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Essay on Water Pollution!
Water pollution may be defined as deterioration of physical, chemical and biological characteristics of water through natural and anthropogenic activities to such an extent that it becomes harmful to human beings, plants and animal communities.
1. Importance of Water
2. Sources of Water
3. Uses of Water
4. Water Pollution
5. Sources of Water Pollution
6. Types of Water Pollutants
7. General Effects of Water Pollution
8. Classification of Water Pollution
9. Water Quality Parameters and Standards
Chemically speaking, water is a simple inorganic covalent molecule. It is formed, when hydrogen is burnt in oxygen or an electric spark is passed through a mixture of hydrogen and oxygen gas in the ratio 2: 1 (Vol. to Vol.)
2 H2 + O2 → electric spark 2H2O
As regards to its physical state, it exists in three different states:
(a) Water liquid (Common water).
(b) Water solid (Ice).
(c) Water gas (Water vapour).
All these three physical states are inter-convertible and these depend upon the temperature.
1. Importance of Water:
Water is indispensible for sustenance of ail living organisms because of its several unique properties which are discussed below:
1. Universal Solvent:
Water is capable of solubilizing varieties of substances. By such a process a number of nutrients and ions can be transported into plant body.
2. Higher Specific and Latent Heat (Thermal properties):
Because of its higher specific heat, it can store a large quantity of thermal energy with a comparatively smaller rise in its own temperature. Such a storing of thermal energy is essential for the living organisms in water. Besides, it has a higher value of latent heat i.e. it requires large amount of heat for changing from ice to water and also it liberates large amount of heat for changing from water to ice.
3. Higher Viscosity:
Because of its higher viscosity, it protects the aquatic organisms against mechanical disturbances and helps the swimming and floating of living aquatic animals.
Since water is transparent, it allows the effective penetration of light whereby the submerged aquatic plants are able to photo-synthesize.
Pressure exerted by water at a particular depth modifies the shape and size of aquatic organism.
Water has this unique property which helps the aquatic organisms to float over its surface.
2. Sources of Water:
The fresh water required by man is obtained from two natural sources:
(a) Ground Water; and
(b) Surface Water.
(a) Ground Water:
Water present under the surface of the earth is known as ground water. The average magnitude of the total ground water content is about 210 billion m3 including recharge through infiltration, seepage and evapo-transpiration.
The storing of ground water takes place by the following mechanisms. The inter-molecular spaces between the soil particles are sufficient enough to allow the rain water molecules to pass through them. These water molecules get collected at different zones giving sub-surface water or ground water.
The spaces remaining in between soil particles are known as voids. Similarly, a part of the river water or streams can pass through the voids giving ground water. The ground water is usually of good quality and free from extraneous pollutions. So it can be used for drinking and for our day-to-day use.
It can be withdrawn for human consumption by the following ways:
(i) Wells (dug-well or bore-well);
(ii) Spring intake chamber; and
(iii) Infiltration galleries.
(b) Surface Water:
Water present over the surface of earth in rivers, lakes, ponds, seas and oceans is known as surface water. Water remains in solid state as ice near the poles or near the cold places where the temperature is below 00 C.
The humanity is largely dependent upon the surface water for day-to-day uses. The surface water contains a lot of pollutants, micro-organisms and mineral nutrients for the feeding of bacteria and virus. The surface water gets polluted by the run of water from agricultural Fields containing pesticides and fertilizers, soil particles, waste chemicals from industries and sewage from cities and rural areas. However, the surface water can be purified and reused.
The composition of water obtained from different sources is shown in Table 8.2.
Table 8.2: Chemical composition of ground water, river water and sea water
3. Uses of Water:
The water can be used for different purposes as mentioned below:
(i) Domestic use for drinking, cooking and cleaning, etc.
(ii) Irrigation for agriculture.
(iii) Power generation.
(iv) Industrial use for cooling, processing, cleaning, etc.
(v) For fisheries and acqua-culture.
(vi) For navigation.
(vii) Waste disposal.
4. Water Pollution:
Water is the most important constituent of the life support system because on one hand it is vital for the maintenance of all forms of life and on the other it helps in the movement, circulation and cycling of nutrients in the biosphere. Water is essential for power generation, navigation, irrigation of crops, disposal of sewage etc.
It may be noted that only one per cent of the total quantity of water of the hydrosphere is available to human beings and other biotic communities from various sources such as ground water, rivers, lakes, atmosphere and biological systems.
Coupled with population explosion, rapid industrialisation and unplanned urbanisation, are releasing a lot “of waste into water bodies thereby degrading the quality of water. Though water like other natural substances has self purifying capacity during recycling processes but when the foreign undesirable substances added to it exceed the tolerance level and self-purifying capacity of water, it gets polluted.
Thus water pollution may be defined as deterioration of physical, chemical and biological characteristics of water through natural and anthropogenic activities to such an extent that it becomes harmful to human beings, plants and animal communities. According to United States Public Health Services, water pollution means “the presence of any toxic substance in water that degrades the quality to constitute a hazard or impair its usefulness.
Water pollution may also be described as extraneous enrichment of chemicals which alter the physico-chemical environment changing the community composition and compelling some species or many species to disappear from the natural eco-system. The results of water pollution are evident whether measured by harms to the living resources or hazards to human health or reduction of immunities.
Anyway, water pollution is a global problem affecting both developed and developing countries. Human activities related with water pollution comprised mining, agriculture, stockbreeding, fisheries, urban human activities, various industries, such as manufacturing industry, domestic sewage etc.
5. Sources of Water Pollution:
Depending upon the specificity of waste discharge, the water pollution sources are categorised as:
(a) Point sources
(b) Nonpoint or diffused sources.
(a) Point sources:
Point sources are those which discharge pollutants from some specific location (such as pipeline, ditches and sewers) into water bodies.
Some common point sources of water pollution include:
(ii) Sewage treatment plants,
(iv) Hazardous waste sites;
(v) Leakage from oil storage tanks.
The pollutants from point sources are of definite identity with almost a fixed volume and composition. The level of pollution can be controlled by suitable experimental modulation.
(b) Non-point or diffused sources:
Non-point sources of water pollution are widely scattered and discharge pollutants over larger areas.
Some common nonpoint sources of water pollution are:
(i) run off from agricultural fields;
(ii) live-stock feed lots;
(iii) Storm run off from urban streets; and
(iv) parking lot and streets into surface water and seepage into ground water.
It is difficult and expensive to identify and control the discharges from non-point sources. It may be noted that major pollution involve non-point source pollution.
6. Types of Water Pollutants:
Water pollutants may be classified into the following categories:
1. On the Basis of Pollutant Sources:
Water pollutants are divided into the following classes on the basis of pollutant sources:
(a) Industrial pollutants:
Different industrial pollutants include chlorides, sulphides, carbonates, nitrites, nitrates of heavy metals such as mercury, lead, zinc, arsenic etc., organic compounds synthesized for industrial purposes, radioactive wastes etc.
(b) Agricultural pollutants:
These are chemical fertilizers pesticides, insecticides and herbicides, synthetic chemical compounds, weeds and plant remains.
(c) Urban pollutants:
These contain chemicals from automobile exhaust, chemicals from lime and chemical fertilizers used in the lawns and gardens within city, chemicals from urban sewage, household sewage etc.
(d) Natural pollutants:
The natural pollutants include volcanic dusts, sediments due to weathering and erosion, debris caused by landslide, decayed and decomposed organic matter etc.
2. On the Basis of Physical and Chemical Characteristics:
On such a basis, water pollutants are divided into two categories:
(a) Physical pollutants:
Pollutants changing the physical characteristics such as colour, taste, turbidity, sediments, oil and grease content, dissolved and suspended solid etc.
(b) Chemical pollutants:
These are chlorides, sulphites, sulphates, sulphides, carbonates, nitrates of heavy metals like mercury, lead, cadmium etc., pesticides, herbicides, insecticides and several other chemical compounds.
3. On the Basis of Degradation Nature:
On such basis, water pollutants are of two types:
(a) Degradable pollutants; and
(b) Non degradable pollutants.
(a) Degradable pollutants:
These pollutants can be broken down by biological means such as decomposers or microorganisms. Such pollutants are also known as organic pollutants, e.g. leaf litters, sewage, garbage, plants and animals.
(b) Non-degradable pollutants:
These pollutants cannot be degraded by biological means. These are also known as inorganic pollutants, e.g. chemical pollutants and solid toxic substances.
7. General Effects of Water Pollution:
Water pollution induces irreparable damage to all types of living organisms including man.
Some detrimental effects of water pollution are outlined below:
1. Polluted water is the major cause for the spreading of epidemics and several dreaded diseases like cholera, tuberculosis, jaundice, dysentery, typhoid etc.
2. The consumption of water contaminated by fibres as asbestos causes lung cancer and stomach diseases called Asbestosis.
3. The consumption of water contaminated with mercury causes Minamata disease.
4. The polluted water contaminated with toxic chemicals causes death of aquatic organisms (both plants and animals).
5. Polluted water damages crops and decreases agricultural productivity.
6. Heavily polluted water decreases soil fertility and kills soil micro-organisms.
7. Polluted water containing basic salts increases alkalinity of the soil.
8. Increase in the concentration of inorganic and organic nutrients in water bodies causes eutrophication which leads to rapid growth in population of plants and animals beyond controllable unit.
9. Contamination of sea water due to oil slicks resulting from leakage of crude oil from huge oil tankers and due to discharge of industrial and urban wastes causes ecological disasters in littoral eco-systems because of mass death of sea organisms.
8. Classification of Water Pollution:
On the basis of sources and storage of water, water pollution nay be divided into the following categories:
1. Ground water pollution;
2. River water pollution;
3. Lake water pollution; and
4. Sea water pollution.
1. Ground Water Pollution:
Ground water (which lies below the surface of earth) acts as very good reservoir by virtue of large pore space in earth materials, as a Conduit which can transport water over long distances and as a mechanical filter which improves water quality by removing suspended solids and bacterial contamination. It is the recommended source of rural domestic use which is replenished by precipitation through rain, snow, slit and hail. The composition of ground water is given in Table 5.2.
In order to meet the high demands of increasing population there is continuous and non-interrupted interactions in between humanity and environment along with release of a lot of extraneous materials (wastes). These extraneous materials (wastes) are constantly added into ground water reservoirs at an alarming rate causing the pollution of ground water. Once the ground water is polluted, it is difficult to restore the original water quality of the aquifer.
The extent of ground water pollution depends on the factors like rainfall pattern, depth of water table, distance from the source of contamination, soil properties (like structure, texture and filtration rate).
(A) Sources of Contamination of Ground Water:
Ground water is threatened with pollution from the following sources:
1. Industrial wastes:
The hazardous effluents released from industries, contain toxic heavy metals, ions and a number of organic and inorganic species. These contaminate the ground water and severely pollute it.
2. Agricultural wastes:
Excessive use of fertilizers, pesticides, insecticides, herbicides etc add a lot of chemical to ground water. Besides agricultural processing wastes and animal wastes are also significantly polluting ground water.
3. Domestic Wastes:
The primary factors responsible for deteriorating the ground water quality are pathogenic organisms, oxygen demand, nutrients and solids from domestic wastes.
4. Run-off from urban areas:
Rapid urbanisation releases a lot of effluents which contains large concentration of oils, greases, nutrients, heavy metals and detergents. The detergents being soluble can pass through the soil and pollute ground water.
5. Soluble Effluents:
Soluble effluents can easily pass through and pollute the ground water. The extent of pollution is more prominent in sandy soils and humid regions having high water table condition.
Other sources of ground water pollution may include:
(a) Earthen septic tanks;
(b) Seepage pits;
(c) Barnyard manures;
(d) Urban and rural garbage’s;
(e) Mine spills;
(f) Refuse dumps;
(g) Leaching and downward movement of pollutants.
(B) Detrimental Effects of Ground Water Pollution:
(1) Effects on human beings:
(i) Polluted ground water helps in spreading of epidemics and chronic diseases like typhoid, jaundice, dysentery, diarrhea, hepatitis etc.
(ii) Polluted ground water contaminated with toxic metals like Hg, Pb, Cd, Cr, Cu, etc. and cyanides causes stomach and skin diseases in man.
(iii) Polluted ground water contaminated with fibers (i.e., asbestos) causes fatal diseases like asbestosis and lung cancer.
(iv) Polluted ground water containing more than 0.3 ppm of iron becomes extremely harmful for drinking purpose.
(2) Effects on Plants:
(i) Polluted ground water disturbs plant metabolism severely and hence, has adverse effect on ecosystem.
(ii) Contaminated ground water increases acidity or alkalinity of the soil.
(iii) Polluted ground water decreases soil fertility by killing bacteria and micro-organisms.
(iv) Polluted ground water used for irrigation purpose severely damage crop productivity.
(C) Control of Ground Water Pollution:
The level of pollutants in ground water can be minimised by the following manner:
1. The contaminant water sources should be carefully surveyed.
2. The toxic industrial effluent should be properly treated before their disposal.
3. The location of wells for drinking water supplies should be decided with utmost caution.
4. The uppermost aquifier should not be tapped for drinking water wells.
5. The location of industrial and municipal disposal sites should be carefully selected keeping in view the ground water level and flow pattern in the area.
2. River Water Pollution:
River water is one of the forms of surface water. It usually contains ions like chloride ion
(Cl–), sulphate ion (SO2-4), sodium ion
(Na+), Magnesium ion (Ng+), Calcium ion (C 2+ a)’ Potassium ion
(K+) etc. in those areas which are free from industrial and urban influences. When concentrations of these ions exceeds their threshold values due to exogenous addition of effluents from industries, discharges of urban sewages, discharges from agricultural Fields etc. The river water gets polluted and causes a number of potential hazards to living organisms. Some Indian rivers and their major sources of pollution are given in Table 8.3.
(A) Sources of River Water Pollution:
The chief sources of river water pollutions are as follows:
1. Discharge from urban sewage water.
2. Industrial effluents carrying industrial waste water.
3. Washing and dumping of industrial solid wastes.
4. Non degradable and long lasting pollutants from tanneries.
5. Wastes from sugar factory, beet-sugar refining, meat packing, distilleries.
6. Agricultural wastes containing fertilizers, insecticides, fungicides, etc.
7. Decomposed plants and animals.
8. Radioactive materials.
9. Surface run-off.
10. Atmospheric gases.
11. Acid rain containing sulphuric acid, nitric acid etc.
The nature and extent of river water pollution depends on a number of factors, few of which may be outlined as follows:
(i) Hygienic and health situation of communities residing near river.
(ii) Physical, chemical and biological characteristics of waste water entering into river.
(iii) Vegetation, soil type and degree of weathering of rock.
(iv)Waste water disposal system and technique.
(v) Extent of internal mechanism to cause self purification.
(vi) Hydrological characteristics of diluting biocides.
River pollution takes place mainly in two ways:
(1) Through point source;
(2) Through non-point sources.
The point source includes discharge of urban sewage drains and industrial effluents at specific points into rivers. The Mon- point sources involve discharge of pollutants, mainly from agricultural fields through surface run-off.
(B) Types of River Water Pollutants:
According to U.S. Department of Heath, Education and Welfare (HEW), river water pollutants are classified into eight types:
1. Sewage and Waste:
It includes a number of chemical substances brought down by the sewage drains of urban and industrial areas.
2. Infectious agents:
These include germs and viruses which cause several diseases.
3. Plant nutrients and dissolved substances:
These are chemical fertilizers.
4. Particulate matters:
These are soil and mineral particles.
5. Mineral and Chemical substances:
These include salts, acids, alkalis, oil, grease etc.
6. Organic chemical exotics:
These include synthetic materials like pesticides, insecticides, herbicides, rodenticides etc.
7. Radio active substance.
(C) Detrimental Effects of River Water Pollution:
Same as ground water pollution.
(D) Control of River Water Pollution:
The level of pollutants in river can be minimised by adopting the following procedures:
1. The contaminant water sources should be properly surveyed.
2. The toxic industrial effluents and urban sewage wastes should be properly treated before their disposal.
3. The use of biofertilizers should be given preference over chemical fertilizers.
4. The use of pesticides, insecticides, herbicides, rodenticides etc. should be minimised.
3. Lake Water Pollution:
In addition to ground water pollution and river water pollution, water masses in different lakes are also under going pollution due to rapid industrialisation and unplanned urbanisation. The pollution of lake water also causes a number of hazards to both plants and animals including human beings.
(A) Sources of Lake Water Pollution:
The lake water is polluted by the following sources:
1. Toxic and hazardous effluents from industries.
2. Surface run off, rivulets and streams bringing inorganic nutrients from agricultural fields.
3. Waste sludge’s from factories as well as washings and dumping of tailings.
4. Siltation of lakes due to dumping of enormous quantities of sediments.
5. Discharge of organic wastes from hills and toxic effluents from urban areas.
6. Decomposed plant and animal matters.
7. Wastes from house boats, hotels and homes.
8. Illegal constructions and building materials.
9. Excess quantity of excreta from migratory birds.
10. Eutrophication: The abundance of nutrients causes uncontrolled growth of plants and animals.
11. Acid rain
(B) Detrimental Effects of Lake Water Pollution:
Same as those of ground water.
(C) Control of Lake Water Pollution:
In order to control the level of pollutants in lake water, the following preventive measures should be adopted:
1. The contaminant water sources should be properly surveyed-
2. The toxic industrial effluents and urban sewage wastes should be properly treated before their entry into lakes.
3. Visitors should be advised not to add non-degradable pollutants into lakes.
4. The lake sites should be properly cleaned time to time.
Natural Water and Its Quality:
Water is one of the abundantly available resource which is an essential ingredient of animal and plant life. It is distributed in nature as rain water, river water, spring water, ground water, sea water, lake water etc.
Rain water is considered to be the purest form because it is produced by the process of natural distillation. However, it may be associated with dissolved gases like C02, S02, NH3 etc. in urban and industrial areas. The rain water in hilly areas and snow melting’s of mountains flow in the rivers. The original river water is pure but as it flows through the planes towards the sea, it gets polluted due to the addition of industrial effluents, agricultural run-off, urban sewage etc.
The natural water usually contains three types of substances:
1. Ion dispersed substances (inorganic substances)
2. Colloidal and molecular substances.
3. Suspended particulates.
1. Ion dispersed substances:
Naturally occurring water contain ionic compounds like CaCl2, MgCl2, CaSO4, MgSO4 Ca (HCO3)2, Mg (HCO3)2, Ha2SO4 and NACI in their ionic forms. Sometimes, the natural water is also associated with NH4+ (ammonium ion), NO3_ (nitrate ion), NO2– (nitrite ion) and HNO3 (nitric acid). The presence of nitrogen containing ions in water indicates that water is polluted.
2. Colloidal and Molecular Substances:
Substances of both organic and inorganic origin are present in water in colloidal state.
The contamination of natural water by organic substances may be due to:
(a) Dying of and decaying of organisms dwelling in water;
(b) Industrial discharges. The inorganic substances in colloidal forms are the compounds of silicon, aluminum and iron.
3. Suspended particulates:
The suspended particulates include the particles of sand and clay of different size, remnant of plants and other substances retrained from the surface. The greatest concentration of such substances in surface waters is usually observed during flood.
Some important functions of water in regulating the physiological activities in human beings may be outlined as follows:
(a) It acts as a regulator of body temperature.
(b) It acts as a carrier of nutrients to tissues and removes waste materials from them.
(c) It maintains electrolyte balance of the body by the maintenance of osmotic pressure.
(d) It acts as a solvent for the secretory and excretory products.
All the characteristics functions of water are due to:
(i) The amphoteric nature of water.
(ii) The tendency of water to solubulise a wide spectrum of compounds.
(iii) The tendency of water molecules to form intermolecular hydrogen bonding.
The total body water constitutes about 60% to 70% of body weight.
9. Water Quality Parameters and Standards:
Based on criteria and requirement, quality standards are prescribed which indicate the current state of knowledge of various constituents present in water. Since the quality standards are continuously revised with up to date information’s about the effects of constituents on proposed uses, these should not be used as absolute limits. However, these can be used as guidelines for preliminary judgments.
The specific purpose for which the water is used usually controls the requisite water quality. For example, water used in food industries will need to meet standards similar to drinking water but water for industrial operations can contain much higher concentrations of impurities.
The parameters for water quality characterisation are listed in Table 8.4. The permissible limits prescribed by United States Public Health Drinking Water Standards (UPSH) and Indian Standard Institution (ISI) are listed simultaneously for comprison. These refers to domestic water supplies for drinking water.
Table 8.5 illustrates the water quality characteristics of natural water that have been used as a source for various industrial operations.
Table 8.6: Raw Water Standards (Maximum Concentration of Constituents In Raw Water Supplied For Various Industries, MG/1. (Lamb, 1985; Clark Etal., 1977).