Introduction to Membrane Technology and applications
- 1. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
- 2. 2 Introduction to Membranes •Low pressure membranes •Ultrafiltration •Microfiltration •High pressure membranes •Nanofiltration •Reverse osmosis •Membrane fouling •Mineral scaling •Biofilm formation
- 3. 3 Plate and frame membrane module
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- 6. 6 Cross-flow membrane operation Spiral wound membrane module Hollow fiber membrane module Dead-end membrane operation feed permeate Typical membrane module construction: Three configurations: hollow fiber-spiral wound and plate and frame
- 7. 7 Low pressure: porous membranes microfiltration, ultrafiltration Photos courtesy of the American Membrane Technology Association Low Pressure Membranes can be Backflushed - Mean pore size ~ size rating of filter (.01 -10 micron)
- 8. 8 Two flow regimes in hollow fibre MF •inside-out: – water flows through a concentric channel or lumen – allows good control over module hydrodynamics •outside-in: – more difficult to control flow channeling and/or dead-end zones – more difficult to flush the particles from the module when backwashing – usually lower head loss through the module Hollow fiber technology
- 10. 10 Lumen Permeate Feed UF and MF membranes can be “inside-out” or “outside in” Skin
- 12. 12 Source : European Conference on Desalination and the Environment: Water Shortage Lemesos (Limassol), Cyprus, May 28-31, 2001 Zeeweed hollow fiber reinforced membrane for ultrafiltration Ultrafiltration- outside in
- 13. 13 Koch Membrane Systems hollow fiber reinforced membrane Ultrafiltration- inside out
- 14. 14 Ultrafiltration - inside out and outside in •Typical operating pressures – Pressurized systems: 20 to 30 psi – Submerged systems: 10 to 12 psi •If run at the same flux and backwash interval. – pressurized system operated up to 22 psi – Submerged system operated up to 12 psi – Pressurized and submerged systems performance nearly identical if operating at a sound flux. – Results in similar cleaning intervals – Test has been repeated many times
- 15. 15 Pall Aria •Test effectiveness of Pall Aria system for pretreating Mediterranean seawater prior to reverse osmosis •Long-term pilot testing at three locations •Compare outcomes with – no pretreatment – pretreatment using coagulation with ferric chloride (FeCl3) – enhanced flux maintenance (EFM) protocol with or without pretreatment MF and UF- inside out
- 16. 16 Source: Perry’s Chemical Engineers Handbook
- 17. 17 Source : DOW Water Solutions - http://www.dow.com/liquidseps/prod/mfs2.htm
- 18. 18 Assymetric membranes can be made nonporous (RO) or porous (MF/UF) Active ‘skin’ More porous flux 300 microns These membranes are not composites, but are cast with a skin and a more porous region. Often made by polymer phase inversion.
- 19. 19 Non-porous membranes: nanofiltration, reverse osmosis-thin film composite Thin (100 - 200 nm) polyamide membran Porous support (polysulfone uf membrane Woven mechanical support Surface morphology - thin, dense polymer coating on porous support (composites)
- 20. 20 Tampa Bay Water - 25 mgd saline feed pre- treatment high pressure pump post- treatment fresh water concentrate disposal • energy use (pump) ~ 10 – 50 kJ kg-1 • concentration dependent • energy recovery essential for seawater RO • membranes susceptible to fouling; pre-treatment required • polyamide membranes degraded by Cl2 dense polyamide membrane porous polymer mechanical support Thin film composite membrane polyamide O NH O NH N H2 O
- 22. 22 http://www.ionics.com/technologies/ro/index.htm# Typical RO installation: multiple spiral wound modules in series
- 23. 23 Configuration and staging of membranes
- 24. 24 RO plants consist of membrane banks Manufacturers: Dow- Koch-Toray-Hydranautics
- 25. 25 distance Permeate flux Concentration Osmotic pressure HP water in Concentrate out Permeate out fouling occurs here scaling occurs here Fouling is location dependent
- 26. 26 Mineral scale formation and biofouling reduce permeate flux Source: UCLA Source: Montana State University
- 27. 27 Antiscalant technology slows crystal growth A. J. Karabelas MEDRC Research Report 98-BS-034 SEM micrographs of calcite precipitates 5 mg/L of a phosphonate inhibitor No inhibitor •Phosphonate (HEDP) •Polyanion polymers •Dendrimers O H P O O H O H P OH O H O CH3
- 28. 28 • Caustic Soda NaOH Ca+2 + HCO3 - + NaOH CaCO3 ↓ + Na+ + H2O • Lime Ca(OH)2 Ca+2 + 2HCO3 - + Ca(OH)2 2 CaCO3 ↓ + H2O • Soda Na2CO3 Ca+2 + HCO3 - + Na2CO3 CaCO3 ↓ + HCO3 - + 2Na+ Water softening reduces membrane scaling and increase recovery (recycle operation)
- 29. 29 • Remove cations (Ca, Mg, Fe, Ba) • Reduce nucleating sites for silica, while passing SiO2 • Structure and charge of the components in solution affect NF High rate nanofiltration softening Ca, Mg, SO4 Na, Cl NF softening Enhanced RO H2O
- 30. 30 1. Inorganic/organic colloidal and suspended particles 2. Inorganic scaling (CaCO3, CaSO4, SiO2) 3. Biofouling Biofouling is the largest challenge for high pressure membranes
- 31. 31 Hydrodynamics and biofilm attachment Attachment and adhesion dependent on shear forces at membrane surface: Shear forces and membrane module construction: membrane organic adsorption bacteria attachment and biofilm growth cross flow Fc permeate Fp Flux ratio: R = Fc/Fp High R: high shear force, low normal force suppressed bacteria attachment; low product recovery Low R: low shear force, high normal force high bacteria attachment, biofilm growth; high product recovery membrane membrane spacer • what is shear force at membrane surface? • how does spacer design affect flow, shear forces? • what is optimum spacer design? Needs: • modeling of fluid flow, shear forces • surfaces resistant to organic adsorption • sensors for organic and bio content • measurement of fouling potential • biofilm prevention/remediation Courtesy: Tom Mayer Sandia National laboratories
- 32. 32 •Reverse osmosis membranes suffer from fouling by biofilms •Disinfection with oxidizing agents can destroy the TFC polyamide membranes •New Research is aimed at making a chlorine tolerant RO membrane
- 33. 33 dense polyamide membrane porous polymer mechanical support Thin film composite membrane Journal of Membrane Science, Volume 300, Issues 1-2, 15 August 2007, Pages 165-171 Membrane degradation proceeds by chlorination of the amide followed by ring chlorination
- 34. 34 Angew. Chem. 2008, 120, 6108 –6113 Chlorine tolerant membranes are being studied A new polymer formulation holds promise as a chlorine tolerant RO membrane
- 35. 35 Membrane form Polymer Membrane pore (Å) Separation mechanism Back flushable Chlorine tolerant Use MF Hollow fiber PES/PVDF/ PP 800-5000 MW size yes yes Turbidity- pathogens UF Hollow fiber PES/PVDF/ PP 50-1100 MW size yes yes NOM- pathogens- colloids NF Spiral wound TFC-PA 10-60 MW surface charge no no Softening-NOM removal- desalination RO Spiral wound TFC-PA 1-10 MW surface charge no no Desalination PES-Polyether sulfone, PVDF-Polyvinylidene Fluoride, PP- Polypropylene, TFC-PA – Thin film composite with polyamide skin. (Some older RO membranes are composed of cellulose triacetate)
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