‫بسم هللا الرحمن الرحيم‬
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PURIFICATION OF WATER
It is of great importance for promoting
health and preventing disease.
Purpose of water treatment, is
 To produce water that is safe and wholesome.
 Ground water (e.g., wells and springs) may need
no treatment, other than disinfection, surface
water (e.g., river water) which tends to be turbid
and polluted, requires extensive treatment.
 Components of water purification system are
Storage, Filtration and Disinfection.
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Methods of Water Purification
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Water purification is done on small scale
at domestic level and large scale.
Methods of Purification
Natural methods of purification
Man –made methods of purification
NATURAL METHODS OF PURIFICATION
The natural methods by which water is purified are: Dilution
 Sedimentation
 Oxidation
 Aeration
 Ultraviolet rays
 Action of Aquatic plants and animals
 Action of sunlight
 Some measure of disinfection is accomplished by
exposure to sun light provided that there is time for
biochemical stabilization of organic matter and
destruction of microorganisms.
Purification on small scale
Boiling (5 to 10 minutes kills off most microorganisms and
removes temporary hardness)
Distillation: By this method get rid of all impurities
Chemical Disinfection:
Chlorine solution (small quantity of 5% bleaching powder
solution is sufficient for chlorination of water)
Chlorine tablets ( 1 tablet is required for 1 liter of water)
Iodine ( 2 drops of 2% solution of iodine is required for 1
liter of water)
Potassium permanganate (a little amount giving pink
coloration)
Alum ( .1 to .4 gram is required for 5 liters of water)
Three pot domestic filtration:
FILTERATION
Filtration systems are of two types
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SLOW SAND OR BIOLOGICAL FILTERS
Elements of a slow sand filter
Essentially these consist of, supernatant (raw) water, a bed of
graded sand, an under – drainage system; and a system of filter
control valves
Supernatant water 1 to 1.5 meter
Sand bed
1.2 meters
Gravel support
0.3. Meter
Filter bottom
0.16 meter
Vital Layer
It develops in first few days and consists of threadlike algae. It
removes organic matter and holds back bacteria.
RAPID SAND OR MECHENICAL FILTERS
The raw water is first treated with a chemical such as
alum, the dose of which varies from 5-40mg or more per
liter, depending upon the turbidity, the gentle stirring
results in the formation of a thick, flocculent precipitate
of AloH. These are removed by sedimentation and rapid
sand filters.
SURVEILLANCE OF DRINKING WATER QUALITY
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Sanitary survey:
Sanitary survey is an on-the-spot inspection and evaluation by
a qualified person of the entire water supply system. The
purpose of the survey is detection and correction of faults and
deficiencies. A sanitary survey is essential for adequate
interpretation of laboratory results.
Sampling:
Sampling of water should be done with the thoroughness of a
surgical operation, with the observation of similar aseptic
precautions, it depends upon the results of analysis. It should
be carried out by competent and trained personnel.
Bacteriological surveillance:
The tests usually employed in water bacteriology are
presumptive coliform test .Tests for the detection of faecal
streptococci and Cl. Perfringens is also done. A complete
bacteriological examination consists of all these tests.
Examination of Water
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Before water from any source is declared
fit for human consumption, it is essential
to take the sample and carry out the
following examinations.
Physical examination
Chemical examination
Bacteriological examination.
Informations required for sampling
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The following information should be furnished
along with the sample of water.
Source of water supply
Geological formation of the soil if available
In case of well, its depth, diameter and how it is
used.
Any suspected source of pollution in the vicinity.
Whether any method of purification is used.
Sample Collection
Sampling from the stream:
Water is taken from the middle of a
stream.
With the mouth of the bottle facing
upstream, lower the bottle into the stream
and allow to fill. Tilt bottle upwards to fill
completely, the cap is carefully screwed
back, taking care not to touch the screw
thread at the top of the bottle, nor the
inside of the cap.
Sampling from a Well
Tie a sample bottle on to a weighted
length of a rope or strong string. Use a
stone or piece of metal weighing about
500g as the weight and attach the bottle
just above it. After removing the cap
aseptically, lower the bottle into the well
to a depth of about 1 m. when no more
air bubbles rise to the surface, raise the
bottle out of the well and carefully replace
the cap.
Sampling from a tap
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Flame a tap till it is red hot to ensure that
it is sterilized, from the inside. Turn the
tap full on and allow the water to run to
waste for one minute. Close the tap until
only a slow trickle of water is coming out
and fill the sampling bottle. Carefully
replace cap.
Water Quality – Criteria and Standard
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The guideline for drinking water quality
recommended by WHO (1993 and 1996)
relate to following variables:
Acceptability aspects
Microbiological aspects
Chemical aspects
Radiological aspects
Acceptability Aspects
Physical
Constituents or
characteristics
Acceptability Aspects
Physical parameters
Colour
Taste and odour
Temperature
Turbidity
Appearance
Should be acceptable
Should be acceptable
Should be acceptable
No turbidity
Acceptability Aspects
Chemical
Inorganic constituents Effects
Aluminium
Ammonia
Chloride
Copper, Iron, Manganese
Hardness
Hydrogen sulfide
Dissolved oxygen
pH value
Sodium
sulfate
Total dissolved solids
Zinc
Depositions, discoloration
Odour and taste
Taste, corrosion
Staining of laundry and sanitary ware
High hardness: scale deposition, scum formation; low
hardness; possible corrosion odour and taste
Odour and taste
Guideline value 0.5 mg/L.
Low pH: corrosion; high pH: taste, soapy feel
preferable < 8.0 for effective disinfection with
chlorine
Taste
Taste, corrosion
Taste
Appearance, taste
Microbiological Aspects
Organisms
Guideline value
All water intended for drinking
E.coli or thermo tolerant coli form
bacteria
Treated water entering the distribution
system
E.coli or thermo tolerant coli form
bacteria
Total coli form bacteria
Treated water entering the distribution
system
E.coli or thermo tolerant coli form
bacteria
Total coli form bacteria
Must not be detectable in any 100 ml
sample
Must not be detectable in any 100 ml
sample. In the case of large supplies, where
sufficient samples are examined, must not
be present in 95% of samples taken
throughout any 12-month period.
CHEMICAL ASPECTS
Iodine deficiency
Goiter
Excess Fluoride
Dental flourosis
Fluoride deficiency
Dental caries
Excess inorganic salt
Diarrhea
Cadmium
Gastric upsets
Sodium
Hypertension
Sulfates
Laxative effect
Nitrates and nitrites
Methaemoglobinaemia
Typical Non infectious diseases associated with
water supply (Heavy Metals)
Lead
Lead poisoning
Arsenic
Black foot disease
Arsenic
Skin and lung cancer
Cadmium
Itai-itai disease
Cadmium
Nephropathia
Mercury
Minimata disease
Mercury
Nephropathia
Radiological Aspects
There are two types:
1.
Somatic effects
Any exposed individual manifest the
radiological effects these are called somatic
effects e.g., development of carcinomas.
2. Hereditary effects:
The pregnant ladies manifest the radiological
effects in the growing fetus in the form of
hereditary changes.