Disinfection by HO2 Radicals Generated by Negative Corona Discharge on Acidic Solution

An oxygen-supplied negative direct current (dc) corona discharge on acidic solution is studied to reduce the odor associated with conventional disinfectants, such as ClO
^-
, HClO, O
₃
, and ClO
₂
. The discharge system provided an odorless bactericide of hydroperoxyl (HO2) radicals, generated from the reaction of discharge-generated O
₂
^-
with H
⁺
in the acidic solution. A 2.5-log reduction of Escherichia coli (E. coli) was observed under the conditions of pH 2.8, dc -4.8-kV dc, and -17 μA, where the concentration of ozone and hydrogen peroxide was too low to inactivate the E. coli. At a pH of 5.6 or by adding a superoxide dismutase, which is a scavenger of HO
₂
, negligible inactivation was observed.