1. Ultrafiltration fouling control
Demineralized water backwashing
Sheng Li
Sanitary Engineering, Delft University of Technology
The Netherlands
2017年4月12日星期三

2. Content
Introduction
Hypotheses
Results
Conclusion
2017年4月12日星期三

3. Demi water is better than UF permeate for backwashing
Why is demineralized water better?
No pre-treatment! No in-line coagulation!
2017年4月12日星期三

4. Difference between UF permeate and demineralized water for backwashing
Divalent ions
Monovalent ions
Organic matter
2017年4月12日星期三

5. Hypotheses of NOM fouling
Ca-bridging effect and/or Ca complexation
Charge screening effect (DLVO theory)
NOM molecule adsorption
2017年4月12日星期三

6. Ca-bridging effect (filtration)
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7. Ca-bridging effect (Backwash with permeate)
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8. Ca-bridging effect (Backwash with demi water)
2017年4月12日星期三

9. Charge screening effect (filtration)
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10. Charge screening effect (Backwash with permeate)
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11. Charge screening effect (Backwash with demi water)
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12. Results (Impact of calcium, flux: 85 lmh)
No pre-treatment! No in-line coagulation!
2017年4月12日星期三

13. Results (Impact of sodium, flux: 85 lmh)
No pre-treatment! No in-line coagulation!
2017年4月12日星期三

14. Experiment set-up and Material
UF set-up: “MFI-UF” (Kiwa Water Research, NL)
Membrane: Capillary membrane, 0.8 UFC M5 (X-Flow), with a surface area of 0.07 m2
2017年4月12日星期三

15. Backwash solutions Demineralized water UF permeate
UF permeate after dialysis (organic matter is isolated)

16. Permeate after dialysis
MWCO of Dialysis bags:3.5K Da

17. Feed water: Schie canal water (Delft, NL)
Water quality parameter
Feed
Ca2+ (mg/l)
101
Na+ (mg/l)
58.57
Conductivity (µs/cm)
836
Turbidity (NTU)
4.5
DOC (mg/l) 20
2017年4月12日星期三

18. Composition of backwash solutions
Ca2+
(mg/l)
Na+
DOC
UF permeate
100
58.56
18.65
UF permeate after dialysis 20
8.7 17
Demineralized water
<1
0.5

19. Impact of organic matter (flux:120 lmh)
No pre-treatment! No in-line coagulation!
2017年4月12日星期三

20. Effect of backwash solution on membrane surface charge
Two types of backwash solution were used in this study
Milli Q water
UF permeate
2017年4月12日星期三

21. Measurement set-up Wilbert van der Ven et al. 2008 Along fiber
Through pore
Wilbert van der Ven et al. 2008
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22. Measurement method
1 mM KCl solution was used in this study as background electrolyte solution
2017年4月12日星期三

23. Streaming potential of membrane
Backwash with permeate
Streaming potential were measured before and after 14 filtration cycles. One cycle consists of 15-minute filtration at a flux of 120 lmh and 1-minute backwash at a flux of 240 lmh
2017年4月12日星期三

24. Streaming potential of membrane
Backwash with Milli Q water
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25. Conclusions
Backwashing with demineralized water is more efficient than UF permeate on fouling control
Both Ca and Na in backwash water contribute to the fouling of UF, probably by maintaining the bridge effect or decreasing the zeta potential of the membrane and the foulant
Organic matter in backwash water does not influence the fouling control of the UF membranes
Backwashing with pure water can maintain the negative charge of membrane
2017年4月12日星期三