Water quality analysis in a municipal outdoor swimming pool complex before and during the COVID-19 pandemic

Like all public utility, swimming pools had been treated with special procedures during the COVID-19 pandemic. In addition to the basic rules (social distance + hand disinfection + masks), applicable to all citizens, the managers of swimming pools were obliged to reduce the number of swimmers and to increase the effects of water treatment. Monitoring, control and rapid response to unfavour-able changes in the quality of swimming pool water are the basis for minimizing the risk of disease transmission or exposure of bathers to pathogens. The main purpose of this work is to analyse and compare the quality of swimming pool water in a municipal outdoor swimming pool complex, before (2018–2019) and during the COVID-19 pandemic (2020–2021). Water samples taken from a paddling pool for children (CP), a recreational pool (RP), and a sports pool (SP) were analysed. The results of the research, based on real case studies, were compared with the documents on water quality in swimming pools in force at the time. An analysis was carried out to determine the relationships between swimming pool water quality before and during the COVID-19 pandemic. The tested parameters determining the quality of water were physico-chemical parameters (temperature, pH, redox, turbidity, nitrates, chemical oxygen demand, free chlorine, chloramines and trihalomethane THM) and bacteriological parameters (colony forming units CFU of Pseudomonas aeruginosa, Escherichia coli, Legionella sp.). Based on the results of the analysis of the parameters mentioned-above, the val-idation of the procedures applied during the COVID-19 hazard and their impact on the quality of swimming pool water were evaluated. The results of the pool water quality tests were discussed with particular emphasis on disinfection by-products (THM and combined chlorine). Detailed analysis showed better water quality in the first year of the pandemic (2020) compared to 2018–2019 (before COVID-19) and 2021 (the second year of COVID-19 pandemic). The following parameters were found to be significantly different: THM (before 0.069 mg/L and during 0.034 mg/L), free chlorine (before 0.86 mg/L and during 0.66 mg/L), and redox potential (before 667 and during 713 mV).