1. ICOM 2008 | July 12-18, 2008, Honolulu, Hawaii USA
Importance of membrane reactor design on membrane performance in biofilm-MBR
Igor Ivanovic, TorOve Leiknes (
NTNU - Norwegian University of Science and Technology
Department of Hydraulic and Environmental Engineering,
Trondheim, Norway

2. Content
BF-MBR concept and MBBR
Membrane reactor requirements
Membrane reactor design and fouling
Strategies for minimizing fouling due to suspended particles
Strategies for minimizing fouling due to colloidal particles
Results and discussion
Conclusion

3. Biofilm process → Membrane process
BioFilm MemBrane Reactor (BF-MBR) concept
Biofilm process → Membrane process
Concept:
SCOD
PCOD
Process:
Objectives:
One-step biological degradation
Design membrane reactor for enhanced particle removal

4. Biofilm reactor designed for Nitrification
Recirculation!
Biomass attached for plastic carriers (by AnoxKaldnes)
One-step biological degradation process
Aeration demand (2-4 mgO2/L) –
full nitrification (low organic load) after HRT=4-6 hours

5. Biofilm reactor: performance and removal rates

6. Particles and fouling (previous studies)
1. Suspended particles – MLSS - range > 1,2 µm
35 LMH
2. Colloidal particles – PSD number % - range 0,04 -1,2 µm

7. Membrane reactor requirements
Particle separation unit!
Higher fluxes (compared to AS-MBR) - i.e. > 30 LMH
High recovery (R) – i.e. 95 % and more
Short HRT (and SRT) – i.e. HRT < 1 hour

8. ☺way to go! Possible BF-MBR configurations ↓BF + AS ↑ !Not desirable!
Scenario No1:
Typical submerge MBR configuration would convert biofilm reactor to activated sludge reactor due to accumulation of retained biomass
↓BF + AS ↑
!Not desirable!
Biofilm reactor
Scenario No2:
External submerge membrane reactor opens possibility to keep retained biomass separated from biofilm and provides stable i.e. designed bioreactor operation
☺way to go!
Biofilm reactor

9. Suspended particle reduction – MLSS reduction
1. Complete mixed reactor CM-MR – Recovery (R)!
2. Rector with sludge pocket SP-MR – Separation coefficient Ks!
c≠c2 ; c<c2

10. Pilot plant configuration
MBBR:
Total volume of reactor: 260 L
Type of carrier: K1 – AnoxKaldnes
Filling fraction – 67 % of reactor volume
Surface area for biofilm growth m2/(m3 reactor volume)
Total growth area m2
> 99% Nitrification achieved
HRT=4 hours
Membrane:
Zenon ZW10 Membrane Pilot Module
Nominal pore size – 0,04μm
Material PVDF
Membrane area- 0.93m2
Membrane operation:
Production flux – 35 LMH
Backwash flux – 42 LMH
Operating cycle: 4.75 min/production
0,25 min/backwashing
Recovery ~ 96 %

11. CM-MR vs. SP-MR CM-MR: Volume=9 L HRT=0,3 hour
SolidRetentionTime SRT=7,5 hour
Ks=1
Recovery ~ 96 %
SP-MR:
Volume=25 L
HRT=0,7 hour
SolidRetentionTime SRT=20,8 hour
Ks=?
Recovery ~ 96 %

12. Comparison - performance
Separation factor Ks determinate at 3,4 and fouling rate decreased ~ 3 times

13. Challenge – floating sludge in SP-MR!!!
With increasing volume of membrane reactor SRT increased.
Longer SRT creating anoxic conditions inside sludge pocket and causing sludge bulking
Improvements of membrane reactor were required!

14. SP-MR and MSP-MR SP-MR: Volume=25 L HRT=0,7 hour
SolidRetentionTime SRT=20,8 hour
Ks=3.4
Recovery ~ 96 %
MSP-MR
Volume=41 L
HRT= 1,3 hour
SolidRetentionTime SRT=33.3 hour
Ks=?
Recovery ~ 96 %

15. Comparison - performance
Separation factor Ks of MSP-MR increased additionally up to ~ 2,5 times (Ks=8,4) and fouling rate decreased ~ 6 times
Floating sludge was no longer problem!!!

16. Colloidal particle reduction – PSD number% reduction
Colloidal (submicron) particles are not settable.
Strategies to reduce colloidal particles:
1. Prevention of flocs brakeage during the membrane aeration (air scouring)
2. Flocculation – natural UP
DOWN

17. Colloidal particles reduction in MSP-MR
Inlet

18. Membrane performance - TMP start up for CM, SP and MSP-MR
CM-MR
Confirmed by less fouling measured – expressed in TMP development

19. Conclusions
Membrane reactor design play key role in fouling control in BF-MBR
Confirmed reduction of fouling rate due to reduction of amount of particles (both suspended and colloidal) around membrane area
New strategies for reduction of colloidal (submicron) particles required

20. Acknowledgments MSc Students:
Financial support by: Norwegian research council (NFR)
ZENON Environmental Inc., Canada, for supplying the membrane modules
AnoxKaldnes, Norway, for support with the biofilm reactor
EUROMBRA, Contract No ,
MSc Students:
Francisco Sánchez Molada, Polytechnic University of Valencia
Heidi Bold, ETH Zurich, Switzerland
Martin Engmann, ETH Zurich, Switzerland
Gerrit Senger, TU Berlin

21. Thanks for your attention!
Acknowledgments
Greetings from Trondheim's fjord!
(sailing sessions edition)
Thanks for your attention!
QUESTIONS ?!?
TorOve Leiknes:
Igor Ivanovic: