Membrane Technology

MEMBRANE TECHNOLOGY: 

MEMBRANE TECHNOLOGY Paulus Hartanto

Membrane Filtration Technology: 

Membrane Filtration Technology

Filtration Spectrum: 

Filtration Spectrum

Cross Flow Filtration: 

Cross Flow Filtration

Dead End Filtration: 

Dead End Filtration

Application of membrane processes in water environment: 

Application of membrane processes in water environment

Factors affecting membrane performance: 

Factors affecting membrane performance

What is membrane ?: 

What is membrane ?

Conventional vs Membrane Filtration: 

Conventional vs Membrane Filtration

Classification of membrane processes: 

Classification of membrane processes

Phases divided by membrane: 

Phases divided by membrane

Some membrane processes and driving forces: 

Some membrane processes and driving forces

More common membrane processes: 

More common membrane processes

Flux range & trans-membrane pressure in pressure driven membrane: 

Flux range & trans-membrane pressure in pressure driven membrane

Membrane distillation vs Osmotic distillation: 

Membrane distillation vs Osmotic distillation

Historical development of membranes: 

Historical development of membranes

Classification of filter (membrane): 

Classification of filter (membrane)

Depth filter vs screen filter: 

Depth filter vs screen filter

Depth filter: 

Depth filter

Screen filter: 

Screen filter

Advantages of screen filter: 

Advantages of screen filter

Absolute vs Nominal rating: 

Absolute vs Nominal rating

Microporous vs Asymmetric: 

Microporous vs Asymmetric

Membrane classification (poresize): 

Membrane classification (poresize) Colloids Bacteria Pollens Yeasts Organic macromolecules Organic compounds Viruses Dissolved salts RO NF MF 1 m m 0.1 m m 0.01 m m 0. 1 nm 0. 1 nm 10 m m 100 m m hair visible to naked eye Red globule Smallest microorganisms Polio virus UF Microfiltration Ultrafiltration Nanofiltration

Membrane classification (pressure range): 

Membrane classification (pressure range)

Rejection Capabilities UF vs MF: 

Rejection Capabilities UF vs MF

Process combinations: 

Process combinations

Membrane classification (driving force): 

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

Membrane classification (driving force): 

Membrane classification (driving force) Pressure (Canister Membranes) More compact design Cannot handle high solid concentration (> 100 NTU) for a substantial period of time

Membrane classification (configuration): 

Membrane classification (configuration) Open feed channel configuration : Tubular Hollow-Fiber Narrow feed channel configuration Spiral (Flat sheet)

Membrane classification (configuration): 

Membrane classification (configuration) Flat Sheet (Spiral-wound) Mostly used in Reverse Osmosis & Nanofiltration

Membrane classification (configuration): 

Membrane classification (configuration) Tubular Membranes (OD > 3 mm) Mostly used in Industrial MF

Membrane classification (configuration): 

Membrane classification (configuration) Hollow Fiber Membranes (ID < 1.5 mm) Mostly used in MF & UF

Membrane classification (Location of membrane): 

Membrane classification (Location of membrane) Inside-out Membranes Outside-In Membranes Raw Water Filtered Water

Membranes Applications: 

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

Membrane vs Sand: 

Membrane vs Sand Membrane filtration mechanism Sieving/Straining Sand filtration mechanism Interception, collision, electrostatic attraction Straining only happens in cake filtration

Finished water comparison: 

Finished water comparison Conventional Membranes Turbidity 0.05 ~ 0.3 < 0.1 Virus removal 2 log > 4 log Influent quality change Affected Not affected Water chemistry change Affected Not affected Operating conditions change Affected Not affected

Performance comparison: 

Performance comparison Conventional Membranes High 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 cleaning High FeCl 3 dose Shorter run time FeCl 3 not required Low feed temp. Not affected Higher pressure or lower output Capacity increase Shorter run time Higher pressure, need freq. chemical cleaning

Typical Membrane Filtration Cycle : 

Typical Membrane Filtration Cycle Filtration (15 ~ 50 minutes) Backwash (20 sec ~ 2 min) (No rinsing, surface wash, or filter-to-waste) Chemical Cleaning Membrane Repair Special Operation/Maintenance

Membrane Fouling (performance): 

Membrane Fouling (performance)

Fouling is part of membranes: 

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)

Potential Fouling Material Natural Organic Matter: 

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. H 2 O 2 ) are effective for NOM fouling cleaning

Potential Fouling Material Particulate/Colloids: 

Potential Fouling Material Particulate/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

Potential Fouling Material Inorganic Material: 

Potential Fouling Material Inorganic Material Precipitation of Ca, Mn , Mg, Fe, and Al could cause significant fouling Fine inorganic colloids (< 0.05 m m) 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[HCO 3 - ] L.I. > 0 : Oversaturated (tend to precipitate) L.I. < 0 : Undersaturated (tend to dissolve more)

Potential Fouling Material Synthetic Polymers: 

Potential Fouling Material Synthetic 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

Fouling Mitigation Pretreatment: 

Fouling Mitigation Pretreatment 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

Fouling Mitigation Operation: 

Fouling Mitigation Operation 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

Fouling Mitigation Cleaning Strategy: 

Fouling Mitigation Cleaning Strategy Frequent BW (shorter filtration cycle) Longer BW duration Higher BW pressure Add cleaning chemicals in BW water Frequent chemical cleaning

Membrane Cleaning Membrane Fouling Mechanisms: 

Membrane Cleaning Membrane Fouling Mechanisms Organic & Inorganic Particulate & Soluble Various Mechanisms Surface & Pore Adsorption, precipitation, coagulation

Membrane Cleaning: 

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 H 2 O 2 Reducing agent, such as SBS Chelating chemicals, such as EDTA Proprietary Chemicals (surfactants)

Summary of Fouling Material & Cleaning Chemicals: 

Summary of Fouling Material & Cleaning Chemicals Cleaning Chemical For Fouling Material NaOCl Biological; NOM; Synthetic polymers Acids (HCl, H 2 SO 4 , Citric Acid) Inorganic deposits NaOH NOM Sodium bi-sulfite (SBS) Reducible metals (Fe, Mn) H 2 O 2 NOM EDTA Metals

Membrane Integrity: 

Membrane Integrity Membrane failure is rarely catastrophic – less serious than microbial penetration of rapid sand filter beds . Membranes fail incrementally – one fiber at a time. Statistically, individual fiber breaks are insignificant to the overall microbial water quality. Membrane Integrity

Membrane Integrity Monitoring: 

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)

The Secret of Membranes…: 

The Secret of Membranes… Finding the balance point between Fouling-Enhancers and Fouling Reducers is the KEY! Cleaning Water Quality High Production High Recovery Manageable Problematic Fouling Index

Take Away Points: 

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

The End: 

The End