EWT Water Technology – Water Treatment

EWT Water Technology

Electrodeionisation (EDI)

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EDI (short for Electrodeionsiation), also CEDI (short for Continuous Electrodeionsiation), is an electrochemical membrane process for polishing of →demineralised water, meaning for removal of trace dissolved solids from water.

Basically, EDI is a variation of electrodialysis. Demineralisation within an EDI-module occurs by applying an electrical field accross ion-selective membranes. The ion-selective membranes form chambers, which are filled with ion exchange resin. Cations and anions move within the electrical field in accordance with their respective electrical charge, and are then retained in concentrate chambers by the ion-selective membranes.

EDI is a continuous process. During operation, concentrate will continuously be either discharged as waste water, or recycled into an upstream process step.

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Design Example:

EDI plant

EDI plant, single line, skid-mounted together with an upstream reverse osmosis plant.

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Technical Data:

product volume flow available from approx. 0.5 up to 100 m³/h for each line
amount of lines usually 1× 100% or 2× 50%
product quality electrical conductivity < 0.2 μS/cm
silicic acid < 20 μg/L SiO2
recovery 90% ... 95%
differential pressure at nominal flow approx. 2 bar
operating pressure ≤ 6 bar
operating temperature 5 ... 40 °C
concentrate discharge corresponding to the recovery, 50 ... 100 L for each 1 m³ product
concentrate quality electrical conductivity approx. 50 ... 300 μS/cm
electrical energy demand approx. 0.1 .... 0.3 kWh for each 1m³ product
recommended feed quality source reverse osmosis feed
electrical conductivity ≤ 30 μS/cm
free carbon dioxide < 1 ... 10 mg/L CO2
water hardness < 0.01 mmol/L
iron < 0.01 mg/L Fe
manganese < 0.01 mg/L Mn
silicic acid < 1 mg/L SiO2
free chlorine < 0.02 mg/L Cl2
total organic carbon (TOC) < 0.5 mg/L C
total service life of the EDI modules usually ≥ 5 years
material options module housing • polyvinyl chloride (PVC)
• glass-rintroductionorced plastic (GRP)
pipelines • polyvinyl chloride (PVC)
• polypropylene (PP)
• polyvinylidene fluoride (PVDF)
• stainless steel (e.g. 1.4404, 1.4539)
valves • polyvinyl chloride (PVC)
• polypropylene (PP)
• polyvinylidene fluoride (PVDF)
• stainless steel (e.g. 1.4408)
gaskets • etyhlene propylene diene monomer rubber (EPDM)
• polytetrafluorethylene (PTFE)
skid • stainless steel (e.g. 1.4301)
control options start-up, service, and shut-down • fully automated, via micro-processor control unit
• fully automated, via PLC
process monitoring • gauge pressure (option)
• differential pressure (option)
• volume flow concentrate (standard)
• volume flow product (option)
• electrical conductivity product (standard)
• silicic acid product (option)

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2018-05-05 • water treatment made in GermanyCompany InformationPrivacy