Presentation by Mike Arpin / S&L to Opus D&K Mar 2012

3. B&B’s Process Equipment experience includes lines from
companies such as
• LIGHTNIN/SPX
• SWECO
•SMITH & LOVELESS
•SPIROFLOW
•THERMO FISHER SCIENTIFIC
•J&H
•V-SEP
•PERIFLO
•MERRICK/BIF

4. Grit Presentation
Presented By:
Mike Arpin, Smith & Loveless Inc.
& Greg Gurd Black & Baird
© Smith & Loveless, Inc. 2010

5. Outline
• Fundamentals
• Grit Removal Efficiencies
• Vortex Grit Chambers
• Water Level Velocity Control
• Grit Testing Methodologies
• Grit Study - Grit at WWTP & USGS River Bed Sediment
• Grit Pumping
• Don’ts
• Grit Dewatering/Grit Classifiers & Washers
• Packaged Headworks

6. Fundamentals
• What is grit?
• Specific gravity
• Classifying grit
• Velocity

7. What is Grit?
• Grit is heavy mineral matter consisting of a variety of
particles including sand, gravel, cinder, and other heavy,
discrete inorganic
materials found in
domestic sewage.
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

8. What is Grit?
• The EPA’s Wastewater Technology Fact Sheet (Screening &
Grit Removal), defines grit as “particles larger than 0.21 mm
(.008 in.) (65 mesh) and
with a specific gravity of
greater than 2.65.”
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

9. What is Specific Gravity?
• Correlates to a particle’s settling velocity, which measures the
speed or time a particle will settle in the water.
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

10. Grit & Specific Gravity
• Grit particles develop a thin coating of iron oxide or iron
sulfide when exposed to wastewater.
• This coating, does not alter the particle’s specific gravity.

11. What is Specific Gravity?
• Appropriate retention time must be maintained for grit to settle
& be captured.
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

12. What is Specific Gravity?
• Settling velocities & retention times do not apply to forced
vortex systems.
• Forced vortex systems use
hydraulic forces to remove grit.
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

13. Classifying Grit Particles
• Mesh sizing is a common way to classify grit particle sizes.
• Increasing mesh values translates into smaller grit particle
diameters.
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

14. Classifying Grit Particles
• Typical domestic sewage grit ranges from 20 to 140 mesh.
• Majority of grit (90+ %) normally ranges between 50 and
100 mesh.
• Quantity may vary based upon geographic location.
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

15. Classifying Grit Particles
• Abrasive grit particles (100+ mesh) create the
greatest problems.
• Particles smaller than 140 mesh display buoyant,
silt-like characteristics.
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

16. Rule of Thumb
SEPARATE SEWERS
3
Average 2 to 4 ft per 3,785
CMD
3
Peak 8 ft per 3,785 CMD
COMBINED SEWERS
3
Average 8 to 20 ft per CMD
3
Peak 40 ft per CMD

17. Velocity
• Velocity plays a key role in grit travel through a collection
system & WWTP.
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

18. Understanding Flume Flow
Dynamics & Velocities
The low velocity is near
the left & right walls,
and near the bottom
corners. The highest
velocity is in the center
of the flume. The high
velocity pushes
obstructions towards
the low velocity areas.
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

19. Ideal Flow Velocities
• Range between 0.48m to 1.07m or 1.6 to 3.5 ft./second.
• Causes grit suspension in the flow, traveling like a
moving bed.
• Higher velocities (above 1.07m or 3.5 ft./second), the
flow becomes turbulent dispersing the grit bed.
• Lower velocities (below 0.48m or 1.6 ft./second), grit will
settle & have limited movement.

20. Flow Velocities
• Multiple straight currents exist within a flume, each with
varying velocities.
• Grit will generally be found where the lowest velocities occur.
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

21. Understanding Flume Flow
Dynamics & Velocities
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

22. Grit Removal Efficiency

23. Grit Removal Efficiency
• 270 Degree or 360 Degree with Weir
- 95% of 50 mesh grit and larger
- 85% of 70 mesh grit but less than 50 mesh
- 65% of 100 mesh grit but less than 70 mesh
• 360 Degree w/ Baffling System
- 95% of 140 mesh

24. Vortex Grit Chambers

25. 270 Degree Layout
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

26. Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

27. 360 Degree Layout
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

28. Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

30. Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

32. Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

33. Vortex Grit Chamber Design
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

34. Gravity Based Vortex Systems
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

35. Hydraulic Based Gravity Based
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

36. Gravity Grit Chamber Design
Illustration from Jones & Attwood

39. Photo taken by S&L during site visit.

40. Water Level / Velocity Control

41. Understanding Flume Flow
Dynamics & Velocities
The minimum
inlet channel
velocity - 1.6
feet/second.
The maximum
inlet channel
velocity - 3.5
feet/second.
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

42. V-FORCE FLOW SUBMERGED FLOW
BAFFLE at 1.6 FT/SEC WEIR at 1.6 FT/SEC
360-DEGREE (MGD) 360-DEGREE (MGD)
1.0B 0.2 1.0A 0.1
2.5B 0.3 2.5A 0.6
4.0B 0.4 4.0A 1.0
7.0B 0.7 7.0A 1.8
12.0B 1.1 12.0A 4.0
20.0B 1.9 20.0A 7.0
30.0B 2.9 30.0A 10.0
50.0B 5.0 50.0A 18.0
70.0B 7.0 70.0A 22.0
100.0B 10.0 100.0A 37.0

43. Grit Pumping

44. 250 GPM / 500 GPM
• Up to 30 MGD, use 250 GPM
• 30 MGD Plus, use 500 GPM
• Option A - Top Mounted Vacuum Primed
• Option B - Flooded Suction

45. Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

48. Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

49. Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

50. Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

52. Grit Piping Rules
• Suction Piping Should be Kept to a Minimum (Less than
10’-15’)
• Never Use Check Valves, instead use Pinch Valves
• Use Good Screening Equipment Ahead of Grit Process
(3/4” max. opening)

53. Grit Piping Rules
• Remove All Grit From Basin
• Use Water Flush Into Suction Line
• May Run Flush Water While Pumping
• Do NOT Depend on Gravity

54. Grit Piping Rules
• Use Dedicated Suction & Discharge Lines for Dual
Pumps
• Eliminate Unnecessary Elbows
• Use 45o Elbows if Necessary

55. Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

56. Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

58. Don’ts

59. Avoid Siphoning Problems
• Watch out for Siphoning - Inlet to the Grit
Concentrator must be 24 inches above the water level
in the grit removal chamber to prevent siphoning

60. Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

61. Avoid Short Inlet problems
• Watch out for short inlet flumes, which create unnecessary
and excessive turbulence which can affect the removal
efficiency of a forced or gravity based vortex unit.

62. Grit Dewatering

66. Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

68. Inside Look of the
Screw Conveyor

69. Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

70. Why a Grit Washer?
• Growing Landfill Restrictions.
• Growing Concerns About Odor & Disease Conveying Insects.
• More Stringent Regulations, and we see this preference in the
Midwest and Northeast.

71. Grit Washer

73. Grit Washer
Reprinted with the permission of Smith & Loveless, Inc. © 2007-2010.

74. Packaged Headwork
Technologies

76. PISTA WORKS® ™
Peak System
Model Installed Footprint
Flow Capacity
Model 0.5 0.5 MGD 8'-0 Wide x 18'-0 High x 45'-0 Long
Model 1.0 1.0 MGD 8'-0 Wide x 18'-0 High x 45'-0 Long
Model 2.5 2.5 MGD 8'-0 Wide x 18'-0 High x 46'-0 Long
Model 4.0 4.0 MGD 8'-0 Wide x 18'-0 High x 47'-0 Long
Model 7.0 7.0 MGD 12'-0 Wide x 18'-0 High x 49'-0 Long
Model 12.0 12.0 MGD 12'-0 Wide x 18'-0 High x 49'-0 Long

77. THANK YOU