NOVELTY - The process comprises obtaining the digested sludge by primary digestion of sludge, obtaining an aqueous first effluent (14) and partially dehydrated digested sludge by a first solid-liquid separation of the sludge, obtaining a partially dehydrated and hydrolyzed digested sludge by thermal hydrolysis of digested sludge, digesting the partially dried and hydrolyzed sludge, and retrieving a biogas formed during digestion and producing primary stage production of energy from the biogas. The step of production of energy comprises a sub-step of production of necessary energy.    USE - The process is useful for the treatment of organic wastes and municipal and industrial water to obtain non-decayed sludge and to produce energy e.g. electricity.    ADVANTAGE - The process is capable of simply, reliably and economically treating the organic wastes with less energy consumption thus providing large quantity of non-decayed sludge, which is easily fermentable and biodegradable.    DETAILED DESCRIPTION - The process comprises obtaining the digested sludge by primary digestion of sludge, obtaining an aqueous first effluent (14) and partially dehydrated digested sludge by a first solid-liquid separation of the sludge, obtaining a partially dehydrated and hydrolyzed digested sludge by thermal hydrolysis of digested sludge, digesting the partially dried and hydrolyzed sludge, and retrieving a biogas formed during digestion and producing primary stage production of energy from the biogas. The step of production of energy comprises a sub-step of production of necessary energy by thermal hydrolysis and a sub-step of production for excess energy. A second aqueous effluent is obtained and then treated by a second solid-liquid separation of sludge. The thermal hydrolysis is carried out at a pressure equal to the saturation vapor pressure and a temperature of 165 degrees C for 30 minutes. The digestion and primary digestion are mesophilic or thermophilic anaerobic digestion. The primary digestion is carried out after defibration of the sludge. An INDEPENDENT CLAIM is included for an installation for the treatment of sludge.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of an installation for the treatment of sludge (Drawing includes non-English language text).    Primary digester (10)    Secondary digester (11)    Sludge supply pipe (12)    First liquid-solid separation unit (13)    First effluent. (14)