Forward Osmosis: Progress and Challenges Menachem Elimelech Department of Chemical and Environmental Engineering Yale University New Haven, Connecticut 2014 Clarke Prize Conference, November 7, 2014, Huntington Beach, California
Reverse Osmosis (RO) Water flux, J w 0 J Water Flux Eqn: w A P m Permeate RO (P > ) water water M E M B R A N E Feed Hydraulic Pressure P
Forward Osmosis (FO) Water flux, J w 0 Water Flux Eqn: J w A m FO (P = 0) Feed M E M B R A N E Permeate water Draw Solution water P
Pressure Retarded Osmosis (PRO) Water flux, J w J w 0 Water Flux: A m Flux reversal point (P = ) P PRO (P < ) Feed M E M B R A N E Permeate Pressurized Draw Solution water water P
Engineered Osmosis FO (P = 0) Water flux, J w 0 Flux reversal point (P = ) PRO (P < ) RO (P > ) P
Overview of Presentation Energy Aspects of Forward Osmosis Fouling Propensity and Reversibility in Forward Osmosis Desired Membrane Properties and Reverse Solute Flux Applications of Forward Osmosis
The Forward Osmosis Process Feed Water Membrane Diluted Draw Solution Draw Solution Recovery Process Energy Input Concentrate Concentrated Draw Solution Product water
Energy Input in FO: No Free Lunch. Can t beat thermodynamics Separation energy of draw solution is proportional to the osmotic pressure of draw solution Input energy > energy equivalent to draw solution osmotic pressure Potential innovations through use of low-cost forms of energy (e.g., low-grade heat), rather than prime (electric) energy
RO Energy Consumption Brine Permeate SE: Specific energy ΔP: Applied pressure π Β (R): Brine osmotic pressure at recovery R SE = ΔP π Β (R) Shaffer et al. (2014), in press, 10.1016/j.desal.2014.10.031.
Comparing Energy of RO and FO-RO SE min = π Β π D is always > π Β SE min = π D Brine Permeate Draw
FO-RO Always Requires More Energy than RO Alone SE min (FO-RO) = π D > π Β = SE min (RO) Condition for net driving force in FO
Overview of Presentation Energy Aspects of Forward Osmosis Fouling Propensity and Reversibility in Forward Osmosis Desired Membrane Properties and Reverse Solute Flux Applications of Forward Osmosis
Organic Fouling Reversibility in Forward Osmosis Flux (m/s) 10 8 6 4 2 Flux of clean membrane Fouling Cleaning Flux after cleaning 36 29 22 14 0 0 0 500 1000 1500 2000 Time (min) 7 Flux (l/m 2 /h) FO membrane: CA (Hydration Tech) Organic foulant (200 mg/l alginate); 50 mm NaCl; 0.5 mm Ca 2+ Cleaning: 50 mm NaCl, increased crossflow, 15 min Mi and Elimelech, Journal of Membrane Science, 348 (2010) 337 345.
FO Exhibits Fouling Reversibility with a Wide Range of Foulants 1.0 Flux recovery by rinsing Flux after fouling Normalized Flux Shaffer et al. (2014), in press, 10.1016/j.desal.2014.10.031. 0.8 0.6 0.4 0.2 0.0 Alginate BSA Gypsum Silica Foulant Type
In Situ Surface Modification for Fouling Resistance PEG PEG MPD+TMC O C Cl O C O Cl C Cl NH 2 -PEG O C NH O C NH Interfacial Polymerization PEGylation Polysulfone Support Layer Nascent Polyamide Layer In Situ Modified Membrane Lu et al. Environ. Sci. Technol. 2013, 47, 12219 12228. Contact Angle ( ) 120 100 80 60 40 20 0 Control Control In Situ Modified In Situ Modified
Modified Membrane Exhibits Organic Fouling Resistance Normalized water flux, J w /J w,0 (%) 100 95 90 85 80 Control Polyamide In Situ Modified 0 100 200 300 400 500 Cumulative Permeate Volume (ml) Normalized Water Flux, J w /J w,0 (%) 100 95 90 85 80 Fouling Control Cleaning In Situ Modifed Lu et al. Environ. Sci. Technol. 2013, 47, 12219 12228
Overview of Presentation Energy Aspects of Forward Osmosis Fouling Propensity and Reversibility in Forward Osmosis Desired Membrane Properties and Reverse Solute Flux Applications of Forward Osmosis
Current Focus: Reducing Structural Parameter of Membranes K t s D Membrane structural parameter, S Tortuosity, Thickness, t s Porosity, K Solute resistance to diffusion t s Support layer thickness Tortuosity support layer Porosity thin film (active layer) D Draw solute diffusivity
Significant Progress in the Past 10 Years TFC-RO TFC-FO S = 9583 μm S = 390 μm Yip et al. Environ. Sci. Technol. 2010, 44, 3812 3818
Low Structural Parameter is Critical for Obtaining High Water Flux Shaffer et al. (2014), in press, 10.1016/j.desal.2014.10.031.
Challenge: Minimize Reverse Draw Solute Flux Feed Water Membrane Diluted Draw Solution J s Draw Solution Recovery Process Concentrate Concentrated Draw Solution Product water
The Driving Force for Reverse Draw Solute Permeation A highly concentrated draw solution generates the osmotic gradient that drives the flux of water J w J w A m J s The high concentration of draw solute also drives the reverse permeation of draw solute. n J s f cm Feed Draw
Analytical Expression for Reverse Solute Flux J s J ws J w cd, b exp cf, b exp D k A B J w J ws 1 exp exp J w k D J w J ws J w D, b exp F, b exp D k A B J w J ws 1 exp exp J w k D
Model Predicts Reverse Solute Flux for Salt and Neutral Solutes Predicted Solute Flux (mol m -2 h -1 ) 100 10 1 0.1 0.01 Urea Ethylene Glycol Glucose NaCl 0.01 0.1 1 10 100 Experimental Solute Flux (mol m -2 h -1 ) 60.1 g/mol 62.1 g/mol 0.72 nm 180.2 g/mol Yong et al., Journal of Membrane Science 392 393 (2012) 9 17
Reverse Flux Selectivity (RFS): An Important Design Parameter Defined as ratio of forward water flux to reverse salt flux Representative of the volume of water produced per moles (or mass) of solute lost Depends solely on the membrane active layer permeability and selectivity J J w s A B nr g T
Membranes Are Constrained by the Permeability-Selectivity Tradeoff J J w s A B nr g T Goal: Maximize B A Yip et al. Environ. Sci. Technol. 2011, 45, 10273 10282 Geise et al., Journal of Membrane Science 2011, 369 (1-2), 130-138.
Overview of Presentation Energy Aspects of Forward Osmosis Fouling Propensity and Reversibility in Forward Osmosis Desired Membrane Properties and Reverse Solute Flux Applications of Forward Osmosis
The Goal of FO is NOT to Replace RO! RO is the Gold Standard for Desalination FO can be used in Applications where RO cannot
Potential Applications of FO High salinity feed waters that cannot be treated by RO (RO limited to feed water up to about 40,000 ppm) Very difficult to treat feed waters (i.e., feed waters with very high fouling potential) Zero liquid discharge (ZLD) Pre-treatment to improve the performance of conventional desalination processes
Applications in Oil and Gas Gregory et al., Elements, Vol. 7, 2011, 181 186
Applications in Oil and Gas: Very Hard to Treat Shale Gas Waters Upper Limit Conc. (mg/l) Gregory et al., Elements, Vol. 7, 2011, 181 186 TDS: 260,000 Hardness: 55,000 Alkalinity: 1,100 Calcium: 31,000 Cannot be treated by pressure-driven membrane processes (RO/NF)
The Green Machine : Treatment of Water from Hydraulic Fracturing Source: Hydration Technologies Innovation (HTI)
FO Desalination with Thermolytic Draw Solutions Nature, 452, (2008) 260 Low-Grade Heat McCutcheon et al., Desalination, 174 (2005) 1-11.
Brine Concentrator for Treatment of High Salinity Shale Gas Wastewater TDS = 75,000 mg/l Oasys Water Inc. Desalination 312 (2013) 67 74 TDS = 300 mg/l
FO in ZLD Schemes as Brine Concentrator Shaffer et al. (2014), in press, 10.1016/j.desal.2014.10.031.
Pre-treatment for Conventional Desalination Technologies Shaffer et al. (2014), in press, 10.1016/j.desal.2014.10.031.
The Promise Concluding Remarks Low fouling propensity Can treat high salinity brines Can treat challenging wastewaters Can be integrated with established technologies (e.g. RO) and zero liquid discharge (ZLD) schemes The Challenges Development of low-cost high performance membranes Minimizing reverse draw solute flux More pilot demonstrations Development of full-scale systems
Acknowledgments Current and former research group at Yale Collaborations: Korea University (Prof. S. Hong), Wollongong University (Prof. Long Nghiem Funding: National Science Foundation, Office of Naval Research, Department of Energy, US EPA, Cornell- KAUST