The disinfection with UVC radiation is a method that has been used for decades and has been proven to be effective for example for disinfection of surfaces as well as for water with low levels of pollution (such as drinking water, sewage treatment plant effluents).

UVC radiation inactivates microorganisms by damaging their deoxyribonucleic acid (DNA). Since microorganisms have DNA repair mechanisms, this carries the risk of reactivation.

In addition, the use of UVC radiation, especially for disinfecting of slightly contaminated water, is associated with not inconsiderable energy costs.

Against this background, a research project was carried out at the wfk Institute in collaboration with the Belgian cooperation partners CELABOR (project coordinator) and the Department of Chemical Engineering (focus: nanomaterials, catalysis, electrochemistry) of the University of Liège, in which a process for the photocatalytic UVA treatment of natural bathing waters was developed.

The subproject of the wfk institute focused on the evaluation of the disinfection effect to be achieved with the new photocatalytic process under UVA excitation.

Investigations to elucidate the mechanism of cell damage showed that photocatalytic UVA irradiation led to a loss of membrane integrity, a decrease in membrane potential and lipid peroxidation; oxidative damage to DNA was not detected using the marker molecule 8-OhdG.

Consequently, photocatalytic UVA treatment has the advantage over UVC irradiation that it damages the microbial cell membranes.

The suitability of photocatalytic UVA irradiation for the treatment of weakly microbially contaminated process waters, e.g. from textile service companies, was also investigated.

The research report is available on request from FRT.