Resource Disposal and Products of Fly Ash from Domestic Waste Incineration in Zhejiang Province, China: Migration and Change of Hazardous Heavy Metals

At present, domestic waste incineration fly ash is classified as hazardous waste. The technical hurdle of fly ash detoxification and resource usage must be overcome in order to effectively utilize fly ash resources. In this study, we investigate the migration and transformation of heavy metal contaminants in the course of utilizing domestic waste incineration fly ash resources through the technology pathway of low-temperature pyrolysis, cyclic rinsing, and evaporation crystallization. Firstly, a comparative analysis was conducted on the fly ash (FA), pyrolysis ash (PA), and water-washing ash (WA) resulting from domestic waste incineration, revealing 24 types of metals, 3 types of non-metals, and 8 types of oxides. We observed the variations in heavy metal concentrations as well as the acidity and alkalinity in three types of ash resulting from the regenerated salt (RS) and incineration processes. Moreover, we analyzed the changes in heavy metal levels and acidity and alkalinity of treated saline water (TSW) and industrial brine (IB), which originate from the fly ash treatment process. The study’s results have confirmed that the heavy metal content in RS was below the detection limit following resource treatment. In addition, the regenerated salt product is determined to be a CaO-SiO₂-Al₂O₃-Fe₂O₃ system, which enables the utilization of fly ash as a valuable resource. Notably, there were significant changes observed in heavy metal content in TSW and IB. Continued attention needs to be paid to the potential risk of environmental contamination from heavy metals and dioxins in FA infiltration. This research will prove beneficial in assessing resource utilization potential of products subjected to environmentally sound incineration fly ash treatment.