Radionuclides in wastewater treatment plants: Monitoring of Sicilian plants

Three Sicilian wastewater treatment plants were monitored to assess the occurrence and the behaviour of radionuclides. Two sampling campaigns (screening and long-term) were carried out during which liquid and solid samples have been analysed. It was found that 131| mostly occurred in the samples analysed during the screening campaign (43% of the analysed samples contained 131|). High 131| specific activity was found in the mixed liquor, recycled sludge and dehydrated sludge samples. This finding was mainly due to the tendency of 131| to be associated with solid particles. During the long-term sampling campaign an influence of the sludge retention time (SRT) on the 131| behaviour was found. Increasing the SRT and consequently decreasing the fraction of active organic biomass inside the system, the specific activity of 131| decreases.