• SED - Selective ElectroDialysis
    For multivalent/monovalent ion separation from water/waste streams.
    Membranes: standard grade, monovalent grade homogeneous anion and cation exchange membranes


    How does it work?
    Selective ElectroDialysis (SED) is a DC voltage-driven membrane process. An electrical potential is used to move (ions) salts through a membrane

    SED like ED depends on the following general principles: Most salts dissolved in water are ions, either positively charged (cations), or negatively charged (anions). Since two identical charged poles repel each other and two opposite poles attract, the ions migrate toward the electrodes with an opposite electric charge.

    monovalentgradeiemSuitable membranes can be constructed to permit selective passage of either anions or cations. In a saline solution, dissolved ions such as sodium (+) and chloride (-) migrate to the opposite electrodes passing through selected membranes that either allow cations or anions to pass through (not both).

    Membranes are usually arranged in an alternate pattern, with anion-selective membrane followed by a cation-selective membrane. During this process, the salt content of the water channel is diluted, while concentrated solutions are formed on the other side of the membrane. Concentrated and diluted solutions are created in the spaces between the alternating membranes, and these spaces bound by two membranes are called cell pairs. An ED units consist of several hundred cells bound together with electrodes, and is referred to as a stack. Feed water passes through all the cells simultaneously to provide a continuous flow of desalinated water and a steady stream of concentrate (brine) from the stack.

    ED and EDR are processes in which ions move through a semi-permeable membrane under the influence of an electrical current. In an EDR system the polarity, and by this the product and concentrate compartments, are reversed periodically in order to prevent scaling of the membranes.

    The difference between ED and SED is made via the use of monovalent membranes which reject multivalent ions to pass through the membrane.
    Typically multivalent ions like sulphates, carbonates, phosphates tend to move faster through standard grade membranes than monovalent ions like nitrates. By using monovalent membranes the multivalent ions are being blocked, resulting in an overall lower energy consumption, faster desalination / concentration rate and specific monovalent/multivalent ion separation.

    SED uses the same EDR module configuration while making using of standard grade (AEM, CEM) and monovalent grades (AEM mono, CEM mono) membranes.

    Depending on the application requirements one can choose for the following configurations:

    • Standard grade AEM + mono valent grade CEM
    • Monovalent grade AEM + standard grade CEM
    • Monovalent grade AEM + monovalent grade CEM


    • Nitrate removal from ground water
    • Ammonia removal
    • Sodium removal

    Water recovery from manure via selective ED technology using Fujifilm membranes. You can read more about this in the brochure: