The Potential of Using Biological Nitrogen Removal Technique for
Stormwater Treatment
May 18, 2017
Yewei Sun, PhD StudentZhi‐Wu Wang, Assistant Professor
Sustainable Environment Research Laboratory
The Charles E. Via, Jr. Department of Civil & Environmental Engineering
Agenda
The Charles E. Via, Jr. Department of Civil & Environmental Engineering
Introduction
Material and Methods
Results
Discussion
The Potential of Using Biological Nitrogen Removal Technique for Stormwater Treatment
Introduction: Background
“Dead Zones”
https://nofishleft.wordpress.com/tag/marine‐dead‐zones/
What is “Dead Zones”? -----NO FISH!!
Introduction Material and Methods Results Discussion
Introduction: Background
Increased
• Urbanization• Climate Change
Increased
• Stormwater Runoff• Nitrogen Pollutant
Formed• “Dead Zones”
“Dead Zones” Formation
Introduction Material and Methods Results Discussion
Introduction: Biological Nitrogen Removal (BNR)
What is Biological Nitrogen Removal (BNR)?
Introduction Material and Methods Results Discussion
Introduction: BNR for stormwater
Biological Nitrogen Removal
Introduction Material and Methods Results Discussion
Applications Models
ASM1ASM2ASM3CWM1
High affinity of BNR communities to
nitrogen pollutants
Applicability of wastewater BNR models to low nitrogen concentration environment
Introduction: BNR for stormwater
Stormwater Characteristics (National Stormwater Quality Database)
TKN TN
BOD5 NOX (TN‐TKN)
Introduction Material and Methods Results Discussion
Material and Methods: Model development
Bioretention System
Introduction Material and Methods Results Discussion
Biofilm
Soil
Pore Water
Biofilm ThicknessConfocal image from Meherunnesha et al. (2008)
Material and Methods: Model development
Bacterial Model
• Five substrates in the liquid phase• Dissolved oxygen (DO) • Nitrate (NO3
-)• Nitrite (NO2
-)• Ammonium (NH4
+)• Biodegradable organic carbon source expressed as chemical oxygen
demand (COD)
• Three types of autotrophic bacteria• Ammonia-oxidizing bacteria (AOB)• Nitrite-oxidizing bacteria (NOB)• Anammox bacteria (AMX)
• Three types of heterotrophic bacteria• Oxygen-respiring heterotroph (ORH)• Nitrite denitrifier (NID)• Nitrate denitrifier (NAD)
Introduction Material and Methods Results Discussion
Material and Methods: Model development
Plant Model
• Capability of assimilating both NH4+ and NO3
-
• Nitrogen is only temporarily stored in plant and will be eventually released back to the downstream water at their death and decay.
• Since this study focused on biological nitrogen removal and plant assimilation will reach its limit soon, plant nitrogen uptake was only considered in model calibration and validation.
Introduction Material and Methods Results Discussion
Material and Methods: Model kinetics
Introduction Material and Methods Results Discussion
Material and Methods: Model calibration and validation
0
2
4
6
8
10
0 10 20 30
Am
mon
ium
C
once
ntra
tion
(g N
m-3
)
Time (hour)
Experimental DataModel Simulation
R2=0.99
0
2
4
6
8
10
0 10 20 30
Nitr
ate
Con
cent
ratio
n (g
N m
-3)
Time (hour)
Experimental DataModel Simulation
R2=0.98
Model Calibration
Model Validation
0%
20%
40%
60%
80%
100%
experi
ment
model
Nitr
ate
fate
(a) 0%
20%
40%
60%
80%
100%
experi
ment
model
(b) 0%
20%
40%
60%
80%
100%
experi
ment
model
(c)
Literature data from Payne et al. (2014)
Introduction Material and Methods Results Discussion
Results: Effect of HRT on steady-state NH4+ and TN removal efficiencies
• 0.5 days HRT should be sufficient for stormwater NH4+ removal.
• TN removal efficiency improves along with the increase of stormwater reducing power (NH4
+ and COD).• The contribution of AMX to TN removal increases along with the increase of
stormwater reducing power (NH4+ and COD).
0%
4%
8%
12%
16%
20%
60%
70%
80%
90%
100%
0 0.5 1 1.5 2
TN
rem
oval
eff
icie
ncy
NH
4+ rem
oval
eff
icie
ncy
HRT (day)
(a)
0%
4%
8%
12%
16%
20%
60%
70%
80%
90%
100%
0 0.5 1 1.5 2
TN
rem
oval
eff
icie
ncy
NH
4+ rem
oval
eff
icie
ncy
HRT (day)
(b)
0%
4%
8%
12%
16%
20%
60%
70%
80%
90%
100%
0 0.5 1 1.5 2
TN
rem
oval
eff
icie
ncy
NH
4+ rem
oval
eff
icie
ncy
HRT (day)
(c)
0%
4%
8%
12%
16%
20%
60%
70%
80%
90%
100%
0 0.5 1 1.5 2
TN
rem
oval
eff
icie
ncy
NH
4+ rem
oval
eff
icie
ncy
HRT (day)
(d)
Low NH4+
High COD High NH4+
High COD
Low NH4+
Low COD High NH4+
Low COD
Black: NH4+
removal
Green: TN removal with AMX
Red: TN removal without AMX
Introduction Material and Methods Results Discussion
Results: Substrate distribution in biofilm
• COD can be oxidized within the top 50 µm layer in the biofilms.• NH4
+ oxidation occurs further inside biofilm beneath the layer where COD oxidation occurs.• The extent of NH4
+ oxidation depends on the penetration of remaining DO.
Dark blue: NH4+
Green: NO2-
Purple: NO3-
Blue: COD
Maroon: DO
2.178
2.182
2.186
2.190
2.194
2.198
0.00
0.05
0.10
0.15
0 100 200 300
NO
3- -N (g
m-3
)
N (N
H4+ ,N
O2- ),
DO
, CO
D
(g m
-3)
Lf (µm)
(d)
1.254
1.258
1.262
1.266
1.270
1.274
0.00 0.03 0.06 0.09 0.12 0.15 0.18
0 300 600 900
NO
3- -N (g
m-3
)
N (N
H4+ ,
NO
2- ), D
O, C
OD
(g
m-3
)
Lf (µm)
(b)
0.6
0.8
1.0
1.2
1.4
0.00
0.04
0.08
0.12
0.16
0 200 400 600 800
NO
3- -N, D
O (g
m-3
)
N (N
H4+ ,
NO
2- ), C
OD
(g
m-3
)
Lf (µm)
(a)
0.0
1.0
2.0
3.0
4.0
5.0
0.00
0.02
0.04
0.06
0.08
0 50 100 150 200
NO
3- -N, D
O (g
m-3
)
N (N
H4+ ,N
O2- ),
CO
D
(g m
-3)
Lf (µm)
(c)
Low NH4+
High COD
Low NH4+
Low COD
High NH4+
Low COD
High NH4+
High COD
Introduction Material and Methods Results Discussion
Results: Bacteria distribution in biofilm
• Heterotroph, AOB and NOB predominate the top layers of biofilms where COD and DO are depleted.
• AMX only grow deep inside the biofilms where COD and DO are lean but NO2- and NH4
+ are affluent.
• Only stormwater with a relatively high reducing power (NH4+ and COD) offers the possibility to
cultivate biofilms with an anoxic local environment for AMX prosperity.
0
2000
4000
6000
8000
0 400 800
1200 1600 2000 2400
0 100 200 300
Het
erot
roph
, Ine
rt
(g C
OD
m-3
)
AO
B, N
OB
, AM
X
(g C
OD
m-3
)
Lf (µm)
(d)
0
3000
6000
9000
0
400
800
1200
1600
2000
0 300 600 900
Het
erot
roph
, Ine
rt
(g C
OD
m-3
)
AO
B, N
OB
, AM
X
(g C
OD
m-3
)
Lf (µm)
(b)
0
3000
6000
9000
0
25
50
75
0 200 400 600 800
Het
erot
roph
, Ine
rt
(g C
OD
m-3
)
AO
B, N
OB
, AM
X
(g C
OD
m-3
)
Lf (µm)
(a)
0
3000
6000
9000
0
30
60
90
0 50 100 150 200
Het
erot
roph
, Ine
rt
(g C
OD
m-3
)
AO
B, N
OB
, AM
X
(g C
OD
m-3
)
Lf (µm)
(c)
Low NH4+
High COD
Low NH4+
Low COD High NH4+
Low COD
High NH4+
High CODDark blue: AMX
Purple: NOB
Maroon: AOB
Green: Inert
Blue: Heterotroph
Introduction Material and Methods Results Discussion
Results: Effect of COD on BNR
• TN keeps decreasing to almost zero as the influent COD increases to a threshold COD value (COD*).
• Continuous increase of influent COD will result in increase of TN and effluent COD concentration.
Dark blue: NH4+, Green: NO3
-, Maroon: NO2-, Purple: TN, Blue: COD
0
2
4
6
8
10
12
14
0
0.4
0.8
1.2
1.6
2
2.4
0 10 20 30 40
Eff
luen
t CO
D (g
m-3
)
N (g
m-3
)
COD (g m-3)
(b) Threshold COD*
Introduction Material and Methods Results Discussion
Results: BNR at COD*
Dark blue: AMX
Purple: AOB
Blue: NOB
Maroon: NID
Green: NAD0
10
20
30
40
50
60
70
80
0
2
4
6
8
10
12
14
0 200 400 600 800
N tu
rnov
er r
ate
by
NID
and
NA
D (g
m-3
d-1
)
N tu
rnov
er r
ate
by
AO
B, N
OB
, AM
X (g
m-3
d-1
)
Lf (µm)
(a)
Two major characteristics of BNR at COD*:
i) Majority (90%) of nitrogen (NH4+ or NO3
-) is removed through AMX while only 10% through NID.
ii) Only partial nitritation occurred with no need of NOB. Therefore, the primary BNR pathway at COD* is through partial nitritation and AMX for the least COD consumption.
Introduction Material and Methods Results Discussion
Results: BNR at COD*
COD* must be provided to enable the co-existence of aerobic and anoxic conditions required by BNR.
• COD < COD* leads to BNR failure because of the inadequate reducing power (NH4
+ and COD) for anoxic condition establishment.
• COD > COD* causes insufficient NH4+ nitrification due to inadequate DO
remains for AOB after COD oxidation.
0
2
4
6
8
10
12
14
0
0.4
0.8
1.2
1.6
2
2.4
0 10 20 30 40
Eff
luen
t CO
D (g
m-3
)
N (g
m-3
)
COD (g m-3)
(b)
Dark blue: NH4+
Green: NO3-
Maroon: NO2-
Purple: TN
Blue: COD
Introduction Material and Methods Results Discussion
Discussion: Stoichiometric estimation of COD*
Introduction Material and Methods Results Discussion
Exemplary
ratio
Percentage of nitrogen being removed by different pathways
Denitrification AMX Bacterialuptake Residual
Scenario 1 2.50 6.6% 84.3% 9.1% 0.0%
Scenario 2 0.50 61.3 10.0% 28.7 0.0%
Scenario 3 0.30 35.3% 0.0% 23.1% 41.6%
• Three scenarios can be generalized for stormwater BNR with regard to COD* demand.
Fraction of U.S. stormwater runoff in NSQD with NH4+-N to NO3
--N ratio under scenario
1 (blue), scenario 2 (orange), and scenario 3 (green)
71.10%
19.30%
9.60%
Discussion: Stoichiometric estimation of COD*
• About 9.6% stormwater events in National Stormwater Quality Database (NSQD) are subjected to NH4
+ limitation (scenario 3).
Introduction Material and Methods Results Discussion
Discussion: Stormwater COD availability for BNR
0
1
2
3
4
5
0 0.5 1 1.5 2 2.5 3
NH
4+ -N
(g m
-3)
NO3--N (g m-3)
(a)
0
10
20
30
40
50
0 10 20 30 40 50
BO
D5 (
g m
-3)
COD* (g m-3)
(b)
• 82.6% U.S. stormwater in NSQD contains BOD5 lower than COD* required for complete BNR.
• Vegetation planted in the topsoil of bioretention system may release some COD.
• The slow COD-releasing biofilm carriers developed in recent years may be applied as an alternative for COD supplementation.
(a) BOD5 : (black circle size) COD* (red circle size)
(b) BOD5 vs COD* plot
Introduction Material and Methods Results Discussion
Discussion: Importance of AMX for stormwater BNR
• COD* without AMX can be two-fold higher than the COD* with AMX. • BNR efficiency can be significantly compromised without AMX, which is true
especially at higher S : S ratio.
NO3- (g N m-3) = 0.5 (black)
1 (red)1.5 (orange)2 (green)2.5 (blue)3 (purple)
Solid line: with AMXDashed line: without AMX
Introduction Material and Methods Results Discussion
Discussion: Model limitations and future work
• Homogeneous condition was assumed in bioretention systems in which heterogeneous environment may exist.
• The effect of inter-event duration was not considered in current model development.
• Experimental validation of the mathematical model is needed in future work.
Validation study is being carried out in ourcollaborator’s (Dr. Changwoo Ahn) mesocosmcomplex in George Mason University
Introduction Material and Methods Results Discussion
Daily average rainfall graph in Goa, India (Jun to Sept. 2014)
http://weatheringoa.blogspot.com/2014/10/goa-monsoon-2014-analysis-happy-ending.html
• A mathematical model was for the first time developed tosimulate the spatial distribution of BNR activity in biofilmsgrowing on bioretention media for stormwater treatment.
• A threshold influent carbon source concentration (COD*) wasfound for maximizing BNR efficiency. Application of AMXcan significantly lower COD* and enhance BNR efficiency.
• 71.1% urban stormwater runoff contains adequate NH4+ for
both AMX and denitrification, 19.3% contains adequate NH4+
for denitrification but inadequate for AMX, while the NH4+
content in 9.6% urban stormwater is inadequate for neitherAMX nor denitrification.
Concluding remarks:
Introduction Material and Methods Results Discussion
The Charles E. Via, Jr. Department of Civil & Environmental Engineering
We would like to extend our sincerest thanks to 4-VA Competitive Research Grants and Sussman Internship funding for supporting this project.
Yewei Sun
PhD StudentOccoquan LaboratoryDepartment of Civil and Environmental Engineering, Virginia Tech9408 Prince William Street, Manassas, VA 20110-5670
Office: 703-361-5606 x 136 Fax: 703-361-7793 Email: [email protected]
The Potential of Using Biological Nitrogen Removal Technique for Stormwater Treatment