Here is a compilation of essays on ‘Water Pollution’ for class 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Water Pollution’ especially written for kids, school and college students.
Essay on Water Pollution
ADVERTISEMENTS:
Essay Contents:
- Essay on the Introduction to Water Pollution
- Essay on the Types of Water Pollutants
- Essay on the Sources of Water Pollution
- Essay on the Ill Effects of Water Pollution
- Essay on the Control of Water Pollution
Essay # 1. Introduction to Water Pollution:
The earth has about 1.35 cubic kilometres of water of which about 97% is found in the oceans. The sole source of land water is atmospheric precipitation. It is roughly estimated that about 27% of precipitated water flows into oceans and about 73% is evaporated. A little percentage of water enters the soil whose some part reaches the deep zones. This is called gravitational water whose upper layer is called water table.
Surface water usually contains small amount of suspended particles (organic and inorganic) and a number of micro-organisms like bacteria, algae, viruses, protozoans etc. and even higher organisms. Water becomes polluted when these substances increase in their concentration. Water pollution is a serious health-hazard in India. It is estimated that 50-60% Indian population suffers from water-borne diseases and about 30-40% of all deaths occur due to water pollution.
A recent study of Tata Energy Research Institute has shown that in the past 50 years, the availability of fresh water has declined by two-third. In India, nearly, 44 million people have been affected by poor quality of water caused by water pollution.
Some poisons, pathogens pollute the water even in low concentration. Natural water pollution is due to silt, clay, animal wastes, minerals etc. Provision of clean water is the bare necessity of every human being. It ought to be the priority of all governments. It is the need of the hour to create public awareness.
ADVERTISEMENTS:
ADVERTISEMENTS:
Essay # 2. Types of Water Pollutants:
Water used for household, agricultural and industrial purposes when discharged after use is polluted with soluble, insoluble matter and even pathogens.
Water pollutants can be classified under following categories:
1. Biological:
ADVERTISEMENTS:
It includes pathogens like bacteria, viruses, worms and protozoa. Most of these are added by excreta of animals.
2. Chemical:
(a) Inorganic e.g. phosphates, nitrates, fluorides and chlorides.
(b) Organic e.g. Phenols, plastics, dyes, pesticides and chloro compounds.
ADVERTISEMENTS:
(c) Heavy metals. In this category heavy metals like cadmium, mercury, copper, zinc and their organometallic compounds are included.
3. Physical as Waste Heat from Industrial Plants:
Physical pollution involves the changes in the physical properties of water e.g. turbidity, temperature, etc.
Essay # 3. Sources of Water Pollution:
They can be broadly classified into following groups:
1. Domestic effluents;
2. Industrial effluents;
3. Surface run-off; and
4. Waste heat.
1. Domestic Effluents:
In this case waste waters are discharged into common public sewerage system.
They include:
(i) Human and animal excreta,
(ii) Plenty of organic matter in the form of food residue;
(iii) Detergents etc. and
(iv) A large number of bacteria.
Municipal sewers contain many kinds of pollutants and a lot of industrial wastes.
Beautiful Dal Lake in Kashmir has been polluted due to the dumping of raw sewage and domestic effluents from house boats and nearby localities. Pollutants from soap and detergent industries include alkalies, tertiary ammonium compounds, fats, fatty acids, sulphonated hydrocarbons like alkyl benzene sulphonate and polyphosphates, while pollutants from paper and pulp industries include sulphides, bleaching liquors, cellulose fibres, wood sugars and organic acids.
Domestic Sewage:
Domestic sewage contains three types of impurities:
(i) Suspended solids include soil particles like sand, silt, clay, etc.
(ii) Colloidal particles are large sized but suspended compounds which may be inorganic or organic. These also include faecal matter, bacteria, cloth, paper, fibres, etc.
(iii) Dissolved solids e.g. inorganic nutrients (like nitrates, ammonia, phosphates, sodium, calcium, etc.), toxic metallic ions and organic compounds.
These three types of impurities collectively form 0.1% of the domestic sewage but their relative amounts vary. Out of three types of impurities, biodegradable organic matter is most abundant.
Relationship between organic matter of domestic sewage. Biochemical Oxygen Demand (BOD), Dissolved Oxygen (DO) and Chemical Oxygen Demand (COD):
Domestic sewage mainly contains biodegradable organic matter which can be decomposed by bacteria and other micro-orgarusms in the presence of oxygen. Biochemical Oxygen Demand (BOD) is the amount of oxygen required by the micro-organisms in milligrams in five days to completely decompose the organic matter present in one litre of polluted water at 20°C. Higher is the amount of oxygen consumed, greater is the degree of organic pollutants.
The BOD of different water sources is different e.g. less than 1 for pure drinking water; below 1500 mg/litre for a weak organic waste water body; between 1500-4000 mg/litre for a medium organic waste water body while it is more than 4000 mg/litre for a strong organic waste water body. So the input of domestic sewage containing high amounts of biodegradable organic matter increases the BOD of water body.
But as the micro-organism consume oxygen during the aerobic decomposition of organic wastes of waste water so BOD has an inverse relationship with the dissolved oxygen (DO). So in a highly polluted water body, there is very high BOD and very low DO which generally causes health of a large number of aquatic animals especially the fish which disturbs food chains, food web and productivity of aquatic ecosystem.
Chemical Oxygen Demand (COD) is the amount of oxygen required to oxidise all the pollutants (both biodegradable and non-biodegradable) in one litre of waste water at 20°C in five days. The value of COD is always higher than BOD.
2. Industrial Effluents:
Industries usually discharge waste water into ponds, lakes and rivers. Industrial waste water contains heavy metals as mercury, lead, copper, arsenic and cadmium. Other inorganic pollutants are the acids, alkalies and bleaching liquors.
Some organic pollutants are:
(i) Phenol,
(ii) Naphtha,
(iii) Proteins,
(iv) Cellulose fibres,
(v) Aromatic compounds, and
(vi) Putrescible organic matter.
Some of these chemicals are carcinogens. Industrial effluents are the most hazardous pollutants on land and water. Main sources of mercury are combustion of impure coal, thermal power plants, chloralkali industries producing caustic soda, thermometers, blood pressure instruments, smelting of metallic ore, paper and paint industries.
The sources of lead pollution are smelters, battery industry, chemical and pesticide industries,
automobile’s exhausts, etc. Cadmium is released from electroplating, pesticide and phosphate industries. Other industrial pollutants include copper, nickel, titanium, etc.
3. Surface Run Off:
The surface run off from field of inorganic fertilizers, pesticides, insecticides, manures bring heavy loads of pollutants into natural water bodies. Pesticides like DDT are non-degradable.
Fertilizers include nitrates, phosphates and sulphates of potassium. They may reach the ground water through leaching or may be carried to rivers, lakes and ponds.
Effects of Surface Run-Off:
(a) Excess of nitrates from fertilizers run down into ponds, lakes, streams etc. It leads to thick blooms of algae. As a result, plenty of oxygen is used from water by these algae. This leads to suffocation of aquatic organisms. The increased productivity of lake and pond etc. due to this nutrient enrichment is called cultured or accelerated eutrophication or algal blooming.
(b) Biomagnifications. Explained ahead under separate heading.
(c) Water becomes unfit for drinking, industrial and recreational purposes etc.
(4) Thermal Pollution:
It is rise in temperature of water through human activity. Thermal power plants, refineries etc. discharge hot water into nearby lake, sea etc. The sudden rise in temperature of water has very harmful effects on the aquatic organisms such as fish and algae.
Effects of Thermal Pollution in Water:
(a) Warmer water has less oxygen (14 ppm at 0°C, 1 ppm at 20°C), so thermal pollution causes deoxygenation of water bodies which decreases the decomposition of organic wastes and kills the aquatic animals.
(b) Trout eggs fail to hatch while Salmon does not spawn at higher temperature.
(c) High temperature denature enzymes, decreases photosynthesis rate so decreasing the primary productivity.
5. Radioactive Pollution:
Discussed in Radioactive pollution.
This shows that although 71 per cent of the earth’s surface is covered by water, there are strong signals of a global water crisis in the near future. Water wars are predicted between the nations and a time may come when this prime natural resource could cost more than petrol.
Essay # 4. Ill Effects of Water Pollution:
A. Effects of Organic Wastes and Domestic Sewage:
1. Micro-organisms use the oxygen in decomposition of these organic wastes so causing deoxygenation of water which stimulates the algal blooming.
This anaerabiasis produces foul smell in water bodies and makes it unfit for human consumption.
2. Domestic sewage stimulates the activity of decomposer like bacteria (e.g. Sphaerotilus, Beggiatoa, Escherichia, etc.); fungi (Mucor, Fusarium, Leptomilus, etc.); Oscillatoria and other blue-green algae; green algae (e.g. Chlamydomonas, Cladophora, etc.); sewage-tolerant plants (e.g. Fontinalis antipyretica—a moss and angiospermic Potamogeton); bacteria-eating protozoans (e.g. Paramecium, Colpidium, Glaucoma, etc.).
3. Organic wastes form a scum and sludge in polluted water which becomes unfit for industrial uses.
4. Phosphates of detergents (may be upto 40%) further stimulate the algal growth called eutrophication.
5. Pathogen-contaminated water is known to cause a number of infectious diseases like cholera, jaundice, typhoid, dysentery, hapatitis, etc. According to Central Water Health Engineering Institute, 60 persons out of 100,000 die every year due to typhoid, dysentery, etc. which are caused by polluted water.
B. Effects of Industrial Wastes in Water:
1. Compounds like mercury, arsenic and lead are neurotoxic in nature e.g. chronic exposure to arsenic causes black foot disease. Arsenic causes diarrhoea, peripheral neuritis, lung and skin cancers, etc. Mercury as well as methyl mercury are neurotoxins and can cause memory loss, impaired coordination and vision disorders.
2. Minamita disease in Japan in 1952 appeared due to consumption of mercury-contaminated fishes of Minamita Bay. It is characterized by numbness of limbs, lips, blurring of vision, apathy and mental disorder and genetic changes.
3. The asbestos fibres cause asbestosis, a kind of lung cancer (in 1970).
4. Cadmium pollution was found to cause Itai-itai disease in Japan due to consumption of Cd-contaminated rice. It is characterized by bone disorder and cancer of liver and lungs.
5. Nitrates (in excess than 90 ppm) are known to cause cyanosis or blue babies.
6. Excess of nitrates in drinking water may cause methaemoglobinemia. Nitrate converts haemoglobin to methaemoglobin-oxidised form, which is non-functional.
7. Excess use of fluoride (Fig. 16.19) toothpaste may lead to skeletal fluorosis or knock knee disease in which joints and bones become stiff and hard. Thirteen states of India have high concentration of fluoride (more than 1.5 ppm) in drinking water.
In the Unnau villages, the fluoride contents have been recorded as high as 15-19 ppm. A high dose of fluoride (100-200 ppm) causes the retarded growth. Fluorosis is characterized by chronic joint pain, arthritic symptoms and calcification of ligaments. Children barely in their teens have lost their teeth while people in their 30s look aged and withered.
8. Lead. Lead poisoning leads to the symptoms like hyperactivity, learning disability and anaemia.
9. Liquid effluents kill fish and other aquatic life.
10. Selenium causes stunted growth, loss of appetite and digestive disorders in animals.
National Environmental Engineering Research Institute (NEERI) is located at Nagpur.
Biomagnification:
Biological magnification, also called biological concentration or biological amplification, is characterized by the increase in the substances in successive trophic levels of a food chain (Fig. 16.20).
Pesticides are the chemicals used to kill the plant and animal pests. These include bactericides, fungicides, nematicides, insecticides, rodenticides and herbicides (or weedicides). Now these are collectively called biocides. Most of biocides are non-biodegradable and toxicants. According to WHO survey, more than 50,000 people in developing countries are annually poisoned and 5,000 die as a result of the effects of toxic chemicals being used in agriculture.
These biocides show biomagnification. Some of the most toxic biocides are DDT (Dichloro-Diphenyl Trichloroethane), BHC (Benzene Hexachloride), chlordane, heptachlor, methoxychlor, aldrin, endrin and PCBs (Polychlorinated biphenyls).
Indiscriminate use of biocides could result in bio-magnification as shown below:
C. Effects of Biomagnification:
1. DDT interferes the egg-shell formation in many birds. The shells remain thin and break by bird’s weight during incubation. Dieldrin is about 5 times more toxic than DDT when ingested and 40 times more poisonous when absorbed.
2. These chlorinated hydrocarbons are known to affect CNS, cause softening of brain, cerebral haemorrhage, cirrhosis of liver, hypertension, cancer, malformation of sex hormones, etc.
3. Biomagnification of mercury into fishes through the food chain was responsible for large number of deaths due to Minamita disease in Japan in 1952. Mercury compounds in waste water are converted by bacterial action into extremely toxic compound methyl mercury, which causes numbness of limbs, lips and tongue, deafness, blurred vision, mental retardation, etc.
4. Selenium accumulates in the plants growing on selenium-rich soils. Through food chain, such plants cause stunted growth, loss of appetite gastro-intestinal disorders, etc. in the animals grazing on such plants.
Essay # 5. Control of Water Pollution:
1. Treatment of Waste Water (Fig. 16.21):
The sewage is taken to sewage treatment sites. In this, industrial and municipal waste waters are treated in Effluent Treatment Plant (ETP) before their discharge in water bodies.
In ETP waste water is given following treatments:
(a) Primary Treatment:
In this method mechanical screening and sedimentation of undissolved solids in raw sewage (e.g. large lumps of organic matter, sand and silt) is done. It fails to remove any dissolved substance in water. It does not remove the pathogens.
(b) Secondary Treatment:
Sewage treated in primary treatment is brought in contact with oxygen and aerobic micro-organisms. They breakdown the organic matter into harmless materials as CO2 and H2O. Further, chlorination is done to kill the bacteria. It may be further treated to tertiary level.
Two measures are adopted for secondary treatment:
(i) Trickling filter method. In this case, sewage water passes through a thick bed of gravel stones so that bacteria consume most of the organic matter.
(ii) Activated sludge method. In this, sewage water is pumped into an aeration tank which contains sludge (consisting of bacteria and algae). The bacteria are able to decompose most of the organic matter while algae provide oxygen to these decomposers. But the water still carries large amounts of nitrates, phosphates, etc.
(iii) Advanced waste management or tertiary treatment. In this, salts like nitrates and phosphates are removed by precipitation technique. Water is now pure enough to drink.
2. Recycling of Wastes:
Gobar gas plant can be used for prevention and control of water pollution and to recycle the various kinds of waste products.
Some other recommended methods are:
(a) Composting kills most of the pathogens and also ripens the dung into manure.
(b) From jute wastes, hardboard can be prepared.
(c) Coconut and other agricultural wastes can be used for the manufacture of paper and board.
3. Controlled use of pesticides and fertilizers. Minimum amounts of pesticides should be applied so that no surplus remains in the soil. Only less stable compounds should be used in manufacturing biocides.
4. Reverse osmosis. By this technique, brackish water is demineralised by pumping it through a semipermeable membrane under strong pressure.
5. Thermal pollution can be checked by employing heat or dry cooling towers (Fig. 16.23).
6. Water hyacinth removes biological and chemical pollutants. It also removes heavy metals like Cd, Hg, Pb and Ni.
