Influence of operating parameters on the performance of a continuously aerated SHARON reactor
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Eveline I.P. Volcke1, Mark C.M. van Loosdrecht2 and Peter A. Vanrolleghem1 1 Ghent
University, Department of Applied Mathematics, Biometrics and Process Control (BIOMATH), Coupure Links 653, B-9000 Gent, BELGIUM 2 Delft University of Technology, Department of Biochemical Engineering, Julianalaan 67, NL-2628 BC Delft, THE NETHERLANDS
Introduction
The SHARON model
The SHARON-Anammox process
Implemented in Matlab 6.1-Simulink 4.1
The combined SHARON-Anammox process is a promising process for biological nitrogen removal from ammonium-rich wastewater (~1gNH4-N/l).
Consists of • 16 liquid phase mass balances • 5 biological conversion processes in liquid phase • 3 gas phase mass balances • diffusion processes between gas and liquid phase
Advantages compared to conventional nitrification-denitrification: • savings on aeration energy (63%) • no need for carbon source addition • low sludge production 1 CO2 1 NH4+
0.5 NH4+
1 HCO3-
0.5 NO2-
0.75 O2
SHARON
0.5 N2
Anammox
The optimal nitrite/ammonium ratio (1/1 in theory) in the Anammox influent should be produced by the SHARON process.
pH effects are very important ⇒ chemical equilibria are considered & lumped components are defined: H2O ↔ H+ + OHNH4+ ↔ NH3 + H+ TNH = NH4+ + NH3 HNO2 ↔ H+ + NO2TNO2 = HNO2 + NO2CO2 + H2O ↔ H+ + HCO3HCO3- ↔ H+ + CO32TIC = CO2 + HCO3- + CO32assume steady state
The SHARON process • completely stirred tank reactor (CSTR) + − − • high temperature (~35°C) ⇒ NH 4 → NO 2 → NO 3 • short retention time (~1day) • protons produced during nitrification are neutralized through CO2 stripping In theory:
HCO3 − 1 IF = + NH 4 influent 1
NO 2 − 1 THEN = + NH 4 produced 1
From the charge balance in the reactor: - H+ + OH- - NH4+ + NO2- + NO3- +HCO3- + 2 CO32- - Z+ = 0 the pH and corresponding equilibrium concentrations are calculated.
In practice: The produced nitrite/ammonium ratio is influenced by a number of factors.
Objective Perform a simulation study to examine the influence of operating parameters on the nitrite/ammonium ratio produced by the continuously aerated SHARON process
Simulation results Steady state simulation results for the behaviour of the continuously aerated SHARON system are presented (influent TNH = 70 mole m-3).
7.5
30
7
20
6.5
10
6
0
5.5 0.5
1
1.5
2
2.5
50 40
TNH TNO2 NO3 pH
TNO2/TNH = 1/1
30 20 10 0 0
10
20
30
40
50
60
70
80
8 7.9 7.8 7.7 7.6 7.5 7.4 7.3 7.2 7.1 7 6.9 6.8 6.7 6.6 6.5
70
50 40 TNO2/TNH = 1/1
30 20 10 0 6
90 100 110 120 130 140
8 7.9 7.8 7.7 7.6 7.5 7.4 7.3 7.2 7.1 7 6.9 6.8 6.7 6.6 6.5
SRT = 0.67 days TICin = 70 mole m-3
TNH TNO2 NO3 pH
60
6.5
-3
7
7.5
8
8.5
pH
8
40
SRT = 0.67 days influent pH = 7.8
60
Influence of the influent pH concentrations [mole m-3]
8.5
concentrations [mole m-3]
50
70
9
influent pH = 7.8 TICin = 70 mole m-3
TNH TNO2 NO3 pH
60
pH
concentrations [mole m -3]
70
Influence of the influent TIC concentration
pH
Influence of the sludge retention time
9
influent pH
TICin [mole m ]
SRT [days]
0.65 d-1 < SRT< 1.6 d-1 to establish partial nitrification TNO 2 resulting is hardly influenced TNH in this operating region
−
HCO 3 !⇒ TIC TNO 2 buffer capacity ! ⇒ ! TNH
influent TIC ! ⇒ HCO3- ! ⇒ TNO 2 buffer capacity ! ⇒ ! TNH
influent pH ! ⇒
Conclusions TNO 2 The ratio produced by the SHARON process hardly varies with varying SRT, but is highly influenced by the buffer capacity of the influent, TNH
that varies with influent pH and TIC concentration.
TAKE HOME MESSAGE _____________________________________________________________________________________________________________________________________________________________________________________________________________________________________
• For efficient realization of the combined SHARON-Anammox system, it is crucial to control the
TNO 2 ratio produced by the SHARON process TNH
• Operating parameters influencing the buffer capacity of the SHARON system are suitable control handles
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