Forward Osmosis: Progress and Challenges

Department of Chemical and Environmental Engineering Yale University

New Haven, Connecticut

Menachem Elimelech

2014 Clarke Prize Conference, November 7, 2014, Huntington Beach, California

Water Flux Eqn:

Feed

Permeate

mw PAJ

Hydraulic Pressure

water

MEMBRANE

water

Wa

ter

flu

x, J

w

P

0

RO (P > )

Reverse Osmosis (RO)

MEMBRANE

water

water

Draw Solution

Feed

Permeate

Water Flux Eqn:

mw AJ

Wa

ter

flu

x, J

w

P

0

FO (P = 0)

Forward Osmosis (FO)

Wa

ter

flu

x, J

w

P

0

Flux reversal point (P = )

PRO (P < )

MEMBRANE

water

water

Pressurized Draw

Solution Feed

Permeate

Water Flux: PAJ mw

Pressure Retarded Osmosis (PRO)

Wa

ter

flux,

Jw

P

0

Flux reversal point (P = )

PRO (P < )

Engineered Osmosis

RO (P > )

FO (P = 0)

Overview of Presentation

Energy Aspects of Forward Osmosis Fouling Propensity and Reversibility in Forward Osmosis Desired Membrane Properties and Reverse Solute Flux Applications of Forward Osmosis

Membrane

Draw Solution Recovery Process

Product water

Feed Water

Concentrate

Diluted Draw Solution

Concentrated Draw Solution

Energy Input

The Forward Osmosis Process

Energy Input in FO: “No Free Lunch.”

Can’t beat thermodynamics Separation energy of draw solution is proportional to the osmotic pressure of draw solution Input energy > energy equivalent to draw solution osmotic pressure Potential innovations through use of low-cost forms of energy (e.g., low-grade heat), rather than prime (electric) energy

SE = ΔP ≥ πΒ (R) Permeate

Brine

SE: Specific energy ΔP: Applied pressure πΒ(R): Brine osmotic pressure at recovery R

RO Energy Consumption

Shaffer et al. (2014), in press, 10.1016/j.desal.2014.10.031.

SEmin= πΒ

SEmin= πD

πD is always > πΒ

Permeate Brine Draw

Comparing Energy of RO and FO-RO

SEmin (FO-RO) = πD > πΒ = SEmin (RO)

Condition for net driving force in FO

FO-RO Always Requires More Energy than RO Alone

Overview of Presentation

Energy Aspects of Forward Osmosis Fouling Propensity and Reversibility in Forward Osmosis Desired Membrane Properties and Reverse Solute Flux Applications of Forward Osmosis

Organic Fouling Reversibility in Forward Osmosis

0 500 1000 1500 20000

2

4

6

8

10

0

7

14

22

29

36Flux of clean membrane

Flux after

cleaning

Flu

x (

l/m

2/h

)

Flu

x (m

/s)

Time (min)

Fouling Cle

an

ing

FO membrane: CA (Hydration Tech)

Organic foulant (200 mg/L alginate); 50 mM NaCl; 0.5 mM Ca2+

Cleaning: 50 mM NaCl, increased crossflow, 15 min

Mi and Elimelech, Journal of Membrane Science, 348 (2010) 337–345.

FO Exhibits Fouling Reversibility with a Wide Range of Foulants

Alginate BSA Gypsum Silica0.0

0.2

0.4

0.6

0.8

1.0

Flux recovery by rinsing

Flux after fouling

No

rma

lize

d F

lux

Foulant TypeShaffer et al. (2014), in press, 10.1016/j.desal.2014.10.031.

In Situ Surface Modification for Fouling Resistance

C O Cl

C O Cl

C O Cl NH2-PEG

Interfacial Polymerization

Polysulfone Support Layer Nascent Polyamide Layer

PEGylation

In Situ Modified Membrane

C O NH

PEG

C O NH

PEG

MPD+TMC

Control In Situ Modified0

20

40

60

80

100

120

Control In Situ Modified

Con

tact

Ang

le (°

)

Lu et al. Environ. Sci. Technol. 2013, 47, 12219−12228.

Modified Membrane Exhibits Organic Fouling Resistance

Control In Situ Modifed

80

85

90

95

100

Nor

mal

ized

Wat

er F

lux,

Jw/J

w,0(%

)

Fouling Cleaning

0 100 200 300 400 500

80

85

90

95

100

Polyamide In Situ Modified

Nor

mal

ized

wat

er fl

ux, J

w/J

w,0(%

)

Cumulative Permeate Volume (ml)

Control

Lu et al. Environ. Sci. Technol. 2013, 47, 12219−12228

Overview of Presentation

Energy Aspects of Forward Osmosis Fouling Propensity and Reversibility in Forward Osmosis Desired Membrane Properties and Reverse Solute Flux Applications of Forward Osmosis

D

tK

s

Tortuosity,

Porosity,

Thickness, ts

thin film (active layer) support

layer

K Solute resistance to diffusion ts Support layer thickness Tortuosity

Porosity D Draw solute diffusivity

Membrane structural parameter,

S

Current Focus: Reducing Structural Parameter of Membranes

S = 9583 μm

TFC-RO

S = 390 μm

TFC-FO

Significant Progress in the Past 10 Years

Yip et al. Environ. Sci. Technol. 2010, 44, 3812–3818

Low Structural Parameter is Critical for Obtaining High Water Flux

Shaffer et al. (2014), in press, 10.1016/j.desal.2014.10.031.

Challenge: Minimize Reverse Draw Solute Flux

Membrane

Draw Solution Recovery Process

Product water

Feed Water

Concentrate

Diluted Draw Solution

Concentrated Draw Solution

Js

The Driving Force for Reverse Draw Solute Permeation

A highly concentrated draw solution generates the osmotic gradient that drives the flux of water

The high concentration of draw solute also drives the reverse permeation of draw solute.

w mJ A

n

s mJ f c

Js

Jw

Feed Draw

Analytical Expression for Reverse Solute Flux

, ,exp exp

1 exp exp

w wD b F b

s

w w

w

J S Jc c

D kJ A

J J SB

J k D

, ,exp exp

1 exp exp

w wD b F b

w

w w

w

J S J

D kJ A

J J SB

J k D

Model Predicts Reverse Solute Flux for Salt and Neutral Solutes

0.01 0.1 1 10 100

0.01

0.1

1

10

100

Urea

Ethylene Glycol

Glucose

NaCl

Experimental Solute Flux (mol m-2 h

-1)

Pre

dic

ted

So

lute

Flu

x (

mo

l m

-2 h

-1)

180.2 g/mol

60.1 g/mol

62.1 g/mol

0.72 nm

Yong et al., Journal of Membrane Science 392–393 (2012) 9–17

Defined as ratio of forward water flux to reverse salt flux

Representative of the volume of water produced per moles (or mass) of solute lost

Depends solely on the membrane active layer permeability and selectivity

Reverse Flux Selectivity (RFS): An Important Design Parameter

TnRB

A

J

Jg

s

w

Membranes Are Constrained by the Permeability-Selectivity Tradeoff

Yip et al. Environ. Sci. Technol. 2011, 45, 10273–10282

Geise et al., Journal of Membrane

Science 2011, 369 (1-2), 130-138.

TnRB

A

J

Jg

s

w

Goal: Maximize B

A

Overview of Presentation Energy Aspects of Forward Osmosis Fouling Propensity and Reversibility in Forward Osmosis Desired Membrane Properties and Reverse Solute Flux Applications of Forward Osmosis

The Goal of FO is NOT to Replace RO!

RO is the Gold Standard for Desalination

FO can be used in Applications where RO cannot

Potential Applications of FO

High salinity feed waters that cannot be treated by RO (RO limited to feed water up to about 40,000 ppm)

Very difficult to treat feed waters (i.e., feed waters with very high fouling potential)

Zero liquid discharge (ZLD)

Pre-treatment to improve the performance of conventional desalination processes

Applications in Oil and Gas

Gregory et al., Elements, Vol. 7, 2011, 181–186

Applications in Oil and Gas: Very Hard to Treat Shale Gas Waters

Gregory et al., Elements, Vol. 7, 2011, 181–186 Upper Limit Conc. (mg/L)

TDS: 260,000

Hardness: 55,000

Alkalinity: 1,100

Calcium: 31,000

Cannot be treated by pressure-driven membrane processes (RO/NF)

The “Green Machine”: Treatment of Water from Hydraulic Fracturing

Source: Hydration Technologies Innovation (HTI)

Low-Grade Heat

Nature, 452, (2008) 260

McCutcheon et al., Desalination, 174 (2005) 1-11.

FO Desalination with Thermolytic Draw Solutions

Desalination 312 (2013) 67–74

Brine Concentrator for Treatment of High Salinity Shale Gas Wastewater

Oasys Water Inc.

TDS = 75,000 mg/L

TDS = 300 mg/L

FO in ZLD Schemes as Brine Concentrator

Shaffer et al. (2014), in press, 10.1016/j.desal.2014.10.031.

Pre-treatment for Conventional Desalination Technologies

Shaffer et al. (2014), in press, 10.1016/j.desal.2014.10.031.

Concluding Remarks The Promise • Low fouling propensity • Can treat high salinity brines • Can treat challenging wastewaters • Can be integrated with established technologies (e.g. RO)

and zero liquid discharge (ZLD) schemes

The Challenges • Development of low-cost high performance membranes • Minimizing reverse draw solute flux • More pilot demonstrations • Development of full-scale systems

Acknowledgments Current and former research group at Yale Collaborations: Korea University (Prof. S. Hong), Wollongong University (Prof. Long Nghiem Funding: National Science Foundation, Office of Naval Research, Department of Energy, US EPA, Cornell-KAUST