The Promise of Forward Osmosis

Department of Chemical Engineering

Menachem Elimelech

Department of Chemical EngineeringEnvironmental Engineering Program

Yale University

World Class University Program

School of Civil, Environmental & Architectural Engineering

Korea University

Waterworks Research Institute Seoul Metropolitan Government

August 13, 2009

Motivation: Augment Water

Supply

� Droughts and water shortages

� Need to increase water supply

by producing new water

� Viable options for new water:

� Wastewater reuse

� Desalination of sea/brackish

water

Need for Sustainable

Technologies

� Develop water/wastewater

treatment technologies that

• Use less energy

• Require less chemicals• Require less chemicals

• Have lower impact on the

environment

� Osmotically-driven membrane

processes, or forward osmosis

(FO), may be a promising option

What is Forward Osmosis?

Reverse Osmosis

Hydraulic

Pressure

Feed

Permeate

M

E

M

B

R

water

( )mw PAJ ∆Π−∆=

Pressure

water

PermeateR

A

N

E

What is Forward Osmosis?

Reverse Osmosis

Hydraulic

Pressure

Feed

Permeate

M

E

M

B

R

water

Forward Osmosis

M

E

M

B

R

water

Permeate

Draw

Solution

Feed

( )mw PAJ ∆Π−∆=

Pressure

water

PermeateR

A

N

E

mw AJ ∆Π=

R

A

N

E water

Solution

Permeate

Forward

Osmosis

Osmosis

Reverse

Osmosis

p=π p>π

π

OsmosisOsmosis

Seawater or

brackish water

FreshwaterMembrane

Draw

Solution

Forward Osmosis

Forward Osmosis Process

Membrane

Draw

Solution

Feed water

Diluted Draw solution

Solution

Recovery

Process

Product

waterConcentrate Concentrated

Draw Solution

Applications of

Forward OsmosisForward Osmosis

Hydration Bags

Wastewater Treatment with

Forward Osmosis

Feed

water

Draw Solution (Salt)

Forward

Membrane Membrane

Reverse

water

Clean

WaterConcentrate

Disposal

watersaltForward

Osmosis

water

Reverse

Osmosis

Diluted Draw Solution

Membrane Bioreactor (MBR) for

Wastewater Treatment

Wastewater Reuse: Membrane

Bioreactor (MBR)-RO System

Osmotic MBR-RO: Multiple

Barrier Wastewater Treatment

Osmotic MBR

DisinfectionWastewater

RO

Draw

Concentrated

Draw Solution

(Salt)

Achilli et al., Desalination, 2008

Potable

water

Sludge

Solution

Recovery

Process

Diluted

Draw Solution

M1

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M1 M1 M1 M1 This you can modifu as you wish. See original paper...

May use similar style as previous slideMeny Elimelech, 2009-07-31

Desalination by Forward Osmosis:

The Ideal Draw Solution

� Highly soluble solution to generate high

osmotic pressure gradient

� Recoverable and recyclable� Recoverable and recyclable

� Soluble species should not pass through

the membrane

NH3/CO2 Draw Solution

NH3(g) CO2(g)

NH3(g) CO2(g)

NH4HCO3(aq)

(NH4)2CO3(aq)

NH4COONH2(aq)

HEAT

The Ammonia-Carbon Dioxide FO

Desalination Process

Energy

Input

Nature, 452, (2008) 260

Desalination, 174 (2005) 1-11.

High Water Recovery with FO

RO FO

250

300

350

400

450

π (atm)

Seawater π

0 10 20 30 40 50 60 70 80 90 1000

50

100

150

200π (atm)

Recovery (%)

Osmotic Heat Engine

Q in

Heat Engine Work

Q out

Heat Engine Work

NH3/CO2 Osmotic Heat Engine:

Closed Loop PRO

JMS, 305 (2007) 13-19; ES&T, 42 (2008) 8625-8629.

Water Flux in Forward

OsmosisOsmosis

Effect of Membrane Design on

FO Water Flux

12

16CA

Flux (

µm/s)

Flux (gfd)

4

6

8

0

4

8

6M Draw/0.5M Feed, 50˚C

CEAG

Flux (

Flux (gfd)

0

2

4

Desalination, 174 (2005) 1-11.

SEM Cross Sections

CE

(RO)

Red lines indicate 50 µµµµm

AG

(RO)

CA (FO)

Forward Osmosis Membrane

50 µµµµm

10 µµµµm10 µµµµm

Forward Osmosis Membrane

Active Layer Backing Layer

– Asymmetry observed at high magnification

300 nm 300 nm

ππππD,b

Active

Layer

Draw

Solution

Crossflow

Internal CP

Major Challenge: Internal

Concentration Polarization

∆πTheo

Water flux

ππππF,b

∆πeff

External CP

Feed

Crossflow

Crossflow

Diffusion

theoeff ππ ∆<<∆

( )FW

bF

mFkJ /exp

,

, =π

π( )KJWbD

mD −= exp,

,

π

π

Modeling Internal CP

Draw Side Feed Side ππππD,b

∆πTheo

∆π

ππππD,m

)( ,, mFmDW AJ ππ −=

( )

−−=

F

WbFWbDW k

JKJAJ expexp ,, ππ

ππππF,b

∆πeff ππππF,m

Characterizing the Support Layer

ετD

tK =

K solute resistance to diffusion

t support layer thickness

τ tortuosity

ε porosity

D draw solute diffusivity

6

8

10

Flux (gfd)

40 C

30 C

20 C

m/s) 15

20

Quantifying Internal CP

0 20 40 60 80

2

4

6

Flux (gfd)

Flux (

µm/s)

πD,b-π

F,b (atm)

5

10

System Conditions

Draw: 0 to 1.5 M NaCl

Feed: Deionized water

∆π

6

8

10

Flux (gfd)

40 C

30 C

20 C

m/s) 15

20

Quantifying Internal CP

0 20 40 60 80

2

4

6

Flux (gfd)

Flux (

µm/s)

πD,b-π

F,b (atm)

5

10

System Conditions

Draw: 1.5 M NaCl

Feed: 0 ���� 1 M NaCl

∆π

Modeling Internal CP

( )

−−=

F

WbFWbDW k

JKJAJ expexp ,, ππ

τtε

τD

tK =

6

8

10

Flux (gfd)

Experimental

Model

Flux (

µm/s)

12

16

20

6

8

10

Flux (gfd)

Experimental

Model

Flux (

µm/s)

10

15

20

30 oC 40 oC

Modeling Internal CP

0 20 40 60 80

2

4

Flux (gfd)

Flux (

πD,b-π

F,b (atm)

4

8

0 20 40 60 80

2

4

Flux (gfd)

Flux (

πD,b-π

F,b (atm)

5

10

Thickness, t

thin film (active layer)

Support

layer

Characterizing the Support Layer

Tortuosity, τ Porosity, ε

Red lines indicate 50 µµµµm

CE

AG

CA

ετD

tK =

ππππDraw

∆π

∆πeff

Convection

Diffusion

Porous

support

Active

layer

τεS

eff

DD =

Driving Force in the NH3/CO2 OHE

Draw

crossflow

∆πTheo

Water

flux

ππππFeed

Dilutive ECP

Negligible

Concentrative

ICP

τ

Working Fluid

(Deionized

water)

Salt flux

P

)( effW AJ π∆=

Very High Water Fluxes

40

50

60

2-s)

20

25

50 100 150 200 250

0

10

20

30

40

Flux (

10−6

m3/m

2

Pure water (40 oC)

Pure water (20 oC)

40 oC

20 oC

Flux (gfd)

Driving Force (atm)

0

5

10

15

20

Very High Membrane Power Density

250

300

5.5 M (257 atm)

5.0 M (224 atm)

4.6 M (197 atm)

3.7 M (148 atm)

3.2 M (128 atm)

Energy Production (W/m

2)

50 100 150 2000

50

100

150

200

250

Energy Production (W/m

Hydraulic Pressure (atm)

3.2 M

3.7 M 4.6 M

5.0 M

5.5 M

Fouling and Fouling

ReversibilityReversibility

Organic Fouling Reversibility in

Forward Osmosis

6

8

10

22

29

36Flux of clean membrane

Flux (l/m

2/h)

m/s) � FO membrane: CA

(Hydration Tech)

� Organic foulant (200

0 500 1000 1500 20000

2

4

6

0

7

14

22Flux after

cleaning

Flux (l/m

Flux (

µm/s)

Time (min)

Fouling Cleaning

� Organic foulant (200

mg/L alginate); 50 mM

NaCl; 0.5 mM Ca2+

� Cleaning: 50 mM

NaCl, 15 min

Organic Fouling Reversibility

0.4

0.6

0.8

1.0

Flux recovery by cleaning

Flux after fouling

Norm

alized Flux

8.5 cm/s, NaCl, 1hr

8.5 cm/s, NaCl, 5hr

8.5 cm/s, NaCl, 24hr

21 cm/s, NaCl, 15 mins

21 cm/s, DI, 15 mins

21 cm/s, bubble DI, 1 mins

21 cm/s, bubble DI, 5 mins

0.0

0.2

Norm

alized Flux

Cleaning Conditions

Organic Fouling Reversibility:

FO versus RO

6

8

10

12

22

29

36

43

FO- CA

RO- CA

RO- PA

Flux (l/m

2/h)

µm/s)

0.6

0.8

1.0

Flux recovery by cleaning

Flux after alginate fouling

Norm

alized Flux

0 500 1000 15000

2

4

6

0

7

14

22

Fouling solution: 200 mg/L alginate,

50 mM NaCl, 0.5 mM CaCl2

Flux (l/m

Flux (

µ

Time (min)FO-CA RO-CA RO-PA

0.0

0.2

0.4

Norm

alized Flux

� FO – CA: CA membrane in FO mode

� RO – CA: CA membrane in RO mode (hydraulic pressure)

� RO – PA: Polyamide TFC membrane in RO mode

FO Exhibits Fouling Reversibility

with a Wide Range of Foulants

0.8

1.0

Flux recovery by rinsing

Flux after fouling Norm

alized Flux

Alginate BSA GypsumSilica0.0

0.2

0.4

0.6

Norm

alized Flux

Foulant Type

Concluding RemarksForward osmosis can be used as a

standalone process or as part of an hybrid

system (e.g. FO-RO)

Forward osmosis is less prone to fouling; may Forward osmosis is less prone to fouling; may

use less prime (electric) energy

Need to develop an appropriate membrane

with low internal concentration polarization

Acknowledgments

Graduate Students/Postdocs: Jeffrey McCutcheon, Robert

McGinnis, Baoxia Mi, Sangyoup Lee

World Class University (WCU) project (No. R33-2008-000-

10046-0)

The Ministry Education, Science, and Technology, KoreaThe Ministry Education, Science, and Technology, Korea

Korea Science and Education Foundation (KOSEF)

US Office of Naval Research; NSF through WaterCAMPWS