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. Uses of water Domestic Use:7% of water available is for domestic use i.e drinking, cooking, washing, bathing etc. Recommended need of water is 30 gallon/ day/ person. It includes all aspects of life which a person has in his routine life i.e bathing, washing, drinking & for toilet use. Public purpose:Water is required for public cleansing, maintenance of gardens, and swimming pools and other civic activities. Industrial Use:23% of available water is used in industries. Agricultural Use:70% of available water is used for growth of food and raw materials required.

4. 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

8. Sources of water

9. RAIN Prime source of all water. Part of rain water sinks to form ground water, part of it evaporates and some runs in streams and rivers. These events are called "water - cycle". Characteristics: Purest, bright & sparkling colour, soft water, only traces of dissolved solids, corrosive action on lead due to softness, in clean areas rain water is free of pathogens. Impurities: Picks up local impurities such as dust, soot, micro-organisms, CO2, N2, O2, Ammonia & Sulphur. In areas where NO2 and SO2 are present in atmosphere, rain water becomes acidic and the rain is called acidic rain.

10. SURFACE WATER Surface water mostly originates from rain water. It has highest chance of being polluted particularly river water because people near banks throw wastes in it. Sources of surface water are. a. Impounding reservoirs b. Rivers and streams c. Tanks, ponds and lakes. Catchments Area; It is an area from where rain water is drained into a specific reservoir area made naturally/ artificially. Peat: Decomposed organic matter containing acids is called peat. It makes water acidic, so gain ability to dissolve lead and result is lead poisoning.

11. GROUND WATER • It is in form of: • a. Wells — Deep well, shallow well, Artesian well. • Springs —Seasonal springs, thermal springs, mineral spring, shallow springs, and deep springs. • The advantages of ground water are: • a. It is usually free from pathogenic agents. • It usually requires no treatment. • Its supply is continuous. • The disadvantages of ground water are: • a. It ishigh in mineral contents • It requires pumping or some arrangement to lift the water. • Springs:A spring is ground water which finds its way to the surface because of topographical features. Cracks present in earth, water enters and comes out from other opening at a low level. So source may be quite far away such as 100-200 miles.

12. WELLSThese are artificial holes or pits dug into the earth to reach the underground water level. They constitute a very important source of water supply in villages. There are four varieties of wells:1. Shallow Wells,2. Deep Wells3. Artesian Wellsare a variety of deep wells in which water under great pressure comes out to the surface automatically4. Norton's Abyssinian Tube Wellsare really shallow wells which are bored by simply driving iron pipes 3.8 to 5 cm. in diameter and 6 to 7.62 metres deep to tap theground water. A pump is attached to the pipe to draw the water.

13. Types of aquifers and wells. In a water table well, the water table is at atmospheric pressure. In an artesian well, the water pressure is greater than atmospheric. In a flowing artesian well, the water pressure is such that it can flow freely above the ground surface

14. 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

16. Hazards of Polluted Water: • Biological Hazards • These are due to some specific agent that causes ill-health.

17. 2. Other Hazards a. GIT disturbances due to Na ++, Mg ++ & Ca++ ions, e.g) increased MgSO4 lead to diarrhea. b. Lead poisoning c. Iodine deficiency d. Fluorine deficiency e. Hardness of water f. Infant methaemoglobinemia.

18. 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.

19. 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

20. 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.

21. 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)

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

23. 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.

24. 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:

25. A complete system of water supply

26. 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.

27. Comparison of Rapid & Slow Sand Filters.

29. CHLORINATION Chlorination is the process in which chlorine is added to water for purification. Chlorinationis 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

30. 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.

31. Principles of Chlorination a. First, water should be clear and free from turbidity. b. Chlorine absorption (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 residual chlorine is 0,3 - 0.5 mg/L. e. The sum of the chlorine absorption of water and the quantity of residual chlorine (0,3-0,5 mg/l) is the chlorine’s need of water

32. 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.

33. 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.

34. 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.

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

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

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

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

40. Asaka Water Purification Plant  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

41. Agents alternative to Chlorination The ozonization of water 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.

42. Advanced Water Purification System

43. 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.

44. 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. • 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.

45. 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.

46. PURIFICATION 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

47. 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.

48. 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

49. 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.

50. C. By Filtration Water can be filtered and is purified. Different filters are. Doulton water filters have a unique 3-stage filtration system. The first stage is the Ceramic filter. This provides a physical barrier that traps and reduces parasites, particulates, turbidity, rust, and dirt greater than 0.9 microns in size. The second stage is High Density Activated Carbon, which reduces chlorine, bad taste and odor. The third stage is a Heavy Metal removing compound that reduces lead.