SMALL SCALE PURIFICATION OF WATER.pptx

These slides show a detailed explanation of Small Scale Purification of water and Chlorination. That include principles of chlorination, test of chlorinated water, Methods of small scale purification, Disinfection of wells. This presentation is aiming to inculcate a deep understanding of water purification and chlorination in students.

1. Dr PRANAV MK MPH SCHOLAR Amrita institute of medical sciences , KOCHI CHLORINATION & SMALL SCALE PURIFICATION OF WATER

2. INTRODUCTION Purification water is of great importance in community medicine. 2 types : large scale purification of water. Small scale purification water.

3. Large scale purification water comprise the following measures : Storage Filtration Disinfection

4. CHLORINATION Action of chlorine Hydrochloric and hypochlorous acid formed when chlorine is added to water. Disinfecting action of chlorine is largely due to hypochlorous acid . When pH exceeds 8.5 chlorine is unreliable as a disinfectant. Water to be chlorinated should be free from turb idity.

5. Principles of chlorination Water to be chlorinated should be free from turbidity. Chlorine demand of water should be estimated i.e ; chlorine demand = difference between amount of chlorine added and amount of residual chlorine remaining at the end of specific period of contact ( usually 1 hour) at a given pH and temperature of water. Contact period of at least 1 hour of free residual chlorine essential .(0.5mg/L)

6. Break point chlorination Break point the point at which the chlorine demand of water is met . Addition of further chlorine causes free chlorine to appear. Is essentially controlled superchlorination .

7. Superchlorination Comprises the addition of large doses of chlorine to water and removal of excess chlorine after disinfection. Applicable to heavily polluted water whose quality fluctuates considerably.

8. Methods For disinfecting large bodies of water, chlorine is applied as : Method of choice : Chlorine gas , chloramine, perchloron . Chlorine gas equipment : Paterson’s chloronome . Chloramine : chlorine + ammonia. Perchloron – HTH.

9. Test of chlorinated water Orthotolidine test (OT) test Enables determination of both free and combined chlorine in water. Procedure Add 0.1 ml of reagent to 1ml of water Free chlorine : after 10 seconds compare yellow colour produced against standards Free + combined chlorine : check yellow colour after 15-20 minutes .

10. Orthotolidine – Arsenite (OTA) test Modification of OT test. Performed to separately determine : Free chlorine Combined chlorine

11. SMALL SCALE PURIFICATION OF WATER

12. METHODS

13. BOILING To be effective : Rolling boil : 10-20 minutes It kills all the bacteria ,spores , cysts and ova – also removes hardness – by driving off carbon dioxide and precipitating calcium carbonate Boiled water should be stored in same container – to avoid contamination

14. CHEMICAL DISINFECTION

15. Bleaching powder Bleaching powder or chlorinated lime (caocl2) : white amorphous with pungent smell of chlorine. Contain 33 % available chlorine – when freshly made. Rapidly loss of chlorine content upon exposure to – light , air, moisture. Target : free residual chlorine of 0.5 mg/L at the end of one hour.

16. Chlorine solution May be prepared from bleaching powder Similar properties to bleaching powder

17. High Test Hypochlorite HTH is a calcium compound with 60-70% available chlorine . More stable than bleaching powder

18. Chlorine tablets Various types available. (trade names VIZ, halazone tablets.) .05 g tablet sufficient to disinfect 20L of water.

19. Iodine May be used for emergency disinfection of water 2 drops of 2 % ethanol solution of iodine – required for 1 L of clear water. Contact time 20-30 minutes Disadvantage : high cost Physiological active ( thyroid )

20. Potassium permanganate No longer recommended for disinfection of water Kills vibrio cholerae , but ineffective against other pathogen Disadvantage : Alters – colour , taste , smell of water

21. FILTRATION

22. Can be used for : To remove bacteria , but not viruses Only with clean water

23. Ultraviolet irradiation A film of water is exposed to UV radiation at 254 nm wavelength. The water should be free from : Turbidity Suspended /colloidal impurities

24. Advantages Short duration of exposure No alteration of taste or odour No harmful effects due to overexposure Disadvatages No residual effect Expensive

25. Reverse osmosis Used to make water chemically and micro biologically potent : By reducing Total dissolved solids Hardness Heavy metals Pathogens

26. Disinfection of wells

27. Find volume of water in the well Measure depth of water column (h) in meters. Measure diameter of well (d) in meters Substitute above value in formula : Value (liters) = 3.14*d^2*h * 1000 4 1 cubic metre = 1000 litres of water.

28. Found amount of bleaching powder required for disinfection Estimate chlorine demand using Horrock’s apparatus 2.5 g good quality bleaching powder required to disinfect 1000 liters of water

29. Dissolve bleaching powder in water Place bleaching powder (<100g) in a bucket and make into thin paste. Add water and make solution till 3/4 th of the bucket. Stir the contents well , allow to sediment * 5-10 minutes. Transfer the supernatant ( chlorine solution ) to another bucket. Discard chalk / lime residue.

30. Deliver chlorine solution into well Lower bucket containing chlorine solution below water surface. Agitate water by violently moving vertically and horizontally several times.

31. contact period Allow a Contact Period between the Chlorine and Water - Contact period o f 1 hour allowed before anyone is permitted to draw water from the well

32. Test for residual chlorine Orthotolidine Arsenite Test is then performed at the end of one hour contact period. This is done to check the level of free residual chlorine OTA test : if free residual chlorine level is < 0.5 mg/L : repeat chlorination process

33. DOUBLE POT METHOD

34. THANK YOU