No document available.
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.