Integrated management of radioactive strontium contamination in aqueous stream systems

A combination of biomass treatment, fluidized bed/membrane reactor, and a minimum-suspension fluidized bed reactor is proposed to remove strontium cations from aqueous solutions, such as those generated by nuclear reactors. After conducting a series of screening tests, three adsorbents were selected for their suitability and high adsorptive capacity. The proposed combination uses Chlorella vulgaris in a packed column, followed by the fluidized bed/membrane reactor with bentonite powder in suspension. The membrane is primarily used to retain bentonite powder in the reactor. However, the same can be designed to remove additional amount of contaminant from the aqueous stream. The final separation is carried out in a fluidized bed containing resins that are suspended with minimal airflow. In laboratory scale, a flow rate of 600 ml/h was achieved for 30 min during which period the inlet concentration of 100 mg/l was reduced to 2.5 mg/l at the outlet. Bio-encapsulation with thermophilic bacteria and subsequent separation is proposed at this point in order to reduce the concentration to an even lower level. The proposed separation scheme offers an acceptable solution to removing strontium while minimizing the generation of secondary waste.