Minimising energy consumption for aeration in activated ......Bubble size Mixers thrust Velocity of...
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www.irstea.fr To better reflect its missions, Cemagref becomes Irstea Y. Fayolle 1 , O. Brémond 2 , A. Cockx 3 , D. Legendre 4 , M. Fahlgren 5 , L. Uby 5 , C. Ramel 5 , D. Marchand 2 , D. Kuntz 2 , S. Gillot 1 16 th International Symposium Water, Wastewater, Solid Waste, Energy May 8th, 2012 Minimising energy consumption for aeration in activated sludge systems: Results from the O 2 STAR project 1 2 3 4 5
Transcript of Minimising energy consumption for aeration in activated ......Bubble size Mixers thrust Velocity of...
www.irstea.fr
To better reflect its missions, Cemagref becomes Irstea
Y. Fayolle1, O. Brémond2, A. Cockx3, D. Legendre4, M. Fahlgren5, L. Uby5, C. Ramel5, D. Marchand2, D. Kuntz2, S. Gillot1
16th International Symposium Water, Wastewater, Solid Waste, Energy May 8th, 2012
Minimising energy consumption for
aeration in activated sludge systems:
Results from the O2 STAR project
1 2 3 4 5
$$$$$ $ $
PrimaryTreatment Clarifier
Aeration Tank
Context and objectives - Aeration in wastewater treatment
Aeration could represent up to 70% of the total energy expenditure
Optimisation is required:
To reduce operating costs
To guaranty a reliable and efficient treatment
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
Closed – loop reactors (commonly installed in Europe)
Mixing
Sequenced aeration (nitrification / denitrification)
Fine bubble aeration
Axial slow speed mixers
Good oxygenation performances
Context and objectives - Aeration in wastewater treatment
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
Context and objectives – the O2 STAR Project
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
A 3-year (2008 – 2011) industrial research project funded by the French National Research Agency (ANR)
Main objectives:
Development of a software tool to design and optimise aeration systems installed in aerobic bioreactors (clean water)
Based on in situ measurements and CFD modelling
For wastewater treatment builders, engineering consulting companies, equipment manufacturers and operators
Context and objectives – the O2 STAR Project
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
Irstea (coordinator)
• In situ measurements
• CFD modeling
Xylem
• Development of mixers models
• In situ mixing characterisation
INSA Toulouse (LISBP)
• Local mass transfer measurements
• CFD and 1-D modeling
Degrémont – France Assainissement
• Making available aeration tanks
• Participation to in situ measurements
IMF Toulouse (Fluid dynamics Institute)
• Development of local mass transfer models
• 1-D modeling
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
Local simulation of oxygen transfer
Local measurement of oxygen transfer
On site measurements (Mixing/flows/mass transfer)
Mixing model development
3-D models development (Eulerian simulation – CFD)
1-D models development
Software tool O2 STAR development
Global scale Local scale
Context and objectives – A multi-scale approach
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
Local simulation of oxygen transfer
Local measurement of oxygen transfer
On site measurements (Mixing/flows/mass transfer)
Mixing model development
3-D models development (Eulerian simulation – CFD)
1-D models development
Software tool O2 STAR development
Global scale Local scale
Scientific and technical approach From local to global scale
Scientific and technical approach / Results
Analysis of the effect of the bubble deformation / flows characteristics on the oxygen transfer
Development of correlations that predict the local oxygen transfer (Figueroa and Legendre, 2010)
Characterisation of oxygen transfer around a bubble
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
Local measurement
Development of a planar laser induced fluorescence technique (PLIF) [François et al., 2011]
Measurement of oxygen in a cross-section of the bubble wake
Local simulation
CFD modelling
Direct simulation of flows and oxygen transfer
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
Local simulation of oxygen transfer
Local measurement of oxygen transfer
On site measurements (Mixing/flows/mass transfer)
Mixing model development
3-D models development (Eulerian simulation – CFD)
1-D models development
Software tool O2 STAR development
Global scale Local scale
Scientific and technical approach From local to global scale
Scientific and technical approach
Development of experimental methods for on site measurements
On site measurements
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
Bubble size Mixers thrust
Velocity of liqud
Scientific and technical approach
Development of experimental methods for on site measurements
To build up an experimental database on three full-scale reactors
On site measurements
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
Reactor 1 Reactor 3
Reactor 2
Scientific and technical approach
Development of experimental methods for on site measurements
To build up an experimental database on three full-scale reactors
On site measurements
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
Reactor 1
Reactor 3
Reactor 2
Reactors characteristics differs in :
Shapes (annular / oblong)
Size (1500 – 8400 m3) and water depth (5.4 – 8.1 m)
Characteristics and configuration of the mixing and aeration systems
Results
Impact of main parameters governing mixing and mass transfer in aeration tank on
Mixing characteristics
On site measurements
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
500
600
700
800
900
1000
1100
1 2 5 9 14 17 20 21 22 23 24 25 26 27 28
Thru
st-t
o-P
ow
er ra
tio
(N
kW
-1)
Test number
- 25 to 30 %
- 10 to 20 %
# Nominal value
Mechanical and energetic performances of slow speed mixers are impacted by:
• location of the mixers
• induced mean horizontal velocity of liquid
• tank geometry
On site measurements
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012 3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
0 10 20 30 40 50 60
Surface airflow rate (m3N m-2 h-1)
Gillot et al. (2005) Reactor 1 Reactor 2 Reactor 3
SSO
TE (
%/m
)
QA/SA : SSOTE
UC : SSOTE
Results
Impact of main parameters governing mixing and mass transfer in aeration tank on
Mixing characteristics / Bubble size / Oxygen transfer
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
Local simulation of oxygen transfer
Local measurement of oxygen transfer
On site measurements (Mixing/flows/mass transfer)
Mixing model development
3-D models development (Eulerian simulation – CFD)
1-D models development
Software tool O2 STAR development
Global scale Local scale
Scientific and technical approach From local to global scale
CFD and 1-D modelling
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
Scientific and technical approach / Results
Two types of models to describe hydrodynamics and oxygen transfer
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0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
UC experimental data (m s-1)
UC 1
-D M
od
el (
m s
-1)
Reactor 1
Reactor 2 +10%
-10%
CFD Modelling / 3-D model
Integration of mixing model / mass transfer model / empirical bubble size evolution
Allow to describe local hydrodynamics and mass transfer
Limited by the computer’s power
Cannot be included into software tool
1-D model
Based on mass and momentum conversion laws
Boundary conditions deduced from experimental data / CFD simulation
Input data must be precise
Easy integration into software tool
A further step is required to
validate CFD models for the
prediction of oxygen transfer
efficiency
The description of the
interaction of mixing and
aeration required further
investigations
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
Local simulation of oxygen transfer
Local measurement of oxygen transfer
On site measurements (Mixing/flows/mass transfer)
Mixing model development
3-D models development (Eulerian simulation – CFD)
1-D models development
Software tool O2 STAR development
Global scale Local scale
Scientific and technical approach From local to global scale
Software tool O2 STAR development
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
A beta version is currently being tested
Should be made available online in 2012 on the Irstea website
English version will be included
Web application Matlab calculator program
Conclusions
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
The software tool O2 STAR has been developped to design and optimise aeration systems installed in aerobic reactors
This tool integrates hydrodynamics and mass transfer models developed and validated from local to global scale
Innovative measurements methods have been developped
A database of mixing and oxygen transfer parameters has been build up on three full-scale aeration tanks
The software tool will be available online in 2012 on Irstea website
Ongoing research: optimisation of performances under process conditions
ANR for funding O2 STAR
Acknowledgements
16th International
Symposium Water,
Wastewater, Solid
Waste, Energy
May 8th, 2012
