Science and Technology for Sustainable Water Supply Menachem Elimelech Department of Chemical Engineering Environmental Engineering Program Yale U i Y l University itSeminar, University of Oklahoma, February 20,2009
The “Top 10” Global Challengesfor the New Millennium1.1 Energy2. Water3. Food4. Environment5. Poverty6. Terrorism and W T i d War7. Disease8.8 Education Richard E Smalley Nobel E. Smalley,9. Democracy Laureate, Chemistry, 1996,10. Population MRS Bulletin, June 2005
Regional and Temporal WaterScarcityS it National Oceanic and Atmospheric Administration
How Do We Increase the Amountof Water Available to People? Water conservation repair of infrastructure conservation, infrastructure, and improved catchment and distribution systems ― improve use not increasing use, supply! Increase water supplies t gain new waters I t li to i t can only be achieved by: Reuse of wastewater R f t t Desalination of brackish and sea waters
Many OpportunitiesWe are far from the thermodynamic limits forseparating unwanted species f ti t d i from water tTraditional methods are chemically and yenergetically intensive, relatively expensive,and not suitable for most of the worldNew systems based on nanotechnology candramatically alter the energy/water nexus y gy
Reclaimed Wastewater inSingapore (NEWater) Source of water supply f l for commercial and industrial sectors (10% of water demand) 4 NEWater p a ts ate plants supplying 50 mgd of NEWater. Will meet 15% of 5 miles water demand by 2011
Reuse of Wastewater in Orange County, County California www.gwrsystem.com Groundwater Replenishment System (70 MG/day))PradoDam Santa Ana River Facilities
GWR System for Advanced Water Purification (Orange County) Microfiltration Reverse Ultraviolet (MF) Osmosis Light with (RO) H2O2 OCSDSecondary WW Recharge Effluent Basins
Windhoek’s Solution: Wastewater Reclamation for Direct Potable UseGoreangab Reclamation Plant (Windhoek) “Water should not be Water judged by its history, but by its quality.” y q y Dr. Lucas Van Vuuren National Institute of Water Research, S th Af i R h South Africa The only wastewater reclamation plant y in the world for direct potable use
The Treatment Scheme: AMultiple Barrier Approach
Most Important: Public Acceptanceand T d Trust i the Q li of W in h Quality f Water Breaking down th psychological b i (th B ki d the h l i l barrier (the “yuck factor”) is not trivial – Ri Rigorous monitoring of water quality after every it i f t lit ft 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
Fouling Resistant UF Membranes: Comb (PAN-g-PEO) Additives amphiphilic copolymer added hi hili l dd d segregate & self-organize t lf i to casting solution at membrane surfaces PEO brush layer on surface and inside pores Casting Doctor Solution Blade Heat Treatment Fouling Casting Solution Coagulation Doctor Blade Heat Treatment Bath Coagulation Bath Bath ResistanceAsatekin, Kang, Elimelech, Mayes, Journal of Membrane Science, 298 (2007) 136-146.
Fouling Reversibility (with Organic Matter) O ) White: Pure water Whit P t 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 2 N/m) 0F/R (mN -2 -4 PAN (P0-0) P50-5 -6 P50-10 P50 20 P50-20 -8Kang, Asatekin, Mayes, Elimelech, Journal of Membrane Science, 296 (2007) 42-50.
Antifouling NF Membranes for MBR (PVDF g POEM) (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 1.4 1.2 malized flux 1.0 0.8 PVDF-g-POEM (●,●) 0.6 Norm 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
MBR and the Sanitation Crisis inDDeveloping C l i Countries ti1.1 billion people ⎯ or onesixth of the world’s population⎯ lack access to safe water2.4 billion are withoutadequate sanitationBetween 2 to 4 million deathsa year are attributed to unsafewater,water mostly due to water water-borne preventable diarrhealdiseases
MBR as a Decentralized SewageTreatment OptionT t t O tiCentralized sewage treatment (wastewater treatmentplants) is not realistic (long-term goal)MBR may be ideal for localized, decentralized sewagetreatment in the developing worldAdvantages: small footprint, flexible design, andautomated operation
Seawater DesalinationAugmenting and diversifying water supplyReverse osmosis and thermal desalination(MSF and MED) are the current desalinationtechnologiesEnergy intensive (cost and environmentalimpact)Reverse osmosis is currently the leadingtechnology
Reverse OsmosisMajor improvements in the past 10 yearsFurther improvements are likely to beincrementalRecovery limited to ~ 50%: Brine discharge ( B i di h (environmental concerns) i t l ) Increased cost of pre-treatmentUse prime (electric) energy (~ 2.5 kWh percubic meter of product water)
Minimum Energy of Desalination Minimum energy needed to desalt water is independent of the technology or mechanism of desalination V 2 1 3.5 35 W= ∫Π dVMinimum Energy (kW-h/m ) V1 − V23 os O 3.0 100 C V1 O 25 C 2.5 25 ( 2.0 Minimum theoretical energy for desalination: 1.5 15 0% recovery: 0.7 kWh/m3 1.0 50% recovery: 1 kWh/m3 0.5 05M 0 20 40 60 80 100 Percent Recovery
Nanotechnology May Result inBreakthrough Technologies“These nanotubes are so beautifulthat they must be useful forsomething. . .”, Richard Smalley(1943-2005).
Aligned Nanotubes as High FluxMembranes for Desalination? Hinds et al, “Aligned multi-walled carbon nanotube membranes”, Science, 303, 2004.
Research on Nanotube BasedMembranes Mauter and Elimelech, Environ. Sci. Technol., 42 (16), 5843-5859, 2008.
Next Generation NanotubeMembranesM b Mauter and Elimelech, 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 Hi h nanotube d t b density and purity it d it Large scale production?
Bio-inspired High FluxMembranes for DesalinationNatural aquaporin proteins extracted from livingorganisms can be incorporated into a lipid bilayermembrane or a synthetic polymer matrix
BUT …. Energy is Needed Even for Membranes with Infinite Permeability Minimum theoretical energy for desalination at gy 50% recovery: 1 kWh/m3 Practical limitations: No less than 1.5 kWh/m3 Achievable goal: g 1.5 − 2 kWh/m3Shannon, Bohn, Elimelech, Georgiadis, and Mayes, Nature 452 (2008) 301-310.
Concluding Remarks gWe are far from the thermodynamic limits yfor separating unwanted species from waterNanotechnology and new materials cansignificantly advance water purificationtechnologiesAdvancing the science of water purification g pcan aid in the development of robust, cost-effective technologies appropriate for g pp pdifferent regions of the world