To provide the treatment process which comprises subjecting a slurry of sewage or the like, that contains sludge, etc., and is conventionally disposed as waste, to primary compression to form primary-compressed sludge, then subjecting the sludge to secondary compression under high pressure to form secondary-compressed sludge in a highly dehydrated state, then in the secondary compression stage, adding a waste synthetic resin material hardly disposed as waste, such as polyvinyl chloride or other plastic materials, in the form of chips, to the secondary-compressed sludge under pressure to mix them and to form an integrated material, subjecting the integrated material to solid-liquid separation to form a cake, and treating the cake so as to enable its effective utilization directly as a solid fuel or as a material for an effective recycled product such as surfactant, soil conditioner, or the like.

This treatment process comprises: forming a waste synthetic resin material into chips; also, subjecting a slurry to primary compression to form primary-compressed sludge; subjecting the primary-compressed sludge to secondary compression to form secondary- compressed sludge in a highly dehydrated state; mixing the waste resin in the form of chips with the secondary-compressed sludge to form a mixture; subjecting the mixture to solid-liquid separation to form a cake; and treating the cake so as to enable effective utilization of it as an effective recycled product or its material. Thus, sewage containing sludge and waste synthetic resin material that is hardly subjected to direct disposal as waste, can concurrently be treated altogether in one plant and also the treated cake thus obtained can directly and effectively utilized as an effective recycled product or its material.