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Ultrapure Water with EDI: The Role of Post-RO Deionization

Compatibility of Electrodeionization (EDI) modules, which produce uninterrupted ultrapure water without the need for acid and caustic regeneration, with RO and deaerator.

Electrodeionization (EDI) is an advanced purification technology that continuously removes the trace amounts of ionic charge remaining in the permeate water exiting the reverse osmosis (RO) stage with the help of direct current (DC) electric field and selectively permeable ion exchange membrane/resin beds.

Unlike classical mixed-bed deionization columns, in EDI modules, resins are continuously regenerated during operation with H⁺ and OH⁻ ions formed by the electrical dissociation of water. Thus, continuous production is ensured without the need for hazardous acid (HCl/H₂SO₄) and caustic (NaOH) storage, neutralization and regeneration stops.

The EDI module should not be considered as a “final filter” on its own; Its performance and life directly depend on the quality of the feed water. Hardness, free chlorine, organic matter, iron and especially dissolved carbon dioxide (CO₂) directly affect EDI capacity.

EDI and Ultra Pure Water page of Elif Çevre Kimya includes an integrated configuration consisting of Double-Pass RO, membrane deaerator (for CO₂ removal) and EDI modules. Removing CO₂ gas before EDI both reduces electricity consumption and increases silica (SiO₂) and boron removal efficiency in the effluent.

Flat glass and mirror washing lines, high pressure steam boilers, power plants, pharmaceuticals, cosmetics and laboratory applications have different conductivity (<0.06 µS/cm / >16–18 MΩ·cm), TOC and silica expectations. Although the catalog includes a capacity range of 0.5–100 m³/hour, the exact system design is not committed without seeing the raw water analysis and point-of-use criteria.

What Does EDI Do After Reverse Osmosis?

Electrodeionization (EDI) is an advanced purification technology that continuously removes the trace amounts of ionic charge remaining in the permeate water exiting the reverse osmosis (RO) stage with the help of direct current (DC) electric field and selectively permeable ion exchange membrane/resin beds. Unlike classical mixed-bed deionization columns, in EDI modules, resins are continuously regenerated during operation with H⁺ and OH⁻ ions formed by the electrical dissociation of water. Thus, continuous production is ensured without the need for hazardous acid (HCl/H₂SO₄) and caustic (NaOH) storage, neutralization and regeneration stops.

Why Are Double Pass RO and Membrane Deaerator Critical?

The EDI module should not be considered a stand-alone “final filter”; Its performance and life directly depend on the quality of the feed water. Hardness, free chlorine, organic matter, iron and especially dissolved carbon dioxide (CO₂) directly affect the EDI capacity. Elif Çevre Kimya's EDI and Ultra Pure Water page includes an integrated configuration consisting of Double-Pass RO, membrane deaerator (for CO₂ removal) and EDI modules. Removing CO₂ gas before EDI both reduces electricity consumption and increases silica (SiO₂) and boron removal efficiency in the effluent.

Match Application and Capacity to Project

Flat glass and mirror washing lines, high pressure steam boilers, power plants, pharmaceuticals, cosmetics and laboratory applications have different conductivity (<0.06 µS/cm / >16–18 MΩ·cm), TOC and silica expectations. Although the catalog includes a capacity range of 0.5–100 m³/hour, the exact system design is not committed without seeing the raw water analysis and point-of-use criteria.

Field Control and Monitoring List

Chemical dosage and system capacity decisions should be determined by analysis and facility conditions; There is no guarantee of fixed dosage or performance.

  • Verification of total hardness (<1.0 ppm CaCO₃), free chlorine (<0.02 ppm) and SDI limits in EDI inlet water
  • Controlling the dissolved CO₂ load with a membrane deaerator and/or intermediate pH adjustment
  • Matching feedwater conductivity, silica (SiO₂) and organic carbon (TOC) values ​​to module limits
  • Online monitoring of DC rectifier current/voltage values ​​and EDI product water resistance (MΩ·cm)
  • Suitability of stainless steel (AISI 316L) or PVDF/PP pure water distribution line design to the point of use

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