1. ROTATING BIOLOGICAL CONTACTOR (RBC) PROCESS
Prepared By
Michigan Department of Environmental Quality
Operator Training and Certification Unit

2. ROTATING BIOLOGICAL CONTACTORS
Primary
Treatment
Secondary
Clarifier
Effluent
Influent
Solids Removal

3. RBC Secondary Treatment
Rotating
Plastic Media
1.6 rpm
Provides Large Surface Area
40 %
Submerged
Microorganisms “Treat” the Wastewater by Using Organics

4. Wastewater New Cells NH3 CO2 Slime Layer H2O Cell Membrane Food Oxygen
Storage
Enzymes
(Absorption)
Adsorbed
Particle
Soluble Organics

5. Oxygen
Organics
Liquid Film
Biomass
Media
(disc)
Oxygen

6. Media OXYGEN Liquid Film Liquid Film Random Continuous Sloughing
Organics
BIOMASS
Media

7. RBC Flow Scheme INFLUENT Rotating Biological Contactors EFFLUENT
Primary
Treatment
Rotating
Biological
Contactors
Pretreatment
Disinfection
Secondary
Clarifiers
EFFLUENT
Solids Handling

8. ADVANTAGES OF RBC PROCESS
Simple Operation
Low Energy Requirements
Nitrification
Few Nuisances
Wide Flow Range
Large Biological Population

11. ADVANTAGES OF RBC PROCESS
Simple Operation
Low Energy Requirements
Nitrification
Few Nuisances
Wide Flow Range
Large Biological Population
Handles Shock Loads
Low Head Loss

12. Limited Experience and Training
DISADVANTAGES OF
RBC PROCESS
Limited Controls
Enclosures
Limited Experience and Training

13. RBC COMPONENTS
CONTACTOR
TANK
CLARIFIER

14. RBC COMPONENTS
CONTACTOR
Discs
Shaft
Individual Disc

15. Media
“High Density” Polyethylene
Carbon
Black

16. Increases Surface Area Increases Contact Time
Media – Irregular Surface
Maintain Spacing
Increases Rigidity
Increases Surface Area
Increases Contact Time

17. Media – Irregular Surface
“Corrugated”

18. Media – Irregular Surface
“Dimpled”

20. “Random Fill”

21. Media
1 Inch
BIOMASS

22. 10 to 12 Ft
Diameter
~ 25 Ft
Long

23. Media
Standard
Density
High
Density
1 inch
¾ inch

25. Shaft
Square Shaft

27. Round Shaft

28. Octagonal Shaft

30. Bearings
“Floating”
Self-aligning

31. Bearings

32. Load Cells
Shaft
Bearing
Load
Cell
Coupling for
Hydraulic
Pump

33. Load Cells
Purpose: Determine Weight of Contactor to Determine Amount (Thickness) of Biomass

34. Drive Systems
- Chain

35. Drive Systems
- Direct

36. Drive Systems
- Air
Air Cups
Air
Header
Air Diffusers

37. Drive Systems
- Air
Air Cups
Rotation
Air Header

38. Drive Systems
- Air

39. Drive Systems
- Air

40. Drive Systems
- Combination

41. Containment

42. Containment Good Contact Minimal Short Circuiting Good Mixing
Just Large Enough
Good Contact
Minimal Short Circuiting
Good Mixing

43. “Train”
FLOW
FLOW
RBC Systems Usually More Than One Contactor with Flow Progressing in Series in a “Train”

44. Flow Schemes Parallel to Shaft Direction of Flow
Perpendicular to Shaft
Contactors May be Arranged With Flow Either Parallel or Perpendicular to Shafts

45. “Train”
Small Systems – Train May be One Contactor with Separations and Baffles
Influent
Effluent
Baffles

46. Larger Systems – Contactors are Set in Series in Separate Tanks or in One Tank With
Enclosure
Effluent
Influent
Baffles

47. Baffles

48. Train Baffles FLOW FLOW Baffles Separate Each Contactor,
Dividing the Flow in the Train Into Separate
Complete Mix Zones of Treatment

49. Each Zone of Treatment is Called a
Train
Baffles
FLOW
Each Zone of Treatment is Called a
“Stage”

50. Train
Baffles
FLOW
Stages 5
(Zones of Treatment)

51. 2 Trains Influent 5 Stages Effluent 1st Stage
When a System Has More Than One Train, Each Zone in the System That Receives the Same Loading is Considered One “Stage”

52. Staging Results in Significantly More Efficient Treatment
100
BOD, mg/L 60 39 25 18
Staging Results in Significantly More Efficient Treatment

53. STAGING BOD, mg/L Ammonia Nitrogen, mg/L 100 60 39 25 18 12 9 7
Stage
Ammonia Nitrogen, mg/L
This Especially Important for Facilities that are Required Nitrify Ammonia

54. RBC Flow Scheme INFLUENT Rotating Biological Contactors EFFLUENT
Primary
Treatment
Rotating
Biological
Contactors
Pretreatment
Disinfection
Secondary
Clarifiers
EFFLUENT
Solids Handling

55. Secondary Clarifier
Scum Removal
Influent
Effluent
Sludge
Removal

56. Chemical Phosphorus Removal
Clarifier
500 to 800 gpd/sq.ft.
Chemical Phosphorus Removal
Sludge Removal

57. Protect Contactors Enclosures Ultraviolet Light Hard Rains Freezing
Algae
Equipment
Security

58. Enclosures Types of Structures Roof Only Prefabricated Covers
Permanent Building

59. Enclosures
Prefabricated Covers

60. Enclosures
Permanent Building

61. Enclosures
Permanent Building

62. Operational Considerations
Enclosures
Operational Considerations
Ventilation
Humidity Control
Heat Loss
Observation
Maintenance

63. Basic Principles of Process
Contactors
Primary
Treatment
Secondary
Clarifier
Effluent
Influent
Solids Removal

64. (Related to the SIZE of the System)
“LOADING”
Amount Applied
to the
Treatment Process
(Related to the SIZE of the System)
Hydraulic Loading
Amount of Liquid
Volume (gallons)
Organic Loading
Amount of BOD
Weight (pounds)
(Calculation of Loading is Specific for Each
Type of Treatment Process)

65. Applied to the Media surface Complete Available Surface Area
RBC LOADINGS
HYDRAULIC
Liquid Volume -
Applied to the Media surface
Use Plant Flow
- No Recirculation
Complete Available Surface Area
Area is Not Calculated
- from Manufacturer

66. RBC LOADINGS gpd / Ft2 HYDRAULIC GALLONS PER DAY PER SQUARE FOOT
Liquid Volume -
Applied to the Media surface
GALLONS PER DAY
PER
SQUARE FOOT
gpd / Ft2

67. RBC LOADINGS HYDRAULIC FORMULA: Flow Rate, gpd
Hydraulic Loading, gpd/ft2 =
Media Surface Area, ft2
EXAMPLE:
Plant Flow MGD
Trains in Service 2
Contactors in Each Train 5
Baffles Between All Contactors
Each Contactor Surface Area 100,000 ft2 (from manufacturer)
Primary Effluent Soluble BOD 55 mg/L

68. Train
Baffles
FLOW
FLOW 5
Stages
(Zones of Treatment)

69. RBC LOADINGS HYDRAULIC = 1,000,000 ft2 FORMULA: Flow Rate, gpd
Hydraulic Loading, gpd/ft2 =
Media Surface Area, ft2
EXAMPLE:
Plant Flow MGD
Trains in Service 2
Contactors in Each Train 5
Baffles Between All Contactors
Each Contactor Surface Area 100,000 ft2 (from manufacturer)
Primary Effluent Soluble BOD 55 mg/L
Total Surface Area =
2 trains X 5 contactors/train X 100,000 ft2/contactor
= 1,000,000 ft2

70. RBC LOADINGS = HYDRAULIC = 2.4 gpd/ft2 2,400,000 gpd 1,000,000 ft2
FORMULA:
Flow Rate, gpd
Hydraulic Loading, gpd/ft2 =
Media Surface Area, ft2
2.4 MGD
X 1,000,000 gal/MG
Hydraulic Loading, gpd/ft2 =
1,000,000 ft2
2,400,000 gpd =
1,000,000 ft2
= 2.4 gpd/ft2

71. Media Surface Area – (Not Volume)
RBC LOADINGS
ORGANIC
Organic Matter - BOD
Applied to the Media Surface
Soluble BOD
Media Surface Area – (Not Volume)
Area in 1000 Ft2

72. Applied to the Media surface Pounds Soluble BOD per Day
RBC LOADINGS
ORGANIC
Organic Matter -
Applied to the Media surface
Pounds Soluble BOD per Day
per 1000 ft2
#Sol. BOD/Day/1000 ft2

73. Soluble BOD Applied, # Sol. BOD/Day
RBC LOADINGS
ORGANIC
FORMULA:
Organic Loading, # Sol. BOD/Day/1000 ft2 =
Soluble BOD Applied, # Sol. BOD/Day
Media Surface Area in 1000 ft2

74. RBC LOADINGS ORGANIC = 1100 # Sol. BOD/Day Pounds Soluble BOD/Day =
FORMULA:
Soluble BOD Applied, # Sol. BOD/Day
Organic Loading, # Sol. BOD/Day/1000 ft2 =
Media Surface Area in 1000 ft2
EXAMPLE:
Plant Flow MGD
Trains in Service 2
Contactors in Each Train 5
Baffles Between All Contactors
Each Contactor Surface Area 100,000 ft2 (from manufacturer)
Primary Effluent Soluble BOD 55 mg/L
Pounds Soluble BOD/Day =
55 mg/L x 2.4 MGD x 8.34 #/gal
= 1100 # Sol. BOD/Day

75. RBC LOADINGS = ORGANIC = 1,000 (1000 ft2) = 1,000,000 ft2
Total Surface Area =
2 trains X 5 contactors/train X 100,000 ft2/contactor
= 1,000,000 ft2
Total Surface Area ft2
Surface Area in 1000 ft2 =
1000
1,000,000 ft2 =
= 1,000 (1000 ft2)
1000

76. Soluble BOD applied, # Sol. BOD/Day
RBC LOADINGS
ORGANIC
FORMULA:
Organic Loading, # Sol. BOD/Day/1000 ft2 =
Soluble BOD applied, # Sol. BOD/Day
Media Surface Area in 1000 ft2
1100 # Sol. BOD/Day =
Total System Org. Ld.
1,000 (1000 ft2)
= 1.1 # Sol. BOD/Day/1000 ft2

77. RBC LOADINGS FIRST STAGE ORGANIC = 1100 # Sol. BOD/Day
EXAMPLE:
Plant Flow MGD
Trains in Service 2
Contactors in Each Train 4
Baffles Between All Contactors
Each Contactor Surface Area 100,000 ft2 (from manufacturer)
Primary Effluent Soluble BOD 55 mg/L
Pounds Soluble BOD/Day =
= 1100 # Sol. BOD/Day
55 mg/L x 2.4 MGD x 8.34 #/gal

78. 2 Trains Influent 5 Stages Effluent 1st Stage
When a System Has More Than One Train, Each Zone in the System That Receives the Same Loading is Considered One “Stage”

79. RBC LOADINGS = FIRST STAGE ORGANIC = 200 (1000 ft2)
First Stage Surface Area =
2 contactors X 100,000 ft2/contactor
= 200,000 ft2
First Stage Surface Area in 1000 ft2 =
First Stage Surface Area ft2
1000
200,000 ft2 =
= 200 (1000 ft2)
1000

80. Soluble BOD applied, # Sol. BOD/Day
RBC LOADINGS
ORGANIC
FORMULA:
Organic Loading, # Sol. BOD/Day/1000 ft2 =
Soluble BOD applied, # Sol. BOD/Day
Media Surface Area in 1000 ft2
1100 # Sol. BOD/Day =
First Stage Org. Ld.
200 (1000 ft2)
= 5.5 # Sol. BOD/Day/1000 ft2

81. CARBONACEOUS BOD REMOVAL
TYPICAL RBC LOADINGS
HYDRAULIC
CARBONACEOUS BOD REMOVAL
2 to 4 gpd/Ft2
NITRIFICATION
1.0 to 1.5 gpd/Ft2

82. (For Typical 30 mg/L Requirements)
TYPICAL RBC LOADINGS
Organic
(For Typical 30 mg/L Requirements)
All Media
2.0 #Sol. BOD/DAY/1000 ft2
First Stage
2.5 to 4.0 #Sol. BOD/DAY/ 1000 ft2
3.0 for mechanical drive
EPA - “caution over 2.5”

83. ROTATING BIOLOGICAL CONTACTOR (RBC) PROCESS
Prepared By
Michigan Department of Environmental Quality
Operator Training and Certification Unit