Ground Water Pollution:
More and more people throughout the world, including India, are now dependent on ground water for drinking, agricultural and industrial use.
In the recent past, ground water was considered generally pure and safe for drinking.
However, recent studies have revealed that ground water sources are also facing major threats of pollution.
Ground water is being polluted by percolation of contaminated surface water through the layers of the earth. Release of raw sewage in unlined soak-pits and release of toxic effluents by the industries into surface water bodies, are the main causes of ground water pollution Indiscriminate and overuse of fertilizers, chemicals and pesticides have also caused ground water pollution through the seepage of irrigation water into ground water reserves.
The hazards of ground water pollution depend on several factors such as:
i. Concentration or toxicity of the pollutant
ii. The level of ground water if the level is higher chances of contamination are more
iii. Conditions of ground water recharge
Water is essential for all forms of life and none can survive on this earth without water. The surface of earth measures 50,000 billion hectare of which about 70% is covered by water and the rest is land. The total volume of water on the earth is 1011 million cubic kilometers of which about 97% i.e., 986 million cubic kilometers is contained in oceans and an additional 3 million cubic kilometers of salty water is buried underground and the remaining 2.5% (22 million cubic kms) account for the total fresh water, frozen water of glaciers and polar ice caps.
Of the 113 river basins in India, 14 are major, 44 are medium and 55 are minor (major basins are larger than 20,000 square km., minor basins are smaller than 2000 sq km). Three major rivers, namely the Ganga, the Brahmaputra, and the Indus, are snow fed rivers originating from the Himalayas and the other major rivers originate either in the central plains or in peninsular India.
Chemically, water contains two parts hydrogen and one part oxygen. Water for human consumption should be clean, colourless, odorless, well aerated, cool, soft, palatable, free from dissolved toxic substances and suspended particles. But water is rarely found in pure state. Man has polluted the bodies of water to an alarming state. In recent years the pollution of water has become one of the most significant environmental problems in the world.
There is a great concern for rapidly deteriorating quality of water. The causes of water pollution are many but urbanisation, industrialization and increasing pollution are more prominent among them. Water is said to be polluted when its quality or composition is changed either naturally or as a result of human activities and it becomes unsuitable for drinking and less suitable for domestic, agricultural, industrial, recreational and other uses.
The dissolved or suspended substances which deteriorate the quality of water and make it unfit for human consumption are called water pollutants. In other words, water pollutants are those physical, chemical or biological factors which are harmful to aquatic life and to those who consume water. Water pollutants include several chemicals in dissolved or suspended state, some physical factors such as heat, radiations, and some bio-pollutants such as aquatic microorganisms, particularly pathogens (Table 13.2).
Most of the wastes generated by human society are disposed of in the bodies of water such as rivers, lakes and oceans. Some of the wastes which are discharged in air or on land may also ultimately enter the bodies of water. When human population is concentrated too much along the water ways they are unable to handle huge quantities of domestic wastes released into them and consequently they become polluted with unhappy results.
Growths of big cities and industrial setups at the banks of rivers have posed serious problems. Huge discharge of industrial wastes and sewage into the rivers, lakes, ponds etc. at times, and polluted water to such an extent that dead fishes were seen floating on the surface of water. Today there is a growing concern about the pollution of our lakes and rivers. The results of water pollution are quite apparent whether they are measured in terms of living resources, or hazards to human health or reduction of immunities.
Marine pollution is the matter of International concern from the point of view of conservation of living resources. All coastal nations dispose of millions of gallons of untreated sewage, millions of tonnes of garbage, unlimited amount of low level radioactive wastes etc. into the seas.
There can be no doubt in it that there has been a serious decline in environmental quality and production in estuarine and shallow coastal waters as a result of pollution. Oceans are considered the ultimate waste disposal sinks. Though, the oceans have enormous capacity to dilute, degrade and disperse large amounts of wastes, there is a limit to it.
In addition to the marine environment, areas along the coasts, such as, estuaries, reefs, wetlands, mangroves, etc. are adversely affected due to enormous dumping of pollutants into the ocean. This problem is further aggravated due to the fact that about 40% of the world’s population lives near the sea.
The oceans cover major part of the earth’s surface (71%) and play an important role in maintaining the different geochemical cycles. The unceremonious dumping of pollutants in to the marine water would thus cause severe imbalances in the earth’s natural cycles.
The main sources of marine pollution are:
1. Municipal wastes and sewage
2. Industrial effluents
3. Runoff agricultural wastes
4. Oil spills from tankers
5. Offshore drilling and mining
6. Submarine nuclear testing
7. Dumping of radioactive wastes
The consequences of marine pollution are as follows:
i. The pollutants adversely affect the productive ocean regions, thus causing huge losses of fish populations and coral reefs. This results in economic losses amounting to billions of dollars per year.
ii. Eutrophication, due to the influx of organic pollutants, results in the formation of red tides. These are blooms (massive growth) of red algae, which inhibit the movement of ships and also kill marine fauna.
iii. Dumping of huge amounts of toxic wastes in a short duration of time, creates areas of oxygen-depleted zones in the coastal waters. In these zones, most of the aquatic lives die or migrate elsewhere.
iv. Discarded garbage, sewage, plastic refuse, etc. that are dumped in the oceans sometimes accumulate in the beaches. This spoils the aesthetic beauty of the region and results in loss of tourism.
Water Pollutants and their Effects:
Most of the rivers and fresh water streams in India are badly polluted by industrial wastes or effluents. The major sources of pollution of some Indian rivers are listed in Table 13.3.
Contamination of water with industrial wastes is most dangerous. The sewage of big cities is often drained into rivers. This sewage promotes the growth of phytoplankton’s. The excessive growth depletes the oxygen of water. This reduction of oxygen and the presence of poisonous wastes affect the fish population. Besides these, rivers, lakes and ponds are also used directly by people for bathing or washing. This contaminates the water with the germs of various diseases- like cholera, dysentery and hepatitis.
The effluents produce physical, chemical and biological changes in water. Some pollutants produce only temporary effects in water whereas others have long standing effects. There are several types of physical and chemical effects produced by pollutants.
(1) Addition of poisonous substances;
(2) addition of suspended particles;
(3) Addition of non-toxic salts;
(4) Water de-oxygenation, and
(5) Heating of water.
Some of the important effects of water pollutants are discussed here as under:
1. Sewage and other oxygen demanding wastes:
These are largely organic materials that can be oxidized by micro-organisms to CO2 and water. When the amount of sewage discharged is relatively small, the river will not become badly polluted and the biological degradation will soon remove most of the wastes. However, medium and strong sewage as well as other O2 demanding wastes from industry and agriculture can lead to depletion of dissolved O2 in water. Septic conditions are said to prevail when the dissolved O2 is very low.
Sewage contains human excreta, dung and urine of animals, some dissolved proteins, carbohydrates, fats and a variety of inorganic wastes such as nitrites, nitrates, phosphates, chlondes, carbonates sulphates and mineral elements like sodium, potassium, calcium, magnesium, aluminium, nickle chromium etc.
Through drainage system the sewage is discharged into the rivers, canals, lakes and sea which makes the bodies of water polluted. Pollution of water promotes vigorous growth of algae and other microbes which results in the development of yellow or grey scum on the surface of water. Sometimes water smells stingy and appears to be coloured. This is referred to as water bloom. In natural state, the organic wastes are degraded or decomposed by microorganisms.
Sometimes, the rate of decomposition of pollutants is much slower than their addition leading to depletion of oxygen which makes the pollution problem serious and complicated, in developed countries and in a great majority of developing nations including India, different types of sewage disposal systems are employed for the removal of organic and inorganic wastes and other harmful substances from sewage before that is discharged into the body of water.
Sewage and other O2 demanding wastes are classified as water pollutants because of the following reasons:
(i) Their degradation leads to O2 depletion which affects or even kills fishes and other aquatic life;
(ii) They produce foul odour and undesired colours;
(iii) They may lead to scum and sludge that render water unfit for recreational use.
Microorganisms such as algae, fungi, bacteria, viruses, protozoa, etc. often reach to water bodies through surface runoff, domestic wastes and sewage. These microbes produce several undesirable and harmful effects in water. Many of them cause diseases in human beings and equatic animals through contacts.
Waste water from municipalities, sanatona, tanning and slaughtering plants and boats discharged into the rivers, streams, lakes, etc. may be a potential source of infective bacteria and other microbes which cause diseases in man and other animals. Cholera typhoid and many skin diseases are transmissible though polluted water. Recent Jaundice epidemic in Delhi and Kanpur was considered to be due to the excessive pollution of water of Jamuna and Ganga respectively, which are used for drinking purpose.
3. Plant nutrients:
Surface runoff from agricultural fields carries nitrogenous and phosphate organic loading of the streams. Excess algal growth has been of particular concern since algae lead to depletion of O2 in water, create problems for municipalities and industries and make water unfit for recreational uses.
4. Exotic organic chemicals:
These include surfactants, detergents, pesticides, various industrial products, oils and decomposition products of other organic compounds. Good amount of oil along with waste products of industry reaches the sea and rivers. Oil discharged from coastal industries and from ships is most likely to be responsible for the tainting of fishes and shell fishes. Sea food with oily taints is highly objectionable and the suspected presence of tainted consignment can damage the market generally.
The most important groups of compounds which are both toxic and persistent are the chlorinated hydrocarbons including organo-chlorine pesticides, such as DDT, Dieldrin, BHC, Polychlorinated biphenyls (PCBs) and benzene products. The pesticides as shown in Fig. 13.2 are dispersed in the environment through air and water. They become concentrated in successive transfers from plants to herbivores to carnivores.
This is termed bio-magnification. Agricultural pesticides poison or kill millions of fishes and other aquatic life. DDT may upset behaviour pattern in fishes and survival of young molluscs and crustacea. PCBs compounds seem to be substantially less toxic than DDT but they certainly accumulate in marine animals in the similar manner.
There is suggestion that they were responsible for sea birds’ deaths at the U.K. coast in 1969 but it could not be substantiated. Some plastic intermediates and the by-products appear to be widespread in the sea. Very insufficient information is available to assess their toxicity which may well accumulate in marine animals and plants.
At various places, water becomes accumulated with some toxic compounds such as arsenic, lead, cadmium, mercury and some pesticides etc. These reach to underground water by percolation. When the people consume water, these compounds remain stored in the body tissue. Many plants and some animals also store such toxic compounds in their biomass. Human beings consume such toxic compounds through plants, animals and polluted water and store in their body tissues.
This phenomenon of accumulation of bio-toxins is called bioaccumulation. As these compounds do not metabolize but they get magnified and become concentrated. Thus, the amount of toxic compounds is increased through biological food chain; the process is called Bio-magnification or Biological magnification. During deficiency of food in the body, the reserve food is utilized along with these toxic compounds, which are passed into blood stream causing toxic effects.
Figure 13.2 shows the various steps of food chain in which the concentration of DDT increases from 0.02 ppm in the pond water to 5 ppm in phytoplankton’s (free floating plants) to 40-300 ppm in plant eating fishes and ultimately reaches to 2000 ppm in fish eating birds.
5. Inorganic minerals and chemical compounds:
Inorganic chemicals of many types find their way into waters through municipal and industrial wastes and the urban runoff. These pollutants can kill and injure fishes and other aquatic life and they can interfere with the suitability of water for drinking and industrial purposes. Mercury, lead, cadmium and copper are the important metals that cause most concern. Other metals reaching the rivers and sea in substantial quantities are zinc and chromium. Cyanides, thiocyanates, chromates, acids, alkalis, organic solvents and several other industrial wastes are causing serious concern to general public.
Arsenic is absorbed through skin and lung. It causes cancer of skin and lung. Chronic exposure to arsenic causes “Black-foot” disease which is prevalent in the parts of West Bengal and Bangladesh (Fig. 13.3).
It is toxic to aquatic life. Mercury occurs naturally in the sea as the result of weathering of mercury bearing rocks. It is also present in fossil fuels, coal and oils and reaches the sea by serial transport. It is highly persistent and said to be converted into a highly toxic mono-methyl mercury (CH3Hg) and dimethyl mercury (CH3)2Hg which produce nervous disorders in marine animals at an ordinarily low level of dietary intake. Normal level of Hg in fish probably ranges between 0.02 and 0.2 ppm.
In situations exposed to industrial discharges containing Hg wastes in Japan, Sweden and North America, Hg levels above 1.0 ppm have been found. Consumption of Hg contaminated fishes may be hazardous to man. High concentration of mercury is injurious to human life. Human beings feeding on such poisoned animals develop a crippling deformity called malamute disease.
Mercury causes chromosome damage and inhibits chromosomal disjunction during gamete formation and brings about genetic changes (Ramel, 1974). It is now known that anaerobic bacteria in bottom mud can convert Hg into mono-methyl mercury (CH3Hg).
Minamata disease is caused by organic mercury poisoning. In 1956, an epidemic broke out in minamata, a small town on the coast of Kyushu which is the southernmost Island of Japan. The disease took a heavy death toll. The cause of disease was mercury waste dumped into Minamata Bay by Chisso Corporation. The effluent of chissofactory contaminated the Mianamata Bay with mercury.
The mud samples collected from the Bay near factory outlet contained about 200 ppm mercury. Fish and shellfish samples were also found to be contaminated with high methyl mercury levels ranging from 10-40 ppm. Autopsies of Manimata Victims revealed about 70 ppm in liver 140 ppm in kidney and 24 ppm in brain which is very sensitive to methyl mercury.
Even hair samples of residents of the Minamata town with no outward symptoms of disease showed 100-150 ppm methyl mercury, normal level ranging from 8-90 ppm. Up to early 1960s, it was widely assumed that elemental mercury discharged into the biosphere was not hazardous as it did not react easily with other substances and it was nearly insoluble in water.
Swedish scientists for the first time noted this fact that mercury dumped in the bay was in elemental or inorganic form whereas the fishes inhabiting in the waters contained toxic form, the methyl mercury. In 1972, it was demonstrated beyond doubt that aquatic micro organisms living in the mud of natural water ways could transform insoluble elemental mercury into highly soluble and highly toxic form, the methyl mercury. That soluble methyl mercury was absorbed by tissues of fishes and from fishes that reached to man and other predators that consumed contaminated fishes.
The symptoms of minamata disease are muscular pain, madness convulsions, arching of body like a bow, loss of speech and vision, paralysis, crippling of arms and legs. At the last stage of disease, the patient loses imotional control, passes into coma and finally dies.
Soon after 1956 epidemic outbreak, Chisso’s own physician Dr. Hajime Hosokawa had quietly begun to test the effect of factory waste by feeding that to laboratory cats and, to this surprises, he found the same results. On 7th October, 1959 he found that cats suffered convulsions, profusely salivated and suddenly crashed against the laboratory wall and died. Bur Dr. Hosakawa did not publish his results and that secret remained unexplained for some ten years.
In 1966, again an identical case of mercury poisoning broke out in Niigata town in central Japan and for that outbreak Denko company was held guilty of dumping toxic substances into the Angano river. The victims sued the company was held guilty of dumping toxic substances into the Angano river. The victims sued the company and the court decided the case in favour of victims. This success caused fierce resentment in Minamata against Chisso factory and a criminal Law suit was filed in a Japanese Court against the factory.
In 1968, the company stopped discharging mercury waste into Minamata Bay. On March 20, 1973 the court gave verdict against Chisso factory and the plaintiffs and dependents of those who had died were paid heavy damage compensation ranging from 60,000 to 80,000 dollars to each and company had paid 200 million dollars. In 1979, 1401 individuals were certified as victims of Minamata disease and out of this number 353 had died. This is continuation of the account on lead.
Lead is the natural nonessential element generally found in all the components of ecosystem. It is one of the important pollutants of water, air and biosphere. Lead is accumulating in the marine environment as a result of drainage from rocks bearing this metal, industrial and domestic sources particularly the use of anti-knock motor fuels containing lead compounds.
It has been calculated that motor vehicle exhausts contribute up to 2 x 105 tonnes of lead annually to the ocean through atmospheric transport. Much of this accumulates in the surface layer of sediments. One study based on geochemical relationships and material balances suggest that modem man absorbs daily 20 µg lead from food, 1 µg from water and up to 10µg from urban air. Natural conditions are estimated to have .01 ppm lead in food, .0005 ppm in water and 5 x 10-4 µg/m3 in air.
The pollutant is persistent cumulative and may show biological amplification. It has mutagenic effects (Hickey et al. 1971) and it may cause congenital deformities. Lead disturbs metabolism through its effect on enzymes. Symptoms of lead poisoning include loss of appetite, appearance of bluish lines round the gums, anaemia, etc. The rapid increase in the lead level in air and aquatic environment in recent years must be viewed with concern.
Copper and zinc have long been known to accumulate to very high levels in molluscs where they may colour the flesh and render them unmarketable but marine fishes do not exhibit this characteristic to the same degree. No toxic effects on consumers have yet been recorded. Besides above metal elements, molybdenum, barium, manganese, cobalt, are other metallic pollutants which may show toxic effects on human health.
Cadmium is also accumulated by some marine animals and is only slowly excreted. It is highly toxic but there is lack of information as to its biological effects. It was the cause of etaietai disease in Japan. This metal leads to the formation of kidney stone. Liver and pancreas are also effected. The information regarding chromium is also very sparse. Liquid wastes or effluents from industries. The liquid effluents of industries containing a variety of poisonous chemicals are discharged into the bodies of water. They not only change the pH of water but also adversely affect the aquatic plant and animal life and sometimes cause large scale killing of fishes and other aquatic animals.
Oil spills. Petroleum extracted from the area of continental shelf is transported from one country to another through sea. After unloading, the tankers are washed in sea. This causes oil slicks or spills in the sea especially near the ports and shore lines. Because of accidents during transportation and extraction process, oil is spread hundreds of kilometers on the water surface which causes serious problems. A line of oil spilled into water can spread and cover an area of four thousand square metres of water surface. Three fourth of the oil spilled into the water is subjected to emulsification and the rest is evaporated (Fig. 13.4).
The effects of oil are as follows:
(i) Oil film on the surface of water prevents oxygenation of water.
(ii) It inhibits plankton growth and photosynthetic activity of aquatic plants.
(iii) It causes death of aquatic animals due to reduced oxygen availability in water, poisoning of food and toxic effect of oil.
(iv) Oil spilled over water surface may catch fire and cause damage to aquatic life.
(v) Detergents used to clean oil spill are equally harmful to aquatic life.
Effects of Water Pollution:
Water pollution is the cause of many dangerous diseases. In India, still more than 50% people suffer due to disease caused by drinking of unsafe water.
The various effects of water pollution are discussed here as follows:
Many pollutants produce undesirable colours, taste and odour in water and make it unpleasant and unfit for drinking and domestic uses. These changes may be in O2 contents, temperature, and pH which affect the physicochemical nature of water.
The addition of organic substances results in depletion of oxygen and increase in CO2, due to their decomposition by aerobic bacteria. The addition of nutrients through various sources enhances the alga and other biological growths which help in decomposition and lead to depletion of O2. This IS called eutrophication.
The decomposition of organic materials in absence of O2 produces unpleasant odour and unaesthetic conditions due to release of several obnoxious gases as ammoma, methane, hydrogen sulphide etc. Algal photosynthesis produces increase in pH of water by consuming CO2. CO2 dissolved in water produces carbonates.
Excess pollutants affect the aquatic flora and fauna. Most of the fresh water algae are highly sensitive to pollutants and their elimination modifies the predatory relationship by breaking down the food Cham which results in change of plant and animal communities, Biodiversity decreases in presence of a few tolerant species in polluted aquatic medium. Excess of nutrients in water promotes algal growth and formation of water blooms by blue-green and green algae. Many of the blue-green algae are not consumed by fishes and other aquatic animals and some of them produce toxic secretions which disturb the aquatic ecosystems.
Some pollutants for example, heavy metals, biocides, cyanides, and other organic and inorganic compounds are harmful to aquatic organisms. Although these substances have low permissible limits their presence beyond those limits can make water unfit for aquatic life, human beings as well as for other uses. These chemicals prove to be toxic to aquatic organisms and many of them, especially non-biodegradable ones accumulate in the body of organisms and cause long- term effects.
Vectors are certain organisms that act as the carriers of many pathogens, for example mosquitoes. They themselves are unaffected by the pathogens, but transmit the pathogens to the human bodies causing a number of deadly diseases. The vectors breed in unsanitary and stagnant water bodies. Some common dieses spread by vectors are malaria, filarial, encephalitis, etc.
Few wastes for example sewage contain several pathogenic fungi, bacteria and viruses Clostridium perfringens. Streptococcus faecalis cause various types of food poisoning Besides several diseases are water-borne which spread by sewage contaminated water, e.g., cholera’ typhoid, paratyphoid, dysentery, colitis, jaundice etc. (Table 13.4).
Control of Water Pollution:
Controlling water pollution is a multi-disciplinary approach that relates to maintaining the quality of water for human, industrial and agricultural use.
This can be achieved by the following:
i. Treatment of effluents before discharge, which involves the removal of particulates dissolved organic contaminants and dissolved inorganic contaminants.
ii. Installation of waste-water treatment plants should be made mandatory for every industry (Fig. 13.5)
iii. Proper use of fertilizers, chemicals and pesticides, and preventing their runoff into water bodies.
iv. Tree plantation is very effective to check excessive runoff of polluted agricultural water
v. Adopting Integrated Pest Management (IPM) to minimize the use of pesticides for the control of pests. It involves the use of chemical, biological and cultural methods to control weeds, insects and plant pathogenrs simultaneously.
vii. Proper disposal of municipal sewage so as to avoid contamination of ground water reserves.
viii. Marine pollution should also be checked, especially in sensitive coastal ecosystems. This can be done by avoiding oil spills, curbing developmental activities on the coastlines and avoiding the dumping of toxic wastes.