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Modelli matematici applicati ai processi di filtrazione a membrana

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Mathematical modelling of MBR system. Biomath, Ghent University, Belgium. 06-06-2006 ... Overview of the presentation. Modelling the biological performance of ... – PowerPoint PPT presentation

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Title: Modelli matematici applicati ai processi di filtrazione a membrana


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Modelli matematici applicati ai processi di
filtrazione a membrana Mathematical modelling
of MBR system
Biomath, Ghent University, Belgium 06-06-2006 Tao
Jiang
3
Overview of the presentation
  • Modelling the biological performance of MBR
  • Modelling of MBR fouling

4
Biological difference of MBR and TAS
  • Complete retention of solids and partial
    retention of colloidal/macromolecular fraction
  • Operational parameters
  • Long SRT
  • Short HRT

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

6
Colloidal concentration in MBR sludge
  • TAS Effluent 30-60 mg/L
  • MBR sludge (lt0.45µm) 50-200 mg/L
  • MBR effluent (ltpore size) 5-20 mg/L
  • Membrane retention 70-95

7
Colloidal fraction is S or X?
  • By size
  • Colloidal fraction lt 0.45 µm ? S
  • By retention
  • 70-90 retention ? X
  • By biological degradation
  • Slow biodegradable ? X

8
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 (CODColltltCODTSS)

9
Influence of long SRT and short HRT
  • High MLSS concentration
  • MLSSSRT/HRT..
  • Increased sensitivity of X (advantage of
    calibration)
  • Inert particulate COD build up in MBR
  • XI SRT/HRTXI,in
  • Careful wastewater characterization
  • Low active biomass fraction

10
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

11
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

12
Modelling of a lab-scale MBR
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WEST Configuration
14
WEST Experimentation
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Simulation results - Particulate
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Simulation results - effluent
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Simulation results - user defined
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Objective of modelling MBR fouling
  • Prediction of membrane fouling (TMP vs t)
  • Facilitate integrated design, upgrading,
    operation
  • Cost reduction

19
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?

20
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)

21
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

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