Untouchability of natural spa waters

Natural SPA waters and their environments were known since ancient times and used for health or recreational purposes in different societies, worldwide. The composition and uses of these spring waters may not allow standard disinfection in pools, representing a challenge for hygiene management. Several safety and quality procedures were proposed, but a systematic approach is still needed. Here, we focus on alternative strategies to provide hints for developing a sustainable Water Safety Plan, based on intrinsic water properties and photocatalytic materials. The antimicrobial activity of four different SPA waters with high mineral content and one drinkable spring water with a low mineral content, was assessed and then tested for the additional bactericidal activity of Titanium Dioxide (TiO2) nanomaterials and/or light exposure at different wavelengths (200-635 nm). A native antibacterial activity was observed in all high mineral content waters, with a CFU reduction of 75-80%. The bactericidal action of TiO2 showed an additional incremental effect, with a reduction of over 99% within 2-5 h. Interestingly, the antibacterial photocatalytic effect was detected also in the visible light range, with a possible pick around 450-455 nm, blue-light. Based on observed results, we propose a model for developing a water safety plan, considering water properties and bather exposure. This candidate approach is personalized on water composition and pool use, trying to avoid chemical disinfectants. Photocatalytic nanotechnologies represent one of the promising alternative treatments and can provide novel perspectives for a sustainable managing of natural SPA water hygiene.