RO fouling

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New membrane’s feed pressure increased but DP stays same .Second stage  feed pressure also increased , raw water is treated sewage , is is organic fouling and tried cleaning with Caustic but not helped . Any suggestions? 

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5 Answers

  1. Second stage feed pressure increase tells me there maybe a issue with scaling (chemical fouling) in the membranes (besides organic/colloidal fouling in first stage), so check your anti-scalant and/or acid dosing rates & concentrations. Also try to lower the conversion to see if any difference. You report DP is not increasing but how do you measure it? Do NOT take the difference between feed pressure and reject pressure - need to measure the pressure differential across the membranes ON LY (no piping/valve, etc. pressure drops). Finally I suggest you remove one membrane from first stage and one from second stage and do an autopsy to see what you got!

  2. it may be an issue of insufficient settling time, and or insufficient airation. You may also check for heavy metal salt impurities which can affect ionization.

       
       
       

     

    1 Comment

    1. If it is scaling , the second stage DP should increase , but stays same . So thought of organic fouling , since it is treated sewage , RO inlet . 

  3. In used water there is water and impurities. the cleaning of used water must therefore consist of cleaning the water of these impurities. Filtration is just a separation process that does not clean the water, it only retains what it is programmed for whether it is sandy soil filtration or nano filtration. It only extracts part of the suspended matter impurities, it has no action of cleaning the water of diluted, dissolved impurities such as urine and all other bio-chemical, chemical, acidic components. , detergents, pharmaceuticals. Filtration, whatever it is, is always subject to clogging, which the management operator must avoid at all costs.

    Filtration is the only tool currently in use in the management of used water that necessarily requires expensive, polluting alternative solutions, which in addition give the same problem: the residual.

    the major drawback of this management of used water is the deterioration of the environment. organic matter putrefies to the stage of putrid. this deterioration interferes with all the other components present. The final deterioration generates hydrogen sulfide which insusceptibly forms poisonous gas, fatally suffocating anyone who inhales it.

    one can imagine the damage caused by this toxic gas when it is released into the environment, mainly in surface aquatic environments, causing all of humanity to slowly poison itself by drinking this poison every day.

    A biotechnology cleans water from wastewater with a cleaning performance of more than 98% of total and definitive destruction of suspended organic matter.

     

  4. and what about permeate's flow and conductivity? Do you normalize data?

    1 Comment

    1. Permeate flow reduced for the same feed pressure , conductivity same . Not changed much . 

  5. How do micro- and ultra-filtration installed upstream of reverse osmosis behave?
    If well functioning, they should avoid this problem at RO.

    What do you mean by “cleaning with caustic”? Backwash?

    2 Comments

    1. Cleaning with Caustic means not backwash , CIP . Clean in place . Soaking and recirculation . 

      1 Comment reply

      1. The concept of CIP is clear to me but one thing I still don't understand: how often is a backwash of the membranes performed or is it never scheduled?
        Have you changed membrane types and/or working pressures?

    2. Have upstream sand filtration as well as ultrafiltration . And TSS downstream is zero and Turbidity below 0.5 NTU . 

      1 Comment reply