Radiation impact of ashes from the combustion of bottom sediments in a municipal sewage treatment plant, Czajka, located in Warsaw, Poland

The aim of the present research was to assess the radiological importance of the fly ashes generated from the incineration of sludge from the “Czajka” sewage treatment plant located in Warsaw, Poland. The γ-spectrometry technique was employed for their radiometry. The high purity germanium (HPGe) detector was mathematically energy-efficiency calibrated. The ash samples were measured two times, i.e., after 24 days and after 3 months of storage. Storage was supposed to provide a radioactive equilibrium. Radionuclides from three natural decay series, i.e., uranium–radium, uranium–actinium, and thorium, were detected in the ash samples. Apart from these, ⁴⁰K, ¹³⁷Cs, and ⁷Be were also detected. The indicated levels of radionuclides do not produce radioactive hazards, regardless of the method used for further management.