CLARIFIERS

1
CLARIFIERS
Prepared By Michigan Department of Environmental
Quality Operator Training and Certification Unit
2
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
Stokes Law
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
Stokes 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 Time
Particle Size mm
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
0.00001 Colloidal 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
Stokes Law
Forget the Formula Remember the Removal
Efficiency Depends on Several Factors
9
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 (Lamella) Rectangular Circular
26
Inclined Plate (Lamella)
27
Types of Clarifiers Inclined Plate (Lamella)
Discharge Flumes
Distribution Orifice
Feed Box
Overflow Box
Flocculation Tank
Flash Mix Tank
Coagulant Feed
Clarifier Effluent
Clarifier Influent
Inclined Plates
Sludge Discharge
Sludge Hopper
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
Rails
Wear Shoes
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
Circular Clarifier
A Circular Baffle Directs Flow 
Center Baffle
Influent
63
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
Circular Clarifier
Drive Mechanism Also Drives Skimmer Arm to Remove
Floating Scum 
Scum Baffle
Drive Unit
Skimmer Arm
Influent
68
Circular Clarifier
Drive Mechanism Also Drives Skimmer Arm to Remove
Floating Scum 
69
Circular Clarifier
Drive Mechanism Also Drives Skimmer Arm to Remove
Floating Scum 
70
Circular Clarifier
Drive Mechanism Also Drives Skimmer Arm to Remove
Floating Scum 
71
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
Scum Baffle
Effluent Weir
Effluent Launder
Effluent
Circular Clarifier Outlet
74
The Launder and Weir May Be
1 2 3
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
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
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
Clarifier Variations
Many Others Each Designed to Address Particular
Concern
87
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
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
Clarifier Operation
Routine Inspection Maintenance
Sludge Judge Daily (Each Shift)
Cleaning
Monitoring for Short Circuiting
98
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