A Methodology To Design and/or Assess Baffles for Floatables Control Thomas L. Newman II, P.E....
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Transcript of A Methodology To Design and/or Assess Baffles for Floatables Control Thomas L. Newman II, P.E....
![Page 1: A Methodology To Design and/or Assess Baffles for Floatables Control Thomas L. Newman II, P.E. HydroQual, Inc.](https://reader036.fdocuments.net/reader036/viewer/2022062618/55146aaa550346414e8b5d7a/html5/thumbnails/1.jpg)
A MethodologyA MethodologyTo Design and/or AssessTo Design and/or Assess
Baffles for Floatables Control Baffles for Floatables Control
Thomas L. Newman II, P.E.
HydroQual, Inc.HydroQual, Inc.
![Page 2: A Methodology To Design and/or Assess Baffles for Floatables Control Thomas L. Newman II, P.E. HydroQual, Inc.](https://reader036.fdocuments.net/reader036/viewer/2022062618/55146aaa550346414e8b5d7a/html5/thumbnails/2.jpg)
HydroQual, Inc.
Introduction Interest in Baffles
– EPA CSO Control Policy / 9 Minimum Controls– Municipalities seek cost-effective alternatives
Advantages of Baffles– Low Cost (capital and maintenance)– Simple Design– Easy to Retrofit – Usable with Other Technologies
Disadvantages of Baffles– Not much information available– Limited analytical tools to assess performance
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HydroQual, Inc.
Objective
Develop an Improved Method
to Assess the
Floatables-Removal Efficiency
of Baffles
![Page 4: A Methodology To Design and/or Assess Baffles for Floatables Control Thomas L. Newman II, P.E. HydroQual, Inc.](https://reader036.fdocuments.net/reader036/viewer/2022062618/55146aaa550346414e8b5d7a/html5/thumbnails/4.jpg)
HydroQual, Inc.
Application of Baffles
For Floatables
Control
Typical Regulator (Without Baffle)
Dry Weather: 100% capture of
– Flow– Floatables
Section View
Plan View
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HydroQual, Inc.
Application of Baffles
For Floatables
Control
Typical Regulator (Without Baffle)
Wet Weather: CSO Discharge of
– Flow– Floatables
Section View
Plan View
(continued)
![Page 6: A Methodology To Design and/or Assess Baffles for Floatables Control Thomas L. Newman II, P.E. HydroQual, Inc.](https://reader036.fdocuments.net/reader036/viewer/2022062618/55146aaa550346414e8b5d7a/html5/thumbnails/6.jpg)
HydroQual, Inc.
Application of Baffles
For Floatables
Control
(continued)
Typical Regulator With Baffle Installed
Wet Weather: CSO Discharge of
– Flow– Fewer Floatables
Section View
Plan View
Baffle
Baffle
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HydroQual, Inc.
Application of Baffles
For Floatables
Control (continued)
Typical Regulator With Baffle Installed
Wet Weather: CSO Discharge of
– Flow– Fewer Floatables
Section View
Plan View
Baffle
Baffle
![Page 8: A Methodology To Design and/or Assess Baffles for Floatables Control Thomas L. Newman II, P.E. HydroQual, Inc.](https://reader036.fdocuments.net/reader036/viewer/2022062618/55146aaa550346414e8b5d7a/html5/thumbnails/8.jpg)
HydroQual, Inc.
- Laminar streamlines
- Neutrally buoyant items follow streamlines, Vx
Previous Analytical Approaches Non-turbulent-Flow Case
Channel
Baffle
- Floatables: rise velocity, Vz
Xo
- Capture if trajectory intercepts baffle
Zo
- Minimum Vz for capture (from given release point):
Vz,min = Zo Vx / Xo (Dalkir, 1996; Cigana, 1998, 1999)
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HydroQual, Inc.
Turbulent-Flow Case– Mixing between streamlines
– reduces effective Vz by the RMS velocity component of the vertical turbulence, V* = Vx (n g Rh
1/3 )1/2
Previous Analytical Approaches
Channel
Baffle
Drawdown Zone
- Minimum Vz must also compensate for downward turb. component
Vz,min = Zo Vx / Xo + C V* (C factor 0.4 - 1.6) (Dalkir, 1996; Cigana, 1998, 1999)
- Minimum Vz (compensating for extra required rise, Zd)
Vz,min = (Zo + Zd) Vx / Xo + C V* (C = 0.4 - 1.6) (Dalkir, 1996)
(continued)
Zd
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HydroQual, Inc.
Previous Analytical Approaches
Determine Removal Efficiency from Rise Velocity – Use distribution curve– Laboratory tests on 2,000
items from 2 Montreal CSOs
Example:
Vz,min = 10 cm/s
Efficiency = 20 %
(continued)
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HydroQual, Inc.
Shortcomings of Previous Approach (and the solutions!)
1 Requires multiple calculations: – for overall performance
(each release point over the depth)
– for each change in baffle position, flow rate, water level, etc.
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HydroQual, Inc.
Shortcomings of Previous Approach (and the solutions!)
Solution: Spreadsheet Model
inputs standardizedautomatic integration
(gives overall efficiency)easy for sensitivity runscompare results using
different approaches
(Continued)
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HydroQual, Inc.
Shortcomings of Previous Approach (and the solutions!)
2 Does Not Account for Effect of Flow Path: – only release point and
baffle position – ignores downward velocity
component of flowpredicts 100% capture
if baffle extends below inlet invert level
overpredicts capture!
(Continued)
Section View
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HydroQual, Inc.
Shortcomings of Previous Approach (and the solutions!)
Solution: Assume A Simple Flow Path
accounts for effect of baffle position and regulator geometry on flowstream
Example...
(Continued)
Section View
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HydroQual, Inc.
Shortcomings of Previous Approach (and the solutions!)
Example:– Item in top streamline must rise
a small distance.– Item in bottom streamline must
rise full distance (Zs+Zd) before traveling the distance S:
Therefore: Vz,min = (Zs+Zd)Vs / S ( + C V* ) where Vs is speed along streamline
(Continued)
SZs
Section View
Zd
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HydroQual, Inc.
Shortcomings of Previous Approach (and the solutions!)
3 Does Not Account for Underflow Capture: – some floatables captured in
the underflow – model not applicable to
“pre-baffle” conditioncannot determine
Net Effectiveness of Baffle Installation
(Continued)
Section View
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HydroQual, Inc.
Shortcomings of Previous Approach (and the solutions!)
Solution: Account for “Escape Velocity” Example… Underflow = 20% of Inflow, Bottom 20% of streamlines to
underflow Floatables that can rise out of
underflow streamlines “escape” but remaining are captured
Add underflow capture to baffle capture for overall capture.
(continued)
Section View
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HydroQual, Inc.
Shortcomings of Previous Approach (and the solutions!)
Efficiency based on 2 Montreal CSOs, but these appear to differ from NYC composition– fewer on high and low
end of spectrum– cause under- or over-
estimate of performance
NYC tests coming...
Quiescent Rise-Velocity DistributionFor CSO Floatables
0
20
40
60
80
100
0.1 1 10 100
Rise Velocity (cm/s)
Pe
rce
nt
Gre
ate
r T
ha
n
Sp
ec
ifie
d V
elo
cit
y
CEGEO /Meunier
Alden Labs(estimated)
(continued)
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HydroQual, Inc.
Comparison / Verification of Results
Previous Approaches Predict Higher Removal Efficiency Than New Model
New Model Still Predicts Relatively High Performance Comparison to Lab Data is Favorable, but Not “Apples to Apples”
0
20
40
60
80
100
No BaffleTest 1
Baffle Test 1
. No BaffleTest 5
BaffleTest 5
Dalkir+
Cigana+
New
Data(Alden)P
erc
en
t C
ap
ture
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HydroQual, Inc.
Conclusions
New, Improved Model to Assess the Floatables-Removal Efficiency of Baffles – Fully Compatible with Previous Approaches– Spreadsheet format– Considers flow path– Accounts for underflow capture– Enables assessment of “pre-baffle condition” and
the net effectiveness of the installation– Awaiting experimental data to further verify model
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HydroQual, Inc.
For More Information
Tom Newman
HydroQual, Inc.
www.hydroqual.com
(201) 529-5151