Water Pollution
Water is essential for all living organisms. All plants absorb essential elements in dissolved form and water is the solvent. In the water many mineral elements, Organic substances and gases are dissolved. If the concentration already present substances increases or some other harmful substances usually not found in water gets dissolved in water it gets polluted. Water pollution is defined as "The addition of any substances to water that changes physical and chemical properties in any way which interferes with its use for legitimate purpose". Normally water is never pure in a chemical sense. Many gases, minerals, suspended matters and some microbes are present in the water. Polluted water is turbid, unpleasant, bad smelling, unfit for drinking.
Sources
The chief sources of water pollution are sewage and other waste, industrial effluents, agricultural discharges, industrial wastes from chemical industries, fossil fuel plants and nuclear power plants.
Sewage is the waterborne waste derived from domestic waste and animal or food processing plants. It includes human excreta, paper, cloth, soap and detergents etc. These are the major proportion of the pollutants entering our water body. There is uncontrolled dumping of waste of rural and urban areas, into pond, lakes or river.
Due to accumulation of sewage and other wastes in these bodies, they are not able to recycle them and their self regulatory capability is lost. The decomposition of these wastes by aerobic microbes decreases due to higher level of pollution. The self purifying ability of the water is lost and water becomes unfit for drinking purpose.
Phosphate is major ingredients of most detergents. They favour the luxuriant growth of algae which form water blooms. This extensive algal growth also consumes most of the available oxygen from water.
Many pathogenic microbes may begin to grow on products coming from tanneries, slaughter houses, sewage disposal plants etc. in the water bodies under anaerobic conditions. These may result into spread of fatal water-born diseases.
Inorganic and organic pollutants are present in effluents from breweries, tanneries, dying textile, paper and pulp mills ete. The pollutants include oils, greases, plastic, phenols, toxins, acids, salts, dyes etc. many of which are not ready for degradation and thus cause serious pollution problem. Coal mine discharges sulphuric acid and ferric hydroxide into local stream through sewage. The acid on entering the water bodies destroys its aquatic life.
The use of radioactive materials in nuclear power plants, use of radioactive isotopes in medical, industrial and research institutes and nuclear tests. The discharge of radioactive wastes into water and sewer systems is likely to create problem in future.
Oil pollution of the seas has increased over the year. Due to increased traffic of oil tankers in the seas that causing oil spill. Also due to oil losses during off-shore drilling oil pollution is increasing.
Pesticides have been largely used for killing pest and insects harmful for crops and there crop production. At present there are more than 10,000 different types of pesticides are to be used. They include insecticide like DDT (dichloro diphenyl tricholoroethane), herbicides and fungicides.
Coal fired thermal power plants are source of thermal pollution. The hot water from these plants is dumped as waste into nearby lake or river where its temperature is rise. This high temperature is harmful for aquatic life.
Ocean covers more than 70% of the earth and is the major importance in the cycling of carbon dioxide, nitrogen and phosphorus. They are valuable resource of
people. Ocean currents sometimes transport pollutants back to shore. Like nonbiodegradable plastic bottles, pellets and containers. Offshore mining and shipping add pollutants to the oceans. A significant amount of oil spills into the ocean kills ocean life like planktons, fish larva and marine mammals. Marine pollution adds to reduction in the dissolved oxygen content.
Quality parameters
It is essential to enforce water quality standards in the interest of public health. All developed countries conform to water quality parameter. The United States public health (USPH) has laid down standards for water quality parameters.
Table-: Water Quality Parameter of Domestic Water UPSH Standards (upper limits)
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Quality Parameter |
Water quality is closely linked to water use and to the state of economic development. Quantitative measurements of pollution are necessary before water pollution can be controlled. Some standards methods are use in quality measurement.
1. Dissolved Oxygen- The amount of oxygen dissolved in the water is usually measured either by an oxygen probe or the old standard wet technique, the Winkler dissolved oxygen test.
2. Biochemical Oxygen Demand- BOD is taken as indirect measure of water
quality. It measures the amount of oxygen required by microbes while stabilizing decomposable organic matter.
3. Chemical Oxygen Demand- In Chemical oxygen demand organics are
oxidised chemically instead of biologically. All organics are oxidized in Chemical Oxygen Demand test and only some are decomposed during the Biochemical Oxygen Demand test, COD values are always higher than BOD
values.
4. Turbidity- If water is dirty i.e. Light transmission inhibited, it is known as turbid water. The standard method of measuring turbidity is the Jackson Candle Turbidmeter.
5. Solids- Solids are residue left on evaporation at 103 degree centigrade. Total solids have two fractions, the dissolved solid and suspended solid.
Effects
The effects of water pollution are not only harmful to people but also to animals. and other living beings. Polluted water is unsuitable for drinking, recreation. agriculture and industries. Nobody can escape the effect of water pollution. Some effects by the water pollution are given below.
1. Biochemical Oxygen Demand- To measure water pollution Biochemical oxygen demand (BOD) test is made. In this test amount of oxygen sufficient to destroy waste organic matter by bacteria in a sample is measured. The more oxygen that is used by the bacteria degrade the organic matter in the sample, the greater the BOD. The BOD of household sewage is 200-400 ppm (In one litre polluted water sample).
2. Dissolved Oxygen - Oil pollution reduces light transmission through surface of water and hence reduces photosynthesis by marine plants, decreases dissolved oxygen in water causing damage to marine life and also contaminates sea food which enters the human food chain.
3. Arsenic Contamination-More than one million people in six districts of West Bengal drink arsenic-contaminated ground water from tube wells in the region. Among them 20 lakh people suffer from various diseases related to arsenic poisonings like loss of hair, brittle of nails, bronchitis etc.
4. Minamata diseases-Mercury enters waternaturally as well as through industrial effluents. Mercury is responsible for the minamata epidemic that caused several deaths, In Japan and Sweden. The tragedy had occurred due to consumption of heavily mercury contaminated fishes, by the villagers.
5. Flurosis- Flurosis is a crippling disease that affects the bones. The disorder occurs due to prolonged consumption of fluoride contaminated water and in the affected areas in Unnao the fluoride content has been recorded as high as 15-19 ppm as against the permissible dose of 1 ppm. The affected person suffers from stiff backs, fixed joint, deformed spines and may cann't stand on their own.
6. Selenium-Selenium accumulates in plants growing in selenium rich soils and become toxic to animal's grazing on them. Toxicity causes stunted growth, loss of appetite, shedding of hairs and nails and gastrointestinal disturbances.
7. Lead-If present in different foods in traces, it accumulates in the body leading to poisoning and causing severe anaemia and changes in kidney and arteries. Causes decrease in rate of mitosis in root tips. Automobile burning leaded gasoline poured most of the lead in the air. Lead particles enter in to the food chain; an intake of it can also cause mental retardation, partial paralysis, loss of hearing and death.
Oxalic acid-Excess intake of oxalic acid causes renal calculi (Stone of kidney).
Ganga pollution-Ganga along with its tributaries is the largest and a very important river basin of the country. It has been a symbol of purity but today it is grossly polluted.
Control measures
Biodegradable pollution alone is not responsible for water pollution. Water pollution load is contributed by no biodegradable or slow degrading pollutants such as heavy metals, mineral oil, biocide, plastic mineral etc. all pollutants are dumped in to water. Various ways are suggested for control the water pollution.
1. Stablisation of ecosystem- The basic principles involved are the reduction in waste input, harvesting and removal of biomass, trapping of nutrients, fish management and aeration.
2. Recycling of waste- Various kinds of wastes may be recycled to beneficial use.
3. Removal of pollution- So many types of pollutants are to be present in the water body. By the appropriate method we can remove the particular pollutants by the polluted water body. Some pollutants are given below.
Ammonia- Ammonia can remove by the waste water by ion exchange technique. This can be used for fertilizers.
Mercury- Mercury can be removed from chlor alkali effluents plants by using mercury selective ion exchange resin.
Phenolics- Phenolics can be removed by the help of polymeric absorbent.
Decolorisations of water- The decolorisation of the water remove by the help of electrolyte decomposition technique.
Salts- Salts can be removed by the help of reverse osmosis method.
Though water act was promulgated in 1974, a serious concern about water quality control could be generated only recently. The water (Prevention and control of pollution) Cess Act, 1977 could recognize the value of this resources.
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