A Gritty Face-Off: A Gritty Face Off: Mechanical Vortex Versus

A Gritty Face
Face-Off:
Off:
Mechanical Vortex Versus Stacked
Tray Grit Removal
Jeff Sober
May 27, 2011
NTMWD
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Today, we will discuss:
1
1.
2.
3.
4.
5.
North Texas Municipal Water District
District’s
s
Panther Creek Regional WWTF
Why
y we
e decided
dec ded to put ttwo
o tec
technologies
o og es
side-by-side
How we did it for as cheap
p as p
possible
The grit testing methods used
The results!
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In 2007, Panther Creek
Regional WWTF was built for 5
mgd
g average
g flow
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In 2009, Panther Creek
underwent an expansion from
5 to 10 mgd
g
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The headworks has both forced
and free vortex grit basins
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Forced vortex basins have a low
capital cost
65%
100
200
95%
300
Micron Size
•
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Low headloss
400
The Headcell in theory provides
higher efficiency grit removal
95%
100
200
300
400
Micron Si
Size
e
•
•
•
•
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Large surface area in a small
footprint
Short settling distance
N moving
No
i
parts
t iin-basin
b i
Same level of O&M effort
How can we provide this at the
lowest possible cost?



Don t design Headcell for peak flow
Don’t
Provide system in existing footprint
Optimize flow between systems
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The headworks is rated for 10
mgd average, 30 mgd peak
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Flows of 0 to 15 mgd are sent
to the Headcell
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Peak flows of 15 to 30 mgd are
routed to the vortex
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GRIT TESTING
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To compare the units, we
utilized two testing protocols
1.
Totall grit
accumulation testing
performed by
NTMWD
2.
Third Party vertical
flow p
profile testing
g
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For the first test, we isolated
each unit for one week at a time
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This four week test required
weighing grit every two hours
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This test focused on total grit
removed from the classifiers
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This test focused on total grit
removed from the classifiers
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There was a significant
difference in the total pounds
2,000
1,800
1,600
1,400
Week 2
Vortex
Pou
unds
1,200
Week 4
Vortex
1,000
,000
800
600
400
200
0
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Week 1
Headcell
Week 3
Headcell
We also measured TS and VS
7,000
Total Pounds Removed
Total Solids Removed
6,000
Grit Removed
(Inorganics)
Pounds
s Removed P
Per Week
5 000
5,000
4,000
3,000
2,000
1,000
0
Week 1 (Headcell)
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Week 2 (Vortex)
Week 3 (Headcell)
Week 4 (Vortex)
Results were not as expected
Avera
age Pound
ds Remove
ed Per Day
y
250
200
150
Grit Removed
(Inorganics)
100
50
0
Headcell Average
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Vortex Average
TEST PROTOCOL NO. 2 –
THIRD PARTY TESTING
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Grit Solutions ran vertical
profile tests before and after
the grit
basins
g
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This test measures the amount
of grit that makes it past the
grit
basins
g
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A non-native grit was also
used
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The results show that the grit
basin was working as designed
88%
Removal
6,000
97%
Removal
5,000
Total Pou
unds
4,000
3,000
2,000
1,000
0
Headcell
Influent
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Headcell
Effluent
Vortex
Influent
Vortex
Effluent
Why did this test not agree
with our previous results?
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The system was adjusted
1
1.
2.
Blow down sequence frequency increased
Wash water rates increased
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Another week of testing had
improved results
2,000
1,800
1,600
1,400
1,200
Pounds
Week 4
Vortex
Week 2
Vortex
1,000
800
600
400
200
0
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Separate
Test
Headcell
Week 1
Headcell
Week 3
Headcell
Another week of testing had
improved results
1,200
1,000
Pounds Removed
Solids Removed
Solids Removed
Pounds Reemoved 800
Grit Removed (Inorganics)
600
400
200
0
Headcell Average
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Vortex Average
Headcell Test 2 Average
Let this be a lesson, your eyes
can fool you!
Don’t assume a system is optimized, even if
it is proprietary black box information
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In summary, the new grit
system does remove less
organics
g
Vortex Average
Headcell Average
80%
74%
45%
30%
Percent Solids
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Percent Inorganics
Acknowledgements
1.
2
2.
3.
Steve Kramer, Plant Manager
Elizabeth Turner
Turner, NTMWD Lab
Drew Satterwhite, NTMWD Engineer
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