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Design of Ultrafiltration plants for safe drinking water Frans Knops Mark Steggink Irene Körbl

Design of Ultrafiltration plants for safe drinking water Frans Knops Mark Steggink Irene Körbl. Contents. Introduction Ultrafiltration Designing an UF system Components of an UF plant Membrane fouling and cleaning Testing and validating for drinking water New developments

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Design of Ultrafiltration plants for safe drinking water Frans Knops Mark Steggink Irene Körbl

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  1. Design of Ultrafiltration plants for safe drinking waterFrans KnopsMark StegginkIrene Körbl

  2. Contents • Introduction • Ultrafiltration • Designing an UF system • Components of an UF plant • Membrane fouling and cleaning • Testing and validating for drinking water • New developments • Examples of potable water UF plants

  3. Introduction • What is a membrane? • A membrane is a selective physical barrier used to separate a stream (gases or liquids and slurries) into its components based on their permeability through the barrier. • Common membranes processes for water treatment: • Microfiltration (MF) • Ultrafiltration (UF) • Nanofiltration (NF) • Reverse Osmosis (RO)

  4. ultrafiltration

  5. Designing an UF system • Information required: • Feed Quality: • Non ionics: turbidity, TSS, COD, TOC, color, silica • Ionics: dissolved metals, alkalinity, silica • Others: temperature, pH • Capacity: • Nominal flow • Peak flow • Required filtrate quality: • Micro biological removal efficiency • Removal of organics and color • Other considerations: • Redundancy • Footprint

  6. Components of an UF plant • Components of an UF plant • Pre-treatment • Pre-screen • UF skid • Chemical dosing unit(s) • Neutralisation unit • Backwash unit • CIP unit • Post treatment (disinfection, RO etc) • Membrane integrity test unit

  7. Components of an UF plant • Pre-treatment • Pre-treatment is installed to: • Remove particular foulants that UF is susceptible to. (e.g. Mn, Fe, FOG) • Reduce size of UF plant by reducing TSS load. • Typical UF pre-treatment processes: • DAF  removal /reduction of FOG, COD and TSS • Green sand filter  Mn and Fe removal, reduce TSS • Coagulation/Flocculation  Reduce TSS load, remove oxidised Fe and Mn • Activated carbon (GAC/PAC)  colour, odour, TOC • Oxidation  oxidation of Mn and Fe, reduction of TOC

  8. Components of an UF plant • Chemical dosing units • For pH adjustment, CEB, in-line coagulant dosing and chemical neutralisation • Typical dosing sets required: • In-line coagulation: FeCl3, alum, PACl + pH adjustment • CEB: Caustic + NaOCl + acid • Neutralisation: Reducing agent (SBS) + acid/caustic • Considerations: • Chemical dosing sets should be overdesigned to cater for deterioration in chemical stock concentration and fluctuating water quality

  9. Membrane fouling and cleaning • Types of fouling on UF membranes: • Cake formation • Pore blocking • Adsorption • Concentration Polarization

  10. Membrane fouling and cleaning • Cleaning modes: • Backwash (BW) • Relaxation • Chemical Enhanced Backwash (CEB) • Clean-In-Place (CIP)

  11. Membrane fouling and cleaning • Backwashing • Reverse the flow of filtrate at higher flux for short duration to flush out foulants from membrane surface and pores. • Effective against surface foulants, loose cake layer and partially effective against adsorbed foulants. • Relaxation • Short stoppages of filtration. (air scouring may run concurrently). • Loosen cake layer and loosely attached foulants. • Chemical Enhanced Backwash • Chemical cleaning involving a short soak duration. • Effective against adsorbed foulants. • Clean-In-Place • Long duration, chemical cleaning involving recirculation-soak cycles. • Use for recovery cleaning or with specialised chemicals for particular foulants.

  12. Membrane fouling and cleaning • UF cleaning chemicals * It is important to check back with UF supplier on chemical compatibility and dosage

  13. TESTING AND VALIDATING • One of the main requirements of governments and drinking water companies worldwide in providing drinking water: public safety • REQUIRED REMOVAL • Bacteria (e.g. Fecal bacteria) • Protozoa (e.g. Cryptosporidium and giardia) • Viruses (e.g. Enteric viruses like hepatitis) • DIRECTIVES • WHO • European directive • Long term 2 surface water treatment (USA) • APPROVALS • Potable water approvals: UK, USA, F, D, NL, AUS, JAP, CN, RU

  14. TESTING AND VALIDATING • EUROPEAN DIRECTIVE • COUNCIL DIRECTIVE 98/83/EC on the quality of water intended for human consumption (Drinking Water Directive or DWD) • For drinking water contact materials no harmonized EU regulations yet. • Four EU Member States France, Germany, the Netherlands and the United Kingdom Great Britain (4MS) announced in January 2011 that they have formalized arrangements to work together on this important aspect of the regulatory frameworks they have in place to ensure the hygienic safety of drinking water.

  15. TESTING AND VALIDATING • 4MS • The 4MS intend to adopt common, or directly comparable, practices for: • Acceptance of constituents used in materials in contact with drinking water • (4MS Common Positive List(s)) • Testing of materials • Use of common test methods and • setting acceptance levels • Specification of tests to be applied • to products • Reviewing factory production control • and setting audit testing requirements • Assessing the capabilities of • certification and testing bodies • Transition period several years, in the meantime still national approvals required

  16. TESTING AND VALIDATING • Validating for safe use: leaching of toxic chemicals • Leaching • USA NSF Std.61 (membrane module) • UK DWI reg.31 (membrane module) WRAS (ancillaries) • F ACS (membrane module plus chemicals) • D KTW, W270 DVGW (membrane fibers) • NL KIWA ata (membrane module) • CN MoH (membrane module) • RU Federal Service (membrane module)

  17. TESTING AND VALIDATING • Testing for removal efficiency of microbiology • Challenge Testing • USA: CDPH approval as Alternative Filtration Technology • Demonstration study with membrane module to show microbiological reduction of 0.5 μm microspheres (conservativeCryptosporidium/Giardiasurrogate) and MS2 virus • In-house: Challenge testing with membrane module to show microbiological reduction of MS2 virus • Non-Destructive Performance Test (Intern) • Demonstrates the Cryptosporidium/Giardiaremovalcapability of the membrane module. • DiffusiveAirflow Test

  18. TESTING AND VALIDATING • Testing during operation • Testing methods • Direct integrity testing: pressure decay airflow • Performance testing: spiking with indicator substance non-spiked (naturally present matter)

  19. TESTING AND VALIDATING • Virus Like Particles (4.3 – 6.0 log) • versus • MS2 Phages (6.6 – 8.2 log) • VLP is conservative

  20. New developments UFC – Xiga / Aquaflex HFW1000 color

  21. Hollow fiber nanofiltration • Virus Like particles Virus Like Particles (5.1 log)

  22. ULTRAFILTRATION Drinking water production

  23. Roetgen, Germany UF product flow rate 145.000 m3/d

  24. Lowerselatar water works, singapore UF product flow rate 260.000 m3/d

  25. Goteborg vatten, sweden UF product flow rate 186.000 m3/d

  26. Thankyouforyour attention!

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