Laboratory and pilot plant scale study on the removal of radium, manganese and iron from drinking water using hydrous manganese oxide slurry

The presence of naturally occurring radionuclides in drinking water can pose health risks to consumers. Processes of radionuclides removal could result in the accumulation of radioactive elements in a treatment facility, e.g. in filter materials, causing the formation of naturally occurring radioactive materials (NORM). Development of water treatment solutions mostly puts the emphasis on radionuclide removal leaving the generation of (NORM) out of focus. To meet current radiation protection standards, a broader view is necessary -water purification from radionuclides is an optimization assignment between radionuclide removal and accumulation rates. In this work, the injection of HMO slurry into the raw water was tested for simultaneous reduction of the radium, iron, and manganese. Experiments were performed in a lab scale setup and then upscaled to a pilot plant. Laboratory study allowed to optimize the sequence of water treatment steps. The pilot plant was operated over the course of two years demonstrating the removal of Fe and Mn from water as high as 97% and 83%, respectively. The optimal dose of HMO for radium isotopes removal was found to be 1.3 gMnO(2)center dot m(-3). At this dose the concen-trations of Ra-226 and Ra-228 were reduced from 0.358 and 0.470 to 0.048 and 0.043 Bq center dot L-1, respectively. Thereupon, radionuclides content in drinking water was decreased far below the parametric value of 0.1 mSv center dot year(-1). In terms of NORM generation, the studied approach enabled to slow down the accumulation of radionuclides in the filter material prolonging its operation cycle.