Jar TestingCoagulation Dosage

Water Treatment Plants

Jar TestingCoagulation Dosage

Water Treatment PlantsWQT 134

Aquatic Chemistry II

Determining ALUM Coagulation Rates

WQT 134Aquatic Chemistry II

Determining ALUM Coagulation Rates

http://www.cee.vt.edu/ewr/environmental/teach/wtprimer/jartest/jartest.html

http://www.waterspecialists.biz/html/jar_test.html

Week 8 Objectives Week 8 Objectives

• Understand how to test pH, turbidity, and color on raw water sample

• Understand Jar Testing/Coagulation chemistry• Understand the role of pH, alkalinity, turbidity,

temperature on coagulation and flocculation application

• Understand how to test pH, turbidity, and color on raw water sample

• Understand Jar Testing/Coagulation chemistry• Understand the role of pH, alkalinity, turbidity,

temperature on coagulation and flocculation application

Reading assignment: Tech Brief: Jar Testing

Reading assignment: Tech Brief: Jar Testing

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.

• 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.

Jar Testing StepsJar Testing Steps• Fill the Phipps and Bird jar testing apparatus containers with

1000 ml of sample water. • Label each Beaker #1 add 1 liter of water =control, Beaker #2

add 2 ml of alum=2 mg/L, Beaker #3 add 5 ml of alum=5 mg/L, Beaker #4 add 10 ml of alum=10 mg/L, Beaker #5 add 15 ml of alum=15 mg/L, Beaker #6 add 20 ml of alum=20 mg/L

• Add the coagulant to each container and stir at approximately 100 rpm for 1 minute (record condition of flocs during rapid mix coagulation).

• Reduce the stirring speed to 25 to 35 rpm and continue mixing for 15 to 20 minutes(record condition of flocs every 5 minutes on data sheet below).

• Determine which coagulant dosage has the best flocculation time and the most floc settled out.

• Test the turbidity of the water in each beaker using a turbidimeter (record value on data sheet).

• Fill the Phipps and Bird jar testing apparatus containers with 1000 ml of sample water.

• Label each Beaker #1 add 1 liter of water =control, Beaker #2 add 2 ml of alum=2 mg/L, Beaker #3 add 5 ml of alum=5 mg/L, Beaker #4 add 10 ml of alum=10 mg/L, Beaker #5 add 15 ml of alum=15 mg/L, Beaker #6 add 20 ml of alum=20 mg/L

• Add the coagulant to each container and stir at approximately 100 rpm for 1 minute (record condition of flocs during rapid mix coagulation).

• Reduce the stirring speed to 25 to 35 rpm and continue mixing for 15 to 20 minutes(record condition of flocs every 5 minutes on data sheet below).

• Determine which coagulant dosage has the best flocculation time and the most floc settled out.

• Test the turbidity of the water in each beaker using a turbidimeter (record value on data sheet).

Jar Testing Experimental DesignJar Testing Experimental DesignAdd 1 liter of water Label each

Beaker #1 =control Beaker #2 add 2 ml of alum=2 mg/LBeaker #3 add 5 ml of alum=5 mg/L

Beaker #4 add 10 ml of alum=10 mg/L Beaker #5 add 15 ml of alum=15 mg/L Beaker #6 add 20 ml of alum=20 mg/L

Add 1 liter of water Label eachBeaker #1 =control

Beaker #2 add 2 ml of alum=2 mg/LBeaker #3 add 5 ml of alum=5 mg/L

Beaker #4 add 10 ml of alum=10 mg/L Beaker #5 add 15 ml of alum=15 mg/L Beaker #6 add 20 ml of alum=20 mg/L

#1 control

#1 control

#2 2 mg/L

#2 2 mg/L

#3 5mg/L

#3 5mg/L

#4 10 mg/L

#4 10 mg/L

#5 15 mg/L

#5 15 mg/L

#6 20 mg/L

#6 20 mg/L

Rapid mix 100 rpm for 1 minRecord floc conditions

Rapid mix 100 rpm for 1 minRecord floc conditions

Let settle for 10 minDetermine optimal coagulant dosage.

Record Turbidity on optimal coagulant dose

Let settle for 10 minDetermine optimal coagulant dosage.

Record Turbidity on optimal coagulant dose

Slow mix 25 rpm for 15 minRecord floc conditions every 5 min

Slow mix 25 rpm for 15 minRecord floc conditions every 5 min

Jar Testing ResultsJar Testing Results

• A hazy sample indicates poor coagulation.• Properly coagulated water contains floc particles

that are well-formed and dense, with the liquid between the particles clear.

• A hazy sample indicates poor coagulation.• Properly coagulated water contains floc particles

that are well-formed and dense, with the liquid between the particles clear.

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

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

A laboratory procedure for evaluating coagulation,

flocculation, and sedimentation is called what?

A laboratory procedure for evaluating coagulation,

flocculation, and sedimentation is called what?

Tem

perat

ure p

r...

Turb

idity

rem

o...

Tre

atab

ility

s...

Jar

test

ing

25% 25%25%25%1. Temperature profile

2. Turbidity removal efficiency

3. Treatability study

4. Jar testing

1. Temperature profile

2. Turbidity removal efficiency

3. Treatability study

4. Jar testing

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.”

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)

3311227 ntuRaw water

375 ntubackwash

0.02 ntuTreated

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

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. 

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

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

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

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

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