation, agriculture, and industry. It diminishes the aesthetic quality of lakes and rivers. More seriously, contaminated water destroys aquatic life and reduces its reproductive ability. Eventually, it is a hazard to human health. Nobody can escape the effects of water pollution.
The individual and the community can help minimize water pollution. By simple housekeeping and management practices the amount of waste generated can be minimized.