water pollution and water borne diseases

1. ENVIRONMENT AND HEALTH
WATER
DEVIPRIYA P V
M PHARM

2. Water pollution
 When natural colour and taste of water is
changed and bad smell comes out from water
due to any kind of contamination higher than
the permitted limits is called water pollution.
 Contain both dissolved and suspended
impurities.
 Dissolved impurities -hydrogen sulphide,
CO2, N2, NH3 and mineral salts.
 Suspended impurities – sand, mud clay, dry
leaves , plants, bacteria etc.

3. Causes
 Rapid urbanization and industrialization.
 The disposal of sewage from township to
water bodies.
 Industrial waste from electroplating, dying,
vegetable oil, paper, textile, sugar, jute and
iron industries, tanneries and milk plants.
 Fertilizers and pesticides from agriculture.
 All these contain toxic chemicals harmful for
humans.
 Harmful to agricultural crops, fish and other
water animals.

4. Water Borne Diseases
 Definition: Consumption of contaminated water with
pathogenic microorganism lead to diseases.
 Classified into:
1. Bacterial diseases: Diarrhoea, Typhoid, Cholera,
Dysentery.
2. Viral diseases : Poliomyelitis, Viral Hepatitis
3. Protozoal diseases: amoebiasis, giardiasis
4. Worm infections: roundworm , thread worm
5. Other diseases due to the presence of aquatic host:
Guinea pig and tape worm
6. Diseases due to toxic substances: lead , arsenic,
mercury, cadmium etc

5. Purification of water
 Large scale purification of water
1. Slow sand filtration (Biological filtration)
2. Rapid sand filtration (mechanical filtration)
 Slow sand filtration:
 Contain 3 stages
1. Storage
2. Filtration
3. Chlorination

6. Storage
 Raw water from source(rivers, streams etc) is
collected in large open reservoirs known as
settling tanks.
 Allowed to remain for 1-2 days for natural
purification.
 Suspended impurities settle by gravity.
 Organic matter is oxidised by bacteria with
the help of dissolved O2
 Water becomes clearer in appearance.

7. Filtration
 Second and very important stage.
 About 99% bacteria is removed at this stage.
 The clarified water from storage tank is
transferred to slow sand filters.
 The filter beds are water tight rectangular
tanks made of concrete and usually kept
open.
 The beds are usually 2.5-4 meters deep.
 The water is filtered through the bed.

8.  They are filled from bottom to upwards as
follows:
 Lowest layer contain 4cm size gravel or broken
stones.
 Above this , fine gravel layer of 15-30 cm
thickness.
 Above this coarse sand of 15-30 cm thickness.
 Above this layer is fine sand from 60-90 cm
thickness. They provide large surface area for
water to pass through as the particle size is
very small.
 On top is the clarified water from the settling
tanks(1.5-1.8m in height).
 The inlet of water is controlled by valves fitted

10.  Vital layer formed at surface of sand play an important
role in the purification.
 It is the thin green slimy gelatinous layer which
consists of numerous plant and animal life like algae,
bacteria, fungi etc.
 The process of formation of vital layer is known as
ripening of filter.
 Formed within 2-3 days on a new filter bed.
 It is about 2-3 cm in thickness.
 As thickness increases filtration decreases.
 When thickness increases to about 4 feet , cleaning of
filter is done.
 On repeated cleaning, efficiency decreases-new bed
is prepared.
 Usually done after an interval of 3 years

11. Slow sand filters- Advantages and Disadvantages
Advantages Disadvantages
 More practicable for
filtration of water with
minimum filtration.
 Accepted as standard
method of purification.
 They yield 98-99%
bacteria free water.
 Initial cost is more as
more land is required for
construction.
 They require periodical
cleaning.

12. Rapid sand filtration
 Two types:
1. Gravity type eg: Paterson’s filter (commonly
used)
2. Pressure type eg: Candy’s type.
 5 stages of rapid filtration:
a) Coagulation
b) Mixing
c) Flocculation
d) Sedimentation
e) Filtration

13.  Coagulation:
 The water from settling tank is led into plant
and is treated with chemical coagulants such
as alum.
 To remove turbidity and colour.
 Alum used: 5-40 mg per liter(depending on the
turbidity of water).
 Mixing:
 Agitated mechanically in a mixing chamber for
few minutes.
 To dissolve alum and thus the impurities get
precipitated.

14.  Flocculation:
 Then passed into flocculation chamber.
 Stirred at slow speed for half an hour
 Floccules of aluminium hydroxide is formed.
 Sedimentation:
 Water is transferred to settlement tank where
the particles settle at the bottom of the tank.
 Allow to remain for 2-6 hours.
 The precipitates along with suspended matter
settle at bottom and is removed.
 Filtration:
 The clarified water is led to rapid sand filter.
 Purifies water from 98-99%

15. Cleaning of filters
 As the filter bed becomes dirty due to
floccules, suspended matter and bacteria in
the vital layer.
 Back washing is done for cleaning.
 For this inlet and outlet valves are closed.
 water is flowed from bottom of sand bed and
the upper layer of sand is stirred.
 Thus the deposited dirt will be dislodged and
removed.
 Cleaning is stopped when the sand looks
clear.

16. Rapid sand filters- Advantages and Disadvantages
Advantages Disadvantages
 Very little space is
required
 Less initial cost
 Suitable for turbid water.
 Rapid process.
 Cleaning is easy.
 No chances of
contamination by the
labourers.
 High running cost.
 Chemical coagulants like
alum are required.
 Results of purification are
not good so chlorination
of water is required.

17. Chlorination
 Last step in purification.
 For sterilization of water.
 Kills the harmful bacteria and make water safe for
drinking.
 Oxidises organic matter and destroys bad taste &
smell.
 Chlorine in the form of gas or solution or as bleaching
powder is used.
 Chlorine gas is used for chlorination of large
quantities of water because it is cheap, easily
available, effective and quick in action but it irritates
eye and poisonous.
 When chlorine is used, the water should be clear, and
is not effective in turbid water.

18. Action of chlorine
H2O + Cl2 HCl+ HOCl
(Hypochlorous acid)
HOCl H+ OCl
(Hypochlorite)
 The germicidal action of chlorie is effective at
neutral pH(7)
 The chlorine demand has to determined
before chlorination (the amount of chlorine
required for disinfecting).
 A known amount of chlorine is added to
water, the undissolved amount is calculated
after half an hour

19.  The difference between the values gives
the amount of chlorine dissolved.
 Break point:
 When the process of disinfection is
complete and if more chlorine is added the
free chlorine will start appearing in water.
The point where free chlorine appears in
water is called break point.

20.  Contact period:
 After the addition of chlorine, at least one hour
is required for the chlorine to produce its
action, the time period is called contact period,
where the chlorine kills the bacteria and
oxidizes the organic matter.
 Free residual chlorine :
 The little excess of chlorine added at the end
of one hour chlorination .
 Usually 0.5 mg per liter.
 If more amount is added it gives the taste and
smell of chlorine.
Total amount of chlorine required for disinfection = demand+0.5
mg/liter free residual chlorine

21. Small scale purification of
water
1. Boiling
2. Distillation
3. Filtration through muslin cloth
4. Three pitcher system
5. Chemicals
6. Domestic filters--Eg:Berkefeld filter
Pasteur’s chamber-land filter.

22. Boiling
 Boiling for 5-10 min kills bacteria, spores, cysts and
ova of intestinal parasites.
 Removes the hardness of water.
 Done in a neat and clean vessel.
 After boiling the water is stored in a clean covered
container

23. Distillation
 All kinds of dissolved and volatile impurities can be
removed.
 First and last portion of the distillate is rejected as it
contain volatile matter which can further
contaminate the distilled water.
 Not possible for the purification of water for routine
household purposes.

24. Filtration through muslin cloth
 Muslin cloth act as a coarse filter.
 It can remove the suspended materials.
 Not fit for drinking.
 Used for other purposes like washing the clothes,
bathing etc.

25. Three pitcher system
 3 pitchers are used which are kept one above the
other on a wooden stand.
 The top pitcher contain sand, second charcoal and
sand; and lowest collects the purified water.
 The raw water is filled in first pitcher from where it
flows through a hole into the 2nd one and finally to
the last.

27. Chemicals
1. Bleaching powder (chlorinated lime)
2. Chlorine tablets
3. Quick lime(calcium oxide)
4. High test hypochlorite(HTH).
5. Alum
6. Potassium permanganate(KMnO4).
7. Bromine and Iodine

28. Bleaching powder (chlorinated lime)- CaOCl2.
 Fresh sample has 33%chlorine content.
 On storage it looses chlorine content. So stored in dry,
air-tight containers at cool and dark places.
 2.5 gm is used to disinfect 1000 liters of water.
Chlorine tablets:
 for disinfecting small quantities of water.
 Available in diff. strengths.
 500 mg tablet for disinfecting 20 liters of water.
Quick lime(calcium oxide):
 Cheap, easily available and effective
 Disinfecting wells and tanks in cholera outbreak.
 Disadvantage: large dose is required

29. HTH:
 A calcium compound that contain 65-75% chlorine
Alum :
 Used to purify muddy water and removes turbidity
 60-240 mg can purify 4-5L of water.
Potassium permanganate:
 A strong oxidising agent.
 Can kill cholera vibrios.
 Used for disinfecting wells(dose=0.5ppm).
 Disadvantage: alters taste,smell and color of water.
Bromine and chlorine:
 Used only in emergencies.
 Not a routine disinfectant.
 Disinfect water within half an hour.
 Bromine dose is 3.5 mg per liter of water
 Iodine dose=2ppm

30. Domestic filters
 For purification of
water used for drinking
purpose.
 Berkefeld filters:
 These are cylindrical
filters known as filter
candles or ceramic
candles.
 Made up of unglazed
poreclain or
kieselguhr.
 Need adequate
cleaning as the pores
get clogged

31. Pasteur’s chamberland filter
 It is made up of unglazed
poreclain tubes which are
screwed on to a water tap.
 Work only under pressure
 Can’t used for filtration of
muddy water as the pores
get blocked.
 Quick and reliable .
 Make water free from all
kinds of impurities
including bacteria.

32. Disinfection of wells
 Common source of water supply.
 So it should be disinfected regularly to keep
water fit for drinking and domestic purposes.
 Bleaching powder is used as it is cheap and quite
effective disinfectant.
Steps involved:
1. Measurement of well for its depth
2. Amount of water in the well
3. Amount of bleaching powder required.
4. Mixing the bleaching powder
5. Addition of bleaching powder solution in the well
6. Ortho-toludine test

33. Measurement of well:
 Diameters and depth is measured with a rope tied with
some weight.
 The rope is lowered in well till it touches the bottom of
well
 The rope is taken out and the wet portion is measured
which gives the height of the well.
Amount of water present in the well:
 V=∏r2h x 1000 litres
 Where, V= volume of water; ∏= 22/7; R= radius(m)
H=height(m).
Amount of bleaching powder required
 10 gm for 1500L of water.
 Amount can vary according to the impurities present

34. Mixing of bleaching powder:
 Add small amount of water and made it to a paste.
 Add more water with stirring until bucket is ¾ full.
 Allow to stand for 5-10 min.
 Transfer the supernatant clear liquid to another bucket
and discard the sedimented lime.
Addition of bleaching powder in the well:
 Lower the bucket containing chlorine solution into the
well .
 Agitate the water by lowering the bucket several times
to mix the solution with the well water.
 Allow to remain in contact for one hour.
 No water is taken during this time
 This will kill the pathogenic microorganism

35. Ortho-toludine test:
 Performed after one hour to check whether the
water is properly chlorinated.
 Free residual chlorine is tested.
 if it is less than 0.5 mg/L, additional quantity of
bleaching powder has to be added.
 Chlorinated water is taken in a test tube and add
2-3 drops of Ortho-toludine in 10% solution of
HCl
 Appearance of yellow color indicates sufficient
chlorination
 Red colour indicates excess chlorination.

36. Hardness of water
 Water which produce lather difficulty with soap is
known as hard water.
 Water which produce lather readily with soap is
known as soft water.
 Hardness is the soap destroying power of water.
 Occurs due to the presence of salts ie,
bicarbonates, chlorides and sulphates

37. Disadvantages of haerness of
water
1. Wastage of soap and detergents.
2. Unsuitable for cooking some vegetables, dal and
meat . (takes long time to cook in hard water).
3. Not suitable for washing(not cleaned properly and
have no long life).
4. Harmful for industrial purposes.
5. Harmful to health(diarrhoea and digestive
disorders).
6. On boiling calcium carbonate deposits on the inner
walls of boilers and kettles-scaling or furring of
boilers.

38. Types of hardness of water
 Temporary hardness
 Permanent hardness
 Temporary hardness:
 Due to the presence of bicarbonates of Ca and Mg.
 It can be removed by boiling.
Ca(HCO3)2 CaCO3 + H2O + CO2
Mg(HCO3)2 MgCO3 + H2O + CO2.
 Also removed by adding lime or Ca hydroxide
(Clark’s process).
CaHCO3+ Ca(OH)2 2CaCO3 + 2H2O

39. Permanent hardness:
 Due to the presence of chlorides and sulphates of
calcium and magnesium.
 Not removed by boiling
 It can be removed by adding sodium carbonate or
soda ash.
CaSO4 + Na2CO3 Na2SO4 + CaCO3
 Also removed by Base exchange or Permutit
process
 Sodium Permutit is a loose compound of sodium,
aluminium and silica.
 When hard water is passed through it the Ca and Mg
ions are exchanged with sodium ions, thus hardness
is removed.