WATER POLLUTION
Dozens of times a day those of us who live in the industrialized nations of the world enjoy a blessing denied to 75% of the world population: abundant supply of clean water. Because, water is essential for life on earth. No known organisms can live without it. For centuries water has been used as a dumping ground for human sewage and industrial wastes. Added to them are the materials leached out and transported from land by water percolating through the soil and running off its surface to aquatic ecosystems. Thus the term water pollution refers to "Water contamination by a variety of chemical substances or eutrophication caused by several nutrients and fertilizers (Southwick,1976)." U.S. Department of Health Education and Welfare defines water pollution as "The adding to water of any substance, or the changing of water's physical and chemical characteristics in any way which interferes with its use for legitimate purposes."
Origin of Wastewater
Wastewaters can be classified by their origin as domestic wastewater and industrial wastewater. Any combination of wastewater that is collected in municipal sewers is termed as municipal sewage. Domestic wastewater is that which is discharged from residential and commercial establishments, whereas industrial wastewater is that which is discharged from manufacturing plants. The pollutants in domestic wastewater arise from residential and commercial cleaning operations, laundry, food preparation, body cleaning functions, and body excretions. The composition of domestic wastewater is relatively constant.
Industrial wastewater is formed at industrial plants where water is used for various processes, and also for washing and rinsing of equipment, rooms, etc. These operations result in the pollution of the products and byproducts are discharged, either deliberately or unintentionally into them.
Normally, wastewaters are conducted to treatment plants for removing undesirable components which include both organic and inorganic matter as well as soluble and insoluble material. These pollutants, if discharged directly or with improper treatment, can interfere with the self-cleaning mechanisms of water bodies. The capacity for self-cleaning is due to the presence of relatively small numbers of different types of micro-organisms in the water bodies. These microorganisms use as food much of the organic pollutants and break them down into simple compounds such as CO₂ or methane, and the micro-organisms produce new cells also. But often either a pollutant does not degrade naturally or the sheer volume of the pollutant discharged is sufficient to overwhelm the self-cleaning process. Also, the microbial population can be destroyed by toxic wastes build up and reach high enough levels that will prevent re-establishment of a microbial population. The water quality thus becomes permanently degraded.
Various constituents of wastewater are potentially harmful to the environment and to human health. In the environment, the pollutants may cause destruction of animal and plant life, and aesthetic nuisance. Drinking water sources are often threatened by increasing concentration of pathogenic organisms as well as by many of thenew toxic chemicals disposed of by industry and agriculture. Thus, the treatment of these wastes of paramount importance.
The major sources of water contaminatio I have been domestic, industrial, agricultural v products, solid wastes, heat and radioactiv materials.
Domestic Water Pollution
It is mainly caused by sewage. Sewage is defined as the water-borne waste derived from home animal or food processing plants and include human excreta, soaps, detergents, paper and cloth They are the largest group of water pollutants Water pollution is caused by uncontrolled dumping of waste collected from villages, towns and cities into ponds, streams, lakes and rivers. A major ingredient of most detergents is phosphate Phosphates support luxurious growth of alga Algae withdraw large quantities of oxygen from water. It becomes detrimental to other organisms. Domestic waters are the primary sources of water pollution.
The domestic sewage contributes to the largest amount of waste and it has been estimated that approximately 20,000 million litres per day reach the coastal environment of the country, Thecharacteristics of domestic sewage of Bombay is given below,
Bombay has the capacity to treat only 390 mld against 1200 mld of domestic sewage. Due to such partial sewage treatment, waste water retains the original characteristics: that result into severe damage to water quality The water quality at Bombay Harbour is mentioned below :
The huge discharge of sewage allows following events that lead to water pollution.
1. Depletion of oxygen contents. The aerobic bacteria present in water are responsible for the decomposition of organic matter. The quantity of oxygen utilized by the bacteria for the degradation of organic substance is called biological oxygen demand (BOD). Thus BOD value can be used as an indicator of water pollution. Alongwith BOD, the quantity of oxygen dissolved in a water body (DO), indicates the quality of bio-life in a water system. DO below 4 to 5 ppm is detrimental to the system.
2. Promotion of algal growth. Stimulation of heavy algal growth and shift in the algal flora to the blue green algae, leading to the formationof obnoxious blooms, floating scums or blankets of algae results into eutrophication. Most of the algal bloom do not seem to be utilized as food by the invertebrates or zooplankton, thereby, minimizing the predatory control. Biological decomposition of such algal masses in turn leads to oxygen depletion. In a poorly oxygenated condition, fish and other animal die and clean river is turned into a stinking drain.
3. Spread of infections/diseases. Micro organisms, usually viruses, bacteria, some protozoans and helminthes occur in water bodies as a result of sewage disposal. Consumption of contaminated water causes water borne infectious diseases.
Industrial Water Pollution
Pollution mainly caused by the discharge of industrial effluents into the water body is known as industrial pollution. These effluents contain a variety of inorganic and organic substances such as oils, greases, plastics, plasticizers, methylicwastes, suspended solids, phenols, pesticides. heavy metals and acids. Major industries of the country are located on or near the coastline or river sides.
(2) Inorganic substances render the water unf for drinking and other purposes.
Most of the Indian rivers and freshwater streams have been seriously polluted by industrial waste.
The discharge of industrial wastes results into the following:
(1) Organic substances deplete the oxygen content.
Table 10.5. Some Indian rivers and their major sources of pollution.
Name of the river
Kali at Mecrut (UP)
2 Jamuna near Delhi
3 Ganga at Kanpur
4 Gomti near Lucknow (UP)
Dajora in Bareilly (UP)
Damodar between Bokaro and Panchet
Hoogly near Calcutta
Sone at Dalmianagar (Bihar) Bhadra (Kamataka)
10 Cooum, Adyar and Buckinghum canal
(Madras)
Cauvery (Tamil Nadu) Godavari
12.
13. Siwan (Hihar)
14 Kulu (between Bombay and Kalyan)
15 Suwao (in Balampur)
(3) Acids and alkalies adversely effect the growth of fish and other aquatic organisms.
(4) Dye change the colour of water and affec the aquatic life.
(5) Toxic substances cause serious damage to flora and fauna.
(6) Oil and other greasy substances interfere with the self purification mechanism of water.
Source of pollution
Sugar mils: distilleries; paint, soap, rayon, silk, yam, tin and glycerine industries.
DDT factory sewage, Indraprastha Power Station. Delhi Jute, chemical, metal and surgical industries, tanneries, textile mills and great bulk of domestic sewage of highly organic nature.
Paper and pulp mills, sewage Synthetic rubber factories.
Fertilizers, fly ash from steel mills, suspended coal particles from washeries, and thermal power station.
Power station; paper pulp, jute, textiles, chemical, paint. varnishes, metal, steel, hydrogenated vegetable oils, rayon, and soap, match, shellac, and polythene industries and sewage Cement, pulp and paper mills.
Pulp. paper and steel industries. Domestic sewage, automobile work shops.
Sewage, tanneries, distilleries, paper and rayon mills.
Paper mills.
Paper, sulphur, cement, sugar mills
Chemical factories, rayon mills and tanneries Sugar industries. Sugar industriesAgricultural Water Pollution
ar pollution can be caused by agricultural sates such as fertilizers, pesticides, soil additives and animal wastes that are washed off from the and to the aquatic system through irrigation, nntall and leaching India uses about 16 kg ha of fertilizers on an average. However, average all er the world is 54 kg ha. Netherlands alone uses 709 kg ha. However, an increased use of pesticides has been observed in India from 2.8 Mt in 1975-76 to 6 Mt in 1994-95 and 9.7 Mt in 1994-95. The fertilizers are non-biodegradable. In both fresh and marine systems they enter the food chain, accumulate in non-target organisms and increase in animal tissue to alarming concentrations. They may find entry into the drinking water supplies.
Solid Waste Pollution
Solid waste varies in composition with the socio economic status of the generating community. The following materials could be classified as solid waite.
1. Garbage. Decomposable wastes from households, food, canning, freezing and meat processing operations that are not disposed off in wastewater.
2. Rubbish. All non-decomposable wastes, garden wastes, cloth, paper, glass, metals and chemicals
3. Sewage sludge.
4. Miscellaneous materials chemicals, paints, explosives and mining wastes.
River or ocean dumping of these materials leads to water pollution. This tends to contaminate surface as well as ground water. Because of a high organic nature of this material, a large BOD is placed on the waters and the sediment becomes coated with a highly organic ooze. Non combustible materials are generally disposed off by ocean dumping.
The national Environmental Engineering Research Institute (Nagpur, India) has categorized sea off Mumbai upto 5 km as one of the most polluted urban centers where 1.800 millions liters of city's discharge is dumped everyday. In 1994, 800 truckloads of garbage was washed onto the Juhu beach in a single night. Others adding to the coastal pollution include foreign liners docking along the Bombay Port Trust (BPT) which openly dump their wastes into the sea and leave a huge trail of fuel along the coastal stretches while departing.
Thermal Pollution
An increase in the optimum water temperature by industrial processes (steel factories, electric power houses and atomic power plants) may be called as thermal pollution. Many industries generate their own power and use water to cool their generators This hot water is released into the system from where it was drawn, causing a warming trend of surface waters. If the system is poorly flushed, a permanent increase in the temperature may result. However, if the water is released into the well flushed systems, permanent increase in temperature does not occur.
Many organisms are killed instantly by the hot water resulting into a high mortality. It may bring other disturbance in the ecosystem. The eggs of fish may hatch early or fail to hatch at all. It may change the diurnal and seasonal behaviour and metabolic responses of organisms. It may lead to unplanned migration of aquatic animals Macrophytic population may also be changed. As temperature is an important limiting factor, serious changes may be brought about even by a slight increase in temperature in a population.
Oil Pollution
There are about 15 million water crafts on navigable waters throughout the world. Their combined waste discharges are equivalent to a city with a population of 2,000,000. Thus oil pollution, an oxygen demanding waste, is of concem not only from sensational major spills from ships and offshore drilling rigs but also from small spills and cleaning operationsThe information available on oil pollution in Indian oceans is fragmentary. In all, 6,689 observations were made on oil sliks and other floating pollutions along the tanker and trade routes across the northern Indian Ocean of these, oil was sighted on 5582 occasions (Qasim, 1991). The percentage of oil sightings ranged from 51 to 96. The number increased away from the source of oil, that is from the ballast and bilge washings and northern Indian Ocean is well known for oil slicks.
Observations on the floating petroleum residues from the Indian Ocean region show variations in time and are fairly high occasionally along the tanker routes. In the Arabian Sea, the concentration ranged from 0 to 6.0 mg/m² with a mean of 0.59 mg/m². The range in the Bay of Bengal tanker route varied from 0 to 69.75 mg/m². These figures indicate that the tanker route in the Bay of Bengal is relatively more polluted than the Arabian sea.
A layer of oil floating on the ocean surface can interfere with the exchange of oxygen and carbon dioxide and reduce the rate of photosynthesis of marine plankton and the respiration of marine animals. Fuel oil added to sea water in very low concentration (199 ppb) depresses photosynthesis.
The death of birds from oil spills has attracted much attention. In the Torrey Canyon incident in 1967, an estimated 40,000 to 100,000 birds died. The Fort Mercer and Pendleton Collision in 1952 reduced the wintering population of eider ducks from 5,00,000 to 1,50,000.
Health Effects of Water Pollution
For want of dependable statistical data, the extent of mortality and morbidity that can be attributed to water pollution is not exactly known. However, its effects are clear from the lower standard of
human health and from even the limited information on the incidence and the prevelence of common water borne diseases such as typhoid fever, infective hepatitis, cholera, diarrhoea and dysentries.
Diseases of the alimentary tract constitute the biggest group of diseases responsible for much of illness in India. In poor communities, diarrhoea and dysentery have become a part of life. About 2000 people died due to gastroentritis in Delhi alone in July-Aug. 1998. Other water bome communicable diseases assumed propertions. World's biggest ever reported epidermic of infective hepatitis occurred in Delhi in 1955-56 Over 40,000 people developed jaundice and thousands died. Similar situations were observed in Pimpri and Sangli.
Furthermore, mosquito borne diseases like malaria, Japanese encephalitis and dengue have also have associated with water pollution. Nine states with 43% of India's population account for 70% cerebral malaria cases. Similarly cases of Japanese encephalitis have been reported from newer to newer areas-in India. In the north, Uttar Pradesh has been subjected to fluctuating bouts of Japanese encephalitis. After a lull in 1979 (72 deaths), toll rose steeply to 530 in 1980. During 1983, a number of states reported Japanese encephalitis death like Andhra Pradesh, Bihar, Karnataka, Tamil Nadu and Goa. Reports on viral fever-Dengue which is spread by striped mosquito Aedes aegypti had hit the urban and semiurban population in India. In 1982, there was an explosive outbreak of dengue in Delhi which effected hundreds of thousands of people within three months from Aug. to Oct. In 1983, it again hit the city and nearly one-third of city's
population had fallen prey to the fever. The failure of pesticides has thrown control into a state of crisis and the need to develop environmental control techniques is felt all over the world.
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