latest technologies in water desalination

Latest Technologies in Water Desalination

Amy E. Childress Department of Civil and Environmental Engineering

University of Nevada, Reno

1st Arab-American Frontiers Symposium Kuwait Institute for Scientific Research and U.S. National Academies

October 17-19, 2011 in Kuwait City

Outline

S  Introduction S  Fresh water scarcity S  Alternate sources and new technologies S  Desalination by reverse osmosis

S  Emerging Technologies for Desalination Applications S  Membrane Distillation

S  Forward Osmosis S  Pressure Retarded Osmosis

S  Final Remarks

Global Water Stress

Forcing water providers to rely more on alternative sources

Alternative Sources and New Technologies

Saline waters “Waste” waters

New concerns Salinity

Recovery Energy

Emerging Contaminants

Membrane Distillation

(MD)

Forward Osmosis

(FO)

Pressure Retarded Osmosis (PRO)

Desalination Applications and Salinity Levels

S  Seawater desalination (35-41 g/L)

S  In-land groundwater desalination (2-6 g/L) S  RO brine (>40 g/L)

S  Extreme salinity scenarios (>100 g/L) S  Oil and gas applications S  Mineral mining (water is by-product)

Current Leading Desalination Technology: Reverse Osmosis

Reverse Osmosis Separation

S  Produces water with <500 mg/L salts S  Less energy intensive than distillation (~10x less) S  But… does have drawbacks

1. passage of some contaminants 2. reduced driving force at high salt concentrations 3. membrane fouling

→ dual osmotic barrier (FO/RO) or MD → osmotic dilution or MD

PΔFeed

Concentrate Permeate

→ FO as pretreatment for RO

In-Land Desalination

Drinking water

Concentrate

Brackish Groundwater Feed Drawback 4. Brine Disposal or Treatment → FO/RO or MD

Seawater Desalination

Drinking water

Concentrate

High pressure

Low pressure Pressurized Feed

Seawater Desalination

Drinking water

Pressurized Feed

Concentrate

High pressure

Low pressure

Pressure

Seawater Desalination

Drinking water

Concentrate

High Salinity

Environmental Concern Waste of Chemical Energy Pressurized Feed

Emerging Technologies:

Membrane Distillation (MD)

Forward Osmosis (FO) Pressure Retarded Osmosis (PRO)

Direct Contact Membrane Distillation

Driving force: vapor pressure gradient

Heated Feed Stream Cooler Distillate Stream

Hydrophobic, Microporous Membrane

Driving Force in MD

Addresses RO Drawback 1: Reduced Driving Force at High Salt Concentration

Industrial Mineral Harvesting Great Salt Lake, Utah

Tzahi Cath’s Lab at Colorado School of Mines

Desalination of Hypersaline Lake Water

Constituent g/L Cl 83

SO4 10

Ca 0.3

K 3 Li 0.03 Mg 6 Na 47

TDS 149 g/L

0

10

20

30

40

50

60

0

2

4

6

8

10

12

0 20 40 60

Bat

ch r

eco

very

, %

Wat

er f

lux

, LM

H

Time, hr

> 300 g/L

Removal of Emerging Contaminants

0 10 20 30 40 50 60 70 8050

60

70

80

90

100

EDC

Rej

ectio

n, %

Water Recovery, %

estradiol in Soap Solution estrone in Soap Solution estrone in DDW

0 10 20 30 401.0

1.5

2.0

2.5

3.0

3.5

water flux

Elapsed Time, hr

Wat

er F

lux,

L/m

2 -hr

80

85

90

95

100(a)

estrone rejection estradiol rejection

ED

C R

ejec

tion,

%

Membrane Distillation Osmotic Processes

Addresses RO Drawback 3: Passage of Some Contaminants

Salinity Gradient Solar Pond

Membrane Distillation

Membrane Distillation with Solar Energy

Solar Thermal, Geothermal Waste Heat

Stand-alone energy collection/storage and water desalination

Emerging Technologies:

Membrane Distillation (MD)

Forward Osmosis (FO) Pressure Retarded Osmosis (PRO)

Emerging Technology: Forward Osmosis

Osmosis and Forward Osmosis

Brine

Water

Equilibrium

osmotic pressure

Brine

Water

membrane

Osmosis

Feed Water

Forward Osmosis

Conc Draw

Solution

ConcentratedDraw Solution

Diluted Draw Solution

salt

Reverse Osmosis

Forward Osmosis

Impaired Water

Concentrated Impaired water Clean Water

water

FO Pretreatment for RO (General Concept)

Addresses RO Drawback 3: Membrane Fouling Addresses RO Drawback 3: Passage of Some Contaminants

Ammonia-Carbonate FO Process

Saline Water

Draw Solution NH3/CO2

Product Water

Brine

Membrane

Column Distillation

Has potential to require less energy than FO/RO

waste heat

Meny Elimelech’s Lab at Yale University

Emerging Technologies:

Membrane Distillation (MD)

Forward Osmosis (FO) Pressure Retarded Osmosis (PRO)

Brine

Water

membrane

Osmosis

Brine

Water

Reverse Osmosis (RO)

pressure>osmotic pressure

Brine

Water

Pressure Retarded Osmosis (PRO)

pressure<osmotic pressure

Osmotic pressure

What is Pressure-Retarded Osmosis?

S  An osmotically driven membrane process similar to RO and FO

S  An osmotically driven membrane process similar to RO and FO S  A source of renewable and sustainable energy

What is Pressure-Retarded Osmosis?

SALINATION Seawater Freshwater

Energy

PRECIPITATION

global energy production from mixing in estuaries: 2,000 TWh/y current global energy production from all renewable sources: 10,000 TWh/y

River 5 g/L Ocean 35 g/L

S  An osmotically driven membrane process similar to RO and FO S  A source of renewable and sustainable energy

S  A process of capturing the energy released from the mixing of

freshwater with saltwater

What is Pressure-Retarded Osmosis?

River Ocean Δπ=22.5 atm

S  An osmotically driven membrane process similar to RO and FO S  A source of renewable and sustainable energy

S  A process of capturing the energy released from the mixing of

freshwater with saltwater

What is Pressure-Retarded Osmosis?

River

Ocean

225 m

S  An osmotically driven membrane process similar to RO and FO S  A source of renewable and sustainable energy

S  A process of capturing the energy released from the mixing of

freshwater with saltwater

What is Pressure-Retarded Osmosis?

Power Generation with PRO

Norman, 1974

chemical potential transformed to hydraulic potential

PRO System

Achilli, Cath, Childress, 2009 Adapted from Loeb, 2002

Diluted seawater

Low pressure

pump

Low pressure

pump

Seawater

Pressure exchanger

Circulation pump

Diluted seawater

Fresh water Flushing solution

Hydroturbine and generator

Draw solution side

Feed solution side

Seawater

Diluted seawater

Pumps

Membrane

Net power

H

L

Seawater Desalination

Drinking water

Concentrate

High Salinity

Environmental Concern Waste of Chemical Energy Pressurized Feed

Drinking water

Feed

High pressure

Proposed Energy Recovery in Seawater Desalination

Impaired water

Osmotic pump

1- Energy generation 2 - Concentrate dilution

1

2

Final Remarks S  There is no single best method for desalination

S  Water source and energy availability S  Treatment needs S  Sustainability considerations

S  The needs for all processes are similar:

S  Commercial competition for membranes S  New membrane modules / packing S  Cost models

S  MD, FO, and PRO have implications for wastewater reuse

Acknowledgements S  California Department of Water Resources S  National Aeronautics and Space Administration S  Office of Naval Research S  U.S. Bureau of Reclamation S  U.S. Department of Energy S  Hydration Technology Innovations

S  Dr. Andrea Achilli S  Dr. Tzahi Cath S  Dr. Scott Tyler S  Dr. Francisco Suarez S  Katie Bowden, Jeri Prante,

Guiying Rao, Jeff Ruskowitz

amyec@unr.edu