Adaptation of conventional water treatment technologies for organic component removal from liquid radioactive waste: sorption and coagulation mechanisms

Abstract Significant concentrations of artificial radionuclides have been detected in drinking water sources not only in areas contaminated by major radiation accidents, but also in the vicinity of operating nuclear power plants. Therefore, the use of effective, broad-spectrum sorbents produced from readily available Ukrainian raw materials in water treatment and purification technologies should be regarded as a strategically important social measure. However, technologies that rely on oxidation to decompose organic components require the recycling of this process. Other promising methods, such as plasma treatment, photocatalysis, and electrocatalysis, currently lack industrial-scale equipment. Meanwhile, there are established water treatment technologies that, despite their proven effectiveness, have not yet been adapted for the treatment of liquid radioactive waste (LRW). This paper investigates the potential application of conventional water treatment technologies for removing the organic component from LRW at nuclear power plants. By employing sorption (using activated carbon and powdered bentonite), coagulation (with ferric chloride), and filtration. We achieved a 75% removal efficiency of the organic component, as measured by COD(Cr) (dichromate oxidizability). The use of a 20% w/v FeCl₃ solution as a coagulant and activated carbon as a sorbent significantly enhanced the purification process. Reducing the concentration of bentonite had little effect on the degree of LRW purification, whereas increasing its concentration noticeably diminished purification efficiency. Nevertheless, the addition of bentonite as a turbidity agent substantially accelerated coagulation and sedimentation. Conversion models were developed to recalculate COD(Cr) (dichromate oxidizability) indicators into corresponding COD(Mn) (permanganate oxidizability) or total organic carbon (TOC), with prediction accuracy validated by experimental data. It should be noted that using such technologies will significantly reduce water and energy consumption, as well as saving time, all of which is extremely important in Ukraine’s current wartime economic situation.