A vacuum toilet system comprises a toilet bowl having an outlet opening, a sewer pipe having an interior space, a discharge valve connecting the outlet opening of the toilet bowl to the sewer pipe, and a source of partial vacuum for establishing a lower pressure in the interior space of the sewer pipe than in the toilet bowl. A nozzle defines a rinse liquid outlet for introducing liquid into the toilet bowl. A container for reagent is in communication with the rinse liquid outlet. Reagent is introduced into the toilet bowl by way of the rinse liquid outlet in timed relationship to introduction of rinse liquid into the toilet bowl.