Identification of the species of active oxygen generated in water by chlorination or ozonation was carried out by the spin trapping method using DMPO as the spin trap agent with ESR spectrometry. On chlorinating with NaOCl solution (15 mg/litre), typical ESR signals for DMPO-OH adduct were observed. Increasing the concentration of NaOCl, however, caused complex spectra to appear. The addition of thiourea or D-mannitol, as a radical scavenger, did not significantly affect on the intensity of the signals. On ozonation, two radicals, DMPO-OH and an unknown radical, were always observed. These results indicate the generation of several radicals in the solution treated with NaOCl and ozone.

An interaction of the polio virus with OH was also studied. The preliminary test showed that the OH generated by Fenton's reaction slightly disinfected the virus. Precise tests changing the concentration of active oxygen and the reaction condition are currently in progress.

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