Protection of public health from microbial and chemical hazards in swimming pool environments

This thesis describes the occurrence of microbial and chemical contaminants in swimming pool environments and the investigation of an alternative disinfection technology, UVOX Redox® that could reduce reliance on chlorine and eventually reduce the formation of chlorinated disinfection byproducts (DBPs) in swimming pools. UVOX was proven effective in the inactivation of chlorine resistant microorganisms, represented by Bacillus subtilis spores, and generated lower concentrations of chlorinated DBPs in combination with chlorine compared to usage of chlorine alone. Moreover, it enhanced the removal of emerging contaminants, pharmaceuticals and personal care products (PPCPs), which are of concern due to their potential adverse human health effects. It was demonstrated that PPCPs were frequently present in pool water in different pools in Spain, including indoor, outdoor and spa pools. Carbamazepine and 1H-benzotriazole were the most frequently detected PPCPs, while hydrochlorothiazide and 4-methylbenzylidene camphor were detected at the highest concentration. Of the different types of pools studied, spa pools showed the most frequent detection of PPCPs. Based on the water treatment applied, the lowest frequency of detection of PPCPs was in swimming pools applying sand filtration followed by chlorination with sodium hypochlorite, while the lowest frequency of detection was in swimming pools applying coagulation, sand filtration, UV and salt electrolysis. An investigation of seven different swimming pool facilities in the Netherlands showed that clinically relevant fungi were omnipresent in the swimming pool environment. Floors at the sites where the pool visitors converge, such as the exit of the dressing rooms leading to the shower room, and the exit of the shower room leading to the swimming hall, showed the highest fungal concentrations. The distribution of fungi inside the swimming pool facilities highlighted potential transmission pathways and a possible risk of fungal infections. Since there are no guidelines for PPCPs or fungi in swimming pools, hygienic behaviour, such as pre-swim showering and wearing sandals, can be put into practice to reduce anthropogenic contamination. Frequent cleaning can also be applied to maintain the cleanliness inside a swimming pool facility, especially at the sites where pathogenic microorganisms can grow or accumulate. Future swimming pool water guidance should include raising awareness among swimmers, pool operators and managers about hygienic behaviour, and opportunities for better hygiene measures and application of alternative disinfection technologies such as UVOX