11th International Drainage Symposium August 30-September 2, 2022 Des Moines, Iowa

1. LONG-TERM
NITRATE REMOVAL
PERFORMANCE OF
FOUR DENITRIFYING
WOODCHIP
BIOREACTORS IN
EASTERN SOUTH
DAKOTA
John McMaine
Ag and Biosystems
Engineering

2. ACKNOWLEDGEMENTS
▪Those who have gone before
▪ Shelby Duncan
▪ Kristen Almen
▪ Pavan Kulkarni
▪ John Maursetter
▪ David Kringen
▪ Rachel McDaniel
▪ Todd Trooien
▪ Chris Hay
▪ Jeppe Kjaersgaard
▪ Laurent Ahiablame
▪ Utsav Thapa
▪ Cynthuja Partheeban
2

3. ACKNOWLEDGEMENTS
▪Thank you to those who supported this project,
especially:
▪ South Dakota Agricultural Experimental Station
▪ South Dakota NRCS
▪ Minnehaha Conservation District
▪ Dr. Laura Christianson for assistance in sample experimental
design and analysis
3

4. STUDY SITES
4

5. STUDY SITES
5

6. ARLINGTON RESULTS
6
0
10
20
30
40
50
60
70
80
90
100
2013 2014 2015 2016 2017 2018 2019
Arlington
Annual Average Concentration Reduction

7. ARLINGTON RESULTS
7
0
5
10
15
20
25
30
0
10
20
30
40
50
60
70
80
90
100
2013 2014 2015 2016 2017 2018 2019
Total
Annual
Precipitation
Arlington
Annual Average Concentration Reduction Total Annual Rainfall

8. HARTFORD RESULTS
8
0
10
20
30
40
50
60
70
80
90
100
2013 2014 2015 2016 2017 2018 2019 2020
Annual
NO3
Concentration
Reduction
Year
Hartford
Annual Average Concentration Reduction

9. HARTFORD RESULTS
9
0
5
10
15
20
25
30
35
0
10
20
30
40
50
60
70
80
90
100
2013 2014 2015 2016 2017 2018 2019 2020
Total
Annual
Precipitation
Annual
NO3
Concentration
Reduction
Year
Hartford
Annual Average Concentration Reduction Total Annual Rainfall

10. MONTROSE RESULTS
10
0
10
20
30
40
50
60
70
80
90
2013 2014 2015 2016 2017 2018 2019
Annual
NO3
Concentration
Reduction
Year
Montrose
Annual Average Concentration Reduction

11. MONTROSE RESULTS
11
0
5
10
15
20
25
30
35
0
10
20
30
40
50
60
70
80
90
2013 2014 2015 2016 2017 2018 2019
Total
Annual
Precipitation
Annual
NO3
Concentration
Reduction
Year
Montrose
Annual Average Concentration Reduction Total Annual Rainfall

12. STUDY OF THE INTERNAL HYDRAULICS OF AN
AGED DENITRIFYING WOODCHIP BIOREACTOR
~SHELBY DUNCAN~
12
BALTIC, SD BIOREACTOR
Photo credit - Cynthuja Partheeban

13. NITRATE REDUCTION RESULTS
• Nitrate samples have
been taken since
2013.
• Nitrate removal rates
are decreasing faster
than estimated
leading to the belief
that the bioreactor is
reaching the end of
its useful life.
13

14. 14

15. METHODS & MATERIALS
• Water samples taken at the inlet and outlet once a
week when the bioreactor was flowing
Nitrate Sampling
• 3.2 kg of Potassium Bromide was injected into the
inlet control structure
• Water samples were taken every 30 minutes after
injection
• Flow was tracked using a pressure transducer with
data points logged every 1 minute
Tracer Study
• Linear interpolations was used to estimate data
between samples
• Moving average was used to transform the data over
a 4.5-hr time-step
Data Analysis
15
Photo by John McMaine

16. TRACER STUDY
RESULTS
• Mean Tracer
Residence time
• 31.60 hrs
• Time to Peak
• 34.50 hrs
• Theoretical HRT
• 10.76 hrs
16

17. 17

19. SHORT CIRCUITING
▪ Short circuiting occurs when water finds preferential paths
through a system. This leads to a lower HRT leaving water
under treated.
▪ Under conditions with no short circuiting, the S value would be
1.0.6 Since S value is 0.77, some short circuiting is occurring in
the bioreactor.
▪ Other aged bioreactors had S values ranging from 0.55 to 0.76.2
𝑆 =
𝑡16
𝑡50
= 0.77
19

20. PREDOMINANT FLOW TYPE
▪ A Mass Dispersion Index (MDI) of 1.0 is indicative of ideal plug
flow where an MDI greater than 2.0 indicates that the dominate
flow type is that of a continuously stirred tank reactor.7
▪ Other aged bioreactors which had MDIs ranging from 3.2-4.2.2
▪ An MDI of 1.84 is lower than other aged bioreactors; the
dominant flow is still considered to be plug flow.
▪ This does not indicate a failing bioreactor.
𝑀𝐷𝐼 =
𝑡90
𝑡10
= 1.84
20

21. NUMBER OF TANKS IN SERIES
▪ When n is 1, the bioreactor is completely mixed (continuously
stirred tank reactor); as n reaches infinity, the flow is plug flow. 4
▪ 19.83 is relatively high for a system like this, so plug flow is the
predominant flow.
▪ This does not indicate a failing bioreactor.
𝑛 =
𝜏2
𝜎2
= 19.83
21

22. 22

23. CONCLUSION
▪ The short circuiting index was not low enough to hint at
major issues
▪ Both the MDI and tanks in series pointed to plug flow
▪ Though the nitrate reduction trend was showing that
the bioreactor was close to failure, other factors may
have been the cause
23

24. 24
REFERENCES
1Christianson et al. (2020). Denitrifying bioreactor Woodchip RECHARGE: Media properties after nine
years. Transactions of the ASABE, 63(2), 407–416. https://doi.org/10.13031/trans.13709
2Christianson, L., Helmers, M., Bhandari, A., & Moorman, T. (2013). Internal hydraulics of an agricultural
drainage denitrification bioreactor. Ecological Engineering, 52, 298–307.
https://doi.org/10.1016/j.ecoleng.2012.11.001
3Hampson, M. (2018, March 21). Marine dead zones in Gulf of Mexico are expected to last decades.
American Association for the Advancement of Science. Retrieved March 15, 2022, from
https://www.aaas.org/news/marine-dead-zones-gulf-mexico-are-expected-last-decades
4Kadlec, R. H., & Knight, R. L. (1998). Treatment wetlands. CRC Lewis Publishers.
5Knobeloch, L., Salna, B., Hogan, A., Postle, J., & Anderson, H. (2000). Blue babies and nitrate-
contaminated well water. Environmental Health Perspectives, 108(7), 675–678.
https://doi.org/10.1289/ehp.00108675
6Ta, C. T., & Brignal, W. J. (1998). Application of computational fluid dynamics technique to Storage
Reservoir Studies. Water Science and Technology, 37(2), 219–226.
https://doi.org/10.2166/wst.1998.0143
7Teixeira, E. C., & do Nascimento Siqueira, R. (2008). Performance Assessment of Hydraulic Efficiency
Indexes. Journal of Environmental Engineering, 134(10), 851–859.
https://doi.org/10.1061/(asce)0733-9372(2008)134:10(851)

25. ACKNOWLEDGEMENTS
▪Those who have gone before
▪ Shelby Duncan
▪ Kristen Almen
▪ Pavan Kulkarni
▪ John Maursetter
▪ David Kringen
▪ Rachel McDaniel
▪ Todd Trooien
▪ Chris Hay
▪ Jeppe Kjaersgaard
▪ Laurent Ahiablame
▪ Utsav Thapa
▪ Cynthuja Partheeban
25

26. https://extension.sdstate.edu/tags/streamlines-podcast
Twitter – @SDSUExtWaterMan
Email – john.mcmaine@sdstate.edu

27. LONG-TERM
NITRATE REMOVAL
PERFORMANCE OF
FOUR DENITRIFYING
WOODCHIP
BIOREACTORS IN
EASTERN SOUTH
DAKOTA
John McMaine
Ag and Biosystems
Engineering