Intermediate free radicals in the oxidation of wastewaters

The cleaning action on wastewater as obtained through oxidation methods has been investigated by means of EPR spectroscopy to achieve qualitative and quantitative information on the radicals produced upon utilising peracetic acid and hydrogen peroxide with and without UV irradiation. The DEPMPO spin trap was employed to detect hydroxyl and carbon-centred short living radicals during water disinfection, either in the absence or in the presence of UV-C irradiation. Moreover, three different kinds of water (wastewater, demineralized water, distilled water) were analysed in order to assess the contribution of Fenton reactions to the radical production. The spectroscopic results are discussed in relation to the efficiency of the different oxidising agents and UV irradiation in wastewater disinfection evaluated as Escherichia coli, faecal and total coliforms inactivation.