Impact of scattering of UV radiation from an exciplex lamp on the efficacy of photocatalytic inactivation of Escherichia coli cells in water

We have used integrating-sphere UV spectroscopy to study scattering of radiation from an XeBr exciplex lamp (282 nm) by nanoparticles of a photocatalyst (TiO 2 ) and Escherichia coli CN13 cells. We have demonstrated that we must take into account scattered radiation in calculating the UV doses for disinfection of water in the presence of suspended TiO 2 particles. We have established that using the absorption intensities for the water to be disinfected in the dose calculation, obtained without taking into account the intensity of scattering of the radiation, leads to the actual dose exceeding the calculated dose by 5.2% to 69.4%. Total inactivation of the cells (from the absence of colony-forming units (CFU) after incubation of the irradiated aqueous suspension) was achieved at a UV radiation dose of 30 and 40 mJ/cm 2 and TiO 2 concentration of 0.25 and 0.10 g/L. The optimal concentration of TiO 2 in water determined was 0.25 g/L, which corresponds to the maximum concentration of hydroxyl radicals and the rate of their formation.