Naturally-Occurring Radioactive Materials at water treatment plant on the Poços de Caldas Plateau Region, Brazil

ABSTRACT Oil and gas, mining, among others, are examples of facilities where naturally occurring radioactive materials can be found. This study aims to evaluate the presence of natural radioactive series, especially those of 238U and 232Th, in the water treatment plants of Poços de Caldas City, Minas Gerais. The presence of these series was investigated in samples of raw water, treated water, sludge from decanters, and scale from Parshall gutters. The sludge, input, and scale samples were submitted to the gamma spectrometry technique to determine the 226Ra, 228Ra, and 210Pb radionuclides. For U and Th, ultraviolet visible spectrophotometry was performed, and for the alpha and beta total values, radiochemical separation and subsequent alpha and beta total counts were performed. The results indicate that water samples are within the Ministry of Health Ordinance n° 5 (2017). Due to the different concentrations of radionuclide activity in the sludge, it was not possible to affirm the same order of magnitude with the sediment from the catchments. However, the values are in accordance with those established by the European Union Council for Naturally-Occurring Radioactive Materials. In the scale, the contents of 1192, 1704, and 301 Bq kg−1 were identified for 226Ra, 228Ra, and 210Pb, respectively. In the inputs of aluminum sulfate and calcium hydroxide, no relevant activities were identified. The results obtained in the study can serve as an indicative regarding the need for a more detailed evaluation of the radiological issue in question concerning public water supplies. RESUMO Petróleo e gás, mineração, estações de tratamento de água, entre outros, são exemplos de instalações que podem apresentar Materiais Radioativos de Ocorrência Natural. Neste estudo, objetivou-se avaliar a presença de séries radioativas naturais, especialmente as de 238U e 232Th nas estações de tratamento de água da cidade de Poços de Caldas/MG. Foram investigadas as presenças dessas séries em amostras de água bruta, de água tratada, no lodo dos decantadores e nas incrustações das calhas Parshall, além dos principais insumos utilizados. As amostras de lodo, insumos e incrustações foram submetidas à técnica de espectrometria gama para a determinação dos radionuclídeos 226Ra, 228Ra e 210Pb. Para U e Th, realizou-se espectrofotometria ultravioleta-visível, e para os valores de Alfa e Beta totais foram realizadas separação radioquímica e posterior contagem Alfa e Beta total. Os resultados indi