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Tubular Membranes in Industrial Wastewater Filtration Systems & Technologies

The industrialized world has long been addressing the issue of managing wastewater with varying degrees of success. Over the decades, a multitude of wastewater processing and treatment systems have been developed with the goal of capturing various toxic and or otherwise undesirable manufacturing byproducts prior to discharge or filtering water for reuse.

Traditional treatment systems include chemical treatments followed by filtration and separation technologies such as sedimentation tanks (clarifiers), sand/media filters, various microfiltration (MF) and ultrafiltration technologies (UF), such as hollow fiber and reverse osmosis (RO) systems, to name a few. 

MF is a low-pressure (0.7 – 7 bar, 10 – 100 psi) membrane process for separation of particulate from water down to sub-micron and colloidal size, 0.1 to 0.05µ. MF is often used upstream of RO systems that are employed to remove soluble materials from feed water. UF is also a low-pressure solids separation process with filtration efficiencies in the 0.01 – 0.1µ size range.

Tubular Membranes for Cross Flow Filtration

Tubular Cross Flow Filtration is an industrial wastewater filtration technology that is available for both MF and UF systems. In this process, treated wastewater is passed through the bore of membrane filtration tubes under pressure at sufficient speed to prevent cake formation.

Clear liquid permeate is driven through the membrane pores while the solids pass through the inside of the tubes and are progressively concentrated into a slurry after several passes through the tubes. Slurry is continuously drawn off from the system for dewatering while freshly treated wastewater is introduced into the system.

 This technology has been used for over 20 years and offers many advantages, including:

  • Compact dimensions
  • High quality liquid output
  • Mechanical robustness
  • High chemical resistance

This chemical resistance allows very strong acids, alkalis, oxidants, etc. to be used for chemical clean-in-place (CIP) procedures.

Tubular Cross-flow Filtration Process

TMF and Cross Flow Filtration Membrane Technology

Filtration membranes are permeable materials with tightly controlled pore sizes that are available in a variety of polymers and filtration ratings. Advantages of these polymeric membrane materials include varying degrees of mechanical robustness and resistance to chemical attack. When these permeable membranes are applied to a tube substrate the resulting product is a tubular membrane filter, or TMF™.

PVDF is a polymer that offers a high level of robustness and chemical resistance, especially when available as a pure polymer formulation.

PVDF membranes may be available as alloys derived from multiple polymers, such as PVDF with PVP, but these alloys may not offer as high a degree of chemical resistance over the life of the membrane as compared with 100% PVDF membranes.

The POREX® Filtration membrane is a 100% unalloyed PVDF polymer offering optimum chemical resistance.

Porex Filtration PVDF Polymers

Casting Membranes onto Tubular Substrates

There are varying methods for applying the polymeric membrane to the tube substrate. One method is to laminate the membrane to the surface (only) of the substrate tube resulting in a laminated composite material.

Another method is to anchor the membrane directly into the substrate material also resulting in a composite material.

Porex Filtration has developed a unique manufacturing technology where the membrane is cast throughout the wall of the substrate tube, solidly anchoring the membrane into the substrate.

This technology results in a cross flow tubular membrane filter (TMF) that will not delaminate, yet allows for optimal flow of permeate through the tube filter, supports hydraulic back pulse cleaning, exhibits outstanding chemical resistance, and offers long service life.

Laminated Composite Membranes

Tubular Membrane Tube Lumen with Lamincated PVDF Membrane

Anchored Composite Membranes

Tubular Membrane Tube Lumen with Anchored Membrane Anchored PVDF Membrane for Tubular Membrane Filtration 

 

Unique Surface Topography

The POREX® TMF™ membrane casting process was engineered to produce a unique “peaks and valleys” lumen topography. The porous PE substrate peaks protect the PVDF membrane surface in the valleys from highly abrasive feed waters, such as those containing high concentrations of sharp silicon cuttings produced by semiconductor grinding and cutting processes.

Porex Filtration Semiconductor Grinding and Cutting Porex Filtration Tubular Membrane

 

Porex Filtration Tubular Membranes

Porex TMF products utilize a PVDF membrane casting technology that anchors the membrane to a PE or PVDF substrate tube. Porex TMF membrane filters are available in 0.1, 0.05, and 0.02 micron pore sizes. Porex utilizes a unique membrane casting process that offers the following advantages:

  • Produces high water recovery rates
  • Will not delaminate (even under high pressure)
  • 100% PVDF membrane
  • Supports pulse backwashing
  • Supports CIP
  • High chemical inertness
  • Full pH tolerance (1 – 14)
  • Highly abrasive resistant (semiconductor - wafer grinding processing)
  • Small system footprint
  • Long service life

 

 

 

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