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REVERSE OSMOSIS AND
FORWARD OSMOSIS
LABORATORY EXPERIMENTS
Jeffrey McCutcheonAssociate Professor
University of ConnecticutDepartment of Chemical & Biomolecular Engineering
3
A Story of a Thirsty University
UConn Announces
$2 Billion Expansion
Hartford Courant
how bad must it be in truly
arid regions?4
If it is this bad in Connecticut…
a place that gets 50 inches of rain per year…
Global Water Crisis
5References: http://water.org/; http://reports.weforum.org/global-risks-2015/#read
Every minute a child
dies of a water-
related disease
Children
Women and
children spend 140
million hours a day
collecting water
Women
1 in 9 people lack
access to safe
water
Water
More people
have a mobile
phone than a
toilet
Sanitation
For every $1 spent on
water and sanitation
there is a $4 economic
return
Economic
Water
Crisis
Every million dollars of GDP = 22,000 m3/yr additional water
Growing Markets for Water and Power
6
Lux Research
Public
supply11%
Irrigation
34%Industry
5%
Thermal
power generation
48%
Other
2%
U.S. Water Usage (2000)
GDP correlates strongly with energy use
We must augment existing water supplies by tapping
unconventional resourcesUnited States Geological Survey
Glo
bal
wat
er
use
(km
3)
Global Water Distribution
7References: Igor A.Shiklomanov, State Hydrological Institute (SHI, St. Petersburg) and United Nations Educational, Scientific and Cultural Organization (UNESCO, Paris),1999
A Lesson from Nature
8
“Biomimicry is common in membrane separations today.
Membranes are designed to be like biological membranes with superior
permselectivity”
Membranes are thin, selective barriers that allow certain chemical species to permeate through them while
rejecting others
Desalination Special Issue on Recent Advances in Forward Osmosis
Desalination around the world
Thermal Technologies
Membrane Technologies
https://waterenergymatters.wordpress.com/tag/desalination-capacity/
Osmosis
Reverse
Osmosis
Saltwater Freshwater
Me
mb
ran
e
pOsmotic pressure P> p
RTCpJ = Water flux
A = Water
permeability
DP = Hydraulic
pressure
difference
Dp = osmotic
pressure gradient
p = osmotic pressure
R = gas constant
T = temperature
C = concentration of
molecules
)( pDD PAJW10
Limitations of RO
11Elimelech, Science 333, 2011
• Approaching the thermodynamic minimum energy for separation for desalination
• Unable to handle high salinity feeds• Few breakthrough improvements that
would reduce RO energy use are possible
Forward Osmosis
Dilute solution Concentrated
draw solution
Me
mb
ran
e
J = Water flux
A = Water
permeability
pdraw= osmotic
pressure of the
concentrated
draw solution
pfeed = osmotic
pressure of the
dilute feed
solution
?
)( feeddrawW AJ pp 12
Desalination, Reuse, and Dewatering
13
EnergyInput
Saline/ImpairedWater
Brine
Membrane
Adapted from McCutcheon, McGinnis, Elimelech, Desalination, 174 (2005) 1-11.
Draw Solute
Recovery
Draw Solution
SpontaneousProcess
Clean Water
Osmotic Dilution
14
Saline Water
Brine
Membrane
Diluted draw
solution
Draw Solution
SpontaneousProcess
Other Uses for Osmotic Pressure?
• Osmotic pressure is a physical manifestation of a chemical potential
difference
• PRO offers a unique way of converting chemical potential energy into
electrical energy by using a hydraulic energy intermediate
15
JW = A(Dp – DP)
W = (E) x (DP) x (JW)
Achilli, Journal of Membrane Science 343, 2009, 42-52
Naturally Occurring Salinity Gradients
Saline water acts as a source of chemical
energy
16
Nile River Mississippi River
Great Salt Lake
Dead Sea
Pressure Retarded Osmosis (Open
Loop)
17
Freshwater
Membrane
Diluted draw
solute
Draw Solution
(Seawater)
PX
JW = A(Dp – DP)Dp> DP
W = (E) x (P) x (JW)
Mix and discard to draw source
Work
Pressure Retarded Osmosis (Closed
Loop)
18
Pure water working fluid
Membrane
Draw Solute
Recovery
Draw Solution
Work
PX
EnergyInput
McGinnis, Journal of Membrane Science, 305, 2007, 13-19.
W = (E) x (P) x (JW)JW = A(Dp – DP)Dp> DP
Misconception # 1 about FO
• RO is an excellent technology for low to moderate
salinity feeds, but….
• FO can do many things that RO cannot
– Handle high salinity waters
– Directly handle liquids with a high fouling propensity
• FO can often work in tandem with RO as a
complimentary process
19
Forward osmosis will replace reverse osmosis
Misconception #2 about FO
• There is no such thing as a free lunch
• FO can use free or less costly energy
than RO
• FO may lower the cost of desalination
and reuse
20
Forward osmosis uses less energy than reverse osmosis
Opportunities for FO
• Difficult waters
• High salinity
• High TDS/TSS
• Materials that are
sensitive to heat
and pressure
• Utilization of low
grade energy
• Power production?
21
Carl Lundin, CDM-Smith, IFOA Meeting, 2014
What folks care about
• Membrane
• Draw solution
• Process design
22
What folks care about
• Membrane
• Draw solution
• Process design
23
Types of Membrane Materials
Baker, R. Membrane Technology and Application, 3rd Edition
XX
X XX
Dong, G., Li, H., Chen, V., Journal of Materials Chemistry A, 1, 2013, 4610-4630
McCutcheon, McGinnis, Elimelech, Desalination, 174 (2005) 1-11.
Challenges with Membrane
Design
25
Conventional asymmetric membranes structures cause
severe mass transfer resistance during osmosis
tS
Conventional RO Membranes Commercial FO Membrane
The Problem with Asymmetry
S
D
t
DDDk SSSeff
eff
F
WbF
effD
WbDW k
Jk
JAJ expexp ,
,, pp
F
WbF
S
WbDW k
JD
SJAJ expexp ,, pp
mFmDW AJ ,, pp
FDW AJ pp
Low S means high water flux performance
(as long as the membrane can be handled and manufactured)
McCutcheon, J.R., Elimelech, M. “Influence of concentrative and
dilutive internal concentration polarization on flux behavior in
forward osmosis”, Journal of Membrane Science 284, 2006, 237-
247.
Desired Properties of FO Membranes
27
Requires anisotropic membrane
with appropriate polymers (like
TFC RO membranes)
High permeability
High selectivity
Chemical resistance
Thermal stability
Support layers that are thin,
highly porous, non-tortuous
(low S) and hydrophilic
+
Requires new
membrane designs,
materials, and
formation techniques
Mechanically
strong
+
For fabrication
and handling
Tolerate high
pressure
For pressure
retarded
osmosis
Easy to
manufactureLarge areas
needed
Properties of RO Membranes
• 60 year old technology
• Easy to manufacture
• Low selectivity
• Low permeance
• Common in UF and MF,
specialty RO
• 30 year old technology
• Tunable properties
• High selectivity
• High permeance
• Vast majority of RO
membranes
Commercial Membranes for FO
Ren, J., McCutcheon, J.R.
Desalination 343, 2014, 187-
193.Garcia-Castello, E.M., McCutcheon, J.R., and
Elimelech, M. Journal of Membrane Science
338, 2009, 61-66.
Arena, J.T., Manickam, SS,
Reimund, K.K., Brodskiy, P.,
McCutcheon, J.R. Industrial &
Engineering Chemistry Research.
In revision
What folks care about
• Membrane
• Draw solution
• Process design
29
What Makes a Good Draw Solution:
General Criteria
• Osmotic efficiency: Low molecular weight and high solubility
• Removable, recoverable, or useable: Low value energy for reuse
• Non toxic: Trace amounts may reside in the water
• System compatible: Does not degrade the membrane or the system
30
What Makes a Good Draw Solution?
31
What Makes a Good Draw Solution?
32
Criteria
Osmotic Efficiency
Recoverable
Non Toxic
System Compatible
Comments
What Makes a Good Draw Solution?
33
Criteria FO
Osmotic Efficiency
Yes
Recoverable Essential
Non Toxic Yes
System Compatible
Yes
CommentsMinimal leakage
What Makes a Good Draw Solution?
34
Criteria FO Dewatering
Osmotic Efficiency
Yes Yes
Recoverable Essential Optional
Non Toxic Yes Optional
System Compatible
Yes Yes
CommentsMinimal leakage
Minimal leakage
What Makes a Good Draw Solution?
35
Criteria FO DewateringOsmotic dilution
Osmotic Efficiency
Yes Yes Yes
Recoverable Essential Optional No
Non Toxic Yes OptionalEnd use
dependent
System Compatible
Yes Yes Yes
CommentsMinimal leakage
Minimal leakage
Direct use required
What Makes a Good Draw Solution?
36
Criteria FO DewateringOsmotic dilution
Open Loop PRO
Osmotic Efficiency
Yes Yes Yes Yes
Recoverable Essential Optional No No
Non Toxic Yes OptionalEnd use
dependentNo
System Compatible
Yes Yes Yes Yes
CommentsMinimal leakage
Minimal leakage
Direct use required
Naturally Occurring
What Makes a Good Draw Solution?
37
Criteria FO DewateringOsmotic dilution
Open Loop PRO
Closed Loop PRO
Osmotic Efficiency
Yes Yes Yes Yes Yes
Recoverable Essential Optional No No Essential
Non Toxic Yes OptionalEnd use
dependentNo No
System Compatible
Yes Yes Yes Yes Yes
CommentsMinimal leakage
Minimal leakage
Direct use required
Naturally Occurring
Leakage OK
Switchable polarity solvents
(CO2-catalyzed acid base
reaction)
Volatile solutes (ethanol,
etc.)
Polymers and hydrogels with
low lower critical solution
temperature
Solutes containing ammonia
and/or carbon dioxide
Recoverable Draw Solutes
38
Physically
Recoverable
Thermolytic
Decomposition
Thermal
Solubility
Phase
Switching
Distillable
Novel Draw SolutesIonic solutes or
magnetic nanoparticles
What folks care about
• Membrane
• Draw solution
• Process design
39
Commercialization of Forward
Osmosis
40McGinnis, et. al., Desalination, 312 (2013) 67-74
Hydration Technology Innovations:
Produced Water
• Saves nearly 1 million gallons of water per well (20% of total fluid need)
• Up to 150 fewer truck loads per well
41http://www.htiwater.com/divisions/oil-gas/lead_story.html
Hydration Technology Innovation:
Osmotic Dilution
Can produce a clean, safe drink from nearly
any water source
42http://www.htiwater.com
Butler, Desalination 312 (2013), 23-30
Modern Water:
Forward Osmosis Seawater Desalination
Claims lower energy use and
fouling combined with
high boron rejection
43
http://www.modernwater.co.uk/
Oasys Water:
Oilfield Produced Water
44McGinnis, et. al., Desalination, 312 (2013) 67-74
42% reduction in cost compared to distillation
Statkraft:
Open Loop Pressure Retarded Osmosis
45
Now divested from PRO
Your experiments
Reverse Osmosis
• Evaluate performance of reverse
osmosis/nanofiltration membrane
• NaCl/MgSO4
• Control temperature, flow rate,
pressure
What you will measure
𝑱𝒘 =∆𝒎
𝑨𝒎 × 𝝆 × 𝒕Jw = Water Flux
∆m = Mass change in balance
𝜌 = Density of water
t = Time
Am = Membrane area
𝑱𝒔 =∆𝒄
𝑨𝒎 × 𝒕Js = Solute flux
∆c = Concentration difference
between feed and permeate
𝑨 =𝑱𝒘∆𝑷
𝑩 = 𝑱𝒘𝟏 − 𝑹
𝑹𝒆𝒙𝒑 −
𝑱𝒘𝒌𝒎𝒕
𝑱𝒔 = 𝑩 × ∆𝑪
Pure water
permeance
Solute
permeability
% Rejection 𝑹 = 𝟏 −𝑪𝒑
𝑪𝒃
k
J
D
J
c
c WW
b
m expexp
Concentration Polarization
48
Turbulent
Laminar mass-transfer boundary
layer
Permeate water flux
JW
c
x
pWW cJdx
dcDcJ
D
J
cc
ccW
pb
pm exp
cm
cb
cp
Integrate over
cp << cm,cbCP
modulus
Dk
Solute balance:
Forward Osmosis
• Commercial FO
membrane
• NaCl draw solution
• Evaluate effects of
concentration
polarization
• Control temperature,
flow rate, draw
concentrationWhat you will measure
𝑱𝒘 =∆𝒎
𝑨𝒎 × 𝝆 × 𝒕Jw = Water Flux
∆m = Mass change in balance
𝜌 = Density of water
t = Time
Am = Membrane area
𝑱𝒔 =∆𝒄
𝑨𝒎 × 𝒕Js = Solute flux
∆c = concentration change from
beginning to end of test