science and technology for sustainable water supply
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Science and Technology for Sustainable Water Supply
Menachem ElimelechDepartment of Chemical EngineeringEnvironmental Engineering Program
Yale University
“Your Drinking Water: Challenges and Solutions for the 21st Century”, Yale University, April 21, 2009
1. Energy2. Water3. Food4. Environment5. Poverty6. Terrorism and War7. Disease8. Education9. Democracy10. Population
The “Top 10” Global Challenges for the New Millennium
Richard E. Smalley, Nobel Laureate, Chemistry, 1996, MRS Bulletin, June 2005
International Water Management Institute
Regional and Temporal Water Scarcity
National Oceanic and Atmospheric Administration
How Do We Increase the Amount of Water Available to People? Water conservation, repair of infrastructure,
and improved catchment and distribution systems ― improve use, not increasing supply!
Increase water supplies to gain new waters can only be achieved by: Reuse of wastewater Desalination of brackish and sea waters
Many OpportunitiesWe are far from the thermodynamic limits for separating unwanted species from water
Traditional methods are chemically and energetically intensive, relatively expensive, and not suitable for most of the world
New systems based on nanotechnology can dramatically alter the energy/water nexus
Wastewater Reuse
Reclaimed Wastewater in Singapore (NEWater)
5 miles
Source of water supply for commercial and industrial sectors (10% of water demand)
4 NEWater plants supplying 50 mgd of NEWater.
Will meet 15% of water demand by 2011
Reuse of Wastewater in Orange County, California
Prado Prado DamDam
Santa Ana River FacilitiesSanta Ana River Facilities
Groundwater ReplenishmentSystem, GWR (70 MG/day))
www.gwrsystem.com
Ultraviolet Light with
H2O2
Microfiltration(MF)
Reverse Osmosis
(RO)OCSD OCSD
Secondary Secondary WW WW
Effluent
Recharge Basins
GWR System for Advanced Water Purification (Orange County)
Namibia, Africa
Natural Beauty … but not Enough Water
Windhoek’s Solution: Wastewater Reclamation for Direct Potable Use
“Water should not be judged by its history, but by its quality.”
Dr. Lucas Van VuurenNational Institute of Water Research, South Africa
The only wastewater reclamation plant in the world for direct potable use
Goreangab Reclamation Plant (Windhoek)
The Treatment Scheme: A Multiple Barrier Approach
Most Important: Public Acceptance and Trust in the Quality of Water
Breaking down the psychological barrier (the “yuck factor”) is not trivial
– Rigorous monitoring of water quality after every process step
– Final product water is thoroughly analyzed (data made available to public)
The citizens of Windhoek have a genuine pride in the reality that their city leads the world in direct water reclamation
Wastewater Reuse: Membrane Bioreactor (MBR)-RO System
Shannon, Bohn, Elimelech, Georgiadis, and Mayes, Nature 452 (2008) 301-310.
Fouling Resistant UF Membranes: Comb (PAN-g-PEO) Additives
Doctor Blade
Coagulation Bath
Casting Solution Heat Treatment
Bath
Casting Solution
Doctor Blade
Coagulation Bath
Heat Treatment
amphiphilic copolymer added to casting solution
segregate & self-organize at membrane surfaces
PEO brush layer on
surface and inside pores
Fouling Resistance
Asatekin, Kang, Elimelech, Mayes, Journal of Membrane Science, 298 (2007) 136-146.
Fouling Reversibility (with Organic Matter)
Gray: recovered flux after fouling/cleaning (following “physical” cleaning (rinsing) with no chemicals)
White: Pure water
Shannon, Bohn, Elimelech, Georgiadis, and Mayes, Nature 452 (2008) 301-310.
AFM as a Tool to Optimize Copolymer for Fouling Resistance
-8
-6
-4
-2
0
2
4
F/R
(m
N/m
)
PAN (P0-0) P50-5 P50-10 P50-20
Kang, Asatekin, Mayes, Elimelech, Journal of Membrane Science, 296 (2007) 42-50.
Wastewater Reuse: Membrane Bioreactor (MBR)-RO System
Shannon, Bohn, Elimelech, Georgiadis, and Mayes, Nature 452 (2008) 301-310.
One Step NF-MBR System?
NF
Antifouling NF Membranes for MBR (PVDF-g-POEM)Filtration of activated sludge from MBR– PVDF-g-POEM NF: no flux loss over 16 h filtration – PVDF base: 55% irreversible flux loss after 4 h
0 120.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
No
rma
lize
d f
lux
Time (hours)
PVDF base (,)
PVDF-g-POEM (●,●)
Asatekin, Menniti, Kang, Elimelech, Morgenroth, Mayes: J. Membr. Sci. 285 (2006) 81-89
Wastewater Reuse:Osmotically-Driven Membrane
Processes
Wastewater Reclamation with Forward (Direct) Osmosis
Wastewater
Concentrate Disposal
Osmotic MBR-RO: Low Fouling, Multiple Barrier Treatment
Achilli, Cath, Marchand, and Childress, Desalination, 2009.
OMBR SYSTEM
DISINFECTION Wastewater
Potablewater
Sludge
RO
Reversible Fouling: No Need for Chemical Cleaning
Mi and Elimelech, in preparation.
0 500 1000 1500 20000
2
4
6
8
10
0
7
14
22
29
36Flux of clean membrane
Flux aftercleaning
Flu
x (l/
m2 /h
)
Flu
x (
m/s
)
Time (min)
Fouling Cle
anin
g
Desalination:Reverse Osmosis
Population Density Near Coasts
Seawater Desalination
Augmenting and diversifying water supply
Reverse osmosis and thermal desalination (MSF and MED) are the current desalination technologies
Energy intensive (cost and environmental impact)
Reverse osmosis is currently the leading technology
Reverse Osmosis
Major improvements in the past 10 years
Further improvements are likely to be incremental
Recovery limited to ~ 50%: Brine discharge (environmental concerns)
Increased cost of pre-treatment
Use prime (electric) energy (~ 2.5 kWh per cubic meter of product water)
Minimum Energy of Desalination Minimum energy needed to desalt water is independent of
the technology or mechanism of desalination
2
121
1V
V
osdVVVW
Minimum theoretical energy for desalination:
0% recovery: 0.7 kWh/m3
50% recovery: 1 kWh/m3
0 20 40 60 80 1000.5
1.0
1.5
2.0
2.5
3.0
3.5
100 OC
25 OC
Min
imum
Ene
rgy
(kW
-h/m
3)
Percent Recovery
Nanotechnology May Result in Breakthrough Technologies
“These nanotubes are so beautiful that they must be useful for something. . .”, Richard Smalley (1943-2005).
Aligned Nanotubes as High Flux Membranes for Desalination?
Hinds et al, “Aligned multi-walled carbon nanotube membranes”, Science, 303, 2004.
Research on Nanotube Based Membranes
Mauter and Elimelech, Environ. Sci. Technol., 42 (16), 5843-5859, 2008.
Next Generation Nanotube Membranes
Single-walled carbon nanotubes (SWNTs) with a pore size of ~ 0.5 nm are critical for salt rejection Higher nanotube density and purityLarge scale production?
Mauter and Elimelech, Environ. Sci. Technol., 42 (16), 5843-5859, 2008.
Bio-inspired High Flux Membranes for DesalinationNatural aquaporin proteins extracted from living organisms can be incorporated into a lipid bilayer membrane or a synthetic polymer matrix
BUT …. Energy is Needed Even for Membranes with Infinite Permeability
Shannon, Bohn, Elimelech, Georgiadis, and Mayes, Nature 452 (2008) 301-310.
Minimum theoretical energy for desalination at 50% recovery: 1 kWh/m3
Practical limitations: No less than 1.5 kWh/m3
Achievable goal: 1.5 2 kWh/m3
Desalination:Forward Osmosis
The Ammonia-Carbon Dioxide Forward Osmosis Desalination Process
EnergyInput
Nature, 452, (2008) 260
McCutcheon, McGinnis, and Elimelech, Desalination, 174 (2005) 1-11.
NH3/CO2 Draw Solution
NH3(g) CO2(g)
NH4HCO3(aq)
(NH4)2CO3(aq)
NH4COONH2(aq)
HEAT
NH3(g) CO2(g)
High Water Recovery with FO
RO FO
0 10 20 30 40 50 60 70 80 90 1000
50100150200250300350400450
(atm)
Recovery (%)
Seawater
0
1
2
3
4
5
6
kW
h/m
3
MSF MED-TVC MED-LT RO FO-LT
Energy Use by Desalination Technologies (Equivalent Work)
Contribution fromElectrical Power
McGinnis and Elimelech, Desalination, 207 (2007) 370-382.
Waste Heat Geothermal Power
Concluding Remarks
We are far from the thermodynamic limits for separating unwanted species from water
Nanotechnology and new materials can significantly advance water purification technologies
Advancing the science of water purification can aid in the development of robust, cost-effective technologies appropriate for different regions of the world
Acknowledgments
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