Disinfection of Therapeutic Spa Waters: Applicability of Sodium Hypochlorite and Hydrogen Peroxide-Based Disinfectants
2022
Dóra Gere | Eszter Róka | Gyula Záray | Márta Vargha
The microbial water quality of therapeutic pools operating without disinfection is recurrently compromised, posing a risk to bathers’ health. The complex composition of such waters and the sensitivity of their therapeutic components hinder the use of traditional chlorine-based disinfectants. The present study aimed to investigate the applicability of a hydrogen peroxide-based disinfectant in therapeutic water in comparison with hypochlorite. Disinfection efficacy, byproduct formation, and the fate of therapeutic components were tested for both disinfectants under laboratory conditions, applying different doses and contact times. Disinfection efficacy was found to be matrix-dependent, especially that of hydrogen peroxide against <i>Pseudomonas aeruginosa</i> (a 10- to 1000-fold difference). Hypochlorite treatment presented a significant chemical risk through the generation of byproducts, mainly brominated and iodinated compounds and combined chlorine. Of the alleged therapeutic components, sulfide ions were eliminated (≥86% loss) by both disinfectants, and hypochlorite reacted with iodide ions as well (≥70% removal). Based on their composition, only 2% of Hungarian therapeutic waters can be treated by chlorination due to high concentrations of ammonia and/or organic compounds. Hydrogen peroxide is applicable to 82% of the waters, as the presence of sulfide ions is the only limiting factor. Due to the matrix effect, close control of residual disinfectant concentration is necessary to ensure microbial safety.
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