latest technologies in water desalination
TRANSCRIPT
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