REVERSE OSMOSIS AND

FORWARD OSMOSIS

LABORATORY EXPERIMENTS

Jeffrey McCutcheonAssociate Professor

University of ConnecticutDepartment of Chemical & Biomolecular Engineering

View video of lecture here:

https://youtu.be/aaq6SNvGKUo

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