coagulation and flocculation at water treatment plants wqt 131 water works operation iii water...
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Coagulation and Flocculation at Water Treatment Plants
Coagulation and Flocculation at Water Treatment Plants
WQT 131Water Works Operation III
Water Treatment
Chapter 4 Coagulation and Flocculation
Lecture 3
WQT 131Water Works Operation III
Water Treatment
Chapter 4 Coagulation and Flocculation
Lecture 3
Week 3 Objectives Week 3 Objectives
• Understand conventional treatment to remove turbidity• Understand turbidity and its primary constituents• Explain coagulation chemistry• Understand mechanism of function involved in coagulant
aggregation• Explain flocculation chemistry• Understand mechanism of function involved in flocculent
aggregation• Understand the role of pH, alkalinity, turbidity,
temperature on coagulation and flocculation application
• Understand conventional treatment to remove turbidity• Understand turbidity and its primary constituents• Explain coagulation chemistry• Understand mechanism of function involved in coagulant
aggregation• Explain flocculation chemistry• Understand mechanism of function involved in flocculent
aggregation• Understand the role of pH, alkalinity, turbidity,
temperature on coagulation and flocculation application
Reading assignment: AWWA 2003. Water Treatment, Principles and Practices of Water Supply Operation, Third Edition, American Waterworks Association, ISBN 1-58321-230-2
Chapter 4 Coagulation and Flocculation
Reading assignment: AWWA 2003. Water Treatment, Principles and Practices of Water Supply Operation, Third Edition, American Waterworks Association, ISBN 1-58321-230-2
Chapter 4 Coagulation and Flocculation
Key WordsKey Words• Coagulation: adding and rapid mixing of chemicals to remove particles from
water. (flash mixing)
• Flocculation: adding and slow mixing of chemicals and particles to create flocs that settle out of water.
• Turbidity: suspended, dissolved, and colloidal particles in pretreated water that need to be removed to optimize treatment efficiency.
• Suspended Solids: particles held in suspension by the natural action of flowing waters.
• Colloidal Solids: fine silt that does not settle out of water but remain in suspension.
• Dissolved Solids: organic or inorganic molecules that are dissolved into the aqueous phase.
• Coagulation: adding and rapid mixing of chemicals to remove particles from water. (flash mixing)
• Flocculation: adding and slow mixing of chemicals and particles to create flocs that settle out of water.
• Turbidity: suspended, dissolved, and colloidal particles in pretreated water that need to be removed to optimize treatment efficiency.
• Suspended Solids: particles held in suspension by the natural action of flowing waters.
• Colloidal Solids: fine silt that does not settle out of water but remain in suspension.
• Dissolved Solids: organic or inorganic molecules that are dissolved into the aqueous phase.
Which of the following is the main purpose of the
coagulation/flocculation process?
Which of the following is the main purpose of the
coagulation/flocculation process?
a. t
o re
move
turb
idity
b. t
o softe
n th
e w
ater
c. t
o ad
d oxy
gen
d. t
o dis
infe
ct.
0% 0%0%0%
a. to remove turbidity
b. to soften the water
c. to add oxygen
d. to disinfect.
a. to remove turbidity
b. to soften the water
c. to add oxygen
d. to disinfect.
The most important raw water constituent for a surface water
plant is:
The most important raw water constituent for a surface water
plant is:
a. t
empe
ratu
re
b. h
ardne
ss
c. t
urbi
dity
d. p
H
0% 0%0%0%
a. temperature
b. hardness
c. turbidity
d. pH
a. temperature
b. hardness
c. turbidity
d. pH
WQT 131Water Works Operation III
Water Treatment
Chapter 4
WQT 131Water Works Operation III
Water Treatment
Chapter 4
Coagulation and Flocculation at Water
Treatment Plants
Coagulation and Flocculation at Water
Treatment Plants
“Ironically, it is easier to clean up dirty water than to make clean water cleaner. The reason is because particles must collide before they can stick together to make larger flocs. More
particles means more collisions.”
“Ironically, it is easier to clean up dirty water than to make clean water cleaner. The reason is because particles must collide before they can stick together to make larger flocs. More
particles means more collisions.”
Conventional Treatment Conventional Treatment • Conventional Treatment – common treatment steps used to remove turbidity from the initial source water.
1. Coagulation
2. Flocculation
3. Sedimentation
4. Filtration
• Conventional Treatment – common treatment steps used to remove turbidity from the initial source water.
1. Coagulation
2. Flocculation
3. Sedimentation
4. Filtration
Rapid MixingRapid Mixing
Slow MixingSlow Mixing
SettlingSettling
CleaningCleaning
Turbidity Turbidity • Turbidity – particles (sand, silt, clay, bacteria, viruses) in the initial source water that need to be removed to improve treatment. 1. Suspended Solids
2. Colloidal Solids (~0.1 to 1 m)
3. Dissolved Solids (<0.02 m)
• Turbidity – particles (sand, silt, clay, bacteria, viruses) in the initial source water that need to be removed to improve treatment. 1. Suspended Solids
2. Colloidal Solids (~0.1 to 1 m)
3. Dissolved Solids (<0.02 m)
331122
The turbidity of a water treatment plant effluent cannot be above?
The turbidity of a water treatment plant effluent cannot be above?
5 n
tu
1 n
tu
.5 n
tu
.3 n
tu
0% 0%0%0%
1. 5 ntu
2. 1 ntu
3. .5 ntu
4. .3 ntu
1. 5 ntu
2. 1 ntu
3. .5 ntu
4. .3 ntu
Turbidity Turbidity • Turbidity/Colloids– negative charged particles particles (sand, silt, clay, organic matter) in the initial source water that need to be removed to improve treatment.
• Turbidity/Colloids– negative charged particles particles (sand, silt, clay, organic matter) in the initial source water that need to be removed to improve treatment.
CoagulationCoagulation• Coagulants tend to be positively charged. •Due to their positive charge, they are attracted to the negative particles in the water•The combination of positive and negative charge results in a neutral , or lack, of charge •Van der Waal's forces refer to the tendency of particles in nature to attract each other weakly if they have no charge.
• Coagulants tend to be positively charged. •Due to their positive charge, they are attracted to the negative particles in the water•The combination of positive and negative charge results in a neutral , or lack, of charge •Van der Waal's forces refer to the tendency of particles in nature to attract each other weakly if they have no charge.
Settling ForcesSettling ForcesZeta Potential refers to the electrostatic potential generated by the accumulation of ions at the surface of the colloidal particle. It can help you understand and control colloidal suspensions
van der Waals Force- van der Waals forces are weak attractive forces that hold non-polar molecules together. They tends to pull molecules together and forms flocs.
Zeta Potential refers to the electrostatic potential generated by the accumulation of ions at the surface of the colloidal particle. It can help you understand and control colloidal suspensions
van der Waals Force- van der Waals forces are weak attractive forces that hold non-polar molecules together. They tends to pull molecules together and forms flocs.
Zeta potential analyzer
van der Waals in action
Settling ForcesSettling ForcesZeta Potential -is the electrical potential that exists at the "shear plane" of a particle, which is some small distance from its surface. Keeps particles apart and in suspension
Zeta Potential -is the electrical potential that exists at the "shear plane" of a particle, which is some small distance from its surface. Keeps particles apart and in suspension
Zeta Potential [mV] Stability behavior of the colloid
from 0 to ±5, Rapid coagulation or flocculation
Water Treatment CoagulantsWater Treatment Coagulants
Particles in water are negative; coagulants usually positively charged.
1. Alum- aluminum sulfate
2. Ferric chloride or ferrous sulfate
3. Polymers
Particles in water are negative; coagulants usually positively charged.
1. Alum- aluminum sulfate
2. Ferric chloride or ferrous sulfate
3. Polymers
What determines the optimum and most cost-effective amount
of a coagulant to use?:
What determines the optimum and most cost-effective amount
of a coagulant to use?:
Bey
ond th
at d
ose, i
t ...
Bel
ow th
at d
ose th
e ...
The
treat
men
t pla
nt ..
.
Div
ide
the
number
of .
..
0% 0%0%0%
1. Beyond that dose, it takes a very large increase in the amount of chemical to produce a small increase in turbidity removal
2. Below that dose the coagulant results in poor settling
3. The treatment plant budget4. Divide the number of
gallons of water in the coagulation tank by the nephelometric turbidity unit reading to determine the dosage in mg/L.
1. Beyond that dose, it takes a very large increase in the amount of chemical to produce a small increase in turbidity removal
2. Below that dose the coagulant results in poor settling
3. The treatment plant budget4. Divide the number of
gallons of water in the coagulation tank by the nephelometric turbidity unit reading to determine the dosage in mg/L.
Which is NOT a common method for determining optimum coagulant effectiveness?:
Which is NOT a common method for determining optimum coagulant effectiveness?:
Jar
test
Zet
a po
tentia
l det
ecto
r
Stre
amin
g curre
nt de.
..
Colo
rimet
ric m
etho
d
0% 0%0%0%
1. Jar test
2. Zeta potential detector
3. Streaming current detector
4. Colorimetric method
1. Jar test
2. Zeta potential detector
3. Streaming current detector
4. Colorimetric method
Water Treatment Coagulant AlumWater Treatment Coagulant AlumAlum- (aluminum sulfate)- particles suspended in natural, untreated water normally carry a negative electrical charge. These particles are attracted to the positive charges created by aluminum hydroxides. Dosage is generally around 25 mg/L.
1. Trivalent Al+3 charge attracts neg – particles2. Forms flocs of aluminum hydroxide (AlOH3).
3. Impacted by mixing, alkalinity, turbidity and temp.
4. Ideal pH range 5.8-8.5
Alum- (aluminum sulfate)- particles suspended in natural, untreated water normally carry a negative electrical charge. These particles are attracted to the positive charges created by aluminum hydroxides. Dosage is generally around 25 mg/L.
1. Trivalent Al+3 charge attracts neg – particles2. Forms flocs of aluminum hydroxide (AlOH3).
3. Impacted by mixing, alkalinity, turbidity and temp.
4. Ideal pH range 5.8-8.5
Alum CHEMISTRYAlum CHEMISTRYAlum- (aluminum sulfate)- made by dissolving aluminum hydroxide (bauxite or clay) in sulfuric acid
2Al(OH)3 + 3H2SO4 + 10H2O → Al2(SO4)3·16H2O
When ALUM is dissolved in alkaline water, it undergoes hydrolysis (reacts with water) to produce a high surface area gelatinous precipitate of aluminum hydroxide, Al(OH)3 (gibbsite)
(Al(OH)3 sticks the negatives.
When ALUM is reacted with water it hydrolyzes to
form aluminum hydroxide and dilute sulfuric acid (lowers pH). -----Need alkalinity adjustment
Alum- (aluminum sulfate)- made by dissolving aluminum hydroxide (bauxite or clay) in sulfuric acid
2Al(OH)3 + 3H2SO4 + 10H2O → Al2(SO4)3·16H2O
When ALUM is dissolved in alkaline water, it undergoes hydrolysis (reacts with water) to produce a high surface area gelatinous precipitate of aluminum hydroxide, Al(OH)3 (gibbsite)
(Al(OH)3 sticks the negatives.
When ALUM is reacted with water it hydrolyzes to
form aluminum hydroxide and dilute sulfuric acid (lowers pH). -----Need alkalinity adjustment
Alum CHEMISTRYAlum CHEMISTRYAlum- (aluminum sulfate)-
Al2(SO4)3·14H2O 2Al+3 +3SO4-2 +14H2O
2Al+3 + negatively charged colloids neutral surface charge
WHY IS ALKALINITY SO IMPORTANT??
2Al+3 + 6 HCO3- 2(Al(OH3)(S) + 6CO2
No bicarbonate (low alkalinity, low pH sulfuric acid!):
Al2(SO4)3·14H2O 2(Al(OH3) (S) +3H2SO4-2 +14H2O
Optimum pH: 5.5 to 6.5Operating pH: 5 to8
Alum- (aluminum sulfate)-Al2(SO4)3·14H2O 2Al+3 +3SO4
-2 +14H2O
2Al+3 + negatively charged colloids neutral surface charge
WHY IS ALKALINITY SO IMPORTANT??
2Al+3 + 6 HCO3- 2(Al(OH3)(S) + 6CO2
No bicarbonate (low alkalinity, low pH sulfuric acid!):
Al2(SO4)3·14H2O 2(Al(OH3) (S) +3H2SO4-2 +14H2O
Optimum pH: 5.5 to 6.5Operating pH: 5 to8
Alum MSDS Safety and HandlingAlum MSDS Safety and Handling
Alum- (aluminum sulfate)-Alum- (aluminum sulfate)-
Health Rating: 2 - Moderate Flammability Rating: 0 - None Reactivity Rating: 1 - Slight Contact Rating: 2 - Moderate Lab Protective Equip: GOGGLES; LAB COAT; VENT HOOD; PROPER GLOVES Storage Color Code: Green (General Storage)
Health Rating: 2 - Moderate Flammability Rating: 0 - None Reactivity Rating: 1 - Slight Contact Rating: 2 - Moderate Lab Protective Equip: GOGGLES; LAB COAT; VENT HOOD; PROPER GLOVES Storage Color Code: Green (General Storage)
Inhalation: Causes irritation to the respiratory tract. Ingestion: Causes nausea, vomiting and diarrhea. There have been two cases of fatal human poisonings from ingestion of 30 grams of alum. Skin Contact: Causes redness, itching, and pain. Eye Contact: Causes irritation, redness, and pain.
Inhalation: Causes irritation to the respiratory tract. Ingestion: Causes nausea, vomiting and diarrhea. There have been two cases of fatal human poisonings from ingestion of 30 grams of alum. Skin Contact: Causes redness, itching, and pain. Eye Contact: Causes irritation, redness, and pain.
When alum is added to water, a floc is formed from the
combination of alum and
When alum is added to water, a floc is formed from the
combination of alum and
a. a
lkal
inity
b. a
cid
c. c
hlorin
e
d. l
ime
0% 0%0%0%
a. alkalinity
b. acid
c. chlorine
d. lime
a. alkalinity
b. acid
c. chlorine
d. lime
The precipitate formed by coagulation with alum is
aluminum ________.
The precipitate formed by coagulation with alum is
aluminum ________.
Bic
arbonat
e
Car
bonate
Hyd
roxi
de
Sulfa
te
0% 0%0%0%
1. Bicarbonate
2. Carbonate
3. Hydroxide
4. Sulfate
1. Bicarbonate
2. Carbonate
3. Hydroxide
4. Sulfate
Adding Alum to water will cause the pH of the water to increase.Adding Alum to water will cause the pH of the water to increase.
Tru
e
Fal
se
0%0%
1. True
2. False
1. True
2. False
Alum comes in dry grade as a minimum of 17.5% pure product,
in liquid form it is 49% pure or 8.23% by weight Al2O3?
Alum comes in dry grade as a minimum of 17.5% pure product,
in liquid form it is 49% pure or 8.23% by weight Al2O3?
1. True
2. False
1. True
2. False
The coagulation process will most likely improve when:
The coagulation process will most likely improve when:
The
hardnes
s of
the
i...
The
tem
pera
ture
of t
h...
The
tem
pera
ture
of t
h...
The
alka
linity
of t
he in
...
11%0%
89%
0%
1. The hardness of the influent increases
2. The temperature of the influent decreases
3. The temperature of the influent increases
4. The alkalinity of the influent decreases
1. The hardness of the influent increases
2. The temperature of the influent decreases
3. The temperature of the influent increases
4. The alkalinity of the influent decreases
Water Treatment Coagulant Iron SaltWater Treatment Coagulant Iron Salt
Iron salt- (Iron chloride or sulfate)- particles suspended in natural, untreated water normally carry a negative electrical charge. These particles are attracted to the positive charges created by Fe(III) salts.
1. Trivalent Fe+3 charge attracts neg – particles2. Work over a larger pH range than alum3. Lower costs than alum4. Better removal of natural organics 5. Corrosive6. Special handling necessary7. Leave a residue of Fe in water (taste, stains)
Iron salt- (Iron chloride or sulfate)- particles suspended in natural, untreated water normally carry a negative electrical charge. These particles are attracted to the positive charges created by Fe(III) salts.
1. Trivalent Fe+3 charge attracts neg – particles2. Work over a larger pH range than alum3. Lower costs than alum4. Better removal of natural organics 5. Corrosive6. Special handling necessary7. Leave a residue of Fe in water (taste, stains)
Which one of the following chemicals would you most likely
use as a coagulant?:
Which one of the following chemicals would you most likely
use as a coagulant?:
Cat
ionic
pol
ymer
Sulfu
ric a
cid
Hyd
roch
loric
aci
d
Sodiu
m h
ydro
xide
100%
0%0%0%
1. Cationic polymer
2. Sulfuric acid
3. Hydrochloric acid
4. Sodium hydroxide
1. Cationic polymer
2. Sulfuric acid
3. Hydrochloric acid
4. Sodium hydroxide
A coagulant aid is a chemical added during coagulation to improve
coagulation; to build stronger, more settleable floc; to overcome the effects of temperature drops; to reduce the amount
of coagulant needed, and/or to reduce the amount of sludge produced. Which
of the following is not a type of coagulant aid:
A coagulant aid is a chemical added during coagulation to improve
coagulation; to build stronger, more settleable floc; to overcome the effects of temperature drops; to reduce the amount
of coagulant needed, and/or to reduce the amount of sludge produced. Which
of the following is not a type of coagulant aid:
Act
ivat
ed s
ilica
Gre
en s
and
Poly
elec
troly
tes
or p...
Wei
ghtin
g agen
ts
0% 0%0%
100%
1. Activated silica
2. Green sand
3. Polyelectrolytes or polymers
4. Weighting agents
1. Activated silica
2. Green sand
3. Polyelectrolytes or polymers
4. Weighting agents
A microfloc is a colloid that has reacted with a chemical
coagulant?
A microfloc is a colloid that has reacted with a chemical
coagulant?
Tru
e
Fal
se
11%
89%1. True
2. False
1. True
2. False
In determining the proper dosage of alum, the most useful
test is the _______ test:
In determining the proper dosage of alum, the most useful
test is the _______ test:
a. m
arbl
e
b. j
ar
c. c
arbona
te
d. p
H
9%0%0%
91%a. marble
b. jar
c. carbonate
d. pH
a. marble
b. jar
c. carbonate
d. pH
Alum added to turbid water containing alkalinity forms
_________, which increase in size and settle
out.
Alum added to turbid water containing alkalinity forms
_________, which increase in size and settle
out.
a. f
loc
partic
les
b. c
oagula
nts
c. c
oagula
nt a
ids
d. a
lum
inum
sulfa
te
89%
0%0%11%
a. floc particles
b. coagulants
c. coagulant aids
d. aluminum sulfate
a. floc particles
b. coagulants
c. coagulant aids
d. aluminum sulfate
Overcoming problems of cold-water floc can be corrected by
operating the process at the best pH for that water temperature,
increasing the coagulant dosage, or:
Overcoming problems of cold-water floc can be corrected by
operating the process at the best pH for that water temperature,
increasing the coagulant dosage, or:
Addin
g wei
ghtin
g ag
...
Per
form
ing th
e ja
r tes
t
Incr
easi
ng th
e num
b..
Incr
easi
ng th
e det
enti.
.
50%
40%
10%
0%
1. Adding weighting agents
2. Performing the jar test
3. Increasing the number and strength of floc particles
4. Increasing the detention time for floc formation
1. Adding weighting agents
2. Performing the jar test
3. Increasing the number and strength of floc particles
4. Increasing the detention time for floc formation
Which of the following conditions most affect
coagulation performance?
Which of the following conditions most affect
coagulation performance?
a. v
eloci
ty, c
hlorin
e ...
b. v
eloci
ty, w
ater
te...
c. w
ater
tem
perat
ure,..
.
d. d
eten
tion ti
me,
vel
...
0% 0%0%
100%a. velocity, chlorine dosage, detention time, and air temperature
b. velocity, water temperature, detention time and coagulant dosage
c. water temperature, detention time, air temperature, and chlorine dosage
d. detention time, velocity, air temperature, and chlorine dosage
a. velocity, chlorine dosage, detention time, and air temperature
b. velocity, water temperature, detention time and coagulant dosage
c. water temperature, detention time, air temperature, and chlorine dosage
d. detention time, velocity, air temperature, and chlorine dosage
With the coming of winter, the water temperature drops. A
likely operational problem at a filtration plant with coagulation
is:
With the coming of winter, the water temperature drops. A
likely operational problem at a filtration plant with coagulation
is:
Flo
c ca
rryo
ver f
rom
t..
Hig
h chlo
rine
resi
dual
Hig
h alk
alin
ity
Odor
100%
0%0%0%
1. Floc carryover from the sedimentation system
2. High chlorine residual
3. High alkalinity
4. Odor
1. Floc carryover from the sedimentation system
2. High chlorine residual
3. High alkalinity
4. Odor
Water Treatment Coagulant AidsWater Treatment Coagulant Aids
Activated silica (sodium silicate)- helps improve coagulation, decreases volume of coagulant necessary. Typically is sodium silicate.
1. secondary coagulant 2. reduces primary coagulants needed 3. Sodium silicate are alkaline
4. widens pH range for coagulation 5. used at 7-11% of alum
6. Heavier denser floc that settles faster 7. Can be formed on site
8. Corrosion inhibitor (forms a surface coating)
Activated silica (sodium silicate)- helps improve coagulation, decreases volume of coagulant necessary. Typically is sodium silicate.
1. secondary coagulant 2. reduces primary coagulants needed 3. Sodium silicate are alkaline
4. widens pH range for coagulation 5. used at 7-11% of alum
6. Heavier denser floc that settles faster 7. Can be formed on site
8. Corrosion inhibitor (forms a surface coating)
The three most commonly used coagulants in water treatment
are:
The three most commonly used coagulants in water treatment
are:
Alu
min
um h
ydro
xide,
...
Alu
min
um s
ulfate
, fer
r..
Lim
e, s
odiu
m h
ydro
xi...
Soda,
lim
e an
d chl
orin
e
33%
0%0%
67%
1. Aluminum hydroxide, lime and sodium hydroxide
2. Aluminum sulfate, ferric chloride, and ferrous sulfate
3. Lime, sodium hydroxide, and chlorine
4. Soda, lime and chlorine
1. Aluminum hydroxide, lime and sodium hydroxide
2. Aluminum sulfate, ferric chloride, and ferrous sulfate
3. Lime, sodium hydroxide, and chlorine
4. Soda, lime and chlorine
Water Treatment Coagulant AidsWater Treatment Coagulant Aids
Bentonite (clay)- helps improve coagulation, decreases volume of coagulant necessary.
1. high in color, low turbidity, low mineral content water 2. 10-50 mg/L dosage 3. Heavier denser floc that settles faster
Bentonite (clay)- helps improve coagulation, decreases volume of coagulant necessary.
1. high in color, low turbidity, low mineral content water 2. 10-50 mg/L dosage 3. Heavier denser floc that settles faster
Which of the following would most likely improve the coagulation/flocculation
process?
Which of the following would most likely improve the coagulation/flocculation
process?
a. i
ncre
ase
in ra
w w
at..
b. d
ecre
ase
in w
ater
...
c. i
ncre
ase
in w
ater
...
d. d
ecre
ase
in ra
w wa.
..
0% 0%
100%
0%
a. increase in raw water hardness
b. decrease in water temperature
c. increase in water temperature
d. decrease in raw water alkalinity
a. increase in raw water hardness
b. decrease in water temperature
c. increase in water temperature
d. decrease in raw water alkalinity
Water Treatment Coagulant AidsWater Treatment Coagulant AidsPolyelectrolytes- are water-soluble organic polymers
that are used as both primary coagulants and coagulant aids. Act as "bridges" between the already formed particles :
• Anionic—ionize in solution to form negative sites along the polymer molecule.
• Cationic—ionize to form positive sites.
• Non-ionic—very slight ionization.
• effectiveness: particles type, turbidity present, and the turbulence (mixing) available during coagulation.
Polyelectrolytes- are water-soluble organic polymers that are used as both primary coagulants and coagulant aids. Act as "bridges" between the already formed particles :
• Anionic—ionize in solution to form negative sites along the polymer molecule.
• Cationic—ionize to form positive sites.
• Non-ionic—very slight ionization.
• effectiveness: particles type, turbidity present, and the turbulence (mixing) available during coagulation.
Which one of the following chemicals would be most suitable as a filter aid?
Which one of the following chemicals would be most suitable as a filter aid?
a. a
lum
b. s
oda a
sh
c. s
odium
hyd
roxi
de
d. a
nionic
poly
mer
0%
100%
0%0%
a. alum
b. soda ash
c. sodium hydroxide
d. anionic polymer
a. alum
b. soda ash
c. sodium hydroxide
d. anionic polymer
A high molecular weight substance that is formed by either a natural or synthetic process. Can have either
positive or negative charge.
A high molecular weight substance that is formed by either a natural or synthetic process. Can have either
positive or negative charge.
Poly
mer
Pro
tein
Car
bohydra
te
Enzy
me
Deo
xyrib
onucl
eic
acid
100%
0% 0%0%0%
1. Polymer
2. Protein
3. Carbohydrate
4. Enzyme
5. Deoxyribonucleic acid
1. Polymer
2. Protein
3. Carbohydrate
4. Enzyme
5. Deoxyribonucleic acid
Water Treatment Coagulant/pHWater Treatment Coagulant/pHAlkalinity- Alkalinity is a measure of the buffering
capacity of water. These buffering materials are primarily the bases bicarbonate (HCO3
-), and carbonate (CO3
2-), and occasionally hydroxide (OH-), borates, silicates, phosphates, ammonium, sulfides, and organic ligands.
Chemicals applied to raise alkalinity
• Lime—CaOH2 accompanies alum or iron salt • Sodium bicarbonate- NaHCO3- raise alkalinity• Soda Ash—Na2CO3 -raise alkalinity• Caustic Soda—NaOH -raise alkalinity
Alkalinity- Alkalinity is a measure of the buffering capacity of water. These buffering materials are primarily the bases bicarbonate (HCO3
-), and carbonate (CO3
2-), and occasionally hydroxide (OH-), borates, silicates, phosphates, ammonium, sulfides, and organic ligands.
Chemicals applied to raise alkalinity
• Lime—CaOH2 accompanies alum or iron salt • Sodium bicarbonate- NaHCO3- raise alkalinity• Soda Ash—Na2CO3 -raise alkalinity• Caustic Soda—NaOH -raise alkalinity
Water Treatment WHO CoagulantsWater Treatment WHO CoagulantsName Advantages Disadvantages
Aluminum Sulfate (Alum) Al2(SO4)3.18H2O
Easy to handle and apply; most commonly used; produces less sludge than lime; most effective between pH 6.5 and 7.5
Adds dissolved solids (salts) to wa-ter; effective over a limited pH range.
Sodium Aluminate Na2Al2O4
Effective in hard waters; small dos-ages usually needed
Often used with alum; high cost; ineffective in soft waters
Polyaluminum Chloride (PAC) Al13(OH)20(SO4)2.Cl15
In some applications, floc formed is more dense and faster settling than alum
Not commonly used; little full scale data compared to other aluminum derivatives
Ferric Sulfate Fe2(SO4)3
Effective between pH 4–6 and 8.8–9.2
Adds dissolved solids (salts) to wa-ter; usually need to add alkalinity
Ferric Chloride FeCl3.6H2O
Effective between pH 4 and 11 Adds dissolved solids (salts) to wa-ter; consumes twice as much alka-linity as alum
Ferrous Sulfate (Copperas) FeSO4.7H2O
Not as pH sensitive as lime Adds dissolved solids (salts) to wa-ter; usually need to add alkalinity
Lime Ca(OH)2
Commonly used; very effective; may not add salts to effluent
Very pH dependent; produces large quantities of sludge; overdose can result in poor effluent quality
Optimum flocculation requires: Optimum flocculation requires:
a. v
iole
nt a
gitatio
n
b. g
entle
agita
tion
c. h
igh p
H
d. l
ow p
H
0% 0%0%
100%a. violent agitation
b. gentle agitation
c. high pH
d. low pH
a. violent agitation
b. gentle agitation
c. high pH
d. low pH
Agglomeration of colloidal and finely divided suspended matter
after coagulation by gentle mixing is called what?
Agglomeration of colloidal and finely divided suspended matter
after coagulation by gentle mixing is called what?
Flo
ccula
tion
Sed
imen
tatio
n
Poly
mer
acc
retio
n
Bal
last
ing
100%
0%0%0%
1. Flocculation
2. Sedimentation
3. Polymer accretion
4. Ballasting
1. Flocculation
2. Sedimentation
3. Polymer accretion
4. Ballasting
Which laboratory test is concerned with indicator
changes at pH 8.3 and about pH 4.5?
Which laboratory test is concerned with indicator
changes at pH 8.3 and about pH 4.5?
a. t
otal
har
dness
b. p
H
c. a
lkal
inity
d. t
otal c
hlorin
e re
sidual
0% 0%
100%
0%
a. total hardness
b. pH
c. alkalinity
d. total chlorine residual
a. total hardness
b. pH
c. alkalinity
d. total chlorine residual
_________ is the measure of how much acid can be added to a liquid, without causing a great
change in pH.
_________ is the measure of how much acid can be added to a liquid, without causing a great
change in pH.
Alk
alin
ity
Har
dness
pH
Aci
dity
80%
20%
0%0%
1. Alkalinity
2. Hardness
3. pH
4. Acidity
1. Alkalinity
2. Hardness
3. pH
4. Acidity
When operating a surface water plant, which laboratory tests are most significant for establishing
dosages for coagulation?
When operating a surface water plant, which laboratory tests are most significant for establishing
dosages for coagulation?
a. p
H and
alka
linity
b. s
ulfate
s
c. c
alci
um a
nd mag
...
d. t
otal h
ardnes
s
100%
0%0%0%
a. pH and alkalinity
b. sulfates
c. calcium and magnesium
d. total hardness
a. pH and alkalinity
b. sulfates
c. calcium and magnesium
d. total hardness
A test that is commonly performed to monitor the
treatment process is :
A test that is commonly performed to monitor the
treatment process is :
pH
Alk
alin
ity
Turb
idity
All
of the
above
0%
100%
0%0%
1. pH
2. Alkalinity
3. Turbidity
4. All of the above
1. pH
2. Alkalinity
3. Turbidity
4. All of the above
Tonight's Lecture Objectives: To understand coagulation
processes has been met?
Tonight's Lecture Objectives: To understand coagulation
processes has been met?
Stro
ngly Agree
Agree
Neutra
l
Disa
gree
Stro
ngly Disa
gree
78%
22%
0%0%0%
1. Strongly Agree
2. Agree
3. Neutral
4. Disagree
5. Strongly Disagree
1. Strongly Agree
2. Agree
3. Neutral
4. Disagree
5. Strongly Disagree