Microbiological water quality assessment of swimming pools and jacuzzis in Northern Greece: a retrospective study

Swimming pools and jacuzzis can pose significant public health risks as potential sources of infections. The present study aimed to evaluate the prevalence and concentration of microbiological indicators in recreational water facilities in Thessaloniki, Northern Greece, focusing on their hygiene status before and after the COVID-19 pandemic. Between January 2018 and December 2022, 1114 water samples were analyzed by the regional Water Hygiene Laboratory at Aristotle University of Thessaloniki, using standardized ISO methods. Jacuzzis exhibited the highest microbial contamination, particularly for Pseudomonas aeruginosa (19.7%), while indoor adult pools showed the lowest. Overall, P. aeruginosa was found in 12.4% of samples, with the highest concentrations in jacuzzis (median: 30 CFU/100 ml). Significant seasonal variations were identified in the prevalence of total microbial flora (p < 0.001) and total coliforms (p = 0.03), as well as in the concentration of residual chlorine (p = 0.023). During the COVID-19 pandemic, microbial prevalence decreased across facilities. We concluded a strong compliance with Greek and international microbiological standards. The decline in microbial prevalence overtime likely reflects the impact of the strict hygiene measures implemented during the pandemic. These findings highlight the importance of maintaining rigorous hygiene practices to protect public health.