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Modeling a novel ion exchange process for arsenic and nitrate removal
Jaeshin Kim1, M M Mark M Benjamin
1Department of Civil and Environmental Engineering, University of Washington, PO Box 352700 Seattle, WA 98195-2700, USA.
Water Research
|April 17, 2004
Summary
A modified ion exchange process effectively removes arsenate and nitrate from drinking water, significantly reducing regenerant brine requirements, especially at lower nitrate concentrations. This method enhances water treatment efficiency and sustainability.
Area of Science:
- Environmental Science
- Chemical Engineering
- Water Treatment Technology
Background:
- Anion exchange can remove arsenate and nitrate from drinking water.
- High sulfate or nitrate levels exhaust resins quickly, increasing regenerant brine needs and making the process less attractive.
Purpose of the Study:
- To extend a modified ion exchange procedure for arsenic removal to solutions containing nitrate.
- To develop a mathematical model for this modified ion exchange process.
- To evaluate the process's efficiency and brine requirements for various water compositions.
Main Methods:
- Investigated the selectivity coefficient of sulfate over nitrate for a strong base anion exchange resin at varying ionic strengths.
- Developed a mathematical model incorporating mass balances and solid/liquid equilibrium.
- Analyzed brine requirements for the modified treatment process with different influent water compositions.
Main Results:
- The selectivity coefficient for sulfate over nitrate increased with ionic strength, partially offsetting predicted decreases in the separation factor.
- Modeling indicated significantly increased water treated per unit of brine at lower influent nitrate concentrations.
- The modified process remained advantageous at higher nitrate levels, though less so. Separate brine regeneration further magnified benefits.
Conclusions:
- The modified ion exchange process offers a more sustainable approach to removing arsenate and nitrate from drinking water by optimizing brine usage.
- Mathematical modeling provides a valuable tool for predicting process performance and optimizing regenerant strategies.
- Precipitating sulfate as calcium sulfate (CaSO(4)(s)) in brine is a viable, albeit slightly less efficient, alternative to barium sulfate (BaSO(4)(s)).
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