Abstract: The invention relates to the treatment of aqueous materials such as clarified sludge. Disposal of such materials in large quantities is difficult and expensive. The present invention is directed to a treatment method that is economical and results in products which are at least as useful as the starting material. According to the invention, a treatment method comprises mechanical dewatering followed by drying in a fluidized bed drier and burning in a fluidized bed boiler. The heat generated in the boiler is at least sufficient to fulfill the requirements of the drier. The heat generated in the boiler is normally used directly in the drier.