Removal of technetium from solution by algal flagellate Euglena gracilis

Based on limited data for the removal of radioactive (99)Tc by freshwater phytoplankton, it has been thought that phytoplankton are unsuitable for remediation of (99)Tc-contaminated waters. This work sought to verify the validity of this assumption by studying the removal of (99)TcO(4)(-) by freshwater and brackish water phytoplankton. The phytoplankton used were Euglena gracilis, Chlamydomonas pulsatilla, Chlorella vulgaris, and Spirulina platensis. Each of them was incubated for 63 d, and the removal of (99)Tc from solution was periodically determined. Significant removal of (99)Tc was observed only for E. gracilis, and the maximum removal was 70% of the total (99)Tc added. The killed cells of E. gracilis, however, removed hardly any (99)Tc. When E. gracilis cells were washed with fresh culture medium, only 13% of the total (99)Tc was desorbed. These results suggested that intracellular uptake of (99)Tc by E. gracilis occurred. These results are the first documented example of significant removal of (99)Tc by planktonic microalgae.