Science and Technology for
Sustainable Water Supply
Menachem Elimelech
Department of Chemical Engineering
Environmental Engineering Program
Yale University
“Your Drinking Water: Challenges and Solutions for
the 21st Century”, Yale University, April 21, 2009
The “Top 10” Global Challenges
for the New Millennium
1.
Energy
2. Water
3.
4.
5.
6.
7.
8.
9.
10.
Food
Environment
Poverty
Terrorism and War
Disease
Education
Democracy
Population
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 Opportunities
We 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)
Source of water
supply for
commercial and
industrial sectors
(10% of water
demand)
4 NEWater plants
supplying 50 mgd
of NEWater.
5 miles
Will meet 15% of
water demand by
2011
Reuse of Wastewater in Orange
County, California
www.gwrsystem.com
Groundwater Replenishment
System, GWR (70 MG/day))
Prado
Dam
Santa Ana River Facilities
GWR System for Advanced Water
Purification (Orange County)
Microfiltration
(MF)
OCSD
Secondary
WW
Effluent
Reverse
Osmosis
(RO)
Ultraviolet
Light with
H 2 O2
Recharge
Basins
Namibia, Africa
Natural Beauty … but not Enough
Water
Windhoek’s Solution: Wastewater
Reclamation for Direct Potable Use
Goreangab Reclamation Plant (Windhoek)
“Water should not be
judged by its history,
but by its quality.”
Dr. Lucas Van Vuuren
National Institute of Water
Research, South Africa
The only wastewater reclamation plant
in the world for direct potable use
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
amphiphilic copolymer added
to casting solution
segregate & self-organize
at membrane surfaces
PEO brush
layer on
surface and
inside pores
Casting
Solution
Casting Solution
Doctor
Blade
Doctor Blade
Coagulation
Coagulation
Bath
Bath
Heat
Treatment
Heat Treatment
Bath
Fouling
Resistance
Asatekin, Kang, Elimelech, Mayes, Journal of Membrane Science, 298 (2007) 136-146.
Fouling Reversibility (with
Organic Matter)
White: Pure water
Gray: recovered flux
after fouling/cleaning
(following “physical”
cleaning (rinsing)
with no chemicals)
Shannon, Bohn, Elimelech, Georgiadis, and Mayes, Nature 452 (2008) 301-310.
AFM as a Tool to Optimize
Copolymer for Fouling Resistance
4
F/R (mN/m)
2
0
-2
-4
-6
-8
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
Normalized flux
1.4
1.2
1.0
0.8
PVDF-g-POEM (●,●)
0.6
PVDF base (,)
0.4
0.2
0.0
0
12
Time (hours)
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
OMBR SYSTEM
RO
DISINFECTION
Wastewater
Sludge
Achilli, Cath, Marchand, and Childress, Desalination, 2009.
Potable
water
Reversible Fouling: No Need for
Chemical Cleaning
29
6
4
2
0
0
Fouling
Flux after
cleaning
14
7
0
500 1000 1500 2000
Time (min)
Mi and Elimelech, in preparation.
22
Flux (l/m /h)
8
36
2
Flux of clean membrane
Cleaning
Flux (m/s)
10
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
3
Minimum Energy (kW-h/m )
independent of the technology or mechanism of
desalination
V
1
W
V1  V2
3.5
O
100 C
O
25 C
3.0
2.5

2.0
1.5
0.5
0
20
40
60
80
Percent Recovery
100

os
dV
V1
Minimum theoretical energy
for desalination:


1.0
2
0% recovery: 0.7 kWh/m3
50% recovery: 1 kWh/m3
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
Mauter and Elimelech,
Environ. Sci. Technol., 42
(16), 5843-5859, 2008.
Single-walled carbon nanotubes (SWNTs) with a pore
size of ~ 0.5 nm are critical for salt rejection
Higher nanotube density and purity
Large scale production?
Bio-inspired High Flux
Membranes for Desalination
Natural 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

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
Shannon, Bohn, Elimelech, Georgiadis, and Mayes, Nature 452 (2008) 301-310.
Desalination:
Forward Osmosis
The Ammonia-Carbon Dioxide Forward
Osmosis Desalination Process
Nature, 452, (2008) 260
Energy
Input
McCutcheon, McGinnis, and Elimelech, Desalination, 174 (2005) 1-11.
NH3/CO2 Draw Solution
NH3(g)
CO2(g)
NH3(g)
CO2(g)
NH4HCO3(aq)
(NH4)2CO3(aq)
NH4COONH2(aq)
HEAT
High Water Recovery with FO
 (atm)
450
400
350
300
250
200
150
100
50
0
RO
FO
Seawater
0 10 20 30 40 50 60 70 80 90 100
Recovery (%)

Energy Use by Desalination
Technologies (Equivalent Work)
6
5
kWh/m
3
4
MSF
MED-TVC
MED-LT
RO
FO-LT
3
2
1
0
McGinnis and Elimelech, Desalination, 207 (2007) 370-382.
Contribution from
Electrical Power
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, costeffective technologies appropriate for
different regions of the world
Acknowledgments