Integrated electrodeionization with bipolar membranes for dialysis water treatment
An integrated electrodeionization system with bipolar membranes (EDI-BM) that removes both water hardness and free chlorine from tap water for dialysis patients. The system targets reduction of hardness from 450 mg/L to 2 mg/L and free chlorine from 2 mg/L to 0.1 mg/L, addressing a critical need in dialysis water purification.
Overview
This solution proposes an integrated electrodeionization system combined with bipolar membranes (EDI-BM) to treat tap water for dialysis patients. Current dialysis water treatment requires removal of both hardness ions (calcium and magnesium) and free chlorine to protect patients from exposure to harmful contaminants. The EDI-BM system is designed to simultaneously address both challenges in a single process, reducing water hardness from 450 mg/L to 2 mg/L and free chlorine concentration from 2 mg/L to 0.1 mg/L.
The innovation lies in leveraging bipolar membranes to generate hydroxide ions that convert free chlorine into OCl-, which can then be removed through standard EDI ion-removal mechanisms. This integration eliminates the need for separate treatment steps, potentially reducing equipment footprint, operational complexity, and costs for dialysis clinics and water treatment facilities.
Technical specifications
- Electrodeionization (EDI): A proven electromembrane technology that uses electrical current and ion-exchange resins to remove ionized species from water, widely used in ultrapure water production.
- Bipolar membranes (BM): Specialized membranes that dissociate water into hydrogen ions on the negative side and hydroxide ions on the positive side when subjected to an electrical field.
- Integrated mechanism: The OH- generated by bipolar membranes converts free chlorine (HOCl) to OCl- form, enabling its removal through the same EDI process that captures calcium and magnesium ions.
- Target performance: Hardness reduction from 450 mg/L to less than 2 mg/L and free chlorine reduction from 2 mg/L to 0.1 mg/L.
- Recovery rate: System designed to operate at 95% water recovery in upscaled configurations.
Technology readiness level
The technology is at an early-to-mid stage of development. Published literature has independently validated EDI for hardness removal (reducing Mg2+/Ca2+ from 100 mg/L to less than 2.5 mg/L) and integrated EDI-BM systems for ultrapure water production from reverse osmosis permeate. However, the simultaneous removal of both hardness and free chlorine using an integrated EDI-BM system has not yet been demonstrated.
The planned validation pathway begins with proof-of-concept experiments using a simplified electrodialysis system to confirm OCl- removal, hardness reduction at target concentrations, and pH control. Subsequent phases involve testing with an upscaled PC-Cell system to evaluate hardness removal at 95% recovery, followed by implementation of bipolar membranes for simultaneous removal. Process parameters will be optimized to maximize production and water purity.
About University of North Carolina, Chapel Hill
UNC–Chapel Hill is a comprehensive public research university and the state’s flagship, pairing broad academic depth with a major academic health system. Industry partners access co‑located core facilities, sponsored research, and an on‑campus innovation hub that connects companies to faculty and advanced instrumentation. Integration with a major hospital system and statewide clinics enables patient access, clinical trials, and real‑world evidence collaborations. Minutes from Research Triangle Park, the university works within a dense corporate R&D ecosystem. Research is supported by strong competitive federal funding, including NIH and NSF, and a dedicated technology transfer office streamlines IP, licensing, MTAs, and startup formation.
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