Abstract: Owing to the concomitant storage, transport, material and handling problems and the unsatisfactory retarding of reinfection, the use of commercially available peracetic acid solutions with a high peracetic acid (PES) and acetic acid content for disinfecting large quantities of aqueous solutions, e.g. purification plant outlets, has been closely limited. It is possible to disinfect even large quantities of aqueous solutions economically and at the same time retard reinfection by using a peracetic acid solution containing 1.5 to 2.5 wt. % peracetic acid and 40 to 60 wt. % hydrogen peroxide and under 2 wt. % acetic acid as a disinfectant. The use of a peracetic acid solution with less than 1 wt. % acetic acid is preferred.