The invention relates to a method for purifying wastewaters, particularly wastewaters produced in the paper industry, involving the following steps: a) aerobic clarification of the wastewater using activated sludge in an activation stage; b) carrying out, in a secondary settling tank, a subsequent clarification of a portion of the wastewater/activated sludge mixture leaving the activation stage; c) desiccating, in a desiccation unit, another portion of the wastewater/activated sludge mixture leaving the activation stage; d) returning at least a portion of the activated sludge removed in steps b) and c) into the activated sludge tank.