PERIODIC CONTROL OF A WASTEWATER TREATMENT PROCESS

TO IMPROVE PRODUCTIVITY MUHAMMAD RIZWAN AZHAR

KING SAUD UNIVERSITYSaudi Arabia

Introduction Process description Periodic control RobustnessConclusion

Outline

Usually refer to sewage treatmentRemoval of containments from wastewaterActivated sludge processAerobic/anaerobic

Introduction

Process Description

ReactorV, S, X SettlerD, S i X , S S

WDUD, X r , S

Well mixed unitsWell aerated reactorXi = 0No reaction in settlerNo settler dynamicsIdeal settler: Xout = 0

Process modelAssumptions

Optimal Operating Conditions

Variation of Steady State with Dilution rate; dotted: Biomass (X), dashed: Substrate (S), solid: Productivity (Pr)

Application Concept of MPC

PlantMPC

Model+

-

+

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yp

ym

u

x

er

Control Objective

Controlled Variables:ProductivityPr=D(1-S) i.e. amount of waste water treated

Manipulated Variables:Dilution rate D

Periodic forcing the input DRobustness in presence of

Modeling error External disturbance rejection

Control objective

Enhanced productivity in terms of substrate consumption

10 % increase than the maximum productivity in case steady state

Controller performance

Variable feed quality in WWTP Closed loop response for -25% error in Y, 10% error µ and

-10% step change in K

Robustness (Tracking modeling errors)

Regulatory performance 10 % increase in substrate concentration

Robustness (External disturbance)

10 % increase beyond the maximum productivity when periodic operation is enforced via MPC

Robust controller in presence of modeling errors and external disturbances

Less energy consumption as the fluctuation rate is kept within xx% (need to ad some numbers here)

Economically feasible (you should explain how in words)

Conclusion

Questions