Veolia Water Technologies & Solutions

Bipolar Electrodialysis (BPED)

For recovery of brine streams to produce acid and caustic product
Bipolar Electrodialysis uses the basics of electrodialysis but introduces a bipolar membrane which splits water into H+ and OH- within an electrodialysis stack. This allows the removed salts to be converted in their acid and/or base products.

Veolia’s BPED can be used in several applications, including organic acid production, pH adjustment in beverages, or using industrial brine to generate value added acid and caustic byproducts.

Download Electrodialysis Brochure

Overview

Veolia's BPED stacks use the same concepts as standard electrodialysis, with the addition of a so-called bipolar membrane that allows water to be split in H+ and OH- ions. By assembling membranes and spacers in specific configurations, the stacks can be used to:

  • 3C-BPED:
    • Split non-organic salts and produce separate acid and base streams.
  • 2C-BPED:
    • Split organic salts to product the organic acid and a base stream (e.g. potassium lactate (La) splitting to KOH and HLa).
    • pH modification of (up or down)

Stack Features

  • Up to 400 cells of membranes with application-specific membranes
  • Total active membrane area of up to 128 m2 per stack
  • Dual-entry stack to deliver consistent flow and pressure.
  • Robust stack design that is capable of Clean-in-Place (CIP) and can also be easily removed and disassembled for cleaning, maintenance, and component replacement if needed.
  • Spare parts can easily be stored on site.
  • Works with Veolia’s proprietary ion exchange membranes that offer specific benefits per applications:
    • AR119TP: acid-blocking membrane for chloride applications
    • AR118TP: acid-blocking membrane for sulfate applications

Under typical operating conditions of 375 A/m2, a 200C 3C-BPED stack can convert about 45.7 kg/h of NaCl, but can also be used to convert other inorganic salts (Na2SO4, LiCl, Li2SO4, KCl, K2SO4). The strength of the acid and base can be tuned between 0.5N and 2N.

How It Works

Bipolar Electrodialysis introduces a BP membrane in the stack that splits water in H+ and OH- when the voltage is applied.

As with standard electrodialysis (Figure 1) , the voltage also moves the ions from the salt feed stream through the cation exchange and anion exchange membranes. Contrary to standard ED though, the cations and anions are not entering the same water stream, but in separate stream on each side of the BP membrane, thus combining with the H+ and OH- to form their conjugated acid and base. This is called 3-compartment BPED, or 3C-BPED.

In a 2-compartment BPED (2C-BPED) configuration, one of the monopolar membrane is left out of the equation, meaning the applied voltage will only move either anions or cations away from the salt feed solution, replacing them by OH- or H+ ions respectively:

BPED principle

Figure 1: Standard Electrodialysis Process Diagram

 

2C-BPED-C (Figure 2):

  • In this case, the cation exchange membrane is kept and the anion exchange membrane is removed from the stack.
  • When the voltage is applied, the cations move through the cation exchange membrane and combine with the OH- generated in the BP membrane, forming a separate base stream.
  • The H+ from the BP membrane enters the salt feed stream and decreases the pH.
  • This is typically used for organic salt splitting, generating an organic acid and a base stream that can be reused in the upstream process.

BP2-C principle

Figure 2: 2C-BPED-C Process Diagram

 

2C-BPED-A (Figure 3):

  • In this case, the anion exchange membrane is kept and the cation exchange membrane is removed from the stack.
  • When the voltage is applied, the anions move through the anion exchange membrane and combine with the H+ generated in the BP membrane, forming a separate acid stream.
  • The OH- from the BP membrane enters the salt feed stream and increases the pH.
  • This is typically used for pH control of stream like wine and fruit juice, or ammonium nitrate splitting.

BP2-A principle

Figure 3: 2C-BPED-A Process Diagram

Related Products

  • 2025 © Copyright Veolia

*Trademark of Veolia; may be registered in one or more countries.