Development of groundwater treatment method using radiation-induced graft polymerization adsorbent at the Mizunami Underground Research Laboratory; Annual report for 2008 fiscal year (Joint research)

Iyatomi, Yosuke ; Hoshina, Hiroyuki; Seko, Noriaki; Shimada, Akiomi; Ogata, Nobuhisa ; Sugihara, Kozo; Kasai, Noboru; Ueki, Yuji; Tamada, Masao

The concentrations of fluorine (7.2-10 mg/L) and boron (0.8-1.5 mg/L) dissolved in groundwater pumped from the shafts during excavation of the Mizunami Underground Research Laboratory (MIU), Tono Geoscience Centre, must be reduced to the levels below the environmental standards for fluorine: 0.8mg/L and boron: 1 mg/L. As well, collaborative research on groundwater treatment to remove fluorine and boron started in 2006 between the Environmental and Industrial Materials Research Division, Quantum Beam Science Directorate and the Tono Geoscientific Research Unit, Geological Isolation Research and Development Directorate. This is because the Quantum Beam Science Directorate has synthesized fibrous adsorbents with radiation-induced graft polymerization and applied adsorbents to collect rare metals dissolved in hot springs and sea water. The results of previous testing indicate that the adsorbent was able to remove more than 95% of the boron and fluorine and that performance of adsorbent for boron removal was better than the performance using ion-exchange resin. It was also apparent that the pH of groundwater had an influence on the performance of the adsorbent with respect to boron removal. Therefore we reran the recycling test using groundwater from the neutralization tank at the groundwater treatment facility. The results indicated that the performance of the adsorbent using neutral groundwater for boron removal was higher than using uncontrolled groundwater. However the bed volume (BV) with recycled adsorbent decreased compared to first use. It is thought that sulfur added at the groundwater treatment facility was retained by the adsorbent despite elution, and affected the performance such that repeat usage resulted in decreased efficiency. In addition, it is considered that the goals established in the first year compared to the results obtained to date, including the status of waste water treatment at the MIU, and summarized the results in this development.