Abstract: Decontaminating a liquid--such as a liquid containing radioactive materials--by evaporation, includes the steps of guiding the vapor through plurality of wash liquid baths and guiding the wash liquid through the individual baths substantially in a countercurrent to the vapor. The step of guiding the wash liquid comprises the steps of introducing the wash liquid into each bath along an outer edge zone thereof; guiding the wash liquid in each bath radially inwardly towards a centrally located outlet in each bath; and guiding the wash liquid through the central outlet. The step of guiding the vapor comprises the steps of passing the vapor through the wash liquid in a central zone of each bath and subsequently deflecting the vapor above each bath in a radially outwardly oriented direction.