The influence of potassium on the removal of 137Cs by live Chlorella from low level radioactive wastes

Abstract

The objective of this study was to determine the concentration of stable potassium that must be present in a radioactive waste solution to maximize the uptake of radiocesium by algae without a substantial reduction in algal growth. Laboratory cultures of Chlorella pyrenoidosa were grown under continuous culture conditions, and the accumulation of 137Cs by the algae was measured. Potassium ion concentrations below 15 mg/l reduced the growth of C. pyrenoidosa but increased the accumulation multiples for 137Cs. The removal efficiencies, which represent the combined effects of algal growth and accumulation multiples, obtained for 137Cs ranged between 88 and 83 per cent for potassium concentrations between 2 and 15 mg/l but were reduced to less than 20 per cent when the potassium ion concentration was greater than 15 mg/l or less than 2 mg/l.