water supply for enviromental health.pptx

• Contribute to policy development and planning in environmental health issues at the national and regional level
• Apply identifying, sampling, analyzing, interpreting and intervene environmental pollutants
• Provide training and conduct research activities in the environment, environmental health and health related areas
• Practice CRC Legal aspects in health care, community and institutional setting practice
• Manage environmental health activities at the real working environment
• Develop intervention plan for the industries/sectors

1. Water Supply Mekelle University College health science School of Public Health Environmental Health and Behavioral Science Dept. Instructor: Tsegaluel Abay(MSc)

2. INTRODUCTION TO SAFE WATER SUPPLY

3. Introduction What is water??? Why do we need water ??? Write the public health importance of water. What is the reason that the largest portion of the water is unfit for domestic and agricultural purposes? Explain the global occurrence of water in terms of percentages

4. Cont’d … Ethiopian Situation About 75% registered OPD cases are associated to lack of basic sanitation : dysentery, diarrhea , skin and eye infections, helminthiasis , protozoal infections Proportion of diarrhea among under fives is 45% Accessibility : General population: safe water : 15% in 1984: Sanitation : 7% in 1984 Vs 8% in 1998 Less than 8% to both facilities (1998 ) The worst condition being in rural areas: about 83% to safe water and about 60% to latrine in urban Vs 20% to safe water and 1% to latrine in rural areas (1998, national plan of action, MOH)

5. Cont’d… 1.4 Role of Environmental Health in health of the people Three basic strategies: Promotion, Prevention and Control Promotion: targeted to behavioural changes mainly through provision of water ; housing improvement, basic sanitary provisions. Prevention of communicable diseases before it happens: safe water , safe food, latrine provisions, personal hygiene, proper solid waste management, vector control, etc. Control of communicable diseases through various environmental interventions

6. Cont’d… 1 .1 . Importance and use of water: Physiological needs: 70% of our body by weight A bout 2.0-2.5 litres per day needs Survival with out water very hard Most food contains water: milk about 90%, fish about 80% Water intake balance: 2-2.5L intake (1.5L drink, 0.6-1. 0L food, 0.3-0.4L body oxidation); equal loss (1.5L urine, 0.4-0.6L sweat, 0.35-0.4L breathing, 0.1-0.14L faeces; generally half of intake lost by skin and lung, and half of it by urine and faeces);

7. Cont’d… It’s important for the balance in ecology Valuable source of energy Domestic use : cleaning, washing, swimming, livestock watering Recreational purposes : swimming, boating, fishing, skiing, (lakes Langano , Ziway , etc.) Other uses: agriculture, transportation, power production, industrial use, etc.

8. Cont’d… 1 .2 Occurrence and sources of fresh water Where does the water come from?

9. Cont’d… The earth’s surface is covered by 72% of water(widely occurring substance in the world ) of which 97.2% ocean( unfit ) 2% water in frozen state( unreachable ), 0.8% only exists as available fresh water . Sources of drinking water: Surface (river, lakes, ponds, dams) Ground water (springs and wells) Rain water .

10. Cont’d …

11. During part of the water cycle, the sun heats up liquid water and changes it to a gas by the process of evaporation. Water that evaporates from Earth’s oceans, lakes, rivers, and moist soil rises up into the atmosphere.

12. The process of evaporation from plants is called transpiration . (In other words, it’s like plants sweating.)

13. As water (in the form of gas) rises higher in the atmosphere, it starts to cool and become a liquid again. This process is called condensation. When a large amount of water vapor condenses, it results in the formation of clouds.

14. When the water in the clouds gets too heavy, the water falls back to the earth. This is called precipitation.

15. Cont’d… What is water ? Chemistry : H 2 O (distilled water?? Rain Water??. It is impossible for water to exist in such form in nature. Water contains some kind of impurities . Physical characteristics : odorless , colorless, tasteless, liquid, about density 1.0. Dissolve oxygen (DO) : clear fresh water at 25C contains 9-10ppm (mg/L)of oxygen; threshold for aquatic life is 4.0ppm

16. Cont’d… Biochemical oxidation demand (BOD): the amount of oxygen needed for biodegradation of organic matter (by micro organisms in 5 days). Typical fresh natural water contains 1-2ppm; treated water: 10-20ppm; Sewage; >200ppm (Little Akaki river in AA has about 400ppm ). Chemical oxidation demand ( C OD ): the amount of oxygen needed for the decomposition of both organic and non-organic matter. Both BOD & COD: measures the strength of water pollution.

17. Impurities of water may be divided into two classes: a . Suspended Impurities Micro-organisms : they may get into water from the air with dust, etc., as rain falls, or commonly when soil polluted with human and animal wastes is washed into the water source . Suspended solids : Minute particles of soil, clay, silt, soot particles , dead leaves and other insoluble material get into water because of erosion . Toxic chemicals such as insecticides and pesticides are also included in this category. Generally , suspended solids cause taste, color or turbidity . Algae Cont’d…

18. Cont’d… Dissolved impurities Gases Minerals Plant dyes

19. Cont’d… Hardness of water- containing more than 100 mg/l of hardness expressed as calcium carbonate ( CaCO3) Hardness also be defined as water that doesn’t produce lather (foam) with soap solutions , but produces white precipitate (scum)

20. Cont’d…

21. Cont’d…

22. Cont’d…

23. Cont’d… Adverse effects: loss of soap &detergents; effects to kidney; scale formation on boiling; decreases life fabrics

24. Cont’d…

25. Cont’d… Exercise: (Assignment) Methods water softening Effects of temporary and permanent hardness Advantages and Disadvantages of hard and Soft water

26. Cont’d… Safe water It is water that does not contain harmful chemical substances, or microorganisms in concentration that could cause illness in any form or impurities that interfere with color, taste, transparency, and odour (WHO). Drinking water must be physically, chemically and microbiologically safe . Health importance Toxicity : Toxicity criteria (excess chemicals above the standard causes a health risk of acute and sub acute toxicity): Example Pb <0.05mg/l, Hg<0.001mg/l, etc. of WHO standard.

27. Cont’d… Water related diseases Water borne : the pathogen is in the water (cholera, typhoid, giardiasis, etc ). Quality matters Water washed : the water is inadequate (conjunctivitis, scabies, trachoma). Quantity matters. All water borne diseases are water washed. Water based (contact): the pathogen spends part of its life cycle in water snail or other aquatic animals ( schistosomiasis , guinea worm). Water-insect related : the pathogen carrying insect is breeding near the water and bite near it (yellow fever a viral, by Mospuitoe Aedes Egypti , malaria by Anopheles mosquitoe , dengue fever viral by Aedes mosquitoes)

28. Cont’d …

29. Cont’d… Adequate water can decrease diarrhea by 25%; Water quality alone by 16%, both by 37% (some studies) Improved latrine provision decreases diarrhea by 20% (some studies) Water supply, latrine provisions, and hygiene education decrease diarrhea significantly Objective of drinking water supply A) To supply safe and wholesome water B) Adequate supply for all purposes : cooking, washing, personal hygiene, C) Accessibility

30. Cont’d… Ground water : is that portion of the rainfall water which has percolated into the earth until it reaches an impermeable stratum ” Advantages : likely to free from contamination and pollution; does not need treatment plants if properly protected (a protected well, spring); can be accessed for individuals where it is abundant ( Ziway , etc ); Development of ground water: Types:

31. Cont’d…

32. Cont’d… Infiltration gallery: “it is a „horizontal well‟ constructed near a river bank and than connected to a large diameter vertical well in order to obtain an adequate quantity of water” Well protection: Site selection : at least 15 metres (preferably 30 meters) away and upward from any potential underground contamination; With in the well : 1) fencing (about 10m radius in rural); 2) a 3m from the surface water tight internal wall lining; 3) the well is closed (sealed) the water being drawn with a pump or drawn with a fixed bucket and rope system (windlass); 4) a raised well apron of at least one meter radius and height of >50cm; 5) a surface run of drainage channel of at least 10 meters length with a soak away pit/trench or plant irrigation.

33. Cont’d… Spring protection is G round water issued at favorable water table. Need of sanitary survey : adequacy, topography, hydrology, and potential source of contamination; Structure : eye of spring; protection box; collection box; delivery or in take pipe, over flow pipe with a screen; water gradient; diversion ditch; fencing;

34. Cont’d.. Surface water supply Occurrence : fresh water – river, lakes, ponds; Characteristics: Physical : less naturally dissolved minerals; has dissolved oxygen: 8-12 ppm; Pollution : likely to be polluted by industrial & municipal effluents affecting the water physical, biological and chemical characteristics; Self purification : sedimentation, dilution, oxidation, photosynthesis, plankton; Un polluted water has aquatic animals; animals like worms, snails, etc in its bank;

35. Cont’d … BOD (biological oxidation demand): amount of oxygen needed for aerobic microorganisms to decompose organic matter in 5 days . A water with no organic has 0 ppm; fresh surface water – 2-5ppm; domestic sewage-> 100ppm Dissolved oxygen (DO): fresh surface water has 8-12ppm; An oxygen sensitive fish can not survive <4ppm (critical level)

36. Water Quality and Safe Drinking Water Generally, water for human use is collected from various unprotected water holes , and is consumed without treatment . Naturally, water-borne diseases are prevalent among communities that consume such untreated contaminated water , and such practices must be discouraged. Water must be adequately treated before consumption , even in rural areas. Drinking water treatment systems are: Water treatment in small scale Central or large scale water treatment

37. C ont’d … 1. Treatment Of Water On A Small Scale Learning Objectives At the end of this chapter you will able to : Mention methods of treating household water supplies Describe the principal health risk associated with household water storage Design and construct different household water filtration method Mention chemicals and their dosage used in water treatment at household level.

38. Cont’d… Introduction In most rural areas and small communities in developing countries , adequate water treatment procedures are almost non-existent , mainly for economic reasons . Generally, water for human use is collected from various unprotected water holes , and is consumed without treatment . water-borne diseases are prevalent among communities Water must be adequately treated before consumption , even in rural areas .

39. Cont’d… Therefore , small-scale treatment of water in emergency situations , temporary settlement areas, at household level and areas where the municipality is not well organized is very important to reduce the problem of waterborne disease through the utilization of different methods of water treatment Treatment of household water supplies may be effected by the following methods, used singly or in combination, depending on the reliability of each method. A . Source protection

40. 41 Physical treatment process used to remove small particles, which make water cloudy B. Sedimentation

41. Option 1: Pot Settling Disadvantages : Time intensive Removes only or partially removes turbidity and pathogens Good settling requires multiple containers 42 Advantages: Low costs (for free, if container is already available) Simple and easy Source: CAWST (2009)

42. Option 2: Coagulation and Flocculation

43. 45 Coagulants Additives encourage settlement of suspended particles Forms larger particles which precipitate (fall to the bottom) Easily removed by settling or filtration Chemical coagulants: PUR – Coagulation + Chlorination Alum ( aluminum sulphate) PAC (poly aluminum chloride – liquid alum) aluminum or iron salts – i.e. ferric sulphate Plant coagulants: Moringa seeds Cactus Cactus Source: Unknown

44. Disadvantages: Time intensive Doesn’t remove all pathogens Coagulants may not available everywhere 46 Advantages: Low costs Simple and easy Traditional/indigenous practice Removes turbidity and some pathogens Alum block Source: http://: www.cdc.org [Accessed: 26.06.2010] Moringa seeds Source: Unknown

45. 47 C. Filtration Settling does not remove all flocs – further treatment is required. Filtration provides the additional opportunity for separation of small flocs or particles is any of various mechanical, physical or biological operations that separate solids from fluids Source: IFRC, 2008 Option 1: Straining Filters should be of mesh size less than 130 μm ; this should remove all infected intermediate hosts . effective in removing guinea-worm

46. 48 Disadvantages: Requires extra washing of cloth after use Cloth fibres loosen significantly the more they are used Cannot remove all bacteria and viruses Advantages: Low costs (free if extra cloths are available) Time required is minimal , simply the time it Takes to pour water through the cloth Simple and easy to reduce turbidity Known to reduce risk of cholera Source: IFRC, 2008

47. Diffuser Plate Protects the biological layer from damage when water is poured into the filter . Outlet Pipe – 6 mm (¼”) inner diameter (I.D.) Conducts water from filter base to outside . Biological Zone: Develops at the top 5-10 cm (2-4”) of the sand surface. The sand absorbs pathogens, iron, and other small particles. Sand Zone : Contains virtually no living microorganisms due to lack of nutrients and oxygen. Gravel Zone : Holds the sand in place which protects the outlet pipe from clogging and allows for the smooth flow of water . http://www.cawst.org Option 2: Bio sand Filter

48. Removes: - More than 96% of fecal coli forms -100 % of protozoa and helminthes - 50-90 % of organic and inorganic toxicants - Greater than 75% of iron and manganese  - Suspended sediments, in all or part Works mainly due to 4 mechanisms: 1. Mechanical trapping and sieving 2. Adsorption and attachment 3. Predation 4. Natural death (removes iron, turbidity, pathogens & odour ) 50 Source: A. DOUCET, ( http://commons.wikimedia.org/wiki/File:Biosand_Filter_and_Canari.JPG [Accessed: 29.04.2010]

49. Advantages: Affordable - no ongoing cost Made from locally available materials Durable High user acceptability Simple and easy to use Can effectively treat 60-80 litres /day 51 Disadvantages: Turbidity should be less than 50 NTU Takes up to 30 days to develop the biological layer Heavy, should not move after installation Filter must be used almost every day to maintain the biological layer

50. Option 2: Home candle Filter Looks like an upside-down candle, screwed into the base of the upper portion of a two container water filter Mix clay with water and sawdust or flour Compress into mold Heat in oven to vaporize sawdust and leave open pores Pore size ~ 1 – 5 micron diameter traps microorganisms and other suspended contaminants in its pores Can add more specialized filter material to remove fluoride, arsenic Silver ions released into water, inhibit bacterial enzymes

51. Advantages: Made from locally available materials Easy to transport High user acceptability Simple and easy to use Removes parasitic worms, cysts ( Crypty , Giardia), spores, bacteria 53 Disadvantages: Slower flow rate (1.5-3.0 litres per hour) Breakable Need to be replaced when damaged Need to clean filter regularly if source water is dirty Can’t guarantee water is pathogen free eg . Virus Can’t remove dissolved substance- but activated carbon

52. A ssignment: Slow sand filter Rapid sand filter

53. Option 1: Chemical disinfection - liquid chlorination(3 drops 1% Chlorine stock per 1L water Advantages: Provides residual chlorine for some protection against re-contamination Inexpensive Widely available in different countries Easy to transport Relatively quick Simple and easy to use 55 D. Disinfection Source: Uknown

54. Disadvantages: Does not deactivate parasites like Guardia , Cryptosporidium and worm eggs Requires clear water to be most effective Risk of by-product formation if water has high organic content (i.e. surface waters) Taste is unacceptable to some users Need to wait 30 minutes Users require to purchase chlorine on a continuous basis 56 Source: CAWST (2009)

55. Option 2: Solar Water Disinfection (SODIS) 57 PET (Polyethylene terephthalat ) bottles or bags (1 to 2 litres) filled with low turbidity water and exposed to sun light Exposure time: 6 hours (bright to 50% cloudy sky) to 2 days (100% cloudy sky) Advantages: Free if plastic bottles are reused Relies on renewable energy and reduces need for traditional energy Ideal to treat small quantities of water Does not change the taste of the water Bottles are convenient for safe water storage and transportation Simple and easy to use

56. Disadvantages: Time-consuming (7 hours exposure) No residual effect Requires relatively clear water to be most effective (turbidity less than 30 NTU) Requires sufficient solar radiation, therefore depends on weather and climatic conditions Not useful to treat large volumes of water

57. Cont’d… Option 3. Boiling One of most reliable methods of disinfecting water at household level. kept boiling for 15 to 20 minutes, all forms of micro-organisms, including the most resistant spores or cysts , will be destroyed . E ffective for all kinds of raw water, unless the water contains toxic chemicals which boiling cannot destroy . its flat taste Health caregivers - health education to change the habit of people towards safe water supply through boiling of water to reduce the problems of waterborne disease.

58. 62 E– Safe water storage Safe storage involves storing water in a suitable place using a clean and appropriate container For safe water storage, an appropriate container should have the following qualities: Strong and tightly fitting lid or cover Tap or narrow opening Stable base Durable Comfortable handle Allows air to enter as water is poured

59. Conventional Large Scale Water Treatment Learning Objectives At the end of this chapter students will be able to: Define water treatment. Explain the main objective of water treatment. Identify the criteria required in classifying raw water treatment . Write and discuss steps in conventional large-scale water treatment .

60. Cont’d… Water treatment on a large scale is utilized where the population is larger when there is an organized municipality operating the treatment plant for the production and distribution of adequate and safe water for the community. It is different from treatment of water on a small scale ; hence, it utilizes different complicated steps of water treatment units Water Treatment –process of removing all those substances, whether biological, chemical or physical, which are potentially dangerous or undesirable in water supply for human and domestic use.

61. Cont’d… Main objective of water treatment To remove pathogenic organisms and consequently to prevent waterborne disease. To remove substance which impart color, taste or odor to the water. To remove excess or undesirable chemicals or minerals from the water. To regulate essential elements or chemicals that may be in excess or lacking in a certain water supply (e.g. fluoridation or de-fluoridation of water, softening of water, etc.) To remove excess or undesirable dissolved gasses.

62. Cont’d… The most important factors influencing in selection of treatment processes are : Treated water specifications . Raw water quality and its variations. Local constraints (availability of skill , manpower and funds ). Relative cost of different treatment processes.

63. Cont’d… Steps in Municipal (Conventional Large Scale ) Water Treatment Plant The process flow: 1. Preliminary water treatment T o remove any large floating and suspended solids that could obstruct flow The Source and Intake of the Raw Water Sanitary condition Better the quality of the raw water, the more the saving in treatment cost . Appropriate size of intake pipe should be installed

64. Cont’d… Screening Coarse screening- remove leaves, twigs , small fish, and so on Micro-strainer (Fine Screen )- remove algea

65. Cont,d … 2. Aeration to oxidize dissolved iron and manganese in water drawn from the ground Removal of carbon dioxide to reduce corrosion and interference with lime-soda softening ; Removal of hydrogen sulfide to eliminate odor and taste, decrease the corrosion of metals and disintegration of cement and concrete, and lessen interference with chlorination. Removal of methane to prevent fires and explosions; and Removal of volatile oils and similar odor and taste producing substances released by algae and other microorganisms.

66. Cont’d… 3. Coagulation and flocculation . Many impurities in water and wastewater are present as colloidal solids, which will not settle. Their removal can be achieved by promoting agglomeration . Coagulation is mixing water with chemicals that encourage suspended solids to coagulate into larger particles that will settle easily( increasing size) Most commonly used coagulants are : Aluminum Sulphate, Ferrous Sulphate, Ferric Sulphate, Magnesium Carbonate, Polyelectrolyte, Copper Sulphate

67. Cont’d… The principle of chemical coagulation in terms of chemical reaction suspended particles in water are in colloidal form. Colloids(1micron-100mili micron) - minute particles that exist in dispersed state in a liquid

68. Cont’d… Flocculation - gently mixing water and coagulant allowing the formation of large particles of floc

69. Cont’d… 4. Sedimentation- removal by gravitational settling of suspended particles heavier than water flow is slowed enough so that gravity will cause flocs to settle Coagulated particles fall, by gravity, through water in a settling tank and accumulate at the bottom of the tank , clearing the water of much of the solid debris and clear water moves to filtration. WATER TOWARDS FILTRATION WATER FROM COAGULATION

70. Cont’d… 6. Filtration The water passes through filters, some made of layers of sand, and charcoal that help remove smaller particles such as To reduce turbidity) To reduce number of micro-organisms To minimize the contaminants which cause undesirable taste and odor To remove any suspended solid in water . Eg : Slow sand filter, rapid sand filter, activated carbon etc

71. Cont’d… 7. DISINFECTION : A small amount of chlorine is added or some other disinfection method is used to kill microorganisms that may be in the water . The most common forms of chlorine Liquid chlorine . C alcium hypochlorite powder , Ca ( OCl )2, S odium hypochlorite solution, NaOCl , Halazone(tablet). factors that influence the disinfecting power of chlorine and its compounds. A) The quality of the water to be chlorinated

72. Cont’d… B) Contact time (30minute) C) Water Temperature(high Temp preferable) D) Presence of Ammonia Both of them are disinfectant but more time is needed

73. Cont’d… Dosage rate of chlorine The amount of chlorine or its compounds to be added to disinfect a given quantity of water depends upon several factors , chiefly: A ) The chlorine demand of the water B ) Residual chlorine Other methods Ultraviolet irradiation Ozone Boiling (for small scale)

74. Cont’d… 8. Supplementary water treatment (Assignment) Water hardness( removed by soda-lime method, ion exchange, boiling ) Fluoridation of water-removed by The Ion Exchange Process The Phosphate Compounds Process The Aluminum Compounds (Activated Aluminum) Process. c . Water desalinization R everse osmosis Electro dialysis

75. Conventional Municipal large scale Water Treatment Screening Coagulation Flocculation Sedimentation Filtration Disinfection Storage Distribution Raw water Alum Polymers Cl 2 sludge sludge sludge

76. Nitrogen removal Nitrification –conversion of ammonia to nitrate Two steps process: Oxidation of ammonium , NH 4 + , to nitrite , NO 2 2NH 4 + + 3O 2 ------2No 2 - +4H + + 2H 2 O   Oxidation of nitrite NO2 to nitrate NO3 2No 2 - + o 2 ---------nitro-bacteria-------2NO 3 - Overall reaction NH4 + + O 2------- 2H + + H 2 O+NO 3 - 1gram N uses 4.57grams of O 2 based on stoichiometry

77. Iron and Manganese Water containing excessive amounts of iron and manganese can stain clothes, discolor plumbing fixtures, and sometimes add a “rusty” taste and look to the water Surface water generally does not contain large amounts of iron or manganese, but iron and manganese are found frequently in water systems that use groundwater

78. BACTERIA AND IRON AND MANGANESE Iron and manganese in water also promote the growth of bacteria (including iron bacteria) These organisms obtain energy for growth from the chemical reaction that occurs when iron and manganese mix with dissolved oxygen when bacteria form thick slime growths on the walls of the piping system and on well screens. These shines tend to be are rust-colored from iron and black-colored from manganese Variations in flow can cause these slime growths to separate from pipe walls, resulting in dirty water in the system.

79. The growth of iron bacteria can be controlled by chlorination However, when water containing iron is chlorinated, the iron is converted from the ferrous state to the ferric state--in other words, rust--and manganese is converted into black manganese dioxide. These materials form a coating on the inside of the water main and, when they break loose, a customer will sometimes complain of “dirty” water. IRON AND MANGANESE CONTROL Methods to control iron and manganese in distribution systems include arranging for alternate water sources, adding phosphate to the water to keep iron and manganese in solution, and oxidizing and removing both by filtration.

80. Alternate Sources In some situations, abandoning a well and drilling a new one into an aquifer with a lower iron or manganese concentration may be cost-effective It may also be possible to blend the water from the well with the high concentrations with water from another source with lower concentrations Phosphate Treatment Phosphate can be added at the source to mask the effects of elevated iron concentrations in the distribution system This is effective when the water contains less than 0.3 ppm of iron or 0.1 ppm of manganese Phosphate delays the precipitation of oxidized manganese and iron, thereby greatly reducing the layer of scale that forms on the pipe The effect is called sequestration The iron or manganese ion is surrounded by a chain of phosphate molecules and is not allowed to precipitate in the water

81. Pyrophosphate, tripolyphosphate , and metaphosphate may be effective as iron and manganese sequestering agents However, the most effective seems to be sodium phosphate in low concentrations The proper dose and type of phosphate should be selected only after bench-scale testing is performed by a qualified technician or consultant. Phosphate feed points should be separated from the chlorine injection point by as much distance as possible The phosphate feed point should also be ahead of the chlorine injection point If phosphate is fed after chlorine, there is a possibility the iron and manganese will be oxidized by the chlorine before sequestering can take place causing iron and manganese precipitates to be pumped out into the distribution system

82. The amount of phosphates required to sequester iron and manganese generally has to be approximately two parts actual phosphate (as product) for one part of iron and manganese It is also important to remember that a chlorine residual must be maintained throughout the distribution system to control bacterial growth The chlorine residual should be greater than 0.2 ppm at the most distant part of the system If the total detention time in the distribution system exceeds 72 hours, the phosphates may break down and release the iron and manganese in the outer portions of the system If the detention is exceeded, the iron or manganese problem may not be resolved with phosphate.

83. Removal Filtration Removing iron and manganese from drinking water instead of sequestration it is recommended if the water contains over 0.3 ppm of iron or 0.05 ppm of manganese These elements can be removed during softening with lime, but most commonly iron and manganese is removed by filtration after oxidation (with air, potassium permanganate, or chlorine) Gravity and pressure filters are both used, with pressure filters being the more popular.

84. Oxidation with aeration Iron is easily oxidized by atmospheric oxygen Aeration provides the dissolved oxygen needed to convert the iron and manganese from ferrous and manganous (soluble) forms to insoluble oxidized ferric and manganic forms It takes 0.14 ppm of dissolved oxygen to oxidize 1 ppm of iron, and 0.27 ppm of dissolved oxygen to oxidize 1 ppm of manganese

85. Fluoride removal Fluoride is a normal constituent of natural water samples Its concentration, though, varies significantly depending on the water source Geological and manmade sources contribute to the occurrence of fluoride in water, the major contribution comes from geological resources Except in isolated cases, surface waters seldom have fluoride levels exceeding 0.3 mg/l.

86. Over the years groundwater has generally been considered to be a protected and safe Source of water, fit for drinking without treatment, as the main focus has been on the bacteriological quality of potable water Little consideration used to be given to the risks of chemical pollution, particularly to the presence of elevated levels of fluoride, arsenic and nitrate in groundwater Consumption of water having excess fluoride over a prolonged period leads to a chronic ailment known as fluorosis Incidence of high-fluoride groundwater has been reported from 23 nations around the globe It has led to endemic fluorosis, which has become a major geoenvironmental health issue in many developing countries

87. Health impacts of excess fluoride in potable waters Low dental caries incidence rates demonstrate that fluoride concentrations of up to 1.0 mg/l in potable water are beneficial to the oral health of children and, to a lesser extent, Adults In several developed countries fluoridation of water supplies is practised if the natural concentration is below the desired level Recently, however, fluoridation of drinking water has been questioned and many countries have expressed concerns over this practice due to the adverse health effects of fluoride. Dental fluorosis, also called “mottled enamel”, occurs when the fluoride level in drinking water is marginally above 1.0 mg/l When the above manifestations are seen in an adult, they clearly indicate that the person has been exposed to high fluoride levels during her or his childhood.

88. Taking health effects into consideration, the World Health Organization (1996) has set a guideline value of 1.5 mg/1 as the maximum permissible level of fluoride in drinking Waters However, it is important to consider climatic conditions, volume of water intake, diet and other factors in setting national standards for fluoride As the fluoride intake determines health effects, standards are bound to be different for countries with temperate climates and for tropical countries, where significantly more water is Consumed Water is generally the major route of fluoride intake, exposure from diet and air may become important in some situations However, in many cases, the required data on different routes of exposure may be lacking Data obtained by monitoring fluoride levels in local water supplies and the incidence of fluorosis in the local population can be used to arrive at the appropriate standards.

89. Fluoride control options Search for alternative sources If fluoride concentration in a community’s water supply is significantly and consistently beyond the permissible level, it is essential to consider remedial measures to combat fluorosis The first choice should be to search for water with a lower fluoride level. Options are: (a) Provision of a new and alternate source of water with acceptable fluoride levels It may be possible to get a safe water source in the vicinity by drilling a new well and/or drawing the water from different depths, as leaching of fluoride into groundwater is a localized phenomenon. Periodic monitoring is needed though, as mixing of water from different aquifers with different fluoride concentrations can occur.

90. ( b) Transporting water from a distant source This may lead to lasting benefits, but initial cost will be high. Such an approach has been implemented in endemic fluorosis areas in few countries. (c) Blending high fluoride with low fluoride water Mixing high and low fluoride waters so as to bring the concentration within permissible levels can be an appropriate long-term solution provided the low fluoride source is available within reasonable distance and is of acceptable quality with respect to other characteristics (d) Dual water sources If there are sources with both high and low fluoride levels available to the same community, the source having low fluoride levels can be strictly limited to drinking and cooking.

91. Defluoridation of water When none of the above options is feasible or if the only solution would take a long time for planning and implementation, defluoridation of drinking water has to be practiced Two options are then available: ( i ) the central treatment of water at the source (ii) the treatment of water at the point of use that is, at the household level In developed countries treatment at the source is the method adopted

92. Cont’d … Water quality control and surveillance Water Quality : Water safety in terms of physical, chemical, and biological acceptability. Free from pathogenic organisms; Containing no chemical that have an adverse effect on human (acute and chronic); Fairly clear: low turbidity, little colour; No saline (salty); Containing no chemicals that cause an offensive taste or smell; Not causing corrosion or encrustation of water supply system, nor staining clothes washed in it.

93. Cont’d … Types of water surveillance: Sanitary survey: topography, hydrology, and epidemiological assessment. Its aim is to detect any possible source of contamination, detect any leakages; identify if the system is protected as required . Laboratory surveillance: sampling, laboratory test for chemical, biological, and physical tests.

94. Cont’d …

95. Cont’d … NB: X/Y: highest desirable level/maximum permissible leve l. Highest desirable level is a requirement whose fulfillment is desirable but whose non-fulfillment will not be sufficient cause for disqualification of the water for drinking and domestic use . Maximum permissible level is a requirement level whose non fulfillment would disqualify the water for drinking and domestic use because of its probable hazard to health. This is the level that can be tolerated with out significant health risks. The level is accepted if there seems resource limitation for water projects implementation. The final target for this level must be to achieve the desirable quality level as above specified.

96. Cont’d …

97. Cont’d… Requirements for bacteriological analysis of water  Both pathogenic and non pathogenic organisms may exist in water  There should be both technically and economically feasible to detect one of them  Coliforms are chosen as an indicator  Co-exist with pathogens in water and sewage  Their number is proportional to the extent of pollution  Present in greater numbers than pathogens  Greater survival than pathogens  Absent in unpolluted water  Easy and fast to detect in lab  Harmless to animal and human  Good indicator of faecal contamination from animals and humans .

98. END OF THIS CHAPTER Thank you!