EDI is the abbreviation of its English name electrodeionization. It is a new deep desalination process that organically combines electrodialysis and ion exchange technologies. It utilizes the ability of ion exchange for deep desalination to overcome the incomplete desalination defect of electrodialysis, and also uses the polarization-generated H+ and OH- on the surface of electrodialysis membranes and ion exchange resins under the action of an electric field, along with the selective permeability of electrodialysis membranes, to achieve automatic regeneration of ion exchange resins, overcoming the defect of requiring acid and alkali regeneration after resin failure. EDI is the product of the combination of ion exchange and electrodialysis technologies, so EDI possesses all the working characteristics of both ion exchange and electrodialysis during the desalination process.

The electrodeionization system includes the unit itself, chemical cleaning devices, auxiliary systems, supporting instruments, valves, piping systems, unit framework, and dosing equipment.         

The EDI unit is the key equipment for post-RO polishing treatment, and the EDI membrane element is the core component of the EDI unit. It is widely used in the preparation of electronic ultrapure water, industrial high-purity water, etc. It adopts a fully filled concentrate chamber, does not require salt addition or concentrate recirculation, produces water continuously without the need for shutdown regeneration, has a wider adaptation range, and offers superior performance.

Unit Design Requirements

● The electrodeionization unit adopts a frame design model and is supplied as a complete set. The unit is equipped with all modules, rectifiers, instruments, controls, piping, valves, etc., required to meet the effluent water quality and quantity requirements. The EDI unit operates fully automatically. The internal equipment and piping of the unit should be arranged aesthetically. The combination of components is determined based on factors such as water quality, recovery rate, and product water output.

● Valves shall be installed on the inlet and outlet main pipes of each unit of the device components. Sampling points shall be provided on the product water pipes and the inlet and drain pipes of the device components (a separate sampling point shall be established for the product water pipe of each device component). The number and location of sampling points should effectively diagnose and identify system defects. Sampling points shall be centrally located for easy access.

● The unit frame shall be equipped with all piping and fittings, including all supports, fasteners, clamps, etc. The combined frame of the electrodeionization unit should facilitate maintenance and disassembly. The design of the EDI unit combined frame shall meet the local seismic intensity requirements.

● Types and requirements of chemical cleaning solutions.

● Instruments, dosing metering pumps, and automatic valves in the electrodeionization unit shall use imported high-quality and reliable products. The system should be capable of automatic operation.

● Each EDI module shall be equipped with a completely independent DC power supply control box, ensuring that if any module overheats due to operational reasons, the power to that module is automatically cut off, while other modules in the system continue to operate normally.

● EDI does not generate chlorine gas or salt bridges during unit operation.

● The EDI rectifier device shall meet the requirements of relevant national technical standards and display current and voltage.

● The EDI unit adopts a modular assembly design for easy maintenance and replacement. Each EDI module has corresponding inlet and outlet pipes and valves, ensuring that if any module fails, it can be isolated while other modules in the system continue to operate normally. All components within the module are assembled at the factory before shipment.