Ceramic membranes for water
treatment applications
Katie Guerra, Bureau of Reclamation
John Pellegrino, University of Colorado
This presentation compares ceramic and polymeric MF
and UF membranes for water treatment applications.
1. Reported benefits and
limitations of each material
VS
2. Literature review - flux and
permeance comparison
2
3. Laboratory comparison of
fouling propensity
1.5
1
0.5
0
0
100
MF and UF membranes can be made of polymeric
or ceramic materials.
Polymeric
Tubular vs hollow
fiber module
configuration
SEM of membrane
surface (x5000)
Ceramic
Ceramic membranes offer a number of advantages
over polymeric membranes.
• Benefits of ceramic membranes
–
–
–
–
Mechanical strength
Chemical and thermal resistance
Longer operational life
High flux and low fouling
• Potential limitations
– High initial capital cost
– Lack of operational experience in the US
Adapted from TAMI Industries
The first full scale ceramic membrane system for water
treatment expected to be online ion 2012.
• Reuter-Hess Reservoir water
• 1st large scale ceramic membrane
system in the US
• Key factors in selection: low
maintenance and membrane lifespan
From: Myers, N., A. Pratt, M. Lutz, Organic removal utilizing ceramic microfiltration membranes in
combination with enhanced coagulation and PAC addition.
A literature review was conducted to evaluate the
claim of “higher flux” for ceramic membranes.
• Two ways of accomplishing higher flux
– Higher trans-membrane pressure
– Have a more permeable membrane
• Pure water permeance
• Pressure normalized flux of DI-water
• Used instead of MWCO or pore size
• Feed water permeance
• Pressure normalized flux of feed water
• Feed water flux
Ceramic membranes were not operated at a higher
flux than polymeric membranes.
flux (m3/m2/s)
2.0E-04
1.5E-04
Ceramic
Polymeric
n = 68
1.0E-04
5.0E-05
0.0E+00
pure water permeance (m3/m2/s/kPa)
feed water permeance
(m3/m2/s/kPa)
Ceramic membranes may have higher feed water
permeance in the MF range.
5.E-09
Ceramic
4.E-09
Polymeric
n = 68
3.E-09
Ultrafiltration
Microfiltration
2.E-09
1.E-09
0.E+00
pure water permeance (m3/m2/s/kPa)
Other factors, such as fouling tendency and cleaning efficiency may provide more
benefit than flux or permeance.
Characteristics of membranes used in laboratory
evaluation.
Parameter
Ceramic
Polymeric
Membrane material
Nominal molecular
weight cutoff (g/mol)
Al2O3 composite
Unknown
Polyethersulfone
10,000
Pore size
Channel diameter (mm)
0.01 µm
1.05
Unknown
1.00
Channel length (mm)
Number of channels
Total membrane area (m2)
Pure water permeance
(L/m2/d/kPa)
304.8
208
0.195
36 ± 3
304.8
142
0.13
16.7 ± 0.7
Membranes must be operated at the same hydrodynamic
conditions to compare fouling tendancy.
• Peclet number (Jo/k)
• Jo = initial feed water flux
• k = mass transfer coefficient
2 0.33
UD
k  1.62

 dh L 
Diffusion
Advection
permeate
Constant flux experiments were conducted for a
range hydrodynamic conditions.
• Constant flux
experiments
• Series of experiments
– each one with
increase Pe number
• Evaluate pressure
increase per mass of
solute filtered
• Bentonite solutions:
tubidity = 100 NTU
The critical Peclet number of the polymeric is
between 1010 and 1200.
2
J/k = 400
J/k = 600
J/k = 830
J/k = 1010
J/k = 1200
J/k = 1400
1.8
1.6
1.4
P(t)/P(0) (-)
1.2
1
0.8
400
0.6
600
830
1010
1200
1400
0.4
0.2
0
0
20
40
60
Mass applied (g)
80
100
Significant mass accumulation for the ceramic
membranes occurred at Pe > 1200.
2
J/k = 400
J/k = 600
J/k = 870
J/k = 1020
J/k = 1200
J/k = 1360
J/k = 1440
1.8
1.6
1.4
P(t)/P(0) [-]
1.2
1
0.8
400
600
870
1020
1200 1360
1440
0.6
0.4
0.2
0
0
20
40
60
Normalized mass applied (g/m2)
80
100
The ceramic membrane can be operated more efficiently
at higher Pe numbers than the polymeric membrane.
0.02
Polymeric
Slope of delta P vs mass/area
0.018
Ceramic
0.016
0.014
0.012
0.01
0.008
0.006
0.004
0.002
0
0
500
1000
Pe
1500
2000
In summary, ceramic membranes offer some
intrinsic resistance to particulate fouling.
Acknowledgements
Funding
• Bureau of Reclamation
Science and Technology
Research and Development
Program
• Corning, Incorporated
(donated membranes)
• NWRI Student Fellowship
Program