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This section answers frequently asked questions.
Select a topic below.
For further information, see Contact Us About Products and Technology.

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General Questions

  • What is MBR (Membrane Bioreactor) ?
    It is a wastewater treatment process that combines activated sludge treatment with membrane separation.
    Instead of directly filtering the wastewater (influent), the organic matter in the influent is decomposed by activated sludge (microorganisms), and the solid-liquid separation of the activated sludge is achieved using membranes.
    MBR has several advantages compared to conventional activated sludge processes, including "clear treated water," "space-saving," and "simple flow and easy operation and management."
  • What is the advantages of membrane treatment?
    Clear treated water, without suspended solids (SS) and pathogenic E. coli, is achievable.
    Compared to treatments such as sedimentation tanks and sand filtration, the treated water from membrane treatment is clear.
    By utilizing membrane treatment for water treatment and wastewater reuse, it is possible to save on water and sewage charges.
  • What types of membranes are used for water treatment?
    Membranes are classified based on their pore size into MF membranes (microfiltration membranes), UF membranes (ultrafiltration membranes), NF membranes (nanofiltration membranes), and RO membranes (reverse osmosis membranes).
    PoreflonTM membranes are classified as either MF or UF membranes.
  • What is a hollow fiber membrane?
    It is a membrane that has a hollow, straw-like structure and contains numerous tiny pores on its surface.
    The separation process occurs on the walls of these tiny pores. It is characterized by its ability to have a large membrane surface area per unit volume (high packing density), allowing for more compact equipment design in membrane processes.

Operating Conditions

  • What aeration rate should I use for membrane scouring?
    For a pressurized module: 200 L/min per module
    For a submerged cassette-type module: 100-150 L/min per module
    For a submerged square-type module: 50-90 L/min per module
  • What is the upper limit of TSS in raw water?
    For MBR, the recommended value is a MLSS concentration of less than 12,000 mg/L.
    For a pressurized type, less than 100 mg/L.
  • What is the upper limit for oil contained in raw water?
    It is confirmed that the removal rate is 99% or more for oil contained feed water at a level of approximately 800 mg/L
  • What chemicals can I use for cleaning?
    A mixture of NaOH and NaOCl is effective for organic fouling. Use an acid (sulfuric, hydrochloric, citric, etc.) for inorganic fouling. The POREFLON Membrane Module has excellent chemical resistance and can be used with solutions ranging widely from pH 0 to 14. It is recommended to make preliminary tests to find out right type of chemical and its optimum concentration.
  • When does the membrane module require cleaning?
    Periodical cleaning is recommended to ensure stable operations. (The cleaning frequency depends on the water quality.)
    Also perform cleaning when the transmembrane pressure (TMP) starts to sharply increase or to reach approximately 60 kPa for pressurizes membrane, 40 kPa for submerged membrane modules.
  • How much cleaning chemicals should I use?
    This varies depending on the cleaning frequency and concentration of chemical used for cleaning. Contact us for details. The POREFLON Membrane Module enables use of a high-concentration chemical and exhibits high recovery performance.
  • Do I need to perform backwashing?
    In the case of pressurized membrane modules, it is recommended to perform backwashing on a regular basis.
    When submerged membrane modules are in the MBR for municipal wastewater, the membrane modules can operate without backwash.

Maintenance and Storage

  • Are the hollow fibers likely to break during use?
    The hollow fiber membranes used in the POREFLON Membrane Module are exceptionally strong, and are not broken during normal operation.
  • How should I store the POREFLON Membrane Module?
    The POREFLON Membrane Module has long-lasting hydrophilic properties compared to membranes made of other materials, so you can store it dry.
    (You may also be able to store it dry during or after use. Please contract us for details.)
  • How long will the membrane last?
    The membrane is robust enough for a service of more then 10 years. However, the service life depends on the operating conditions. Please contact us for warranty information.


  • Can you supply a packaged membrane treatment system?
    Yes, Sumitomo can propose a membrane treatment system that is best suited to your required water quality and volume needs.
  • Do you sell membrane modules alone?
    Yes, membrane modules alone are available.
  • Can I receive service after purchasing a membrane treatment system?
    Sumitomo offers a variety of services to maintain your membrane treatment system. (Available for a fee.)
  • What are the specific uses for pressurized and submerged membrane modules?
    In general , select module type according to the turbidity of the raw water.
    Pressurized membrane modules are suitable for low-turbidity water while submerged membrane modules are used for high-turbidity water.
  • Can I use the membrane module to produce drinking water?
    Yes, you can. The POREFLON Membrane Module has been authorized by the Association of Membrane Separation Technology of Japan (AMST). If you use the POREFLON Membrane Module to produce drinking water, please refer to the regulation of each country.