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WALL MOUNT HOLLOW FIBER ULTRAFILTRATION UF SYSTEMS

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WMZ Series Wall Mount Hollow Fiber Ultrafiltration UF Systems

1,600 to 10,000 GPD

 

WMF Series Wall Mount Hollow Fiber Ultrafiltration UF Systems

2,200 to 20,000 GPD Wall Mount UF Systems

 

Both Series designed to produce clean, purified water from tap or well water, these wall-mounted systems use high efficiency ultrafiltration membranes. The filtered product water is used in commercial and residential POE/POU applications such as water stores, RO pretreatment, whole house, laboratories, bottled water and other similar applications.

 

 Call or email us for a customized quote!

 

Benefits of Ultrafiltration Systems

  • Over 30 years of experience is reflected in our quality
  • Fine filtration to 0.02 microns for bacteria, viruses and turbidity treatment
  • Low operating pressure and high efficiency
  • Reliable and durable UF Membranes for high membrane integrity
  • Compact, heavy duty, powder coated frame
  • Factory tested to ensure trouble-free operation
  • Simple installation and automatic operation

 

WMZ Series 1,600 to 10,000 GPD Economy Wall Mount Hollow Fiber UF Systems

Model No.

System Capacity

Membrane Elements

Line Size
Inlet, Filtrate, Drain 
(NPT)

System Dimensions (in/cm)

GPD

m³/day

Qty.

Size
(Dia.×L)

Length

Depth

Height

WMZ-12521A-116

1,600

6.06

1

2.5 × 21

½”

28/71

12/30

26/66

WMZ-14A-116

10,000

37.85

1

4.0 × 40

¾”

18/46

12/30

52/132

 

WMF Series 2,200 to 20,000 GPD Wall Mount Hollow Fiber UF Systems

Model No.

System Capacity

Membrane Elements

Line Size
Inlet, Filtrate, Drain 
(NPT)

System Dimensions (in/cm)

GPD

m³/day

Qty.

Size
(Dia.×L)

Length

Depth

Height

WMF-22521A-116

2,200

8

2

2.5 × 21

½”

28/71

12/30

26/66

WMF-42521A-116

4,300

16

4

2.5 × 21

½”

35/89

12/30

26/66

WMF-24A-116

13,000

50

2

4.0 × 40

¾”

29/73

12/30

52/132

WMF-44A-116

22,000

83

4

4.0 × 40

1”

36/91

12/30

52/132

 

 Notes and Voltage

  • All dimensions and weights are approximate.
  • Capacity Basis:  24 hrs/day
  • Systems rated at:  77°F (25°C) less than 1,500 ppm total dissolved solids (TDS) city water or natural groundwater well
  • Minimum feed pressure to UF System: 40 PSI. 
  • Voltage:   120 volts, single phase, 60 hertz.  220 volt available upon request
  • System capacity changes significantly with water temperature
  • Media pretreatment recommended for source water turbidity reduction, typically for well water.

 

Features

Wall-Mount UF Systems Standard Equipment

Standard Equipment 

  • Hollow fiber ultrafiltration membranes
  • PVC membrane housings/vessels
  • Liquid filled system pressure gauge
  • Corrosion resistant powder coated durable frame
  • Boxed and palletized for shipment
  • Electric actuated control valve system
  • Automated system controller
  • Inlet isolation valve

WMZ Economy Series Wall Mount UF Controller Features

Controller for Automatic Operation

Controller Features:

  • Simple operation, easy to use
  • Automatic operation including membrane flush/cleaning
  • Manual flush button

Indicator Lights:

  • In service
  • Flush clean mode 

WMF Series Wall-Mount UF Systems Controller Features

Controller for Automatic Operation

Controller Features:

  • Simple operation, easy to use
  • Automatic operation including membrane backwash/cleaning
  • Manual backwash button

Indicator Lights:

  • In service
  • Backwash flush clean mode

 

Applications

Applications for Wall Mount Hollow Fiber UF Systems

  • Purification of surface water, groundwater and spring water to make drinking water and process water
  • Pretreatment in sea water desalination plants in combination with reverse osmosis or thermal treatment
  • Water for industrial use to close water cycles and a wide variety of other applications

 

Parts



Pretreatment and Post Treatment Options

System Model No.

Carbon Filter
Post Treatment

UV Disinfection Post Treatment

Multi-Media Filter Pretreatment

1 Micron Filter Pretreatment

Pressure Tank

 WMZ-12521A-116  A725 S2Q-PA  W-MB844ET-US   A704-10-1  A612-40 
 WMZ-14A-116 A725BB   S5Q-PA W-MB1665ET-US  A704-20-1   A612-80

WMF-22521A-116

A725

S2Q-PA

W-MB844ET-US

A704-10-1

A612-40

WMF-42521A-116

A725

S2Q-PA

W-MB844ET-US

A704-10-1

A612-40

WMF-24A-116

A725BB

S5Q-PA

W-MB1665ET-US

A704-20-1

A612-80

WMF-44A-116

A725BB

S8Q-PA

W-MB1665ET-US

A704-20-1

A612-80


 

ABOUT ULTRAFILTRATION 

BY  DR. GIL DHAWAN


Ultrafiltration is a separation process using membranes with pore sizes in the range of 0.1 to 0.001 micron. Typically, ultrafiltration will remove high molecular-weight substances, colloidal materials, and organic and inorganic polymeric molecules. Low molecular-weight organics and ions such as sodium, calcium, magnesium chloride, and sulfate are not removed. Because only high-molecular weight species are removed, the osmotic pressure differential across the membrane surface is negligible. Low applied pressures are therefore sufficient to achieve high flux rates from an ultrafiltration membrane. Flux of a membrane is defined as the amount of permeate produced per unit area of membrane surface per unit time. Generally flux is expressed as gallons per square foot per day (GFD) or as cubic meters per square meters per day.

Ultrafiltration membranes can have extremely high fluxes but in most practical applications the flux varies between 50 and 200 GFD at an operating pressure of about 50 psig in contrast, reverse osmosis membranes only produce between 10 to 30 GFD at 200 to 400 psig.

 

ULTRAFILTER VS.  CONVENTIONAL FILTER

Ultrafiltration, like reverse osmosis, is a cross-flow separation process. Here liquid stream to be treated (feed) flows tangentially along the membrane surface, thereby producing two streams. The stream of liquid that comes through the membrane is called permeate. The type and amount of species left in the permeate will depend on the characteristics of the membrane, the operating conditions, and the quality of feed. The other liquid stream is called concentrate and gets progressively concentrated in those species removed by the membrane. In cross-flow separation, therefore, the membrane itself does not act as a collector of ions, molecules, or colloids but merely as a barrier to these species.                                        

Conventional filters such as media filters or cartridge filters, on the other hand, only remove suspended solids by trapping these in the pores of the filter-media. These filters therefore act as depositories of suspended solids and have to be cleaned or replaced frequently. Conventional filters are used upstream from the membrane system to remove relatively large suspended solids and to let the membrane do the job of removing fine particles and dissolved solids. In ultrafiltration, for many applications, no prefilters are used and ultrafiltration modules concentrate all of the suspended and emulsified materials.

 

CONCENTRATION POLARIZATION

When a membrane is used for a separation, the concentration of any species being removed is higher near the membrane surface than it is in the bulk of the stream. This condition is known as concentration polarization and exists in all ultrafiltration and reverse osmosis separations. The result of concentration polarization is the formation of a boundary layer of substantially high concentration of substances being removed by the membrane. The thickness of the layer and its concentration depend on the mass of transfer conditions that exist in the membrane system. Membrane flux and feed flow velocity are both important in controlling the thickness and the concentration in the boundary layer. The boundary layer impedes the flow of water through the membrane and the high concentration of species in the boundary layer produces a permeate of inferior quality in ultrafiltration applications relatively high fluid velocities are maintained along the membrane surface to reduce the concentration polarization effect.

 

RECOVERY

Recovery of an ultrafiltration system is defined as the percentage of the feed water that is converted into the permeate, or:

R=    P   × 100

         F               

Where:

R =       Recovery

P =       Volume of permeate

F =       Volume of Feed

 

ULTRAFILTRATION MEMBRANES

Ultrafiltration Membrane modules come in plate-and-frame, spiral-wound, and tubular configurations. All configurations have been used successfully in different process applications. Each configuration is especially suited for some specific applications and there are many applications where more than one configuration is appropriate. For high purity water, spiral-wound and capillary configurations are generally used. The configuration selected depends on the type and concentration of colloidal material or emulsion. For more concentrated solutions, more open configurations like plate-and-frame and tubular are used. In all configurations the optimum system design must take into consideration the flow velocity, pressure drop, power consumption, membrane fouling and module cost.

 

MEMBRANE MATERIALS

A variety of materials have been used for commercial ultrafiltration membranes, but polysulfone and cellulose acetate are the most common. Recently thin-film composite ultrafiltration membranes have been marketed. For high purity water applications the membrane module materials must be compatible with chemicals such as hydrogen peroxide used in sanitizing the membranes on a periodic basis.

 

MOLECULAR-WEIGHT CUTOFF

Pore sizes for ultrafiltration membranes range between 0.001 and 0.1 micron. However, it is more customary to categorize membranes by molecular-weight cutoff. For instance, a membrane that removes dissolved solids with molecular weights of 10,000 and higher has a molecular weight cutoff of 10,000. Obviously, different membranes even with the same molecular-weight cutoff, will have different pore size distribution. In other words, different membranes may remove species of different molecular weights to different degrees. Nevertheless, molecular-weight cutoff serves as a useful guide when selecting a membrane for a particular application.

 

FACTORS AFFECTING THE PERFORMANCE OF  ULTRAFILTRATION

There are several factors that can affect the performance of an ultrafiltration system. A brief discussion of these is given here.

 

FLOW ACROSS THE MEMBRANE SURFACE

velocity if especially critical for liquids containing emulsions or suspensions. Higher flow also means higher energy consumption and larger pumps. Increasing the flow velocity also reduces the fouling of the membrane surface. Generally, an optimum flow velocity is arrived at by a compromise between the pump horsepower and increase in permeate rate.
The permeate rate increases with the flow velocity of the liquid across the membrane surface. Flow


PERFORMANCE OF ULTRAFILTRATION SYSTEM

In high purity water systems, ultrafiltration is slowly replacing the traditional 0.2-micron cartridge filters. In Japan, practically all of the semiconductor industry follows this practice. An ultrafiltration membrane with a molecular-weight cutoff of 10,000 has a nominal pore size of 0.003 micron. When an ultrafiltration membrane is used instead of a 0.2-micron cartridge filter, particle removal efficiency is greatly improved. In addition, ultrafiltration membranes are not susceptible to the problem of bacteria growing through them, as is the case with 0.2-micron filters.

In a recent study (1), the performance of an ultrafilter was compared with that of a 0.2-micron cartridge filter. Some of these results are given in Table A.

The Ultrafilter used in the study had a molecular-weight cutoff of 100,000- (pore size 0.006 micron). As the requirements for the quality of high purity water become more stringent, we can expect to see an increasing use of ultrafiltration as a final filter.

 

TABLE A: EFFECTIVENESS OF ULTRAFILTRATION PARTICLE COUNTS ON WATERS

Test Location

0.2 Micron Filtered DI Rinse Water

Unfiltered

DI Rinse Water

1

200-300

20-30*

2

175-200

0-25

3

120

5

4

275

125*

 

OPERATION AND MAINTENANCE

Ultrafiltration system operation and maintenance is similar to that of reverse osmosis systems. Daily records of feed and permeate flow, feed pressure and temperature, and pressure drop across the system should be kept. Membranes should be cleaned when the system permeate rate drops by 10% or more. Feed flow is critical to the operation of ultrafiltration systems. A drop in feed flow may be due to a problem in the prefilter (if any), with the flow control valve, or with the pump itself. When the system is shut down for more than two days, a bacteriocide should be circulated through the membranes. At restart, permeate should be diverted to drain until all the bacteriocide is removed.

 

 CONCLUSIONS

Ultrafiltration will find an increasing application in the production of high purity water. The basic principles outlined here should help in the understanding and use of this technology.

 

REFERENCE

1Gaudet, P.W. "Point-of-use Ultrafiltration of Deionized Water and Effects of Microelectronics Device Quality, American Society for Testing and Materials", 1984.

 

GLOSSARY OF TERMS 

  • Feed - Liquid to be treated by the ultrafiltration
  • Permeate - Liquid stream that passes through the
  • Concentrate - Remaining Portion of the liquid stream after the permeate has been
  • Recovery - Expressed as percentage, this defines the permeate rate as a fraction of the feed rate. Recovery provides an immediate measure of the maximum concentrations in the system and it affects permeate quality, pump size, power consumption and membrane
  • Flux - Permeate flow per unit area of membrane per unit time (gallons/ft²/day)
  • Rejection - Percent removal of a particular species by the membrane. Expressed as 1-CP CF where CP is the concentration in the permeate, and CF is the concentration in the
  • Flow Velocity - Rate at which the liquid goes along the membrane surface, expresse d in length per unit time (ft/sec).

 

THE AUTHOR

Dr. Gil Dhawan is the president of Applied Membranes, Inc. based in Vista, CA. Dr. Dhawan has been involved in the design, development, and marketing of ultrafiltration and reverse osmosis systems for the past 35 years.

 

Order Confirmation:

As soon as you place your order, you will receive an order confirmation e-mail.  This means that we have received your order in our system and pre-authorized your credit card for the purchase.  As soon as we receive your order, we automatically reach out to our suppliers to confirm that it is in stock and available for immediate shipment.  If your item is on backorder or unavailable, we will void the pre-authorization and reach out to you via e-mail.  If your item(s) are available for immediate shipment (within 5 business days), we will process the charges and submit the order for shipment.

*Free Shipping Over $100.00 Shipping not available for Alaska or Hawaii

Order Shipment:

If your order is stock and we process the charges to your credit card, it will ship within five business days from the date of your order.  We will send you tracking information within 24 hours of your order leaving the warehouse to the e-mail address your provide when checking out.  If you do not receive tracking information from us within six business days of your order, feel free to follow up with us at info@purewaterguys.com.

 

USPS     UPS      

 

 

Damages:

Please inspect the packaging of your item(s) when they arrive, if you notice any damage you should make note of it when signing for delivery.  If your item(s) do arrived damaged, please send photos to info@purewaterguys.com and we will process an insurance claim on your behalf.

Cancellations & Refunds:

All orders cancelled after 48 hours are subject to a $20 administration fee, whether or not your order has shipped.  If you order has shipped, you (the buyer) will also be responsible for actual return shipping charges. Refunds will only be issued to the original credit card that you use when placing your order.

*shipping charges may be applied to certain products or brands that are over-sized weight or dimensions. Or that require freight shippping.

Our 100% Price Match Guarantee

We work very hard to ensure that we offer the absolute best prices online.  If you find another online store that offers a lower price then us within six months of your purchase date please let us know and we will refund your original payment for the difference.  We want you to feel confident that you are getting the absolute best price for the product you are ordering.  If you find that our own website has a lower price for the same item you have ordered within six months of your purchase date will refund the difference as well.

To request your partial refund simply e-mail us a link to the same product on our website, or on our competitors website within six months from the date of your order and we will process the credit accordingly.

Our 100% Price Guarantee has some limitations:

  • You must purchase the item from our website before requesting your Price Match Guarantee
  • Promotions such as rebates and buy one, get one free offers are not eligible
  • The item must be in stock on the competitors website
  • The competitor must be an online store, they may not have a retail location
  • The website can not be a discounter or auction website (ie; eBay, overstock, etc..)
  • The competitor must be an Authorized Retailer of the product in question
  • The Price Match Guarantee includes the item price and the shipping charges, it excludes sales tax

WMZ Series Wall Mount Hollow Fiber Ultrafiltration UF Systems

1,600 to 10,000 GPD

 

WMF Series Wall Mount Hollow Fiber Ultrafiltration UF Systems

2,200 to 20,000 GPD Wall Mount UF Systems

 

Both Series designed to produce clean, purified water from tap or well water, these wall-mounted systems use high efficiency ultrafiltration membranes. The filtered product water is used in commercial and residential POE/POU applications such as water stores, RO pretreatment, whole house, laboratories, bottled water and other similar applications.

 

 Call or email us for a customized quote!

 

Benefits of Ultrafiltration Systems

  • Over 30 years of experience is reflected in our quality
  • Fine filtration to 0.02 microns for bacteria, viruses and turbidity treatment
  • Low operating pressure and high efficiency
  • Reliable and durable UF Membranes for high membrane integrity
  • Compact, heavy duty, powder coated frame
  • Factory tested to ensure trouble-free operation
  • Simple installation and automatic operation

 

WMZ Series 1,600 to 10,000 GPD Economy Wall Mount Hollow Fiber UF Systems

Model No.

System Capacity

Membrane Elements

Line Size
Inlet, Filtrate, Drain 
(NPT)

System Dimensions (in/cm)

GPD

m³/day

Qty.

Size
(Dia.×L)

Length

Depth

Height

WMZ-12521A-116

1,600

6.06

1

2.5 × 21

½”

28/71

12/30

26/66

WMZ-14A-116

10,000

37.85

1

4.0 × 40

¾”

18/46

12/30

52/132

 

WMF Series 2,200 to 20,000 GPD Wall Mount Hollow Fiber UF Systems

Model No.

System Capacity

Membrane Elements

Line Size
Inlet, Filtrate, Drain 
(NPT)

System Dimensions (in/cm)

GPD

m³/day

Qty.

Size
(Dia.×L)

Length

Depth

Height

WMF-22521A-116

2,200

8

2

2.5 × 21

½”

28/71

12/30

26/66

WMF-42521A-116

4,300

16

4

2.5 × 21

½”

35/89

12/30

26/66

WMF-24A-116

13,000

50

2

4.0 × 40

¾”

29/73

12/30

52/132

WMF-44A-116

22,000

83

4

4.0 × 40

1”

36/91

12/30

52/132

 

 Notes and Voltage

  • All dimensions and weights are approximate.
  • Capacity Basis:  24 hrs/day
  • Systems rated at:  77°F (25°C) less than 1,500 ppm total dissolved solids (TDS) city water or natural groundwater well
  • Minimum feed pressure to UF System: 40 PSI. 
  • Voltage:   120 volts, single phase, 60 hertz.  220 volt available upon request
  • System capacity changes significantly with water temperature
  • Media pretreatment recommended for source water turbidity reduction, typically for well water.

 

Features

Wall-Mount UF Systems Standard Equipment

Standard Equipment 

  • Hollow fiber ultrafiltration membranes
  • PVC membrane housings/vessels
  • Liquid filled system pressure gauge
  • Corrosion resistant powder coated durable frame
  • Boxed and palletized for shipment
  • Electric actuated control valve system
  • Automated system controller
  • Inlet isolation valve

WMZ Economy Series Wall Mount UF Controller Features

Controller for Automatic Operation

Controller Features:

  • Simple operation, easy to use
  • Automatic operation including membrane flush/cleaning
  • Manual flush button

Indicator Lights:

  • In service
  • Flush clean mode 

WMF Series Wall-Mount UF Systems Controller Features

Controller for Automatic Operation

Controller Features:

  • Simple operation, easy to use
  • Automatic operation including membrane backwash/cleaning
  • Manual backwash button

Indicator Lights:

  • In service
  • Backwash flush clean mode

 

Applications

Applications for Wall Mount Hollow Fiber UF Systems

  • Purification of surface water, groundwater and spring water to make drinking water and process water
  • Pretreatment in sea water desalination plants in combination with reverse osmosis or thermal treatment
  • Water for industrial use to close water cycles and a wide variety of other applications

 

Parts



Pretreatment and Post Treatment Options

System Model No.

Carbon Filter
Post Treatment

UV Disinfection Post Treatment

Multi-Media Filter Pretreatment

1 Micron Filter Pretreatment

Pressure Tank

 WMZ-12521A-116  A725 S2Q-PA  W-MB844ET-US   A704-10-1  A612-40 
 WMZ-14A-116 A725BB   S5Q-PA W-MB1665ET-US  A704-20-1   A612-80

WMF-22521A-116

A725

S2Q-PA

W-MB844ET-US

A704-10-1

A612-40

WMF-42521A-116

A725

S2Q-PA

W-MB844ET-US

A704-10-1

A612-40

WMF-24A-116

A725BB

S5Q-PA

W-MB1665ET-US

A704-20-1

A612-80

WMF-44A-116

A725BB

S8Q-PA

W-MB1665ET-US

A704-20-1

A612-80


 

ABOUT ULTRAFILTRATION 

BY  DR. GIL DHAWAN


Ultrafiltration is a separation process using membranes with pore sizes in the range of 0.1 to 0.001 micron. Typically, ultrafiltration will remove high molecular-weight substances, colloidal materials, and organic and inorganic polymeric molecules. Low molecular-weight organics and ions such as sodium, calcium, magnesium chloride, and sulfate are not removed. Because only high-molecular weight species are removed, the osmotic pressure differential across the membrane surface is negligible. Low applied pressures are therefore sufficient to achieve high flux rates from an ultrafiltration membrane. Flux of a membrane is defined as the amount of permeate produced per unit area of membrane surface per unit time. Generally flux is expressed as gallons per square foot per day (GFD) or as cubic meters per square meters per day.

Ultrafiltration membranes can have extremely high fluxes but in most practical applications the flux varies between 50 and 200 GFD at an operating pressure of about 50 psig in contrast, reverse osmosis membranes only produce between 10 to 30 GFD at 200 to 400 psig.

 

ULTRAFILTER VS.  CONVENTIONAL FILTER

Ultrafiltration, like reverse osmosis, is a cross-flow separation process. Here liquid stream to be treated (feed) flows tangentially along the membrane surface, thereby producing two streams. The stream of liquid that comes through the membrane is called permeate. The type and amount of species left in the permeate will depend on the characteristics of the membrane, the operating conditions, and the quality of feed. The other liquid stream is called concentrate and gets progressively concentrated in those species removed by the membrane. In cross-flow separation, therefore, the membrane itself does not act as a collector of ions, molecules, or colloids but merely as a barrier to these species.                                        

Conventional filters such as media filters or cartridge filters, on the other hand, only remove suspended solids by trapping these in the pores of the filter-media. These filters therefore act as depositories of suspended solids and have to be cleaned or replaced frequently. Conventional filters are used upstream from the membrane system to remove relatively large suspended solids and to let the membrane do the job of removing fine particles and dissolved solids. In ultrafiltration, for many applications, no prefilters are used and ultrafiltration modules concentrate all of the suspended and emulsified materials.

 

CONCENTRATION POLARIZATION

When a membrane is used for a separation, the concentration of any species being removed is higher near the membrane surface than it is in the bulk of the stream. This condition is known as concentration polarization and exists in all ultrafiltration and reverse osmosis separations. The result of concentration polarization is the formation of a boundary layer of substantially high concentration of substances being removed by the membrane. The thickness of the layer and its concentration depend on the mass of transfer conditions that exist in the membrane system. Membrane flux and feed flow velocity are both important in controlling the thickness and the concentration in the boundary layer. The boundary layer impedes the flow of water through the membrane and the high concentration of species in the boundary layer produces a permeate of inferior quality in ultrafiltration applications relatively high fluid velocities are maintained along the membrane surface to reduce the concentration polarization effect.

 

RECOVERY

Recovery of an ultrafiltration system is defined as the percentage of the feed water that is converted into the permeate, or:

R=    P   × 100

         F               

Where:

R =       Recovery

P =       Volume of permeate

F =       Volume of Feed

 

ULTRAFILTRATION MEMBRANES

Ultrafiltration Membrane modules come in plate-and-frame, spiral-wound, and tubular configurations. All configurations have been used successfully in different process applications. Each configuration is especially suited for some specific applications and there are many applications where more than one configuration is appropriate. For high purity water, spiral-wound and capillary configurations are generally used. The configuration selected depends on the type and concentration of colloidal material or emulsion. For more concentrated solutions, more open configurations like plate-and-frame and tubular are used. In all configurations the optimum system design must take into consideration the flow velocity, pressure drop, power consumption, membrane fouling and module cost.

 

MEMBRANE MATERIALS

A variety of materials have been used for commercial ultrafiltration membranes, but polysulfone and cellulose acetate are the most common. Recently thin-film composite ultrafiltration membranes have been marketed. For high purity water applications the membrane module materials must be compatible with chemicals such as hydrogen peroxide used in sanitizing the membranes on a periodic basis.

 

MOLECULAR-WEIGHT CUTOFF

Pore sizes for ultrafiltration membranes range between 0.001 and 0.1 micron. However, it is more customary to categorize membranes by molecular-weight cutoff. For instance, a membrane that removes dissolved solids with molecular weights of 10,000 and higher has a molecular weight cutoff of 10,000. Obviously, different membranes even with the same molecular-weight cutoff, will have different pore size distribution. In other words, different membranes may remove species of different molecular weights to different degrees. Nevertheless, molecular-weight cutoff serves as a useful guide when selecting a membrane for a particular application.

 

FACTORS AFFECTING THE PERFORMANCE OF  ULTRAFILTRATION

There are several factors that can affect the performance of an ultrafiltration system. A brief discussion of these is given here.

 

FLOW ACROSS THE MEMBRANE SURFACE

velocity if especially critical for liquids containing emulsions or suspensions. Higher flow also means higher energy consumption and larger pumps. Increasing the flow velocity also reduces the fouling of the membrane surface. Generally, an optimum flow velocity is arrived at by a compromise between the pump horsepower and increase in permeate rate.
The permeate rate increases with the flow velocity of the liquid across the membrane surface. Flow


PERFORMANCE OF ULTRAFILTRATION SYSTEM

In high purity water systems, ultrafiltration is slowly replacing the traditional 0.2-micron cartridge filters. In Japan, practically all of the semiconductor industry follows this practice. An ultrafiltration membrane with a molecular-weight cutoff of 10,000 has a nominal pore size of 0.003 micron. When an ultrafiltration membrane is used instead of a 0.2-micron cartridge filter, particle removal efficiency is greatly improved. In addition, ultrafiltration membranes are not susceptible to the problem of bacteria growing through them, as is the case with 0.2-micron filters.

In a recent study (1), the performance of an ultrafilter was compared with that of a 0.2-micron cartridge filter. Some of these results are given in Table A.

The Ultrafilter used in the study had a molecular-weight cutoff of 100,000- (pore size 0.006 micron). As the requirements for the quality of high purity water become more stringent, we can expect to see an increasing use of ultrafiltration as a final filter.

 

TABLE A: EFFECTIVENESS OF ULTRAFILTRATION PARTICLE COUNTS ON WATERS

Test Location

0.2 Micron Filtered DI Rinse Water

Unfiltered

DI Rinse Water

1

200-300

20-30*

2

175-200

0-25

3

120

5

4

275

125*

 

OPERATION AND MAINTENANCE

Ultrafiltration system operation and maintenance is similar to that of reverse osmosis systems. Daily records of feed and permeate flow, feed pressure and temperature, and pressure drop across the system should be kept. Membranes should be cleaned when the system permeate rate drops by 10% or more. Feed flow is critical to the operation of ultrafiltration systems. A drop in feed flow may be due to a problem in the prefilter (if any), with the flow control valve, or with the pump itself. When the system is shut down for more than two days, a bacteriocide should be circulated through the membranes. At restart, permeate should be diverted to drain until all the bacteriocide is removed.

 

 CONCLUSIONS

Ultrafiltration will find an increasing application in the production of high purity water. The basic principles outlined here should help in the understanding and use of this technology.

 

REFERENCE

1Gaudet, P.W. "Point-of-use Ultrafiltration of Deionized Water and Effects of Microelectronics Device Quality, American Society for Testing and Materials", 1984.

 

GLOSSARY OF TERMS 

  • Feed - Liquid to be treated by the ultrafiltration
  • Permeate - Liquid stream that passes through the
  • Concentrate - Remaining Portion of the liquid stream after the permeate has been
  • Recovery - Expressed as percentage, this defines the permeate rate as a fraction of the feed rate. Recovery provides an immediate measure of the maximum concentrations in the system and it affects permeate quality, pump size, power consumption and membrane
  • Flux - Permeate flow per unit area of membrane per unit time (gallons/ft²/day)
  • Rejection - Percent removal of a particular species by the membrane. Expressed as 1-CP CF where CP is the concentration in the permeate, and CF is the concentration in the
  • Flow Velocity - Rate at which the liquid goes along the membrane surface, expresse d in length per unit time (ft/sec).

 

THE AUTHOR

Dr. Gil Dhawan is the president of Applied Membranes, Inc. based in Vista, CA. Dr. Dhawan has been involved in the design, development, and marketing of ultrafiltration and reverse osmosis systems for the past 35 years.

 

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