The lecture

1. Water as factor of health, its hygienic, endemic and epidemiologic value. Organization of drinkable water-supply. Methods of improvement of quality of drinking-water. Ecological problems and sanitary protection of objects of waters. The lecture Author: Lototska O.V.

2. Water constitutes nearly two-thirds of the total weight of the body, 79 % of blood, 80 % of brain and muscles and 10 % even of bones Its main functions are that it: • Replaces loss of fluids from tissues. • Maintains the fluidity of blood and lymph. • Helps elimination of waste material of the body. • Acts as a vehicle for dissolved food. • Helps in the secretion of digestive juices. • Regulates body temperature and acts as a distributor of body heat.

3. The population should be provided not only with enough of water, but also with qualitative water. Water should not cause any pathological change in the organism, should not cause of spread of infectious diseases, and also not to cause unpleasant sensations. • Waters, used for drink and everyday needs, • must correspond to the demands: • good organoleptic properties: refreshing temperature, transparence, colorless, no smell and no taste . • harmlessness of its chemical composition • the absence of pathogenic microorganisms • safety in the radiological attitude

4. The pollution of water sources represents the important ecological problem. Depending on type of pollution there are: chemical, physical (radioactive substances, hot water), bacterial, virus and biological. Industrial wastewater is characterized by considerable quantity of components. Major categories of water pollutant 1. Infections agents - Bacteria, viruses 2. Organic chemical - Pesticides, plastics, detergents, oil, and gasoline 3. Inorganic chemicals - Acids, caustics, salts, metals 4. Radioactive materials - Uranium, thorium, cesium, iodine, radon

5. Sources of water

6. Impure water may be purified by either of the following methods: A. Natural (a) Pounding or Storage. (b) Oxidation and Settlement. B. Artificial I. Physical Distillation. Boiling. II. Chemical Precipitation. Disinfection or Sterilization. III. Filtration "Biological" or "Slow Sand" Filtration. "Rapid Sand" or "Mechanical" Filtration. Domestic Filtration.

7. PURIFICATION OF WATER Purification of water is of great importance in community medicine. It may be considered under two headings. Purification of water on large scale Purification of water on small scale Three main steps in purification of water on large scale: Storage, Filtration, Chlorination

8. 1. Storage: Water is drawn out from source and impounded in natural or artificial reservoirs. Storage provides a reserve of water from which further pollution is excluded. Advantages Physical — About 90% of suspended impurities settle down in 24 hours by gravity. Chemical — The aerobic bacteria oxidize the organic matter present in water with the aid of dissolved oxygen. As a result the content of free ammonia is reduced and a rise in nitrates occur. Biological — 90 % of total bacterial count drops in first 5 - 7 days.

9. A complete system of water supply

10. How is water treated? Coagulation:  Alum and other chemicals are added to water to form tiny sticky particles called "floc" which attract the dirt particles.

11. Sedimentation:  The heavy particles (floc) settle to the bottom and clear water moves to filtration.

12. Filtration:  The water passes through filters that help to remove smaller particles.

13. Disinfection:  A small amount of chlorine is added to kill any bacteria or microorganisms that may be in the water.

14. Storage:  Water is placed in a closed tank or reservoir where it flows through pipes to homes and businesses in the community.

15. 2. Filtration Filtration is important because 98 – 99 % of bacteria are removed by filtration, a part from other impurities. Two types of filters are in use, they are: a. Slow sand filters (biological filters) b. Rapid sand filters (Mechanical filters)

16. Slow sand filter • Supernatant (raw) water: • Sand bed • Vital Layer • Under - drainage system

17. Filter control valves: The filter is equipped with certain valves and devices which are incorporated in the outlet pipe system maintaining a steady rate of filtration. When the vital layer becomes dense and resistance to the passage of water is increased the supernatant water is drained off Sand bed is cleaned by scrapping of the top portion of the sand layer to a depth of 1 - 2 cms. Scrapping is done 20 - 30 times. The process is known as Filter Cleaning.

18. b. Rapid Sand Filter Rapid sand filters are of two types, the gravity type and the pressure type. Both the types are in use. The following steps are involved in the purification of water by rapid sand filters. i. Coagulation: ii. Rapid mixing: iii. Flocculation: iv. Sedimentation: v. Filtration:

19. Filter Beds: Back - Washing: Rapid sand filters need frequent washing daily or weekly. Washing is accomplished by reversing the flow of water through the sand bed, which is called "back-washing". Back - washing dislodges the impurities and cleans up the sand bed.

20. Comparison of Rapid & Slow Sand Filters.

22. CHLORINATION Chlorination is the process in which chlorine is added to water for purification. Chlorination-is more effective when pH of water is around 7. Effects of Chlorine: a. Chlorine kills pathogenic bacteria, it has no effect on spores and certain viruses. b. It has germicidal effects. c. It oxidizes iron, manganese and Hydrogen sulphide d. If destroys some taste and odour producing constituents. e. It controls algae and slim organisms f. It aids coagulation

23. Action of Chlorine When Chlorine is added to water, there is formation of hypochlorous and hydrochloric acid. The hydrochloric acid is neutralised by alkalinity of the water. The hypochlorous acid ionizes to form hydrogen ions and hypochlorite ions as follows. H2O + CI2 ► HCI--+HOCI HOCI ► H++OCI“ The disinfecting action of-chlorine is mainly due to hypochlorous acid and to a small extent due to hypochloriteon.

24. Principles of Chlorination a. First, water should be clear and free from turbidity. b. Chlorine demand of water should be estimated. c. At least one hour is essential as a contact period of free residual chlorine for killing bacterial and viruses. d. Minimum recommended concentration of free chlorine is 0.5 mg/L for one hour. e. The sum of the chlorine demand of the specific water plus the free residual chlorine of 0.5 mg/l constitutes the correct dose of chlorine to be applied.

25. Methods of Chlorination a. By means of chlorine gas It is of first choice because it is cheap, quick in action, efficient and easy to apply. Chlorinating equipment is required to apply chlorine gas to water as chlorine gas is irritant to eyes. b. By means of Chloramine: Chloramines are loose compounds of chlorine and ammonia. They have slower action than chlorine. They give more persistent type of residual chlorine. They have a less tendency to produce chlorinous taste.

26. Chlorine DemandIt is the difference between the amount of chlorine added to the water and the amount of residual chlorine remaining at the end of a specific period of contact (1 hour) at a given temperature and pH of water. Residual Chlorine: Amount of untreated chlorine, remaining in the water after some time as an effective disinfecting agent i.e. 0.3 – 0.5 mg/liter Break point chlorination: The point at which the chlorine demand of water is met and if further chlorine is added free chlorine begin to appear in water Super Chlorination: It is addition of large doses of chlorine to the water and removal of excess of chlorine after disinfection.

27. Agents alternative to Chlorination a. Ozonation b. U.V. radiation The ozonization of water  Ozone has been used in water treatment since 1903. It is more effective against bacteria and viruses than chlorine and adds no chemicals to the water. Ozone cannot be stored and requires an on-site ozone generator. In general, ozonation equipment and operating costs are higher than other treatment procedures. Ozone contains three oxygen atoms. It is destroyed in water, forming atomic oxygen: O3 → O2 → O. ozonization is one of the best methods of disinfection: water is well disinfected, organic admixtures become destroyed, organoleptic features are improved. Water becomes blue and it is equated with spring water. Ozone dose is 0,5 - 6 mg/l. Sometimes, higher doses are necessary for the lighting of water and improving other organoleptic features. The time of disinfection is 3-5 min. The remaining ozone should make up 0,1 – 0,3 mg/l. The concentration of the remaining ozone 0.4 mg/l provides the reliable inactivation of 99 % viruses for 5 min.

28. Asaka Water Purification Plant

29. Advanced Water Purification System

30. Ultraviolet Light    Ultraviolet irradiation will kill bacteria by creating photochemical changes in its DNA. No chemicals are added to the water by this process. Most ultraviolet water treatment units consist of one or more ultraviolet lamps usually enclosed in a quartz sleeve, around which the water flows. The UV lamps are similar to fluorescent lamps and the quartz sleeve surrounding each lamp protects the lamp from the cooling action of water. The killing effect of the lamp is reduced when the lamp temperature is lowered. Ground water is usually a constant temperature year round and so it is possible to set a flow rate that will not lead to excess cooling.         The effectiveness of UV irradiation depends on the intensity of the light, depth of exposure and contact time. Water passes in a relatively thin layer around the lamp; therefore, water flow must be regulated to ensure that all organisms receive adequate exposure. If the water is at all turbid, or if it contains traces of iron, the effectiveness of UV is greatly reduced. In such cases, the water needs to be filtered before it reaches the UV system.

31. The maximal bactericidal effect is achieved by the waves 250-260 nm, which pass even through the 25 cm layer of transparent and decolorized water. The disinfection proceeds very quickly: vegetative forms of microorganisms die in 1-2 min. The turbidity, colour and iron salts decelerate the disinfection, decreasing the transparence of water. Consequently, it is necessary to light and decolorize water beforethe disinfection. There are some advantages of UV-irradiation over the chlorination: bactericidal rays don't denaturate the water and don't change its organoleptic features, they have wider biological action. Their bactericidal action is spread over the spores, viruses and worm eggs, resistant to chlorine. Many investigators consider this method the best for the disinfection.

32. RIFICATION OF WATER ON SMALL SCALE • House hold purification of water • Disinfection of wells • HOUSE HOLD PURIFICATION • a. By Boiling: • Water should be boiled for 5 -10 minutes. • It kills all bacteria, spores, cysts & ova. • It removes temporary hardness • Taste is altered but is harmless • b. Chemical disinfection • i) Bleaching Powder (CaOCI2) • Bleaching powder is a white amorphous powder. • Produced by action of chlorine on slaked lime. • When freshly made contains 33 % of available chlorine.It must be stored at dark, cool, dry place in a closed container that is resistant to corrosion. • In practise one cup (250 g) of laundry bleach is mixed with three cups (750 ml) of water to make a litre. Three drops of this solution are added to 1 litre water for disinfection. Contact period is 30 minutes to 60 minutes.

33. ii.) Chlorine Solution Chlorine solution may be prepared from bleaching powder. * If 4 kg of bleaching powder with 25 % available chlorine is mixed with 20 litres of water, it will give a 5% solution of chlorine. * This solution should be kept in dark, cool and dry place in closed container

34. iii. Chlorine tablets Available under different trade name e.g. Halazone One tablet of 0.5 g is sufficient to disinfect 20 litres of water. Used in camps and during travel. iv. Iodine: Two drops of 2 % ethanol solution of iodine is used. A contact period of 20 - 30 minute is sufficient for 1 litre water. DUAL CHLORINE TABLET CHAMBER UNIT — CAN HOLD UP TO 50 TABLETS v. Potassium Permanganate. It is a powerful oxidizing agent but not recommended as it alters colours, smell and taste of water.

35. C. By Filtration Water can be filtered and is purified. Different filters are. The new filtration system uses centrifugal force to spin the untreated water above the filter media (sand). This helps remove suspended solids that accumulate on the inside walls of the tank

36. DISINFECTION OF WELL Wells are main source of water in rural area. The most effective and cheapest method of disinfecting wells is by bleaching powder. Disinfection of well is required in normal days and during epidemics.

37. Steps: 1. Find volume of water in well. Measure depth of water column — (h) metres Measure the diameter of well— (d) metres Substitute (h) & (d) in: Volume (litres) = π x d2 x h x 1000 π = 3.14 4 One cubic metre - 1,000 litres of water 2. Find amount of bleaching powder required Measures by Horrock's apparatus. Roughly 2.5 gm of good quality bleaching powder would be required to disinfect 1,000 litres of water.

38. 3. Dissolve bleaching powder in water The calculated amount of bleaching powder is placed in a bucket (not more than 100 g in one bucket) and made into a thin paste. More water added till bucket is 3/4 full. The contents are stirred and allowed to stand for 5 - 10 minutes. When lime settles down, the supernatant solution which is chlorine solution is transferred to another bucket. 4. Delivery of Chlorine solution into the well. The bucket containing the supernatant chlorine solution is lowered some distance below surface water. The well water is agitated by moving the bucket violently both vertically and laterally. Note: The precipitate or lime is never entered in well because it increases the hardness of water. 5. Contact period - 1 hour contact period is required. 6. Ortho-Tolidine test: It is done to list for residual chlorine at the end of one hour. If "free" residual chlorine level is less than 0.5 mg/ litre, then procedure should be repeated, before water is drawn.

40. EXPRESS METHODS OF WATER QUALITY IMPROVING Deodorization - elimination of smack and odour of water by aeration, usage of oxidants (ozonization, dioxide of chlorine, large doses of chlorine, potassium permanganate), filtrating through a layer of absorbent coal, by introduction in water to sedimentation of absorbent coal. Deironation is carried out by spraying water with the purpose of aeration in graduation towers. Thus, bivalent iron is oxydated in ferric hydroxide, which sediments in settling tank, or delays on the filter. Softening.By an aged method of water softening is soda calcareous, at which calcium and magnesium settle in a settling tank as unsolvable salts. Today is used filtrating water through filters, which are completed by ion exchangers. Ion exchangers are firm, unsolvable, acinose stuffs, which have property to exchange their ions on ions of salts, which are solved in water.

41. Removal of hardness I.Temporary Hardness a. Boiling b. Addition of lime c. Addition of sodium carbonate d. Permutit process II. Permanent Hardness a. Addition of sodium carbonate b. Permutit process/ Base exchange process. Boiling: It removes temporary hardness by expelling carbon dioxide and precipitating the insoluble calcium carbonate. Ca (HCO3)2→ CaCO3 + CO2 + H2O Addition of Lime: It removes temporary hardness. Lime absorbs carbondioxide and precipitates the insoluble calcium carbonate. Ca (OH)2 + Ca (HCO3)2 →2 CaCO3 + 2H2O

42. Household water softeners typically use a different process, known as ion exchange. Ion-exchange devices consist of a bed of plastic (polymer) beads covalently bound to anion groups, such as -COO-. The negative charge of these anions is balanced by Na+ cations attached to them. When water containing Ca2+ and Mg2+ is passed through the ion exchanger, the Ca2+ and Mg2+ ions are more attracted to the anion groups than the Na+ ions. Hence, they replace the Na+ ions on the beads, and so the Na+ ions (which do not form scale) go into the water in their place.

43. Addition of Sodium Carbonate, It removes both temporary and permanent hardness. Na2CO3 + Ca (HCO3)2→ 2NaHCO3 + CaCOs Na2CO3 + CaSO4 →Na2SO4 + CaCO3 Base Exchange Method In this method sodium permutit is used, which is a combination complex of Na, Al and Si (Na2 Al2 Si2OH2O) Sodium permutit has property of exchanging the sodium cation for Ca++ and Mg++ ions in water. Na2 Al Si2O + H2O = Mg++/Ca++ When hard water passed, sodium permutit exchanges Mg/ Ca and is converted into calcium and magnesium permutit. With time permutit loses effectiveness, it is regenerated by adding conc. sol of NaCI. * By this process hardness of water is removed to zero. As zero hardness is corrosive, therefore a part of raw water is mixed with softened water.

44. Desalting - the sequential filtrating of water through kationite, and then through anion exchanger permits to liberate it from solvable salts and consequently use with the purpose of desalting. For desalting water on water pipes, sea courts thermal method is used which bases on evaporation of water with the following condensation of steams. Also is used electro dialysis with usage of selective diaphragms, freezing and other methods. Decontamination - at coagulation, settling and filtrating of water on waterpipes contents of radioactive substances in it is reduced only on 70-80%. For more penetrating decontamination water is filtrated through ionic exchanger of resin. Fluoridation of water - synthetic adding of fluorine bonds with the purpose of decrease of its rate by caries of teeth.

45. About 97 percent of the water on earth is in the salty oceans. People have found many ways to desalinate, the process for removing salt from seawater and brackish water. The desalination processes used most commonly today are distillation, reverse osmosis, and electrodialysis. These processes produce fresh water from salt water. Distillation is the oldest method of turning salt water into fresh water. Seawater can be distilled by simply boiling it in a teapot, and piping the steam into a cool bottle. The salt water turns to vapour under the sun's heat. The vapour rises until it hits the underside of the dome or glass, where it condenses.

46. Most modern distillation plants use a process called multistage flash distillation. This is a type of the age-old method of boiling and condensation. In flash distillation, preheated seawater flows into a large chamber in which the pressure is low. The low pressure causes some of the water to instantly turn into steam The steam is condensed into salt-free water. The seawater passes through several distillation chambers. Each of the chambers has a lower pressure than the previous chamber. Often, the final water is so pure that it is tasteless, and some salt must be tossed back in to give it flavour

47. Reverse osmosis is a widely used method for desalting seawater and brackish water. In normal osmosis, a less concentrated liquid flows through a membrane into a more concentrated liquid. Thus, if salt water and fresh water are separated in a chamber by a special semi-permeable membrane, the fresh water will flow through the membrane into the salt water. Electrodialysis is used chiefly to desalt brackish ground water and water from estuaries, or river mouths. Electrodialysis is based on the fact that when salt is dissolved in water, it breaks up into ions, or electrically charged particles, of sodium and chloride. Sodium ions carry a positive charge, and chloride ions carry a negative charge. Other desalting processes are also being studied. During the 1970's, several plants experimented with freezing as a method of desalination. When seawater freezes, the ice crystals produced are pure water in solid form. The salt is separated and trapped between the ice crystals.

48. EXAMINATION OF WATER Before water from any source is declared fit for human consumption, it is essential to carry out the following examination. For hygienic purposes the examination of water is generally done under the following heads: • Physical Examination. • Chemical Examination. • Microscopical Examination. • Bacteriological Examination.

49. 1. Physical qualities • a. Turibidity • Colour • Odour • Taste • 2. Chemical qualities: • Analysis is made to determine : • The amount of organic salts which determine the hardness of water and type of hardness. • The nature and amount of organic pollution. • The percentage and amount of poisonous metals. • The chemist determines the reaction (by means of a litmus paper or phenolphthalein), • the type and degree of hardness, • the presence of chlorides, nitrites, nitrates, ammonia (free and albuminoid) and metals such as lead, copper, iron, calcium etc., before giving his final opinion.

50. Bacteriological Indicators: The main object of bacteriological examination of water is to find out whether excretal pollution is present or not. The sewage bacteria can be divided into three groups: - E.coli and coliform group - Fecal streptococci - Clostridium perfringens. 4. Radiological Standards Gross alpha activity 3 pico curie/L Gross beta activity 30 pico curie/L