• What are the main foulants on the membrane surface ?
    1.Organic, colloidal and particulate fouling.
    3.Bacterial and microbial fouling.
  • Colloids and particulate matter on the membrane surface can seriously affect the performance of the membranes. What are the typical observations?
    Feed pressure increase.
    Permeate flow decline.
    Pressured drop increase.
    Cleaning is not restoring the performance decline.
  • What are the symptoms of a membrane system experiencing biofouling?
    Pressure drop increase.
    Permeate flow decline.
    Feed pressure increase.
    Salt passage is the same or worse.
  • How to avoid or minimize membrane fouling?
    Use pretreatment equipment (such as UF, MMF, prefilters).
    Apply effective pretreatment chemicals (coagulant, flocculant, biocides, antiscalants) to improve the efficacy of the pretreatment and RO/NF system.
    Membrane cleaning should be carried out if there is 10% drop in normalized permeate flow, 10% increase in normalized salt passage or a 15% pressure drop increase.
  • What kind of corrosion is observed in water recirculation systems?
    Uniform or general Corrosion
    Galvanic Corrosion
    Crevice Corrosion
    Intergranular Corrosion
    Selective Corrosion
    Impingement Attack
    Stress Corrosion
    Corrosion Fatigue
  • What is the simple qualitative method to determine the composition of the scale?

    It is simple to judge the main composition of the scale in the circulating water system by using the acid solution method.

    Main components of scale                                 The apperance of acid dissolved by acid

    Carbonate scale                            After adding acid, large number of bubbles are formed.

    Silicate scale                                Slowly dissolved in hot HCl and HNO, produces white insoluble deposit.

    Iron oxide scale                           Dissolve with HNO, it generates a yellow solution.

    Copper scale                                Dissolve with HNO3 , it generates blue and yellowish green solutions.

    Phosphate scale                         The solution with ammonium molybdate plus HNO3 generates  a yellow precipitate.

                                                         Then adding ammonia to this deposit:  phosphate scale is formed.