Possibility of the reuse of drinking water treatment sludge contaminated with radio cesium

Sludge from drinking water treatment plants has been effectively reused as materials for construction, playground soils, and potting mixes. After the 2011 accident at the Fukushima Daiichi Nuclear Power Plant, sludge in the Tohoku and Kanto regions has become contaminated with radiocesium (Cs-134 and Cs-137). Consequently, the storage amount of contaminated sludge in drinking water plants had temporarily increased. The Ministry of Health, Labor and Welfare imposed a voluntary ban on the shipping of the sludge after the accident. On March 2013, they were officially announced that the sludge with less than 400 Bq/kg-wet at the time of shipment from plants is able to reuse as a material of potting mixes. Although resuming the reuse of contaminated sludge may be effective to decrease the amount of storage, it is also necessary to be careful for radiation exposure to the public by the reuse. If the sludge is reused as a material for potting mixes of home gardens, vegetables grown in the mixes may take up the radiocesium. Because sludge, which is artificially separated from surface water by coagulating sedimentation, is a special kind of soil, there are no data about transfer of radiocesium from sludge to plants as far as we know. In our study, leaf vegetables were grown in the potting mix containing contaminated sludge to obtain the soil-to-plant transfer factor of radiocesium. In addition, we studied suppression techniques for the transfer of radiocesium to leaf vegetables. In the poster presentation, we will report the possibility of the reuse of radiocesium- contaminated-sludge on the basis of our data.This work was partially supported by JSPS KAKENHI Grant Number 24590775 and the Agency for Natural Resources and Energy, the Ministry of Economy, Trade and Industry (METI), Japan.International Symposium on Radiological Issues for Fukushima\u27s Revitalized Futur