Removal of radioactive iodine and cesium in water purification processes after an explosion at a nuclear power plant due to the Great East Japan Earthquake.
The presence of radionuclides at five water purification plants was investigated after an explosion at a nuclear power plant hit by the Great East Japan Earthquake on 11 March 2011. Radioactive iodine (¹³¹I) and cesium (¹³⁴Cs and ¹³⁷Cs) were detected in raw water in Fukushima and neighboring prefectures. ¹³¹I was not removed by coagulation-flocculation-sedimentation. ¹³¹I was removed by granular activated carbon (GAC) and powdered activated carbon (PAC) at a level of about 30%-40%, although ¹³¹I was not removed in some cases. This was also confirmed by laboratory-scale experiments using PAC. The removal percentages of ¹³¹I in river and pond waters by 25 mg dry/L of PAC increased from 36% to 59% and from 41% to 48%, respectively, with chlorine dosing before PAC. ¹³⁴Cs and ¹³⁷Cs were effectively removed by coagulation at both a water purification plant and in laboratory-scale experiments when turbidity was relatively high. In contrast, ¹³⁴Cs and ¹³⁷Cs in pond water with low turbidity were not removed by coagulation. This was because ¹³⁴Cs and ¹³⁷Cs in river water were present mainly in particulate form, while in pond water they were present mainly as cesium ions (¹³⁴Cs+ and ¹³⁷Cs+). However, the removal of ¹³⁴Cs and ¹³⁷Cs in pond water by coagulation increased markedly when ¹³⁴Cs and ¹³⁷Cs were mixed with sediment 24 h before coagulation.
Department of Environmental Health, National Institute of Public Health, 2-3-6 Minami, Wako, Saitama 351-0197, Japan. kosaka@niph.go.jp
Koji
K
Kosaka
Mari
M
Asami
Naoya
N
Kobashigawa
Keiko
K
Ohkubo
Hiroshi
H
Terada
Naohiro
N
Kishida
Michihiro
M
Akiba
D002588:Cesium Radioisotopes; D002606:Charcoal / Q000737:chemistry; D060766:Drinking Water / Q000737:chemistry; D055866:Earthquakes; D005107:Explosions; D005374:Filtration; D005427:Flocculation; D007457:Iodine Radioisotopes; D007564:Japan; D055848:Nuclear Power Plants; D018788:Radioactive Hazard Release; D012722:Sewage / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D014875:Water Pollutants, Radioactive / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*
D002588:Cesium Radioisotopes; D060766:Drinking Water; D007457:Iodine Radioisotopes; D012722:Sewage; D014875:Water Pollutants, Radioactive; D002606:Charcoal; D012822:Silicon Dioxide