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![REMOVAL OF HARDNESS
Hardness can be removed by :-
• Boiling
• Addition of Lime [Ca(OH)2]
• Addition of sodium carbonate
• Permutit process (Base exchange process)
PURIFICATION OF WATER
It can be done by :-
1. on a large scale
2. on a small scale](https://image.slidesharecdn.com/waterdeepakneupanefinal-210223172042/75/WATER-PUBLIC-HEALTH-DENTISTRY-16-2048.jpg)
Uploaded byDeepak Neupane
WATER (PUBLIC HEALTH DENTISTRY)
This document discusses water purification. It defines potable water and lists domestic, public, industrial, and agricultural water uses. Sources of water include rain, surface water, and ground water. Guidelines for drinking water quality cover acceptability, microbiological, chemical, and radiological aspects. Purification methods for large scale include storage, filtration using slow sand filters or rapid sand filters, and chlorination. Small scale purification involves boiling, chemical disinfection, and filtration. Proper well disinfection is also discussed.
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Similar to WATER (PUBLIC HEALTH DENTISTRY)
WATER (PUBLIC HEALTH DENTISTRY)
- 1. WATER SUBMITTED BY :DEEPAK NEUPANE (DEPARTMENT OF PUBLIC HEALTH DENTISTRY) UNIVERSAL COLLEGE OF DENTAL SURGERY BHAIRAHAWA,NEPAL
- 2. CONTENTS INTRODUCTION POTABLE WATER SOURCES OFWATER GUIDELINES OF DRINKING WATER QUALITY PURIFICATION OF WATER CONCLUSION
- 3. INTRODUCTION • Good oralhealth requires a clean water supply for sufficient for brushing and cleaning teeth regulary from an early age. • Poor oral hygiene may result in periodental probles since the dental plaque may induce gingival inflammation and deep pockets. • Fluroide intake from drinking water and balanced loe sugar diet are probably the most important factor for reducing dental caries. • Lack of clean water for basic oral hygiene may tip the balance towards earlier and more severe pattern of caries.
- 4. POTABLE WATER Potable waterhas been defined as water that is; -Free from pathogenic agents -Free from harmful chemical substances -Pleasant to taste, ie free from color and odor -Useful for all domestic needs.
- 5. USES OF WATER •Domestic uses - drinking, cooking • Public purposes –cleaning streets and fire protection • Industrial uses – factories • Agricultural purposes – irrigation
- 6. SOURCES OF WATER •RAIN • SURFACE WATER -Impounding reservoirs -Rivers and streams -Ponds and lakes -Sea water • GROUND WATER
- 7. GUIDELINES FOR DRINKINGWATER QUALITY 1) ACCEPTABILITY ASPECTS Physical parameters Drinking Water Should be free from turbidity. Water with turbidity of less than 5 Nephelometric turbidity units (NPU) is acceptable. Should be free from color. The guideline value is up to 15 true color units Should be free from taste and odour.
- 8. Inorganic constituents • Chlorides: The standard prescribed for chloride is 200 mg/litre. The maximum permissible level is 600 mg/litre . Any excess over the normal range should arouse suspicion of water contamination . • Hardness : Drinking water should be moderately hard .1-3mEq/L (50-150) mg/litre. • Ammonia : Natural levels in ground and surface waters are usually Below 0.2 mg/litre. • PH : An acceptable pH for drinking water is in between 6.5 and 8.5 • Hydrogen sulphide : The test and odour threshold of hydrogen sulphide in water are estimated to be between 0.05 and 0.1 mg/litre.
- 9. • Iron :Anaerobic ground water may contain ferrous ion at concentration upto several mg/litre without discoloration or turbidity in water . However ,on exposure to the atmosphere , the ferrous ion oxidizes to ferric ion , giving a reddish brown color to the water .Iron also promotes the growth of iron bacteria. • Sodium : The taste threshold concentration of sodium in water depends on the associated anion and temperature of the solution. • Sulphate : The presence of sulphate in drinking water can cause noticeabe taste .Taste impairment is minimal at levels below 250mg/litre. • Total dissolved solids: The palatability of water with total dissolved solids(TDS) level of less than 600mg/litre is generally considered to be good • Zinc : It imparts an undesirable astringent taste to water. The threshold concentration is 4mg/litre
- 10. • Mangenese :concentrations below 0.1 mg/litre are usually acceptable. At levels about 0.1 mg/litre , manganese causes an undesirable taste in beverages. • Dissolved Oxygen :Deplition of dissolved oxygen in water supplies can encourage microbial reduction of nitrate to nitrite and sulphate to sulphide , giving rise to odour problem. • Copper : The presence of copper above 1mg/litre may inrterfere with the intended domestic uses of water. • Aluminum : The concentration should not exceed 0.2 mg/litre.
- 11. 2) MICROBIOLOGICAL ASPECTS Bacteriologicalindicators: Ideally , drinking water should not contain any pathogenic microorganisms. It should also be free from bacteria indicative of pollution with excreta. The Primary bacterial indicators recommended for this purpose are:- • Coliform Organisms Faecal group -> E.coli Non Faecal group -> Klebsiella aerogens • Faecal streptococci • Clostridium perfinges
- 12. Virological aspects It isrecommended that to be acceptable,drinking water should be free from any virus which is infectious to man. Biological aspects Protozoa: Drinking water should not contain any pathogenic intestinal protozoa Helminthes: A single mature larva or fertilized egg can cause infection and such infective stages should be absent from drinking water. Free living Organisms: Free living organisms that may occur in water are fungi and algae , which gives water a bad odor and taste.
- 13. 3) CHEMICAL ASPECTS Thepresence of certain chemicals in excess of prescribed limits may make water non potable. Inorganic constituents Arsenic Lead Cadmium Mercury Chromium Nitrate and Nitrite Cyanide Selenium Fluoride
- 14. Organic constituents: Polynuclear aromatichydro carbons Pesticides 4)RADIOLOGICAL ASPECTS The effects of radiation exposure are called somatic, if they become manifest in the exposed individual and hereditary if the affect the descendants . The activity of a radioactive material is the number of nuclear disintegration per unit time. The unit of activity is a becquerel (Bq) 1 Bq= 1 disintegration per second Gross alpha activity 0.1 Bq/L Gross beta activity 1.0 Bq/L
- 15. HARDNESS OF WATER Hardnesscan be defined as the soap destroying power of water CAUSES OF HARDNESS • Calcium Bicarbonate • Magnesium Bicarbonate • Calcium Sulphate • Magnesium Sulphate DISADVANTAGES OF HARDNESS • Hard water consumes more soap and detergents. • When hard water is heated ,carbonates gets precipated and bring about furring or scaling of boilers leading to increased fuel consumption ,loss of efficiency and sometimes boiler explosions. • It adversely affects cooking by altering its color and appearance • Fabrics washed with hard water do not have long life • It is unsuited in many industrial processes and give rise to economic losses. It shortens the life of pipes and fixtures. CLASSIFICATION LEVEL OF HARDNESS(mEq/Litre) Soft water less than 1 (<50mg/L) Moderately hard 1-3 (50-150 mg/L) Hard water 3-6 (150-300 mg/L) Very Hard Over 6 (>300 mg/L)
- 16. REMOVAL OF HARDNESS Hardnesscan be removed by :- • Boiling • Addition of Lime [Ca(OH)2] • Addition of sodium carbonate • Permutit process (Base exchange process) PURIFICATION OF WATER It can be done by :- 1. on a large scale 2. on a small scale
- 17. PURIFICATION OF WATERON LARGE SCALE The contents of water purification system comprise of 1. Storage 2. Filtration 3. Chlorination STORAGE During Storage ,considerable amount of purification takes place by • Physical action • Chemical action • Biological
- 18. FILTRATION Filtration is thesecond stage in the purification of water . • The biological or "slow sand" filters • The rapid sand or mechanical filters
- 19. SLOW SAND ORBIOLOGICAL FILTERS Elements of a slow sand filter: • 1) Supernatant(raw) water • The depth of the supernatant water above the sand bed • varies from 1 to 1.5 meters. • It provides a constant head of water so as to overcome the resistance of the filter bed and therby promote the downward flow of the water into the sand bed.
- 20. 2) A bedof graded sand The thickness of the sand bed is about 1 metre.The sand Grains have an effective diameter between 0.2 and 0.3mm VITAL LAYER The slimy growth covering the surface of sand bed is known as "Schmutzdecke",vital layer,zoogleal layer or biological layer . This layer consists of a thread like algae,plankton,diatoms and bacteria. The VITAL LAYER is the "heart" of the slow sand filter.It removes Organic matter ,holds back bacteria and oxidizes ammonical nitrogen into nitrates and helps in purifying the water.
- 21. 3) An underdrainage system At the bottom of the filter bed,there is under draining system. It consists of perforated pipes which not only provides an outlet for filtered water but also supports the filter medium above. FILTER BOX The filter box is an open rectangular box,2.5 to 4 meters Deep and is built wholly or partly below ground. The walls may be made of stone,brick or cement. 4) A system of filter control values Filter control values are are present to maintain a constant rate of filtration.
- 22. FILTER CLEANING When thebed resistance increases to such an extent that the regulating valve has to be kept fully open,it is time to Clean the filter bed.The supernatant water is then drained off and the sand bed is cleaned by scraping off the top portion of the sand layer to a depth of 1-2 cm.After 20 or 30 scrapings ,the thickness of the sand bed will have reduced and a new bed is constructed.
- 23. Fig : SLOWSAND FILTER
- 24. RAPID SAND ORMECHANICAL FILTERS The steps involved are: 1) Coagulation:The raw water is first treated with a chemical coagulant such as alum. 2) Rapid mixing:The treated water is then subjected to violent agitation in a "mixing chamber"for a few minutes.This allows a quick and thorough dissemination of alum throughout the bulk of water. 3) Flocculation:This phase involves a slow and gentle stirring of the treated water in a "flocculation chamber" for about 30 minutes.This results in the formation of thick,Copious,white flocculent precipitate of aluminium hydroxide.
- 25. RAPID SAND ORMECHANICAL FILTER 4) Sedimentation: The coagulated water is then led into sedimentation tanks where it is kept for 2-6 hours , when the flocculant precipitate together with impurities and bacteria settle downn in the tank. 5) Filtration: The partly purified water is then subjected to rapid sand filtration.
- 26. FILTER BEDS Each unitof filter bed has a surface of 80-90m2 Sand is the filtering medium. The effective size of the sand particles is between 0.4-0.7mm. The depth of the sand bed is usually about 1 metre. Below the sand bed is a layer of gradedgravel,30 – 40 cm deep. BACKWASHING Rapid sand filters need frequent washing daily or weekly,depending upon the loss of head. Washing is accomplished by reversing the flow of water through the sand bed,which is called "BACKWASHING".It helps in dislodging the impurities and cleaning up the sand bed.The washing is stopped when the wash water is sufficiently clean.The whole process of washing takesabout 15 minutes.
- 27. FIG: RAPID SANDFILTER
- 29. CHLORINATION Chlorination is asupplement and not a substitute to sand filtration. Its action includes :- • Chlorine kills pathogenic bacteria,but it has no effect on spores and certain viruses except in high doses. • It oxidizes iron,manganese and hydrogen sulphide. • It destroyes taste and odour producing constituents. • It controls algae and slime organisms. • It aids coagulation ACTION OF CHLORINE When chlorine is added to water ,there is formation of hydrochloric acid and hypochlorous acid. The hydrochloric acid is neutralized by the alkalinity of the water. The Hypochlorous acid has the disinfecting action of chlorine as it ionizes to form hydrogen ions and hypochlorite ions.
- 30. PRINCIPLES OF CHLORINATION •The water to be chlorinated should be clear and free from turbidity. • The chlorine demand of water should be estimated. • The point at which the chlorine demand of water is met is called the "break point".If further chlorine is added beyond the breakpoint, free chlorine begins to appear in the water • The free residual chlorine should be present for a contact period of at least one hour to kill bacteria and viruses. • The minimum recommended concentration of chlorine is 0.5mg/litre for one hour . • The sum of the chlorine demand of water plus the free residual chlorine of 0.5mg/l constitutes the correct dose of chlorine to be applied.
- 31. METHODS USED Chlorine isapplied either as • Chlorine gas • Chloramines • Perchloron Break point chlorination The addition of chlorine to water to a point at which free residual chlorine begins to appear is called breakpoint chlorination. Superchlorination Superchlorination comprises of the addition of larger doses of chlorine to the water and removal of excess of chlorine by dechlorination .This method is used for heavily polluted river water.
- 32. OTHER AGENTS USEDFOR WATER PURIFICATION • Ozonation • Ultraviolet irradiation PURIFICATION OF WATER ON A SMALL SCALE Household purification of water : 1)Boiling 2)Chemical disinfection 3)Filtration
- 33. DISINFECTION OF WELLS Wellsare the main source of water supply in the rural areas.The most effective and economical method of disinfecting well is bleaching powder. FIG: DOUBLE POT METHOD
- 34. CONCLUSION Environmental health issystematic conduct of a planned program designed to promote optimum health and comfort of the individual,family and community by modifying or controlling the environment ,so as to prevent illness or disability caused by interrelationships with the environment.