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.  BPED takes advantage of this process to either split salt streams into acid and caustic products or can adjust the pH of a process stream. 

Veolia’s Ionics 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.

Description & Use

The Ionics* 3CBPED Stack is an electrodialysis stack, specially-designed with three compartments and bipolar membranes. The stack can be used to split non-organic salts, producing separate acid and caustic streams.

Within the stack, an electric current is used to move anions through anion-selective membranes, cations through cation-selective membranes, and to split water into H+ and OH- ions. With the 3-compartment stack design, this generates two product streams (one acid and one caustic) and a dilute salt stream.

Stack Features

  • 200 cells of Ionics Bipolar Membranes used for salt splitting along with Ionics AR118U and CR61N.
  • Total active membrane area of 64 m2 per type
  • Dual-entry stack to deliver consistent flow and pressure.
  • Robust stack design that is capable of 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.
  • Integrated electrode chambers; no requirement for external electrode feed plumbing and control loop.


Typical Performance

Under typical operating conditions of 375 A/m2, the 3CBPED stack will convert salt in the following capacities (others calculated in kg/hr by multiplying the equivalent weight of the salt by 0.582):

NaCl à NaOH + HCl:  34.0 kg/hr

Na2SO4 à NaOH + H2SO4:        41.3 kg/hr

LiCl à LiOH + HCl:  24.6 kg/hr

Li2SO4 à LiOH + H2SO4:  31.9 kg/hr


The acid and caustic streams produced by 3CBPED have a typical strength of 2N with the use of our acid blocking anion membrane, the AR118U. Consult with Veolia for information on system design for specific applications.

Temperature:  40 to 100ºF (4 to 50ºC)

Typical Feed:                Min 4%           Max: 90% of saturation

Operating Pressure:   2-3 bar (28-43 psi)

Turbidity:  5 NTU

TOC:  < 60 ppm (mg/l)

COD:  < 200 ppm (mg/l) as O2

Manganese, Aluminum:  < 0.1 ppm (mg/l)

Total Hardness:  <10 ppm (mg/l)