contaminated MSW. By modifying coprecipitation conditions according to solution
matrix, Cs removal rates of higher than 95 % could be obtained.
Keywords Cesium • Ferrocyanide • Metal • Municipal solid waste • Oxalic acid
• pH
29.1 Background and Objectives
The estimated sustainable life period of the existing final disposal sites for municipal solid wastes (MSW) in Japan was only 18 years as of the end of FY2008.
Therefore, waste avoidance, waste volume reduction, and recycling of MSW have
been a national policy. However, the Fukushima Daiichi Nuclear Power Plant
(F1) accident has created an entirely new dimension in environmental pollution
problems. Because waste incineration and water treatment are, by their nature, the
processes that concentrate pollutants such as radioactive cesium (rad-Cs) in ashes
and sludge, MSW containing high concentrations of rad-Cs are produced in some
areas where high atmospheric deposition of rad-Cs occurred in the aftermath of the
F1 accident. As a result, recycling of MSW as concrete material and compost has
become difficult, and their reuse has been often prevented because of public
opposition even when rad-Cs concentrations in the wastes are below the clearance
level (100 Bq/kg). Most of the citizens in the affected area are in hard opposition to
disposal of rad-Cs-containing wastes even if radioactivity of the wastes is below the
governmental limit for their disposal in landfills with leachate collection systems
(i.e., 8,000 Bq/kg of Cs-134 + Cs-137). As the result, treatment residues are now
piling up in many treatment facilities in some area, which may eventually jeopardize the treatment itself and exert serious negative impacts to everyday life. For
example, sewage facilities in Fukushima Prefecture stored 74,401 t of dewatered
sludge, molten slug, and incinerator ashes as of May, 2014. Therefore, suitable
technologies to reduce the volume of such wastes or to decontaminate rad-Cs at low
cost are urgently required.
Private companies and agencies have been working on sludge volume reduction
through drying combined with granule processing [1] with the purpose of alleviating storage problems at treatment facilities. High-temperature combustion of sludge
with an additive for controlling basicity of incineration material also proved
effective in condensing rad-Cs in fly ash. The cost of this technique, however,
was high and would be justified only when a very strong social need for sludge
volume reduction exists [2]. Another tested technique in this regard is extraction of
sewage by hot 0.1 M oxalic acid followed by recovery of the extracted rad-Cs by
zeolite [3]. The cost of the oxalic acid method is considered acceptable for largescale sewage treatment facilities, although waste volume reduction is dependent on
the amount of zeolite necessary to remove Cs from the extract. The Cs distribution
factor value (ml/g) reported for zeolite was a few thousand whereas the values for
ferrocyanide (Fer) compounds determined by the in situ Fer coprecipitation method
330
Y. Fujikawa et al.
matrix, Cs removal rates of higher than 95 % could be obtained.
Keywords Cesium • Ferrocyanide • Metal • Municipal solid waste • Oxalic acid
• pH
29.1 Background and Objectives
The estimated sustainable life period of the existing final disposal sites for municipal solid wastes (MSW) in Japan was only 18 years as of the end of FY2008.
Therefore, waste avoidance, waste volume reduction, and recycling of MSW have
been a national policy. However, the Fukushima Daiichi Nuclear Power Plant
(F1) accident has created an entirely new dimension in environmental pollution
problems. Because waste incineration and water treatment are, by their nature, the
processes that concentrate pollutants such as radioactive cesium (rad-Cs) in ashes
and sludge, MSW containing high concentrations of rad-Cs are produced in some
areas where high atmospheric deposition of rad-Cs occurred in the aftermath of the
F1 accident. As a result, recycling of MSW as concrete material and compost has
become difficult, and their reuse has been often prevented because of public
opposition even when rad-Cs concentrations in the wastes are below the clearance
level (100 Bq/kg). Most of the citizens in the affected area are in hard opposition to
disposal of rad-Cs-containing wastes even if radioactivity of the wastes is below the
governmental limit for their disposal in landfills with leachate collection systems
(i.e., 8,000 Bq/kg of Cs-134 + Cs-137). As the result, treatment residues are now
piling up in many treatment facilities in some area, which may eventually jeopardize the treatment itself and exert serious negative impacts to everyday life. For
example, sewage facilities in Fukushima Prefecture stored 74,401 t of dewatered
sludge, molten slug, and incinerator ashes as of May, 2014. Therefore, suitable
technologies to reduce the volume of such wastes or to decontaminate rad-Cs at low
cost are urgently required.
Private companies and agencies have been working on sludge volume reduction
through drying combined with granule processing [1] with the purpose of alleviating storage problems at treatment facilities. High-temperature combustion of sludge
with an additive for controlling basicity of incineration material also proved
effective in condensing rad-Cs in fly ash. The cost of this technique, however,
was high and would be justified only when a very strong social need for sludge
volume reduction exists [2]. Another tested technique in this regard is extraction of
sewage by hot 0.1 M oxalic acid followed by recovery of the extracted rad-Cs by
zeolite [3]. The cost of the oxalic acid method is considered acceptable for largescale sewage treatment facilities, although waste volume reduction is dependent on
the amount of zeolite necessary to remove Cs from the extract. The Cs distribution
factor value (ml/g) reported for zeolite was a few thousand whereas the values for
ferrocyanide (Fer) compounds determined by the in situ Fer coprecipitation method
330
Y. Fujikawa et al.