Water resources managt

1. Hari Prasad Kafle
Assistant Professor (Public Health)
School of Health and Allied Sciences
Pokhara University.

4.  Inorganic compound made up of 2 part of
hydrogen and one part of oxygen.
 Essential component for vitality animal and
plant life.
 Alma Ata Declarations on PHC1978: Water as
basic element of Primary Health Care (An
adequate supply of safe drinking water and
basic sanitation).

5.  Free from pathogenic agents
 Free from harmful chemical
substances
 Pleasant to taste, i.e. free
from color and order, and
 Useable for domestic propose

6. For drinking purpose: 2 liter/person/day

7. Domestic purpose: 150-200 liter/person/day

8. 1. Domestic uses;
2. Public purpose: cleaning
streets; fire protection, etc.
3. Industrial purpose;
4. Agricultural purpose;
5. Hydropower production;
6. Other uses: fishing, tourism,
swimming pool, ornamental
ponds, transportation etc.

9.  Rainwater;
 Surface water
◦ Impounding reservoir
◦ River and streams
◦ Tanks, Ponds and lakes
 Ground water
◦ Sallow well
◦ Deep well
◦ Spring

10.  Prime source of all water
 Purest water in the nature
 Physically clear, bright and sparkling
 Chemically very soft
 Corrosive action on pipes due to softness
 Bacteriological free from pathogenic organism
 Contains atmospheric impurities while raining:
acid rain

11.  Originates from rain water
 Main source of water supply
 Examples: river, tanks, lake, sea water
 Types: 4 types
◦ Impounding reservoir
◦ River and streams
◦ Tanks, Ponds and lakes
◦ Sea water
 High chances of contamination
 Generally no useable without treatment

12.  Cheapest and more practical means providing
water for small communities
 Free from pathogenic organism
 Usually requires no treatment
 Supply even dry seasons
 High mineral content e.g. Ca, Mg etc.
 Requires pumping
 Ground water includes
◦ Sallow well
◦ Deep well
◦ Spring

13. Particulars Shallow well Deep well
Definition Taps water from above
the first impervious
layer
Taps water from
below the first
impervious layer
Chemical
quality
Moderately hard Much hard
Bacteriologi
cal quality
Often grossly
contaminated
Tapes purer water
Yields Usually goes dry in
summer
Provides a source
of constant
supply

15. Location 1990 2000 2005 2010 2015*
Drinking
Water
Urban (%) 90 86 93 94 95
Rural (%) 43 71 79 78 72
Total 46 73 81 80 73
*Target MDG
Source: Nepal Millennium Development Goals; Progress Report 2010.

16. Developmen
t region
Piped
water
Hand
pump
Well Spring
water
Other
FDR 30.7 44 3.5 19.7 1.9
MWR 44.3 28.3 4.1 21.7 1.6
WR 59.8 27. 0.5 10.2 2.2
CR 45.4 39.4 5.4 6.5 3.4
ER 37.7 53.1 3.2 3.1 3
Nepal 45 39.1 3.6 9.6 2.7

17. Geographic
region
Piped
water
Hand
pump
Well Spring
water
Other
Terai 16.1 78.2 4.3 0.9 0.5
Hill 71 3.3 3.3 17.5 4.9
Mountain 77.3 0.3 0 18.9 3.5
Urban 62.2 28.2 4.3 3.1 2.2
Rural 45.5 41.3 3.4 11 2.8
Nepal 45 39.1 3.6 9.6 2.7

18. Year Unit Water Supply Leakage (%)
1993/94 Th. l/day 64684 -
1994/95 Th. l/day 62379 -
1995/96 Th. l/day 63447 -
1996/97 Th. l/day 40150 -
1997/98 Th. l/day 32115 -
1998/99 Th. l/day 27011 -
1999/00 Th. l/day 31271 38
2000/01 Th. l/day 26644 37
2001/02 Th. l/day 9876 37
2002/03 Th. l/day 10552 37
2003/04 Th. l/day 11550 36
2004/05 Th. l/day 9580 37
2005/06 Th. l/day 26300 38
2006/07 Th. l/day 33500 37
2007/08 Th. l/day 230450 35

19.  Sewage,
 Industrial and
trade pollutants,
 Agricultural
pollutants,
 Physical pollutants
 Radioactive
substances.

20.  Factories, power plants, sewage treatment
plants, latrines that are classified as point
sources, as they discharge pollution from
specific locations.
 Non-point sources of water pollution are
scattered or diffuse, having no specific location
for discharge and include runoff from farm
fields and feedlots, construction sites, roads,
streets and parking lots.

21. Pollutant Main source Effects Possible control
Organic
oxygen
demanding
waste
Human sewage,
animal wastes,
decaying plant life,
industrial waste
Overload depletes
dissolved oxygen in
water: animal life
destroyed or migrates
away: plant life
destroyed
Provide secondary
and tertiary waste
water treatment;
minimize agricultural
runoff
Plant
nutrients
Agricultural
runoff, detergents
industrial wastes
inadequate
waste water
treatment
Algal blooms and
excessive aquatic plant
growth upset
ecological balances:
eutrophication
Agricultural runoff
too
widespread, diffuse
for adequate

22. Pollutant Main source Effects Possible control
Pathogenic
bacteria &
virus
presence of
sewage and animal
wastes in water
Outbreaks of such
diseases
as typhoid infectious
hepatitis
Provide secondary
and tertiary
wastewater
treatment; minimize
agricultural runoff
Inorganic
chemicals
Mining
manufacturing
irrigation, oil fields
Alter acidity, basicity,
or
salinity: also render
water
toxic
Disinfect during
waste-water
treatment; stop
pollutants at source

23. Pollutant Main source Effects Possible control
Synthetic
organic
chemicals
(plastic,
pesticides)
Agricultural
manufacturing, and
consumer uses
Many are not
biodegradable;
chemical interactions
in environment are
poorly understood
many poisonous
Use of biodegradable
materials; prevent
entry into water
supply at source
Sediments Natural erosion,
poor soil
conservation
practices in
agriculture, mining
construction
Fill in waterways,
reduce
fish populations
Put soil conservation
practices to use

24. Pollutant Main source Effects Possible control
Fossil fuels
(oils
particularly)
Machinery,
automobile wastes;
pipeline breaks,
offshore blowout
and seepage,
supertanker
accidents, spills,
and wrecks; heating
transportation,
industry;
agriculture
Vary with location,
duration, and type of
fossil fuel; potential
disruption of
ecosystems; economic,
recreational, and
aesthetic damage to
coasts
Strictly regulate oil
drilling,
transportation,
storage; collect and
reprocess engine oil
and grease; develop
means to contain
spills

25. A. Biological: water borne
disease
B. Chemical: organic acids,
Detergents, heavy metal
show long term effect.
C. Water associated disease:
Malaria, JE, filaria, dental
carries, CHD, conjunctivitis,
trachoma etc.

26.  Viral: Viral hepatitis A, Hepatitis E, Poliomyelitis,
rotavirus diarrhoea etc.
 Bacterial: typhoid & paratyphoid fever, bacillary
dysentery, Cholera, Esch. Diarrhoea etc.
 Protozoal: amoebiasis, giardiasis.
 Helminthic: round worm, thread worm, hydiatid
disease.
 Snail: schistosomiasis.
 Cyclops: guinea worm, fish tape worm.

27. Oh! how big; Could we digest it?
Let’s try!

28. Hari Prasad Kafle
Assistant Professor (Public Health)
School of Health and Allied Sciences
Pokhara University.

29. The guideline for drinking water quality
recommended by WHO (1993 and 1996) relate
to following variables:
1. Acceptability aspects
2. Microbiological aspects
3. Chemical aspect
4. Radiological aspects

30. A. Physical parameters
1.Turbidity: < 5NTU (Nephelometric Turbidity
Unit)
2.Colour: free from colour; upto 15 TCU (True
Colour Unit)
3.Taste and odour: pleasant to taste and no odour
4.Temperature: cool water is more palatable.

31.  Chloride: upto
200mg/liter
 Calcium: 100-300mg/liter
 Ammonia: <0.2mg/liter
 Hydrogen sulphide: 0.05-
0.1mg/liter
 Iron: 0.3mg/liter
 Sodium: 200mg/liter
 Sulphate: <250mg/liter
 Zinc: 0.3mg/liter
 Manganese: <0.1mg/liter
 Cupper: <1mg/liter
 Aluminum: 0.2mg/liter
 PH value: 6.5-8.5
 Dissolved oxygen: no
guideline
 Total dissolved solids:
<100mg/liter
B. Inorganic constituents

32. 1. Bacteriological indicator
a. Coliform organism
b. Faecal streptococci
c. Cl. Perfringens
2. Virological aspects
3. Biological aspects
a. Protozoa
b. Helminthes
c. Free living organism

33. a. Coliform organism: Several region for choosing coliform
indicators of faecal pollution are:
i. Easy to culture; even single E. coli can be culturable
in 100 ml of water.
ii. They are foreign to the water and generally not
present to water.
iii. They are present in greater number (normal human
can excrete 200-400 billion E. coli)
iv. They resist natural purification
v. They live longer than other pathogens

34. b. Faecal streptococci: It is the confirmatory test
for faecal contamination. Some times (very
rarely) E. coli doesn't present in water but if
present streptococci than there is 100% faecal
contamination.
c. Clostridia: the spores of clostridia are highly
resistance against the disinfection. If only one
spore of clostridia is present in water; it shows
faecal contamination taken place in remote
time.

35.  Drinking water should be free from any virus
infectious to man. At the level of 0.5% FRC all
pathogenic virus will be destroyed including
hepatitis A. when bleaching powder mix with
2.5 gram mix with 1000ml of water then Free
Residual Chlorine (FRC) will be 0.7%/liter in
water.

36. a. Protozoa: Entomoba Histolytica, Giardia
Lambia both should not present in drinking
water and both slow and rapid sand filter are
effective In remaining protozoa.
b. Helminthes: Round worm, Flat worm etc.
Even a single egg/larva can produce disease in
man; should not in water. Guinea worm and
schistosomiasis is hazard of unpiped water can
be protect from source protection.

37. c. Free living organism: free living organism
that occurs in water supply include fungi,
algae etc. which interfere colour, odour, taste,
turbidity etc.

38. A. Inorganic chemicals
B. Organic constituents

39.  Arsenic: 0.01mg/liter
 Cadmium: 0.003mcg/liter
 Chromium: 0.05mg/liter
 Cyanide: 0.07mg/liter
 Fluoride: 1.5mg/liter
 Lead: 0.01mg/liter
 Mercury: 0.001mg/liter
 Nitrate (NO3): 50mg/liter
 Nitrite (NO2): 3mg/liter
 Selenium: 0.01mg/liter

40. Organic constituents Upper limit of
concentration
(Mcg/L)
Chlorinated alkanes
Carbon tetrachloride 2
Dichloromethane 20
Chlorinated ethane
Vinyl chloride 55
1.1-dichloroethene 30
1.2-dichloroethene 50

41. Organic constituents Upper limit of
concentration
(Mcg/L)
Aromatic hydrocarbon
Benzene 10
Toluene 700
Xylems 500
Ethyl Benzene 300
Styrene 20
Benzolalpyrene 0.7

42. Organic constituents Upper limit of
concentration(Mcg/L)
Aldrin/dieldrin 0.03
Chloride 0.2
DDT 2
Hepatochlor epoxide 0.03
Hexachlorobenzene 1
Lindane 2
Methoxychlor 20
Pentachlorophenol 9

43.  Gross α activity = 0.1 Bq/L (Becquerel)
 Gross β activity = 1.0 Bq/L

44. Thank you!

45. Hari Prasad Kafle
Assistant Professor (Public Health)
School of Health and Allied Sciences
Pokhara University.

46. Don’t be puzzled by problems, what ever
they may be.
Always face them as if they are examinations
you have to pass.

47. The activities that ideally should be included in
the surveillance function are:
1. Approval of new sources (including private-
owned supplies)
2. Watershed protection

48. 3. Approval of the construction and operating
procedures of waterworks, including:
 Disinfection of the plant and of the distribution
system after repair or interruption of supply.
 Periodic flushing programs and cleaning of
water storage facilities.
 Certification of operators,
 regulation of chemical substances used in
water treatment
 cross connection control, back-flow prevention
and leak detection control;

49. 4. Sanitary survey;
5. Monitoring programs, including provision for
central and regional analytical laboratory
services;
6. Development of codes of practice for well
construction, pump installation and plumbing
7. Inspection quality control in bottled-water
and ice manufacturing operations.

50. 1. Sanitary survey:
◦ On-the-spot inspection
◦ Evaluation by a qualified person.
◦ Purpose: detection and correction of faults
and deficiencies.

51. 2. Sampling:
◦ Carried out by competent and trained personnel.
◦ Sample for physical and chemical examination:
◦ Clean glass stoppered bottles (known as
“Winchester Quart bottles”)
◦ Capacity of bottle: less than 2 liters.
◦ Sample for biological examination:
◦ Collected in clean sterilized bottles made of neutral
glass.
◦ Capacity: 200-250 ml

52. 3. Bacteriological Surveillance:
a. Presumptive Coliform Test:
i. Multiple tube method
 Tube-Mc Conkey’s Lactose Bile Salt Broth with
bromcresol purple
 Incubated for 48 hours.
 Most probable number (MPN) is obtained from the
number of tubes showing acid and gas in 100ml water.
ii.Membrane filtration technique
 Filtered through a membrane specially made of cellulose
ester.
 Obtained result within 20 hours.

53. 3. Bacteriological Surveillance:
a. The detection of faecal streptococci and cl.
perfringens
b. Colony count
 Count on nutrient agar (yeast extract agar)
at 37 deg C and 22 deg C.

54. 4. Biological examination
 Microscopic organism: algae, fungi, yeast,
protozoa, rotifers, crustacean, minute worms,
etc.
5. Chemical surveillance
 Basic Test: PH, colour, turbidity, chlorides,
ammonia, residual chlorine
 Include analysis for toxic metal, pesticide,
persistent organic chemical and radioactivity.

55. 55

57. No matter how handsome
(beautiful) you may be,
you will be judged by your
words and actions.
Always express sweet &
sound words and positive
action & efforts to sustain
your achievements.

59.  Water purification is defined as the process of
removing all those substances, whether
biological, chemical or physical, which are
potentially dangerous or undesirable in water
supply for human and domestic use.

60. 1.To remove pathogenic organisms &
consequently to prevent waterborne disease.
2.To remove substance which impart color, taste or
odor to the water.
3.To remove excess or undesirable chemicals or
minerals from the water.
4.To regulate essential elements or chemicals that
may be in excess or lacking in a certain water
supply.
5.To remove excess/undesirable dissolved gasses.

61.  In order to achieve these objectives, water
treatment procedures may involve a simple
physical process such as sedimentation, or
complex physio-chemical and biological
processes, depending upon the undesirable
elements or substance present in the raw water.

62.  Preliminary planning of water treatment plant
work should include a comprehensive study of
the catchments area in terms of:
1. Size, topography, population division and
surface geology
2. Source of pollution
3. Sewage treatment facilities
4. Raw water characteristics including physical,
radiological, chemical, bacteriological and
biological characteristics

63. 5. Rainfall and run-off data
6. Evaporation rate
7. Anticipated water supply requirement,
(minimum, maximum and average); and
8. Other items of importance in providing a safe
water supply, adequate in amount for the
community in question.

64.  Purification of water in large scale
◦ Rapid sand filter
◦ Slow sand filter
 Purification of water in small scale
◦ Boiling
◦ Chemical disinfection
◦ Filtration
◦ Well disinfection

65.  The component of water purification system
comprise one or more of the following
measures:
i. Storage
ii. Filtration
iii.Disinfection

66.  As a result of storage, considerable amount of
purification takes place.
 Physical: 90% suspended particles settle
down in 24 hours by gravity.
 Chemical: aerobic bacteria oxidize the
organic matter present in the water with aid of
dissolved oxygen.
 Biologically: bacterial count drops by 90% by
storage of water for 5-7 days.

67.  Second stage of purification
 98-99% of bacteria are removed by filtration.
 Two types of filtration procedure are used for
large scale water purification.
 Rapid sand filter “Mechanical filter”
 Slow sand filter “Biological filter”

68.  The oldest type, this type of filter has been use
traditionally and has been effective in the past.
 The rate of filtration very low than rapid sand
filter.
 Some of these filters are still in use in some
parts of the Far East, Europe, and North
America.

69.  It is very well suited to rural areas, because it
does not require skilled workers to construct or
maintain, and the costs of operation and
maintenance are reasonable.

70.  In this system, the process of filtration is a
combination of physical straining, (e.g.
sedimentation and biological activities), such
as the growth of micro-organisms which takes
place in the topmost layer of the sand grains
soon after filter is in operation.
 This microbial growth in the sand grain forms
a sticky gelatinous coat in the top layers of the
filter, and is called schmutzdecke, a German
term meaning "cover of filth".

72. a.Raw water
b.A bed of graded sand
c.An under drainage system
d.A system of filter control valve.

73.  The raw water to be filtered should be as clean
as possible, and turbidity should be less than
50 mg/l.
 The depth of raw water is about 1-1.5 meter.
 The raw water is evenly distributed over the
graded sand to a depth from 90 cm to 1.20
meters (36 inches to 48 inches).

74.  The depth of the filter sand is one of the most
important determinants of the efficiency of
flirtation.
 The effective diameter of sand is about 2-
3mm.
 The graded sand is laid on the top of the
graded gravel to a minimum depth of 60 cm
(2ft), optimum 90 cm (3ft), and a maximum
depth of 1.20 meters (4ft).

75.  Water percolates through a sand bed very
slowly taking time 2 hours or more to pass
taking number of purification process:
mechanical straining, sedimentation,
absorption, oxidation and bacterial action.
 The designated rate of filtration is about 0.1-
0.4m3/m2/hour.

76.  Crushed round gravel of fixed sizes, varying
from about 5 cm to 1.5 mm is laid around and
over the under drains, the largest size at the
bottom and the smallest at the top.
 The depth of the graded gravel should be at
least 30 cm (12 inches), and preferably 45 cm
(18 inches).

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Filter sand
Course sand
Finegravel
Course gravel

78.  Perforated pipes, or drainpipes with open
joints, with side joints (laterals) connected to
the main drain, are laid at the bottom of the
filter bed or tank to collect filtered water.

79.  Equipped with certain valve and devices which
are incorporated in the outlet pipe system.
 The purpose is to control the rate of filtration.
 An important component is a ‘Venturi meter’
which measure the bed resistance or ‘loss of
head’.

80.  The rate of filtration decreases gradually due
to clogging, it indicates the necessity for
cleaning, filtration is stopped, and the topmost
layer of the sand is removed by careful
scraping.
 Each scraping usually removes from 5 cm to
10 cm depth of sand.

81.  The sand that has been scraped off is stored
and washed several times.
 The cleaned sand is then replaced over the bed
of the filter, to maintain the minimum depth.
 The cleaning interval varies from about three
weeks to several months depending on the
quality of the raw mater to be filtered.

82.  First installed in USA in 1885.
 Useful for industrialized countries having
metro and mega cities.
 Supply large amount of water for populations.
 Occupies very small space for plant
installation.

83. Mixing
Chamber
Flocculation
Chamber
Sedimentation
Tank Filter
Clean
water
storage
Alum
Chlorine
Consumption

85. 1. Screening
2. Coagulation
3. Rapid mixing
4. Flocculation
5. Sedimentation
6. Filtration
7. Chlorination
8. Supply

86.  To protect the main units of a treatment plant and
to aid in their efficient operation, it is necessary
to remove any large floating and suspended solids
that are often present in the inflow.
 These materials include leaves, twigs, paper, rags
and other debris that could obstruct flow through
a plant or damage equipment in the plant.

87.  The raw water is first treated with a chemical
coagulants such as alum (Aluminum Sulphate)
in the varying dose of 5-40mg/liter depending
up on the colour, turbidity, temperature and PH
value of water.

88.  The treated water is then subjected to violent
agitation in a mixing chamber for a few
minutes.
 This allows a quick and through dissemination
of alum through out the bulk of water.

89.  Intense mixing of
coagulant and other
chemicals with the
water.
 Generally performed
with mechanical mixers
Chemical Coagulant

90.  Flocculation involves a slow and gentle stirring
of the treated water in a flocculation chamber
for about 30 minutes.
 This result in formation of thick, copious, white
flocculent precipitate of aluminum hydroxide.

92. Water coming from
rapid mix.
Water goes to sedimentation
basin.

93.  The coagulated water is now led into
sedimentation tanks where it is detained for
periods varying from 2-6 hours when the settle
down in the tank.
 At least 95% of the flocculent precipitate
needs to be removed before the water is
admitted into the rapid sand filter.

94. Water coming from
flocculation basin.
Water goes to
filter.
Floc (sludge) collected
in hopperSludge to solids
treatment

96.  The partly clarified water is then subjected to
rapid sand filter.
 Filter is a process where the suspended matter
is separated or purified by passing it through a
minute porous material or medium.
 This medium may be sand, diatomaceous
earth, or a finely woven fabric.

97. 1.To produce clear sparkling water (reduce
turbidity)
2.To reduce number of micro-organisms
3.To minimize the contaminants which cause
undesirable taste and odor
4.To remove any suspended solid in water.

98.  Each unit of filter bed has a surface of about 80-
90 m sq (about 900 sq feet).
 Sand bed: Sand is the filtering medium. The
effective size of the sand particles is about 0.4-
0.7mm. The depth of the sand bed is usually
about 1 meter.
 Gravel bed: Below the sand bed is a layer of
graded gravel of 30-40 cm. The gravel supports
the sand bed and permits the filtrated water to
move towards the under drain.

99.  The depth of water on the top of the water is
about 1-1.5 meter.
 The rate of filtration is 5-15cubic m3/m2/hour.
 Filtration removes “alum-floc” not removed
by sedimentation.

100. Water coming from
sedimentation
basin.
Anthracite
Sand
Gravel (support
media)
Water going to disinfection

101.  It is cleaned by means of its back-washing
system.
 In this filter, the sand layer gets clogged
quickly because of the high rate of filtration
and deposition of flocs among the sand grains.
 The filter is washed at intervals varying
between 20 hours and 5 days, depending on
the degree of turbidity of the raw water.

102.  Washing of the filter sand is achieved by
forcing clean water up through the sand, by
reversing the flow of water pressure.
 The forced upward flow agitates the sand
layers and washes away the clogging materials
to a drain system, which totally gets rid of the
dirt into a final disposal drain.
 The washing process is normally
accomplished in five to fifteen minutes.

103. 10
3

105. Particular Rapid sand filter Slow sand filter
Space Occupies very little
space
Occupies large
space
Rate of
filtration
200 mgad 2-3mgad
Effective
size of sand
0.4-0.7mm 0.2-0.3 mm
Preliminary
treatment
Chemical coagulation
and sedimentation
Plane
sedimentation
Washing By back washing By scraping sand
bed

106. Particular Rapid sand
filter
Slow sand
filter
Washing By back
washing
By scraping
sand bed
Operation Highly skilled Less skilled
Loss of head allowed 6-8 feet
(2.25m)
4 feet (1.5m)
Removal of turbidity Good Good
Removal of colour Good Fair
Removal of bacterial 89-99% 99.9-99.99%

107.  Simple to construct and operate
 The cost of construction is cheaper than rapid
sand filter
 physical, chemical and bacteriological quality
is very high.
 Reduced total bacterial counts by 99.9-99.99%
and E coli counts by 99-999.9%.

108.  An outdated method
 Occupies large space
 Very low rate of filtration
 Not suitable for mega and metro cities

109.  Deal directly with raw water
 No preliminary storage of water is required
 Filter beds occupies less space
 Rapid filtration rate (40-50 times grater than
slow sand filter)
 Flexibility in operation.
 Suitable for large populations.

110.  Required highly skilled manpower
 High maintenance cost
 Required frequent cleaning/washing

111.  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.

112.  Location
 Lining
 Parapet
 Plate form
 Drain
 Covering
 Hand pump
 Consumers responsibility
 Quality

113.  At least 50 feet from source of contamination
 Appropriate distance from home ( not more
than 100 meter)

114.  Cemented ring or made up of stone or break
lining up to the depth of at least 20 feet.
 2-3 feet above the ground level

115.  28 inches above the ground level

116.  Cement concrete plat form at least 1 m (3
feet) in all directions.
 Sloping towards the drain

117.  Cemented drain around the platform to drain
waste water

118.  The top of the well should be covered by a
cement concrete cover to protect against
contamination.

119.  The well should be equipped with hand pump
for lifting the water in sanitary manner.
 Electronic device can be applied for lifting the
water.

120.  Protection and maintenance
 Time to time disinfection

121.  Physical, chemical and bacteriological quality
should be measured in time to time by taking
sample.

124. Chemical or agent used for water disinfection
meet following criteria:
1.Capable for destroying pathogenic organism
2.Should not leave toxic product after chemical
reaction
3.Reasonable price, simple to use, safe and easy
availability
4.Leaving residual concentration to deal with
possible recontamination.
5.Rapid, practical & simple analytical technique.

125.  Chlorine formula
 Ozonization
 Ultraviolet radiation

126.  Most commonly used method for large and
small scale purification of water
 It is supplement not a substitute of filtration.
 Chlorine kills pathogenic bacteria but it has no
effect on spores and certain virus like polio
and hepatitis virus.

127.  Chlorine kills pathogenic bacteria but it has no
effect on spores and certain virus like polio
and hepatitis virus.
 It also oxidizes iron, manganese and hydrogen
sulphide.
 It also destroys some taste and odour
producing constituents.
 It controls algae and slime organisms and aids
coagulation.

128.  When chlorine is added to water, there is
formation of hydrochloric and hypochlorous
acids.
 The hydrochloric acid is neutralized by the
alkalinity of water.
 The hypochlorous acid ionizes to form
hydrogen ions and hypochlorite ions.

129. H2O + CL2 HCL + HOCL
HOCL H+ + OCL-
 The disinfecting action of chlorine is mainly
due to the hypochlorous acid and to small
extends due to hypochlorite ion.
 Chlorine acts best when the PH value of water
is about 7.

130. 1.Water to be chlorinated should be clear and free
from turbidity.
2.Chlorine demand should be estimated exactly.
3.Contact period should be at least one hour to
kill bacteria and viruses.
4.Minimum recommended free residual chlorine
should be 0.5/liter.
5.Chlorine dose should include chlorine demand
and chlorine amount to produce 0.5mg/L FRC.

131.  Chlorine Demand: The amount of chlorine that
is needed to destroy bacteria and to oxidize all
the organic matters and amonical substances
present in the water.
 Chlorine Dose: the total amount of chlorine
that is needed to meet the chlorine demand and
to produce 0.5mg/liter free residual chlorine.

132.  Break point: The point at which chlorine
demand of water is meet is known as break point.
If further chlorine is added then free residual
chlorine begins to start in water.
 Contact period: The period from a point when
free residual chlorine starts appearing in water to
the period from which can be consumed is known
as contact period. It should be at least hour.

133.  Free Residual Chlorine: the concentration of
free chlorine in water after 1 hour of contact
period is known as free residual chlorine. The
minimum recommended FRC is 0.5mg/L.

134. Chlorine Demand
Chlorine dose
Contact Period
Break Point FRC
0.5 mg/L
ConcentrationofChlorine
Combined
chlorine
Mono: diachloramine 2:1

135.  NH3+Cl2= NH2Cl (Monochloramine)
 NH2Cl+CL2= NHCL2 (Dichloramine)
 NH2Cl+NHCL2= N2O (nitrous oxide)

136.  Ozone is relatively unstable gas.
 Powerful oxidizing agent
 Eliminates undesirable colour, odour, taste and
removal of all chlorine from water.
 Strong virucidal effect
 > 1000 cities practicing
 Appropriate in combination with chlorine
 Dose 0.2-1.5mg/Liter.

137.  This method of water disinfection involves the
exposure of a film of water up to about
120mm thick to one or several quartz mercury
vapour arc lamp emitting UV radiation at a
wave length of 200-295 Nanometer.