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Tony Fane Director Singapore Membrane Technology Centre Nanyang Technological University1 Singapore 639798 Phone: 65-

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Tony Fane Director Singapore Membrane Technology Centre Nanyang Technological University1 Singapore 639798 Phone: 65-

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    2. Et al. Acknowledgements

    3. Special Acknowledgements

    4. Thinking about EPS

    8. Consequences RO Fouling

    9. Membrane Fouling Factors

    10. RO Fouling Roadmap

    11. RO Fouling Roadmap

    15. RO Cake Layer Effects

    16. Basic Theory ~ effect of fouling

    18. Extra TMP required due to RF & CEOP (10 micron cake)

    19. Sodium chloride tracer response technique Measurement of CP (M) and RF

    20. Clean membrane CP (M) vs theory CP by sodium chloride tracer response technique close to theoretical values.

    24. At fixed flux fouling manifests as rise in required TMP. Cause of this rise is hydraulic resistance (RF) and enhanced CP (leading to higher DP ) (CEOP). CEOP contribution can be significant and is measurable (in the lab). RO fouling effect increases (exponentially) with imposed flux, and decreased crossflow.

    25. What is the effect of flux in RO on biofouling?

    26. Growth = f (CW )

    27. Biofouling vs flux Is biofouling flux dependent? Does biofilm present as a ‘resistance’ or an enhanced concentration polarization effect? Controlled flux tests using p.fluorescens and model feed (NaCl + nutrient).

    30. Biofouling has resistance

    31. Biofouling enhances CP*

    32. Biofilm development vs flux

    33. Biofouling (dCp/dt) development vs flux

    34. The role of the spacer

    35. Spacers can also increase particle back-transport

    36. Spacers can also promote localized deposition

    37. Local variations in surface shear are predicted by CFD

    38. Biofouling with spacers

    39. Biofouling with spacers

    40. Biofouling with & without spacers

    41. Biofouling with & without spacers ~ effect of salt background

    42. Biofouling with & without spacers ~ effect of salt background

    44. Biofilm development - The role of the spacer ?

    45. Biofilm development and control

    46. Biofilm development and control

    51. The addition of NO induces dispersal of P. aeruginosa biofilms

    52. NO donors work synergistically with traditional biocides

    53. Nitric oxide reduces biofilms on RO membranes These were biofilms of P. aeruginosa which were added to the RO system. These were biofilms of P. aeruginosa which were added to the RO system.

    54. NO treatment reduces biofilms on RO membranes Preliminary data, based on CFU and staining indicate that NO treatment reduces pre-established biofilms The percentage of biofilm reduction was concentration dependent: 2 mM , 1 mM and 0.5 mM 95 %, 70 % and 25% reduction in CFU counts.

    56. ACKNOWLEDGEMENTS

    57. Materials and Methods Model foulants (i) colloidal silica (20 nm, 200 mg/L), (ii) alginic acid (6 mg/L as TOC), (iii) Pseudomonas fluorescens (ATCC 700830, 105 CFU/mL, 20 mg/L Nutrient Broth) with background salinity of 2000 mg/L NaCl Experimental protocols Equilibrate with Milli-Q water for 12 hours (membrane compaction) Add in NaCl as background ions solution (and add in Nutrient Broth for biofouling studies) and equilibrate for 2 hours Add in model foulants or continuous injection of bacteria solution to initiate fouling process Monitor TMP and membrane autopsy at the end of experiment Test conditions Fixed flux operation No feed spacer used (to accelerate fouling process) Vary flux level, crossflow velocity, feed pressure

    60. Critical flux for Bacteria SW8

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