Electrodialysis in Water Treatment 101

Company Profile & Expertise
📌 Mega is a Czech-based specialist in electromembrane separation technologies, including electrodialysis (ED), electrodeionization (EDI), and electrophoresis.
🏭 The company produces its own ion exchange membranes and integrates them into electrodialysis stacks and full-scale industrial systems.
🌍 Established in the 1970s, Mega employs roughly 240 staff, with a strong focus on R&D involving 70 researchers and an annual turnover of approximately $40 million.

Electrodialysis Technology Basics
⚡ Electrodialysis uses a DC electrical field as the primary driving force to move ions through ion exchange membranes, effectively separating dissolved solids from water streams.
💧 The process creates two main streams: the diluate (desalinated water) and the concentrate (brine containing removed ions).
⚙️ Stacks consist of "cell pairs"—a repeating unit of a cation exchange membrane, a spacer, an anion exchange membrane, and a second spacer. These can be configured into multiple stages to increase the desalination rate.

Modes of Operation
🔄 Single Pass: Water passes through stacks once; typically used for large-scale brackish water desalination with recovery rates between 85% and 95%.
📉 Feed and Bleed: A continuous, steady-state process designed for high salinity applications (e.g., 20–80 g/L TDS), capable of concentrating salts up to 200 g/L.
📦 Batch Mode: A non-continuous process where water is recirculated until a specific conductivity is met; ideal for food and pharmaceutical applications to separate salts from valuable organic compounds.

Polarity Reversal (EDR)
🔄 Electrodialysis Reversal (EDR) involves periodically switching the electrical polarity (anode becomes cathode) every 15 to 30 minutes.
🧼 This process helps prevent fouling and scaling on the membranes, significantly reducing the requirement for chemical cleaning agents.
🛠️ Systems utilizing EDR require specific equipment, including titanium/platinum or MMO electrodes on both sides and additional valve manifolds to manage flow direction.

Key Points & Insights
➡️ Water Recovery: Electrodialysis is highly efficient for water recovery, typically achieving 85–95% efficiency in standard brackish water applications.
➡️ Operational Flexibility: By adjusting the number of stages (in-line stacks), operators can control the desalination percentage, while adjusting lines (parallel stacks) controls total flow capacity.
➡️ Valuable Resource Recovery: Beyond water treatment, the technology can effectively remove salts from non-charged organic feeds (like whey), converting waste into high-value products like infant formula.
➡️ Gas Management: Operation produces hydrogen, oxygen, or chlorine gases; systems must include ventilation loops and fans to safely discharge these gases from the facility.

📸 Video summarized with SummaryTube.com on Mar 26, 2026, 00:58 UTC