Continuous electrodeionization CEDI

Electrodemineralization includes a number of subset technologies, including electrodialysis (ED), electrodialysis reversal (EDR), and electrodeionization (EDI). Electrodeionization is sometimes termed continuous electrodeionization (CEDI) or continuous deionization (CDI). 

In this chapter, the impact of other membrane technologies on the operation of RO systems is discussed. Technologies considered include microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) as pretreatment to RO, and continuous electrodeionization (CEDI) as post-treatment to RO. This chapter also describes the HERO (high efficiency RO—Debasish Mukhopadhyay patent holder, 1999) process used to generate high purity water from water that is difficult to treat, such as water containing high concentrations of silica. 

Continuous electrodeionization (CEDI—the continuous process subset of electrodeionization (EDI) that is sometimes referred to as... 

The process sequence employed to produce WPU grade water in the pharmaceutical industry typically comprises the following steps multimedia filtration, water softening, activated carbon filtration, prefiltration, UV disinfection, reverse osmosis, continuous electrodeionization (CEDI). For WFI, as mentioned earlier, the WPU water is subjected to a distillation process, and may be supplied hot if needed. 

Continuous electrodeionization systems can achieve 95% rejection of boron and silica, and 99+% rejection of sodium and chloride. This performance is possible due to voltage-induced dissociation of water that effectively regenerates a portion of the resin thereby allowing removal of weakly ionized species such as silica and boron.19 In fact, the boron in the effluent from a CEDI system can be lower than that in the effluent from a mixed-bed ion exchange system.13... 

Continuous electrodeionization is primarily used as an alternative to ion exchange. Because of the extensive pretreatment required by CEDI systems, the technology has grown into a polisher for RO (see Figure 16.18). Continuous deionization can achieve mixed-bed water quality of RO permeate without the need to store and... 

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