Reverse Osmosis. Presented by Dick Youmans, CWT David H. Paul, Inc.

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2 Reverse Osmosis Presented by Dick Youmans, CWT David H. Paul, Inc. 2

3 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

4 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

5 Osmosis Time = Zero Equilibrium Time Less Concentrated Solution Pure Water Concentrated Solution Pure Water 5

6 Osmosis 6

7 Osmosis Time = Zero Equilibrium Time Less Concentrated Solution Pure Water Concentrated Solution Pure Water 7

8 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

9 Time = Zero Osmotic Pressure Equilibrium Time 1000 ppm TDS Pure Water <1000 ppm TDS Pure Water Osmotic Pressure 10 psi 9

10 Approximate Osmotic Pressures TDS in ppm Osmotic Pressure in psi (bar) 100 ppm 1,000 ppm 5,000 ppm 10,000 ppm 15,000 ppm 1 psi (.069Bar) 10 psi (.69 Bar) 50 psi (3.45 Bar) 100 psi 6.9 Bar) 150 psi (10.35 Bar) 10

11 Net Osmotic Pressure Time = Zero Equilibrium Time 1000 ppm TDS 1000 ppm TDS 1000 ppm TDS 1000 ppm TDS Osmotic Pressure 10 psi 10 psi Net Osmotic Pressure is 0 psi 11

12 Time = Zero Applied Pressure Equilibrium Time 2.3 feet 2.3 feet 2.3 feet 2.3 feet Pure Water Pure Water Pure Water Pure Water Hydrostatic Pressure 1 psi No Change 1 psi Net Pressure is 0 psi 12

13 Time = Zero Applied Pressure Equilibrium Time 4.6 feet Pure Water 2.3 feet Pure Water 3.45 feet Pure Water 3.45 feet Pure Water Hydrostatic Pressure 1 psi 2 psi Net Pressure is 1 psi Hydrostatic Pressure 1.5 psi 1.5 psi Net Pressure is 0 psi 13

14 Osmosis Stopped Time = Zero Equilibrium Time 7 psi 7 psi 1000 ppm TDS 300 ppm TDS 2.3 feet 1000 ppm TDS 300 ppm TDS Osmotic Pressure 3 psi 10 psi Applied Pressure 8 psi 1 psi Totals 11 psi 11 psi Net Driving Pressure 0 psi 14

15 Time = Zero Equilibrium Time 100 psi Reverse Osmosis 1000 ppm TDS 300 ppm TDS 2.3 feet Osmotic Pressure 3 psi 10 psi Applied Pressure 101 psi 1 psi Totals 104 psi 11 psi Net Driving Pressure 93 psi 15

16 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

17 Definition of Net Driving Pressure Feed Water Flow 100 GPM Reverse Osmosis Unit Permeate Flow 80 GPM Concentrate Flow NDP = Feed Water Pressure (1) + Osmotic Pressure of Permeate (3) - Permeate Back Pressure (4) - Osmotic Pressure of Feed Water (2) 20 GPM 17

18 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

19 Spiral Wound RO Membrane Element 19

20 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

21 Thin Film Composite Membranes 1) Less expensive than cellulose acetate membranes 2) Typical salt rejection of 97 to 98% 3) Typical operating pressures of PSI 4) Wide ph operating range of ) Very Low Chlorine Tolerance 6) Less susceptible to compaction due to lower PSI 21

22 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

23 How Do RO Membranes Reject Three Modes of Rejection 1) Ionic Charge 2) Molecular Weight 3) Physical Size 23

24 Rolling Your Own Reverse Osmosis Membrane Element 24

25 Materials Needed 25

26 Fold Membrane in Two With 1/2 Inch Difference. Insert the Permeate Carrier 26

27 To Simulate Glue Lines, Tape the Edges of the Folded Sheet to Form the Envelope or Leaf. 27

28 Tape Permeate Tube to Leaf, Lay Feed Water Spacer on Top and Roll Your Element 28

29 Continue Rolling Until Finished 29

30 Pick a Colored Tape and Wrap a Shell Around Your Element 30

31 Install the Brine Seal & Your Done. 31

32 Reverse Osmosis Membrane Element 32

33 Reverse Osmosis Water Flow Definitions Feed Water In Permeate Flow Out Concentrate Flow Out 33

34 Reverse Osmosis Versus Traditional Filtration 1) Filtration Water Flow in Water Flow out 2) Reverse Osmosis (Cross Flow Filtration) Water Flow In Permeate Flow Out Concentrate Flow Out 34

35 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 Pretreatment 35

36 Reverse Osmosis Typical Residential Well Water Installation Well Water Cloth Filter Carbon Filter Reverse Osmosis Drinking Water Concentrate 36

37 Reverse Osmosis Putting Elements into a Pressure Vessel Pressure Vessel Inter-connectors Permeate Out Element Element Element Element Feed Water In Brine Seals Concentrate Out 37

38 Reverse Osmosis What is a Pressure Vessel? 38

39 Reverse Osmosis Putting Elements into a Pressure Vessel Pressure Vessel Inter-connectors Permeate Out Element Element Element Element Feed Water In Brine Seals Concentrate Out 39

40 Water Flow Through Pressure Vessels Feed Water *Concentrate to Drain* Permeate to Storage 40

41 Concentrate Waste Disposal in the United States Spray Irrigation, 2% Evaporation Ponds, 2% Zero Liquid Discharge, 0% Deep Well Injection, 9% Discharge to Sewer, 42% Surface Water Discharge, 45% Source: Concentrate Disposal, by Irving Moch, Jr. AMTA s Pretreatment Solutions, Winter 2006/

42 Single Stage Reverse Osmosis Unit (50% Recovery) Permeate 50 GPM Feed 100 GPM Concentrate 50 GPM 42

43 Two Stage Reverse Osmosis Unit (75% Recovery on a 4-2 Array) 50 GPM 5 TDS 75 GPM 6.7 TDS 25 GPM 10 TDS 100 GPM 100 TDS 25 GPM 50 GPM 380 TDS 1st Stage 195 TDS 2nd Stage 43

44 Two Stage Reverse Osmosis Unit (75% Recovery on a 6-3 Array) 2 nd Stage 1 st Stage 44

45 Two Stage Reverse Osmosis Unit (75% Recovery on a Array) 2 nd Stage 1 st Stage 45

46 Two Pass Reverse Osmosis Unit (25% Recovery ) 50 GPM 5 TDS 25 GPM 0.25 TDS 100 GPM 100 TDS 25 GPM 10 TDS 50 GPM 195 TDS 46

47 Two Pass Reverse Osmosis Unit 47

48 Two Pass Reverse Osmosis Units 1) Booster Pump Between Passes 2) Storage Tank Between Passes 3) Caustic Soda Feed Between Passes 48

49 Two Pass / Two Stage Reverse Osmosis Unit 4-2 Array 1 st Pass / 2 1 Array 2 nd Pass 1 st Pass 2 nd Pass 2 nd Stage 2 nd Stage 1 st Stage 1 st Stage 49

50 Hopefully, Time for Questions Thank You, Dick Youmans, CWT 50