Fundamentals of Ultrafiltration

Design of Ultrafiltration plants for safe drinking water

Frans KnopsMark StegginkIrene Krbl

X-FlowPENTAIR X-FlowContentsIntroductionUltrafiltration Designing an UF system Components of an UF plant Membrane fouling and cleaning Testing and validating for drinking waterNew developmentsExamples of potable water UF plants2PENTAIR X-FlowIntroduction 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)

3PENTAIR X-Flowultrafiltration4

PENTAIR X-FlowDesigning an UF system Information required:Feed Quality:Non ionics: turbidity, TSS, COD, TOC, color, silicaIonics: dissolved metals, alkalinity, silica Others: temperature, pH

Capacity:Nominal flowPeak flow

Required filtrate quality:Micro biological removal efficiencyRemoval of organics and color

Other considerations:RedundancyFootprint

PENTAIR X-FlowComponents of an UF plant Components of an UF plantPre-treatmentPre-screenUF skidChemical dosing unit(s)Neutralisation unitBackwash unitCIP unit Post treatment (disinfection, RO etc)Membrane integrity test unitPENTAIR X-FlowComponents of an UF plant Pre-treatmentPre-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 TSSGreen sand filter Mn and Fe removal, reduce TSSCoagulation/Flocculation Reduce TSS load, remove oxidised Fe and MnActivated carbon (GAC/PAC) colour, odour, TOCOxidation oxidation of Mn and Fe, reduction of TOC

PENTAIR X-FlowComponents of an UF plant Chemical dosing unitsFor pH adjustment, CEB, in-line coagulant dosing and chemical neutralisation

Typical dosing sets required:In-line coagulation: FeCl3, alum, PACl + pH adjustmentCEB: Caustic + NaOCl + acidNeutralisation: Reducing agent (SBS) + acid/caustic

Considerations:Chemical dosing sets should be overdesigned to cater for deterioration in chemical stock concentration and fluctuating water quality

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Membrane fouling and cleaning Types of fouling on UF membranes:Cake formationPore blockingAdsorptionConcentration Polarization

PENTAIR X-FlowMembrane fouling and cleaning Cleaning modes:Backwash (BW)RelaxationChemical Enhanced Backwash (CEB)Clean-In-Place (CIP)

PENTAIR X-FlowMembrane fouling and cleaning BackwashingReverse 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.

RelaxationShort stoppages of filtration. (air scouring may run concurrently).Loosen cake layer and loosely attached foulants.

Chemical Enhanced BackwashChemical cleaning involving a short soak duration.Effective against adsorbed foulants.

Clean-In-PlaceLong duration, chemical cleaning involving recirculation-soak cycles.Use for recovery cleaning or with specialised chemicals for particular foulants.

PENTAIR X-FlowMembrane fouling and cleaning UF cleaning chemicals* It is important to check back with UF supplier on chemical compatibility and dosage

PENTAIR X-FlowOne of the main requirements of governments and drinking water companies worldwide in providing drinking water: public safety

REQUIRED REMOVALBacteria (e.g. Fecal bacteria)Protozoa (e.g. Cryptosporidium and giardia)Viruses (e.g. Enteric viruses like hepatitis)

DIRECTIVESWHO European directiveLong term 2 surface water treatment (USA)

APPROVALSPotable water approvals: UK, USA, F, D, NL, AUS, JAP, CN, RU13TESTING AND VALIDATING PENTAIR X-FlowEUROPEAN 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.

14TESTING AND VALIDATINGPENTAIR X-Flow4MSThe 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 materialsUse of common test methods and setting acceptance levelsSpecification of tests to be applied to productsReviewing factory production control and setting audit testing requirementsAssessing the capabilities of certification and testing bodies

Transition period several years, in the meantime still national approvals required

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PENTAIR X-FlowValidating for safe use: leaching of toxic chemicals

LeachingUSA NSF Std.61 (membrane module)UK DWI reg.31 (membrane module) WRAS (ancillaries)F ACS (membrane module plus chemicals)DKTW, W270 DVGW (membrane fibers)NLKIWA ata (membrane module)CNMoH (membrane module)RUFederal Service (membrane module)

16TESTING AND VALIDATINGPENTAIR X-FlowTesting for removal efficiency of microbiology

Challenge TestingUSA:CDPH approval as Alternative Filtration TechnologyDemonstration study with membrane module to show microbiological reduction of 0.5 m microspheres (conservative Cryptosporidium/Giardia surrogate) and MS2 virusIn-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

17TESTING AND VALIDATINGPENTAIR X-FlowTesting during operation

Testing methodsDirect integrity testing:pressure decay airflowPerformance testing:spiking with indicator substance non-spiked (naturally present matter)

18TESTING AND VALIDATINGPENTAIR X-FlowVirus Like Particles (4.3 6.0 log)versus MS2 Phages (6.6 8.2 log)

VLP is conservative19TESTING AND VALIDATING

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UFC Xiga / AquaflexHFW1000 colorNew developmentsPENTAIR X-FlowVirus Like particles21Hollow fiber nanofiltration

Virus Like Particles (5.1 log)PENTAIR X-FlowULTRAFILTRATIONDrinking water production22

PENTAIR X-FlowPENTAIR X-FlowRoetgen, Germany23UF product flow rate145.000 m3/d

PENTAIR X-FlowLower selatar water works, singapore24UF product flow rate260.000 m3/d

PENTAIR X-FlowGoteborg vatten, sweden25UF product flow rate186.000 m3/d

PENTAIR X-FlowThank you for your attention!26PENTAIR X-FlowPENTAIR X-Flow