Advantages of EDI technology compared with hybrid ion exchange technology

Compared with mixed ion exchange technology, EDI technology has the following advantages

  1. Stable water quality
  2. Easy to realize fully automatic control
  3. No shutdown due to regeneration
  4. No need for chemical regeneration
  5. Low operating cost
  6. Small plant area
  7. No sewage discharge.

The history of the development of high-purity water treatment technology:

  • The first stage: pretreatment -> positive bed -> negative bed -> mixed bed
  • The second stage: pretreatment -> reverse osmosis -> mixed bed
  • The third stage: Pretreatment——>Reverse Osmosis——>EDI device

Reverse osmosis (RO) technology is a method that uses membrane separation to remove ions in water. Although the reverse osmosis system removes 95%-98% of ions in water, it still cannot meet the requirements of industrial production. The subsequent processes must use ion exchange equipment. . In recent decades, the mixed bed ion exchange technology has been the standard process for the preparation of pure water. Because it needs periodic regeneration and uses a lot of chemicals (acid and alkali) and pure water in the regeneration process, it is difficult to be satisfied with the acid-alkali-free pure water system.
Because traditional ion exchange has become increasingly unable to meet the needs of modern industry and environmental protection, the EDI technology that combines membrane and resin has become a revolution in water treatment technology. This technology uses electric regeneration ion exchange desalination process to replace the traditional mixed ion exchange desalination process DI. High desalination effect is achieved through ion exchange resin and selective ion membrane, and the combined process combined with reverse osmosis makes the water quality of 10~17M ΩCM high specification water produced.

Working principle of EDI technology:

  1. Water enters the EDI system, the main part flows into the resin/membrane, and the other part flows along the outside of the template to wash away the ions that penetrate the membrane.
  2. The resin intercepts the dissolved ions in the water.
  3. Under the action of the electrode, the trapped ions move the anions towards the positive electrode and the cations towards the negative electrode.
  4. Cations permeate through the cation membrane and drain out of the resin/membrane.
  5. Anions permeate the anion membrane and drain out of the resin/membrane.
  6. The concentrated ions are discharged from the waste water flow path.
  7. Non-ionized water flows out from the resin/membrane.

Water quality requirements for EDI device inlet water:

  • TEA (including CO2): <25mg/L
  • CaCO: 3
  • PH: 5-9
  • Hardness: <0.1mg/L
  • Silicon: <0.5mg/L
  • TOC: <0.5 mg/L
  • Residual chlorine: <0.05mg/L
  • Fe, Mn, H2S: <0.01 mg/L
  • Water inlet pressure: 30-100PSI
EDI water treatment plant

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