1. Design of Ultrafiltration plants for safe drinking water Frans Knops Mark Steggink Irene 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: Capacity:
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
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 (conservative Cryptosporidium/Giardia surrogate) 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/Giardia removal capability of the membrane module.
Diffusive Airflow 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
HFW1000 color
UFC – Xiga / Aquaflex

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 m3/d

24. Lower selatar water works, singapore
UF product flow rate m3/d

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

26. Thank you for your attention!