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ICT I Desalination and Water Reuse
J. Georgiadis, O. Coronell, L. Rakocevic, P. Tontcheva, E. Morgenroth
“sea to sink to the sea again”
Desalination & Water Reuse• Institutions & PIs
– U.C. Berkeley: R. Shen – LLNL: O. Bakajin– Howard University: K. Jones – Notre Dame: P.
Bohn– University of Illinois: N. Aluru, D. Cahill, J. Economy, J.
Georgiadis, S. Granick, E. Luijten, B. Mariñas, J. Moore, E. Morgenroth, M. Shannon
– Massachusetts Institute of Technology: A. Mayes– Rutgers University: S. Prakash– University of Michigan: L. Raskin– Yale University: M. Elimelech
ICT-1: Organization & Objectives• Area I-A: Thermal Desalination and Liquid Discharge
Minimization– Reduce energy expenditure relative to RO– Minimize liquid discharge to less than 5% of total flux
• Area I-B: Pressure-driven and Active Membranes– Increase flux 2-fold– Decrease fouling
• Area I-C: Membrane Bioreactor Technology– Decrease sorptive, particle, and biofilm fouling– Link MBR with downstream processing (e.g. RO) for
water reuse
Reverse Osmosis Energy Use
Minimum energy of separation
John MacHarg and Randy Truby, “West coast researchers seek to demonstrate SWRO affordability”, Desalination and Water Reuse, 14/3, 2004.
Energetics of DesalinationP = + Preject + Ppolar + Pmembrane + Pviscous + Pfoul
Reverse Osmosis Cost
Shannon et al., “Science and technology for water purification in the coming decades”, Nature, 452, 2008.
ICT-1: Organization & Objectives• Area I-A: Thermal Desalination and Liquid
Discharge Minimization– Forward osmosis
• Area I-B: Pressure-driven and Active Membranes– Active membranes– NF/RO membranes– Antifouling membranes
• Area I-C: Membrane Bioreactor Technology– Fouling mechanisms– Extracellular polymeric substances
0
1
2
3
4
5
6
kW
h/m
3
MSF MED-TVC MED-LT RO FO-LT
Energy Requirements of Desalination Technologies
Contribution fromElectrical Power
Adapted from: McGinnis, Elimelech, “Energy Requirements of Ammonia–Carbon Dioxide Forward Osmosis Desalination”, Desalination, 207 (2007) 370-382.
RO FO
0 10 20 30 40 50 60 70 80 90 1000
50100150200250300350400450
(atm)
Recovery (%)
Seawater
Minimizing Liquid Discharge
Forward Osmosis (FO)R. McGinnis, D. Chen, O. Bakajin, M. Elimelech
Saline Water
Draw (NH3/CO2)
ProductWaterBrine
Membrane
Draw Solute Recovery
EnergyInput
D,b
Theo
Water flux
F,b
eff
Convection
Porous support
Active layer
Challenge: Concentration Polarization in FO
Concentrative external CP
Feed crossflow
Draw crossflow
Diffusion
Dilutive Internal CP
Diffusion
)(
)( ,,
effW
mFmDW
AJ
AJ
ICT-1: Organization & Objectives• Area I-A: Thermal Desalination and Liquid
Discharge Minimization– Forward osmosis
• Area I-B: Pressure-driven and Active Membranes– Active membranes– NF/RO membranes– Antifouling membranes
• Area I-C: Membrane Bioreactor Technology– Fouling mechanisms– Extracellular polymeric substances
Active Transport Membranes
Active Transport - Nanocapillary Array Membranes S. Prakash, J. Lucido, H. Fitzhenry, J. Wan, G. Mensing, J. Georgiadis, M. Shannon
NCAM
HEMA
Au- NCAM
Ion transport occurs across membranes and AC bias is more effective than DC bias for manipulating ion flux.
0
40
80
120
160
0 25 50 75 100 125 150 175 200 225 250Time (min.)
Con
duct
ivity
(m
S)
0.00625 mM No bias1 mM No bias0.00625 mM DC bias1 mM DC bias0.00625 mM AC bias1 mM AC bias
Slope: 0.045 ± 0.001
Slope: -0.153 ± 0.001
Slope: 0.106 ± 0.002
Slope: -0.161 ± 0.004Slope: -0.231 ± 0.008
Slope: -0.295 ± 0.01
ICT-1: Organization & Objectives• Area I-A: Thermal Desalination and Liquid
Discharge Minimization– Forward osmosis
• Area I-B: Pressure-driven and Active Membranes– NF/RO membranes– Active membranes– Antifouling membranes
• Area I-C: Membrane Bioreactor Technology– Fouling mechanisms– Extracellular polymeric substances
Water flux in Nanochannels L. Rakocevic, M. Suk, A. Raghunathan, N. Aluru, J. Georgiadis, M. Shannon
Water flux vs. ∆P for BNNT, CNT, and PMMA membrane
Flux enhancement in CNT/BNNT
Water transport by collective “hopping”events of single-file water molecules
Permeation coefficient, pn=k0 by reaction rate theory where k0 is equilibrium hopping rate
Density Functional TheoryLengthscale O(A)
Molecular DynamicsTimescale O(ns)
Lengthscale O(nm)
Coupled Poisson Nernst PlanckTimescale O(ms)
Lengthscale O(mm)
Ion mobility Diffusion coefficient
Partial charges
The system
The material
Characterization of RO MembranesO. Coronell, X. Zhang, D. Cahill, B. Mariñas
FT30 Reverse osmosis (RO)
Support Layer(Polysulfone)
Selective barrier(polyamide)
Membrane characterization procedures are needed
~150 nm
Polyamide (~100 nm)
NHCONH2 CONH NHCO
CONH COOH
Pressurized feed
Amine group
Carboxylic groupAmide link
Functional groups in the active layer
Polysulfone (50 mm)
Polyamide (~150 nm)
Ag+ Ag+ Ag+
Ag+
Ag+ Ag+
Ion probingRutherford backscattering spectrometry (RBS)
RBS DetectorHe+
pH
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Ion
prob
e co
ncen
tratio
n (M
)
0.0
0.1
0.2
0.3
0.4
0.5
R-COO- R-NH3
+
1. Quantification of functional groups (FGs)
FT30 (RO) RBS data
pH
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Ion
prob
e co
ncen
tratio
n (M
)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
w1 = 0.2 ; pKa,1 = 5.3
w2 = 0.8 ; pKa,2 = 9.0
Carboxylic groups
[R-COO-]MAX =
0.435 M
2. Modeling of ionization behavior of FGs
FT30 (RO) RBS data
3. Location of FGs in the active layer
Polyamide active layer
Polysulfone support layer
Chlorine
FT30 (RO) Secondary ion mass spectrometry (SIMS) data
~150 nm
1. Elemental composition of active layer2. Thickness and roughness of active layer3. Quantification of functional groups (FGs)4. Modeling of ionization behavior of FGs5. Quantification of steric and valence effects
on counterions6. Location of FGs in the active layer
Research achievements
Water Mobility in CNT MembranesL. Rakocevic (UIUC), J. Georgiadis (UIUC), O. Bakajin (LLNL)
∙ Thickness = 3 μm∙ Porosity = 2 %∙ Hydrophobic material∙ Average pore size=1.6nm∙ Atomically smooth walls
Double walled Carbon Nanotube
TEM image of CNT membrane
Holt et al. Science 2006
CNT Membrane Performance
MD: water diffusion coef. ~1.5×10-5 cm2/s ! Bulk water diffusion coef. ~ 2.6×10-5 cm2/sDiffusion inside CNTs has not been measured before
Energy requirements (estimated): Reduced Pmembrane 40% reduction relative to RO for seawater desalination
Experiment: Improved salt rejection and flux relative to commercial NF membranes
High water diffusion coefficient inside CNTs despite restricted space (~ nm)
Formasiero et al. PNAS 2008
Objectives
• Verify high (restricted) water diffusivity inside CNTs
• Measure water dispersivity inside CNTs• Quantify water displacement statistics
inside CNTs• Advance unique experimental technique
(MRI) for probing mass transport inside novel membranes
• Gradient G is applied for time δ
Diffusion-Weighted MRI (1)
Free waterBound water Bound water
20 30 40 50 60 70
G
00 Gx
Free water
wait for a short time ….
Bound water Bound water
xkxx x 00
Diffusion-Weighted MRI (2)
Bound water Bound waterFree water
G
-20 -30 -40 -50 -60 -70
• Gradient –G is applied for time δ xGkGx s 01
Diffusion-Weighted MRI (3)
Diffusion causes phase incoherence and therefore MRI signal loss
• The diffusion-weighted q-space (displacement space) gives a signal EΔ(q) such that:
• Example: 1-D Fickian diffusion
MRI signal:
Displacement-Weighted MRI
dRRqiRPqS )2exp(),()(
Propagator function – Probability that a spin will displace amount R (R = r’ – r) during time Δ
Accumulated phase term, where q = 1/(2π) γδg (g is the gradient amplitude)
)exp()( bDqS
Experimental setup and current progress
• 2% 20 % void fraction• 3 mm 100 mm-thick layerswith aligned carbon nanotubes
Experimental setup
LLNL current membrane fabrication improvements
Current ProgressSample with water
Sample with water +
CNT membrane parts
)exp()( bDbS
ICT-1: Organization & Objectives• Area I-A: Thermal Desalination and Liquid
Discharge Minimization– Forward osmosis
• Area I-B: Pressure-driven and Active Membranes– Active membranes– NF/RO membranes
– Antifouling membranes
• Area I-C: Membrane Bioreactor Technology– Fouling mechanisms– Extracellular polymeric substances
PAN-g-PEO as an Additive for UF Fouling Resistance
Doctor Blade
Coagulation Bath
Casting Solution Heat Treatment
Bath
Casting Solution
Doctor Blade
Coagulation Bath
Heat Treatment
graft copolymer added to casting solution
segregate & self-organize at membrane surfaces
PEO brush PEO brush layer on layer on
surface and surface and inside pores inside pores
Fouling Fouling resistanceresistance
Asatekin, Kang, Elimelech, and Mayes: J.Membr.Sci. 298 (2007) 136-146. Kang, Asatekin, Mays, and Elimelech: J.Membr.Sci. 296 (2007) 42-50.
• Increased clean water flux with increased comb content
• After fouling with BSA - complete flux recovery with 20% comb content
Fouling Reversibility (with BSA)
Gray: Recovered flux after BSA fouling/water flushing
White: Pure water
Average AFM results are not consistent with observed fouling reversibility
-8
-6
-4
-2
0
2
4
F/R
(mN
/m)
PAN (P0-0) P50-5 P50-10 P50-20
Carboxylate-modified latex particle as model foulant
Membrane
Attractive interaction
Repulsive interaction
Comb content0% 5%
10%20%
• Incomplete flux recovery with 10% comb content • Average AFM results suggest repulsive interactions
PAN
-12 -10 -8 -6 -4 -2 00
15
30
45
60
Freq
uenc
y (%
)
F/R (mN/m)
PAN (P0-0)
Incomplete fouling reversibility due to heterogeneous comb distribution
PAN 5%
-12 -10 -8 -6 -4 -2 0 2 40
15
30
45
60
Freq
uenc
y (%
)
F/R (mN/m)
P50-5
Incomplete fouling reversibility due to heterogeneous comb distribution
Comb content
PAN 5% 10%
Incomplete fouling reversibility due to heterogeneous comb distribution
-1 0 1 2 30
15
30
45
60
Freq
uenc
y (%
)
F/R (mN/m)
P50-10
Comb content
PAN 5% 10% 20%
Incomplete fouling reversibility due to heterogeneous comb distribution
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.50
15
30
45
60
Freq
uenc
y (%
)
F/R (mN/m)
P50-20
Comb content
10 100-1.0
-0.5
0.0
0.5
NaCl alone NaCl + CaCl
2
F/R
(mN
/m)
Ionic Strength (mM)
Fouling resistance due to steric interactions
• Interaction forces are independent of ionic strength– Electrostatic forces
cannot explain observed effects
– Steric interactions
Promising results using model foulants – but in MBR fouling mechanisms are more complex
• Model foulants– Proteins (BSA)– Polysaccharide (alginate)– Natural organic matter (humic acid)
• Fouling in MBR dominated by – Extracellular polymeric substances
(EPS)– Microbial flocs– Biofilm growth
Floc fragments Colloidal EPS Soluble EPS
Shear forces
Bacteria/archaeaEPS
Microbial floc
Membrane
Biofilm Growth
Organic substrate
Organic substrate
10 mM 30 mM 30 mM+Ca 100 mM0
300
600
900
1200
Cel
ls A
dher
ed (m
m-2)
PAN/PAN-g-PEO Commercial PAN
No E. coli Adhesion on PAN/PAN-g-PEO!
No attachment of E. coli cells on PAN-g-PEO membrane during static (1 h batch) adhesion test
Commercial membrane exhibited increased cell attachment as the ionic strength was increased
PAN-g-PEO UF membranes resistant against bacterial attachment
1 h
10 1000
25
50
75
90
100
PAN/PAN-g-PEO with NaCl With 1 mM Ca Commercial PAN with NaCl With 1 mM Ca
Rem
oval
(%)
Ionic strength (mM)
Percent removal of E. coli cells from the membrane at 150 cm/s cross flow velocity
Clean water rinsing can remove previously attached E. coli from PAN-g-PEO membrane
ICT-1: Organization & Objectives• Area I-A: Thermal Desalination and Liquid
Discharge Minimization– Forward osmosis
• Area I-B: Pressure-driven and Active Membranes– Active membranes– NF/RO membranes– Antifouling membranes
• Area I-C: Membrane Bioreactor Technology– Fouling mechanisms– Extracellular polymeric substances
Relevance of MBR to Advanced Wastewater Reuse
DisinfectionDisinfection(UV )(UV )
Wastewater
MBRMBR using MF or UFusing MF or UF
ROROWater
suitable for reuse
• MBR: Microbial production and degradation of foulants (e.g., soluble extracellular polymeric substances - proteins, polysaccharides)
• RO: Fouling in RO (ICT1-B) is directly related to effectiveness of MBR treatment (ICT1-C)
• Disinfection: ICT III
Wastewater
Effects of long-term operation of MBR • Comparing short (hours) and long-term (weeks)
fouling in anaerobic MBR Petia Tontcheva
• Mixing and mechanical shear in MBR affects the microbial ecology
– Floc structure– Amount and characteristics of
extracellular polymeric substances (EPS)– Membrane fouling
Floc fragments Colloidal EPS Soluble EPS
Shear forces
Bacteria/archaeaEPS
Microbial floc
Membrane
Biofilm Growth
Organic substrate
Organic substrate
Short and long-term fouling in anaerobic membrane bioreactors
Petia Tontcheva (UIUC) PIs: Morgenroth (UIUC), Raskin (Michigan), Anne M. Mayes (MIT)
Background: Antifouling NF (PVDF-g-POEM) Membranes
• Dead-end filtration of activated sludge from MBR– PVDF-g-POEM NF: no flux loss over 16 h filtration – PVDF base: 55% irreversible flux loss after 4 h
0 120.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Nor
mal
ized
flux
Time (hours)
PVDF base (,)
PVDF-g-POEM (●,●)
Volatile suspended solids (VSS): ~1800 mg/L
Asatekin, Menniti, Kang, Elimelech, Morgenroth, Mayes: J.Membr.Sci. 285 (2006) 81-89.
How will the antifouling membranes perform in long-term experiments?
Time of cross-flow cell operation (d)0 5 10 15 20 25 30 35
Flux
(L/m
2 h)
0
20
40
60
80
100
120
Clean water flux of new membraneFlux with anaerobic biomassClean water flux after fouling
Long-term (30d) operation of PAN/PAN-g-PEO in anaerobic MBR
• Reduced flux due to cake layer formation
• Complete recovery of flux after clean water flushing
VSS: ~ 11, 000 mg/L
PES-V PES-O PVDF PAN-g-PEO/PAN
Irrev
ersi
ble
resi
stan
ce (1
0-12 m
)
-1
0
1
2
3
4
5Short-term (5 hrs)Long-term (13 d)Long-term (30 d)
The PAN/PAN-g-PEO membranes did not exhibit irreversible fouling
Membrane surface analysis by XPS
• No indication of inorganic fouling (no Ca, Mg, ... detected)• Increasing quantities of organic foulants on PES-O membranes during the long-
term tests
clean membraneShort-term Long-term
Ato
mic
ratio
0
20
40
60
80
100
120
(C+N)/SO/S
PES-O membrane
Functional group identification by ATR-FTIR
Wavenumbers (cm-1)
100015002000250030003500
Abs
orba
nce
0.00
0.02
0.04
0.06
0.08
0.10
Long-term (13 d) Short-term
O-HN-H C-H COOH
Amide I
C-O
Amide II
Irreversible foulants: proteins, carbohydrates, and humic acids
PES-O Membrane
Shear
High Shear
Low Shear
Solu
ble
EPS
•High shear results in–Smaller microbial flocs
–Less floc associated EPS
–Less soluble EPS
Influences microbial physiology to reduce microbial foulant (= EPS) production in MBR
Low shear
High shear
EPS from high shear MBR is stickier
• Continuous high shear produces less EPS in MBR - but EPS is stickier
• How to best operate MBR?• Mixing/shear main
contribution to energy input• Reduced fouling potential for
high shear operation• Variable shear can release
floc associated EPS and result in fouling
Membrane
CML COO-
COO -
COO -
EPS
- OOC
F
3 mm carboxylate modified latex particle
Membrane
CML COO-
COO -
COO -
EPS
- OOC
F
3 mm carboxylate modified latex particle
Extracellular polymeric substances (EPS) extracted from microbial flocs
Vision for integrated MBR for wastewater reuse
Wastewater
NF based MBRNF based MBRIntegrated application Integrated application
of sorptive, ion of sorptive, ion exchange, catalytic exchange, catalytic
mediamediaWater
suitable for reuseWastewater
• Single unit system without the need for downstream processing
• Increase membrane rejection (NF instead of UF or MF membrane)
• Integrate alternative removal mechanisms with biological process
ICT 1 Path forward
• Fundamental Science– Multiscale computational framework
to explain RO and active membrane systems
– Computational and experimental techniques to understand electrokinetic transport in single nanopores
– Novel optical, spectroscopic, AFM, and RBS techniques to understand transport in membrane systems
• Membrane materials– Improve robustness of novel
UF/NF/RO membranes (e.g. RSA, CNT, PAN-g-PEO, etc.)
– Develop appropriate membrane for forward osmosis desalination
– Long-term fouling and cleaning with novel fouling resistance membrane
• Biological processes– Link microbial ecology to fouling in MBR
• Mechanisms and characterization of microbial EPS production and degradation
• Microbial mechanisms of cell attachment and biofilm formation
– Removal of micropollutants (w/ SIEMENS)• Microbial conversion• Integrate sorptive or catalytic media with
microbial processes
• System integration– Demonstrate active membrane desalination– Complete pilot FO system– Apply magnetic resonance imaging (MRI) and
computational fluid dynamics (CFD) to reduce cake formation in MBR (w/ SIEMENS)
– Compare of aerobic and anaerobic MBR (w/ SIEMENS)
Floc fragments Colloidal EPS Soluble EPS
Shear
Bacteria/archaeaEPS
Microbial floc
Membrane
Floc fragments Colloidal EPS Soluble EPS
Shear
Bacteria/archaeaEPS
Microbial floc
Membrane
Biofilm GrowthBiofilm Growth
CNT-membrane