Compilation of answers we got on the causes of water pollution in India!
Answer 1. Causes of Water Pollution in India:
Water Pollution Cause # A. Domestic Sewage:
Domestic sewage is usually a cloudy dilute aqueous solution containing organic matter, human feces, urine, soap, minerals and dirty used up water of houses. Generally, domestic sewage is released into the rivers, on the bank of which most of the cities are situated.
Municipal waste is the principal contributor of water pollution. A recent report from Water Pollution Research Laboratory, London, indicates that domestic sewage contains trace quantities of toxic metals such as Cu, Cr, Zn, Mn, Pb, and Ni. The decomposable organic matters in the domestic sewage exert an oxygen demand on the receiving waters. Organic matter in the sewage includes fatty acids, esters, amino acids, amides, amino sugars etc.
Tremendous quantities of sewages are produced due to extensive population density. Most municipal sewages receive no treatment before they are discharged in water bodies. Sewage treatment deposits the suspended material — called sludge — at the bottom, while the liquid waste consists of ions like Ca++, Mg++, Na+, K+, NH4+, Cl–, N02–, HC03–, S04— and P04— in dissolved condition.
Harmful Effects of Domestic Sewage:
i. Domestic sewage makes the water extremely anesthetic.
ii. Affects the aquatic flora severely.
iii. Interferes with the spawning of fishes.
iv. Causes depletion of DO and enhances BOD.
v. Sewage serves an excellent medium for the growth of pathogenic organisms.
Water Pollution Cause # B. Industrial Effluents:
Industrial effluents discharged into water bodies contain toxic chemicals, hazardous compounds like phenols, aldehydes, ketones, amines, cyanides, metallic wastes, plasticizers, toxic acids, corrosive alkalis, oils, greases, dyes, biocides, suspended solids, non-biodegradable pollutants, radioactive wastes and thermal pollutants from numerous industries.
The principal industries responsible for water pollution in India are chemical and pharmaceuticals, pulp and paper, sugar, distilleries, textiles, steel mills, oil refineries, fertilizer plants, soap and detergent, tanneries etc.
Some Indian rivers and freshwater streams are heavily polluted by industrial effluents.
Harmful Effects of Industrial Pollutants:
i. Cause deleterious effects on living organisms and may bring about death.
ii. Lower the rate of photosynthesis in aquatic flora.
iii. Disinfectants added in water to control phycophytes growth and bacteria may persist in aquatic bodies and consequently may cause mortality of fishes, planktons and diatoms.
iv. Free Cl2 discharged by factories may cause fish mortality.
v. Hg in its inorganic form in water attacks mainly liver and kidneys of aquatic vertebrates whereas organomercurials traverse through the biological membrane and concentrate especially in the brain. Alkyl mercurials are much more toxic than the inorganic forms. Alkyl mercurials tend to accumulate when consumed in small quantities and eventually attack the nervous system.
A concentration of 6.0 ppm in brain cells can cause irreversible brain damage. Hg is also a teratogen, capable of inducing abortion and toxic effects in human embryo. Minamata episode is a popular one in Japan revealing Hg toxicity as described ahead in this section.
vi. Industrial effluents consisting of As, Pb and CN etc. cause cellular degeneration in brain, which results in frigidity, coma, stupor, and numbness in humans when they enter through food chain.
vii. Effluents containing acids and alkalis make the water corrosive.
viii. Heated effluents discharged into aquatic system may severely alter the aquatic ecosystem by increasing the temperature.
ix. Industrial discharges impart colourful odour and turbidity to the receiving waters. They undergo putrefaction to form objectionable tastes.
It shall not be out of place to mention here that in ‘holy’ Ganga alone, about 315 industrial complexes are dumping their effluents. These are indirectly responsible for the ill-health of about 300 million people of northern India!
Mercury, a byproduct of the production of vinyl chloride, is used in many chemical industries. It is also a byproduct of some incinerators, power plants and laboratories. In Japan, illness and even death occurred in the 1950s among fishermen who consumed fishes, crabs, and shell fish contaminated with methyl mercury from the industrial city of Minamata in Japan. The main unit of this city, Shin-Nihon Chisso Hiryo Co., began to produce vinyl chloride and acetaldehyde by the catalytic conversion of acetylene, sine 1949.
During this process some of the HgCl2 catalyst was unknowingly converted to a methyl mercuric compound. This factory kept ejecting its effluent wastes into Minamata Bay. The people who took the fishes, crabs and shell-fish suffered from Minamata Disease. Initial symptoms of Minamata disease included numbness of the limbs, lips and tongue, impairment of motor control, deafness and blurring of vision.
Cellular degeneration occurred in the cerebellum, midbrain and cerebral cortex and this led to spasticity, frigidity, stupor and coma.
In Japan in 1952, due to Minamata disease, 17 people died and 23 became disabled permanently.
Water Pollution Cause # C. Agricultural Discharges:
Agricultural discharges like pesticides of biodegradable and non-biodegradable nature, fertilizer, manure, slurry, animal and plant debris, soil erosion containing mostly the inorganic materials is known to cause heavy pollution to water sources.
Most of the discharges adding to the soil are washed off through the rainfall, irrigation and drainage into water bodies, where they severely disturb the aquatic ecosystem. Agricultural discharges are expected to be three times more than the domestic sewage.
Harmful Effects of Agricultural Discharges:
i. Agricultural discharges containing DDT, which is non-degradable through food chain arriving in man, may cause nervous impairment. DDT is also known as cancer- promoter in humans.
ii. Agricultural discharges containing endosulphan in water bodies prove to be a contact and stomach poison for man.
iii. Pesticidal accumulation in fishes has also been reported.
iv. Agricultural discharges in aquatic bodies disturb the ecosystem homeostasis.
Water Pollution Cause # D. Fertilizers:
Recently NCA reported the increased application of fertilizers from 2.8 million tons in 1976 to 6.0 million tons in 1984 and 9.7 million tons in 1995. The fertilizer enhance crop yield on one hand but they disrupt the entire natural aquatic ecosystem on the other.
India applies about 15-16 kg of fertilizers per hectare while the world average is 55 kg per hectare. In Netherlands the fertilizer consumption is about 71 kg/ ha. However, it is not only the increasing use of fertilizers but also escalated production, which pose adverse effects on water and their living biota.
Fertilizers and other agricultural chemicals create deleterious effects on man, cattle and plants as mentioned below:
A. Effects on Man (Methemoglobinemia):
The nitrate used in fertilizers enter the intestine of man through drinking water. In the intestine nitrate is reduced to toxic nitrites by intestinal bacteria. Nitrite is absorbed into the blood where it combines with hemoglobin to form methemoglobin.
Methemoglobin cannot transport O2. This leads to suffocation and breathing troubles, especially in infants. This disease is called “methemoglobinemia” (blue babies).
It seems important to express here that a healthy person contains 0.8% of methemoglobin, but in the diseases it reaches up to 10% in blood. Above 20% it causes headache and giddiness and above 60% it causes unconsciousness, stiffness and occupational problems. At 80% of mathemoglobin in blood, death occurs.
i. Protein quality of crops degrades.
ii. Excessive use of fertilizers produce large sized fruits and vegetables, which are more prone to pests, insects and diseases.
iii. Superphosphate may lead to Fe, Cu, and Zn deficiency in plants. Potash treatment decreases valuable nutrient like vit. C and carotene in fruits and vegetables.
iv. Liming may check release and uptake of several essential elements such as Zn, Mn, Ni, Fe, Co, and Ca in plants.
v. Excessive addition of nitrates and phosphates in aquatic ecosystem makes it highly productive causing Eutrophication. It leads to depletion of O2 due to excessive algal growth thereby, increasing BOD of water. It also leads to fish and other aquatic fauna mortality.
Water Pollution Cause # E. Detergents:
Detergents are of recent origin, used as cleaning agents and derived from surfactant (10-30%), builder (10-15%) and other ingredients. The surfactant is actually a surface active agent which dissolves partly in water and partly in organic solvent because of its dual hydrocarbon and polar character, for example, alkyl benzene sulphonates are considered as surfactants.
The builder is usually a sodium phosphate (polyphosphate) of the type Na3P3O10 or Na4P2O7 acting as sequestering agent. Both the surfactant and builders of detergent create complex pollution problems in water.
Household detergents contain surface-active agents and contribute to phosphates of sodium, sodium silicates, sodium sulphate, amides and several other builders in water. Since detergents are composed of complex phosphates, they enhance the concentration of phosphates in water leading to eutrophicational problems.
Harmful Effects of Detergents:
i. Act as allergens.
ii. Complex formation between nitrilotriacetate (NTA) and Hg or Cd enhances the possibilities of transmission across the placental membrane (barrier) into fetus, thereby increasing the likelihood of birth defects.
iii. Phosphate, the major ingredient of most detergents, favours the luxuriant growth of algae which form blooms. The extensive growth of algae consumes most of the available O2 from water. The depletion in O2 concentration becomes detrimental to growth of aquatic fauna which produce a foul smell upon decay. Such decomposing water are known to produce toxins as strychnine, which causes mortality in aquatic fauna.
iv. Synthetic detergents destroy aquatic flora and fauna.
v. Detergents cause damage to gills of fishes and remove protective mucus from gills, skin and intestine.
vi. Alkyl benzene sulphonates (ABS) may bring mortality in several species of Mayfly nymphs when they are exposed to 15 ppm for 10 days.
vii. Aquatic invertebrates are severely affected by the detergents. For example, Gray fish are reduced in numbers by 15 days exposure to 10 ppm of effluent containing detergents.
Water Pollution Cause # F. Toxic Metals:
Toxic metals find their way in aquatic bodies from industrial processes, domestic sewage discharge, land run-off, street dust, engineering processes and fossil fuel burning.
Traces of heavy metals such as Cd, Hg, Pb, As, Mn, Co, Fe and Cr have been identified deleterious aquatic ecosystem and human health.
It is notable here that the enhanced level of heavy metals is seriously concerned because of the following reasons:
i. Accumulate in human body.
ii. Create sublethal and chronic effects to organisms even in minute concentration.
iii. Produce teratogenic and mutagenic effects in human.
iv. Cause phytotoxicity.
v. Produce synergistic effects in living organisms.
vi. Affect critically all aquatic bodies and their flora and fauna.
vii. Degrade very slowly and accumulate in the food chain.
Keeping all these in view, tolerance limits for trace metals in drinking water and their recommended maximum concentration (RMC) in irrigation water.
Water Pollution Cause # G. Silts:
Actually silts are the soil/sand particles suspended in the aquatic bodies. Siltation is the most widespread and damaging pollution, especially in hill streams which create high turbidities. These also obstruct the free movement of aquatic organisms, growth of fishes and their productivity.
Salient deleterious effects of suspensoids and colloids on marine biota as reported by Baruton (1985) are as follows:
(i) Decreased visibility of pelagic food
(ii) Reduction in direct light penetration in water
(iii) Reduced photosynthetic rate
(iv) Less food availability
(v) Decreased availability of benthic food and plant biomass
(vi) Clogging of gill rakers and gill filaments in fishes.
Water Pollution Cause # H. Oils:
Oil is a source of pollution in sea water. Oil pollution is due to ship accidents, loading and discharge of oil at the harbour, oil refineries and offshore oil production. It is estimated that two million tons of used lubricating oil are added every year in coastal waters. Maritime accidents due to collision, fire, explosion or grounding also result in oil release in water.
International discharge of oily wastes from tank washing and accidental spillages pollute the sea water severely. From Indira Dock basin alone, more than 90,000 litres of waste oil was collected in 1984. A recent report shows that about 20 billion tons of wastes per year from industries, homes, farms and municipalities end up in sea.
Oil leakage from 20,000 miles (32,000 km) of pipelines which cross waterways may undergo corrosion, cracks or punctures and would lead to oil pollution in sea water.
Effects of Oil Pollution in Sea Water:
Oil pollution in sea water has been an inevitable consequence of the dependence of rapidly growing population on oil based technology.
The overall detrimental effects of oil pollution in marine water:
A. Physical Effects of Oil in Water:
i. Oil films on water may reduce significantly the rate of O2 uptake by water.
ii. Oil slick retards the light intensity up to 90%.
iii. Smothering coats of oil kill lichens and algae along the shore lines.
B. Effect of Oil Pollution on Marine Ecosystem:
i. Heavy damage to fisheries.
ii. Cause lethal toxicity on aquatic flora.
iii. Large-scale fish mortality as in Mumbai coast in 1981.
iv. Direct oil coating unable the fishes to respire and clog their gill slits.
v. Hydrocarbons in oil get incorporated in body tissues of marine animals. These are quite stable like heavy metals and pesticides.
vi. Oil pollutants may block the taste receptors of organisms.
vii. Emulsified oil reaching the bottom of sea may damage flora and fauna.
C. Effects of Oil Pollution on Man:
i. Oil components like aromatic thiophenes, benzothiophenes and merceptans are lethal to man as they damage kidney and liver.
ii. Crude oil contains sulphur compounds, small amount of nitrogen, little olefins, metals like Fe, Ni, and V. These are extremely lethal. Carbonyl sulphide in the crude oil, after dissociation, produces H2S which acts on CNS resulting in death — mainly due to respiratory paralysis.
D. Effects of Oil Pollution on Birds:
i. Birds are especially vulnerable to damage from oil coating. The spilled oils destroy their natural insulating oils and waxes, which shield the birds from water. Consequently they lose insulation, start shivering and may freeze to death in winter. About 25,000 birds’ mortality took place in Torry Canyon Incident.
ii. Oil spilling in marine water causes abnormally low body temperature in birds resulting in hypothermia. Nearly 150 rare species of bald eagles also became victims when they ingested oil during Exxon Valdez accident.
iii. About 1,000 sea otters died when their fur become saturated with oil by losing insulation.
Water Pollution Cause # I. Thermal Pollutants:
Many industries use water for cooling. The resultant warmed water is discharged into rivers, stream or lakes. This brings about water pollution. Thermal pollution is also referred to as calefaction (warming). Generally the thermal pollutants include the waste chiefly from atomic, nuclear and thermal power plants. Municipal sewage also contributes to thermal pollution. The electric utilities constitute the major source of the thermal pollution of rivers and lakes.
They also send heat into the atmosphere, as do in most manufacturing operations and dense, urban communities. Cooling has been the traditional and still common method of discharging waste heat from a power plant.
Major Problems due to Thermal Pollution of Water:
Actually the thermal pollution of water creates two major problems:
i. The activity of biological life is more at higher temperature and, hence, as water temperature rises, there is more demand for dissolved O2.
ii. With rise in the water temperature, the amount of DO in water diminishes. Hence, at higher temperature, less amount of DO will be present in water and it may be fatal for aquatic biota.
Effects of Thermal Pollution:
Thermal pollution alone poses no direct health risks to people but in aquatic system it has a profound effect on organisms as well as on water quality. If the aquatic body contains chemical pollutants, extra warmth increases their toxicity to fishes. Regarding the change in water quality, the density of water has been a maximum of 1,00,000 g/cm2 at 4°C and then decrease slightly at higher temperature.
Also, as the temperature gets increased, the viscosity of water gets decreased and the vapour pressure increases sharply. The solubility of gases in the water may also lower down with increasing temperature. These properties exert significant effects on aquatic life.
Various detrimental effects of thermal pollution in aquatic bodies are:
A. Physico-Chemical Changes in Aquatic Bodies:
i. Density of water decreases.
ii. Viscosity of water decreases.
iii. Decreases the solubility of gases in water.
iv. Vapour pressure increases.
v. Decreases in dissolved oxygen.
vi. Increase in BOD.
B. Effects on Aquatic Biota due to Thermal Pollution:
i. Undesirable changes in the algal population.
ii. Changes in diurnal and seasonal behaviour of aquatic invertebrates.
iii. Migration of aquatic biota.
iv. Excessive eutrophication.
v. Acceleration in activities of pathogenic organisms, which makes the pathogen more virulent, and fishes become less resistant. Bacteria multiply rapidly.
vi. Direct fish mortality due to failure in respiratory, nervous or essential cell processes.
vii. Early hatching of fish eggs.
viii. Failure of trout eggs to hatch and salmon to spawn.
ix. Adverse effects on spawning and reproductive mechanism during spring season.
x. Rapid settling of sediment load in water affects aquatic food supply.
xi. Each type of fish has its own fatal temperature called heat death. For Sockeye Salmon fry, heat death occurs at only 75°F, (24 °C), whereas large-mouth bass can withstand temperature up to 79°F (26°C).
xii. Thermal pollution also results in faster growth rates but shorter life spans in aquatic fauna.
Water Pollution Cause # J. Radioactive Materials:
The oceanic currents carry the radioactive contaminants everywhere. Radioactive pollutants get their way into water streams from various sources such as nuclear power plants, nuclear reactors, nuclear test, nuclear installation, operations of power, processing
fission and fusion product etc. In fact, hazards from radioactivity arise because radionuclides accumulated in body tissues/organs and deliver radiation dose.
Potentially deleterious radioactive Cs, Cm, Bk, Np, Pu, Ru, Zr etc. are produced from neutron bombardment of atomic fuel. Once they find access into aquatic bodies, they disrupt the ecocycling process, enter the food chain and affect adversely the metabolic pathways.
Effects of Radioactive Pollutants on Aquatic Ecosystem:
i. Aquatic life adversely affected.
ii. Radioactive contaminants deposit on surface and ground water. This water consumed by plants during photosynthesis acts as a medium for radioactivity in them.
iii. The radioactive pollutants reach to the top consumer level through food chain.
iv. Ionizing radiations in aquatic bodies mainly result in cellular damage.
v. Radiation in living organisms produces hazardous chemical species like H+, H2O–, H2O+e –, HO2e+, H3O– etc., which cause damaging effects.
vi. The radioactive substances in aquatic habitat react with proteins of aquatic invertebrates and deactivate enzymes by splitting disulphide bonds. With enzyme inhibition, cell growth may continue but cell division cannot proceed.
vii. Radionuclides occurring in aquatic bodies from leaching of minerals or reactors include Ra-226, Sr-90, Ba-140, I-131, Cs-137, U-236, Zr-95, Mn-44, Co-60, Kr-85, K-40 and Ru-103. Some of these fission products are insoluble in water and settle out with particulate materials and concentrate in silts and sludges. The soluble isotopes remain in solution and enter biological cycle causing chronic health effects.
viii. Researches reveal that Zn-65 accumulates in oysters at high level, Fe-55 concentrates in fishes while Sr-90 accumulates in higher invertebrates. These affect their metabolism seriously.
ix. Traces of radioactive substances present in water may cause cancer, leukemia, eye cataract, DNA breakage and carcinoma in human.
x. Drinking water containing Rn-222, Ra-226 and Th-232 can accumulate in humans and cause several physiological, somatic and genetic disorders. It may also cause teratogenesis and mutation defects too.
Answer 2. Causes of Water Pollution in India:
Water Pollution Cause # i. Wastewater Other than Municipal Wastewater:
Around half of the pollution of the oceans is caused by the sewage and the waste water that are led into the seas and oceans. The world generates industrial wastes in the range of about 10-billion tons. Most of it is pumped untreated into rivers, lakes, oceans and other waterways.
Factories are point causes of water pollution, but quite a lot of water is polluted by common men. That is how pristine water becomes wastewater. It is a common practice to pour the chemicals in the drains or toilets. Detergents used in the washing machines and the dishwashers eventually join the rivers and oceans.
So also are the pesticides used in the cultivable fields and gardens of all sorts? Toxic pollutants also enter wastewater from surface runoff. Highway roads are covered by a mixture of toxic chemicals, spilled fuel, brake fluids to bits of worn tyres made from chemical additives, micro-particles of glass and exhaust emissions.
In the rainy season, these chemicals are drained through streams into the rivers. Rains wash all these toxic material and chemicals into rivers in such concentrations that they kill large numbers of fish and aquatic living things. It has been estimated that in a year the highway runoff from a single large city leaks as much oil into our water environment as a tanker spill. Highway runoff runs away into drains. Others pollute the groundwater or accumulate on the land next to road, making it increasingly toxic as years go by.
Water Pollution Cause # ii. Chemical Wastes:
Detergents are milder substances than a lot of other chemicals. At the other side of the spectrum are highly toxic chemicals such as polychlorinated biphenyls (PCBs), widely used to manufacture electronic circuit boards, but their harmful effects have been recognized and their use is prohibited in many countries abroad.
Nevertheless, an estimated half million tons of PCBs are at regular intervals discharged into the environment. They are dumped first into the oceans and thence along with water vapours into the environment. Although PCBs are widely banned, their effects will be felt for many decades because they last for long time in the environment without breaking down.
Another kind of toxic pollution comes from heavy metals, such as lead, cadmium, and mercury. Lead was once commonly used in petrol, though its use is now restricted in some countries. Mercury and cadmium are still used in batteries though some brands now use other metals. Till recently, a highly toxic chemical tributyltin was used in paints to protect boats from the ravaging effects of the oceans. Tributyltin gradually got recognized as a pollutant, and the boats painted with it were doing as much damage to the oceans as the oceans were doing to the boats.
A Japanese factory discharged a lot of mercury metal into Minamata Bay, polluting the water that contaminated the fish stocks. The problem was known only after a decade and by then, many local people consumed the contaminated fish and around 2000 were poisoned. Hundreds of people were left dead or disabled due to Minamata disease.
Water Pollution Cause # iii. Radioactive Waste:
The biggest cause of radioactive pollution are factories that reprocess nuclear waste fuels originating from the nuclear power plants. Radioactive wastewater is led into the sea or ocean by many European countries. The ocean currents carry the nuclear traces around the world. At high concentrations radioactive waste can lead to death and in low concentrations it can cause cancers.
Water Pollution Cause # iv. Pollution of Oceans due to Oil:
It is estimated that about 10 percent of the oil that enters the oceans comes from tanker accidents and oil slicks. More than 70 percent pollution due to oil in seas and oceans comes from routine shipping and from the oil people pour down drains on land. Nevertheless, the oil slicks are polluting endemically in destructive way due to the sheer quantity of oil they release at a time. Such huge spills kill vast populations of marine animals such as thousands of sea otters, marine fish colonies and sea birds. Billions of eggs of marine life are also destroyed at regular intervals due to oil spills and slicks.
Water Pollution Cause # v. Plastics:
Since plastic is light and it floats, plastic things travel very long distances across the oceans. Besides, since most plastics are not biodegradable, they do not break down naturally in the environment, and therefore, plastic substances like bags and bottles remain in the marine environment for a long time. Researchers have found out that plastic bottles can survive for 450 years in the ocean and the plastic fishing threads and lines can last up to 600 years.
Though plastics are not toxic, they pose major hazards to seabirds, fish and other marine living organisms. Plastic fishing lines and wires can strangle or choke fish; plastic bags and small substances can be swallowed by the marine life. Under such circumstances, the life of marine organisms will be posed threats. Also, the chemicals and plastics can cause cancerous diseases to marine organisms and also lead to cell mutation in them.
Water Pollution Cause # vi. Alien Species:
Alien species or invasive species are the species of animal or plant kingdoms from one domain or ecosystem that have been introduced into a different ecosystem to which they do not belong. For instance, the Mediterranean Sea was invaded by alien algae and the Black Sea by an alien jellyfish. These intrusions reduced the fish stocks in those seas by 90 percent.
Answer 3. Causes of Water Pollution in India:
Water, the most abundant and wonderful natural resource, is extremely essential for survival of all living organisms.
But today clean water has become a precious commodity and its quality is threatened by numerous sources of pollution which are as follows:
(i) Sewage and domestic wastes
(ii) Industrial effluents
(iii) Agricultural discharges
(vi) Toxic metals
(viii) Thermal pollutants, and
(ix) Radioactive materials.
Water Pollution Cause # (i) Sewage and Domestic Wastes:
Sewage is commonly a cloudy dilute aqueous solution containing mineral and organic matter. About 75% of water pollution is caused by sewage, domestic wastes and food processing plants. It also includes human excreta, soap, detergent, metals, glass, rubbish garden waste and sewage sludge from cess pools etc.
If domestic waste or sewage is not properly handled after it is produced or if the effluent received at the end of sewage treatment plant is not of adequate standard, there is chance of water being polluted. The indiscriminate method of handling the domestic sewage may also cause pollution of underground sources of water such as wells. If sewage or partially treated sewage is directly discharged into water bodies such as river, the water of such rivers is polluted or contaminated.
Municipal waste is the principal contributor of water pollution. A recent report from Water Pollution Research Laboratory, London indicates that domestic sewage contains trace quantities of toxic metals such as Cu, Cr, Zn, Mn, Pb and Ni. Sewage contains decomposable organic matter and exert an oxygen demand on the receiving waters. Organic matter generally includes fatty acids, esters, amino acids, amides, amino sugars and proteinaceous amines.
Organic pollution in water originates from incompletely digested wastes which have some BOD when they are released in water. It coats the sediments with a highly organic ooze. Several zones may be distinguished in a flowing stream when the organic wastes are added in it.
(i) Degradation zone
(ii) Active decomposition zone
(iii) Recovery zone, and
(iv) Unaffected zone
There is uncontrolled dumping of wastes from rural areas, towns and cities into water bodies. Tremendous quantities of sewages are produced due to extensive population density.
Most municipal sewages receive no treatment before they are discharged in water. Sewage treatment deposits the suspended material, called sludge at the bottom, while the liquid waste consists of ions like Ca2+, Mg2+, Na+, K+, CI–, NO2–, SO42–, PO43–, NH4+ and HCO3– in dissolved condition.
Harmful Effects of Sewage and Domestic Waste:
(i) Sewage is an excellent medium for the growth of pathogenic bacteria, viruses and protozoa. Vibriocholerae found in sewage causes cholera. Salmonella typhosa causes typhoid, while shigella dysenteriae causes bacillary dysentery. Even after sewage treatment, the water contains pathogenic bacteria and the chances of pathogens mingling with river water are critically high.
(ii) Domestic sewage, which is primarily composed of spent water containing wine, faeces, soapy wastes, food materials and paper makes the water extremely anaesthetic.
(iii) The ova and larvae of many worms are parasitic to man. They may pass out in urine and faeces thereby contaminating the receiving water.
(iv) Several pathogenic micro-organisms introduced into the water course cause deleterious effects and chronic diseases in man and animals.
(v) Sewage containing oxidisable and fermentable matter causes depletion of dissolved oxygen in the receiving water bodies affecting the aquatic flora severely.
(vi) Oxygen deficiency also leads to the production of objectionable odours in water. Due to the evolution of putrefied gases, the solid wastes are buoyed up by these gases resulting in offensive foul matters floating on water surface.
(vii) Presence of solid matter floating in suspension, colloidal and pseudo-colloidal dispersion in sewage creates serious water problems. Highly organic suspended matters which putrefy the water get deposited on river beds, behind weirs or sludge.
(viii) Suspended matter present in sewage has a tendency to blanket the stream thereby interfering with the spawning of fish and reduction of aquatic biota.
(ix) Accumulation of sewage and domestic wastes in water bodies retards the self-regulatory capabilities of aquatic organisms. Self-purifying ability of water is lost and it becomes unfit for domestic purposes. Moreover, the decomposition of wastes by aerobic microbes decreases due to extreme pollution.
(x) Discharge of nutrient rich effluents, sewage and domestic waste in combination with industrial wastes poses serious health problems in man.
(xi) Sewage from different cities in India has a high value of BOD because water used for treating flushing system is less than that used in developed countries. In Chennai sewer blockage and overflowing is common which intensely pollute the aquatic environment. Another problem is the high grit content in water caused by using sand for scouring pans which create hindrances at inlets of treatment plants.
(xii) Sewage poses major threat to water courses. Today developed countries are fighting against thermal and chemical pollutants, while Indians have to combat with chemicals and pathogens with their limited resources.
Water Pollution Cause # (ii) Industrial Effluents:
Industrial effluents discharged into water bodies contain toxic chemicals, hazardous compounds, phenols, aldehydes, ketones, amines, cyanides, metallic wastes, plasticizers, toxic acids, corrosive alkalies, oils, greases, dyes, biocides, suspended solids, non-biodegradable matter, radioactive wastes and thermal pollutants from numerous industries.
The principal type of industries which contribute to water pollution of rivers in India are chemicals and pharmaceuticals, coal washeries, soaps and detergents, pulp and paper, sugar, distilleries, dyeing, tanneries, steel mills, fertilisers etc.
These effluents when discharged through sewage system poison the biological purification mechanism of sewage treatment and pose several pollution problems.
The toxicity of various pollutants to aquatic environment is variable but all of them contaminate on the bottom of water systems where they poison or smother the aquatic organisms. Most of the industrial effluents are insusceptible to degradation. Toxic metals are extremely lethal for living beings. Sulphuric acid waste from coal mines is a chronic pollutant which enhances hardness of water and corrodes concrete etc. It has also drastically affected the living biota.
Harmful Effects of Industrial Pollutants:
(i) Industrial effluents cause deleterious effects on living organisms and may bring about death or sub-lethal pathology of kidneys, liver, lungs, brain and reproductive system (Wilbur).
(ii) Effluents like methyl mercaptan and pentachloro phenol lower the photosynthetic rate of aquatic communities by hindering sunlight penetration into the water column.
(iii) Disinfectants, which are added in water to control algal growth and bacteria may persist in water bodies and may cause mortality of fish, planktons and diatoms.
(iv) It has been reported that free chlorine discharged by factories near Mirzapur in UP had caused heavy fish mortality in river Sone near Dehri-on-sone in Bihar.
(v) Mercury, like toxic lead, arsenic, cadmium and cyanides has cropped seriously in water bodies.
(vi) Mercury poisoning among aquatic organisms has resulted in crippling and often fatal diseases like Minamata in Japan (1950). Effluents sometimes contain upto 10 times the level of Hg in natural water (0.001 to 0.00001 ppm). Natural addition of Hg to oceanic water is about 5000 tonnes per annum and further 5000 tonnes are added via human activities.
(vii) Industrial effluents consisting of As, Pb and CN etc. cause cellular degeneration in brain which results in frigidity, coma, stupor and numbness.
(viii) Effluents containing acids and alkalies make the water corrosive.
(ix) Mineral constituents can be responsible for excessive hardness of water which then becomes unsuitable for domestic and industrial purposes.
(x) Some of the trade wastes contain pathogenic bacteria. For instance the pathogen Anthrax bacilli is present in tannery wastes.
(xi) Toxic effluents may inhibit the natural purification schemes of the water bodies.
(xii) Heated effluents discharged into water system may severely alter the aquatic ecosystem by increasing the temperature of the stream.
(xiii) Industrial discharges impart colour, foul odour and turbidity to the receiving waters. They undergo putrefaction to form objectionable tastes.
(xiv) Mani Mahi River in Baroda receives industrial and several petrochemical wastes and is badly polluted. Similarly, river Cooum flowing through Chennai has become so much polluted by sewage that even the zoo planktons have been unable to thrive in it. It is estimated that one litre of Cooum water is having as much as 900 mg of iron, 275 mg of lead, 32 gm of zinc and 1310 mg of nickel.
Water Pollution Cause # (iii) Agricultural Discharges:
Plant nutrients, pesticides, insecticides, herbicides, fertilisers, farm wastes, manure slurry, sediments, drainage from silage, plants and animal’s debris, soil erosion containing mostly the inorganic materials are reported to cause heavy pollution to water sources. In modern agricultural practices NPK fertilisers containing nitrate and phosphate are added to the soil.
Some of these are washed off through rain fall, irrigation and drainage into water bodies, where they severely disturb the aquatic ecosystem. The excessive use of plant nutrients led to the disruption of nitrogen and phosphorus balance in water affecting plant growth. Organic wastes increase the BOD of receiving water.
Some pesticides are not only non-biodegradable but are slightly soluble in water. Consequently when they are sprayed on cropland, they remain adhere to the soil for long periods. During rainfall they tend to be carried as suspended particles into water systems. It is deemed that pollutants affecting underground aquifers are more serious than it would be in a surface water system due to impossibility of treatment of polluted water.
Over pumping in coastal area is considered to be responsible for water pollution. As compared to developed countries, India has relatively low use of these chemicals. Hence their discharges into water bodies are still low. However, agricultural discharges are expected to be three times more than domestic sewage.
Water Pollution Cause # (iv) Fertilisers:
Modern agriculture rely heavily on artificial fertilisers, including several biocides. Although these chemicals enhance vegetation but they disrupt the entire natural aquatic ecosystem. They acutely pollute the water.
Effects of Fertilisers:
Fertilisers and other agricultural chemicals create following deleterious effects on man and plants.
(A) Effects on Man and Animals:
(i) Excessive use of fertilisers lead to the accumulation of nitrates in water. When such water is used by man, these nitrates are reduced to toxic nitrites by intestinal bacteria. Nitrites cause serious disease in children called “methemoglobinaemia” (blue babies) where nitrites interfere with oxygen carrying capacity of blood causing suffocation and damaging respiratory as well as vascular systems.
(ii) Normally 0.8% of methemoglobin is present in healthy person but in the disease methemoglobinaemia this content increases to 10% in the blood. Above 20% it causes headache and giddiness, while above 60% it causes unconsciousness, stiffness and occupational problems. Death occurs at 80% of methemoglobin.
(iii) Recently WHO reported that nitrate level in Rajasthan are 800 mg per litre which is much higher than the permissible limit of 45 mg per litre. Nitrate poisoning in grazing animals like cows and cattle have been reported in Nagpur which is due to the consumption of vegetables grown in nitrate rich soil.
(B) Effects on Plants:
(i) Agricultural fertilisers crowd out essential nutrients present in top soil layers. The microbes enrich humus enhance plant growth. But fertilisers enriched soil cannot support microbial life for long periods. Hence there is a poor humus and less nutrients while the soil can readily become eroded by wind and rain.
(ii) Although fertilisers increase the total crop yield but at the expense of protein loss. It is reported that there occurs a 20-25% decline in protein content when corn and wheat crops were grown on soil fertilised with NPK fertilisers. Moreover, subtle balance of amino acids within protein molecules is also disrupted degrading the protein quality resulting in malnutrition.
(iii) Excessive use of fertilisers produce large sized vegetables and fruits, which are more prone to pests, insects and diseases.
(iv) Water containing agricultural wastes also impede the uptake of minerals and imbalance the whole mineral pattern in plant systems.
(v) Superphosphates may lead to Fe, Cu, and Zn deficiency in plants. Potash treatment decreases valuable nutrients like ascorbic acid (vitamin C) and carotene in fruits and vegetables.
(vi) Liming can prevent release and uptake of several essential elements such as Zn, Mn, Ca, Ni, Fe, Co in plants.
(vii) Excessive addition of nitrates and phosphates in aquatic system, makes it highly productive or eutrophic causing “eutrophication” in water. It leads to depletion of oxygen due to excessive algal growth, thereby increasing BOD of water. It also leads to death of fish and other aquatic life.
Water Pollution Cause # (v) Detergents:
Detergents are of recent origin, used as cleansing agents and derived from surfactant (10-30%), builder (15%) and other ingredients. Household detergents contain several pollutants which severely affect the water bodies. They contain surface active agents and contribute to phosphates of sodium, sodium silicates, sodium sulphate, amides and several other builders in water. Present day sewage contains appreciable quantities of synthetic detergents.
The persistent surfactants like alkyl benzene sulphonate (ABS) interfere with the waste treatment processes by stabilising the small particles in colloidal suspensions thereby decreasing the activity of biological filter beds and activated sludge. Waste water contaminated with detergent carries a huge cap of foam. This visible foam is anaesthetic for all purposes. ABS kills several species of mayfly nymphus when they get exposed to 12-16 ppm for ten days.
Now linear alkyl benzene sulphonates (LAS) are commonly employed. Since detergents are composed of complex phosphates, they increase the concentration of phosphates in water posing eutrophication problems.
Water Pollution Cause # (vi) Toxic Metals:
Toxic metals are added in aquatic system from industrial processes, domestic sewage discharge, street dust, land run off and fossil fuel burning. Traces of heavy metals such as Hg, Cd, Pb, As, Co, Mn, Fe and Cr have been identified as deleterious to aquatic ecosystem and human health. Waste containing high concentration of toxic metals either separately or in combination are extremely toxic to all organisms. Mercury alone with heavy metals such as Sb, Fe, Co, Cr and Se were reported in sewage sludges.
The major sources of lead poisoning have been steel and paint industries. About 80% of lead retained in the body enters the bone affecting the metabolic activities. Recently ‘WHO’ recommended maximum uptake of 3 mg lead per week, while its excessive dose is extremely lethal. Cadmium (Cd) is toxic to living organisms even in low concentration of < 1 mg Cd per litre.
Toxicity of chromium (Cr3+) to aquatic forms varies differently. Copper is also acutely harmful to fish and its adverse effects depend on the hardness of water. For instance, for carp fish the 96 hour LC50 at hardness 53 and 250 mg/l as CaCO3 was 6.5 mg Cu/l and 0.6 mg Cu/l respectively.
These metals are cumulative poisons and affect dangerously all the aquatic flora. An extremely toxic metal will eliminate the entire aquatic invertebrates until its concentration is reduced below the toxic threshold limit dilution, volatilisation and dissipation. Methyl arsenic compounds occur in various water systems in enough substantial percentages.
Manganese also enters the water bodies through domestic wastes, industrial effluents and dry cell batteries. It is lethal to man in higher levels. Its chronic exposure leads to neurological disorders. Selenium content of most drinking waters is found as 10 ppb. Its excessive amount creates carcinogenic effect on man and animals.
In coal mine areas, water pollution from mine seepage causes several serious problems. Sulphur present in coal produces sulphurous and sulphuric acid in water which are perhaps responsible for lowering the pH of the streams. These heavy metals degrade very slowly, accumulate in the food chain ultimately killing aquatic or terrestrial life.
Water Pollution Cause # (vii) Siltation:
Siltation is the most widespread and damaging pollutant especially in hill streams. These soil particles create high turbidities in water and may hinder the free movement of aquatic organisms, growth of fishes and their productivity.
Various deleterious effects of suspensoids and colloids on marine animals and plants have been observed.
(i) Reduced visibility of pelagic food.
(ii) Reduction in direct light penetration in water.
(iii) Decrease in photosynthetic rate.
(iv) Less food availability and plant biomass.
(v) Decreased aerial predation risk.
(vi) Clogging of gill rakers and gill filaments in fishes.
(vii) Due to smothering, reduced availability of benthic food.
Water Pollution Cause # (viii) Thermal Pollutants:
These pollutants include the waste chiefly from atomic, nuclear and thermal power plants. The discharge of un-utilised heat is highest in the thermal power plants which adversely affect the aquatic environment. Apart from electric power plants, various industries with cooling requirement contribute to thermal loading. Recently it is reported that about 20% more heat is given to cooling waters in nuclear power plants than fossil fuel plants of equivalent size.
Municipal sewage also contributes to thermal pollution. Domestic sewage normally have a higher temperature than the receiving water. When sewage is discharged into water streams, not only the stream temperature rises to a measurable extent but there are other effects also.
The thermal pollution of water creates two major problems:
(i) The activity of biological life is more at higher temperature and hence as temperature of water rises, there is more demand for dissolved oxygen.
(ii) As the temperature of water rises, the amount of dissolved oxygen in water decreases. Hence at higher temperature, less amount of dissolved oxygen will be present in water and it may be fatal for aquatic life.
Effects of Thermal Pollution:
The rise in temperature in aquatic system has a profound effect on organisms as well as on water quality.
These detrimental effects are as follows:
(i) Reduction in dissolved oxygen.
(ii) Increase in BOD.
(iii) Early hatching of fish eggs.
(iv) Failure of trout eggs to hatch and salmon to spawn.
(v) Direct fish mortality due to failure in respiratory, nervous or essential cell processes.
(vi) Adverse effects on spawning and reproductive mechanisms during spring season.
(vii) Bacteria multiply rapidly, which in turn become the food of protozoans.
(viii) Undesirable changes in algal population.
(ix) Excessive eutrophication.
(x) Acceleration in activities of pathogenic organisms which makes the pathogen more virulent and fish less resistant.
(xi) Migration of aquatic biota.
(xii) Changes in diurnal and seasonal behaviour of aquatic invertebrates.
(xiii) Changes in physical and chemical properties of water. For example, vapour pressure increases while viscosity decreases.
(xiv) Decrease in solubility of gases in water.
(xv) Rapid setting of sediment load in water affecting aquatic food supply.
Water Pollution Cause # (ix) Radio-Active Materials in Water:
Today man made sources have begun to add large doses of radionuclides to the already existing radio-active materials in water bodies to which the living organisms are accustomed with various ill effects. Radio-active pollutants enter into water streams from various sources such as nuclear power plants, nuclear reactors, nuclear test, nuclear installations, operations of power, processing fission and fusion products etc.
Actually hazards from radioactivity arise because radionuclides deposit in body organs and deliver radiation dose. Extremely toxic radioactive Pu, Np, Am, Cm, Bk, Cs, Zr, Ru etc. are produced from neutron bombardment of atomic fuel. Once they find access into water bodies, they disrupt the eco-cycling process, enter into food chain and affect metabolic pathways.
Effects of Radio-Active Pollutants:
The ill effects due to radioactive pollutants in water are numerous.
(i) Radionuclides in water wreck havoc on the atoms, molecules and living beings in its path. Serious skin cancer, carcinoma, melanoma, breast cancer, leukemia, DNA breakage and cataracts are rapidly climbing the list of diseases in man.
(ii) Polluted water containing radio-isotopes produce a set of syndromes characterised by nausea, vomiting, diarrhoea, anorexia, epilation, lethargy and general weakness which is known as radiation sickness.
(iii) It destroys biological immune system i.e. body becomes less resistant towards a variety of diseases.
(iv) It causes somatic and genetic disorders, gene mutations and blood abnormalities in higher animals including man.
(v) Radio-active elements present in water accumulate in soil sediments, air and aquatic ecosystem.
(vi) Trace amounts of radionuclides may lead to increase in the rate of mutation in plants.
(vii) A recent study reveals that phosphatic fertiliser also contains fluorine and minute traces of uranium which enter the water system through rainfall and affect seriously plant’s metabolism.
Answer 4. Causes of Water Pollution in India:
Water Pollution Cause # I. Point and Non-Point Sources of Pollution:
Water pollution is a pertinent issue in today’s world and large number of waste materials are added to the water making it unfit for human consumption.
There are two forms of water pollution:
(a) Point Source:
Point source pollution occurs when pollutants are directly dumped into waters. The best suited example of this is the Exxon Valdez oil spill.
(b) Non-Point Source:
Non-point source of pollution is when pollutants are indirectly discharged into the river mostly through environmental changes. This type of pollutant discharge is common through fertilized crop field and the fertilizer gets washed into the river through rain in the form of surface water run-off.
Industries are the major sources of water pollution. With the devastating effect of pollution to the environment, people are getting conscious as well as responsible towards society. Industries are practicing green technologies, corporate social responsibility and implementing ISO 14001. Some of the industries have realized the harm they have done to the nature and have thus taken action accordingly.
The major impacts of oil and refineries are geological and geophysical surveys, drilling and production activities, oil spillage, commissioning, decommissioning and abandonment of offshore installations. With global and regional aspects of pollution, special attention is given to the environmental standards.
Tamil Nadu has many tanneries which are known to discharge untreated chemical effluents into the water bodies, agricultural fields and roadside dumps and even into open fields. The river Palar, which was the primary source of drinking water for the residents of the area is so badly contaminated that there is water scarcity in the region.
Paper manufacturing consumes vast quantities of water and trees. “Consumption of fresh water reduces water levels necessary for fish, and alters water temperature, a critical environmental factor for fish. In British Columbia, Canada, 17 kraft mills discharge about 641 billion litres (141 billion gallons) of liquid effluent each year (Environment Canada, Environmental Effects Monitoring Report)”.
Exploitation of Wetlands:
Wetlands are rich in biological diversity, they are regarded as land builders as their submerged root system, mangroves retard water movement and trap suspended materials and remains of organisms. These organisms raise soil nutrient and its level and build the shoreline seaward. Wetland protects coral reefs and sea grass beds from being smothered by silt brought down by rivers and streams. These protect shoreline from erosion, acting as a buffer against waves.
With boom in tourism industry the problem of water pollution from cruise ships has risen. These generate an astonishing amount of pollution, up to 1,70,000 gallons of sewage from toilets and sinks, galleys and showers each day. This proliferates bacteria, pathogens and sediments heavy metals to the coastal environment.
The Clean Cruise Ship Act of 2004 introduced:
i. Prohibit discharges of any sewage or bilge water within 12 miles of US shore and within the Great Lakes.
ii. Establish uniform treatment standards for sewage discharges outside of twelve miles.
iii. Ensure illegal discharges do not continue by requiring better inspection and monitoring.
Water Pollution Cause # II. Pollution from Shrimp Farming and Aquaculture:
Indian shrimp aquaculture production tripled from 30,000 tons (1990) to 102,000 tons (1999) leading to a number of environmental problems and social conflicts in the last decade. As a result there is enormous levels of salinization of drinking water wells and water pollution and conversion of mangrove forests. Supreme Court in 1996 passed an order by which Aquaculture Authority and Regulatory and Institutional Framework was established for the shrimp aquaculture.
Through a judicious mix of policy measures the social and environmental management of Indian shrimp farming can be bettered which would also, include a strong licensing system, keeping an eye on an effective enforcement of the rules and regulation. Attention should be paid to the use of economic incentives for monitoring the social and environmental degradations.
Leaching of Pesticides into Groundwater:
Use of pesticide has increased to cater the exploding population with adequate food supply. The United States have become the largest producer of food products in the world. Mineral fertilizers and livestock effluents impart phosphorous (ammonium and calcium phosphate). This contributes to the surface run-off and pollutes the water bodies near agricultural fields where groundwater is further contaminated through the leaching of pesticides into the soil.
In India, more than 680,000 hectares of land is under mining lease. In 2000, estimated opencast coal-mines cover around 100 square kilometers. In Gumgaon, Manganese Ore India Ltd. (MOIL) spoil dumps are found on more than one-quarter of the leased land. Mining activities on land have created environmental damage that has severely impacted not only the landscape but also the region’s economic and social well-being.
Mining activities spoil topsoil, nutrients and supportive micro flora, which are necessary ingredients for sustaining the biogeochemical cycles. Mining waste, residues of minerals, ores, dust and other toxic chemicals leach into the soil; it also contaminates subsoil and surrounding water bodies. These percolate through the surface and pollute surface and deep aquifers.
The 15-year-old Durgapur dump, located about 160 kilometers from the Nagpur mine, was in much the same condition. Coal India Limited, requested NEERI to participate in a project on environmental problems associated with its coal mine dump at Durgapur in eastern India.
NEERI found that Microbe Assisted Phytoremediation (MAP) is an excellent method that can be utilized for fast restoration and productivity of wastelands. Similar was the case of Gumgaon, the extraction of manganese from the Gumgaon mine, began in the late nineteenth century and continued for nearly a century. It has rendered the 20-hectare mining area a barren waste land.
Concept of Water Foot Prints:
The concept of water foot print is the nothing but the total volume of water used. For individuals this is expressed as litres and for nations it becomes very complex and involves the lot of variables. It suffices to say, for the simplification of understanding that water foot print is “the use of domestic water resources, minus the virtual water export flows, plus the virtual water import flows”.
This is a very important measurement as it helps to asses a nations call on the total global water. This water foot print is generally linked with the dietary habits of the country. A nation having a meat based diet will have a larger water foot print. Bringing it down to the individual level it is enough to calculate water foot print by seeing it as a function of that individuals consumption pattern and diet chart.
Remedying the Situation:
Polluted water like sewage and sullage resulting from human use and industrial process needs to be treated before being discharged into the rivers or any other water body or even buried or recycled. In water treatment plant the waste water passes through various stages like a series of filters with different bore sizes, then mechanical treatment chambers and finally chemical treatments to reduce their toxicity to tolerable levels and also to break them down to smaller and smaller sizes.
All in all there are three general stages through which polluted water is passed and are generally called the primary, the secondary and the tertiary stage. During the first stage a large number of non-soluble and inorganic matters are sieved out. The secondary stage tries to hasten up the natural biological degradation of matter through catalysts and different chemicals. During the third and tertiary stage the water is made fit for human use.
Therefore in this stage nearly ninety nine percent of the solids in the water is removed, treated heavily with chemicals to ensure that the harmful impurities are lost. But the tertiary stage is only implemented if the water is to be reused for human consumption otherwise the first two stages make the water fit to be discharged into the rivers or into wetlands where the natural rejuvenation power of the water bodies treat the impurities, if any, left in the water.
Answer 5. Causes of Water Pollution in India:
Keeping the water pollution categories in mind, the next logical question is, “Where do these contaminants come from, and how do they get into the aquatic environment?” There are a great many sources or causes of pollution; following are just a few general types and should not be considered a complete list. From these starting points, the pathways a contaminant may take would be the next step to examine.
However, fully understanding the source may better define a contaminant’s nature and thereby affect the pathways available to it. The sources described herein are presented in the very broadest sense, as anthropogenic pollution sources and activities are everywhere and are often difficult to capture under any one label.
Water Pollution Cause # 1. Wastewater Discharges—Point Sources:
Treated effluent from wastewater treatment of municipal, industrial, and commercial treatment facilities usually occurs as a point source, i.e., from a discharge pipe. The wastewater will have physical, chemical and biological characteristics to a degree depending on the extent of treatment. Included here are point-source discharges to surface waters (receiving water bodies—RWB), and subsurface discharges from septic tanks, cesspools, leaching fields, and deep well injection (DWI).
Untreated effluent from combined sewer systems overflows during storms also can be a point-source discharge. The combined sewer overflows—CSOs—exist in cities with older infrastructures. Untreated discharges also occur illegally as point sources from domestic, commercial, and industrial facilities.
In addition, when wastewater treatment plants have mechanical or process problems, they may have to discharge untreated wastewaters. These types of discharges will have all the characteristics of untreated wastewaters, including such attributes as high BOD, COD, TSS, nutrients, metals, etc., with the potential for pH problems as well.
Water Pollution Cause # 2. Stormwater Discharges:
These occur from runoff of sewered environments and include drainage from streets, parking lots, lawns, building roofs, etc. The more developed an area, the more significant these point-source discharges are as a pollution source. Characteristics include BOD, TSS, petroleum products, heavy metals, fertilizing nutrients, pesticides, etc.
This has become such a problem in the New York metropolitan area that new regulations are being developed to address it. Because stormwater is directed to both receiving water bodies and catch basins, this source of pollution poses a threat to both surface and groundwater. If no storm sewer system exists, the potential problem would exist as a non-point source.
Water Pollution Cause # 3. Agriculture:
Runoff from farmlands can often release pesticides and nutrients that can pollute both surface and groundwater. This occurs due to runoff, percolation, and infiltration. In addition, the direct loss of habitat should be considered. During development of land for use in farming, the potential for erosion may be an important source of sediments that can foul surface waters as a non-point source of pollution. Other damage may occur from improper irrigation practices, which can result in a buildup of salts in the soil.
Water Pollution Cause # 4. Mining:
Many types of mining take place throughout the world—from the classic shaft- mining of the old days to the strip mining techniques of today. The cutting of trees for the timber industry also will be included here as a type of mining of natural resources.
Whether it is coal, oil, timber, ores, rock, sand, etc., all may have a distinctive impact on surface waters and groundwaters. Examples of the impact include TSS, low pH, heavy metals, and many others that result from non-point source runoff and erosion from mining operations as well as leaching from tailings and spoils stockpiles.
Water Pollution Cause # 5. Land Development:
The quality and health of the lands that surround water bodies, or overlay important groundwater supplies, both protect and mitigate the impact of pollution. The impact due to land development is often most noticeable in rural and undeveloped areas. Land clearing operations create runoff and erosion problems that affect surface water quality. Development also may impact watersheds and recharge areas, potentially affecting potable water supplies.
We also must consider that land development with the resulting habitat loss may impact the balance of aquatic systems, as well, because an ecosystem by definition includes the interaction of all its components of land, air, and water. Lastly, existing vegetation may preclude or mitigate pollution from runoff, as well as provide an important interface and buffer between the land and aquatic environment.
Water Pollution Cause # 6. Solid Waste Disposal:
Man’s anthropocentric views have led to a throw-away society, which has resulted in significant waste disposal issues and problems. Impacts to aquatic systems commonly occur from the generation of leachate by landfills. We must consider not only domestic landfills but also industrial, commercial and hazardous waste landfills as well.
Transfer stations, storage areas, and all associated operations also can be categorized here, ‘including ocean dumping and other types of sludge disposal. Important in this category is the significant amount of illegal disposal, past and present that can cause, and has resulted in, major problems.
Water Pollution Cause # 7. Accidents:
Whether it is an accident during cargo transportation or at a fixed manufacturing or processing plant, many spill or leak incidents have catastrophic results. Tanker accidents, such as the Exxon Valdez, attract public attention, but the great number of small incidents, sometimes of dangerous materials, probably has a greater impact by their sheer numbers.
Slow leaks or accidental spills of materials in storage, such as fuel or chemical storage tanks, cause pervasive problems in modern society and are now becoming more and more regulated as their threat is increasingly realized.
Water Pollution Cause # 8. Atmospheric Pollution:
Materials transported and deposited by the atmosphere, as well as the atmosphere’s general condition, can result in surface water pollution. The stacks of power plants and industry input significant pollutants that eventually find their way to earth as acidic deposition and many other types of contamination.
The use of aerosols has focused attention on the ozone layer and its ability to protect us from cosmic radiation, which has the potential to impact phytoplankton ecology. The possible effects of the greenhouse gases still are being debated. The potential for atmospheric pollution to affect the hydrologic cycle on a global basis raises the question of the possible effect on the biosphere as a whole.
Answer 6. Causes of Water Pollution in India:
Water gets contaminated by both point and non-point sources of pollution:
Water Pollution Cause # 1. Point Sources:
Point sources of pollution occur when the polluting substance is emitted directly into the water bodies. Basically, these refer to the contaminants that go into a waterway from a single and identifiable source like a pipe. For example- urban cities located along or near the bank of river Yamuna discharge toxic chemicals directly into a river.
Water Pollution Cause # 2. Non-Point or Diffused Sources:
A non-point source occurs when there is runoff of pollutants from diffused sources or from a larger area into water bodies. Just contrary to the point source, the diffused sources are unspecified; numerous in numbers and contribution of each is of less significance. For instance, fertilizer and pesticide from a field are carried into a stream by surface run-off.
The important non-point pollution sources contributing to rivers in the country include agricultural pollution sources, dumping of garbage and dead bodies, immersion of idols, pollution that are due to in-stream uses of water like bathing and clothes washing, cattle wading and open defecation.
Answer 7. Causes of Water Pollution in India:
Sources of water pollution are numerous.
The important sources of water contamination are given below:
Water Pollution Cause # (a) Industrial Effluents:
Industries generally find it convenient to discharge their untreated or partially treated effluents directly into river or stream or canal, through a municipal sewer or other means, causes water pollution. Although the industrial affluent account for only 10 per cent of waste water 19 but these effluents are not easily degradable and toxic in nature which create severe health hazards.
Water Pollution Cause # (b) Community Wastes:
Exponential growth of population and rapid and unplanned urbanisation have created the new problem of water pollution. Most of the municipalities find themselves unable to provide adequate sewage treatment and therefore raw sewage and sullage of urban areas find their way directly into water courses to cause water pollution. “Contrary to common belief, it has been estimated that community wastes” account for four times as much waste water as industrial effluents.
Most of these much waste water ass industrial effluents. Most of these wastes are discharged untreated into the water courses. Out of India’s 3119 towns and cities only 217 have partial (209) or full (8) sewerage and sewage treatment facilities. These cover less than a third of the urban population.
Water Pollution Cause # (c) Ground Storage:
Anything stored on earth such as, any raw materials, solid refuse of a mine or quarry on any land may cause pollution by rain washing it into a stream. This happened in Goa where, Molasses stored in open unlined pits in a co-operative sugar factory at USgaon in Goa was washed away by rain into the Khandapar River. This resulted into degradation of the quality of water and even after treatment it could not be used for human consumption. A large number of fish also killed.
Water Pollution Cause # (d) Air Pollution:
Even air pollutant can cause water pollution. Recent reports from Western Countries indicate that by far the largest contribution of heavy metal pollution in lakes (i.e., from cadmium mercury, lead etc.) comes from airborne pollutants mainly from coal combustion settling on lakes and their catchment areas.
Water Pollution Cause # (e) Storms and Agriculture Runoff:
Air pollutants settled on the land and trees are washed away by rain water and reach to the water course. Similarly inorganic fertilizers used in agriculture to boost production and pesticides and insecticides sprayed on crops do not fully absorb by the land and when washed by rain or irrigation water mingled with water courses and causes water pollution.
Water Pollution Cause # (f) Ground Water Pollution:
Even ground water is not free from pollution. The direct way to pollute ground water is to dump trade effluents or sewage into underground state. But ground water may be polluted due to seepage or percolation from the surface “Human waste may cause pollution by seepage from improperly constructed or improperly placed septic tanks, cesspools or leaking sewer lines.
Industrial wastes including highly poisonous chemicals may be introduced to ground water either by intention or accident. Even the dumping and covering of vegetable materials in garbage result in their decomposition and the carrying down of decomposition products, including carbon dioxide gas, by percolating water into underlying ground water bodies from the article.
Water Pollution Cause # (g) Distribution System:
In India water pollution is also caused by water distribution system. Water is distributed to the Community intermittently. When there is no water in the distribution system vacuum is there. As pipes and pipe joints are not completely water tight they suck in contaminated water. A survey carried out by NEERI has shown that 18-23 per cent of the water supplied is lost due to leaks in the distribution system. When water can go out of the leaks, water pure or impure depending on the location of pipes can be easily sucked in.