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Modelli matematici applicati ai processi di filtrazione a membrana

Modelli matematici applicati ai processi di filtrazione a membrana — Mathematical modelling of MBR system. Biomath, Ghent University, Belgium 06-06-2006 Tao Jiang. Overview of the presentation. Modelling the biological performance of MBR Modelling of MBR fouling.

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Modelli matematici applicati ai processi di filtrazione a membrana

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  1. Modelli matematici applicati ai processi di filtrazione a membrana — Mathematical modelling of MBR system Biomath, Ghent University, Belgium 06-06-2006 Tao Jiang

  2. Overview of the presentation • Modelling the biological performance of MBR • Modelling of MBR fouling 2

  3. Biological difference of MBR and TAS • Complete retention of solids and partial retention of colloidal/macromolecular fraction • Operational parameters • Long SRT • Short HRT 3

  4. Colloidal fraction in MBR • Colloidal: 0.001 µm - 1µm • MBR membrane pore size: 0.03-0.4 µm • non-settable flocs in TAS: < 5-10 µm • Additional removal of solids by MBR • Small flocs (0.45-10 µm) • Partial retention of colloids (pore size - 0.45µm) 4

  5. Colloidal concentration in MBR sludge • TAS Effluent: 30-60 mg/L • MBR sludge (<0.45µm): 50-200 mg/L • MBR effluent (<pore size): 5-20 mg/L • Membrane retention: 70-95% 5

  6. Colloidal fraction is S or X? • By size: • Colloidal fraction < 0.45 µm  S • By retention: • 70-90% retention  X • By biological degradation: • Slow biodegradable  X 6

  7. Colloidal fraction is X • Colloidal fraction is X, although smaller than 0.45 µm • No significant error in TSS measurement, if the colloidal fraction is missing (CODCol<<CODTSS) 7

  8. Influence of long SRT and short HRT • High MLSS concentration • MLSS=SRT/HRT*….. • Increased sensitivity of X (advantage of calibration) • Inert particulate COD build up in MBR • XI= SRT/HRT*XI,in • Careful wastewater characterization • Low active biomass fraction 8

  9. Membrane model • Simple option (BNR study) • Point settler and include the colloidal fraction into X • Complete option (membrane fouling study) • Define new variable S_SMP (X) • Define retention of S_SMP by membrane 9

  10. Modelling of settler vs. membrane • TAS (settler) • Difficulty in calibrating settling model • Possible biological processes in settlers • MBR (Membrane) • Point separation (no volume) • No biological processes • Complete retention of X • Partial retention of colloidal fraction 10

  11. Modelling of a lab-scale MBR 11

  12. WEST – Configuration 12

  13. WEST – Experimentation 13

  14. Simulation results - Particulate 14

  15. Simulation results - effluent 15

  16. Simulation results - user defined 16

  17. Objective of modelling MBR fouling • Prediction of membrane fouling (TMP vs t) • Facilitate integrated design, upgrading, operation • Cost reduction • … 17

  18. Influence of biology on fouling • Feed to membrane is activated sludge • The composition of activated sludge is determined by the influent and operation of biological process • How biology influence fouling • What is the main foulant? • Influence of MLSS, SRT, HRT, DO? 18

  19. Foulant in MBRs • The main foulant in MBRs is up to the influent composition, design and operation • Particulate and colloidal can be the main foulant • Colloidal fouling is getting more attention (soluble microbial products) 19

  20. Steps in the modelling of fouling • Identify the main foulant • Quantify the amount of foulant and their fouling potential • Estimate the deposit rate of foulant on/in the membrane • Predict additional resistance due to the foulant • Estimate the reversibility of foulant by backwashing and chemical cleaning 20

  21. conclusion 21

  22. Modelling the biolgical performance of MBR is simpler than TAS • Modelling of MBR fouling, especially fouling prediction is extremely difficult and pre-mature 22

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