Denitrifying Bioreactor
Exploring N and P Sequestration in Bioreactors
Lu Zhang, Joe Magner, Gary Feyereisen, Rod Venterea, Bruce Wilson, John Nieber
Minnesota Water Resource ConferenceOct. 13th, 2015
N and P effects
http://www.breitbart.com/london/2015/02/09/global-warming-so-dishonest-it-makes-enron-look-like-a-paragon-of-integrity/
http://earthsky.org/earth/2011-gulf-of-mexico-dead-zone-smaller-than-scientists-predicted
http://savethewater.org/2012/07/14/usa-drinking-water-contamination-warning-iowa-perry-issued-a-drinking-water-warning-friday-nitrate-levels-high/
http://www.ecology.com/2011/11/01/paper-plastic-corn/ https://commons.wikimedia.org/wiki/File:Difference_DNA_RNA-EN.svg
Nutrient Reduction Strategy
DenitrificationNO3
− NO2− NO N2O N2
Phosphorus Reduction• Physical
– Filtration, membrane• Chemical
– Precipitation, adsorption• Biological
– EBPR
Bioreactor Advantages• Subsurface flow• Biostimulation• High reduction rate• Space
Bioreactor Locationshttp://artnsinks.apps.uri.edu/Atlas.html
Lab Study Design IDesign Schematic
• The two bioreactors simulatedhorizontal flow in the field with alength to width ratio of 16:1.
• The size of each bioreactor was0.98m (L) * 0.2m (W) * 0.67m (H).
• One had transparent sides toprovide view of the inside. Bothsides were covered with tarp toprevent light effect on microbialgrowth.
• Each chamber had two bafflesinside to guide the flow. Waterentered from the bottom on oneside and comes out from the topon the other side.
Lab Study Design I- continue Design Schematic
• Soil from the field site (mostlyClarion-Storden loams) was usedto cap the top. When water wasrunning, the soil on top wasalways saturated providinganaerobic condition inside.
• Nutrient water was prepared in thestorage tank and pumped into theoverhead tank. Six flow meterswere used to control the flow ratein each chamber.
• PVC containers were used tocatch outflow for nitrate probeuses.
Lab Study Design IIDesign Components
Variables• Alternative C sources: food source for
denitrifying bacteria– Woodchips- mix of hardwood– Biochar- “caramelized woodchips”– Corn cob
• Residence time – 24 and 8-hour
Controlled factors• Nitrate concentration: 21±1 ppm• Phosphorus concentration: 0.35±0.05 ppm• Temperature: around room temperature• Processes competing for available C:
oxygen availability
Biochar• Black carbon• Pyrolysis• Carbon sequestration-
slower cycling form• What we did-
caramelized woodchips
Lab Study MethodResearch Method
• Nutrient removal was evaluated by nitratereduction and phosphorus reduction.Nitrate concentration was measured on adaily-base. Orthophosphateconcentration was measured every threedays.
• Nitrous oxide production was measuredon a weekly base to determine the effecton greenhouse gases emission.
• The in-situ residence time will bedetermined by bromide tracer.
• Residence time was designed to be 24hours (50ml/min flow rate) for the first 3months and 8 hours (150 ml/min) for thenext 2 months.
• ANOVA test and student-t test were usedfor statistical analysis.
Lab Study- 24 hr N Reduction
Lab Study- 8 hr N Reduction
Nitrate-N Removal Summary
Nitrate-N removal rate stats
Nitrate-N removal rate stats cont.
Lab Study- 24 hr P reduction
Lab Study- 8 hr P reduction
Ortho-P removal rate stats
Ortho-P removal rate stats cont.
Lab Study- 24 hr N2O emission
Lab Study- 8 hr N2O emission
Summary• Woodchip: nitrate removal• Biochar: orthophosphate removal, N2O, longevity• Corn Cob: environmental resilience• Suggestion: multi-media treatment, combined
treatment system
AcknowledgementCommittee:• Joe Magner- Advisor• Gary Feyereisen• John Nieber• Bruce Wilson• Rodney Venterea
Funding:Minnesota Corn Growers
Association
Questions
Wetlands and Lakes Reduce Surface Water Nitrogen in Minnesota’s Agricultural Landscapes
Amy Hansen, Christy Dolph, Jacques FinlayUniversity of Minnesota
2015 Minnesota Water Resources Conference
Call for a 45% reduction in nitrogen loading to Mississippi River by 2045.
The Dead ZoneRobertson and Saad, 2011.
Total annual N yield
“Sides line up in Des Moines Water Works' nitrate lawsuit”
Source: Minnesota Pollution Control Agency, June 2013Nitrogen in Minnesota Surface Waters
Image from
microbew
iki.kenyon.edu
Denitrification Assimilation
Primary nitrate removal mechanisms
Can occur anywhere in surface water network. Occur at high rates in wetlands.
Image from
microbew
iki.kenyon.edu
Denitrification
Primary nitrate removal mechanisms
• Nitrate supply• Organic carbon
supply • Temperature• Oxygen status
Project questions
• What factors are limiting denitrification rates? Where? When?
• Does land use predict nitrate concentrations?
Le Sueur BasinJune, 2015
Chippewa, Cottonwood, Le Sueur BasinsJune, 2014
Basin spatial sampling
TDN = total dissolved nitrogen (~90% nitrate)DOC = dissolved organic carbon
0
10
20
30
0 500 1000 1500 2000 2500 3000 3500 4000
TDN
(mg/
L)
Drainage area (km2)
June 2015, Greater Blue Earth Basin
0
5
10
15
20
25
0 200 400 600 800 1000 1200 1400
DOC
(mg/
L)
Drainage area (km2)
June 2015, Le Sueur River Basin
Variability in ditches and streams
• Avg June tile• (2013-2015, n = 18)
• TDN = 20.6 mg/L• DOC = 3.4 mg/L
• June 2014, 3 basins• 72 sites• Drainage areas:
3 km2 to 5800 km2
• Crop land cover: 30% - 95%
Wetlands and lakes reduce nitrate
y = 19.7e-0.27x
R² = 0.57
0
5
10
15
20
25
30
0 5 10 15 20 25
Nitr
ate
(mg/
L)
% of drainage area that is lakes + wetlands
75% reduction in nitrate with 5% lakes and wetlands
0
5
10
15
20
25
30
0 20 40 60 80 100
Nitr
ate
(mg/
L)
% cultivated cropland
June 2014, 3 basins
Enhanced nitrate uptake or reduced inputs?
BOTH reduced inputs and enhanced uptake
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5
10
15
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25
30
82 84 86 88
Nitr
ate
(mg/
L)
% cultivated cropland
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5
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25
30
0 5 10 15
Nitr
ate
(mg/
L)
% lakes + wetlands
R2 = 0.38p = 0.003
y = 1.83x + 4.5R² = 0.66
0
5
10
15
20
25
0 2 4 6 8 10
DO
C (m
g/L)
% emergent wetlands (not lakes)
Le Sueur River Basin, June 2015
Emergent wetlands increase DOC
Ditch data
Nitrate over time
Nitr
ate
(mg/
L)
< 5% wetlands/lakes
5% to 20% wetlands/lakes
DOC over timeDO
C (m
g/L)
< 5% wetlands/lakes
5% to 20% wetlands/lakes
More dissolved organic carbon(non saturating) nitrate…
but
denitrification rates were not enhanced downstream of wetlands.
Why not? What, in intensively agricultural setting is limiting denitrification?
(temperature, organic carbon supply or nitrate supply)
Areal denitrification rates
0
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20
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40
50
60
70
80
0 5 10 15 20 25 30 35
Area
l den
itirf
icat
ion
rate
(mg-
N/m
2/hr
)
Nitrate (mg/L)
Upper bound on denitrification was well described as nitrate limited and matched results from USA study of 56 (less disturbed) streams (Mulholland et al 2008, Bohlke et al. 2009)
0
10
20
30
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50
60
70
80
0 10 20 30
Area
l den
itirf
icat
ion
rate
(mg-
N/m
2/hr
)
Nitrate (mg/L)
Areal denitrification rates
Spring denitrification rates
(water temperature is a secondary control, after N and C)
R² = 0.25p = 0.01
0
5
10
15
20
25
30
35
40
45
0 5 10 15 20
Area
l den
itirf
icat
ion
rate
(mg-
N/m
2/hr
)
DOC (mg/L)
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60 70
Nitr
ate
(mg/
L)
DOC (mg/L)
Nitrate supply limited DENDOC supply limited DEN
DOC:NO3 = 2 (molar)
Limiting resource switches
Nitrate limitedOrganic carbon limited
Applying limit switching to basin
Conceptualization of changes along reach
Nitrate
DOC
Maximum denitrification
rate
x, distance downstream
No wetland
Conceptualization of changes along reach
Nitrate
DOC
Maximum denitrification
rate
x, distance downstream
No wetlandWetland at x = 0
DOC:NO3 = 2
• Current land use are not resulting in a significant change on the basin scale (outlet concentrations ~ tile outlet concentrations)
• 75% reduction in nitrate concentration with 5% wetland/lake land use
• Denitrification rates are limited by organic carbon supply OR nitrate (limit switching)
• Opportunity to optimize placement of treatment wetlands by considering specific limiting resource
Conclusions
Field and laboratory assistance from:Adam Worm, Ailsa McCulloch, Allison Acosta, Andrea Keeler, Abby Tomasek, Ben Janke, Brent Dalzell, Erika Senjk, Evelyn Boardman, Jon Schwenk, Katie Kemmit, LeAnn Charwood, Maria Roubert, Morgan Andreson, Nick Omodt, Nolan Kleinjan, Sandy Brovold, Shelly Rorer, Vincent Knox
Funding: • NSF grant EAR-1209402 under the Water Sustainability and Climate Program
(WSC): REACH (REsilience under Accelerated CHange)
• NSF grant SEES-1415206 under the Water Sustainability and Climate Program (WSC): SEES Fellows: Leveraging the waterscape to increase agricultural landscape sustainability
Contact:Amy Hansen
Contributors and funding
Internal wetland sampling
Lost Marsh Wetland281 acres
Emergent vegetationConstant depth (~ 0.3 m)
Maple River Wetland116 acres
Emergent vegetation/open waterVarying depth (max ~ 1.5 m)
0
5
10
15
20
25
30
0 10 20 30 40 50 60
Nitr
ate
(mg/
L)
DOC (mg/L)
4 sample events• Inlet streamflow: 6 to 160 L/s• Data from 2 wetlands which
vary in:• Vegetative cover• Water depth• Surface area
• June-July 2015
DOC-NO3- coupling
Tight coupling of N:C suggests resource stoichiometric control of N uptake
Nitrogen Reduction in a Constructed Wetland and Wetland MesocosmsBrad Gordon, Josh Gamble, Chris Lenhart, Dean Current, and Nikol RossUniversity of MinnesotaOctober 13, 2015
Martin County
Overview• Introduction
• Objectives• Location• Design
• Methods• Results
• Nutrient Reduction Efficiency• Water Retention
• Mesocosm Experiment
Objectives• Assess effectiveness of an on-farm, edge-of-field, treatment
wetland in removing nitrogen (nitrate) and phosphorus (total phosphorus and orthophosphorus) from tile drainage water
• Assess biomass production and nutrient uptake of wetland vegetation to determine potential for bioenergy production and contribution to nutrient removal
• Determine the role of ecological components (soil and vegetation) in removing nitrogen from tile drainage water using wetland mesocosms
Location - Blue Earth River Basin
Roberts’ Farm
Constructed Wetland Design
• Three cell design• Separated by berms
• Water supplied from tile drainage
Total wetland: 0.54ac Each treatment cell: 45ft x 87.5ft (0.09ac) Total active treatment
0.27 ac
Soil Properties• All three cells > 40% clay• 2.0-2.77 % TOC
Soil Texture Analysis - Hydrometer Method
Sample ID
Sand(%)
Silt(%)
Clay(%)
TOC( % C )
Total N( % N ) C/N Ratio
Darwin's Wetland - Cell 1 (2013) 9.9/12.6 43.8/41.2 46.3/46.2 2.0-2.77%
Darwin's Wetland - Cell 2 5.0 53.8 41.3 2.0-2.77%
Darwin's Wetland - Cell 3 8.7 45.0 46.3 2.0-2.77%
Darwin's Wetland –Cell 1 (2014) 25.0 28.8 46.3 2.07 0.150 13.77
Corn field
Agri-Drain 1
Agri-Drain 2
Agri-Drain 3/ Outlet
Tile Drainage Inlet
• Level logger
• Level logger
• Area Velocity probe
• Area Velocity probe
Groundwater Well
Groundwater Well• Level logger• barometer
Drainage Area• 25 acres• Land Use History
• Drainage area farmed since before 1930’s
• West half of wetland farmed with row crops since around 1960
• East half has remained natural vegetation
70-acre restored pothole basin, 2004
Size of treatment wetland = 0.5 acre, 2013
Vegetation Biomass & composition
0
1
2
3
4
5
Cell 1 Cell 2 Cell 3 Cell 1 Cell 2 Cell 3
2013 2014
Mg
Ha-1
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Cell 1 Cell 2 Cell 3C4 grasses C3 grassesForbs Reed Canary grassOther weeds
Vegetation Mineral uptake
0
5
10
15
20
25
N P
Kg H
a-1
2013 Cell 1 2013 Cell 2 2013 Cell 32014 Cell 1 2014 Cell 2 2014 Cell 3
0
5
10
15
20
25
30
35
40
45
Kg H
a-1
NP
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
Inlet AgriDrain 1 AgriDrain 2 Outlet
Volu
me
(m3 )
2014 Water Volumes
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
Inlet AgriDrain 1 AgriDrain 2 Outlet
Volu
me
(m3 )
2013 Water Volumes
2%
74%
6%
18%
2013 Water Volume Outflow Distribution
ET Infiltrated Ponded Outlet
22%
9%69%
2014 Water Volume Outflow Distribution
Surface Outflow ET Infiltration
June 2014 Flood
0123456789
10
Out
flow
(m3 /
15 m
inut
es)
2014 Outflow
0123456789
10
2014 Tile Inflow and Rainfall
Tile Inflow Volume(m^3/15 minutes)Daily Rainfall (inches)
Backflow observedduring flood
Reducing Peak Discharge
Lower flow in mid-late summer creates drier conditions than many constructed wetlands
2013 NO3-N removal• Limited vegetation cover• 356.7-377.2 lbs nitrate/nitrite-N
entered the wetland• ~39% (28-40%) Total Reduction (~143 lbs)
23%
38%1%
38%
0%Fate of Nitrogen in Wetland
Surface OutflowSubsurface OutflowSurface RemovalSubsurface RemovalPlant Uptake
2014 NO3-N removal• 379.0-647.6 lbs nitrate/nitrite-N
flowed into the wetland.• ~51% (45-61%) Total Reduction (~240 lbs)
18%
32%17%
32%
1% Fate of Nitrogen in Wetland
Surface OutflowSubsurface OutflowSurface RemovalSubsurface RemovalPlant Uptake
0
0.5
1
1.5
2
2.5
2013 2014
Ort
hoph
osph
ate
(lbs.
)
Orthophosphate Reductions
InflowOutflow
76-86%Reduction inSurface flowOrthoP
Can it Reduce Phosphorus Discharge?
Can it Reduce Phosphorus Discharge?
0
0.5
1
1.5
2
2.5
3
2013 2014
Tota
l Pho
spho
rus (
lbs.
)Total Phosphorus Reductions
InflowOutflow
68-69%ReductionIn surfaceflow Total P
Groundwater Measurements
Soil, Microbes, and Vegetation
Wetland Mesocosms• Study impacts of soil and vegetation on nitrogen reduction
• 3 wetland soils (remnant, 10-15 years old, 2 years old)• 3 wetland plant species (fringed sedge, cattail, reed canary grass)• DNA analysis of denitrifying microbes
0
100000000
200000000
300000000
400000000
500000000
600000000
nosZ
Den
sity
(cop
ies/
g so
il)Denitrifying DNA in Various Wetland Soils
2 Years Old 10-15 Years Old Remnant
0
10
20
30
40
50
60
70
80
90
100
DarwinNo Veg
KittlesonNo Veg
KittlesonSedge
KittlesonReed
Canary
Sarita NoVeg
SaritaSedge
SaritaReed
Canary
Perc
ent N
itrog
en R
educ
tion
Wetland Source + Plant Species
Mesocosm Nitrate Reductions
2 Years Old
10-15 Years Old Remnant
Conclusions• Infiltration and subsurface flow may play a large
role in nutrient reduction• Peak discharge to the creek is significantly
reduced during rain events• Surface water reduction of nitrogen improves
after the first growing season (1 to 17%)• These systems may work well in reducing
phosphorus discharged from tile drains• Microbial establishment may take >2 years• Managers must decide whether reed canary
grass is acceptable
Discussion• >50% N reduction is similar to other, larger
constructed wetlands but less than restored.• Can the easier adoption lead to more acres of
treatment wetlands and more reductions in total?• Can multiple reductions of ~240 lbs. N add up?
• Could the vegetation be used for biofuels?• How important is biodiversity in these wetlands?
Acknowledgements• Minnesota Department of Agriculture
• Heidi Peterson & Scott Matteson• Clean Water Fund• Martin Soil and Water Conservation District• Darwin and Sandy Roberts• University of Minnesota Faculty (BBE & Agronomy
departments)• Student assistants
