WATER (PUBLIC HEALTH DENTISTRY)

This powerpoint covers all important topics regarding WATER.
Purification ,storage, chlorination and many more ....

For any queries contact @Deepacasm
E-mail :- [email protected]

1. WATER SUBMITTED BY : DEEPAK NEUPANE (DEPARTMENT OF PUBLIC HEALTH DENTISTRY) UNIVERSAL COLLEGE OF DENTAL SURGERY BHAIRAHAWA,NEPAL \

2. CONTENTS INTRODUCTION POTABLE WATER SOURCES OF WATER GUIDELINES OF DRINKING WATER QUALITY PURIFICATION OF WATER CONCLUSION

3. INTRODUCTION Good oral health 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 water has 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 DRINKING WATER 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 Bacteriological indicators:  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 is recommended  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  The presence 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 aromatic hydro 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  Hardness can 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  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

17. PURIFICATION OF WATER ON LARGE SCALE The contents of water purification system comprise of  Storage Filtration Chlorination STORAGE During Storage ,considerable amount of purification takes place by Physical action  Chemical action Biological

18. FILTRATION Filtration is the second stage in the purification of water . The biological or "slow sand" filters The rapid sand or mechanical filters

19. SLOW SAND OR BIOLOGICAL 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 bed of 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 under drainage 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 the bed 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 : SLOW SAND FILTER

24. RAPID SAND OR MECHANICAL 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 OR MECHANICAL 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 unit of filter bed has a surface of 80-90m 2    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 SAND FILTER

28.     CHLORINATION    Chlorination is a supplement 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.

29. 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.

30. METHODS USED Chlorine is applied 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.

31. OTHER AGENTS USED FOR WATER PURIFICATION  Ozonation Ultraviolet irradiation PURIFICATION OF WATER ON A SMALL SCALE  Household purification of water : 1)Boiling  2)Chemical disinfection 3)Filtration

32. DISINFECTION OF WELLS Wells are 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

33. CONCLUSION Environmental health is systematic 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.