1. CLARIFIERS Prepared By Michigan Department of Environmental Quality
Operator Training and Certification Unit

2. Provide Quiescent Area
CLARIFIERS
Clarifiers
Sedimentation Basins
Settling Tanks
Provide Quiescent Area
Separation of Solids
Settleable
Floatable

3. Clarifiers Efficiency of Solids Removal Related To:
1. Characteristics of the Solids
2. Characteristics of the Water
3. Characteristics of the Clarifier

4. Stoke’s Law 2(p - po)g 9n (d/2)2 VF = VF = Fall Velocity
(p - po) = Density difference between
particle and water
n = viscosity of water
g = gravitational acceleration constant
d = diameter of the particle

5. Remember the Removal Efficiency Depends on Several Factors
Stoke’s Law
Forget the Formula
Remember the Removal Efficiency Depends on Several Factors
VF = Fall Velocity
(p - po) = Density difference between
particle and water
n = viscosity of water
g = gravitational acceleration constant
d = diameter of the particle

6. Particle Size versus Settling Timemm
Order of Size
Time to Settle
1.0
Coarse Sand
3 Seconds
0.1
Fine Sand
38 Seconds
0.01
Silt
33 Minutes
0.001
Bacteria
55 Hours
0.0001
Colloidal
230 Days
6.3 Years

7. Clarifiers Efficiency of Solids Removal Related To:
1. Characteristics of the Solids
2. Characteristics of the Water
3. Characteristics of the Clarifier

8. Remember the Removal Efficiency Depends on Several Factors
Stoke’s Law
Forget the Formula
Remember the Removal Efficiency Depends on Several Factors
VF = Fall Velocity
(p - po) = Density difference between
particle and water
n = viscosity of water
g = gravitational acceleration constant
d = diameter of the particle

9. Solids Settle More Readily in Warm Water
Settling Rate
Cold Water
More Dense
More Viscous
Warm Water
Less Dense
Less Viscous
Solids Settle More Readily in Warm Water
Than in Cold Water
Warm Water - Greater Efficiency of Clarification
Cool Water- Less Efficiency of Clarification

10. Clarifiers Efficiency of Solids Removal Related To:
1. Characteristics of the Solids
2. Characteristics of the Water
3. Characteristics of the Clarifier

11. Clarifiers Efficiency of Solids Removal Related To:
3. Characteristics of the Clarifier
Surface Area
Depth
Hydraulic Loading
Solids Loading

12. Clarifiers Efficiency of Solids Removal Related To:
3. Characteristics of the Clarifier
Surface Area
Depth
Hydraulic Loading
Solids Loading
Design
Operation
Maintenance

13. Clarifiers Efficiency of Solids Removal Related To:
3. Characteristics of the Clarifier
Flow Characteristics in the Clarifier
Flow Must be Dispersed Evenly Throughout

14. Clarifier Short Circuiting
Higher Flow (Horizontal Velocity) in One Part of Tank
Density Currents
Currents Within the Tank Carry Solids Through the Tank. 
Not the Same as Excessive Hydraulic Load
(Detention Time vs. Fall Velocity)

15. Clarifier Short Circuiting
Causes
Missing or poor influent baffling

16. Clarifier Short Circuiting
Causes
Missing or poor influent baffling

17. Clarifier Short Circuiting
Causes
Missing or poor influent baffling

18. Clarifier Short Circuiting
Causes
Uneven effluent weirs Plant growth or thrash in effluent weirs

19. Clarifier Short Circuiting
Causes
Temperature stratification between influent & clarifier water temperatures.

20. Clarifier Short Circuiting
Monitoring for Short Circuiting
Visual Observation
Flow Over Weir
Solids Over Weir

21. Clarifier Short Circuiting
Monitoring for Short Circuiting
Dye Testing

22. Clarifier Short Circuiting
Higher Flow (Horizontal Velocity) in One Part of Tank
Density Currents

23. Clarifier Short Circuiting
Causes
Missing or poor influent baffling
Uneven effluent weirs
Plant growth or thrash in effluent weirs
Temperature stratification between influent & clarifier water temperatures.

24. Clarifiers Efficiency of Solids Removal Related To:
1. Characteristics of the Solids
2. Characteristics of the Water
3. Characteristics of the Clarifier

25. Clarifiers Types of Clarifiers Inclined Plate Rectangular Circular
(Lamella)
Rectangular
Circular

26. Inclined Plate
(Lamella)

27. Types of Clarifiers – Inclined Plate (Lamella)
Distribution Orifice
Discharge Flumes
Feed Box
Overflow Box
Flocculation Tank
Flash
Mix Tank
Coagulant
Feed
Clarifier
Effluent
Clarifier
Influent
Inclined Plates
Sludge
Hopper
Sludge Discharge

28. Types of Clarifiers – Inclined Plate (Lamella)

29. Types of Clarifiers – Inclined Plate (Lamella)
Increased settling efficiency due to increased surface area
Smaller Area Needed for Installation

30. Types of Clarifiers – Inclined Plate (Lamella)
Increased settling efficiency due to increased surface area
Smaller Area Needed for Installation

31. Types of Clarifiers – Inclined Plate (Lamella)
Seldom Used With Organic Wastes
Biological Growths Reduce Efficiency
Mostly Industrial Applications

32. Rectangular
Clarifiers

33. Types of Clarifiers – Rectangular
Effluent
Weir
Drive
Unit
Inlet
Baffle
Scum
Trough
Effluent
Launder
Flights
Inlet
Drive
Gear
Idler
Sprockets
Drive
Chain
Sludge
Trough
Sludge Withdrawal
Pipe

34. Types of Clarifiers – Rectangular
Inlet
Baffle
Inlet

35. Types of Clarifiers – Rectangular
Influent baffling

36. Types of Clarifiers – Rectangular
Settleable
Floatable

37. Types of Clarifiers – Rectangular
Effluent
Weir
Effluent
Launder
Effluent

38. Types of Clarifiers – Rectangular
Settleable
Floatable

39. Types of Clarifiers – Rectangular
Solids Removal Mechanism
Rails

40. Types of Clarifiers – Rectangular
Drive
Unit
Drive
Gear
Idler
Sprockets
Drive
Chain

41. Types of Clarifiers – Rectangular
Flights

42. Types of Clarifiers – Rectangular
Flights
Rails

43. Types of Clarifiers – Rectangular
Wear Shoes
Rails

44. Types of Clarifiers – Rectangular
Wear Shoes
Rails
Prevent Wear on the Flights Where They Contact the Rails
Transfer Wear to the Shoe Instead of the Flights

45. Types of Clarifiers – Rectangular
Flights
Sludge
Sludge
Trough
Sludge Withdrawal
Pipe

46. Types of Clarifiers – Rectangular

47. Types of Clarifiers – Rectangular
Scum Removal
Scum
Trough
Flights
Scum

48. Types of Clarifiers – Rectangular
Scum Removal

49. Types of Clarifiers – Rectangular
Scum Removal

50. Types of Clarifiers – Rectangular
Effluent
Weir
Effluent
Launder
Effluent

51. Types of Clarifiers – Rectangular
Effluent Weir – “V Notch”
Flow = Velocity X Area

52. Types of Clarifiers – Rectangular
Effluent Weir – “V Notch”
Flow = Velocity X Area
As Flow Increases, Area Increases
And As Area Increases, Velocity Decreases

53. Types of Clarifiers – Rectangular
Effluent Weir – “V Notch”
Helps Keep Velocity Constant
Reduces Solids Build-up Behind Weir

54. Types of Clarifiers – Rectangular
Effluent Weirs
Single Weir
Finger Weirs

55. Types of Clarifiers – Rectangular
Effluent Weirs

56. Types of Clarifiers – Rectangular
Effluent
Weir
Drive
Unit
Inlet
Baffle
Scum
Trough
Effluent
Launder
Flights
Inlet
Drive
Gear
Idler
Sprockets
Drive
Chain
Sludge
Trough
Sludge Withdrawal
Pipe

57. Secondary Rectangular Clarifiers – Most Important
Monitor for Short Circuiting
Visual Observation
Flow Over Weir
Solids Over Weir
Dye Testing
Consider Baffles

58. Circular
Clarifiers

59. Circular Clarifier

60. Circular Clarifier
Influent typically enters the basin from the center rather than from one end. 

61. Circular Clarifier
Influent typically enters the basin from the center rather than from one end. 
Influent

62. A Circular Baffle Directs Flow
Circular Clarifier
A Circular Baffle Directs Flow 
Center Baffle
Influent

63. A Circular Baffle Directs Flow
Circular Clarifier
A Circular Baffle Directs Flow 

64. Circular Clarifier Solids Settle Scraped to Sump Removed by Pumping
Center Baffle
Influent
Sludge Plow
Sludge Sump

65. Circular Clarifier
Solids Settle
Scraped to Sump
Removed by Pumping 

66. Circular Clarifier
Solids Settle
Scraped to Sump
Removed by Pumping 

67. Drive Mechanism Also Drives Skimmer Arm to Remove Floating Scum
Circular Clarifier
Drive Mechanism Also Drives Skimmer Arm to Remove Floating Scum 
Scum
Baffle
Drive Unit
Skimmer Arm
Influent

68. Drive Mechanism Also Drives Skimmer Arm to Remove Floating Scum
Circular Clarifier
Drive Mechanism Also Drives Skimmer Arm to Remove Floating Scum 

69. Drive Mechanism Also Drives Skimmer Arm to Remove Floating Scum
Circular Clarifier
Drive Mechanism Also Drives Skimmer Arm to Remove Floating Scum 

70. Drive Mechanism Also Drives Skimmer Arm to Remove Floating Scum
Circular Clarifier
Drive Mechanism Also Drives Skimmer Arm to Remove Floating Scum 

71. Drive Mechanism Also Drives Skimmer Arm to Remove Floating Scum
Circular Clarifier
Drive Mechanism Also Drives Skimmer Arm to Remove Floating Scum 

72. Circular Clarifier
The Water Flows to the Effluent Weir Around the Circumference of the Clarifier 
Effluent Weir
Center Baffle
Influent
Sludge Plow
Sludge Sump

73. Circular Clarifier Outlet
Scum
Baffle
Effluent
Weir
Effluent
Launder
Effluent
Circular Clarifier Outlet

74. 1 2 3 The Launder and Weir May Be Outer Wall Inner Wall Suspended
Outer
Wall
Inner
Wall
Suspended
In Clarifier

75. Effluent Launder/Weir Inside Clarifier (#2) Can Create Water Current
Loss of solids over weir.
Baffles used to redirect & slow water currents.

76. Other Clarifier Baffles
STAMFORD BAFFLE
MC KINNEY BAFFLE

77. Clarifier Short Circuiting
Missing or poor effluent baffling
Uneven effluent weirs
Plant growth or thrash in effluent weirs
Temperature stratification between influent & clarifier water temperatures.

78. Clarifier
Variations

79. Circular Sludge Collection and Skimming
Clarifier Variations
Rectangular Tank
Circular Sludge Collection and Skimming
“Squirqular” Clarifier

80. Clarifier Variations
Peripheral Feed
Peripheral Discharge

81. Clarifier Variations
Peripheral Feed
Center Discharge

82. Clarifier Variations
Radial Discharge Peripheral Feed

83. Clarifier Variations
Tow Bro Clarifier

84. Clarifier Variations
Spiral Sludge Collector

85. Clarifier Variations
Telescoping Valves for RAS Return

86. Each Designed to Address Particular Concern
Clarifier Variations
Many Others
Each Designed to Address Particular Concern

87. Routine Inspection & Maintenance
Clarifier Operation
Routine Inspection & Maintenance
Drive Mechanism
Lubrication (Manufacturers Specs.)
Observe Proper Operation (2/Day)

88. Clarifier Operation
Sludge Judge Daily (Each Shift)

89. Clarifier Operation Rectangular Clarifiers Sludge Collection System
Operating Smoothly
Floating Sludge
Frequent Shear Pin or Breaker Failure
Circular Clarifiers
Skimmer/Sludge Collector
Operating Smoothly
Scum Trough Plugged

90. Clarifier Operation
Cleaning
Weirs – Launder - Center Well

91. Clarifier Operation
The
Hard
Way
The
Easy
Way

92. Clarifier Operation

93. Clarifier Operation
Limit Growth ?

94. Clarifier Operation Limit Growth ?
Covers Block Sunlight Limits Algae Growth

95. Clarifier Operation Limit Growth ?
Covers Block Sunlight Limits Algae Growth
Provides Cold Weather Protection

96. Clarifier Operation Monitoring for Short Circuiting Visual Observation
Flow Over Weir
Solids Over Weir
Dye Testing

97. Routine Inspection & Maintenance
Clarifier Operation
Routine Inspection & Maintenance
Sludge Judge Daily (Each Shift)
Cleaning
Monitoring for Short Circuiting

98. Calculating and Monitoring Loading
Clarifier Operation
Also Includes
Calculating and Monitoring Loading
Detention Time
Surface Overflow Rate
Weir Overflow Rate
Solids Loading Rate

99. CLARIFIERS Prepared By Michigan Department of Environmental Quality
Operator Training and Certification Unit