2. Water treatment is the process of making
water suitable or acceptable for an end-use.
It removes existing water contaminants and so
reduces their concentration that the water becomes fit
for its desired application.
Why Water Treatment?
Natural waters are rarely of satisfactory quality for human
consumption or industrial use and nearly always needed to
be treated.
2
3. In the United States and the United Kingdom,
by far the most common sources of raw freshwater
are rivers and lakes, though in recent decades, more
sources of groundwater are being utilized.
Some groundwater sources are so pure that no
treatment is necessary although when used for public
supplies, local water authorities tend to apply a
disinfection process, but this is primarily for
disinfection purposes of the distribution network.
3
4. The objectives of water treatment are to produce:
Water that is safe for human consumption
Water that is appealing aesthetically to the consumer
Water at a reasonable cost
4
5. Advanced water treatment processes are often
required by industry, e.g. the beverage or
pharmaceutical industries. Such industries
may have higher standards than those for
potable supplies.
5
6. Public water supplies normally service
the requirements of:
Domestic households
Fire fighting
Industrial
Commercial
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9. Development of New Water Sources:
Angat Dam - the only present source of water supply for the MWSS
service area serving a total of 13 million population out of the total
service population of 15 million, or only 87% total service coverage.
Angat Dam provides a supply volume of 4,000 million liters per day
(4,000 mld) out of the present demand of 4,395 mld, or a deficit of
395 mld.
By 2015, the projected demand is expected to reach 5,054 mld, thus
requiring the development of supplementary sources of water to
address the increasing demand.
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10. In discussing water quality, two sets of
standards exist:
The quality of raw water
The quality of the treated potable water
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13. Turbidity
Turbidity refers to how clear the water is
The greater the amount of total
suspended solids in the water, the
murkier it appears and the higher the
measured turbidity
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14. Materials that cause water to be turbid
include
Clay
Silt
Plankton
Microscopic organisms
Soluble colored organic compound
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15. COLOUR
Colour is an optical parameter consisting
in absorbing of a part of spectrum of
visible radiation by substances dissolved
in water, and suspension particles present
in water or sewage.
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16. Colour in water may appear as the result of
different sources activity:
type of vegetation
decay of plant matter
algae growth
plankton
minerals (iron, manganese and copper)
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17. TASTE AND ODOUR
are usually inter-related.
Compounds in water that are perceived
as giving it a taste are generally inorganic
substances present in concentrations such
higher than those of organic pollutants
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18. TASTE AND ODOUR
Inorganic chemicals that can affect taste
but not cause any odour are salt, minerals,
metals.
A few inorganic chemicals can cause
both taste and odour problems. These are
ammonia, chlorine, hydrogen sulphide.
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19. TASTE AND ODOUR
Organic chemicals usually affect both
taste and odour: the compounds
concerned include hydrophilic acids,
carboxylic acids, amino acids,
carbohydrates, hydrocarbons, biological
decay products, petroleum products and
pesticides.
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20. Physico-chemical parameters
Temperature and pH
Conductivity (salinity)
Chlorides
Sulphates
Silica
Calcium
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25. Water for treatment and subsequent public
consumption is normally sourced from:
Rivers: upland and lowland
Lakes and reservoirs
Groundwater aquifers
The selection of the source is governed by many
factors, including proximity to the consumers,
economics, long-term adequacy of supply and raw
water quality.
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26. Each source presents its own problems
Surface water has elevated levels of soil particles and algae,
making the water turbid
may contain pathogens
Groundwater has higher levels of dissolved organic matter (yellow color)
and minerals such as iron
Both sources may have high levels of calcium and magnesium (hardness)
both can be contaminated by toxic chemicals
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27. Four classes of water treatment:
Class Description Source
A No treatment Some borehole
water
B Disinfection only Occasional upland
water, some
borehole water
C Standard water treatment Lowland rivers and
reservoirs
D Special Water Treatment Some rural supplies
(Fe and Mn)
Color removal
Industrial water
Algae removal
Organics removal
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28. Screening
Coagulation
Flocculation
sludge
Sedimentation
Filtration
Disinfection
Storage
Distribution
Raw water
Alum
Polymers Cl2
sludge
sludge
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29. Removes large solids
logs
branches
rags
fish
Simple process
may incorporate a mechanized trash removal system
Protects pumps and pipes in Water Treatment Plants
30. Small particles are not
removed efficiently because
they settle too slowly
they may also pass through
filters
easier to remove if they are
clumped together
Coagulated to form larger
particles, but they don't
because they have a negative
charge
repel each other (like two
north poles of a magnet)
In coagulation
we add a chemical such as alum
which produces positive charges
to neutralize the negative charges
on the particles
particles can stick together
forming larger particles
more easily removed
process involves addition of
chemical (e.g. alum)
rapid mixing to dissolve the
chemical
distribute it evenly throughout
water
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31. Aluminum Sulfate Al2(SO4)3
Ferrous Sulfate FeSO4
Ferric Sulfate Fe2(SO4)3
Ferric Chloride FeCl3
Lime Ca(OH)2
Aluminum salts are cheaper but
iron salts are more effective over
wider pH range
31
32. Now the particles have a neutral
charge
They can an stick together
The water flows into a tank with
paddles that provide slow mixing
bring the small particles together to
form larger particles called flocs
Mixing is done quite slowly and
gently in the flocculation step
If the mixing is too fast, the flocs
will break apart into small particles
that are difficult to remove by
sedimentation or filtration.
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33. 33
Water flows to a tank called a
sedimentation basin
Gravity causes the flocs to settle to the
bottom
Large particles settle more rapidly
than small particles
It would take a very long time for all
particles to settle out and that would
mean we would need a very large
sedimentation basin.
So the clarified water, with most of
the particles removed, moves on to the
filtration step where the finer particles
are removed
34. The filtration apparatus is a concrete box which contains sand
(which does the filtering), gravel (which keeps the sand from
getting out) and underdrain (where the filtered water exits)
After the filter is operated for a while, the sand becomes
clogged with particles and must be backwashed
Flow through the filter is reversed and the sand and particles are
suspended
The particles are lighter than the sand, so they rise up and are
flushed from the system. When backwashing is complete, the
sand settles down onto the gravel, flow is reversed and the
process begins again
34
35. With particles removed, it
only remains to
provide disinfection, so that
no pathogens remain in the
water
Protozoan pathogens are
large in size and have been
removed with other particles
Bacteria and viruses are
now destroyed by addition
of a disinfectant
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36. Chlorination
Enough chlorine is
added so that some
remains to go out in the
water distribution
system, protecting the
public once the water
leaves the plant
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37. Pumping of the clean
water produced at the
treatment plant to the
community is
called distribution
This can be done directly
or by first pumping the
water to reservoirs or
water storage tanks
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38. Water fluoridation is the controlled addition
of fluoride to a public water supply to
reduce tooth decay. Fluoridated water has
fluoride at a level that is effective for
preventing cavities; this can occur naturally or
by adding fluoride.
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39. Ground waters are more likely to have a
higher fluoride content.
Most surface water have negligible amount.
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41. Purposes:
To take a water treated by standard processes and to
improve it to exceptionally high quality as often
required by particular industries.
To treat a water containing specific chemical or
microbiological contaminants to an acceptable standard,
i.e removal of iron and manganese, the removal of blue-green
algae, the removal of specific organics
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44. Techniques Used:
Iron and manganese removal - iron is removed by
pressure filters while manganese is removed by gravity
sand filters
Ion Exchange and inorganic absorption - water
softening by exchanging undesirable calcium and
magnesium cations with sodium. Also used to remove
undesirable cations including barium, strontium and
radium and undesirable anions including fluoride,
nitrates, silicates and chromates
44
45. Techniques Used:
Adsorption of organics – undesirable contaminants are
adsorbed on to solid adsorbents.
Membrane processes – uses microfiltration,
ultrafiltration, reverse osmosis, electrodialysis
Oxidation including chemical oxidation – two or more
chemical species are added with the purpose of
increasing the oxidation state of one.
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46. 46
The Angat River is the largest and
most important source of water for our
region.