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.”

Water Treatment Water Treatment

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