About 90 per cent of fresh water available in nature is frozen in the form of snow, whereas only 10 per cent of fresh water is available for use of human beings.
If this whole water deposit remains at its original qualitative level, water crisis cannot arise, but even 10 per cent part of this fresh water (2.70% of total water in nature) is not free from pollution.
Rivers, lakes, tanks and underground water are continuously becoming polluted.
Oceanic water, in spite of being saline, necessarily has to remain free from pollution because the water is used not only for drinking purposes but it indirectly also maintains all living organisms. Hence, the whole water deposit in nature should remain free from pollution. Human activities are extending day by day, due to which existing sources of water on the surface of the earth are getting polluted. Apart from oily pollution in oceans, disposal of effluents is made in large quantity every year in Coastal areas.
In important industrial countries of the world, including India, waste is disposed of by big cities habited on banks of rivers and at the same time waste from industrial plants is polluting river water. Two-third portion of the water of rivers Ganga, Yamuna, Godavari, Kaveri (Cauvery), Damodar, Hooghly etc. is not fit for human consumption due to disposal of polluting elements emitted by industrial plants located on the banks of these rivers in India. The Ganga enters in plain areas after Haridwar and thereafter up to Allahabad its water is not fit for human consumption.
What is Water Pollution?
At any place on the earth, deterioration of water due to inclusion of undesirable outside elements in water deposit is called water pollution. Water is available from different sources in nature and its physical and chemical composition is also different. Oceanic water is saline which cannot be directly used for human consumption but it does not mean that oceanic water is polluted because quality of water is not only assessed from the point of view of human consumption but also from the angle of use by all living organisms.
Hence, oceanic water is not polluted in spite of being saline. Saline water has its own ecological system which cannot be maintained by fresh water. Thus in the natural context, the water existing in its original form with its physical and chemical composition necessary for various biological communities, is free from pollution but when undesirable outside elements from natural and artificial sources mix in it, then it is called polluted water. Polluted water becomes poisonous and quantity of oxygen is reduced as compared to normal water. Therefore, the water becomes disease bearing rather than remaining nutritive.
Water pollution is change in physical, chemical and biological qualities of water due to human reasons and therefore such water becomes harmful for public health, since they become disease bearing, making them unfit for drinking by human beings and animals, and also various uses in industries, agriculture and other uses. While defining water pollution, G.S. Southwick (1976) has written that “the change in chemical, physical and biological qualities of water due to human activities and natural processes is called water pollution.”
Normally, it can be said that interference by natural and human elements in quality of balanced water necessary for organisms living on the surface of the earth causes deterioration, which causes water pollution and therefore such water does not remain fit for use by those living organisms. Its effect is becoming visible on the surface level water sources and seas in present times.
Types of Water Pollution:
Nature and forms of water pollution are related to many factors, based on the factors which cause pollution of water, pollution of water can be of four types:
1. Sewerage Pollution
2. Domestic Waste Water Pollution
3. Industrial Waste Water Pollution
4. Solid Waste Water Pollution
Similarly based on its nature also, it is of four types:
1. Physical Pollution:
This causes change in smell, temperature, colour, density, taste and warming qualities in the water.
2. Chemical Pollution:
Due to chemical elements and layers mixing in water due to different industries and other sources water gets polluted.
3. Physiological Pollution:
It is after such changes in qualities of water, harmful effect on human processes is caused.
4. Biological Pollution:
Biological pollution is caused by harmful water organisms entering from various sources in water. Among such organisms, the main are Bacteria, Conform, Algae and Virus etc. Normally, quality of water is decided on the basis of biological demand for oxygen and chemical oxygen, dissolved oxygen and pH value.
Classification of water pollution is normally made on the basis of sources of water as under:
1. Surface Water Pollution:
Water is found in rivers, lakes, tanks and other micro places on the surface of the earth. On the surface level sources of water are rainfall and melting of snow. Different ions are found in rainwater. Other water sources contain sodium, chlorine, calcium, sulphate, magnesium and potassium ions. These ions from natural sources enter the atmosphere through oceanic water and they reappear on the earth with rain water. Apart from them, surface water is also polluted by lead, zinc, mercury, cadmium, asbestos etc.
Health, Education and Welfare Department of United States of America (HEWD) has divided surface water pollutants in the following eight categories:
1. Brewery and industrial waste
2. Plant nutritive elements and dissolved elements
3. Infectious factors (insects and virus)
4. Molecules and granules
5. Chemical elements
6. Effluented heat
7. Radioactive elements
8. Biochemical elements etc.
In every field different types of techniques are fast developing in the world. Due to industrialization and urbanization, 2,500 chemicals per year are damaging the pure surroundings resulting in pollution of surface water sources. The effect of this polluted water clearly is visible.
Very soon adverse effects of pollution would appear which would be a question mark on the existence of human beings and other living organisms. In efforts to grow more foodstuffs to maintain the population that is increasing at a fast rate, insecticides are being used in agriculture. Many chemical insecticides are also polluting surface water sources. Due to the activities of human beings, lakes are also becoming polluted along with rivers.
They are also being affected by deforestation, since sedimentation is being caused in lakes because of soil erosion. In addition, many wastes reach lakes because of surface flows. Due to effluent from breweries and industries established in vast cities located on the banks of lakes, lake water is losing its quality. Many chemical substances disposed by agriculture also spread pollution in them.
2. Oceanic Water Pollution:
Industries developed in coastal area of seas and cities developed there also spread pollution through disposal of waste. Brewery effluent and poisonous chemicals like mercury are the main waste materials among them. Unplanned disposal of waste in coastal cities is causing deterioration of quality of oceanic water.
This directly affects the biotic life in seas. Coral and fish biotic life are struggling for their existence but man is ignoring this problem because of his own economic development and self interest, which is having dangerous results.
Due to navigation in seas leakage of mineral oil from oil transporting ships is also causing pollution. Every year about 295 million gallon mineral oil is mixing with sea water due to oil leakage. Apart from this, leakages in sea oil wells and fire have also increased pollution. During wars, while using mineral oil for military purposes, some part mixes in sea water. Sometimes, damaged oil transporting ships also pollute water. Thus, a dangerous ecological crisis is arising from oceanic water pollution.
3. Groundwater Pollution:
Groundwater pollution is considered as an important part of water pollution. It is caused by agricultural waste, effluent from chemical substances from industrial areas, and urban and rural waste disposal. All such disposed waste mixes with surface water and pollutes underground water. Similarly, agricultural waste percolates by leaching at the time of irrigation.
The increasing population in urban as well as rural areas also disposes off their waste by unscientific methods and in an unplanned manner at any place they like. This goes underground after mixing with rain water. Besides this, the pollution in water deposits situated on the surface of the earth like lakes, tanks and baoris, pollutes underground water by infiltration. Nature of aquifers also affects pollution. Polluted water of upper layers stagnates in many aquifers, affecting the quality of groundwater in such areas.
Wells and hand pumps also pollute underground water. Poisonous chemical effluents disposed of by factories nearby wells pollute groundwater by infiltration. Similarly, in wells located near coastal areas of seas, due to over exploitation of groundwater some hollow spaces are created in which polluted oceanic water enters, polluting underground water. Thus, groundwater is being polluted by different sources at a fast rate. Its effects are gradually becoming visible.