Municipal water → raw water tank → raw water pump → quartz sand filter → activated carbon filter → security filter → a booster pump → a RO reverse osmosis → middle tank → secondary booster pump → secondary RO reverse osmosis → pure Water tank → pure water pump → 0.45μ precision filter → TOC removal device → EDI device → resistivity meter → polished mixed bed → 0.22μ precision filter → resistivity meter → washing machine;

EDI working principle

EDI is removed by exchanging residual salts of RO water with hydrogen ions or hydroxide ions and sending them to the concentrated water stream. The exchange reaction is carried out in the purification chamber of the membrane, where the anion exchange resin uses their hydroxide ions (OH-) to exchange the anions (such as chloride ion Cl-) in the dissolved salt. Correspondingly, the cation exchange resin uses their hydrogen ions (H +) to exchange the cations (such as Na +) in the dissolved salt. A direct current field is applied between the anode (+) and the cathode (-) located at both ends of the membrane block. The potential causes the ions exchanged on the resin to migrate along the surface of the resin particles and enter the concentrated water chamber through the membrane. The anodes attract negative ions (such as Cl-, OH-), which pass through the anion selective membrane into the adjacent concentrated water stream and are blocked by the cation selective membrane, leaving the concentrated water stream. The cathode attracts the cations in the concentrated water stream (eg Na +, H +). These ions pass through the cation selective membrane into the adjacent concentrated water stream and are blocked by the anion selective membrane, leaving the concentrated water stream. When water flows through these two parallel chambers, the ions are removed in the pure water chamber and gathered in the adjacent concentrated water stream, which is then removed from the membrane by the concentrated water stream.

The use of ion exchange resins in pure water and concentrated water is the key to EDI technology. An important phenomenon occurs in the ion exchange resin of a pure water chamber. In the local area where the potential difference is high, the electrochemical reaction decomposes the water to produce a large amount of H and OH. The production of local H and OH in the self-exchange resin of the mixed bed allows the resin and membrane to be continuously regenerated without the addition of chemicals.

Major economic and technical indicators

     1, pretreatment flow ≥2.5T / H;
     2, a reverse osmosis water ≥ 1.5T / H;
     3, two reverse osmosis water ≥ 1T / H;
     4, a reverse osmosis conductivity ≤ 15μs / cm;
     5, two reverse osmosis conductivity ≤ 10μs / cm;
     6, EDI production of water resistivity ≥ 14MΩ · CM;
     7, polished mixed bed water resistance ≥ 17MΩ · CM (using nuclear grade resin) (built-in 25L, per liter of water can produce 35-50 tons);
     8, EDI production of water flow ≥ 1000L / H;
     9, a reverse osmosis water use rate ≥ 65%;
     10, two reverse osmosis water use rate ≥85%;
     11, EDI water utilization ≥ 90%;
     12, EDI life: 3-5 years (when the water quality, water does not meet the standards need to clean the membrane block.