SLIDE WATER TREATMENT PROCESS WASTE WATER SUBJECT.pdf
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About This Presentation
NOTES FOR WATER TREATMENT PROCESS
Slide Content
WATER TREATMENT
PROCESS
WEEK 10
PROCESS
WEEK 10
Lesson Outcomes
Understand the water treatment process
Understand the water treatment process
Introduction
Most raw water sources in Malaysia require treatment for safe human consumption.
Reason: Ensuring water meets public health and safety standards.
National drinking water standard
Most raw water sources in Malaysia require treatment for safe human consumption.
Reason: Ensuring water meets public health and safety standards.
National drinking water standard
Water Treatment Processes
1.Chemical Treatment:
Coagulation, chlorination, etc.
2.Physical Treatment:
Filtration, sedimentation.
3.Biological Treatment (in special cases):
Removal of organic contaminants.
1.Chemical Treatment:
Coagulation, chlorination, etc.
2.Physical Treatment:
Filtration, sedimentation.
3.Biological Treatment (in special cases):
Removal of organic contaminants.
Summary of typical water treatment
processes
1.Intake
2.Screening
3.Pretreatment
4.Chemical Mixing
5.Coagulation and Flocculation
6.Clarification
7.Filtration
8.Contact tank
processes
1.Intake
2.Screening
3.Pretreatment
4.Chemical Mixing
5.Coagulation and Flocculation
6.Clarification
7.Filtration
8.Contact tank
0. Intake
River intake, Sungai
Semenyih, Bukit
Tampoi
River intake, Sungai
Semenyih, Bukit
Tampoi
0. Intake
River intake
River intake
0. Intake
Dam intake, Air Itam
Dam intake, Air Itam
0. Intake
Sungai Dua, Penang
Sungai Dua, Penang
1. Screening
to remove of debris and part of
the sediment load.
Coarse Screens (Bar Screens):
Remove large suspended
or floating materials.
Made of metal bars (½ to ¾
inch thick) with 1 to 3-inch
gaps.
Fine Screens:
Remove smaller materials
missed by coarse screens.
Openings around 3/8 inch.
to remove of debris and part of
the sediment load.
Coarse Screens (Bar Screens):
Remove large suspended
or floating materials.
Made of metal bars (½ to ¾
inch thick) with 1 to 3-inch
gaps.
Fine Screens:
Remove smaller materials
missed by coarse screens.
Openings around 3/8 inch.
2. Pretreatment
1.Pre sedimentation
Remove suspended and colloidal
materials from raw water before main
treatment.
Done in a bunded storage reservoir or
purpose-built tank.
Effectiveness depends on retention time
Longer retention time → More solids settle
out.
2.Ph adjustment:
Needed for raw water with high or low pH.
Low pH water is common in rivers flowing
through peaty areas. High pH Water is
rare.
Method: Add lime or soda ash to raise pH.
Ensures optimal conditions for chemical
reaction.
1.Pre sedimentation
Remove suspended and colloidal
materials from raw water before main
treatment.
Done in a bunded storage reservoir or
purpose-built tank.
Effectiveness depends on retention time
Longer retention time → More solids settle
out.
2.Ph adjustment:
Needed for raw water with high or low pH.
Low pH water is common in rivers flowing
through peaty areas. High pH Water is
rare.
Method: Add lime or soda ash to raise pH.
Ensures optimal conditions for chemical
reaction.
Pretreatment
3.Oxidation
To reduce taste and odour-causing compounds,
To control algae growth in treatment plant structures
Two form of oxidations:
A)Aeration
B)Chemical oxidation
3.Oxidation
To reduce taste and odour-causing compounds,
To control algae growth in treatment plant structures
Two form of oxidations:
A)Aeration
B)Chemical oxidation
A. Aeration
Aeration is commonly applied in WTPs in Malaysia.
Aeration involves bringing air or other gases in contact with water
Reduce the concentration of taste and odour from hydrogen sulphide
Oxidise iron and manganese (from soluble form to solid form)
Fe + O2 + H2O → Fe(OH)+ H
Increase the dissolved oxygen
Decrease the carbon dioxide reducing its corrosiveness and raise its pH
Aeration is commonly applied in WTPs in Malaysia.
Aeration involves bringing air or other gases in contact with water
Reduce the concentration of taste and odour from hydrogen sulphide
Oxidise iron and manganese (from soluble form to solid form)
Fe + O2 + H2O → Fe(OH)+ H
Increase the dissolved oxygen
Decrease the carbon dioxide reducing its corrosiveness and raise its pH
Aeration
Methods
Water into air aeration –produce
small drops of water that fall
through air (cascade)
Air into water aeration –create
small bubbles of air that rise
through the water being aerated
(diffuser).
Methods
Water into air aeration –produce
small drops of water that fall
through air (cascade)
Air into water aeration –create
small bubbles of air that rise
through the water being aerated
(diffuser).
B. Chemical Oxidation
Chemical oxidants typically used are :
potassium permanganate -liquid
Chlorine -gas
chlorine dioxide -liquid
Ozone -gas
Chemical oxidants typically used are :
potassium permanganate -liquid
Chlorine -gas
chlorine dioxide -liquid
Ozone -gas
3. Chemical Mixing
A major form of treatment of raw water is from the use of chemicals.
For the chemical processes to work effectively and efficiently, it is necessary
to ensure that the chemicals are properly mixed into the water.
The physical process mixing is needed so chemicals are distributed evenly
throughout the water.
a)Mechanical mixing
b)Hydraulic mixing
c)Air mixing
A major form of treatment of raw water is from the use of chemicals.
For the chemical processes to work effectively and efficiently, it is necessary
to ensure that the chemicals are properly mixed into the water.
The physical process mixing is needed so chemicals are distributed evenly
throughout the water.
a)Mechanical mixing
b)Hydraulic mixing
c)Air mixing
a. Mechanical
mixing
Most Common Method
Mechanical mixing using
propeller or paddle-type
mixers.
Mixers are placed in a water
tank where rapid mixing
occurs.
Reaction time (typically 30 to
60 seconds.
mixing
Most Common Method
Mechanical mixing using
propeller or paddle-type
mixers.
Mixers are placed in a water
tank where rapid mixing
occurs.
Reaction time (typically 30 to
60 seconds.
b. Hydraulic mixing
Hydraulic mixing can be
achieved by using:
weirs, flumes, orifices, baffled
chambers, valves or even
simple turbulence caused by
the velocity in a pipe or
conduit.
Hydraulic mixing can be
achieved by using:
weirs, flumes, orifices, baffled
chambers, valves or even
simple turbulence caused by
the velocity in a pipe or
conduit.
c. Air mixing
Air mixing is the injection of
compressed air bubbles to
promote the mixing of
contents of an entire tank
Air mixing is the injection of
compressed air bubbles to
promote the mixing of
contents of an entire tank
4. Coagulant
Source waters in Malaysia particularly
from rivers, usually contain amounts of
dissolved and suspended solids.
Some of these large suspended particles
such as sand can easily be removed by
sedimentation and filtration processes.
However smaller particles that may be in
colloidal form (clay) and soluble materials
are not as easily removed.
This colloid require chemical and
physical conditioning to remove
them
Source waters in Malaysia particularly
from rivers, usually contain amounts of
dissolved and suspended solids.
Some of these large suspended particles
such as sand can easily be removed by
sedimentation and filtration processes.
However smaller particles that may be in
colloidal form (clay) and soluble materials
are not as easily removed.
This colloid require chemical and
physical conditioning to remove
them
Chemical conditioning
Involves adding chemicals to alter the water chemical properties.
Clay particles in water have a negative charge, so they repel each other and stay
suspended.
Coagulants are added to the water and release positively charged ions.
These positive ions attach to the negative particles, neutralizing their charge.
Once neutralized, the particles stick together, forming larger clumps called flocs.
The flocs become heavy settled.
Common Coagulants Used in Water Treatment Plants (WTPs)
Aluminium sulphate
Polyaluminiumchloride
Ferric chloride
Ferric sulphate
Aluminium chlorohydrate
Involves adding chemicals to alter the water chemical properties.
Clay particles in water have a negative charge, so they repel each other and stay
suspended.
Coagulants are added to the water and release positively charged ions.
These positive ions attach to the negative particles, neutralizing their charge.
Once neutralized, the particles stick together, forming larger clumps called flocs.
The flocs become heavy settled.
Common Coagulants Used in Water Treatment Plants (WTPs)
Aluminium sulphate
Polyaluminiumchloride
Ferric chloride
Ferric sulphate
Aluminium chlorohydrate
5. Flocculation
A physical process that follows after coagulation, to transform
smaller flocs into larger flocs through slow, gentle mixing.
Mixing must be gentle to avoid breaking fragile flocs as they grow.
Conducted in a tank under controlled mixing.
Type:
a)Baffled tank flocculator
b)Mechanical flocculator
c)Plug flow flocculator
A physical process that follows after coagulation, to transform
smaller flocs into larger flocs through slow, gentle mixing.
Mixing must be gentle to avoid breaking fragile flocs as they grow.
Conducted in a tank under controlled mixing.
Type:
a)Baffled tank flocculator
b)Mechanical flocculator
c)Plug flow flocculator
a. Baffled tank
flocculator
Baffled tank flocculator is a form
of hydraulic flocculator that is
simple and effective at constant
flows.
Energy is added to the water as it
flows forcibly around baffles.
Higher flow rate → Greater mixing
intensity.
flocculator
Baffled tank flocculator is a form
of hydraulic flocculator that is
simple and effective at constant
flows.
Energy is added to the water as it
flows forcibly around baffles.
Higher flow rate → Greater mixing
intensity.
b.
Mechanical
flocculator
A mechanical flocculator is an electrically
powered device with adjustable speed and
low energy loss.
Two types:
Vertical flocculator in square tank. Easy operate
and maintenance
Horizontal flocculator in long rectangular tank for
high rate settling
Mechanical
flocculator
A mechanical flocculator is an electrically
powered device with adjustable speed and
low energy loss.
Two types:
Vertical flocculator in square tank. Easy operate
and maintenance
Horizontal flocculator in long rectangular tank for
high rate settling
Vertical
flocculator
Vertical flocculator in square tank.
Easy operate and maintenance
flocculator
Vertical flocculator in square tank.
Easy operate and maintenance
Horizontal
flocculator
Horizontal flocculator in long
rectangular tank for high rate
settling
flocculator
Horizontal flocculator in long
rectangular tank for high rate
settling
c. Plug Flow Reactor
A pipe flocculator (or plug-
flow reactor) is a long,
serpentine piping system that
provides constant mixing
energy and retention time,
ensuring even mixing of
particles to create uniform
flocs with excellent separation
properties.
A pipe flocculator (or plug-
flow reactor) is a long,
serpentine piping system that
provides constant mixing
energy and retention time,
ensuring even mixing of
particles to create uniform
flocs with excellent separation
properties.
6. Clarification
The purpose of the clarification process is to reduce the solids
content in the water after coagulation and flocculation.
Floc will be removed in the clarification tank.
Conventional clarifiers are in a rectangular, square or round tank.
The tanks need to be designed to allows the water to flow slowly,
with minimum turbulence at the entry and exit points.
The residual solids that accumulate at the bottom of the basin, must
be periodically removed.
The purpose of the clarification process is to reduce the solids
content in the water after coagulation and flocculation.
Floc will be removed in the clarification tank.
Conventional clarifiers are in a rectangular, square or round tank.
The tanks need to be designed to allows the water to flow slowly,
with minimum turbulence at the entry and exit points.
The residual solids that accumulate at the bottom of the basin, must
be periodically removed.
Rectangular clarifier (most common)
are usually constructed in concrete and designed for flow parallel to the basin’s
length.
Design Considerations -Flow should be evenly distributed across the width to minimize
currents and eddies that could disrupt settling.
The bottom of the basin slopes slightly at the inlet to facilitate easier removal of solids.
Shape & Size -Basins are typically long and narrow, with width-to-length ratios
between 3:1 to 5:1.
Basin depths range from 3 to 4.5 meters.
At least two basins are required: one for operation and one for inspection/cleaning.
Basins are often placed side by side, sharing a common wall for cost-effectiveness.
are usually constructed in concrete and designed for flow parallel to the basin’s
length.
Design Considerations -Flow should be evenly distributed across the width to minimize
currents and eddies that could disrupt settling.
The bottom of the basin slopes slightly at the inlet to facilitate easier removal of solids.
Shape & Size -Basins are typically long and narrow, with width-to-length ratios
between 3:1 to 5:1.
Basin depths range from 3 to 4.5 meters.
At least two basins are required: one for operation and one for inspection/cleaning.
Basins are often placed side by side, sharing a common wall for cost-effectiveness.
Rectangular clarifier
(most common)
(most common)
Circular clarifier
The water flows radially from the centre to the outside
The water flows radially from the centre to the outside
7. Filtration
The water that still have some fine suspended matter which cannot
be removed during the clarification process.
Filtration is the removal of residual suspended matter that may
interfere with disinfection.
The media commonly used in filtration are sand, anthracite coal,
granular activated carbon, or some combination of these materials.
The mechanism of the filtration
straining where the suspended matter is trapped between the grains of
filter media
adsorption where the suspended materials stick to the surface of the
individual media grains or on previously deposited material.
The water that still have some fine suspended matter which cannot
be removed during the clarification process.
Filtration is the removal of residual suspended matter that may
interfere with disinfection.
The media commonly used in filtration are sand, anthracite coal,
granular activated carbon, or some combination of these materials.
The mechanism of the filtration
straining where the suspended matter is trapped between the grains of
filter media
adsorption where the suspended materials stick to the surface of the
individual media grains or on previously deposited material.
7. Filtration
Filters can be classified either as gravity or pressure filters.
gravity filters use gravitational forces to move the water through the filter
pressure filters, applied pressure forces the water through the filter.
Typically, gravity filters are more commonly used in water treatment.
a.Slow sand filters
b.Rapid gravity sand filters
c.Rapid pressure sand filters
d.Membrane filters
Filters can be classified either as gravity or pressure filters.
gravity filters use gravitational forces to move the water through the filter
pressure filters, applied pressure forces the water through the filter.
Typically, gravity filters are more commonly used in water treatment.
a.Slow sand filters
b.Rapid gravity sand filters
c.Rapid pressure sand filters
d.Membrane filters
8. Disinfection
Disinfection is to remove or inactivates bacteria, viruses, protozoa
and other forms of pathogenic micro-organisms in the water.
Chemicals typically used for disinfection are strong oxidants such as
a)chlorine and chlorine compounds
b)ozone
c)UV radiation.
Disinfection is to remove or inactivates bacteria, viruses, protozoa
and other forms of pathogenic micro-organisms in the water.
Chemicals typically used for disinfection are strong oxidants such as
a)chlorine and chlorine compounds
b)ozone
c)UV radiation.
a. chlorination
Chlorine dissociates in water to form hypochlorous acid and
hypochlorite ions. They are toxic to micro-organisms.
Besides disinfection, chlorine is also useful for
oxidizing iron
manganese
hydrogen sulphide
controlling taste and odour, algae and slime.
Chlorine is available in gaseous, liquid and solid forms. The most
common are Chlorine as Cl2; Sodium hypochlorite, NaOCl, and
Calcium hypochlorite Ca(OCl)2.
Chlorine dissociates in water to form hypochlorous acid and
hypochlorite ions. They are toxic to micro-organisms.
Besides disinfection, chlorine is also useful for
oxidizing iron
manganese
hydrogen sulphide
controlling taste and odour, algae and slime.
Chlorine is available in gaseous, liquid and solid forms. The most
common are Chlorine as Cl2; Sodium hypochlorite, NaOCl, and
Calcium hypochlorite Ca(OCl)2.
b. Ozone oxidation
Ozone (O₃) is a powerful oxidant. Ozone is an unstable gas
composed of three oxygen atoms. It can break down into oxygen
(O₂) and a highly reactive oxygen atom (O).
When in contact with microorganisms, it breaks down their cell walls
by oxidizing vital components like proteins, enzymes, and lipids.
Ozonation systems require high capital cost; the operating cost is
about 10 to 15 times higher than the cost of chlorine)
Ozone (O₃) is a powerful oxidant. Ozone is an unstable gas
composed of three oxygen atoms. It can break down into oxygen
(O₂) and a highly reactive oxygen atom (O).
When in contact with microorganisms, it breaks down their cell walls
by oxidizing vital components like proteins, enzymes, and lipids.
Ozonation systems require high capital cost; the operating cost is
about 10 to 15 times higher than the cost of chlorine)
c. Ultraviolet (UV) radiation
Ultraviolet (UV) irradiation inactivates micro-organisms by damaging its cellular
nucleic acids.
When UV energy is applied, it is absorbed by the genetic material (DNA) of
microorganisms where structural changes are induced thereby preventing further
propagation of the organism.
The peak absorption is between 250 to 265 nm, which is the optimum wavelength
range for germicidal effectiveness.
The advantages : contact time required is short.
Ultraviolet (UV) irradiation inactivates micro-organisms by damaging its cellular
nucleic acids.
When UV energy is applied, it is absorbed by the genetic material (DNA) of
microorganisms where structural changes are induced thereby preventing further
propagation of the organism.
The peak absorption is between 250 to 265 nm, which is the optimum wavelength
range for germicidal effectiveness.
The advantages : contact time required is short.
Ultraviolet (UV) radiation
The disadvantage : not effective in the inactivation of spores, cysts and viruses.
water needs to be well treated prior to UV application otherwise the radiation
may be absorbed by many other constituents that are found in the water, or if
the water is high in suspended solids, the micro-organisms may be shielded from
the UV
The equipment is still expensive; power requirement is high and maintenance is
also expensive when replacements of the UV lamps are necessary.
As a result, the application of UV for disinfection is still limited in the treatment of
drinking water
The disadvantage : not effective in the inactivation of spores, cysts and viruses.
water needs to be well treated prior to UV application otherwise the radiation
may be absorbed by many other constituents that are found in the water, or if
the water is high in suspended solids, the micro-organisms may be shielded from
the UV
The equipment is still expensive; power requirement is high and maintenance is
also expensive when replacements of the UV lamps are necessary.
As a result, the application of UV for disinfection is still limited in the treatment of
drinking water
9. Contact and Clear Water Tank
The main purpose is to provide the necessary contact time for the
disinfecting agent to achieve the degree of inactivation before the
water is considered safe to supply to the consumers.
Typically, if chlorine is used for disinfection, the contact tank will be
30 minutes.
Often, the final pH correction is also carried out in the contact tank
The clear water tank is required to provide the storage buffer
against variations in water demands, as well as to be able to have
sufficient water for all the plant services such as filter backwashing,
firefighting and general service water for the plant usage for
cleaning and chemical preparation.
The main purpose is to provide the necessary contact time for the
disinfecting agent to achieve the degree of inactivation before the
water is considered safe to supply to the consumers.
Typically, if chlorine is used for disinfection, the contact tank will be
30 minutes.
Often, the final pH correction is also carried out in the contact tank
The clear water tank is required to provide the storage buffer
against variations in water demands, as well as to be able to have
sufficient water for all the plant services such as filter backwashing,
firefighting and general service water for the plant usage for
cleaning and chemical preparation.
10. pH correction and protection
Before treated water is sent to the distribution system, its pH must be adjusted to stabilize it
and prevent two major issues:
1.Corrosive Water (low pH): Dissolves minerals (like calcium and magnesium) and harmful
metals (e.g., lead, copper) from pipes, which affects water quality and damages the
distribution system.
Solution: Raise the pH using chemicals such Hydrated lime (Ca(OH)₂), Soda ash
(Na₂CO₃), Sodium bicarbonate (NaHCO₃), Caustic soda (NaOH)
2.Scaling Water (high pH): Deposits minerals (e.g., calcium carbonate) on pipes, which can
reduce corrosion but cause clogs or appliance damage if scaling is excessive.
Solution: Lower pH using Re-carbonation by add carbon dioxide (CO₂) to reduce pH.
In Malaysia, most water is soft and corrosive (pH <7, low hardness, low alkalinity), so pH
correction focuses on preventing corrosion rather than controlling scaling.
Before treated water is sent to the distribution system, its pH must be adjusted to stabilize it
and prevent two major issues:
1.Corrosive Water (low pH): Dissolves minerals (like calcium and magnesium) and harmful
metals (e.g., lead, copper) from pipes, which affects water quality and damages the
distribution system.
Solution: Raise the pH using chemicals such Hydrated lime (Ca(OH)₂), Soda ash
(Na₂CO₃), Sodium bicarbonate (NaHCO₃), Caustic soda (NaOH)
2.Scaling Water (high pH): Deposits minerals (e.g., calcium carbonate) on pipes, which can
reduce corrosion but cause clogs or appliance damage if scaling is excessive.
Solution: Lower pH using Re-carbonation by add carbon dioxide (CO₂) to reduce pH.
In Malaysia, most water is soft and corrosive (pH <7, low hardness, low alkalinity), so pH
correction focuses on preventing corrosion rather than controlling scaling.
11. Fluoridation
Fluoridation is not a treatment process but is required to meet Ministry of
Health (MOH) Malaysia standards.
Dosage of fluoride levels in treated water are maintained between 0.4 to
0.6 mg/L.
Provides protection against dental cavities, especially in children.
Safe Levels:
1 mg/L: Effective for dental protection.
>2 mg/L: May cause tooth discolouration.
>5 mg/L: Can lead to brittle teeth, fluorosis, or skeletal abnormalities.
Fluoridation is not a treatment process but is required to meet Ministry of
Health (MOH) Malaysia standards.
Dosage of fluoride levels in treated water are maintained between 0.4 to
0.6 mg/L.
Provides protection against dental cavities, especially in children.
Safe Levels:
1 mg/L: Effective for dental protection.
>2 mg/L: May cause tooth discolouration.
>5 mg/L: Can lead to brittle teeth, fluorosis, or skeletal abnormalities.
THE END
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