EDI Technology within the PURELAB® Chorus 2+ (RO/EDI/UV)

Importance of the Topic

Ultra-pure water is a foundational requirement in modern laboratories and industrial processes, underpinning reliable analytical results, protecting sensitive equipment, and ensuring compliance with stringent quality standards. Electrodeionization (EDI) stands out as an advanced continuous-regeneration technology that minimizes consumables and waste, providing stable, high-resistivity water suitable for a wide range of applications.

Study Objectives and Overview

This technology note presents the design and performance of the PURELAB Chorus 2+ system, which integrates reverse osmosis (RO), electrodeionization (EDI), and ultraviolet (UV) irradiation to deliver Type II+ water directly from a potable source. Key goals include demonstrating continuous recirculation to maintain water purity, evaluating the system’s response to variable feedwater quality, and highlighting operational efficiencies compared with conventional DI pack methods.

Methodology and Instrumentation

Water purification in the PURELAB Chorus 2+ follows a multi-stage process:

• Feedwater pretreatment through an activated carbon bed to remove chlorine.
• Reverse osmosis cartridges for semi-purification, yielding RO permeate.
• Optimized cartridge to eliminate residual hardness before EDI.
• Electrodeionization module employing mixed-bed, cation- and anion-exchange resins, and ion-permeable membranes under applied current for continuous ion removal.
• UV lamp for microbiological control.
• Optional degasser to remove excess CO₂ in high-carbonate feedwater regions.
• Recirculation loop with pump, flow switch, and water purity sensors to sustain resistivity and microbial specifications.

Although the system employs multiple sensors (chlorine, purity, temperature, flow) and pumps (booster, recirculation), all instrumentation is integrated into a compact, user-friendly unit.

Key Results and Discussion

• Steady product resistivity consistently exceeds the >10 MΩ·cm specification, regularly achieving >15 MΩ·cm due to continuous recirculation through EDI and UV stages.
• Recirculation of reservoir water dilutes RO permeate during transient feedwater fluctuations, ensuring optimum EDI operating conditions and rapid recovery from poorer feed quality without purity loss.
• Continuous resin regeneration prevents silica, boron, or organic breakthrough and eliminates the need for disposable DI packs, maintaining stable performance over time.
• Energy consumption of the EDI module remains low at typically <14 W, contributing to overall system efficiency.

Benefits and Practical Applications

• Eliminates periodic cartridge changes and reduces consumable waste, lowering environmental footprint.
• Delivers consistent Type II+ water suitable for general laboratory uses, QA/QC, and industrial analytical tasks.
• No final point-of-use microfilter is required, while microbiological levels stay below 1 CFU/mL.
• Lower operational costs compared with systems relying on disposable resin cartridges.
• Optional degasser extends applicability to regions with high dissolved CO₂.

Future Trends and Opportunities

• Integration of real-time digital monitoring and predictive maintenance to further optimize performance and reduce downtime.
• Advancements in membrane materials and EDI stack design to push resistivity toward Type I purity levels.
• Enhanced automation with IoT connectivity for remote control and data analytics in regulated environments.
• Modular expansion capabilities to tailor systems for pharmaceutical, semiconductor, and bioprocessing industries.

Conclusion

The PURELAB Chorus 2+ (RO/EDI/UV) system demonstrates how recirculating electrodeionization combined with RO pretreatment and UV disinfection can deliver stable, high-resistivity water with minimal consumables and waste. Its low energy use, continuous regeneration of resins, and robust purity maintenance make it a versatile solution for modern laboratory and industrial water needs.

References

• ELGA LabWater. Technology Note 33: EDI Technology within the PURELAB® Chorus 2+ (RO/EDI/UV). VWS (UK) Ltd., 2019.