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Abstract :
[en] Due to global warming, more and more people are attracted by freshness of water in swimming pools but also in many other locations, including cities fountains, pounds… If the natural bathing area is located downstream of a wastewater treatment plant, a tertiary treatment of water is needed before disposal in rivers to respect the European Directive 2006/7/CE for surface water bathing area in term of microbiological water quality. According to this directive, intestinal Enterococcus must stay under 330 CFU/100 ml and Escherichia coli can’t overpass 900 CFU/100 ml in natural bathing waters.
Currently, the most conventional and useful technology to reduce pathogens uses UVC lamps, no matter if they are low or medium pressure. The UV energy alters the DNA structure of the microorganism in a process called thymine dimerization.
Despite the excellent results achieved by most of the UVC reactors, there are some technical and economic constraints:
• To avoid inadequate disinfection during the heating phase, the UVC lamps must run continuously, which leads to high energy costs and a reduction in lifetime.
• High operating costs of UVC devices due to the energy needs and to the price of UVC lamps (replacement every 12 months or after 12000 operating hours).
• Frequent oversizing of the UVC dose due to quartz sleeves fouling, and/or scaling, the water transmittance and the suspended solid load.
• Potential reactivation of microorganisms after UVC under visible light and/or in darkness.
Recently, photocatalysis and photo-induced processes have proved being effective for disinfection based on their deactivation capacity on numerous bacterial strains (John J. Alvear-Daza, & Al., Solar Energy 171, pp 761–768, 2018).
The aim of the project is to validate at pilot scale the effective and definitive disinfection performance of sol-gel photocatalytic reactor combined with UVA illumination as tertiary treatment of a waste water treatment plant or in closed circulating loops, taking advantage of killing germs by affecting their cell wall instead of DNA alterations.
