Potable water being disinfected with chlorine dioxide must have, after completion of the treatment cycle, a detectable minimum chlorine dioxide residual of 0.05 mg/l. In cases where the drinking water is dechlorinated before it is transferred into the distribution mains, the residual must be detectable prior to dechlorination (Art. 1, para. 4).

The limit value in treated potable water must not exceed 0.3 mg/l of free chlorine respectively 0.2 mg/l of chlorine dioxide. The maximum dose for chlorine or its compounds is limited to 1.2 mg/l, for chlorine dioxide to 0.4 mg/l.

The maximum chlorine dose may be increased up to 6 mg/l, if the microbiological requirements cannot be met by another method, or in cases where the disinfection is temporarily impaired by ammonia. The free available chlorine residual of the treated water must in this case not exceed 0.6 mg/l.

Bactericidal effectiveness depends on the thorough mixing of the chlorine solution with the water to be treated, on contact time, pH value, water temperature, and chlorine residual. The table shows the correlation of these parameters.