The article presents the results of experimental studies on the treatment with Praestol flocculants of actual sludges of industrial wastewater generated during the chemical treatment of a metal surface. The technological parameters of the operation of the sludge thickening equipment have been established: the optimal dose of flocculant Praestol 2500 for the treatment of industrial wastewater sludges is 0.1 g/kg; the specific productivity of gravitational thickeners on the dry matter of the sludge is 20-30 kg/(h ⋅m2).