Disinfection of Therapeutic Spa Waters: Applicability of Sodium Hypochlorite and Hydrogen Peroxide-Based Disinfectants

Abstract

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 Pseudomonas aeruginosa (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.

Antimicrobial dichloroisocyanurate-salts for controlled release of chlorine

“…Na-DCC (5 g, 1 eq., 22.732 mmol) was dissolved into 30 ml of distilled water. To this was added a solution of tetrabutylammonium bromide (7.328 g, 1 eq., 22.732 mmol) in 10 mL of water.…”

“…Na-DCC (5 g, 1 eq., 22.732 mmol) was dissolved into 30 ml of distilled water. To this was added a solution of tetrabutylammonium bromide (7.328 g, 1 eq., 22.732 mmol) in 10 mL of water. After the addition, the immediate formation of white color precipitates was observed, and the reaction mixture further allowed for stirring at 30 min.…”

“…19 In this context, examples of chlorine-containing compounds available for water disinfection effects include chloroisocyanurates (sodium dichloroisocyanurate, trichloroisocyanuric acid), and hypochlorites (ex: Li, Ca, and Na hypochlorite). [20][21][22][23][24][25] These compounds generate Free Available Chlorine (FAC) in the form of HClO and ClO − . FAC is a measure of the oxidizing or bactericidal ability of active chlorine in a compound, expressed as elemental chlorine, and is commonly referred to in the water treatment industry as a weight percent.…”

Effect of atmospheric cold plasma (ACP) on chlorine-adapted Salmonella enterica on spring onion

“…Among the approved disinfectants in food industry, chlorine and chlorine-based materials are the most available disinfectants due to their lower cost and broad inactivation range on bacteria (Bansal et al 2019). Sodium hypochlorite as chlorine-based disinfectant is the ideal disinfectant with high efficacy against most pathogens (Gere et al 2022). Nevertheless, any exposure of bacteria to sub-lethal concentrations of disinfectants may constitute a critical public health challenge such as emergence of highly invasive pathogens with reduced susceptibility to antibiotics and increased ability to form biofilm (Dubois-Brissonnet 2012).…”

“…Sodium hypochlorite as chlorine‐based disinfectant is the ideal disinfectant with high efficacy against most pathogens (Gere et al . 2022). Nevertheless, any exposure of bacteria to sub‐lethal concentrations of disinfectants may constitute a critical public health challenge such as emergence of highly invasive pathogens with reduced susceptibility to antibiotics and increased ability to form biofilm (Dubois‐Brissonnet 2012).…”