About Ultrafiltration



If you’re new to ultrafiltration (UF) technology and applications, you’re probably asking, “what is ultrafiltration?” We can help you gain the knowledge you need by providing you with information about ultrafiltration technology and membranes and a few project installations. Start with the background information below for a high-level overview of UF technology and hollow fiber membrane technology.  Also visit the skids and modules product pages for specific information about the Dow family of ultrafiltration products:  DOW™ Ultrafiltration Modules, DOW IntegraFlo™ Modules, and DOW IntegraPac™ Skids.

Also read the latest ultrafiltration news from Dow along with water trends and water solutions. For more information, visit the resources page or simply contact an expert to start the conversation.  We look forward to the opportunity to discuss separation and purification technologies that best meet your needs.

What is Ultrafiltration

Sand filters and media filtration have been around since the 1800s. However, as with most conventional filtration methods, they require consistent raw water quality to deliver quality effluent, which is not always possible. They also don't provide an absolute barrier. Traditional media filters typically remove particles to down to about 0.5 microns.

Ultrafiltration (UF), however, does not suffer from those limitations. This technology uses a membrane barrier to exclude particles as small as 0.01 microns, including bacteria, viruses and colloids, meeting increasingly stringent water quality standards around the world providing a stable, reliable and consistent water quality.

UF offers:

  • High and consistent product quality measured by turbidity (NTU), silt density index (SDI) or log removal value (LRV).
  • Tolerance to feed water quality upsets.
  • No use of pretreatment chemicals (polymer, coagulant, pH adjustment) and associated costs for sludge disposal.
  • Small footprint and less weight than media filters.

When used as a pre-treatment for reverse osmosis (RO), UF also helps reduce fouling of RO membranes, which can lead to:

  • Reduced chemical cleaning frequency and consequently, lower operating costs and downtime.
  • The potential to operate RO at higher flux, with fewer membranes and vessels – leading to lower capital cost for the RO system.

UF Technology Basics

Ultrafiltration (UF) is a pressure-driven purification process in which water and low molecular weight substances pass through a membrane while particles, colloids and macromolecules are rejected, yet does not remove ions and small molecules.  Flow through the semi-permeable membrane is achieved by applying a pressure gradient between the outer and inner walls of the membrane structure.  Typical feed pressure is from 4 to 100 psig and a transmembrane pressure is generally <14 psig.

UF membranes typically have pore sizes in the range of 0.01-0.05 µm which contributes to a high removal capability of bacteria, viruses, colloids and silt, thereby producing high-quality water. UF membranes typically have a service life of three to seven years or longer, compared to reverse osmosis membranes. They are commercially available in hollow fiber, tubular, plate and frame, and spiral wound configurations.

To learn about the basics of DOW™ Ultrafiltration Technology, check out these videos:


 


 

Hollow Fiber Membrane Technology

Hollow Fiber Membrane Technology

DOW™ Ultrafiltration Modules are made with high strength, hollow fiber membranes that offer the following features:

 

  • 0.03 μm nominal pore diameter to facilitate high removal capability for bacteria, viruses and particulates including colloids.
  • PVDF polymeric hollow fibers for high strength and chemical resistance.
  • Hydrophilic PVDF fibers for easy cleaning and wettability to help maintain long-term performance.
  • Outside-In flow configuration for high tolerance to feed solids and the use of air scour cleaning.
  • U-PVC housings eliminate the need for pressure vessels and are resistant to UV light.

The outside-in flow configuration is tolerant of wide-ranging feed water qualities and allows air scour cleaning. The dead-end flow offers higher recovery and energy savings. The pressurized vertical shell-and-tube design eliminates the need for separate pressure vessels and allows easy removal of air from cleaning along with integrity testing steps.

The hollow fiber membranes are 1.3 mm outside diameter and 0.7 mm inside diameter and are made from PVDF polymer. The fibers are strong due to a combination of PVDF polymer, an asymmetric membrane with smaller pores in the active filtration area and a high porosity substructure. PVDF membranes offer high chemical resistance (e.g., resistance to chlorine) and are tolerant to temperatures of 40ºC.

The 0.03μm nominal pore size combines high filtration performance and high flux. The smaller pore size provides stabile long-term filtration performance compared to microfiltation.

Hollow Fiber Cross Section 
Hollow Fiber Cross Section

Featured Projects

Ultrafiltration modules and skids from Dow are the industry standard, with more than 900 proven ultrafiltration installations worldwide.  See for yourself the value they are delivering to customers in various regions by reviewing the featured projects below.  See our Resources page too, which has convenient filters to help you find the information you need.

Ultrafiltration News

Dow ultrafiltration technology is making waves around the world.   See the latest Dow ultrafiltration news below, and on the News & Events page.
  • DOW™ Ultrafiltration Technology Delivers Water Savings, Exceptional Bacteria Removal in New Haier Eco-Friendly Washing Machine – see full news story.
  • Dow and Veolia Will Deliver Ultrafiltration Technology for Total’s New Moho Nord Offshore Floating Production Unit (FPU) in West Africa – see full news story.

Water Solutions and Trends

Dow Water & Process Solutions has more than 70 years of experience in delivering innovative solutions to the marketplace. As a global leader in sustainable separation and purification technologies, including ultrafiltration, we are helping customers across industries and countries make real progress in ways that not only help improve productivity, efficiency and profitability, but also help reduce waste, energy consumption and environmental impact.  In addition, we are actively collaborating with industry, academia and customers to accelerate solutions to key challenges.

We are well positioned to meet your needs in every region of the world.  Learn more about water solutions and trends on our main website and via the information below. Also check out our resources page, which has convenient filters to help you find the information you need.




 

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