WaterSolutions DOW Ultrafiltration

What is UF?

Ultrafiltration or UF is a pressure driven membrane separation process that separates particulate matter from soluble components in the carrier fluid (such as water). UF membranes typically have pore sizes in the range of 0.01 - 0.10 µm and have a high removal capability for bacteria and most viruses, colloids and silt (SDI). The smaller the nominal pore size, the higher the removal capability. Most materials that are used in UF are polymeric and are naturally hydrophobic. Common polymeric materials used in UF include: Polysulfone (PS), Polyethersulfone (PES), Polypropylene (PP), or Polyvinylidenefluoride (PVDF). Although these materials can be blended with hydrophilic agents, they can reduce the membranes ability to be cleaned with high strength disinfectants such as hypochlorite that impacts removal of bacterial growth.

The DOW™ Ultrafiltration module utilizes a double-walled hollow fiber (capillary) PVDF membrane which has a very small nominal pore diameter for PVDF material that allows for the removal of all particulate matter, bacteria and most viruses and colloids. Despite the small pore diameter, the membrane has a very high porosity resulting in a flux similar to that of micro-filtration (MF) and can effectively replace MF in most cases.

Systems designed with DOW Ultrafiltration use an outside-in flow configuration which allows for less plugging, higher solids loading, higher flow area and easy cleaning. The primary flow design is dead-end filtration but the module can be operated using a concentrate bleed. Dead-end filtration uses less energy and has a lower operating pressure than the concentrate bleed, therefore reducing operating costs.

Typically, DOW Ultrafiltration is operated at a constant permeate flow. The transmembrane pressure (TMP) will naturally increase over time and the module can be cleaned periodically by back flushing and air scouring to remove the fouling layer. Disinfectants and other cleaning agents can be used to fully remove and prevent performance loss due to biological growth as well as other foulants.
 

DOW™ Ultrafiltration Technology

The DOW™ Ultrafiltration double-walled hollow fiber membrane is formed from high grade polymeric chemicals. The virtually defect-free, double-walled fiber membrane is much more robust and less prone to breakage than single-wall hollow fibers but due to the high pore distribution, does not compromise flux. The uniformity of pore size and outside-in flow ensures the DOW™ Ultrafiltration membrane creates a perfect barrier without sacrificing performance.

DOW™ Ultrafiltration Advantages

• Low fouling Hydrophilic Polyvinylidenefluoride (H-PVDF) membrane
• Excellent filtration performance with high flux
• Durable and break resistant double- walled fiber structure
• High chemical resistance and temperature tolerance for effective membrane cleaning
• Very fine nominal pore diameter (0.03 µm)
• High removal efficiency of bacteria and viruses
• Dead-end or concentrate bleed flow capabilities
• Outside-In flow configuration that allows for less plugging and higher solids loading, higher flow area and easier cleaning
• Can be periodically back washed and air scoured to improve performance and extend operating life by removing the fouling layer
• Simple, vertical, modular design allows low cost, compact systems

 Ready-to-assemble DOW IntegraPac™ skids are pre-engineered — direct-connect ultrafiltration (UF) modules — that reduce material costs, lower freight costs and enable faster assembly. This revolutionary UF solution dramatically simplifies the process of incorporating DOW Ultrafiltration technology into water treatment systems.