The plant for thermal hydrolysis and digestion of sewage sludge at the municipal sewage treatment plant in Tarnow was described. In 2014-2016, about 18 400 t of dry solid sewage sludge were produced. After the installation of thermal hydrolysis and digestion was started in 2017, the amt. of sludge was reduced by more than 36% in dry solids, and more than 52% in total, when compared with quantities processed in 2014-2016.