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)

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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

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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)

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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

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Nonlinear MPC for BNR

THANK YOU…

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