The document discusses safe and wholesome water. It defines safe water as free from pathogens and harmful chemicals, pleasant tasting, and usable for domestic purposes. It then discusses various water sources like rain, surface water, and ground water. It explains water purification processes at large scale like storage, filtration, and disinfection which usually involves chlorination. For small scale purification, it discusses boiling, filtration, and chemical disinfection methods.
1. Concept of safe and wholesome water,
Sanitary sources of water,
Water purification processes
2. • Healthcare to a community cannot be provided without ample
and safe drinking water
• Health which affects humans especially in developing countries is
due to lack of safe and wholesome water
• Water that is easily accessible, adequate in quantity, should be
free from contamination, safe and readily available throughout
the year
3. Safe and Wholesome Water
• Free from pathogen
• Free from harmful chemical substances
• Pleasant to the taste
• Usable for domestic purposes
4. Water requirement
For drinking purpose
• 2 Litres per capita per day (Lpcd)
Rural areas
• 40 Lpcd
Urban areas:
• Piped supply without sewerage – 70 Lpcd
• Piped supply with sewerage – 135 Lpcd
• Metropolitan and Megacities with piped water supply
and sewerage – 150-200 Lpcd
5. Uses of water
1 Domestic uses
2
Public purposes
3 Industrial purposes
4
Agricultural purpose
5 Power production
6
Carrying away waste
7. Rain
• Purest water in nature
• Clear, bright & sparkling
• Contain only traces of dissolved solids
• Tends to become impure as it passes through the
atmosphere
8. Impounding reservoirs
• Artificial lakes and dams
• The area draining into the reservoir is called
“Catchment area”
• Usually furnish a fairly good quality of water
• Impurities from human habitations and animal
grazing (from catchment area)
9. Rivers
• Unfit for drinking without treating
• Turbid during rainy season
• High amount of impurities
• Certain amount of self-purification occurs
10. Tanks
• Large excavations in which surface water is
stored
• Subjected to unlimited possibilities of
contamination
• Sanitary quality of water can be improved
11. Sea water
• Though plentiful, it has many limitations
• It contains 3.5 per cent of salts in solution
• Desalting and demineralization process involves
heavy expenditure
• It is adopted in places where sea water is the
only source available
12. Ground water
• Cheapest and most practical means of providing
water to small communities
• Superior to surface water, because the ground
itself provides an effective filtering medium
• Usual ground water sources are wells and
springs
13. Advantages Disadvantages
• It is likely to be free from pathogenic
agents
• It usually requires no treatment
• The supply is likely to be certain even
during dry season
• It is less subject to contamination
than surface water
• It is high in mineral content
• It requires pumping or some
arrangement to lift the water
15. Shallow well Deep well
Definitions
Taps water from above
the first impervious
layer
Taps water from below
the first impervious
layer
Chemical quality Moderately hard water Much harder
Bacteriological quality
Often grossly
contaminated
Pure water
Yield Dry in summer Constant supply
16.
17. Sanitary Wells
A sanitary well is one which is properly
located, well-constructed and protected
against contamination with a view to
yield a supply of safe water
18. LOCATION
• Not less than 15 m (50 feet) from likely sources of contamination
• At higher elevation with respect to possible source of contamination
• No more than 100 m (100 yards) from house
LINING
• Built of bricks or stones set in cement
• Up to a depth of at least 6 m (20 feet)
• 60-90 cm (2-3 feet) above ground level
19. PARAPET WALL
• Up to a height of at least 70-75 cms (28 inches) above the ground
PLATFORM
• Cement-concrete platform round the well
• Extending at least 1 m (3 feet) in all directions
• Should have gentle slope outwards towards a drain
20. DRAIN
• Pucca drain to carry off spilled water to a public drain or a soakage
pit constructed beyond the “cone of filtration” (area of drainage) of
the well
COVERING
• Top of the well should be closed by a cement concrete cover
21. HAND-PUMP
• Should be equipped with a hand-pump for lifting the water in a
sanitary manner
• There should be efficient maintenance service
CONSUMER RESPONSIBILITY
• Consumers should observe certain basic precautions at the
individual and family level
22. QUALITY
• The physical, chemical and bacteriological quality of water should
conform to the acceptable standards of quality of safe and
wholesome water
23.
24. Tube Wells
• Tube well consists of a pipe (usually
galvanized iron) sunk into the water-
bearing stratum and fitted with a
strainer at the bottom, and a hand-
pump at the top
• A water-tight concrete platform with
a drain all round should be provided
25. Springs
• These are ground water which comes to
the surface and flows freely under
natural pressure
• Two types: Shallow & Deep springs
• Springs are exposed to contamination
• Well built protective structures are
necessary to safeguard water quality
28. STORAGE
• Physical : about 90% of suspended
impurities settle down in 24 hours
• Chemical : content of free ammonia is
reduced, rise in nitrates occurs
• Biological : total bacterial count drops by
as much as 90% in the first 5-7 days
30. Slow sand (or, biological) filters
Elements of slow sand filters
(1) supernatant (raw) water
(2) a bed of graded sand
(3) an under-drainage system
(4) a system of filter control valves
33. River water intake Pre-settling tank Aerator
Flash mixer
Clariflocculator
Filter
Water reservoir
Fig: Flowchart showing mechanical filtration at Water Plant in Imphal
Alum
Chlorine
35. DISINFECTION
• Last step in purification of water
• It is supplement, and not substitute to
sand filtration
• Destroys most of the pathogenic bacteria
• Chlorination is the most common
method used
36. Chlorination
(1)Water to be chlorinated should be
clear and free from turbidity
(2)“Chlorine demand” of the water
should be estimated
(3)Chlorine is added till “break point”
(4)Contact period of at least 1 hour is
essential
TYPES OF CHLORINE
• Chlorine Gas
• Chloramines
• Bleaching Powder
• High Test Hypochlorite
37. Chlorine demand
The difference between the amount of chlorine added to the water,
and the amount of residual chlorine remaining at the end of a specific
period of contact (usually 60 minutes) at a given temperature and pH of
the water
Break point
The point at which the chlorine demand of the water is met
38. Free Residual Chlorine
• The minimum concentration of free residual chlorine in drinking
purpose should be 0.5 mg/L at the consumer level
• It should be 2mg/L or 2ppm at production level (water works) after
1 hour contact period
• The purpose of providing 2ppm at water works level is to provide a
margin of safety against further contamination of water during
storage and distribution
39. Orthotoluidine (OT) test
Add 0.1 ml (2-3 drops) of orthotoluidine
reagent to 1 ml of water
Yellow colour within 10-15 seconds
indicates presence of free chlorine
Yellow colour appears after 15-20
minute indicates the presence of
free and combined chlorine
40. Orthotoluidine Arsenite (OTA) Test
• Modification of the OT test
• To determine the free and combined chlorine residuals
separately
• Errors caused by the presence of interfering substances such
as nitrites, iron and manganese are overcome
44. Boiling
• Water must be brought to a “rolling boil”
for 10 to 20 minutes
• Kills all bacteria, spores, cysts and ova
• Offers no “residual protection” against
subsequent microbial contamination
• Should be boiled preferably in the same
container in which it is to be stored
45. Filtration
• Water can be purified on a small scale by
filtering
• Filter candles usually remove bacteriae
found in drinking water
• They should be cleaned by scrubbing
with a hard brush under running water
and boiled at least once a week
51. Ultraviolet radiation
• Disinfection involves the exposure of a
film of water to ultraviolet radiation
• Applications arc limited to individual or
institutional systems
• Exposure is for short period, no foreign
matter introduced and no taste and
odour produced
52. Reverse osmosis
Used to make water both
chemically & microbiologically
potable by reducing the total
dissolved solids, hardness,
heavy metals and disease
causing bacteria, virus,
protozoa and cysts
53. DISINFECTION OF WELLS
• Wells are the main source of water
supply in the rural areas
• The need often arises to disinfect them
• The most effective and cheapest method
of disinfecting wells is by bleaching
powder
54. Steps in well disinfection
1. Find volume of water in a well
a) Measure the depth of water column ... (h) metre
b) Measure the diameter of well ... (d) metre
c) Substitute h and d in : Volume (litres) =
3.14×𝑑2×ℎ
4
d) One cubic metre = 1,000 litres of water
55. 2. Find the amount of bleaching powder required for disinfection
a) Estimate the chlorine demand of the well water by Horrock's
Apparatus
b) Calculate the amount of bleaching powder required
c) Roughly, 2.5 grams of good quality bleaching powder would be
required to disinfect 1,000 litres of water
d) This will give an approximate dose of 0.7 mg of applied chlorine
per litre of water.
56. 3. Dissolve bleaching powder in water
a) The bleaching powder required for disinfecting the well is placed in
a bucket and made into a thin paste
b) More water is added till the bucket is nearly three-fourths full
c) The contents are stirred well, and allowed to sediment for 5 to 10
minutes
d) The supernatant solution which is chlorine solution, is transferred
to another bucket, and the chalk or lime is discarded
57. 4. Delivery of chlorine solution into the well
a) Lower bucket containing chlorine solution below the water surface
b) Agitated well water by moving the bucket violently both vertically
and laterally
5. Contact period
A contact period of one hour is allowed before water is drawn for use
58. Horrock’s apparatus
1. 6 white cups (200 ml capacity each)
2. One black cup with a circular mark on the
inside
3. 2 metal spoons
4. 7 glass stirring rods
5. One special pipette
6. Two droppers
7. Starch-iodide indicator solution
8. Instruction folder
59. Procedure
1. Take one level spoonful (2 g) of bleaching powder in the black cup and
make it into a thin paste with a little water
Add more water to the paste and make up the volume upto the
circular mark with vigorous stirring
Allow to settle
This is the stock solution
2. Fill the 6 white cups with water to be tested
60. 3. With the special pipette provided add
1 drop of the stock solution to the 1st cup
2 drops to the 2nd cup
3 drops to the 3rd cup, and so on
4. Stir the water in each cup using a separate rod
5. Wait for half an hour for the action of chlorine
61. 6. Add 3 drops of starch-iodide indicator to each of the white cups and stir
again. Development of blue colour indicates the presence of free
residual chlorine
7. Note the first cup which shows distinct blue colour
Supposing the 3rd cup shows blue colour, then 3 level spoonfuls or 6
grams of bleaching powder would be required to disinfect 455 litres of
water
62. Conclusion
Much of the ill-health which affects humanity can be traced to lack of
safe and wholesome water supply
Uses of water in a community are many, and the requirement in
quantity and quality are varied
There are 3 main sources of water: Rain, Surface water & Ground water
Water can be purified at Large and Small scale
Purification of water mainly involves Filtration and Disinfection
