causes, effects preventions of water pollution

1. WATER
POLLUTION

2. Definition
 Water pollution can be defined as the
addition of foreign substances(pollutants)
to a water source that affects the physical
chemical and biological properties of
water which in turn decreases the utility of
water.....

3. Facts??????????
 Only about 3% surface water is fresh water
 One- fifth of the world population lacks access
to clean drinking water.
 Over 2.6 billion people do not have adequate
toilets.

4.  More than 2 million children are killed by
diarrheal diseases each year
 Earth’s oceans are the most important carbon
sink on the planet along with rain forests
 Demand for water will double in next 30 years
 Floods are most frequent disaster worldwide

5. SOURCES
 *Domestic sewage.
 *Industrial effluents.
 *Agriculture discharges.
 *Other polluting agents.

6. SOURCES OF WATER POLLUTION
 Domestic sewage : It contains human
excreta, kitchen waste, soap, detergent etc…

7. Cont…
 Industrial sewage: It contain pollutants
like acids, alkalis, pesticides, insecticides, oil
refiners, chemical and pharmaceutical
industries etc…

8. Cont…
 Farm sewage: It includes the excreta of
animals, fertilizers, pesticides, organic waste
from trees and plants etc…

9. Cont…
 Other polluting agents: Oil from oil
spills, radioactive pollutants arise from atomic
power plants, hospitals, fine soil particles
etc…

10. Water pollutants
 *Inorganic pollutants.
 *Organic pollutants.
 *Radioactive materials.
 *Thermal pollutants.
 *Sediments.

11. Heavy metals
• Heavy metals such as Cd, Hg and
lead. These elements are not present
in our body but get concentrated in
living organisms
• These elements severely affect the
environment.

12. Cadmium
 SOURCES
1. During extraction of Zn Cd is released as
a biproduct.
2. Cd alloys in fire detection. automatic
sprinkler, solders, valve seals, high
pressure gas containers. These when
disposed is burnt and cd is released to the
atm.

13. Disposal of rechargeable Ni- Cad
batteries

14. EFFECTS
 Replaces Ca in bones. And symptoms
similar to those of Rheumatism set in.
 Causes ITAI ITAI
increased salivation, acute gastric
liver and kidney damage.
 Consumption of contaminated sea food
 Increase in chance of prostate and
Nasopharynx cancer

15. LEAD
 SOURCES
1. Lead acid industries
2. Galvanized Fe connection
3. Automobile emissions
4.Pb smelters
5.Mining and plumbing
6.Burning of coal and oil
7.Pb enters drinking water from old water pipes

16.  EFFECTS
1.Constipation
2.Loss of appetite
3.Abdominal pain and anaemia
4.Liver and kidney damage
5.Gastro-intestinal damage
6.Mental retardation in Children
7.Abnormality in fertility and pregnancy
Lead poisoning also
known as plumbism,
colica pictonium,
saturnism, painter's
colic

17. MERCURY
 SOURCE
1. Embedded in igneous rocks – Basalt and Granite
in the form Cinnabar – HgS ]
2.Broken thermometers, amalgam tooth fillings,
lawn fungicides,
batteries, pharmaceutical products,
manufacture of Cl and caustic soda

18. effects
When the amount of Hg exceeds 1-10mg/l, Hg
is converted into methyl Hg, which when
injested cause
 nerve and brain damage
 Paralysis followed by death
 Affects nervous system and brain
 Cause depression and irritability

19. iiiiiitttii
Mercury causes
Minamata disease.
The disease results in crippling deformi

20. namata disease- the disease
s to crippling deformity.

21.  SOURCES:
 fertilizer and chemical
industries
 biological degradation of
vegetable
 Deamination of organic N
containing compounds
 Hydrolysis of urea
AMMONIA

22. EFFECTS
 increase pH value of water (increases the
alkalinity), causing stomach disorder .
 Produces algae bloom, which in turn reduces
dissolved oxygen, causing damage to aquatic
life.
 Blocks oxygen transfer in the gills of fish.

23. FERTILIZERS
o Fertilizers contain nitrates and phosphates
which in excess over stimulate the growth
of aquatic plants and algae,
o block light to deeper waters while the
organisms are alive;
o when the organisms die, they use up
dissolved oxygen as they decompose,
o diminished amounts of marine life. Such
areas are commonly called dead zones

24. Cont…
EFFECTS:
o causes disease called methanol
globinaemia in children due to high nitrate
concentration- bluish colouration of skin-
conversion of normal Hb into methyl Hb
o nitrates also interfere with oxygen-carrying
capacity of haemoglobin, thereby causing
suffocation.

25. Cont…
o CONTROL
1. Use fertilizers sparingly
2. Choose one with a low phosphorous number.
3. Don’t fertilize before a rain storm.
4. Use organic fertilizers.

26. SEDIMENTS (SILT)
 Silt is granular material of a grain size
between sand and clay derived from
soil or rock.
 Sediments like silt, sand and minerals
are contributed by soil erosion etc…
 They reduce the amount of light
supply to aquatic animals.

27. Sediments (Silt)

28. What are Sediments?
 Impurities in the form of suspended solids
 Occur due to soil erosion
 Undissolved solids, some of which dissolves
over long periods of time and some of which
practically never go into solution
Sources
 Run off by agricultural activities, china clay
industry ,construction and steel industry.

29. effects
 Fill up dams, make water cloudy and muddy.
 Decrease water quality in a physical way.
 Cause physical problems to gill breathers like
fish.

30. SOURCES AND EFFECTS
OF ORGANIC
POLLUTANTS
Detergents, Pesticides, Food Waste,
Radioactive Materials, Thermal
Pollutants

31. Organic Pollution
 Most common form of water pollution.
 Originate from domestic sewage, industrial
effluents and farm wastes.
 Some important organic pollutants are
1) Domestic waste – sewage
with organic matter
2) Infectious agents - sewage
from municipalities causing
microorganisms
3) Organic chemicals – pesticides, insecticides etc.

32. Organic Pollutants

33. 1.Soaps & Detergents
 Collectively called
surfactants because they
are surface tension
reducing agents
 Mainly two components
1) Lyophilic :- merges with
the solvents
2) Lyophobic:- merges with
the oil dirt.
 Detergents mainly 3
types:- anionic, cationic
and non-ionic.

34. Effects:
 Have a poisonous effect on
all types of aquatic life if
they are present in
sufficient quantities
 Destroy the external mucus
layer which protects the
fish from bacteria &
parasites
 Phosphates in detergents
can lead to algal bloom
that releases toxins and
deplete oxygen in
waterways.

35. 2.Pesticides
General term for insecticides, fungicides etc.
Mainly classified as:
1. insecticides
Chlorinated hydrocarbons
Eg: DDT, heptachlor, etc.
2. herbicides
chlorophenoxy acid group
Eg: 2,4-dichlorophenoxy acid
2. Fungicides
dithiocarbamate group
Eg: thiram

36. Effects:
 Biomagnification: Tendency of pollutants to become
concentrated in successive trophic levels.Eg: DDT,
tributyl, tin.
 DDT(dichlorodiphenyltrichloroethane):
• One of the most well-known synthetic
insecticides.
• It accumulates in the insulating sheaths
around nerves and prevents the
transmission of impulses by decreasing the
concentration of the concerned enzyme.

37. Effects……………….
 Fungicides
 Contain Hg which break down soil.
 CH3Hg is used as a fungicide in Iraq for wheat
crop. The bread made from this wheat caused
the death of many human beings.

38.  Radioactive materials enter in to water bodies
 Production of nuclear power releases
radioactive substances in the environment.
 From water they can be transferred to human
body directly or through food chain.
Radioactive pollution

39.  From nuclear power plants and nuclear
reactions. Eg: Sr90, Cs137,Pu248……
 Wastes from U and Th mining and refining
 Use of radioisotopes in research, agricultural,
industrial and medical applications. Eg. C14,
P32, S35, Ca45, Co60, cs137
 From nuclear weapons.
SOURCES

40.  Somatic effects
Burns, cancer and molecular disruptions.
 Genetic effects
high energy radiations can harm genetic material-
chromosomes
 genetic effects transmitted to coming
generations
 radiations lead to abnormalities in offsprings
Effects

41. Discharge of waste heat into natural waters
is termed as thermal pollution
Large amount of water are used for cooling
purpose in thermal and nuclear power plants.
Water is finally discharged in the water body,
temperature raises to 10-16 degrees.
THERMAL POLLUTION

42. THE GREAT LAKES TODAY

43. Effects:

44. Effects
 Rise in temp decreases the dissolved O2 in
water
 Sudden transference of fish to warm water
may result in death.
 Decreases disease resistance of fish.
 Pollutants present in water become more toxic
at elevated temp.
 bring several physiological problems in aquatic
organisms.
 BOD increases with temp.

45. CONTROL OF THERMAL
POLLUTION
 Cooling ponds :warm water is sprayed
into cooling ponds using nozzles, quick
cooling takes place due to the formation of
fine droplets having large surface area.
Cooling towers :transfer waste heat to
atmosphere thru evaporation/heat transfer
Warm water is first stored in earth like
ponds. Natural evaporation brings down
temp, then discharged into nearby water

46. CONTROL OF WATER
POLLUTION
Physical Chemical
Biological
Water
Conservation

47. Physical Treatment Systems:
//Rely on physical processes
for treatment.
//Common processes
screening,filtration,sedimenta
tion and flotation.
//Suspended particles-
removed using gravity.
//Flotation uses diffferences
in particle densities.

48. Filtration tanks

49. Screening

50. Sedimentation

51. Flotation

52. CHEMICAL treatment systems:
precipitation,adsorption
and disinfection reactions.
Precipitation-uses addition of
chemicals to precipitate dissolved
solids(heavy metals and phosphorus).
Adsorption-activated carbon is used
(GAC-Granulated Activated Carbon
PAC-Powdered Activated Carbon)
Disinfection-destroy disease
causing organisms(bacteria and
viruses)
e.g,ozone,ultraviolet
radiation,chlorine,

53. Disinfection by UV rays

54. Biological Treatment
 Utilize biological activity to remove
pollutant from water streams.
 Microorganisms- bacteria- convert
carbonaceous matter into gas.
 Microorganism--- aerobic and
anaerobic

55. Solid pollution control methods:
Landfilling
Composting
Incineration

56. Land filling
 Spreading the solid waste in compact layers
separated by a thin layer of soil.
 biodegradable substances produce CO2 and
CH4.
 Leachate- waste waste water generated from
landfills- treated to avoid ground water
contamination.

57. Composting:
Microbiological
degradation of
organic matter under
either aerobic or
anerobic conditions.
Carried out in static
pile,agitated beds,or
a variety of reactors.
Applicable to
sewage sludge,
paper, food waste,
household garbage.

58. Incineration Process:
Solids are burnt in large
furnaces thereby
reducing the volume of
solid wastes that enter
landfills,etc.
Can be used for metal
reclamation.
Typically supplemented
with air pollution control
devices.

59. Importance of Dissolved Oxygen in
water :
Fish growth is inhibited if dissolved Oxygen
concentration is less than 6ppm.
Lower the oxygen concentration,more polluted is
the sample.
Dissolution of Oxygen into water through the
atmosphere.
Photosynthesis causes water to become
supersaturated during the day time.
Dissolved matter is rapidly consumed by
micoorganisms to oxidise matter of sewage.

60. SEWAGE TREATMENT

61. Sewage is a mixture of domestic and industrial
wastes. It is more than 99% water, but the
remainder contains some ions, suspended solids
and harmful bacteria that must be removed
before the water is released into the sea.

62. Sewage Treatment:
Primary
Treatment
Tertiary
Treatment
Secondary
Treatment
Primary –
physical
Secondary-
Biological
Tertiary -
Chemical

63. Primary Treatment
 Screening
 Sedimentation
 Flocculation
 Chemical coagulation
 Skimming tank

64.  Combination of screens ,filters ,grit chambers &
sedimentation tanks for grit removal.
 Screening – removes large suspended or floating
materials
 Flocculation – removes smaller suspended
particles. Agitating with mechanical stirrers – small
suspended particles collide to form bigger
aggregates which settle down easily.
 Chemical coagulation – sewage treated with
chemical components coagulates to form colloidal
particles.
 Used coagulants : CaCO3, Alum, FeCl3
Primary Treatment
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66. CHEMICAL COAGULATION
COMMONLY USED COAGULANTS ARE
(i)LIME
(ii)ALUMS
(iii) FERRIC CHLORIDE
TO ENHANCE THE SPEED OF COAGULATION SOMETIMES,
COAGULANT AID SUCH AS ACTIVATED SILICA GEL ETC ARE ALSO
USED

68. SECONDARYTREATMENT –Biological
method
Principle
Organic matter is biologically degraded by different
types of microorganisms under controlled
conditions
Aeorobic condition

70. Main processes used duringsecondary treatment
Trickling filters
Activated sludge process
Oxidation ditch
Oxidation pond
Disposal ofsludge

71. Trickling filter
A trickling filter consists of a beds of crushed
stone containing biologoical slimes. (A mucous
substance secreted by certain animals)
Waste waster is allowed to percolate through the
stone beds when the organic matter present in
waste water gets adsorbed on slimes and
undergoes decomposition by the bacteria and
fungi present in the slimes
 Eg. Food processing, pulp and paper mills,
tannery etc

72. Trickling filter

73. Activated sludge process

74. procedure
 Sewage is pumped into a huge tank – mixed with
air bubbles and bacteria rich sludge for a
period of 4 to 10 hours. (mechanical aeration)
 A gelatinous mass loaded heavily with bacteria
is formed and is called activated sludge.
 The carbonaceous matter formed is oxidised to
more stable nitrates, sulphates, and CO2.
 The floc thus formed is pumped out to a
sedimentation tank, allowing the sludge to
settle out for reuse

75. oxidation ditch
 The oxidation ditch is a circular basin lined with
plastic, tar or butyl rubber through which the
wastewater flows.
 Activated sludge is added to the oxidation ditch so
that the microorganisms will digest the waste in the
water.
 Longer retention times are needed for better
results.

77. Oxidation pond
 A pond that contains partially treated
wastewater which is then left to allow the
growth of algae and bacteria which
decompose the rest of the waste.
 Oxygen required by the bacteria is provided by
algae present in the pond.
 Organic matter undergoes anaerobic oxidation
by bacteria to CH4 ,CO2 & NH3 .
 Heavy metal ions are precipitated as
hydroxides and form sludge.

78. Disposal of sludge
 This method consists in digesting the sludge in
circular digestors 6-10 meter deep maintained at
35degree celcius and pH 7-8 for about a month.
 Slow fermentation forms gases consisting of about
70% methane and 30% CO2 with other gases.
 After treatment, sludge gets converted into a stable
humus material which can be used as a low grade
fertilizer.

79. Other sludge handling methods
 Denaturing by drying on sand beds
 Vacuum filtration
 Centrifuging
Denatured sludge is then disposed off by
incineration or composting.
Incineration, however, can lead to air pollution

80.  To remove chemicals in waste water after 10 and
20 treatment.
 Methods include :
 Coagulation & Sedimentation – waste water
treated with chemical coagulants in which
suspended matter gets coagulated and then
filtered.
 Carbon adsorption – waste water filtered
through activated carbon
 Chemical Oxidation – Organic contaminants are
oxidized by reagents like O3
Tertiary Treatment
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81. The major tertiary methods includes:
1.COAGULATION AND SEDIMENTATION:In
this process,the waste is treated with chemical
coagulants such as alum, ferric chloride ,etc. as
a result of which the suspended matter gets
coagulated.

83. 2.Carbon Adsorption: The waste water is filtered
through activated carbon to eliminate materials
responsible for colour and undesirable tastes and
odours.

84. 3.Chemical Oxidation: Organic contaminants are
oxidised by several reagents like ozone and pottassiun
permanganate.

85.  4.Reverse Osmosis : In this process,
waste water is separated from fresh
water by a semipermeable membrane
which allows the water to move to it
but not the dissolved material.

86.  5.Biological Methods: The dissolved
organic materials such as nitrates and
phosphates can be directly removed from
the water by certain aquatic plants such as
duckweed.

87.  Reverse osmosis – waste water separated
from fresh by semipermiable membrane.
applying pressure > osmotic pressure of waste
water, pure water from waste forced to other
side of membrane.
 Biological process – Algae and waste
hyacinths consume nitrates and phosphates.
bcdss

88. Tertiary Treatment:
//Both primary and secondary
treatments remove 90% of the oxygen
demanding organic wastes.To remove
chemicals left in the waste water after
primary and secondary
treatment,tertiary treatment is carried
out.
//Primarily chemical methods are used.
•Coagulation
•Carbon Adsorption
•Chemical Oxidation://Organic
contaminants oxidized by several
reagents like ozone and potassium
permanganate.
•Reverse Osmosis
•Biological Methods://Algae and water
hyacinths grown in ponds can be used
to consume nitrates and phosphates.

89. EUTROPHICATION
 Addition of artificial or non artificial
substances, through fertilizers to fresh water
system
 nutrient enrichment of water body
 Nitrogen and phosphorus present as
phosphates and nitrates
 Rate of increased respiration rates causes
excess organic matter to accumulate in water
stimulating bacterial activity

90. CAUSES

91. Causes of Eutrophication
 growth of pathogenic organisms due to
decrease of dissolved O2.
 species diversity to decrease because of
increased algae growth
 increase of turbidity
 increase in the rate of sedimentation, shortening
the life span of lakes
 obstruction to the flow of water

92.  difficulties in the treatment of water for drinking
purpose
 extensive fish mortalities in shallow lakes
 methaemoglobinaemia in infants by bottle fed
milk

93. CONTROL

94. Eutrophication control
 phosphate stripping of water using coagulants
of lime or compounds of Al or Fe
 use of micro organism
 By treatment of ponds where much of it is
absorbed on to particular matter which will
settle out in the pond itself
 Planting of buffer strips (vegetated strip of land
of some 5-50m wide) between farm land and
water body

95. DESALINATION OF WATER
 Desalination is the process of removal of salts
from water.
 Water containing high concentration of
dissolved salts is called Brackish water.
 For example, sea water contains 35000 ppm
of dissolved salts.
 Brackish water cannot used for domestic and
industrial uses.

96. DESALI NATI ON OF
WATER
 Process of removing common salt(NaCl)
from water
 Commonly used methods of Desalination
of Water are:
1) Electrodialysis
2)Reverse Osmosis

97. Normal Osmosis
 When two solutions of different
concentrations are separated by a semi-
permeable membrane, the solvent
molecules flow from a region of low
concentration to high concentration. This
phenomenon is called osmosis.
 The semi permeable membrane is a selective
membranes which does not permit the
passage of dissolved alts. The flow of solvent
molecules continues till the concentration
becomes equal on both sides.

99. Reverse osmosis
 The process of reversing the flow of
solvent molecules by applying pressure in
excess of osmotic pressure, on
concentrated solution side is shown as
reverse osmosis.
 (If a hydrostatic pressure in excess of osmotic
pressure is applied on concentrated side, then
solvent molecules are forced o move from
concentrated side to dilute side across the
membrane)

101. Reverse Osmosis
Pure solvent is seperated from its
contaminates,rather than removing
contaminates from the water

102. A RO Membrane
Feed Water
Pump
RO
Membran
e(s)
Product Water
Control Valve
Reject to
Drain
Water enters the RO membrane
under pressure and travels from the
feed end to the reject end. Some of
this feed water passes through the
membrane and becomes purified.
This water is called the RO product
water. The contaminants that were
previously in the product water exit
the membrane in the reject water.

103. Spiral Wound Membrane Element
Several layers of membrane material are sandwiched between spacer
material to form leaves with a feed / reject channel and a product channel.
These leaves are then rolled around a central product collection tube. This
assembly is referred to as a spiral wound membrane element. The spiral
wound membrane element is installed in a pressure vessel. A seal between
the outside of the membrane and the inside of the pressure vessel prevents
the feed water from flowing between the membrane and pressure vessel.
This is called a brine seal. Membranes should always be installed with the
brine seal on the feed end of the vessel. (Before entering the seawater in
reverse osmosis membranes, clarified seawater is pressurized by the High
Pressure Pump typically between 55 and 85 bars, depending on the
temperature and the salinity of the water.

104. Typical RO unit

105. Advantages
 Desalination by reverse osmosis removes
ionic impurities as well as colloidal silica.
 Both organic and inorganic contaminants can
be removed.
 Capital and operating expenses are low.
 Energy requirement is 30% lower than that of
distillation process.
 Operated at a comparatively low temperature.

106. Electrodialysis
 Electrodialysis is the process of removal of
dissolved salts by migration of ions present in
water towards their respective electrodes,
through ion- selective membranes under the
influence of applied emf.
 Electrodialysis (ED) is used to transport salt
ions from one solution through ion-exchange
membranes to another solution under the
influence of an applied electric potential
difference.

107. This is done in a
configuration called an
electrodialysis cell. The
cell consists of a feed
(diluate) compartment
and a concentrate (brine)
compartment formed by
an anion exchange
membrane and a cation
exchange membrane
placed between two
electrodes

108. The anion selective membrane contains positively charged
functional groups such as R4N+ and only anions pass through it
as cations are repelled by it.
Similarly, the cation selective membrane contains negatively
charged functional groups such as RCOO- or RSO3 and only
cations can pass through it as anions are repelled by it.
When electric current is applied across the electrode, cations (
Na+ions) move towards cathode and anions (CI- ions) move
towards anode through ion selective membranes.
It result in removal of ions from central compartment and pure
water is collected at bottom.

110. Reactions
Cathode Reactions
 At the cathode,
 2e- + 2 H2O → H2 (g)
+ 2 OH-
Anode reactions
 At the anode,
 H2O → 2 H+ + ½ O2
(g) + 2e- or 2 Cl- →
Cl2 (g) + 2e-

111. ADVANTAGES ELECTRODIALYSIS
 It is most compact unit
 The cost of installation of the plant and its
operation is economical
 If electricity is easily available ,it is best suited