Membrane technology

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A compilation about membrane technology

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Membrane technology

  1. 1. MEMBRANE TECHNOLOGY Paulus Hartanto
  2. 2. Membrane Filtration Technology
  3. 3. Filtration Spectrum
  4. 4. Cross Flow Filtration
  5. 5. Dead End Filtration
  6. 6. Application of membrane processes inwater environment
  7. 7. Factors affecting membrane performance
  8. 8. What is membrane ?
  9. 9. Conventional vs Membrane Filtration
  10. 10. Classification of membrane processes
  11. 11. Phases divided by membrane
  12. 12. Some membrane processes and drivingforces
  13. 13. More common membrane processes
  14. 14. Flux range & trans-membrane pressure inpressure driven membrane
  15. 15. Membrane distillation vs Osmotic distillation
  16. 16. Historical development of membranes
  17. 17. Classification of filter (membrane)
  18. 18. Depth filter vs screen filter
  19. 19. Depth filter
  20. 20. Screen filter
  21. 21. Advantages of screen filter
  22. 22. Absolute vs Nominal rating
  23. 23. Microporous vs Asymmetric
  24. 24. Membrane classification (poresize) Organic macromolecules Colloids Organic compounds Bacteria Viruses Dissolved saltsPollens Yeasts100 µm 10 µm 1 µm 0.1 µm 0.01 µm 0. 1 nm 0. 1 nm RO Redhair visible to globule Smallest Polio microorganisms virus NF naked eye UF Nanofiltration MF Ultrafiltration Microfiltration
  25. 25. Membrane classification (pressure range)
  26. 26. Rejection Capabilities UF vs MF
  27. 27. Process combinations
  28. 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. 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. 30. Membrane classification (configuration)• Open feed channel configuration : Tubular Hollow-Fiber• Narrow feed channel configuration Spiral (Flat sheet)
  31. 31. Membrane classification (configuration)• Flat Sheet (Spiral-wound) Mostly used in Reverse Osmosis & Nanofiltration
  32. 32. Membrane classification (configuration) • Tubular Membranes (OD > 3 mm) Mostly used in Industrial MF
  33. 33. Membrane classification (configuration) • Hollow Fiber Membranes (ID < 1.5 mm) Mostly used in MF & UF
  34. 34. Membrane classification(Location of membrane)• Inside-out Membranes Raw Water Filtered Water• Outside-In Membranes
  35. 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. 36. Membrane vs Sand • Membrane filtration mechanism – Sieving/Straining • Sand filtration mechanism – Interception, collision, electrostatic attraction – Straining only happens in cake filtration
  37. 37. Finished water comparison Conventional MembranesTurbidity 0.05 ~ 0.3 < 0.1Virus removal 2 log > 4 logInfluent quality change Affected Not affectedWater chemistry Affected Not affectedchangeOperating conditions Affected Not affectedchange
  38. 38. Performance comparison Conventional MembranesHigh 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 cleaningHigh FeCl3 dose Shorter run time FeCl3 not requiredLow feed temp. Not affected Higher pressure or lower outputCapacity increase Shorter run time Higher pressure, need freq. chemical cleaning
  39. 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
  40. 40. Membrane Fouling (performance)
  41. 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. 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. 43. Potential Fouling MaterialParticulate/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. 44. Potential Fouling MaterialInorganic 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. 45. Potential Fouling MaterialSynthetic 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. 46. Fouling MitigationPretreatment • 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. 47. Fouling MitigationOperation • 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. 48. Fouling MitigationCleaning 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. 49. Membrane CleaningMembrane Fouling Mechanisms • Organic & Inorganic • Particulate & Soluble • Various Mechanisms – Surface & Pore – Adsorption, precipitation, coagulation
  50. 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. 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. 52. Membrane IntegrityMembrane failure is rarely catastrophic – less seriousthan 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. 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. 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. 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. 56. The End

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