Magnetic Resonance Imaging of Membrane Fouling Dr Einar Fridjonsson - - PowerPoint PPT Presentation

Magnetic Resonance Imaging of Membrane Fouling

Dr Einar Fridjonsson

Fluid Science & Resources School of Mechanical and Chemical Engineering University of Western Australia

Mobile NMR technology Research Areas:

Low field NMR (Remote Operations): Oil & Gas industry (1) Emulsion & oil discharge monitoring Oil & Gas industry (2) Multi-phase flow metering Mining & Coal seam gas industries (3) Well logging Desalination industry (4) Membrane fouling (Desalination)

• 87 million m3/day desalination

capacity (2015).

• 18,426 desalination plants

worldwide.

• Globally more than 300million

people rely on desalination.

(Source: IDA - International Desalination Association)

Reverse Osmosis Membranes: NEED

Sources: UNESCO, IFPRI

Local motivation

47% of Perth‘s water comes from desalination!

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• Fig. 1. (a) Kwinana desalination plant in Perth, Western Australia; (b) an example of a heavily

biofouled desalination membrane module, the dark regions are due to biofilm.

Feed Feed spacer Feed water Permeate RO Core Permeate Concentrate

Reverse Osmosis Membranes: Construction

Bio-fouling is a major limitation for ROMs

Research aims:

• Direct evidence that spacers host biofilm growth and loss of membrane performance
• Direct measurement of ROM cleaning potential
• Early detection of membrane bio-fouling
• Development of low-cost MRI solution for monitoring membrane fouling.

NMR/MRI Studies

High-field (Superconducting) (Cost > $1M) Bench-top (Permanent Magnet) (Cost > $100k) Mobile (Permanent or No Magnet) (Cost < $10k)

Tap water Flow controller Differential pressure transmitter Pressure regulator Carbon filter RO module

ΔP

Nutrients Pump Discharge

Schematic: Flow loop for spiral wound membrane fouling

Imaging Biomass Accumulation (High-field)

Unfouled Fouled

Velocimetry

Imaging Biomass Accumulation (High-field)

Graf von der Schulenburg, D.A., Vrouwenvelder, J.S., Creber, S.A., van Loosdrecht, M.C.M and Johns, M.L. (2008), Nuclear Magnetic Resonance Microscopy Studies of Membrane Biofouling, J. Memb. Sci., 323(1), 37-44.

Imaging Biomass Accumulation – Model System

16 mm 37 mm x y z

pH 12 NaOH at 45°C, 100 mL/min for 1.5 h

Structural Velocity

0.05 m/s

• 0.01

m/s

Imaging Biofouling cleaning processes - Example

0.05 m/s

• 0.01

m/s

• A variety of cleaning protocols assessed and effectiveness related

to original fouling structure

Creber, S.A., Vrouwenvelder, J.S., van Loosdrecht, M.C.M and Johns, M.L. (2010), Chemical cleaning of biofouling in reverse osmosis membranes evaluated using magnetic resonance imaging, J. Memb. Sci. 362(1-2), 202-210.

Front Middle End Clean Fouled

55 mm 55 mm (a) (c) (d) (b)

On-line Analysis?

On-line NMR/MRI tool should be simple, robust and low cost. Superconducting Magnets Permanent Magnets

Even Simpler System: Mobile NMR/MRI

Nuclear Magnetic Resonance (NMR) measurements conducted using Earth’s magnetic field as the external (B0) magnetic field.

NMR experiments conducted at end of each fouling stage (indicated by arrows):

Fridjonsson et al. J. Memb. Sci. 489 (2015): 227-236.

High Field MRI (400MHz)

Before Fouling After Fouling Before Fouling After Fouling

Flat Sheet Membrane: Spiral Wound Membrane: Observations: Fouling causes a backbone (Channeling) flow

• ccurs within membrane system:

Results in stagnant (slow) flow regions & Flowing regions to flow at higher velocity.

High field MRI - Observations

No Fouling: Linear decrease in NMR signal with increasing velocity: Fouling Stage 3: Negligible decrease in NMR signal as function of increasing velocity. NMR signal measured has increased.

2

/ 0 1

E

T T E d d

T U S S e L

−

  −     ฀

Low field NMR - Observations

“Outflow” effect

=

Results consistent with high field NMR observations: Fouling causes stagnation (low flow) regions to form, resulting in increased total signal, and independence of increasing flow rate.

Fridjonsson et al. J. Memb. Sci. 489 (2015): 227-236.

Da Fit

y x Spatial domain Frequency domain, S x Σy kx ky Frequency domain, φ kx kx kx ky ln(S/Smax) φ Fourier transform

Acquire only the moments of the signal distribution - Test

Fridjonsson et al., J. Magn. Reson. 252 (2015): 145-150.

2 2 max

S(k) 1 ln k S 2σ ≈ −

0.5 0.6 0.7 0.8 0.9 1 1.1 40 60 80 100 120 140 10 20 30 40 2nd Moment - σ2 -(cm2) Pressure Drop (kPa) Fouling Time (Days)

Pressure Drop 2nd Moment

2 2 max

S(k) 1 ln k S 2σ ≈ −

Magnetic Resonance Signal Moment Determination using the Earth’s Magnetic Field

Future Work: Modelling of Outflow (EF NMR)

EF MRI

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400MHz MRI

Figure 1: Typical model output with model prediction, (solid blue line) and NMR

• utput

(black crosses). It can be seen that there is good agreement between the model prediction and the NMR signal measured.

EF NMR

Future Work - Signal Enhancement & Customisation

Miniaturizing Hardware (NMR Spectrometer)

(i) Dynamic Nuclear Polarization (DNP) (ii) Compressed Sensing (iii) Bayesian Analysis Signal Enhancement: Custom Built NMR coils: NMR-CUFF (Windt et al. 2011)

CUFF – Cut-open, Uniform, Force Free

A phenomenon whereby the flux through the membrane is controlled by the film mass transfer resistance on the feed-side rather than purely the resistance of the membrane itself.

Measuring Concentration Polarisation

Feed Permeate Permeate

boundary layer solute molecules

Sodium (23Na) MRI (High-field)

29 (a) 1H image and (b) 23Na MRI images of a flat sheet membrane module (resolution 0.01 by 1mm2). (c) Shows a sodium profile of the operating membrane module (b), with concentration polarisation evident at interface.

Flat sheet membrane system:

• Monitor interplay of fouling and

concentration polarisation using sodium MRI. Spiral wound membrane module:

• Use 23Na MRI techniques to

monitor concentration polarisation and fouling.

Membrane module geometries:

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(ii) Hollow fiber (i) Spiral wound

Hollow Fibre Membranes (HFM):

Non-invasive performance measurement of membrane distillation hollow fibre modules – Four different arrangements tested. Collaboration with: Singapore Membrane Technology Centre.

Bench-top NMR

19mm

Optical MRI 10mm

10mL/min 20mL/min 30mL/min 40mL/min 50mL/min 100mL/min 400mL/min 1000mL/min 1500mL/min 2500mL/min

Yang et al. J. Memb. Sci., 451, 46-54 (2014).

Ultrafiltration (UF) HF membranes

Module type: SIP-1013 Material (membrane & housing): polysulfone (C27H22O4S)n Membranes no.: 400 ID: 0.8 mm; Length : 205 mm

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2-D MRI (Bench-top)

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In-plane resolution: 180µm x 180µm Slice thickness: 1.42cm Acquisition time: 2.3hrs Aim: Monitoring effect of fouling

• n membrane performance

using velocity images.

46 mm

Permeate Concentrate Feed water Capillaries Outer shell

0.06 m/s

• 0.02 m/s

Flow 13 mm (a) (b) 13 mm

2-D MRI (High-field MRI)

Biofouled HFM – impact on flow distribution

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13 mm (a) (b) 0.06

• 0.02

Flow 13 mm (a) (b)

Clean Fouled

Acknowledgements

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Mike Johns Sarah Creber Daniel Graf von der Schulenberg Wiktor Balinski Ryuta Ujihara Nicholas Bristow Andrew Sederman Dan Holland Szilard Bucs Hans Vrouwenvelder Mark von Loosdrecht

Funding/Support from

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Mobile NMR and MRI

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THANK YOU

http://www.fsr.ecm.uwa.edu.au

NMR Measurements:

Velocity: Proton density: T1 & T2 Relaxation:

0.1 0.2 0.3 0.4

• 100

100 200 300

amplitude frequency / Hz

Chemical Shift: Diffusion/DSD:

0.00 0.05 0.10 0.15 0.20 0.0 5.0 10.0 Droplet size (µm) Oil Water

Free Water Water (surface interacting)