ISO 20468-6-2021 pdf download.Guidelines for performance evaluation of treatment technologies for water reuse systems – Part 6: Ion exchange and electrodialysis. 4.3.2.1 Batch method This method circulates raw water between electrodialyser and tank. The batch method, with replacement of solution but needing work, is used in the case of small-scale, high salt rejection. 4.3.2.2 One-pass method This method treats raw water with one continuous pass. This method, because of continuous operation, is easy to control operationally. Changes in raw water affect the quality of product water. 4.3.2.3 Feed & bleed method This method continuously supplies raw water to the desalination tank, where it is desalted. Overflow water from the desalination tank is product water. Using this method, the tank is small compared to the batch method. 4.3.2.4 Multi-stage method The desalination rate of the one-pass method and the feed & bleed method increases using the multistage method. 4.4 Application examples 4.4.1 Ion exchange See Figure A.1. Typical IE processes are: — desalination for boiler feed water; — desalination for ultra-pure water; — softening for boiler feed water; — industrial wastewater treatment and recovery of valuable components; — desalination in the food-processing industry; — purification of various chemicals. 4.4.2 Electrodialysis See Figure A.2. Typical ED applications are: — table salt production from seawater; — tap water production from brackish water; — industrial wastewater reclamation; — desalination of landfill leachate; — desalination in the food-processing industry. NOTE EDR (Electrodialysis Reversal)IaI.Il is one kind of ED process that periodically reverses the electrodes polarity, alternating concentrated and diluted streams, and continuously self-cleaning the scale components. 4.5 Performance evaluation for ion exchange and electrodialysis Performance evaluation is divided into functional and non-functional requirements. Each requirement is described by the selected key factors, which should be measured and be considered at appropriate points and time intervals. Performance evaluations goals: -to ensure treated water quality and quantity; to ensure high efficiency; -，to keep designed performance throughout the expected lifetime. IE and ED are based on the same principle therefore the goals are same; however, these two categories are described in this document as different processes because equipment, devices and requirements are quite different. 5 Performance evaluation guideline for ion exchange resin[14]-[19] 5.1 Performance evaluation 5.1.1 Functional requirements Functional requirements are performance evaluation of treated water quality and regeneration efficiency. 5.1.1.1 Treated water quality To achieve the treated water quality, it is necessary to select IERs that have...
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