Abstract: A process for the thermophilic aerobic treatment of concentrated organic waste water includes the following stages: subjecting the waste water to a fluidized-bed thermophilic aerobic biological treatment, inside a closed reactor, provided with a thermostat control system and a hydraulic recirculation system; subjecting the water to an ultrafiltration treatment; and discharging treated waste water, wherein pure oxygen O2 is insufflated inside the reactor; lime Ca(OH)2 is available during the fluidized-bed thermophilic aerobic biological treatment, whereby the lime forms by reacting with carbon dioxide generated by the degradation of the organic substrate in the biological process, a natural inert supporting medium consisting of microparticles of calcium carbonate, and the microparticles enable the development thereon of an adherent aerobic bacterial flora. A plant that implements the process of thermophilic aerobic treatment of concentrated organic waste water is also described.