water pollution

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WATER POLLUTION Presence of impurities in water in such quantities and of such nature as to make it less fit or unfit for a stated purpose.   Extent of Water Pollution: ·      Has reached alarming proportion ·      Surface water, underground water and sea water are all polluted to a greater or lesser extent. ·      Water evaporates as pure water ·      First contamination during condensation, cloud formation and raining –      Rainout & washout of atmospheric pollutants ·      Run off over land contaminates water with constituents of soil & residues left over the soil –      Agricultural run off –      Run off from solids & hazardous waste disposal sites –      Soil erosion ·      Disposal of wastes into water bodies –      Solid and hazardous wastes –      Industrial & municipal effluents –      Drainage from agricultural fields - Siltation of flood plains, river beds, lakes & estuaries

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Water Pollution Continues…………….   Contaminants affecting health of water bodies & reducing utility value of water resources ·      Biodegradable organic matter ·      Suspended, colloidal and dissolved solids ·      Nutrients (N2 & P) ·      Pathogens ·      Acids & bases and ionic species like fluorides ·      Inorganic toxic substances (cyanides) ·      Thermal pollution ·      Soaps & detergents ·      Radionuclides ·      Pesticides ·      Colour and odour causing substances ·      Volatile organic compounds ·      Recalcitrant & refractory organic pollutants

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Effects of Water Pollution 1.     Eutrophication : Nitrates and phosphates from fertilizers and detergents in the water bodies act as nutrients and accelerate the growth of algae which forms a mat or bloom on the water surface. This increased productivity is called eutrophication. a.   The bloom producing algae cut off light to submerged plants b.  On their death they increase the organic loading of water body which further results in depletion of oxygen and hence death of aquatic animals and water begins to stink. c.   The water also becomes unfit for drinking, industrial and recreational use. Therefore, addition of excess of fertilizers to the fields be avoided.   2.   Contamination of food chain -        Toxic chemicals like Hg, As, Pb , Non degradable pesticides and radioactive wastes reach human & animals bodies through food chains & cause poisoning, disease and death. -        Japan’s Minimata bay is a famous example of disaster of eating mercury polluted fish causing large number of deaths. Such deaths have also been reported from Sweden and Canada. -        Pathogens cause diseases of human & domestic animals -        Reduction of productivity of the phytoplanktones -        Destruction of coral reefs from temp. changes

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Measurement of water pollution Water pollution is measured by -        Biological monitoring based on the population of critical species sensitive to pollution. Mostly employed for drinking water checking.   Most Probable Number (MPN) ·         Biological testing quality of water indicates the absence or presence of pathogens in it. ·         Pathogens are disease producing micro-organisms which cause a number of water borne diseases like typhoid, cholera, hepatitis, dysentery, jaundice etc. ·         Intestinal discharge of infected persons contain billions of these pathogens which if allowed to contaminate water bodies may cause the above water borne diseases. ·         Since faecal contamination of water is responsible for a number of diseases, faecal contamination is detected by micro biological examination of water supplies where faecal colliform bacteria are used as indicator organisms since colliform bacteria is always present in association with faecal matter. ·         We use the most probable number (MPN) tube test for measuring the colliform number in water. ·         Here at different dilutions the water samples are incubated with faecal bacteria specific culture media and establish whether the faecal bacteria is present or not in the incubated sample by observing production of gas and change of pH and colour change. ·         Thus density of colliform bacteria is accepted to be microbiological water quality parameter in almost all situations.

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Physico-Chemical Monitoring – based on actual physical & chemical parameters such as Biochemical Oxygen Demand (BOD): -        BOD indicates the quality of waste water and is used to measure the water pollution by organic wastes -        BOD refers to the amount of oxygen needed by bacteria in decomposing the organic wastes present in the water -        It is oxygen required in milligrams for 5 days to metabolise waste present in one litre of water at 20oC. -        BOD is higher in polluted water. Lesser value of BOD indicates comparatively clean water. A weak organic waste has BOD less than 1500 mg/litre, a strong one has higher than this.

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THERMAL POLLUTION  ·    Addition of hot effluents & waste heat which can cause undesirable changes in the natural environment is thermal pollution. ·     Thermal power plants, nuclear power plants, refineries, steel mills etc. are the major sources of thermal pollution. ·       For their operations, power plants utilize only 1/3rd of the energy provided by fossil fuels, the remaining 2/3rd is lost in the form of heat to water which is used for cooling. ·      Cold water, generally, drawn from some nearby water body is passed through the plant & returned to the same water body with temp. 10-16oC higher than the initial temp. Excess of heat reaching such water bodies cause thermal pollution of water.   Effects of Thermal Pollution: ·    Warmer water contains less oxygen (14 ppm at 0oC, 1 ppm at 20oC). Hence the dissolved oxygen content of the water is decreased. ·    High temperature becomes a barrier for oxygen penetration into deep & cold waters ·     Toxicity of pesticides, detergents & chemicals in the effluents increases temperature ·     The composition of flora & fauna changes because the species sensitive to increased temperature due to thermal shock get replaced by temp. tolerant species. ·     Discharge of heated water near the shares can disturb spawning and can even kill young fishes. ·      Fish immigration is affected due to formation of various thermal zones.

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Control of Thermal Pollution Cooling ponds, spray ponds and cooling towers can be employed for control of thermal pollution.   Marine Pollution ·       Today sea is the sewer of the World ·       Main source of marine pollution are rivers which bring pollutants from their drainage basins, catchment areas i.e. coastline where human settlements in the form of hotels, industry, agricultural practices have been established & oil drilling & shipment. ·   Rivers carry sewage sludge, industrial effluents, synthetic detergents, agrochemicals, solid wastes, plastics, metals & waste heat released by industries. ·       Another important source of marine pollution is the leaking of toxic substances, radioactive wastes which are stored in containers & dumped in deep sea ·       Tankers transporting oil contribute to oil pollution significantly, oil in sea water can spread over a large area of the sea, remain dispersed or get absorbed on sediments. Phytoplanktons, zooplanktons, algal species, various species of invertebrates, coral reefs, fish, birds and mammals are affected by oil pollution. ·       Leakage from oil tankers near Alaska in 1989 caused damage to coral reefs & resulted in the death of about 390 thousand birds. During 1991 Gulf war 200 million gallons of oil spread in the Persian Gulf badly affected marine ecosystem.

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Control of Marine Pollution ·       Toxic pollutants from industries & sewage treatment plants should not be discharged in coastal waters. ·       Run off from non-point sources should be prevented to reach coastal areas. ·       Developmental activities on coastal areas should be minimized. ·       Oil & grease from service stations should be minimized. ·       Oil ballast should not be dumped into sea. ·       Ecologically sensitive coastal areas should be protected by not allowing drilling.   Noise Pollution ·       A loud, unpleasant sound or unwanted sound is called noise. ·       Sound is mechanical energy from a vibrating source & it can propagate through a medium like air, liquid or solid. Sound wave is a pressure perturbation in the medium through which sound travels. There is a wide range of sound pressures which encounter human ear. Noise is the amount of sound energy that cannot be tolerated by organisms. ·       The Degree of noise is measured in term of decibel. Man can hear at 10 dB. A peaceful environment exists at 25 dB. Normal conversation occurs at 35-60 dB. Noise level upto 65 dB is well tolerated. Noise above 80 dB causes discomfort in man & at 120-140 dB it produces pain.

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Noise standards recommended by Central Pollution Control Board (CPCB) Area Noise level in dB Industrial 75 Commercial 65 Residential 55 Silence zone 50   Sources of Noise Pollution Noise pollution is a result of modern industrialized urban life and congestion. Main sources are; Transportation (like air, road, rail transportation), industrial operation, agricultural machines (tractors, harvesters, tubewells, lawn mowers) defence equipments (tank, artillery, rocket launching, explosions, shooting practices) domestic gadgets (pressure cooker, mixers, grinders, exhaust fans, desert coolers, air conditioners, vacuum cleaners) entertaining equipments, public address systems, construction work & use of crackers on festive occasions.   High levels of noise have been recorded in some of the cities of the world. In Nanjing(China) noise level of 105 dB, Rome 90 dB, N. York 88 dB, Calcutta 85 dB, Mumbai 82 dB, Delhi 80 dB have been recorded.

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Effects of Noise 1.   Interferes with man’s communication 2.   Hearing damage : Noise can cause temporary or permanent hearing loss. Depends on intensity & duration of sound level. Auditory sensitivity is reduced with noise level of over 90 dB in the midhigh frequency for more than a few minutes. 3.   Physiological & psychological changes: Continuous exposure to noise pollution affects the functioning of various systems of the body. Results in hypertension, insomnia, gastro-intestinal & digestive disorders, peptic ulcers, blood pressure changes, behavioural changes & emotional changes   Control of Noise Pollution 1.   Reduction in source of noise – heavy vehicles & old vehicles should not be allowed to ply in the populated areas 2.   Proper oiling will reduce the noise from the machinery 3.   Use of sound absorbing silencers 4.   Noise making machines should be kept in containers with sound absorbing media 5.   Through law: Legislation can ensure that sound production is minimized at various social functions. Unnecessary horn blowing should be restricted.

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Solid wastes All the wastes arising from human and animal activities that are normally solid and discarded as useless or unwanted.   Encompasses the heterogenous mass of throwaways from residences and commercial activities as well as more homogenous accumulations of a single industrial activity.   Types and sources of solid wastes: Classified into three main categories: 1.   Municipal wastes 2.   Industrial wastes 3.   Hazardous wastes (including hospital wastes)   Municipal Wastes: ·       Solid wastes generated in residential & commercial areas by activities other than industrial production are termed as Municipal Waste. ·       Includes all types of solid & semi solid waste products like food wastes, rubbish like polyethylene bags, empty metal and aluminium cans, scrap metals, glass bottles, waste paper, cloth/rags, ashes and residues, demolition and construction wastes like debris & rubbles, wood, concrete etc. ·       Also includes special wastes such as street sweeping, roadside litter, dead animals and abandoned vehicles etc.

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Industrial Wastes: ·       Wastes which arise from industrial activities & typically include factory rubbish, packing material, organic wastes, acids, alkalis and metals. ·    Main source of industrial wastes are chemical industries, metal & mineral processing industries ·       Radioactive wastes generated by Nuclear power plants ·       Fly ash produced in large quantities by thermal power plants ·       Solid wastes from other types of industries include scrap metal, rubber, plastic, paper, glass, wood, oils, paints, tars, dyes, scrap leather, ceramics, heavy metals, asbestos, batteries etc.  Hazardous Wastes: ·       Wastes that pose a substantial danger immediately or over a period of time to human, plants or animals life are classified as hazardous wastes. ·       A hazardous waste exhibits any of the following characteristics (i) Ignitability (ii) corrosivity (ii) reactivity (iv) toxicity ·   Hazardous waste grouped into five categories (i) radioactive substances (ii) chemicals (iii) biological wastes (iv) flammable wastes & (v) explosives. ·       18 categories of hazardous solid wastes under Waste Management & Handling Rules, 1989 of EP Act, 1986 have been identified by Ministry of Environment and Forests, Govt. of India ·       A person handling any of these hazardous wastes beyond stipulated quantity has to seek authorization or consent of regulatory agency primarily State Pollution Control Board.

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Hospital Wastes (Biological Wastes) ·       Ministry of Environment and Forests has accorded due priority to hospital wastes and rules are being made for their effective and safe disposal. ·       The solid wastes generated in hospitals can be categorized into (a) general wastes (b) biomedical wastes  General Wastes include wastes from packing materials, garbage, kitchen waste which is not infectious or hazardous in nature. Such wastes can be handled along with the municipal wastes and disposed off at the common dumping site.   Biomedical Wastes ·       Generated from the hospital activities including laboratories and other associated areas ·       Potentially dangerous/infectious and can be classified into (i) chemical wastes (ii) pathological wastes (iii) highly infectious wastes (iv) sharp objects (v) pharmaceutical wastes (vi) laboratory wastes   Management of Solid Wastes -        Reduction in raw material use -        Reuse of solid waste materials -        Recovery of materials/metals -        Generation of energy/biogas -        Conversion into useful products such as fertilizers, fuel pellets etc.

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Vermicomposting Increase in crop for improving fertility and health of the soil Increase in retention of soil moisture Increase in nutrient value of organic waste

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Composting ·       Due to shortage of space for landfills in bigger cities, the biodegradable yard waste is allowed to degrade or decompose in an oxygen rich medium. ·       A good quality nutrient rich & environmentally friendly manure is formed which improves soil’s fertility

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Incineration   (iii) Incineration refers to control burning of wastes at high temperature at 500-1200oC in a specially designed furnace. ·       Ashes and gases are the products of incineration. ·       Four basic unit operations are included in an incineration system. o    First stage involves preparation, storage and transportation of wastes to the incinerator in a physical form conducive to the combustion process o     Incinerator furnace is designed on the basis of physico-chemical properties of the wastes. Under controlled conditions of combustion, the toxic organics are thermally oxidized to form flue gases. o    Cooling of these gases directly through quenching and dilution devices or indirectly by employing waste heat recovery systems & special type of boilers. o     Final step removes the pollutants in the flue gases by subjecting them to venturi scrubbing, mass transfer operations, filtration etc. to reduce the emission to acceptable levels before letting them out into the atmosphere.

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SW Management elements Heat recovery efficiency – 70% Amount of steam produced varies from 1.0 to 3.5 kg/kg of MSW Incineration..

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Disposal of Solid Wastes (i)                   Sanitary landfills (ii)                Composting (iii)             Incineration   Sanitary landfills -        In a sanitary landfill, garbage is spread out in thin layers, compacted & covered with clay or plastic foam. -        The solid wastes in landfills undergo a series of bio-chemical decomposition, (biological decay either aerobically or anaerobically & chemical oxidation) -        Results in the production of gases like methane & CO2 & liquids (leachates) in the landfill areas. -        Methane produced by anaerobic decomposition is collected & burnt to produce electricity or heat. -       Liquids released due biochemical reactions of solid wastes in landfill areas referred as leachates. -   Leachates can easily percolate through the solid wastes & can pollute underground water. -        In the modern landfills the bottom is covered with an impermeable liner usually several layers of clay, thick plastic and sand. The liner protects the ground water from being contaminated due to percolation of leachate. Leachate from bottom is pumped & sent for treatment.

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Sanitary landfills

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Role of an individual in prevention of pollution   “Think globally act locally”. ·       Help more in pollution prevention than pollution control. ·       Use ecofriendly products ·       Cut down the use of CFCs as they destroy the ozone layer. ·       Use the chemicals derived from peaches and plums to clean computer chips and circuit board instead of CFCs. ·       Use CFC free refrigerators. ·       Reduce dependency on fossil fuel especially coal or oil. ·       Save electricity by not wasting it when not required ·       Adopt and popularize renewable energy resources ·       Improve energy efficiency. ·       Promote reuse and recycling wherever possible and reduce the production of wastes ·       Use mass transport system for short visits, use bicycle or go on foot. ·       Decrease the use of automobiles. ·       Use pesticides only when absolutely necessary and that too in right amounts. Wherever possible integrated pest management, including alternate pest control methods (biological control) should be used. ·       Use rechargeable batteries. It will reduce metal pollution. ·       Use less hazardous chemicals wherever their application can be afforded. ·       The solid waste generated during one manufacturing process can be used as a raw material for some other processes.

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·  Use low phosphaste, phosphate-free or biodegradable dish washing liquid, laundry detergent and shampoo. This will reduce eutrophication of water bodies. ·       Use organic manure instead of commercial inorganic fertilizers. ·       When building a home, save as many trees as possible in the area ·       Plant more trees as trees can absorb many toxic gases and can purify the air by releasing oxygen. ·       Check population growth so that demand of material is under control.

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The Bhopal Gas Tragedy   ·       World’s worst industrial accident occurred in Bhopal, M.P., India on the night of 2nd & morning of 3rd Dec. 1984 at Union Carbide Company which used to manufacture Carbaryl pesticide using methyl isocyanate (MIC). ·       Due to accidental entry of water in the tank, the reaction mixture got overheated & exploded because its cooling system had failed. Other safety devices also did not work or were not in the working condition. ·       Forty tons of MIC leaked into the atmosphere which might have contained 40 Kg. of phosgene as an impurity. ·       2,50,000 persons got exposed to MIC. About 5100 persons were killed (2600 due to direct exposure to MIC & other 2500 due to after-affects of exposure). An estimated 65,000 people suffered from severe eye, respiratory, neuromuscular, gastrointestinal & gynecological disorder. About 1000 persons became blind. ·       It cost about 570 millions in clean up & damage settlements. Tragedy could have been averted had the company spent about $1 million on safety measurements.

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The Love Canal Tragedy ·       Occurred in Suburb of Niagara falls, New York. Love canal was built by William Love which was later dug up and was used to dump sealed steel drums of chemical wastes by Hooker Chemicals & Plastic Co. between 1942-53. ·       In 1953, the dump site was covered with clay & top soil by the company & sold to the City Board of Education, which built an elementary school on this site. Houses were also built near to the school. ·       In 1976, the residents started complaining of foul smell. Children playing in the canal area received chemical burns. ·       In 1977, the corroded steel containers started leaking the chemicals into storm sewers, basement of homes & the school playground. About 26 toxic organic compounds were identified. ·       The dump site was covered with clay & the leaking wastes were pumped to new treatment plant. The affected families were relocated.

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Arsenic Pollution in ground water   West Bengal & Bangladesh are severely contaminated by the toxic heavy metal arsenic. ·       First report of arsenic pollution in West Bengal came in 1975 and that in Bangladesh in 1993. Common people were found to be ingesting low doses of arsenic for 10-14 years after which white or black spots called melanosis started mottling the skin. Later on these spots converted into leprosy like skin lesions, eventually rotting into gangrenous ulcers. Long exposures often lead to bladder & lung cancer. ·       In West Bengal 40 million out of 90 million people have exposure to arsenic threat due to contaminated water. The 24 paraganas, Hooghly & Murshidabad districts and also Behala and S. Eastern fringes of Kolkata lie in Arsenic Risk Zone. ·       Excessive use of lead arsenate and Cu arsenite as pesticides in high yielding varieties of summer paddy & jute crops are the major causes of arsenic pollution. ·       Arsenic contaminated tubewells in the state are being painted red while safe water tubewells are painted green for use by people.

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Charnobyl Nuclear disaster   ·       Worst nuclear disaster in the history of human civilization occurred at Chernobyl Ukraine in USSR. ·       The accident occurred on 26th April, 1986 at the reactor of the Chernobyl power plant designed to produce 1000 MW electrical energy. The explosion caused the 1000 tonne steel concrete lid of the reactor 4 to blow off. Fire started at the reactor due to combustion of graphite rods & the reactor temperature soared to more than 2000oC. Fuel & radioactive debris spread out in a volcanic cloud of molten mass of the core and gases which drifted over most of the northern hemisphere badly affecting Poland, Denmark, Sweden and Norway. ·       More than 2000 people died. People suffered from ulcerating skin, loss of hair, nausea & anemia. It was feared that some 5,76,000 people exposed to radiation would suffer from cancer specially thyroid cancer & leukemia.