TEP Fouling in RO Membranes

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We have a transparent exopolymer particles (TEP) fouling problem in our reverse osmosis (RO) membranes.

Our pretreatment includes dissolved air flotation (DAF) and ultrafiltration (UF).

Turbidity and silt density index (SDI) is normal in RO feed water but fouling still occurs.

How can we prevent TEP fouling in RO membranes?

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5 Answers

  1. TEP fouling is normal in Plants fitted with MF / UF

    If in addition you have an intermediate tank between UF and cartridge filters the situation is still worse.

    Sometimes Plants with UF are designed without cartridge filters (Big error) and naturally RO membranes are fouled more heavily.

    UF is not the correct pretreatment for RO, unless water temperature is very low. (Sand filters should be used instead.)

    Cartridge filters last 6 months with sand filters and 1-2 months with UF

    CIPs are performed once a year with sand filters and  4 to 12 times with UF

    What to do?

    Very little, you cannot retrofit to sand filters. (Too late)

    1) Keep intermediate tank as clean as possible with frequent manual cleanings and biocides.

    2) Install cartridge filters if they are not fitted

    3) Perform good CIPs ( pH : 12,5 - 13  and 12 hours time minimum (Full time, no stand byes) 

    4) Install membranes with 34 mills spacers in position 1 and 2

    5) Retrofit to hybrid membrane staging.  (Install membranes with a lower production in positions 1, 2 and 3.) 

    6) Next time, design with sand filters

    Regards

    Talavera

  2. Hello Tahir,


    SDI does not have any relation with fouling potential. If you want to measure fouling potential, better use the MFI method, Modified Fouling Index. Suggest you to contact Akvoregia for more and detailed information their MFI Forecaster and the topic of TEP. With their instrument you can also assess effectiveness of your pretreatment process.  Alos a prediction of fouling potential of feedwater before RO systems is easy and possible. When you know the fouling potential, you can adjust your process ( more or less backwashes), which leads to better performance, of your system. Also corrupt pretreatment systems can be determined. TEP will always occur in your water, but you get better control over your process. Send email to me if you need more info. Best regards, Roemer

  3. ON RO OPERATION DOSE 3PPM ANTISCALANT/PER LITER.

    NOTE:IF SILICA IS MORE THAN 100PPM YOU HAVE TO DO JAR TEST FOR SILICA.

     

    REGARDS

    ABDUL GAFFAR - SENIOR CHEMIST.

  4. Hey Tahir, we have good experience with our HFs Membrane, having a MWCO of 10 kdA to avoid TEP fouling. Have a look at xflow.pentair.com and find more about this product and others.

    Which UF are you using as pretreatment?

  5. Hi Tahir,

    Our NanoCeram electropositive water filters are quite efficient in reducing TEP from salt water sources. The electroadsorptive characteristics of the nanoalumina fibers in our patented nonwoven filter media use a very strong (+50mv) positive charge to attract, capture and retain TEP. If interested, I can send you a report on the independent study.

    Regards,

    Henry Frank

    1 Comment

    1. Hi Tahir

      Please get in ouch with Dryden Aqua, Scotland for their Active Filtration media will help solve the issue is my opinion.