water treatment technology (tas 3010) lecture notes 9a -water intake, screening, aeration,...
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WATER TREATMENT TECHNOLOGY (TAS 3010) LECTURE NOTESUNIVERSITY MALAYSIA TERENGGANU 2009Disclaimer: I don't own this file. If you believe you do, and you don't want it to be published here, please let me know. I will remove it immediatelyTRANSCRIPT
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT© SHAHRUL ISMAIL, DESc.University College of Science and Technology Malaysia
CHAPTER 3:Environmental Microbiology
CHAPTER 9a : CHAPTER 9a : CHAPTER 9a : CHAPTER 9a :
TAS 3101 : WATER TREATMENT TECHNOLOGY
Water Treatment Water Treatment
Process :Process :
Water Treatment Water Treatment
Process :Process :
Water Intake, Water Intake,
Screening, Screening,
Aeration, CoagulationAeration, Coagulation
Water Intake, Water Intake,
Screening, Screening,
Aeration, CoagulationAeration, Coagulation
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Menu
1) Introduction
2) Water Intake
3) Water Treatment Process
4) Screening
5) Pre-Sedimentation
6) Aeration
7) Coagulation
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Characteristic from surface sources - unsuitable for human
consumption, industrial use, commercial use etc.
Characteristics :
1) Turbid
2) Colour
3) Acids, salts and gases – corrosive action – impart hardness of
water
4) Bacteria – Water borne diseases.
Introduction
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Objectives :
“ To remove harmful microorganisms or chemicals, thereby preventing the
spread of disease in order to supply clean and safe water for public demand”
Good water source :
Raw water with a coliform count of up to 5000/100mL and turbidity up to 10
units
Poor water source :
Raw water with coliform counts that frequently exceed 20,000/100 mL and
turbidities that exceed 250 units.
Objectives
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Content must be removed from the water
source
Waste
Solid material / Colloidal particles
Pathogen
Heavy Metal
Exceed dissolved salt
Water Treatment - Pollutant
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
FACTORS CONTRIBUTE TO THE SELECTION
OF TREATMENT METHOD :
Sources of water intake
Characteristic of water
Cost
Water Treatment – Selection
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
SELECTION CRITERIA FOR WATER INTAKE LOCATION :
Must have the best available water quality
Far from strong current – adverse affect water intake
potential
Quantity of water demand can be achieved even at a
very low water flow rate
Near to water treatment plant
Easily accessible & possess adequate space and facilities
for maintenance works
1 – Water Intake
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
SOURCES OF WATER INTAKE :
SURFACE WATER : Particle Removal
GROUNDWATER : Removal of dissolved inorganic
contaminants
WATER STORAGE
- High content of Fe & Mn
- Algal Bloom
1 – Water Intake Sources
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Typical treatment plant for surface water :
1) Screening and grit removal
2) Primary sedimentation (settling/clarification)
3) Coagulation (Rapid mixing)
4) Flocculation
5) Secondary sedimentation
6) Filtration
7) Sludge processing
8) Disinfection
Surface Water Treatment
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Surface Water Treatment
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Typical treatment plant for groundwater :
1) Aeration
2) Flocculation/precipitation
3) Sedimentation
4) Recarbonation
5) Filtration
6) Disinfection
7) Solids processing
Groundwater Treatment
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Groundwater Treatment
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Water IntakeWater Intake ScreeningScreening
FlocculationFlocculation
Pre-SedimentationPre-SedimentationAerationAeration
pH AdjustmentpH Adjustment
CoagulationCoagulation
SedimentationSedimentation
DistributionDistribution DisinfectionDisinfection
Pump HousePump House
Water Treatment – Process
Filtration Filtration
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Pipes design must take into account the
quantity of water to be sucked out
Pipes position must consider the water level
during dry season
Must be fenced for security purposes
Must have screens on pipe or intake
structure – prevent entry of objects that might
damage pumps and treatment facilities
Intake Structure
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
-Water from rivers may be stored in bankside
reservoir for periods between a few days – months to
allow natural biological purification.
-Provide buffer against short periods of drought or to
allow water supply to be maintained during transitory
pollution incidents in the source river.
-Blending water source.
Pump House - Storage
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Gate controls
Water Surface
Open Port
Closed port
Outlet
Entry Port
Tower Water Intake
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Tower Water Intake
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
-With grit removal, remove suspended debris, sand, grit, large
and hard floating huge and hard materials
- Settles very rapidly
- Prevent from damaging pumps & other mechanical devices
- Most deep groundwater does not need screening before
purification steps
Screening
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Traveling Water Screen
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
- Required if the raw water is too dirty.
- Store the raw water temporarily before proceed to the main
process.
- Removes the particles that will settle out by gravity alone
within few hours.
- Sedimentation basin/clarifier – circular/rectangular tank
holds water for suspended solids settlement.
- Equipped with bottom scraper and hopper that removes
collected sludge.
Pre-Sedimentation
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Purpose :
1) Eliminate unneeded dissolved gases
- Remove unpleasant taste and odour-causing substances
- Increase water pH.
- Remove substances that interfere with or add to the cost
of subsequent water treatment processess.
Aeration
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Purpose :
2) Increase DO level in water
- Oxidation of Fe2+ to Fe3+ and Mn2+ to Mn4+ respectively
- Increase the water freshness
3) Remove VOC
- Hazardous to public health e.g. gassoline elements
(benzine, xylene etc)
Aeration – Con’d
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Oxidation of Soluble Fe (II) and Mn (II) to insoluble Fe (III) and Mn (IV)
4Fe2+ + O2 + 10H2O 4Fe (OH)3 +
8H+
2Mn2+ + O2 + 2H2O 2MnO2 + 4H+
- Appromixately : 0.14 mg/L O2 will oxidise 1 mg/L Fe (II)
0.29 mg/L O2 will oxidise 1 mg/L Mn (II)
- Produce floc / settled Fe & Mn
Aeration – Mechanism
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
- The production of 1 meq/L H+ will destroy 1 meq/L alkalinity.
- If sufficient alkalinity is present, H+ ion concentration will increase
during the oxidation process – result in decrease water pH
- Effectiveness :
Depends on pH and the reaction time
- Chloride and Potassium Permanganate are also commonly used
oxidizing agent
- Physically, to force O2 to attached to one another. Therefore, Do
level is increased
- Water will settle as Fe (OH)3, indirectly Fe & Mn will be removed
Aeration – Mechanism
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
1)Cascade Aerator
2)Multiple Platform Aerator
3)Venturi Aerator
4)Draft-Tube Aerator
Objectives of all types of Aeration :
“ To maximize the area of contact between the water
and the air”
Aeration – Types
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Raw Water
Aerated Water
Cascade Aerator
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Water Basin
Platforms
Multiple Platform Aerator
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Perforated Pipe
Air Supply
ThroatVenturi
Aerated WaterRaw Water
Venturi Aerator
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Air
Raw Water
Sludge
Aerated Water
Draft Tube Aerator
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Aeration – Mechanism
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
1) Many of suspended water particles have a negative
electrical charge.
2) Coagulation eliminates natural electrical charge so they
attrack and stick to each other.
3) Form particles large enough to be removed by the
subsequent settling or filtration process
How ?
- Coagulant chemicals are added to water, rapid mixing ;
causing a reduction of the forces tend to keep particles
apart.
Coagulation
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
- Particles in water sources that contribute to colour and
turbidity
- Mainly clays, silts, viruses, bacteria, fulvic and humic acids
and organic particulates
- At pH levels above 4.0, particles or molecules are generally
negatively charged
- Have a very large ratio of surface area to volume
Coagulation – Colloidal Particles
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Factors Affecting Coagulation Process :
- Chemical Coagulant Dosage
- pH Adjustment
- Turbidity
4 - Coagulation
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Most commonly used coagulants :
Others :
Sodium aluminate
Chemicals Description
Alum (Aluminium Sulphate) Often used in conjuction with cationic polymers
Ferric Chloride May be more effective than alum in some application
Ferric Sulphate Effective in some waters and more economical in some location
Cationic Polymers Can be used alone as the primary coagulant or in conjunction with aluminium or iron coagulant
Coagulation - Chemicals
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
• Physical operation affecting coagulant dose efficiency.
• Chemical addition and quick/uniform mixing• Design criteria
– Detention time between 10 and 30 seconds– G, velocity gradient of 600 - 1000 s-1
– V < 8 m3
Rapid Mix- Basin
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
• Design liquid depth– 0.5 - 1.1 times basin diameter or width– 1.1 - 1.6 times basin diameter or width (dual
impeller)• Impeller diameter 0.3 - 0.5 times the tank
diameter or width• Baffles extend 10% of tank diameter or width
Rapid Mix- Basin – Con’d
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
to = V / Q
to = detention time, s
V = volume of the basin, m3
Q = flow into basin, m3/s
Rapid Mix- Basin Design
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
G = (P / V) ½
G = velocity gradient, s-1
P = power input, Watt or Nm/s or J/s
V = volume of water, m3
= dynamic viscosity, N.s/m2
Velocity Gradient, G
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
to
0.5 (in-line blending)
10 – 20
20 – 30
30 – 40
> 40
G
3,500
1,000
900
800
700
G values for rapid mixing
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
QUESTION :
A Water treatment plant designed for a flow 20, 000
m3/day is expected to use alum at a rate of 20 mg/l.
Determine the quantity of alum required for a month’s
supply?
Coagulant - Calculation
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
JAR TEST :
- Must be performed on each water is to be coagulated
- Must be repeated with each significant change in the
quality of a given water
- Used to calculate the quantity of coagulant to be used
in the water treatment plant.
- Jar Test equivalent to Chemical mixing, coagulation,
flocculation and sedimentation of unit processes in
WTP.
Coagulation – Jar Test
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Colourless
Odourless
Tasteless
No Suspended Solids
[BACK]
Clean Water
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
No pathogen microorganism
No dangerous organic/inorganic
Less mineral substances
[BACK]
Safe Water
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Purpose :
“ To provide a uniform
dispersion of coagulant
chemical throughout the
water influent “
[BACK]
Coagulation - Mixing