RESUMEN
Samples were collected for several weeks to determine the evolution of the 131I (Iodine-131) activity concentration in the inflow water processed at the Salitre wastewater treatment plant (WWTP) in Bogota, Colombia, derived from medical facilities for thyroid cancer diagnosis and treatment. Mass balances on 131I were performed based on the activity rates at the main inflow and outflow of the plant. The 131I activity concentration in the raw water stream was observed to increase significantly from Monday onwards throughout the week, while the daily activity concentration was highest in the morning and then continuously decreased over the rest of the day. The 131I activity concentration in the raw water exceeds the reference value for drinking water and is very close to the discharge limit in water bodies in Colombia. A mass balance calculation showed that the activity rate for the inflow and outflow waters of the WWTP is about 15% of the authorized activity to use for facilities discharging water into the basins and the use of bio-sludge stream for organic fertilizer production does not represent a significant risk of external irradiation for the population. The results of this work are the first of its kind in Colombia, which ones contribute significantly to determinate the radiological risk to public health due to utilization of treated water and sludge, know the 131I behavior in the city sewage systems, and give information for the performance review of regulatory control on 131I management in the country.