Operating procedure of the EDI water purification equipment module

The EDI water purification equipment module refers to the process of removing ions from water using ion exchange membranes and ion exchange resins under the action of a direct current electric field.

Most EDI module products on the market today consist of alternately placed cation and anion membranes, with water flowing through the membrane gaps. These alternately placed anion and cation exchange membranes are fixed between two devices with inlets and outlets, and water flows through the gaps between the membranes. The anion membrane facing the positive electrode and the cation membrane facing the negative electrode constitute a concentrate chamber, and the anion membrane facing the negative electrode and the cation membrane facing the positive electrode constitute a freshwater chamber. To facilitate the intensification of the ion exchange process in weak electrolyte solutions, ion exchange resins are sometimes added to the freshwater chamber and sometimes to the concentrate chamber. The electrodes at both ends of the EDI module device rack provide a transverse direct current electric field, which drives the movement of ions in the water through the ion exchange membranes. This achieves a reduction in ion concentration in the freshwater chamber and an increase in ion concentration in the concentrate chamber.

1. Initial Startup
　Before starting the EDI system, the RO system, EDI module installation, instrument calibration, and other system checks should have been completed. The following is the recommended EDI system startup procedure;
2. EDI Startup Procedure
　　Before connecting the piping to the EDI, please confirm that all upstream pretreatment equipment and piping meet the cleanliness requirements. Ensure that all piping connected to the EDI module is correctly connected and meets the cleanliness requirements.
　　Check that all relevant manual valves are in the correct position and open/closed status. The inlet valve, product water valve, ultrapure water tank inlet valve, and concentrate water flow control valve are fully open. During the flushing process, check all pipe connections and valves to ensure there are no leaks. Tighten the connections if necessary.
　　Confirm that the wiring from the EDI module to the power supply module is correct.
　　Start the RO product water transfer pump. Adjust the valve opening to the design flow rate and design pressure. Check the design recovery rate and the actual recovery rate. Continuously monitor the system pressure while ensuring that the system operating pressure does not exceed the module's high operating pressure limit.
　　At the design flow rate, adjust the valve until the product water pressure is higher than the concentrate water discharge pressure. Repeat the above steps until the system operation meets the design product water volume and concentrate water flow rate. Calculate the system recovery rate and compare it with the design value.
　　Turn on the module power switch and slowly adjust the DC power supply on the display panel to the required value. Observe the effluent water quality. Record all operating data.
　　Test all flow limit switches and related interlocks. Ensure that the EDI power supply module is de-energized when the concentrate water circulation flow is insufficient.
　　Continue to keep the CEDI in circulation until the product water indicators meet the requirements. Once the EDI effluent indicators meet the standards, open the EDI product water valve (to the downstream tank) and close the EDI product water return valve (to the RO tank). Confirm again that the product water pressure is higher than the concentrate water discharge pressure. Compare the system operating values with the design values; after the system operation stabilizes (water quality and flow rate), record the operating data in the daily operating data record table. Select the automatic mode for the operating mode.
　　During the first week of system operation, regularly check the system's operation to ensure normal and reliable operation.

3. Running Startup
　　Once the EDI system has started (in fact, the EDI system will inevitably experience more or less shutdown and restart). Each shutdown and restart means changes in pressure and flow rate, as well as mechanical impact on the EDI module. Therefore, the number of system shutdowns and restarts should be minimized to ensure stable operation of the EDI system.
　　Checks before and during system startup should be performed as a daily task, and work records should be kept. Instrument calibration, alarms, safety equipment, and pipe leak checks should also be performed as a daily task.

4. Shutdown
　　Adjust the current and voltage to 0 and turn off the power supply of the EDI module.
　　Stop the reverse osmosis product water transfer pump.
　　Close the inlet valve of each EDI module.
Close the isolation valve of the EDI module

5. Restarting the System After Shutdown
　　Set the EDI system valve operating status to EDI circulation status;
　　Start the reverse osmosis product water transfer pump;
　　Check each item according to the EDI startup procedure and start the EDI system;