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

The control methods for the inlet water quality indicators of EDI ultra pure water system are as follows:

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

2. Control of working voltage current. The system should choose 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 structure. In order to ionize a certain amount of water and 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 to adjust the pH before RO to maximize CO2 removal, and CO2 can also be removed by degassing towers and membranes.

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

5. Control of TOC. Combined 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 inlet control of RO systems, and qualified RO effluent can generally meet the inlet requirements of EDI.

7. Control of Fe. During operation, control the Fe content of EDI inlet to be lower than 0.01mg/L. If the resin has already experienced "poisoning", acid solution can be used for resuscitation treatment, which has a better effect.

The characteristics and advantages of EDI

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

1. The EDI system does not require the use of acid-base solutions for resin regeneration, avoiding wastewater pollution caused by regeneration. Meanwhile, 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.

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