Evaluation of treatment of gas cleaning residues from MSWI with chemical agents

Abstract

In Japan as in many other countries treatment of Municipal Solid Waste Incinerator (MSWI) fly ash is necessary to obtain a less hazardous material for landfilling (in the context of this paper MSWI fly ash consists of combined electrostatic precipitator ash and air pollution control residues). Ultimately, treatment may lead to potential use of materials. Different treatment processes based on the addition of chemical agents are currently in use or in development in Japan. In this paper, the leaching behaviour of untreated MSWI fly ash and chemically treated fly ash has been studied. The treatment processes involved are: treatment with a chelating agent, phosphate treatment, ferrite treatment. In the characterization of the leaching behaviour of treated and untreated fly ash, which all fall in the category of granular materials, the Japanese leaching test (JUT-13), the Availability Test, a pH dependent leaching test, a redox property test, and the serial batch test under open condition and closed condition from L/S = 2 to 100 are performed. The tortuosity of the compacted materials was tested separately in diffusion tubes using Na-22-tracer. The data obtained from the different tests are placed in perspective to derive conclusions on the environmental properties of the treated wastes under confined conditions and the management control measures that are needed to prevent undesired release of contaminants.