2. Coagulation/Flocculation and Jar Testing
Department of Civil and Environmental Engineering
CEEN 330 – Environmental Field Session
Coagulation/Flocculation and Jar Testing

3. Overview Coagulation overview Calculations of dosing
Jar testing procedures
Turbidity measurement procedures
pH measurements
Review of Mn measurement procedures

4. Coagulation/Flocculation
Rapid mix
Flocculator

5. Turbidity in Water: Colloid Surface Phenomena
Electrostatic force
principal force contributing to stability of suspension
electrically charged particles
Van der Waals force
attraction between any two masses
opposing force to electrostatic forces

6. Double Layer Model of Colloidal Particles
Satisfy Electroneutrality

7. Forces Acting on Colloids
after Derjaguin, Landau, and Verwey, Overbeek who developed it in the 1940s

8. Destabilization Mechanisms
Compression of the double layer (DLVO Theory)
increasing the ionic strength

9. Compression of Double Layer

10. Destabilization Mechanisms
Compression of the double layer (DLVO Theory)
increasing the ionic strength
Adsorption and charge neutralization
adding a coagulant (metal salt)

11. Charge Neutralization

12. Destabilization Mechanisms
Compression of the double layer (DLVO Theory)
increasing the ionic strength
Adsorption and charge neutralization
adding a coagulant (metal salt)
Enmeshment in a precipitate (“sweep-floc coagulation”)
high coagulant dose (metal salt)
coagulant forms insoluble precipitates
dominant mechanism applied (pH 6-8)

13. Sweep-Floc Coagulation
Al2(SO4) 3 +

14. Sweep-Floc Coagulation
Al2(SO4) 3
Al2(SO4) 3 + +
colloids are enmeshed

15. Restabilization

16. Destabilization Mechanisms
Compression of the double layer (DLVO Theory)
increasing the ionic strength
Adsorption and charge neutralization
adding a coagulant (metal salt)
Enmeshment in a precipitate (“sweep-floc coagulation”)
high coagulant dose (metal salt)
coagulant forms insoluble precipitates
dominant mechanism applied (pH 6-8)
Interparticle bridging
synthetic organic polymer

17. Destabilization of Colloidal Particles
Metals salts used for destabilization:
aluminum sulfate (alum)
aluminum chloride
ferric sulfate
ferric chloride
ferrous sulfate

18. Coagulation Using Different Coagulants

19. Design of coagulation processes
The design of coagulation process involves:
Selection of proper coagulant chemicals and their dosing
Design of rapid mixing and flocculation basins
Coagulation (chemical conditioning)
Flocculation (physical conditioning)

20. Sedimentation

21. Sedimentation
Removal of largest particles for increased filtration run times
Achieves about 1-log removal (90%) of particles
Extra buffering for raw water upset
Required in treatment of many surface waters

22. Mechanism and Types of Sedimentation
Physical treatment process that utilizes gravity to separate solids from liquids
Types of sedimentation
Type I: discrete settling (i.e., settling of silt; pre-sedimentation)
Type II: flocculant settling (i.e., coagulated surface water)
Type III: hindered settling/zone settling (i.e., upper portion of sludge blanket in sludge thickener)
Type IV: compression settling (i.e., lower portion of a gravity sludge thickener)

23. Media Filtration Gravity filters: 2-3 m head
housed in open concrete or steel tanks
large and small systems
Pressure filters:
higher head
housed in closed steel vessels
costly; small systems

24. Granular Media Filtration Theory
Particles being captured can be 100-1,000 times smaller than the pores
Obviously not straining
Mechanisms of Filtration
Transport to the Media Surface
Attachment

25. Transport Mechanisms During Granular Media Filtration
Sedimentation
Interception
Brownian Diffusion A
Collector B C

26. Disinfection – Chlorine/ClO2

27. Regulations and Water Quality Standards
Federal Requirements
0.3 NTU (95%) not to exceed 1 (1.49)
Fe secondary maximum contaminant level: 0.3 mg/L
Mn secondary maximum contaminant level: mg/L
Complaints received when Mn is > mg/L
Golden WTP: Level III Partnership for Safe Water Quality
0.1 NTU (95%) (15 minute intervals)
Strict SOP’s for Operations
Stringent Reporting Guidelines
2nd plant in State, 7th in the Nation

28. Jar Testing
A laboratory procedure to determine the optimal pH and the optimum coagulant dose to achieve best turbidity removal and evaluate the removal of other constituents of interest (e.g., TOC, hardness, Mn2+)
Jar testing simulates the coagulation, flocculation, and sedimentation processes

29. Coagulant of Choice for the Current Field Session
The City of Golden uses Fe2(SO4)3 as a primary coagulant and PolyDADMAC as polymeric coagulation aid
For this field session we will chose from one of three coagulants:
aluminum sulfate (alum)
aluminum chloride
ferric sulfate

30. Common inorganic coagulants, coagulation aids,
133.3
AlCl3•6H2O g/mol
Common inorganic coagulants, coagulation aids,
and pH and Alkalinity Adjusting Chemicals

31. AlCl3·6 H2O + 3HCO3¯  Al(OH)3(am)+ 3CO2 + 6H2O + 3Cl ¯
Aluminum Chemistry
AlCl3·6 H2O + 3HCO3¯  Al(OH)3(am)+ 3CO2 + 6H2O + 3Cl ¯
1 mole of aluminum chloride consumes 3 moles of bicarbonate (HCO3-)
If alkalinity is not enough, pH will drop
Lime (CaO/Ca(OH)2) or soda ash (Na2CO3) may be needed to neutralize the acid

32. Exercise #1: Alkalinity Calculation
If 100 mg/L of aluminum chloride is to be added to achieve complete coagulation. How much alkalinity is consumed in mg/L as CaCO3?
AlCl3·6 H2O + 3HCO3¯  Al(OH)3(am)+ 3CO2 + 6H2O + 3Cl ¯
241.4 mg mg
241.4 mg aluminum chloride consumes 183 mg HCO3-
100 mg aluminum chloride will consume ((183/241.4) x 100) mg HCO3-
= 76 mg HCO3-
Alkalinity in mg/L as CaCO = 76 x (50/61)
= 62 mg/L as CaCO3 Al 27
g/mol Cl
35.5 H 1 C 12 O 16

33. Coagulation 25 °C

34. Mini-Pilot Flow Diagram
Constant
head pH
pH adjustment
Backwash
Waste
Chlorine
Coagulant
Flocculation Basin
Overflow
Mini-Pilot Flow Diagram
Feed
Tank
KMnO4
Turbidity meter
Backwash
Line
Turbidity meter

35. Exercise #1
For a typical Al3+ dose of 8 mg/L, determine the weight of AlCl3∙6H2O that will be added to every liter of water
A small water treatment system is operated continuously at 4 L/min. The maximum capacity of the dosing pump is 5 mL/min. If the maximum dose of Al3+ is 16 mg/L, what is the maximum concentration of hydrated AlCl3 in the stock feed solution?

36. Jar Testing – General Procedure
Fill six jars with raw water sample (1 Liter)
Place the jars under the jar testing apparatus and lower the mixers into the jars. Make sure the paddles will turn without scratching the sides of the jar.
Adjust water properties
Rapid mix at 200 rpm
Quickly (!) add the appropriate dose of coagulant to all jars
Continue rapid mixing for 1 minute
Reduce stirring speed to rpm and continue mixing for 20 minutes

37. Jar Testing – General Procedure
Turn off mixers after the 20 minutes flocculation step
Pull the mixers up and secure them (make sure they don’t touch the top of the holder)
Allow flocs to settle for 30 minutes
Draw 15 ml sample from each jar for turbidity measurement (s l o w l y and 1” below the surface)
Identify the jar with the lowest residual turbidity
Draw and filter samples for DOC analysis

38. Jar Testing – Determination of optimal pH
Fill six jars with raw water sample (1 Liter)
Adjust pH in the jars while mixing using H2SO4/HCl or NaOH/lime (pH: 5.5, 6.0, 6.5, 7.0, 7.5, 8.0)
Add same dose of the selected coagulant to each jar
Follow the next steps of the general procedure

39. The pH with the lowest residual turbidity will be the optimal pH…
For example….
Optimal pH: 6.3

40. Determination of Optimal Coagulant Dose
Repeat all previous preparation steps
This time adjust pH of all jars to optimal pH while mixing
Add different doses of the selected coagulant to the jars (coagulant dose: 10, 20, 30, 40, 50, 60 mg/L)
Follow the next steps of the general procedure

41. The jar with the lowest residual turbidity will determine the optimal coagulant dose…
Plot residual turbidity against coagulant dose
For example….
Coagulant Dose mg/L
Optimum coagulant dose: 12.5 mg/L

42. Teams’ Tasks This afternoon we will be working in groups
Group 1: ambient pH; dose optimization (Fe2(SO4)3
Group 2: ambient pH; dose optimization (Fe2(SO4)3; KMnO4 dose of 1.5 mg/L
Group 3: ambient pH; dose optimization (AlCl3)
Group 4: ambient pH; dose optimization (AlCl3); KMnO4 dose of 1.5 mg/L
Group 5: ambient pH; dose optimization (FeCl3)

43. Analysis
This afternoon we will bring ~20 gallons of river water for jar testing
The same water will be used for both jar testing and mini-pilot experiments on Tuesday, Wednesday, and Thursday
Measurements on feed water:
pH, Mn, turbidity, temperature, TOC
Measurements on jar-testing supernatant:
Turbidity, pH, Mn, and TOC on optimized dose

44. Turbidity Measurement
Make sure the test vials are clean before using them
Transfer approximately 10 ml of water sample into a test vial using a pipette
When collecting a sample from the jar of settled water, obtain the sample about 1” below the surface of the water
Calibrate the turbidimeter for the range in which the test water falls (the instrument itself will be pre-calibrated)
Wipe the sides and bottom of the test vial with a Kim-Wipes and place the sample in the turbidimeter
Cover the vial and read and record the results
Repeat as needed

45. Mn Measurement

46. Mn Measurement

47. Mn Measurement

48. pH Measurement You will be using portable pH meters
Make sure that the meters are calibrated and follow the calibration guidelines in the manual using pH 4, 7, and 10 buffers
Rinse the probe thoroughly with DI water between measurements and calibrations and gently dry the tip with Kim-Wipes before the next measurement
Make sure that the probe is stored in electrolyte solution or in wet environment if it is not in use

49. TOC Measurement You will collect samples in 17 ml vials
We will analyze the samples for you using a carbon analyzed (GE Sievers 5310 C)

50. Alkalinity and Hardness Measurement
Titration methods

51. Tuesday
We will meet in the labs at 8:00 am for start of experiments (please bring and hand-in the pre-lab and reports)
In the afternoon we will continue experiments and later in the evening we will gather in the classroom to present and share the experimental result

52. Teams Group 1 Group 2 Group 3 Group 4 Group 5 Group 6 Michelle
Bonfanti
Jess
Zielinski
Christopher Allan Waechter
Shaunta Oehlerking
Jordan
Partin
Emma
Ely
Sarah
Fischer
Stephen
Byers
Paige
Becker
Haley
Salzwedel
Travis
Ramos
Caroline
Ike
Kara
Davis
Richard Sebastian-Coleman
Olivia
Cain
Audra
Agajanian
Logan
Yamamoto
Frances
Marlin
Rosa
Foth
Brenna
Eads
Eric
Hake
Cameron
Colley-Holck
Isaac
Avila
Justin
Ripley
Marisa
LaRouche
Matthew
Greff
Dalton
Ellis
Jessica
Allen
Graham
Cottle
Dulguun
Tumurbat
Melissa
Mitton
Laura
Leonard
Xiojian
Guo
Hurley
Christopher
Marks
Neelha S. Mudigonda
Alejandra
Ruiz
Keegan
O'Day
Laila
Maksut

53. Group work Group 1 & 2: 25 g/L Fe2(SO4)3 stock solution
Calculate the required mL of stock solutions to achieve desired doses of coagulant in 2 L water sample
Generate a table:
Jar 1 2 3 4 5 6
Fe or Al dose (mg/L) 10 15 20 25
Required stock solution (mL)
Turbidity (NTU)
Group 1 & 2: 25 g/L Fe2(SO4)3 stock solution
Group 3 & 4: 25 g/L AlCl36H2O stock solution
Group 5: 25 g/L alum, Al2(SO4)314 H2O stock solution