Science and Technology for Sustainable Water Supply Menachem Elimelech Department of Chemical Engineering Environmental Engineering Program Yale University.

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