Abstract
The radioactive fallout emitted by the Fukushima Dai-ichi nuclear power plant has flowed into and accumulated in many wastewater treatment plants (WWTPs) of eastern Japan via sewer systems. The behavior of radioactive materials in four WWTPs in the Tohoku and Kanto regions was investigated to determine the mechanism by which sludge is concentrated during water and sludge treatment processes. In addition, dissolution tests were conducted using contaminated incinerated ash and melted slag derived from sewage sludge to better understand the landfill disposal of contaminated sewage sludge. Results indicate that a large amount of radioactive cesium accumulates in aeration tanks with activated sludge and becomes trapped in concentrated sludge during sludge condensation. Results indicate that the radioactivity of the eluate from 9 out of 12 samples was undetectable; for the remaining 3 samples, the dissolution rates were 0.5-2.7%.
