Controlling the elution of heavy metals from municipal solid waste incineration (MSWI) fly ash using water repellent treatments was studied. Water repellent durability and adaptability to the environment in the final disposal site are required for landfilling water repellent MSWI fly ash. Three types of elution tests, including Ministry of the Environment Notification Test No. 13, were carried out to evaluate the elution suppression effect of water repellent treatments with six fatty acids (oleic acid, linoleic acid, α-linolenic acid, isostearic acid, ricinoleic acid, and erucic acid). All six water repellents could suppress the elution of heavy metals from MSWI fly ash. The elution suppression effects on heavy metals differed depending on the physical and chemical properties of the fatty acids. Water repellent treatments with fatty acids demonstrated effectiveness in the suppression of heavy metal elution in two types of fly ash with different incineration methods and indicated adaptability to the environments of final disposal sites. Based on the results of three types of elution tests, water repellent treatments with fatty acids have the potential to replace conventional methods as new treatments for suppressing the elution of heavy metals from MSWI fly ash.

The water-repellent spray treatment without increasing volume was applied for suppressing the elution of radioactive cesium

The insoluble treatment of radioactive cesium in municipal solid waste incineration (MSWI) fly ash by soil-mixed geopolymer solidification using Akadama soil, which contained abundant amounts of SiO2 and Al2O3, as an activated filler was investigated. The elution rate of radioactive cesium from the geopolymer solidified substance mixed MSWI fly ash and Akadama soil was suppressed to 0.55%, compared to 69.6% for raw MSWI fly ash, using the Japanese No. 13 leaching test. Almost all radioactive cesium in MSWI fly ash was insolubilized by mixing it with Akadama soil, which showed ability as an active filler and adsorption potential for radioactive cesium. A tank leaching test was applied to confirm the long-term stability of the geopolymer solidified substance. The geopolymer solidified substance showed stability in contact with pure water and on ultraviolet radiation. The geopolymer solidifying method using Akadama soil is effective as an insolubilization treatment of radioactive cesium in MSWI fly ash. This method could be applied to other waste materials.

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