Membrane technology
82 likes22,090 views
This document discusses membrane filtration technology. It covers topics such as membrane classification based on pore size and pressure range, common membrane processes like microfiltration and reverse osmosis, factors that affect membrane performance like fouling, and advantages of membrane filtration over conventional processes like sand filtration. The document also describes strategies to mitigate fouling, such as pretreatment, operation techniques like crossflow filtration, and chemical cleaning methods. Maintaining membrane integrity is also addressed.
![Potential Fouling Material
Inorganic Material
• Precipitation of Ca, Mn, Mg, Fe, and Al could cause
significant fouling
• Fine inorganic colloids (< 0.05 µm) could clog
membrane pores and cause fouling
• Prefer a negative Langelier Index
• Acid, EDTA, SBS cleaning could be effective for
inorganic fouling
Langelier Index = Actual pH – Saturation pH
Saturation pH = 2.18 - log[Ca+2] - log[HCO3-]
L.I. > 0 : Oversaturated (tend to precipitate)
L.I. < 0 : Undersaturated (tend to dissolve more)](https://image.slidesharecdn.com/membranetechnology-110926021757-phpapp02/85/Membrane-technology-44-320.jpg)
Membrane technology
- 1. MEMBRANE TECHNOLOGY Paulus Hartanto
- 6. Application of membrane processes in water environment
- 7. Factors affecting membrane performance
- 8. What is membrane ?
- 9. Conventional vs Membrane Filtration
- 10. Classification of membrane processes
- 11. Phases divided by membrane
- 12. Some membrane processes and driving forces
- 13. More common membrane processes
- 14. Flux range & trans-membrane pressure in pressure driven membrane
- 15. Membrane distillation vs Osmotic distillation
- 16. Historical development of membranes
- 17. Classification of filter (membrane)
- 18. Depth filter vs screen filter
- 19. Depth filter
- 20. Screen filter
- 21. Advantages of screen filter
- 22. Absolute vs Nominal rating
- 24. Membrane classification (poresize) Organic macromolecules Colloids Organic compounds Bacteria Viruses Dissolved salts Pollens Yeasts 100 µm 10 µm 1 µm 0.1 µm 0.01 µm 0. 1 nm 0. 1 nm RO Red hair visible to globule Smallest Polio microorganisms virus NF naked eye UF Nanofiltration MF Ultrafiltration Microfiltration
- 25. Membrane classification (pressure range)
- 26. Rejection Capabilities UF vs MF
- 28. Membrane classification (driving force) • Vacuum (Submerged Membranes) – Compatible with higher solid concentration – Can be used for retrofit – High energy demand with air scouring – Noise & evaporation concerns
- 29. Membrane classification (driving force) • Pressure (Canister Membranes) – More compact design – Cannot handle high solid concentration (> 100 NTU) for a substantial period of time
- 30. Membrane classification (configuration) • Open feed channel configuration : Tubular Hollow-Fiber • Narrow feed channel configuration Spiral (Flat sheet)
- 31. Membrane classification (configuration) • Flat Sheet (Spiral-wound) Mostly used in Reverse Osmosis & Nanofiltration
- 32. Membrane classification (configuration) • Tubular Membranes (OD > 3 mm) Mostly used in Industrial MF
- 33. Membrane classification (configuration) • Hollow Fiber Membranes (ID < 1.5 mm) Mostly used in MF & UF
- 34. Membrane classification (Location of membrane) • Inside-out Membranes Raw Water Filtered Water • Outside-In Membranes
- 35. Membranes Applications • Filtration: Low-Pressure membranes (MF/UF) for turbidity & pathogen removal • Organic Removal: Nanofiltration (NF) for NOM removal • Inland Brackish Desalination: RO or NF • Seawater Desalination: RO or 2-stage NF • Membrane Bioreactor: MF/UF MBR
- 36. Membrane vs Sand • Membrane filtration mechanism – Sieving/Straining • Sand filtration mechanism – Interception, collision, electrostatic attraction – Straining only happens in cake filtration
- 37. Finished water comparison Conventional Membranes Turbidity 0.05 ~ 0.3 < 0.1 Virus removal 2 log > 4 log Influent quality change Affected Not affected Water chemistry Affected Not affected change Operating conditions Affected Not affected change
- 38. Performance comparison Conventional Membranes High feed turbidity Shorter run time Higher pressure (if turbidity is excessive for a long duration) High feed TOC Not affected Higher pressure, need freq. chemical cleaning High FeCl3 dose Shorter run time FeCl3 not required Low feed temp. Not affected Higher pressure or lower output Capacity increase Shorter run time Higher pressure, need freq. chemical cleaning
- 39. Typical Membrane Filtration Cycle • Filtration (15 ~ 50 minutes) • Backwash (20 sec ~ 2 min) (No rinsing, surface wash, or filter-to-waste) Special Operation/Maintenance • Chemical Cleaning • Membrane Repair
- 41. Fouling is part of membranes • All membranes are subject to fouling, no exception • Fouling is acceptable as long as it is reversible and manageable (i.e., can be removed in a reasonable fashion)
- 42. Potential Fouling Material Natural Organic Matter • NOM with high SUVA • TOC > 4 mg/L would be a concern • Organic fouling is “sticky” and difficult to clean • Organic may serve as “cement” to bind other particulates and form a strong cake layer • Caustic cleaning (e.g. NaOH) and strong oxidant (e.g. H2O2) are effective for NOM fouling cleaning
- 43. Potential Fouling Material Particulate/Colloids • Inorganic particles alone would not cause much fouling • Inorganic particle cake layer could be easily removed by backwash • Excessive turbidity could clog membrane fiber lumens • Inorganic particles mixed with NOM could cause substantial fouling • Organic colloids could cause significant fouling and could be difficult to clean
- 44. Potential Fouling Material Inorganic Material • Precipitation of Ca, Mn, Mg, Fe, and Al could cause significant fouling • Fine inorganic colloids (< 0.05 µm) could clog membrane pores and cause fouling • Prefer a negative Langelier Index • Acid, EDTA, SBS cleaning could be effective for inorganic fouling Langelier Index = Actual pH – Saturation pH Saturation pH = 2.18 - log[Ca+2] - log[HCO3-] L.I. > 0 : Oversaturated (tend to precipitate) L.I. < 0 : Undersaturated (tend to dissolve more)
- 45. Potential Fouling Material Synthetic Polymers • Polymers used for coagulant/filter aids & backwash water treatment • Presence of polymers in feed water could cause dramatic fouling, and sometimes irreversible • Free residual polymer is worse than particle- associated polymer • Cationic polymers are worst • Some polymers can be easily cleaned with chlorine and therefore are consider compatible with membranes
- 46. Fouling Mitigation Pretreatment • Reduce TOC level (< 4 mg/L) • Reduce Turbidity (< 5 NTU) • Reduce Hardness (< 150 mg/L) • Avoid substantial change in water chemistry, such as pH and other pretreatment chemicals • Prevent Oil and Polymers from entering the feed water
- 47. Fouling Mitigation Operation • Use crossflow if turbidity is high (For Inside- out membranes) • Bleed a portion of the concentrate to avoid solid buildup • Operate at a lower flux (lower TMP) • Enhance pretreatment
- 48. Fouling Mitigation Cleaning Strategy 1. Frequent BW (shorter filtration cycle) 2. Longer BW duration 3. Higher BW pressure 4. Add cleaning chemicals in BW water 5. Frequent chemical cleaning
- 49. Membrane Cleaning Membrane Fouling Mechanisms • Organic & Inorganic • Particulate & Soluble • Various Mechanisms – Surface & Pore – Adsorption, precipitation, coagulation
- 50. Membrane Cleaning • Hydraulic Cleaning (10~30 minutes) – Water/Air Backwash – Air Scouring – Water Flushing • Chemical Cleaning (1~8 weeks) – Free Chlorine (Sodium Hypochlorite) – Acid/Base – Other strong oxidants, such as H2O2 – Reducing agent, such as SBS – Chelating chemicals, such as EDTA – Proprietary Chemicals (surfactants)
- 51. Summary of Fouling Material & Cleaning Chemicals Cleaning Chemical For Fouling Material NaOCl Biological; NOM; Synthetic polymers Acids (HCl, H2SO4, Citric Acid) Inorganic deposits NaOH NOM Sodium bi-sulfite (SBS) Reducible metals (Fe, Mn) H2O2 NOM EDTA Metals
- 52. Membrane Integrity Membrane failure is rarely catastrophic – less serious than microbial penetration of rapid sand filter beds. Membrane Integrity • Membranes fail incrementally – one fiber at a time. • Statistically, individual fiber breaks are insignificant to the overall microbial water quality.
- 53. Membrane Integrity Monitoring • On-Line Turbidity Monitoring – 0.08 NTU 95% of the time, 0.1 NTU max. • On-Line Particle Count – Baseline establishment (< 50 particles/mL) – Sensitivity: Number of fiber breakage? • Pressure Holding Test • Virus Seeding Test (UF)
- 54. The Secret of Membranes… Fouling Index Cleaning High Production Water Quality High Recovery • Finding the balance point between Fouling-Enhancers and Fouling Reducers is the KEY!
- 55. Take Away Points • Membranes Offers a Wide Range of Applications • Membrane is a Mature Technology • A Successful Membrane Operation Depends on – The Selection of an Appropriate System – Optimized Operating Conditions/Protocols that Yield Manageable Membrane Fouling – Experience Design Engineer
- 56. The End