<p>Biological purification of condensate from a process for the manufacture of sheets of disintegrated lignocellulose-containing material, such as fibreboard produced according to the dry method or particle board, where the condensate contains formaldehyde. The condensate is treated in several steps in a treatment vessel (2) divided into sections (3-7). The purification is carried out substantially with the help of a microorganism of the species Trichoderma.</p>
