Enhanced DOC removal using anion and cation ion exchange resins

Area of Science:

• Water treatment technologies
• Environmental engineering
• Chemical engineering

Background:

• Conventional water treatment often requires separate processes for hardness and dissolved organic carbon (DOC) removal.
• Ion exchange is a key technology, but optimizing simultaneous removal of multiple contaminants is challenging.
• Existing methods may involve complex infrastructure, chemical additions, and sludge disposal.

Purpose of the Study:

• To evaluate the efficacy of simultaneously applying cationic (Plus) and anionic (MIEX) ion exchange resins in a single unit for water treatment.
• To assess the impact of this combined approach on hardness and DOC removal efficiency.
• To determine the operational advantages and waste reduction potential compared to separate treatment processes.

Main Methods:

• Bench and pilot-scale testing of a single ion exchange unit employing both Plus and MIEX resins.
• Multiple regeneration cycles were performed to assess resin durability and performance over time.
• Comparison of contaminant removal (hardness and DOC) between simultaneous resin application and sole MIEX resin treatment.
• Analysis of water characteristics, including fluorescence intensity, to understand DOC removal mechanisms.

Main Results:

• Hardness removal closely matched theoretical predictions, achieving 88-98% of expected values.
• Simultaneous Plus and MIEX resin treatment enhanced DOC removal by 0.5 to 1.25 mg/L compared to using MIEX resin alone.
• Full-scale MIEX treatment reduced DOC from 13.7 mg/L to 4.90 mg/L, while a pilot-scale simultaneous Plus and MIEX system achieved <3.4 mg/L DOC.
• The enhanced DOC removal was primarily attributed to the removal of terrestrially derived organic matter, resulting in water with a predominantly microbial character.

Conclusions:

• Integrating cationic (Plus) and anionic (MIEX) ion exchange resins into a single unit operation effectively removes both hardness and dissolved organic carbon (DOC).
• This simultaneous approach offers significant advantages in process simplification, reduced infrastructure needs, and elimination of chemical additives and sludge waste associated with precipitative softening.
• The combined resin system presents a more efficient and environmentally friendly water treatment solution.