Control Measures for Inlet Water Quality Index of EDI Ultrapure Water System

The control measures for the inflow water quality indicators of EDI ultra-pure water system are as follows:

1. Control of inlet water conductivity. Control the conductivity during the pre-treatment process so that the EDI inlet conductivity is less than 40 μ S/cm can ensure that the conductivity of the effluent is qualified and weak electrolyte is removed.

Control of working voltage and current. The system should select an appropriate operating voltage current during operation. At the same time, there is a limit voltage current point position on the voltage current curve of EDI water purification equipment, which is related to factors such as influent water quality, membrane and resin performance, and membrane pair structure. In order to ionize a certain amount of water to generate sufficient amounts of H+and OH - ions to regenerate a certain amount of ion exchange resin, the voltage current operating point of the selected EDI water purification equipment must be greater than the limit voltage current point.

3. Control of influent CO2. Alkali can be added before RO to adjust pH to maximize CO2 removal, and degassing towers and membranes can also be used to remove CO2.

4. Control of inlet water hardness. It can be combined with CO2 removal to soften and add alkali to RO influent water. When the salt content of the influent water is high, a primary RO or nanofiltration can be added in combination with desalination.

5 Control of TOC. In combination with other indicator requirements, add a level of RO to meet the requirements.

6. Control of turbidity and pollution index. Turbidity and pollution index are one of the main indicators for the inflow control of the RO system, and qualified RO effluent can generally meet the inflow requirements of EDI.

Control of 7Fe. During operation, control the Fe content of EDI inlet water to be lower than 0.01 mg/L. If "poisoning" has occurred to the resin, acid solution can be used for resuscitation treatment, with better results.

Characteristics and advantages of EDI

The biggest characteristic of EDI technology is to replace the chemical regeneration of ion exchange resins with electric fields and ion membranes, making RO+EDI pure water systems have significant advantages over RO+mixed beds in terms of equipment structure, usage, and operating costs. And overcomes the problem of wastewater discharge caused by regenerated resin.

The EDI system does not require the use of acid and alkali solutions to regenerate the resin, avoiding wastewater pollution caused by regeneration. At the same time, the concentrated water discharged by EDI can be directly reused before RO, so that the EDI unit can achieve no wastewater discharge and no secondary pollution.

EDI does not use acid and alkali regeneration resin, simplifying the equipment structure of the pure water system, saving investment, simplifying operation, and reducing operating costs.