Geotechnical characterisation for landfill disposal of phosphoric acid production residues

The case study of a dismissed petrochemical plant located in Southern Italy is presented, wherein phosphoric acid production residues have to be transformed through a series of on-site treatment procedures into non-reactive stabilised wastes, which can be accepted for disposal in a non-hazardous solid waste landfill according to the regulations in force. Oedometric compression, triaxial shear, torsional ring shear and column leaching tests were carried out with the aim to determine the strength and deformability parameters of the stabilised residues, as well as to investigate the long-term mobility of water-soluble contaminants under a confining stress level that simulates the final disposal conditions. Such a characterisation of the coupled chemo-hydro-mechanical behaviour allowed the effectiveness of such treatment procedures in producing a waste stream that does not pose threats to the landfill geotechnical stability to be ascertained.