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Trichloramine in swimming pools--formation and mass transfer
Christina Schmalz1, Fritz H Frimmel, Christian Zwiener
1Environmental Analytical Chemistry, Center for Applied Geoscience (ZAG), Eberhard Karls University Tuebingen, 72076 Tuebingen, Germany.
Trichloramine, an irritant disinfection by-product in swimming pools, forms readily from nitrogenous compounds like urea. Slow formation and gas transfer mean precursors and trichloramine (NCl3) removal is key to reducing bather exposure.
Area of Science:
- Environmental Chemistry
- Public Health
Background:
- Trichloramine (NCl3) is an irritant disinfection by-product found in indoor swimming pool air.
- It forms from reactions between nitrogenous compounds and chlorine.
Purpose of the Study:
- Investigate trichloramine formation from precursors like urea.
- Assess the kinetics and mass transfer of trichloramine in swimming pool environments.
Main Methods:
- Studied trichloramine formation from urea at different pH levels.
- Calculated NCl3 mass transfer from water to air using Deacon's boundary layer model.
Main Results:
- Urea is an efficient trichloramine precursor, forming 96% at pH 2.5 and 76% at pH 7.1.
- NCl3 formation is favored even at low chlorine-to-nitrogen ratios.
- Mass transfer of NCl3 from water is slow, taking 20 hours to 5.8 days.
Conclusions:
- Processes to remove trichloramine and its precursors are essential.
- Minimizing precursor presence and NCl3 formation can reduce bather exposure in swimming pools.
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