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Electrodeionization (EDI) system is a scientific water treatment technology that purifies water by directing the movement of dielectric ions in the water through a separator under the action of a direct current electric field, and utilizing the selective permeation of ions by an exchange membrane. Between a pair of electrodes in an electrodialysis device, there are usually multiple sets of alternating arrangements of cathode membrane, anode membrane, and separator (A, B), forming a concentration chamber and a depletion chamber (i.e. cations can pass through the anode membrane, anions can pass through the cathode membrane). Cations in the dilute water migrate to the negative electrode through the cation membrane and are intercepted by the anion membrane in the concentrated chamber; The anions in the water migrate towards the positive electrode direction and are intercepted by the positive membrane in the concentration chamber. As a result, the number of ions in the water passing through the dilution chamber gradually decreases, becoming fresh water. In the concentration chamber, due to the continuous influx of anions and cations, the concentration of dielectric ions continues to increase, becoming concentrated water, thus achieving the purpose of desalination, purification, concentration or refinement.

At the same operating current, as the conductivity of the raw water increases, the removal rate of weak electrolytes by EDI decreases, and the conductivity of the effluent also increases. If the conductivity of the raw water is low, the ion content is also low, and the low concentration of ions causes a large electromotive force gradient to form on the surface of the resin and membrane in the dilution chamber, leading to an increase in the degree of water dissociation, an increase in the limit current, and a larger amount of H+and OH - produced, resulting in a good regeneration effect of the anion and cation exchange resin filled in the dilution chamber.

Jinan water treatment equipment is small in size, easy to install, and can be used unattended for a long time.

The working current increases, and the quality of the produced water continues to improve. But if the current is increased after reaching the highest point, due to the excessive amount of H+and OH - ions generated by water ionization, a large number of surplus ions act as current carrying ions for conduction, in addition to being used for regenerating resins. At the same time, due to the accumulation and blockage of a large number of current carrying ions during their movement, even counter diffusion occurs, resulting in a decrease in the quality of the produced water.
The impact of turbidity and pollution index (SDI). The EDI component's water production channel is filled with ion exchange resin. Excessive turbidity and pollution index can cause channel blockage, resulting in an increase in system pressure difference and a decrease in water production.

Jinan Water Treatment Equipment

The influence of hardness. If the residual hardness of the incoming water in EDI is too high, it will cause scaling on the membrane surface of the concentrated water channel, reduce the flow rate of concentrated water, and decrease the resistivity of the produced water; Affects the quality of the produced water, and in severe cases, it can block the concentrated water and extreme water channels of the components, causing damage to the components due to internal heating.
The impact of Total Organic Carbon (TOC). If the organic content in the influent is too high, it will cause organic pollution of the resin and selective permeable membrane, leading to an increase in system operating voltage and a decrease in the quality of the produced water. At the same time, it is also easy to form organic colloids in the concentrated water channel, which can block the channel.

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The impact of CO2 in the inflow. The HCO3- generated by CO2 in the inflow is a weak electrolyte that can easily penetrate the ion exchange resin layer and cause a decrease in the quality of the produced water.
The influence of total anion content (TEA). A high TEA will reduce the resistivity of EDI water production or require an increase in EDI operating current, while excessively high operating current will lead to an increase in system current and residual chlorine concentration in the polar water, which is detrimental to the lifespan of the polar membrane.