water purification- DR SHUHAIB

1. WATER
Dr shuhaib
Dept of public health dentistry

2. • SOURCES OF WATER SUPPLY
1.RAIN
2.SURFACE WATER
IMPOUNDING RESERVOIRS
RIVERS AND STREAMS
TANKS, PONDS AND LAKES
3.GROUND WATER
SHALLOW WELLS
DEEP WELLS
SPRINGS

3. WATER RELATED DISEASES
A. BIOLOGICAL WATER BORNE DISEASES
• 1.THOSE CAUSED BY THE PRESENCE OF AN
INFECTIVE AGENT
a. viral :Hepatitis A, Hepatitis.E, poliomyelitis
b. bacterial : typhoid and paratyphoid fever,bacillary
dysentery
c. protozoal : amoebiasis
d. helminthic : roundworm,threadworm
e. leptospiral : weil’s disease

4. • THOSE DUE TO THE PRESENCE OF AN AQUATIC
HOST
a. snail: schistosomiasis.
b. cyclops: guinea worm,fish tapeworm
• B. CHEMICAL
detergents solvents, cyanides, heavy metals, minerals and
organic acids, nitrogenous substance, bleaching
agents,dyes, pigments, sulfides, ammonia

5. POTABLE WATER
• Water intended for human consumption should
be both safe and wholesome
• 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

6. PURIFICATION OF WATER
1. PURIFICATION OF WATER ON A LARGE SCALE
2. PURIFICATION OF WATER ON A SMALL SCALE

7. COMPONENTS OF A TYPICAL WATER
PURIFICATION SYSTEM ARE:
1. STORAGE
2. FILTRATION
3. DISINFECTION
PURIFICATION OF WATER ON A
LARGE SCALE

8. STORAGE
RESERVE OF WATER FROM WHICH FURTHER
POLLUTION IS EXCLUDED.
NATURAL PURIFICATION
PHYSICAL
CHEMICAL
BIOLOGICAL
OPTIMUM PERIOD OF STORAGE OF RIVER WATER
IS 10-14 DAYS

9. FILTRATION
SECOND STAGE IN WATER PURIFICATION.
98-99% OF BACTERIAARE REMOVED BY
FILTRATION.
TWO TYPES OF FILTER ARE:
BIOLOGICAL OR SLOW SAND FILTERS
RAPID SAND OR MECHANICAL FILTERS

10. SLOW SAND OR BIOLOGICAL FILTERS
FIRST USED FOR WATER TREATMENT IN 1804 IN
SCOTLAND AND THEN IN LONDON.
ELEMENTS OF SLOW SAND FILTER
SUPERNATANT OR RAW WATER
BED OF GRADED SAND
AN UNDER DRAINAGE SYSTEM
A SYSTEM OF FILTER CONTROL VALVES

11. SLOW SAND FILTER

12. SUPERNATANT WATER
DEPTH VARIES FROM 1 TO 1.5 METERS.
SERVES TWO PURPOSES:
CONSTANT HEAD OF WATER TO OVERCOME THE
RESISTANCE OF FILTER BED.
PROVIDES WAITING PERIOD FOR THE RAW WATER
TO UNDERGO PARTIAL PURIFICATION .

13. SAND BED
THICKNESS --- 1 METRE
EFFECTIVE DIAMETER OF SAND GRAINS IS 0.2 TO
0.3 mm.
SAND SHOULD BE CLEAN AND FREE FROM CLAY
AND ORGANIC MATTER.
SAND BED SUPPORTED BY A LAYER OF GRADED
GRAVEL 30 TO 40 cm DEEP.

14. PURIFICATION PROCESSES LIKE
 MECHANICALSTRAINING,
 SEDIMENTATION,
 ADSORPTION,
 OXIDATION AND
 BACTERIAL ACTION.
RATE OF FILTERATION IS 0.1 TO 0.4 m3/ hour /m2
OF SAND BED SURFACE.

15. VITAL LAYER
THE SURFACE OF THE SAND BED GETS COVERED
WITH A SLIMY GROWTH KNOWN AS
SCHMUTZDECKE OR VITAL LAYER OR
ZOOGLEAL LAYER OR BIOLOGICAL LAYER.
GELATINOUS LAYER CONSISTS OF THREAD LIKE
ALGAE, PLANKTON, DIATOMS AND BACTERIA.
THE FORMATION OF VITAL LAYER IS KNOWN AS
RIPENING OF THE FILTER.

16. THICKNESS IS 2 TO 3 cm .
IT IS THE HEART OF THE SLOW SAND FILTER.
REMOVES ORGANIC MATTER , BACTERIAAND
OXIDISES AMMONICAL NITROGEN INTO
NITRATES.
YIELDS A BACTERIA FREE WATER.

17. UNDER DRAINAGE SYSTEM
CONSISTS OF POROUS OR PERFORATED PIPES.
PROVIDE AN OUTLET FOR THE FILTERED WATER.
SUPPORT THE FILTER MEDIUM ABOVE.

18. FILTER BOX
OPEN BOX , RECTANGULAR IN SHAPE.
2.5 TO 4 METERS DEEP.
BUILT WHOLLY OR PARTLY BELOW GROUND.
WALLS MADE OF BRICK, STONE OR CEMENT.
THE FILTER BOX CONSISTS FROM TOP TO BOTTOM:
 SUPERNATANT WATER 1 TO 1.5 m
 SAND BED 1.2 m
 GRAVEL SUPPORT 0.30 m
 FILTER BOTTOM 0.16 m

19. FILTER CONTROL
VALVES AND DEVICES WHICH ARE INCORPORATED
IN THE OUTLET PIPE SYSTEM.
PURPOSE IS TO MAINTAIN A CONSTANT RATE OF
FLTERATION.
VENTURIMETER :
COMPONENT OF THE REGULATION SYSTEM WHICH
MEASURES THE BED RESISTANCE OR LOSS OF HEAD.

20. ADVANTAGES OF A SLOW SAND FILTER
SIMPLE TO CONSTRUCT AND OPERATE.
COST OF CONSTRUCTION IS CHEAP.
PHYSICAL, CHEMICAL AND BACTERIOLOGICAL
QUALITY OF FILTERED WATER IS VERY HIGH.
SLOW SAND FILTERS CAN REDUCE BACTERIAL
COUNTS BY 99.9 TO 99.99 %.

21. RAPID SAND OR MECHANICAL FILTERS
 RAPID SAND FILTERS WERE FIRST INSTALLED
IN 1885 IN USA.
TYPES
GRAVITY TYPE ( eg. PATERSON’S FILTERS)
PRESSURE TYPE ( eg. CANDY’S FILTERS )

22. STEPS IN PURIFICATION OF WATER
1. COAGULATION
RAW WATER IS TREATED WITH A CHEMICAL
COAGULANT LIKE ALUM.
DOSE -- 5 TO 40 mg / LITRE.
2. RAPID MIXING
WATER IS SUBJECTED TO VIOLENT AGITATION
IN A MIXING CHAMBER TO ALLOW A QUICK
AND THOROUGH DISSEMINATION OF ALUM
THROUGHOUT THE WATER.

23. FLOW DIAGRAM OF A RAPID SAND FILTER

24. 3. FLOCCULATION
SLOW AND GENTLE STIRRING OF TREATED WATER
IN A FLOCCULATION CHAMBER FOR 30 MINUTES.
MECHANICAL TYPE OF FLOCCULATOR.
FORMATION OF A THICK, COPIOUS, WHITE FLOCC-
ULENT PRECIPATE OF ALUMINIUM HYDROXIDE

25. 4. SEDIMENTATION
COAGULATED WATER IS LED INTO THE SEDIMENT-
ATION TANKS AND DETAINED FOR 2 TO 6 HOURS.
FLOCCULENT WITH IMPURITIES AND BACTERIA
SETTLE DOWN IN THE TANK.
5. FILTERATION
PARTLY CLARIFIED WATER IS SUBJECTED TO
RAPID SAND FILTERATION

26. FILTER BEDS
SURFACE AREA IS 80 TO 90 m2.
SAND IS THE FILTERING MEDIUM.
EFFECTIVE SIZE OF SAND PARTICLES IS 0.4 - 0.7 mm.
DEPTH OF THE SAND BED IS 1 METRE.
BELOW THE SAND BED IS A LAYER OF GRADED
GRAVEL 30 TO 40 cm.
THE DEPTH OF THE WATER ON TOP OF THE SAND
BED IS 1 TO 1.5 m.
RATE OF FILTERATION IS 5 TO 15 m3 / m2 / HOUR.

27. RAPID SAND FILTER

28. FILTERATION
THE ALUM FLOC WHICH IS NOT REMOVED BY
SEDIMENTATION IS HELD BACK ON THE SAND
BED.IT FORMS A SLIMY LAYER COMPARABLE TO
ZOOGLEAL LAYER.
THIS ADSORBS BACTERIAAND EFFECTS PURI-
FICATION OF WATER.
SUSPENDED IMPURITIES AND BACTERIA CLOG
THE FILTER.
LOSS OF HEAD APPROACHES 7 TO 8 FEET, FILTER-
ATION IS STOPPED AND FILTERS ARE SUBJECT TO
WASHING --- BACK WASHING.

29. BACK WASHING
WASHING IS ACCOMPLISHED BY REVERSING THE
FLOW OF WATER THROUGH THE SAND BED. THIS
IS CALLED BACK WASHING.
PROCESS TAKES ABOUT 15 MINUTES.
COMPRESSED AIR CAN ALSO BE USED.

30. ADVANTAGES OF RAPID SAND FILTERATION
NO PRELIMINARY STORAGE IS NEEDED. CAN DEAL
WITH RAW WATER DIRECTLY.
FILTER BEDS OCCUPY LESS SPACE.
FILTERATION IS RAPID, 40 TO 50 TIMES THAT OF
A SLOW SAND FILTER.
THE WASHING OF THE FILTER IS EASY.
THERE IS MORE FLEXIBILITY IN OPERATION.

31. DISINFECTION
CRITERIA FOR A CHEMICAL OR AN AGENT TO BE
USEFUL AS A DISINFECTANT IN WATER SUPPLIES:
1. CAPABLE OF DESTROYING THE PATHOGENIC
ORGANISMS WITHIN THE CONTACT TIME AND
NOT UNDULY INFLUENCED BY THE PHYSICAL
AND CHEMICAL PROPERTIES OF WATER.
2. NOT LEAVE PRODUCTS OF REACTION WHICH
MAKE THE WATER TOXIC OR IMPART COLOR OR
MAKE IT UNPOTABLE.

32. 3. DEPENDABLE AVAILABILITY AT REASONABLE
COST.PERMIT CONVENIENT, SAFE AND ACCURATE
APPLICATION TO WATER.
4. LEAVE RESIDUAL CONCENTRATION TO DEAL
WITH SMALL POSSIBLE CONTAMINATION.

33. CHLORINATION
ONE OF THE GREATEST ADVANCES IN WATER
PURIFICATION.
SUPPLEMENT TO SAND FILTERATION.
 GERMICIDAL PROPERTIES.
OXIDISES IRON, MANGANESE AND HYDROGEN
SULPHIDE.
DESTROY TASTE AND ODOUR PRODUCING
CONSTITUENTS.
CONTROLS ALGAE AND SLIME ORGANISMS.
AIDS COAGULATION.

34. ACTION OF CHLORINE
H2O + Cl 2 ---------> HCl + HOCl
HOCl ---------> H + OCl

35. PRINCIPLES OF CHLORINATION
1. WATER TO BE CHLORINATED SHOULD BE CLEAR
AND FREE FROM TURBIDITY.
2. CHLORINE DEMAND OF THE WATER SHOULD BE
ESTIMATED.
CHLORINE DEMAND OF WATER IS THE DIFFE-
RENCE BETWEEN THE AMOUNT OF CHLORINE
ADDED TO WATER, AND THE AMOUNT OF
RESIDUAL CHLORINE REMAINING AT THE END
OF A SPECIFIC PERIOD OF CONTACT( 60 MIN)
AT A GIVEN TEMPERATURE AND PH OF THE
WATER.

36. THE POINT AT WHICH THE CHLORINE DEMAND
OF THE WATER IS MET IS CALLED THE ‘BREAK
POINT’.
3. THE CONTACT PERIOD:
FREE RESIDUAL CHLORINE FOR A PERIOD OF
ATLEAST ONE HOUR IS ESSENTIAL TO KILL
VIRUSES AND BACTERIA.
4. THE MINIMUM RECOMMENDED CONCENTRA-
TION OF FREE CHLORINE IS 0.5 mg/l FOR 1 HOUR.
5. CHLORINE DEMAND + FREE RESIDUAL CHLORINE
CONSTITUTES THE CORRECT DOSE OF CHLORINE
TO BE APPLIED.

37. METHOD OF CHLORINATION
CHLORINE IS APPLIED EITHER AS:
CHLORINE GAS
CHLORAMINE
PERCHLORON
CHLORINE GAS:
CHEAP IRRITANT TO EYES
QUICK I N ACTION POISONOUS
EASY TO APPLY SPECIAL EQUIPMENT
EFFICIENT

38. CHLORAMINES
COMPOUNDS OF CHLORINE AND AMMONIA
LESS TENDENCY TO PRODUCE CHLORINOUS TATSE
GIVE A MORE PERSISTENT TYPE OF RESIDUAL
CHLORINE.
SLOWER ACTION THAN CHLORINE GAS.
PERCHLORON
CALCIUM COMPOND WHICH CARRIES 60 TO 70 %
OF AVAILABLE CHLORINE.

39. BREAK POINT CHLORINATION
THE POINT AT WHICH THE RESIDUAL CHLORINE
APPEARS AND WHEN ALL THE COMBINED
CHLORINES HAVE BEEN COMPLETELY DESTROY-
-ED IS THE BREAK POINT.
THE CORRESPONDING DOSAGE IS THE BREAK
POINT DOSAGE.
ALSO CALLED CONTROLLED SUPERCHLORINATION
SUPERCHLORINATION
THE ADDITION OF LARGE DOSES OF CHLORINE TO
THE WATER, AND REMOVAL OF EXCESS OF
CHLORINE AFTER DISINFECTION.

40. OTHER AGENTS
OZONE GAS
ULTRAVIOLET IRRADIATON
OZONATION
OZONE IS A POWERFUL OXIDISING AGENT.
ELIMINATES UNDESIRABLE ODOUR, COLOR AND
TASTE.
HAS A STRONG VIRUCIDAL EFFECT.

41. DRAWBACK OF OZONE IS THAT IT DISAPPEARS
AND DECOMPOSES QUICKLY.
NO RESIDUAL GERMICIDAL EFFECT.
OZONE DOSAGE FOR POTABLE WATER TREATMENT
VARIES FROM 0.2 TO 1.5 mg / LITRE.
THE OLDEST WATER TREATMENT PLANT TO USE
OZONE FOR WATER TREATMENT IS IN OPERATION
IN FRANCE SINCE 1906.

42. ULTRAVILET IRRADIATION
HAS GERMICIDAL PROPERTIES .
EXPOSURE OF A FILM Of WATER , 120 mm THICK TO
UV RAYS OF WAVELENGTH 200 TO 295 nm.
ADVANTAGES
SHORT PERIOD EXPOSURE
NO TASTE AND ODOUR PRODUCED
NO HARMFUL EFFECTS IF OVEREXPOSED
DISADVANTAGES
NO RESIDUAL GERMICIDAL EFFECT
APPARATUS IS EXPENSIVE

43. THANKYOU