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Reverse Osmosis Reverse Osmosis Presented by Dick Youmans, CWT David H. Paul, Inc. 2 Outline for this Presentation 1) Define Osmosis and Reverse Osmosis 2) Types of Membranes and Their Characteristics 3) Manufacturing Process for the “Membrane” 4) Demonstration: Rolling One Of Our Own 5) Understand Water Flow Through an Element 6) Understand Water Flow Through Pressure Vessels 3 Definition of Osmosis Osmosis is the process where a solvent (usually water) passes from a dilute solution into a more concentrated one by moving through a semipermeable membrane which selectively allows the passage of the solvent, but restricts the passage of the solute (dissolved solids). 4 Osmosis Time = Zero Equilibrium Time Less Concentrated Pure Concentrated Pure Solution Water Solution Water 5 Osmosis 6 Osmosis Time = Zero Equilibrium Time Less Concentrated Pure Concentrated Pure Solution Water Solution Water 7 Types of Pressures Involved 1) Osmotic Pressure 2) Applied Pressures A) Hydrostatic or Head Pressure B) Pump or External Pressure 3) Net Driving Pressure 8 Osmotic Pressure Time = Zero Equilibrium Time <1000 ppm 1000 Pure ppm TDS TDS Pure Water Water Osmotic Pressure 10 psi 9 Approximate Osmotic Pressures • TDS in ppm • Osmotic Pressure in psi (bar) 100 ppm 1 psi (.069Bar) 1,000 ppm 10 psi (.69 Bar) 5,000 ppm 50 psi (3.45 Bar) 10,000 ppm 100 psi 6.9 Bar) 15,000 ppm 150 psi (10.35 Bar) 10 Net Osmotic Pressure Time = Zero Equilibrium Time 1000 1000 1000 1000 ppm ppm ppm ppm TDS TDS TDS TDS Osmotic Pressure 10 psi 10 psi Net Osmotic Pressure is 0 psi 11 Applied Pressure Time = Zero Equilibrium Time 2.3 feet 2.3 feet 2.3 feet 2.3 feet Pure Water Pure Water Pure Water Pure Water Hydrostatic Pressure No 1 psi Change 1 psi Net Pressure is 0 psi 12 Applied Pressure Time = Zero Equilibrium Time 4.6 feet Pure Water 3.45 feet 3.45 feet 2.3 feet Pure Pure Water Water Pure Water Hydrostatic Pressure Hydrostatic Pressure 1 psi 1.5 psi 2 psi 1.5 psi Net Pressure is 0 psi Net Pressure is 1 psi 13 Osmosis Stopped Time = Zero Equilibrium Time 7 psi 7 psi 1000 300 ppm 1000 ppm 300 ppm ppm 2.3 feet TDS TDS TDS TDS Osmotic Pressure 3 psi 10 psi Applied Pressure 8 psi 1 psi Totals 11 psi 11 psi Net Driving Pressure 0 psi 14 Reverse Osmosis Time = Zero Equilibrium Time 100 psi 1000 300 ppm 2.3 feet ppm TDS TDS Osmotic Pressure 3 psi 10 psi Applied Pressure 101 psi 1 psi Totals 104 psi 11 psi Net Driving Pressure 93 psi 15 Definition of Reverse Osmosis Reverse Osmosis occurs when sufficient external pump pressure is applied to the more concentrated solution to overcome osmotic and hydrostatic pressures to reverse the osmotic reaction causing water to flow from the concentrated solution to the dilute solution. 16 Definition of Net Driving Pressure Reverse Osmosis Unit Feed Water 3 4 Permeate Flow Flow 80 GPM 100 GPM 1 2 Concentrate Flow NDP = Feed Water Pressure (1) + Osmotic 20 GPM Pressure of Permeate (3) - Permeate Back Pressure (4) - Osmotic Pressure of Feed Water (2) 17 Major Types of Membranes Configurations 1) Tubular (inside out) 2) Hollow Fiber (outside in) a) Shell & Tube Heat Exchanger 3) Spiral Wound a) Cellulose Acetate b) Thin Film Polyamide Composite 18 Spiral Wound RO Membrane Element 19 Cellulose Acetate Membranes 1) More Expensive than Thin Film Membranes 2) Typical salt rejection of 96% 3) Typical operating pressures of 400 to 700 PSI 4) Optimum pH operating range of 4.8 to 6.5 5) Good Chlorine Tolerance 20 Thin Film Composite Membranes 1) Less expensive than cellulose acetate membranes 2) Typical salt rejection of 97 to 98% 3) Typical operating pressures of 200 - 300 PSI 4) Wide pH operating range of 2 - 10 5) Very Low Chlorine Tolerance 6) Less susceptible to compaction due to lower PSI 21 Reverse Osmosis Membrane Sheet Components Cellulose Acetate Membrane (Asymmetric) Dense Skin Porous Support Backing Material Thin Film Composite Membrane Semipermeable Membrane Porous Support Backing Material 22 How Do RO Membranes Reject Three Modes of Rejection 1) Ionic Charge 2) Molecular Weight 3) Physical Size 23 Rolling Your Own Reverse Osmosis Membrane Element 24 Materials Needed 25 Fold Membrane in Two With 1/2 Inch Difference. Insert the Permeate Carrier 26 To Simulate Glue Lines, Tape the Edges of the Folded Sheet to Form the Envelope or “ Leaf ”. 27 Tape Permeate Tube to “ Leaf “, Lay Feed Water Spacer on Top and Roll Your Element 28 Continue Rolling Until Finished 29 Pick a Colored Tape and Wrap a Shell Around Your Element 30 Install the Brine Seal & Your Done. 31 Reverse Osmosis Membrane Element 32 Reverse Osmosis Water Flow Definitions Permeate Flow Out Feed Water In Concentrate Flow Out 33 Reverse Osmosis Versus Traditional Filtration 1) Filtration Water Flow in Water Flow out 2) Reverse Osmosis (Cross Flow Filtration) Permeate Flow Out Water Flow In Concentrate Flow Out 34 Does Reverse Osmosis Require Pretreatment? 1) Settling Basins for Silt & Mud 2) Filtration for suspended solids 3) Ion Exchange for Hardness Salts 4) Demineralization for Anions & Cations 5) Activated Carbon Filters for Organics Permeate Quality Required Dictates Pretreatment35 Reverse Osmosis Typical Residential Well Water Installation Well Water Cloth Filter Carbon Filter Drinking Water Reverse Osmosis Concentrate 36 Reverse Osmosis Putting Elements into a Pressure Vessel Pressure Vessel Inter-connectors Permeate Out Element Element Element Element Feed Concentrate Water Brine Out In Seals 37 Reverse Osmosis What is a Pressure Vessel? 38 Reverse Osmosis Putting Elements into a Pressure Vessel Pressure Vessel Inter-connectors Permeate Out Element Element Element Element Feed Concentrate Water Brine Out In Seals 39 Water Flow Through Pressure Vessels Feed Water *Concentrate to Drain* 40 Permeate to Storage Concentrate Waste Disposal in the United States Evaporation Zero Liquid Ponds, 2% Discharge, 0% Spray Irrigation, Deep Well 2% Injection, 9% Discharge to Surface Water Sewer, 42% Discharge, 45% Source: Concentrate Disposal, by Irving Moch, Jr. AMTA’s Pretreatment Solutions, Winter 2006/2007 41 Single Stage Reverse Osmosis Unit (50% Recovery) Permeate 50 GPM Feed 100 GPM Concentrate 50 GPM 42 Two Stage Reverse Osmosis Unit (75% Recovery on a 4 -2 Array) 50 GPM 75 GPM 5 TDS 6.7 TDS 25 GPM 10 TDS 100 GPM 100 TDS 25 GPM 380 TDS 50 GPM 195 TDS 1st Stage 2nd Stage 43 Two Stage Reverse Osmosis Unit (75% Recovery on a 6 - 3 Array) 2nd Stage 1st Stage 44 Two Stage Reverse Osmosis Unit (75% Recovery on a 30 - 15 Array) 2nd Stage 1st Stage 45 Two Pass Reverse Osmosis Unit (25% Recovery ) 50 GPM 25 GPM 5 TDS 0.25 TDS 100 GPM 100 TDS 25 GPM 10 TDS 50 GPM 195 TDS 46 Two Pass Reverse Osmosis Unit 47 Two Pass Reverse Osmosis Units 1) Booster Pump Between Passes 2) Storage Tank Between Passes 3) Caustic Soda Feed Between Passes 48 Two Pass / Two Stage Reverse Osmosis Unit 4 -2 Array 1st Pass / 2 – 1 Array 2nd Pass 1st Pass 2nd Pass 2nd Stage 2nd Stage 1st Stage 1st Stage 49 Hopefully, Time for Questions Thank You, Dick Youmans, CWT 50.
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    8/24/2016 Osmosis ­ AccessScience from McGraw­Hill Education (http://www.accessscience.com/) Osmosis Article by: Johnston, Francis J. Department of Chemistry, University of Georgia, Athens, Georgia. Publication year: 2016 DOI: http://dx.doi.org/10.1036/1097­8542.478400 (http://dx.doi.org/10.1036/1097­8542.478400) Content Osmotic pressure Reverse osmosis Bibliography Additional Readings The transport of solvent through a semipermeable membrane separating two solutions of different solute concentration. The solvent diffuses from the solution that is dilute in solute to the solution that is concentrated. The phenomenon may be observed by immersing in water a tube partially filled with an aqueous sugar solution and closed at the end with parchment. An increase in the level of the liquid in the solution results from a flow of water through the parchment into the solution. The process occurs as a result of a thermodynamic tendency to equalize the sugar concentrations on both sides of the barrier. The parchment permits the passage of water, but hinders that of the sugar, and is said to be semipermeable. Specially treated collodion and cellophane membranes also exhibit this behavior. These membranes are not perfect, and a gradual diffusion of solute molecules into the more dilute solution will occur. Of all artificial membranes, a deposit of cupric ferrocyanide in the pores of a fine­grained porcelain most nearly approaches complete semipermeability. The walls of cells in living organisms permit the passage of water and certain solutes, while preventing the passage of other solutes, usually of relatively high molecular weight. These walls act as selectively permeable membranes, and allow osmosis to occur between the interior of the cell and the surrounding media.
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