Drinking Water Standards and Treatment.pptx

Drinking Water Standards and Treatment Undergraduate Medical Students

1. Drinking Water Standards & Treatment Dr Abinesh Department of CM SVMCH&RI

2. Safe & Wholesome Water Water used by human for consumption should be safe and wholesome. It should be pleasant to taste, colorless and odorless, free from pathogenic agents and harmful chemical substances and usable for domestic purposes.

3. Uses of Water Consumption (drinking and cooking) Hygiene (bathing and laundry) Amenity (gardening and cleaning vehicles) Production (animal watering, brewing, etc.)

4. Requirements of Water The daily requirements of drinking water for adults and children are 1.5-2L and 1L per person, respectively. Domestic consumption under normal condition in an Indian city is taken as 150 LPCD (i.e. liters per capita per day) for urban areas and 55 LPCD for rural areas.

5. Hardness of Water Calcium & Magnesium cations C alcium Carbonate at concentrations <50 mg/L - Soft 50-150 mg/L - Moderately Hard 150-300 mg/L - Hard >300 mg/L - Very Hard. Removal of hardness Boiling Addition of lime Addition of sodium carbonate (soda ash) Permutit process (Base exchange process)

6. Hardness is expressed in terms of "milli-equivalents per litre (mEq/L)" One mEq/L of hardness-producing ion is equal to 50 mg CaCO3 (50ppm) in one litre of water. Drinking water should be moderately hard . Softening of water is recommended when the hardness exceeds 3 mEq/1 (150 mg per litre) Temporary hardness: Carbonates Permanent hardness: Non-carbonates

7. Water Quality Criteria & Standards The guidelines for drinking water quality recommended by WHO relate to following variables: Acceptability aspects Microbiological aspects Chemical aspects Radiological aspects.

8. Acceptability aspect

9. Microbiological aspect Bacteriological indicators used for assessing water quality are Escherichia coli or thermotolerant coliform bacteria. They shall not be detectable in any 100 mL sample in all water intended for drinking. Fecal streptococci: Recent fecal pollution of water Cl. perfringens: Remote fecal pollution of water

10. Chemical aspect

11. Other aspects Virological aspect: Disinfection with 0.5 mg/L of free chlorine residual after contact period of at least 30 minutes at a pH of 8.0 is sufficient to inactivate virus. Biological aspect: Giardia spp, Entamoeba histolytica, Balantidium coli . Dracunculus medinensis, schistosomes. Radiological aspect: S hould be within safe limits which is less than 0.1 Bq/L and less than 1.0 Bq/L for alpha and beta emitters, respectively.

12. Water treatment Household water treatment Boiling Solar water disinfection (SODIS) Ultraviolet irradiation (lamps) Chlorination Filtration Community based water treatment Coagulation Sedimentation - Storage Filtration Disinfection

13. Household water treatment Boiling WHO guidelines now recommend holding the water at boiling level for 1 minute at sea level and for 3 minutes at higher altitudes to make it safe for drinking. Ultraviolet irradiation lamps Solar water disinfection (SODIS)

14. Household water treatment Chlorination: Bleaching powder Chlorine solution High test hypochlorite (HTH) Chlorine tablets (0.5 mg for 20 L) Iodine (two drops for 2 L) Filtration: Porous rock, sand, clothes, and unglazed ceramics Nonelectrical pot and candle-type ceramic filters Electrical filters with advance membranes for nano/ultra/microfiltration & RO

15. Community level water treatment Coagulation: Aluminium & Iron salts Disinfection: Ozonisation Super chlorination Chlorination: Chlorine gas (most common), Chloramines or Perchloron. Hypochlorous acid (HOCI) & H ypochlorite ions (OCI) Of the two, Hypochlorous acid is the most effective.

16. Community level water treatment Chlorination: Free chlorine: Combination of hypochlorous acid and hypochlorite ions. More effective, Higher oxidation potential. Combined chlorine: Combination of organic nitrogen compounds and chloramines. Formed by reaction between chlorine & ammonia. Low effective, Lower oxidation potential. Chlorine demand: The amount of chlorine that is required to satisfy all the impurities and disinfect the water. Free Residual chlorine: After the breakpoint, any additional chlorine added.

17. Community level water treatment Chlorine added = Chlorine Demand + Residual Chlorine Chlorine demand Breakpoint Chlorination Residual Chlorine The minimum recommended concentration of residual chlorine is 0.5 mg/L.

18. Community level water treatment Filtration Slow sand filters (Biological) Rapid sand filters (Mechanical)

19. Slow sand filter Elements Supernatant (raw) water A bed of graded sand An under-drainage system A system of filter control valves. Filter Box

20. Supernatant water Downward flow through sand bed. Waiting period (3 to 12 hours) 1 to 1.5 m Constant

21. Filter bed Mechanical straining, Sedimentation, Adsorption, Oxidation and Bacterial action 1 metre sand bed - Filtering medium Sand grains - 0.2 to 0.3 mm Sand gravel - 20 to 30 cm Rate of filtration of water - 0.1 and 0.4 m 3 /m 2 /hour of sand bed surface.

22. Vital layer The surface of the sand bed gets covered with a slimy growth known as "Schmutzdecke" vital layer, zoogleal layer or biological layer. This layer is slimy and gelatinous and consists of threadlike algae and numerous forms of life including plankton, diatoms and bacteria. The formation of vital layer is known as "ripening" of the filter. Heart of the filter. Removes organic matter, holds back bacteria and oxidizes ammoniacal nitrogen into nitrates and helps in yielding a bacteria-free water. 2 to 3 cm .

23. Rapid sand filter G ravity type (e.g. Paterson's filter) and Pressure type (e.g. Candy's filter). Steps Coagulation Mixing Flocculation Sedimentation Filtration

24. Rapid sand filter Coagulation: Alum-5 to 40 mg or more per litre Rapid mixing Flocculation: This slow and gentle stirring results in the formation of a thick, copious, white flocculent precipitate of aluminium hydroxide. 30 minutes. Sedimentation: 2 to 6 hours.

25. Filter bed Each unit of Filter bed has a surface of about 80 to 90 m 2 (about 900 sq feet). Sand grains - 0.4-0.7 mm. Sand bed - 1 metre - Filtering medium. Gravel - 30 to 40 cm. The rate of filtration is 5-15 m 3 /m 2 /hour.