Complex treatment of low-level liqiud radioactive waste by nanofiltration

Abstract

The use of surface storage facilities for low-level radioactive waste does not meet modern safety requirements, which is why strategies are being developed to conserve and remediate the affected areas. This paper presents the results of radionuclide purification tests using nanofiltration on waters from the surface storage of uranium-containing sludge at the Novosibirsk Chemical Concentrates Plant. As cleaning the aqueous phase is only possible in summer, this work focuses on the impact of biofouling on the efficiency of filtration membranes. In the initial stage of the study, the selection of a membrane with minimal cell adhesion was conducted. Laboratory experiments on purification using the NanoNF-1812 membrane demonstrated the potential for effective purification (99.1–99.4%) of water from sludge storage basins, removing uranium, ⁹⁰Sr and ¹⁵²Eu. Periodic washing of the membrane with dilute nitric acid ensures a constant filtration rate during long-term operation. Given the low retention capacity of the NF membrane for nitrate ions, the possibility of their biological removal via a mechanical filter containing microbial biofilms has been demonstrated. This filter is filled with sand and has a diameter of 50 mm and a sand layer height of 1 m, with a flow rate of no more than 10 ml/h.