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Eco-friendly and Energy Efficient Biological
Nitrogen Removal Process with Minimal Green
House Gas Emissions
Chitta Ranjan Behera1,Babji Srinivasan1, Kartik Chandran2,
Venkat Venkatasubramanian3
1 Department of Chemical Engineering, IIT Gandhinagar2 Department of Earth and Environmental Engineering, Columbia University
3Department of Chemical Engineering, Columbia University
1
Outline
BNR process and its Importance• Under line mechanism
Nitrification process using autotrophic AOB• Multiple Pathways for N2O Production
• Model for AOB in Oxic and Anoxic conditions
Simulation of proposed model• Continuous Aerobic Bioreactor
Observability test and State estimation • Implementation of Extended Kalman Filter (EKF)
Model Predictive Controller (MPC)• Control based on optimization approach
• Constraints handling
2
No Oxygen Supply
Importance of Nitrogen Removal
Total nitrogen to an average level of 8 to 10 mg/L should maintain before being discharged into a receiving water
Industry Range of NH4+
(mg/L or ppm)
Cokery 3300-4100
Oil refinery 450-630
Coal < 2500
Fertilizer 200-940
Diary < 625
Pharmaceuticals < 475
Wiesmann, U. (1994)
N2
NH4+
NO2-
NO
N2O
NO3- 3
Eutrophication Blue baby Syndrome Fish Killing
De-nitrificationOxygen Supply
No
indication
of N2O
Oxygen Supply
New metabolic pathways for N2O and NO production in AOB supported by quantitative proteomics
Yu et al., 2010, ES&T4
No Oxygen Supply
N2O Formation
NH3
NH2OH
HNO2
NO N2O
NO N2O
AMO
HAO
HAO Nor
NirK Nor
CytL
O2
H2O
• Under O2 limiting condition,alternate electron acceptors (NO2
-)and donors (unionized NH3 ) toproduce significant amounts of N2Oand NO. (using NirK and Nor)
• Nitrifier dentrification and Nitrogen-dependent are ways for N2Oproduction in AOB
Chandran et al., 2011 BST
Impact of O2 limitationImpact of excessive transient NH3 and O2
Impact of Normal NH3 loading
5- - - - - >
Medium Scale
Large Scale
Small Scale
Greenhouse gas footprint at Kralingseveer WWTP
U.S. Nitrous Oxide Emissions, 1990-2011 U.S. Carbon Dioxide Gas Emissions, 1990-2011
http://www.epa.gov/climatechange/ghgemissions/gases/co2.html
Daelman et al. (2013)
6
Simulation result
7Anoxic Region Oxic Region
Observability
StateMeasurement
Model Measurements from
sensors
Unobserved states
(Oxic region)
Unobserved states
(Anoxic region)
1NH4
+, Dissolved O2
NH4+, Dissolved O2, NO2
-
NH4+, Dissolved O2 ,NO
NH4+, Dissolved O2 ,N2O(l)
1
1
1
0
1
1
1
0
2
NH4+
NH4+, NO2
-
NH4+ ,NO
NH4+,NH2OH
NH4+ ,N2O(l)
11110
11110
• DO• NH3
• NH3
• DO• XNS
• NO2
• NO• N2O(l)
8
Model
How to estimate other states by
TWO measurement ??
It is a measure for how well internal states of a system can be infer by knowledge of its external output.
1 1 1k k k k
k k k
x Ax Bu w
z Hx v
State Observer…
Assumptions
Welch, Greg (1995).
Kalman Filter
System model equation
9
Extended Kalman Filter
Updation
System model equation
Prediction
EKF is the nonlinear version of Kalman filter which linearizes about an estimate of the current mean.
EKF based on 1st order linearization
Remarks• It has no optimality guarantee.• Resulting error from linearization may cause estimate divergence.
Simon, D. (2006)
10
State Estimation by EKF
11Anoxic Region Oxic Region
12Anoxic Region Oxic Region
Model predictive control(MPC)
MPC is based on iterative, finite horizon
optimization of a plant model.
Look ahead Plan Control Correct
1 2
3 3 rate
2 2 2
1 2 rate 3 rate
1 0 0
ˆmin ( ( ) ( )) ( ( )) ( ( ))aeration
M MP
SNH NH aerartion aerationu
j j j
J w y k j y k j w u k j w u k j
2 max
max
min rate max
0
0
aeration rate
aerat
O
on
N
i
u u
u
y
u u
y
Constraint:
Cost function:
13
Energy efficiency
NH3Objective
• Ni, B.-J., Z. Yuan, K. Chandran, P. Vanrolleghem and S. Murthy, 2013 “Evaluating four mathematical models for
nitrous oxide production by autotrophic ammonia-oxidizing bacteria”,Biotechnology and
Bioengineering, 110(1), 153-163.
• Chandran, Kartik, et al. "Nitrous oxide production by lithotrophic ammonia-oxidizing bacteria and implications for
engineered nitrogen-removal systems."Biochemical Society Transactions 39.6 (2011): 1832. IPCC. 2011.
• Welch, Greg, and Gary Bishop. "An introduction to the Kalman filter." (1995).
• Garcia, Carlos E., David M. Prett, and Manfred Morari. "Model predictive control: theory and practice—a
survey." Automatica 25.3 (1989): 335-348.
• Yu, R., M. Kampschreur, M. C. M. van Loosdrecht and K. Chandran*, 2010 “Mechanisms andspecific directionality
in autotrophic nitrous oxide and nitric oxide generation during transient anoxia” Environmental Science and
Technology, 44(4), 1313-1319
References:
Future direction…
• Validation and model improvement using
more experimental data and process
knowledge
• Nonlinear MPC for BNR to sustain both
nitrification and de-nitrification in a single
process train with emphasis on N2O
production
14
Nonlinear MPC for BNR
THANK YOU…
15