Radioactivity in sludge

As part of the Environmental Radiation Surveillance Programme, the sludge at Viikinmäki wastewater treatment plant in Helsinki is analyzed, mainly to monitor the presence of man-made radionuclides. Many of the radionuclides in the environment can be detected from the sludge used in a wastewater treatment plant, as during the purification process several radionuclides present in wastewater are concentrated.

Radionuclides were detected from the sludge in Viikinmäki wastewater treatment plant, the sources of which include the Chernobyl accident, the medical use of radioactive isotopes and nature. Analyzing the sludge also gives information about the migration of radionuclides in the natural environment.

The Viikinmäki wastewater treatment plant was taken into use in 1994. In addition to wastewater from Helsinki, the plant also processes wastewater from eastern and central Vantaa, Kerava, Tuusula, Järvenpää, Sipoo, southern Mäntsälä, and Pornainen.  The samples from the raw sludge and digested dried sludge at the wastewater treatment plant are taken four times a year for an analysis of radionuclides emitting gamma radiation.

The excretions of the patients treated at cancer clinics and isotope units of hospitals using radionuclides are processed at Viikinmäki wastewater treatment plant. Treatments are usually given on certain days, so the emissions are released into wastewater at uneven intervals. Therefore the concentrations of nuclides originating from hospitals in the sludge vary substantially. The radionuclides used in hospitals are I-131, Lu-177 and Tl-201. The Cs-137 originates from the Chernobyl accident, while U-238 is a naturally occurring radioactive material in water.

Radionuclides emitting gamma radiation in the raw sludge at Viikinmäki wastewater treatment plant Bq/kg per dry weight in 2019.

Date of sampling 131I 137Cs 177Lu 201Tl 238U
9.4.2019 1800 ± 12% 3.7 ± 16% 1700 ± 16% 72 ± 14% 410 ± 16%
1.10.2019 1900 ± 9% 3.4 ± 24% 1500 ± 14% 120 ± 12% 250 ± 36%

 

Radionuclides emitting gamma radiation in the dried sludge at Viikinmäki wastewater treatment plant Bq/kg per dry weight in 2019.

Date of sampling 131I 137Cs 177Lu 201Tl 238U
9.4.2019 240 ± 12% 5.9 ± 20% 1700 ± 16% 15 ± 14% 690 ± 18%
1.10.2019 190 ± 9% 3.7 ± 16% 1400 ± 14% 8.8 ± 36% 530 ± 20%

 

Radionuclides emitting gamma radiation in the raw sludge at Viikinmäki wastewater treatment plant Bq/kg per dry weight in 2018.

Date of sampling 131I 137Cs 177Lu 201Tl 238U
6.3.2018 2400 ± 10% 3.1 ± 14% 1800 ± 16% 44 ± 12% 330 ± 16%
27.9.2018 2200 ± 12% 2.7 ± 24% 3300 ± 16% 50 ± 14% 180 ± 26%

 

Radionuclides emitting gamma radiation in the dried sludge at Viikinmäki wastewater treatment plant Bq/kg per dry weight in 2018.

Date of sampling 131I 137Cs 177Lu 201Tl 238U
6.3.2018 560 ± 10% 4.9 ± 12% 2100 ± 14% 13 ± 12% 480 ± 16%
27.9.2018 270 ± 10% 4.1 ± 16% 1400 ± 15% 7.2 ± 17% 310 ± 14%

 

Contact

Contact

  • Vaaramaa Kaisa
    Head of Laboratory / MIT tel. +358975988521