title: Bacteria in Public Swimming Pools – Inactivation Kinetics, Prevalence of Pathogens and Value of Indicators
creator: Kreuter, Leon
subject: ddc-570
subject: 570 Life sciences
description: Swimming pools and other recreational areas (e.g. hot tubs, saunas) enjoy worldwide popularity. Although procedures like disinfection are mandatory, swimming pools are commonly inhabited by diverse microorganisms potentially hazardous to human health, including viruses, bacteria, protozoans and fungi. Yet, there is a lack of comprehensive knowledge on the inactivation of microbes by disinfectants, the prevalence of pathogens in swimming pool water and the value of indicators in assessing the dangers associated.   One common class of disinfecting agents used in swimming pools are chlorine compounds, both because of their effectiveness in inactivating microbes and the accompanied low costs. Using chlorine, inactivation of microbes relies on the powerful oxidizing features of these compounds. Furthermore, as chlorine remains stable in water, these compounds may be used as residual agents. However, this common practice is accompanied by considerable disadvantages. Chlorine compounds readily react with a broad spectrum of potential partners, of which microbes are only a fraction. As a result, a large variety of disinfection by-products are released, some of which are significantly unhealthy. Considering the lack of knowledge on microbial hazards, the question arises, which concentrations of chlorine are necessary and preferable in public swimming pools.   The present study addresses several aspects of environmental hygiene associated with the use of chlorine in swimming pools. Two main tools in maintaining hygienic conditions are assessed: chlorine disinfection and evaluation of pool water quality using indicator bacteria. Routine data was analyzed for the occurrence of bacterial indicators. Applying MALDI-TOF techniques, it was determined which cultivable and potentially hazardous bacteria may be found in (German) public swimming pools. In order to include also less accessible and therefore less controllable parts of the microbial ecosystem of swimming pools, sand filter material was sampled and examined. Furthermore, inactivation kinetics of bacteria by hypochlorous acid were evaluated based on experiments using a setup mimicking swimming pool conditions and three exemplary test strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus). Raw data was fitted with several mathematical models taken from literature. In a parallel approach, chlorine consumption during the disinfection process was examined.   To date, regulations on swimming pool maintenance mainly rely on practical experience rather than on empiric data from scientific studies. The present thesis is motivated by the intention to fill this gap by providing information on the topics of disinfection and monitoring. Inactivation kinetics followed comprehensible trends comparable to the results achieved in other fields of research. Chlorine consumption during this process proceeded quite fast, which presumably influenced the outcome. The results on indicators and pathogens imply that the practice of using the first to assess the presence of the latter is questionable. Especially E. coli proved very susceptible to chlorine inactivation, making it a weak indicator. For P. aeruginosa, the occurrence of survival states (small colony variants, viable but non-culturable states) is assumed. Since the assessment of hygiene relies on culture-dependent methods, this has implications for swimming pool maintenance. The Gram-positive species S. aureus was considerably more resistant to chlorine than its Gram-negative counterparts, raising the question whether it would be more reasonable to use this species as an indicator. Also, the question arises if it is acceptable that normally only bacteria are used as indicators.
date: 2019
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserver/27281/1/DissertationLeonKreuter.pdf
identifier: DOI:10.11588/heidok.00027281
identifier: urn:nbn:de:bsz:16-heidok-272815
identifier:   Kreuter, Leon  (2019) Bacteria in Public Swimming Pools – Inactivation Kinetics, Prevalence of Pathogens and Value of Indicators.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/27281/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng