managing denitrification wood chip bioreactors for maximum nitrate removal and minimum carbon...
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Funded in part by the soybean checkoff
2015 SWCS Conference
July 27, 2015Greensboro, North Carolina
Managing Denitrification Wood Chip Bioreactors for Maximum Nitrate Removal and Minimum Carbon
ExpendedKeegan Kult1 and Dr. Chris Jones2
Iowa Soybean Association1 and University of Iowa, IIHR-Hydroscience and Engineering2
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Drivers
• Limited conservation funding, high public demands• BMP’s need placed using precision conversation
– BMP’s need to be optimized
• Do bioreactors perform more efficiently when operated for higher flow volumes or longer retention times?
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• Removes nitrate-N from field tiles
• Divert water through wood chips
• 30 – 100 acre drainage areas
• Small footprint• 10 – 15 year lifespan
Denitrifying Bioreactors
Image from John Petersen
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• State Nutrient Reduction Strategies– Reduce nitrogen export by
45%– Edge of field practices play
critical role
• ISA has been part of 20 installations
Implementation
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Hamilton County
2010 2012 2013 2014 Total
Nit
rate
-N L
oa
d,
kg
0
100
200
300
400
500
600
Performance
LWFC
2012 2013 2014 Total
Nit
rate
-N l
oad
, kg
0
250
500
750
1000
1250
Potential Load
Actual Load
Greene County
2009 2010 2011 2012 2013 Total
An
nu
al N
itra
te-N
Lo
ad, k
g
0
250
500
750
1000
1250
To
tal N
itra
te-N
Lo
ad, k
g0
500
1000
1500
2000
2500
3000
20 – 32% 12 – 76%
12 – 42%
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Greene County Monthly Performance(2009 – 2013)
Month
Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Nitr
ate-
N,
kg
0
200
400
600
800
1000
1200
Potential Actual
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Study
• Flow management• Nitrate removal/carbon usage• 3 high retention times• 3 low retention times
Funding from Iowa Nutrient Research Center
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Diversion Structure (Upper) Flow Control Structure (Lower)
Low retention time higher flow rateHigh retention time lower flow rate
Bioreactor Flow
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• Weekly to bi-weekly sampling April – August of 2014
• NO3-, TOC, alkalinity
(inorganic carbon)• Flow tracked with pressure
transducer
Monitoring
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Bioreactors Monitored
Bioreactor Location Date Installed Dimensions, ft Acres
drainedYears
monitored
1 UWFC Wright Co., IA Dec. 2011 98 x 8 25 2
2 LEC Wright Co., IA Sep. 2012 98 x 10 40 2
3 LC Hamilton Co., IA July 2012 100 x 20 80 1
4 Fisher Wright Co., IA Aug. 2011 115 x 25 30 --
5 Voss Wright Co., IA Aug. 2012 113 x 8 25 --
6 Tesdell Polk Co., IA Sep. 2013 80 x 6 NA --
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Back-up Plan
Bioreactor HRT Actual HRT
Tes Low Low
Greene Low Low
LEC 2 Low High
Hamilton Low High
LC High High
LWFC High Low
UWFC High High
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2014 Results
Bioreactor Nitrate removed, kg
% Load Reduction
Tes 43 54
Greene 33 13
LWFC 49 33
Bioreactor Nitrate removed, kg
% Load Reduction
UWFC 24 12
LC 38 11
LEC 2 50 6
Hamilton 24 13
Low HRT, high flow volume
High HRT, low flow volume
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UWFC Bioreactor
2014
Apr May Jun Jul Aug Sep Oct
Flo
w m
3 d-1
0
200
400
600
800
1000
Nitr
ate-
N,
mg
L-1
0
5
10
15
20
25
Bioreactor flowBypass flowUWFC InUWFC Out
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Week Flow treatedLoad
Reduction4/2- 4/8 100% 96%4/9 - 4/15 100% 97%4/16 - 4/22 100% 97%4/23 - 4/29 100% 97%4/30 - 5/6 100% 87%5/7 - 5/13 78% 51%5/14 - 5/20 100% 73%5/21 - 5/27 100% 82%5/28 - 6/3 100% 93%6/4 - 6/10 100% 96%6/11 - 6/17 37% 19%6/18 - 6/24 7% 3%6/25 - 7/1 5% 3%7/2 - 7/8 3% 2%7/9/ - 7/15 100% 67%7/16 - 7/22 100% 72%7/23 - 7/29 100% 81%7/30 - 8/5 100% 90%8/6 - 8/12 100% 98%
Total 14% 6%
• 2014 LEC 2 Results
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Hydraulic Retention Time
Low High
HR
T,
days
0.01
0.1
1
10
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Difference of measured vs. predicted alkalinity, kg
Management Samples Median
High retention 27 0.191
High flow 29 0.203
Carbon usage during denitrification
Nitrate-N load removed, kg
0 1 2 3 4 5 6 7
Tot
al a
lkal
inity
gen
erat
ed a
s C
aCO
3,
kg
-2
0
2
4
6
8
10
High retention bioreactorsHigh flow-volume bioreactorsPredicted alkalinity generated
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2014 Bioreactor Carbon Usage
Bioreactor
Tes Greene LWFC UWFC LC LEC 2 Hamilton
Un
it C
arb
on g
ener
ate
d p
er
Nitr
ate-
N u
nit
rem
ove
d
-2
0
2
4
6
8
10
12
Low Retention TimeHigh Retention Time
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Cost Effectiveness
Bioreactor Annual N removed, lbs
Projected 10 year removal, lbs
Projected 15 year removal, lbs Installation cost
Hamilton 143 1,430 2,145 $6,800
Greene 271 2,710 4,065 $10,500
Practice Cost per lb of N removedBioreactors $2.58 - $4.75
Soil testing & side dressing $1.15 Saleh et al. (2007)
Drainage water management $2.71 Jaynes & Thorp (2008)
Wetlands $3.26 Hyberg (2007)
Fall cover crops $11.06 Saleh et al. (2007)
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• Low flow 6 – 13% load reduction
• High flow 13 – 54% load reduction
• Differing flow regimes removed similar loads of N
• No difference in carbon usage
Summary
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• Know tile system before installing
• Difficult to control flow• Large events drive
performance more than management
Lessons Learned
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Acknowledgements
• Project was funded by the Iowa Nutrient Research Center and supplemental data was used from projects funded by an USDA-NRCS Conservation Innovation Grant as well as contracts with private landowners.
• This presentation was prepared by K. Kult and C. Jones under grant number C5-52718-00 from the Iowa Nutrient Research Center. Any opinions, findings, and conclusions or recommendations expressed are those of the authors and do not necessarily reflect the views of the Iowa Nutrient Research Center or Iowa State University.