Purification of water


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What is purification of water
Why to purify
Process (Standard level for Class 9 below)
Results if not purified

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Purification of water

  2. 2. DEFINATION Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids and gases from contaminated water to make it fit for drinking.
  3. 3. Need for Water Purification  Although reasonably pure, it is always variable due to seasonal variations, regional variation in water quality.  For removing impurities and control microbes to avoid contamination.  The treatment of water majorly depends on water’s chemistry and contaminants, influenced by, e.g. rainfall, erosion, pollution, etc. IF PURIFICATION IS NOT DONE IT MAY LEADS TO VARIOUS DISEASES DUE TO THE MICROBES PRESENT IN IT.
  4. 4. Process of Purification of Water The process of purification of the water majorly involves four methods i.e. :-  Sedimentation tank  Loading tank  Filtration tank  Chlorination tank
  5. 5. Sedimentation Tank Water entering into the sedimentation tanks contains suspended particles (sediments). These sediments settle to the bottom of the tanks forms sludge which is then driven to the outlet using scrappers so that the water is free from suspended material like rocks, soil, etc.
  6. 6. Loading Tank The addition of inorganic coagulants such as aluminium sulphate (or alum) or iron (III) salts such as iron(III) chloride cause several simultaneous chemical and physical interactions on and among the particles. Within seconds, negative charges on the particles are neutralized by inorganic coagulants. Also within seconds, metal hydroxide precipitates of the aluminium and iron (III) ions begin to form. These precipitates combine into larger particles under natural processes such as Brownian motion and through induced mixing which is sometimes referred to as flocculation. The term most often used for the amorphous metal hydroxides is “floc.” Large, amorphous aluminium and iron (III) hydroxides adsorb and enmesh particles in suspension and facilitate the removal of particles by subsequent processes of sedimentation.
  7. 7. Filtration Tank In this tank the water moves vertically through sand which often has a layer of activated carbon or anthracite coal above the sand. The top layer removes organic compounds, which contribute to taste and odour. The space between sand particles is larger than the smallest suspended particles, so simple filtration is not enough. Most particles pass through surface layers but are trapped in pore spaces or adhere to sand particles. Effective filtration extends into the depth of the filter.
  8. 8. Chlorination Tank The most common disinfection method involves Chlorination. Chlorine is a strong oxidant that rapidly kills many harmful micro-organisms. Because chlorine is a toxic gas, there is a danger of a release associated with its use. This problem is avoided by the use of sodium hypochlorite, which is a relatively inexpensive solution that releases free chlorine when dissolved in water. Chlorine solutions can be generated on site by electrolyzing common salt solutions. After water passing from this Chlorination tank the water is supplied to our houses.
  9. 9. IF Water is not Purified Water is another fertile source of disease, many organic and inorganic impurities making their way into it. It is to the former that its unhealthful is generally due. Nearly all water from the earth contains some mineral ingredients, few of which are harmful, some of which are healthful. The waters of many mineral springs serve as remedies for serious disorders of the system. The chief source of water pollution lies in organic impurities, which are carried through the soil from cesspools, manure heaps, and similar sources into wells, or are emptied by sewers into the rivers from which many cities now derive their drinking water. The lack of sufficient water may also be a cause of disease. The person and clothes are not properly washed, houses and streets are dirty, and the sewers become clogged with filth. As a result there is a general lower state of health of the community, and typhoid fever and diarrhoea may be prevalent.
  10. 10. Diseases caused by Impure water CHOLERA Cholera, whose germs are now thought to be conveyed only by water. The great epidemic at Hamburg in 1892, was traced to sewage water from cholera patients getting into the river Elbe, which supplies the city with water. This frequently, perhaps almost wholly, comes from a like distribution of the bacterial germs of the disease by water. Typhoid fever has been traced to this cause in numerous instances. This was the case at Over Darwin in 1874, when a drain containing the excreta of a typhoid patient was blocked, and its contents got in the main pipe of the water supply. As a result, out of a population of22,000 there were 2,035 cases of typhoid fever and 104 deaths. In Bangor, in 1882, there occurred an epidemic of typhoid fever, affecting 540 persons out of a population of10,000, of whom 42 died. This was found to be caused by the excreta of a single typhoid patient getting into a small stream which discharged into the river supplying the town with water.
  11. 11. Diphtheria Diphtheria is probably conveyed and caused by impure water, but this is not yet absolutely proved. Dysentery is well known in tropical countries to be caused by impure water, as was proved by an outbreak at Cape Coast Castle, where it was caused by the passage of sewage into one of the drinking tanks. Diarrhoea has been caused in epidemic form by impure water, as was shown in the old Salford jail, where the untrapped overflow pipe from a cistern of drinking water communicated with a sewer, and the water had thus absorbed sewer gas, and probably germs.