Radionuclides In Sludge Research Articles

Possible Factors Influencing the Accumulation of Different Radionuclides in Sludge from a Drinking Water Treatment Plant Located in Southern Catalonia Between 2002 and 2018

The drinking water treatment plant (DWTP) in L’Ampolla collects water from the River Ebro. The sludge generated during the water treatment processes applied accumulates some of the radionuclides present in the ingoing water. Gamma spectrometry measurements of the sludge were carried out monthly for a period of 17 years (2002–2018) to evaluate possible factors that might influence the radioactive content. These included the geology, river flow rate, suspended particulate matter, turbidity, water treatment processes, and industrial activities in the area of the river basin. The activity concentrations of 214Pb, 214Bi, 228Ac, 228Ra, and 226Ra from both the 238U and 232Th decay chains decreased significantly from 2012 onwards. This may be related to a change in the water treatment process in the L’Ampolla DWTP, and in particular, that potassium permanganate was no longer added to the raw water from 2011. Other isotopes such as 40K, 7Be, and 234U/238U have not displayed the same behavior, which could support our hypothesis that the accumulation of radium isotopes in the sludge could be influenced by the use and nonuse of permanganate. A number of artificial radionuclides were also determined, which is consistent since L’Ampolla DWTP is located 70 km from a nuclear power plant, and the activities found for some of these radionuclides correlate with its annual liquid discharges into the river. The results therefore indicate that a relationship exists between the different factors in connection with the raw water and the radioactive content of the sludge generated by the plant under study.

Natural and artificial radionuclides in sludge, sand, granular activated carbon and reverse osmosis brine from a metropolitan drinking water treatment plant

Natural and artificial radionuclides in sludge, sand, granular activated carbon and reverse osmosis brine from a metropolitan drinking water treatment plant

Association of naturally occurring radionuclides in sludges from Drinking Water Treatment Plants previously optimized for their removal

The raw water used in Drinking Water Treatment Plants (DWTPs) can present high values of naturally occurring radionuclides. In order to reduce this content, the routine working conditions of DWTPs were successfully modified. This meant that those radionuclides were accumulated in the sludges generated, whose radioactive content was frequently above the exemption levels. It therefore becomes necessary to assess the association of naturally occurring radionuclides in the sludges for their potential use as agricultural fertilizers. Two approaches were studied: (a) the effect of different sequential extraction methods applied to a selected sludge; and (b) the effect of the different contents of inorganic complexes dissolved in the input water on the composition of the sludges generated by two DWTPs with different origins of their input water. Uranium and radium were mainly associated with the carbonated and reducible fractions, while 210Po and 228Th were associated with the residual fraction. There were differences between the two speciation methods, but the order of bioavailable radionuclides was roughly the same: 226Ra≈234,238U>228Th>210Po. The major inorganic complexes content, mainly carbonate, in the raw water affected the radionuclide association. The greater the carbonate content in the raw water, the greater was the association of uranium and radium with the carbonated and easily reducible fractions.

Temporal evolution of radionuclides in sludge from wastewater treatment plants

22 sludge samples were analyzed from three municipal wastewater treatment plants to assess both the occurrence and the temporal behavior of radioactivity during 8 sampling campaigns carried out over the period 2007–2009. As regards natural gamma emitters radionuclides from the natural 238U series (such as 234Th, 214Pb, 214Bi, 210Pb) and the 232Th series (such as 228Ac, 212Pb, 212Bi and 208Tl) and other natural gamma emitters such as 7Be, 210Pbu or 40K were measured. In the case of man-made radionuclides small amounts of 137Cs were found, while significant amounts of 131I were detected in some samples. Correlations were found between radionuclides with the same origin. No seasonal variation for the 238U and 232Th series was found in the studied period but 7Be and 210Pbu showed seasonal variation that was explained by the monthly rainfall. The internal and external hazard indices were calculated and the results indicate that the radiological characteristics of the sludge do not present a significant radiological risk and make them suitable for future applications.

Levels of 131I and Six Natural Radionuclides in Sludge from the Sewage Treatment Plant of Valladolid, Spain

The levels of 131I and six natural radionuclides (238U, 226Ra, 210Pb, 228Ra, 224Ra, and 40K) were determined in sewage sludge samples obtained from an urban wastewater treatment plant that services a medium-sized town in Spain. Secondary treatment of wastewater consisting of anaerobic, anoxic, and oxic stages is collectively called A2O processing. Radio analytical determinations were performed by gamma spectrometry using a high-purity germanium detector. This technique has proven useful in identifying local radioactive pollution. This type of pollution was consistently detected throughout the year, with several increases associated with authorized discharges from hospitals. Finally, we examined the radiation dose that workers are exposed to due to the presence of 131I in the sludge. We found inhalation risk to be negligible, with external radiation as the main source of exposure to 131I.