Purification of water on a small scale.ppt

1、Purification of water on a small scale,House hold purification of water,Different methods are generally available for purifying water on an individual or domestic scale These methods can be used singly or in combination Boiling Chemical disinfection Filtration.,Boiling,The water must be brought to a

2、 rolling boil for 5 to 10 minutes Its kills all bacteria, spores, cysts and ova and yields sterilized water Boiling also removes temporary hardness of water by driving off carbon dioxide and precipitating the calcium carbonate It is an excellent method but offers no residual protection against subse

3、quent contamination Water should be boiled preferably in same container in which it is to be stored to avoid contamination during storage,Chemical disinfection,Chemical disinfection includes: Bleaching powder Chlorine solution High test hypochlorites Chlorine tablets Iodine Potassium permagnate.,Ble

4、aching powder,Chlorinated lime is a white amorphous powder with a pungent smell of chlorine It contains about 33% of available chlorine Bleaching powder should be stored in a dark, cool, dry place in a closed container that is resistant to corrosion The principle in chlorination is to insure a free

5、residual chlorine of 0.05 mg/L at the end of one hour contact.,Chlorine solution,Chlorine solution may be prepared from bleaching powder If 4 kg of bleaching powder with 25% available chlorine is mixed with 20 lit. of water, it will give a 5% solution of chlorine The solution should be kept in a dar

6、k, cool and dry place in a closure container.,High test hypochlorites (HTH),HTH or perchloron is a calcium compound which contains 60 to 70% available chlorine It is more stable than bleaching powder and detoriates much less on storage.,Chlorine tablets,They are good for disinfection of small quanti

7、ty of water A single tablet of 0.5 gm is sufficient to disinfect 20 lit. of water.,Iodine,Iodine may be used for emergency disinfection 2 drops of 2% ethanol solution of iodine will suffice for one lit. of clear water A contact time of 20 to 30 minutes is needed for effective disinfection Iodine doe

8、snt react with ammonia or organic compounds to any great extent The element is physiologically active (thyroid activity) are the major disadvantage.,Potassium permagnate,It is no longer recommended for water disinfection It is not a satisfactory agent for disinfecting water, it may kill cholera vibr

9、ios, but it is of little use against other disease organism It alters the color, smell and taste of water.,Filtration,Water can be purified on a small scale by filtering through: Pateure chamberland filter Berkefeld filter Ketadyn filter The essential part of filter is the candle, which is made up o

10、f porcelain in the berkefeld filter In ketadyn filter, the surface is coated with a silver catalyst so that bacteria coming in contact with the surface are killed by the oligodynamic action of the silver ion Filter candles are liable to be lodged with bacteria and impurities.,Contd.,So they should b

11、e cleaned with by scrubbing with hard brush under running water and boiled at least once a week.,Disinfection of well,Wells are the main source of water supply in the rural area The most effective and cheapest method of disinfecting wells is by bleaching powder.,Steps in well disinfection,Find the v

12、olume of water Measure the depth of water column Measure the diameter of well Take the average reading of several measurement Compotation Volume (litres)= r2h* 1000 Find the amount of bleaching powder required for disinfection Estimate the chlorine demand of the well water, roughly 2.5 gm of good qu

13、ality bleaching powder would be required to disinfect 1,000 litres of water,Contd.,Dissolve bleaching powder in water The bleaching powder required for disinfecting the well is placed in bucket (not more than 100 gm in one bucket of water) and made into a thin paste More water is added till the buck

14、et is nearly three fourth full, the content are stirred well and the allowed to sediment for 5 to 10 minutes when lime is settled down The supernatant solution which is chlorine solution, is transferred to another bucket The lime sediment should not be poured into the well, as it increases the hardn

15、ess of water,Contd.,Delivery of chlorine solution into well The bucket containing the chlorine solution is lowered some distance below the water surface and the well water is agitated by moving the bucket violently both vertically and laterally Contact period A contact period of one hour is allowed

16、before the water is drown for use Orthotolidine arsenite test Test for the residual chlorine level at the end of one hour contact If the free residual chlorine level is less than 0.05 mg/L, the chlorination procedure should be repeated.,Hardness of water,Hardness may be defined as the soap destroyin

17、g power of water The consumer considers water hard if large amounts of soap are required to produce leather The hardness in water is caused mainly by four dissolved compounds Calcium bicarbonate Magnesium bicarbonate Calcium sulphate Magnesium sulphate .,Contd.,Hardness can be classified as: Carbona

18、te Non-carbonate The carbonate hardness was formerly designed as temporary hardness, it is due to the presence of calcium and magnesium bicarbonate The non-carbonate hardness, formerly designed as permanent hardness, it is due to presence of calcium and magnesium sulphates, chlorides and nitrates.,C

19、lassification,Soft water 300mg/L) Drinking water should be moderately hard .,Disadvantage,Hardness in water consumes more soap and detergents When hard water is heated, the carbonates are precipitated and bring about furring or scaling the of boilers, this leads to great fuel consumption Hard water

20、adversely affect cooking: food cooked in soft water retains its natural color and appearance Fabrics washed with soap in hard water do not have a long life In many industries hard water is unsuited and gives rise to economic losses Hardness shorten the life of pipes and fixtures.,Special treatment,R

21、emoval of hardness: Temporary hardness Boiling Addition of lime Addition of sod. Carbonate Permutit process Permanent hardness Addition of sod. Carbonate Base exchange method.,Boiling,Boiling removes the temporary hardness by expelling carbon dioxide, and precipitating the insoluble calcium carbonat

22、e Ca(HCO3)2= CaCO3+ H2O + CO2.,Addition of lime,Lime softening not only reduces total hardness but also accomplishes magnesium reduction Lime absorbs the carbon dioxides and precipitates the insoluble calcium carbonate Ca(OH)2 + Ca(HCO3)2= 2CaCO3 + 2H2O .,Addition of sod. carbonate,Sodium carbonate

23、removes both temporary and permanent hardness Na2CO3 + Ca(HCO3)=2NaHCO3+ CaCO3 CaSO4+ Na2CO3= CaCO3+ Na2SO4.,Air,The immediate environment of man comprises of air on which depends all forms of life Apart from supplying the life giving oxygen, air and atmospheric conditions serve several functions Th

24、e human body is cooled by the air The special sense of hearing and smell function through air transmitted stimuli Disease agent may be conveyed by air Pollution of air by dust, smoke, toxic gases and chemical vapors has resulted in sickness and deaths Mans adventures into outer space has broadened o

25、ur concept of air to exit The daily requirement of air is relatively constant ( about 10-20 m3 per day) .,Composition of air,Air is mechanical mixture of gases The normal composition of external air by volume is approximately as follows: Oxygen 21% Nitrogen 78% Carbon dioxide 0.03% Others trace.,Con

26、td.,Air is render impurities by: Respiration of man and animal Combustion of coal, gas, oil etc. Decomposition of organic matters Trade, traffic and manufacturing process gives off dust, fumes, vapors and gases Under ordinary conditions, the composition of outdoor air is remarkably constant, that is

27、 brought by certain self cleaning mechanism Wind Sunlight Rain Plant life.,Contd.,Wind: it dilutes and sweeps away the impurities by its movements Sunlight: the atmospheric temperature and sunlight play their own part by oxidizing impurities, and kills bacteria Rain: it cleans the atmosphere by remo

28、ving the suspended and gaseous impurities Plant life: the green plant utilize the carbon dioxide and generates oxygen, this process reverse during night ,The air of occupied room,Human occupancy and the activity vitiate air in occupied rooms and give a sense of discomfort The changes in air that tak

29、e place in confined places are: Chemical changes Physical changes.,Chemical changes,The air become progressively contaminated by carbon dioxide and the oxygen content decreases due to metabolic process An average person at rest gives off 0.7 c.ft. of carbon dioxide per hour; this may increase up to

30、2 c.ft. per hour during physical activity In a mixed gathering comprises all age groups, the per capita output of carbon dioxide is taken as 0.6 c.ft. per hour.,Physical activity,The most important changes due to human occupancy are the physical changes: Raise in temperature Increase of humidity Dec

31、rease in air movement Body orders Bacterial pollutions.,Raise in temperature,The indoor temperature tends to raise as a result of the emanation of body heat A man at rest gives off approx. 400 Btu. Per hour Under condition of physical exertion, the heat output may go up to 4000 Btu.,Increase of humi

32、dity,There is an increase in the relative humidity due to moisture evaporated from the skin and lungs The expired air contains about 6% of water vapor An adult person at rest releases an averages 700gms of water vapors per 24 hours in the form of perspiration,Decrease in air movements: In crowded pl

33、ace, the natural movements of air is impeded Body orders: Unpleasant odors arises from foul breath, perspiration, bad oral hygiene, dirty cloths and other sources The production of body orders depend upon the social status, age and personal hygiene of the people Bacterial pollution: The exhaled air

34、contains microorganism in suspension These are discharged during conversation, coughing, sneezing and loud talking.,Discomfort,Discomfort is a subjective sensation which people experience in ill ventilated rooms For a long time it was believed to be due to increased carbon dioxide and decreased oxyg

35、en, resulting from respiration Studies has shown that the oxygen content may be reduced to 18% and the carbon dioxide content may be raised to over 5%, without adverse effects, provided the temperature and humidity are kept satisfactory.,Contd.,In the “Black hole of Calcutta” 146 prisoners were impr

36、isoned in a room, 18*14*10 out of whom only 23 survived There were two small windows which were adequate to supply all the oxygen needs even than only 23 survived So the death were due to changes in physical condition of the air, these are temperature, humidity, air movement and heat radiation These

37、 factors determine the “cooling power” of the air with respect to the human body The problems of ventilation are physical not chemical ; cutaneous not respiratory.,Indices of thermal comfort,Thermal comfort is a complex entities These includes: Air temperature Air temperature and humidity Cooling po

38、wer Effective temperature Corrected effective temperature.,Comfort zones,Comfort zone is defined as the range of Ets over which the majority of adults feel comfortable It is quite a complex subjective experience which depends upon: Physical factors Physiological factors Psychological factors Conside

39、ring only the environmental factor “comfort thermal condition” are those under which a person can maintain normal balance between production and loss of heat, at normal body temperature and without sweating.,Contd.,corrected effective temperature deg F Pleasant and cool 69 Comfortable and cool 69-76

40、 Comfortable 77-80 Hot and uncomfortable 81-82 Extremely hot 83+ Intolerably hot 86+ .,Contd.,predicted four-hour sweat rate(P4SR) Comfort zone 1-3 litres Just tolerable 3-4.5 litres Intolerable 4.5+ litres.,Air pollution,The term air pollution signifies the presence in the ambient (surrounding) atm

41、osphere of substances (e.g., gases, mixture of gases and particulated matter) generated by the activities of man in concentrations that interfere with human health, safety or comfort, or injurious to vegetation and animals and other environmental media resulting in chemicals entering the food chain

42、or being source of human exposure.,Source of air pollution,The main source of air pollution are: Automobiles Industries Domestic sources Miscellaneous.,Automobiles,Motor vehicles are a major source of air pollution throughout the urban areas. They emit hydrocarbons, carbon dioxide, lead, nitrogen ox

43、ides and particulate matter In strong sunlight, certain of these hydrocarbons and oxides of nitrogen may be converted in the atmosphere into photochemical pollutants of oxidizing nature.,Industries,Industries emit large amounts of pollutants into the atmosphere Combustion of fuel to generate heat an

44、d power produces smoke, sulphur dioxide, nitrogen dioxide and fly ash Many industries discharges carbon monoxide, carbon dioxide, ozone, hydrogen sulphide and sulphur dioxide Industries discharged their wastes from high chimney at high temperature and high speed.,Domestic sources,Domestic combustion

45、 of coal, wood or oil is a major source of smoke, dust, sulphur dioxide and nitrogen dioxide The London disaster of air pollution in 1952 in which thousands had died was due to domestic coal burning The most direct and important source of air pollution affecting the health of many people is tobacco

46、smoke.,Miscellaneous,These comprises burning refuse, incinerators, pesticides spraying, natural sources like wind borne dust, fungi, molds, bacteria and nuclear energy.,Metrological factors,The level of atmospheric pollution at any one time depends upon metrological factors: Topography Air movement

47、Climate Wind help in the dispersal and dilution of pollutants If the topography is dominated by mountains or tall buildings the winds become weak and calm, and pollutants tend to concentrate in the breathing zone.,Contd.,The vertical diffusion of pollutants depends upon the temperature gradient When

48、 there is rapid cooling of lower layers of air (temperature inversion), there is little vertical motion and the pollutants and water vapors remain trapped at the lower levels and the result is “smug” ,Air pollutants,More than 100 substances which pollute air have been identified The importants are:

49、Carbon monoxide Sulphur dioxide Lead Carbon dioxide Hydrocarbons Cadmium Hydrogen sulphides Ozones Polynuclear aromatic hydrocarbons (PAH) Particulate matter.,Carbon monoxides,CO is one of the most common and widely distributed air pollutants It is a product of incomplete combustion of carbon contai

50、ning materials, such as in: Automobiles Industrial process Heating facilities Incinerators Estimates of man made carbon monoxide emission vary 350-600 million tones per annum.,Sulphur dioxide,Sulphur exits in air in several forms such as: Sulphur dioxide Hydrogen sulphides Sulphuric acids Sulphate s

51、alts Sulphur dioxide results from the combustion of: Sulphur containing fossil fuel Smelting of sulphur containing ores Domestic fires.,Lead,The combustion of alkyl lead additives in motor fuels accounts for the major part of all lead emissions into the atmosphere An estimated 80-90% of lead in ambi

52、ent air derives from the combustion of lead petrol The mining and smeltering of lead ores create pollution problems in some areas Children up to 6 years of age are a population at increased risk of lead poisoning Pregnant women represent a second group at increased risk because of exposure of the fe

53、tus to lead.,Carbon dioxide,This is not commonly regarded as an air pollutant It is a natural constituent of the air It does not takes part in any significant chemical reactions with other substances in the air However, its global concentration is rising above the natural level could increase global

54、 temperature enough to affect climate markedly.,Hydrocarbons,Man-made source of hydrocarbons includes: Incineration Combustion of coal Wood Processing and use of petroleum Hydrocarbons exerts their pollutant action by taking part in the chemical reactions that cause photochemical smug.,Cadmium,The s

55、teel industry, waste incineration, volcanic action and zinc production seems to account for the largest emissions Tobacco contain cadmium and smoking may contribute significantly to the uptake of cadmium Cigarettes may contain from 0.5 to 3 mcg of cadmium,Hydrogen sulphides,Human activities can rele

56、ase naturally occuring hydrogen sulphide to ambient air In industry hydrogen sulphide can be formed whenever elemental sulphur or sulphur containing substance come in contact with the organic materials at high temperature Hydrogen sulphides is form during: Coke production Wood pulp production Sulphu

57、r extraction process Oil refining process It is main toxic substances for live stokes rearing.,Contd.,Its noticeable effects are Unpleasant odor Conjuctival irritation Neurological and mental symptoms.,Polynuclear aromatic hydrocarbons (PAH),PAH are a largest group of organic compounds with two or m

58、ore benzene rings They are form especially the incomplete combustion of organic and materials as well as in natural process such as carbonization Study provide sufficient evident to exposure to PAH and health outcome: Skin cancer Lung cancer Other carcinogenic effects.,Particulate matter,Airborne pa

59、rticulate matter represents a complex mixture of organic and inorganic substances They can be divided into: Larger than 2.5mm Smaller than 2.5mm Smaller particle contains: Aerosols Combustions particles Recondensed organic and metal vapors The larger particle contains: Earth crust Fugitive dust from road Industrial dust.,Indoor air pollution,Indoor air pollution is one of the four most critical global environmental problems Rural people in developing countries