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Advanced CEDI Index Print E-mail

The advanced section is comprised of the following EDI topics:

Pretreatment to EDI systems - EDI Feedwater Requirements

Critical contaminants that adversely affect the EDI process include hardness (calcium, magnesium), organics (TOC), particulates and suspended solids (SDI), active metals (iron, manganese), oxidants (chlorine, ozone), and carbon dioxide (CO2).  The pretreatment process designed for the RO/EDI system should remove these contaminants from the feed water as much as possible.  Proper pretreatment design will greatly enhance EDI performance. Suggested water treatment strategies are listed throughout this section.  The main areas that affect EDI operation and performance are:

  • Dechlorination
  • CO2 - Carbon Dioxide
  • Particulates, Metals and TOC

EDI Process Considerations

  • EDI system Safeguards
  • EDI Process Design
  • Feed Water Hardness
  • Design to prevent EDI scaling
  • Avoiding a common mistake
  • Water Recovery
  • Product Water Quality
  • Reclaim of EDI Reject Water
  • Boiler Makeup Water (Power Plant)
  • Other EDI "Watchouts" – Feed Water
  • Other EDI "Watchouts" – Hydraulic
  • Feed Water Conductivity Equivalent (FCE)
  • DC Volts and Amps
  • Definition of EDI Recovery
  • Calculating Reject Flow
  • Suggested Test Kits

Factors Affecting EDI Performance

  • Voltage
  • Current
  • Ionic Species
  • Temperature
  • Flow
  • Feed Conductivity
  • Effects of contaminants

Optimizing EDI Performance

  • Voltage Driving Force
  • Current density
  • Ionic Balance and pH

Troubleshooting EDI Systems

  • Some Very Important Points to Remember!
  • Requirements for EDI troubleshooting
  • Questions To Ask
  • EDI Troubleshooting: Data Required
  • EDI Troubleshooting: Low Product Quality
  • Mass Balance Calculation
  • More going in than coming out
  • EDI Troubleshooting: Resistance Increase
  • EDI Troubleshooting: Low Flow
  • Flowcharts
  • Oxidants
  • Scale
  • Organic Fouling
  • Biofilm
  • Excessive Feed Pressure
  • High Temperature
  • Particulates


EDI Cleaning and Sanitization

  • Purpose of cleaning
  • When to Clean?
  • Chemicals Used on EDI
  • For Any Cleaning/Sanitization
  • Typical Cleaning System
  • General Considerations
  • Multiple Cleanings
  • HCl Cleaning Procedure
  • Brine/Caustic Cleaning
  • Sanitization: Definitions
  • Caustic Cleaning/Sanitization
  • Sodium Percarbonate Cleaning/Sanitization
  • Multi-Agent Cleaning ("3 Step")
  • Peracetic Acid Sanitization
  • Hot Water Sanitization
  • Hot Water Sanitization "watch-outs"
  • Which Cleaning for High d/p?
  • Which Cleaning for High Module Resistance?
  • Action for Quality Decline with no Other Symptoms?
  • Shutdown/Preservation
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