Occupational Risk Evaluation of Using Bottom Ash and Fly Ash as a Construction Material

Abstract

As a case study, the potential to use bottom ash and fly ash from a large-sized (120 MW) bubbling fluidized bed boiler (BFB) at the power plant of a fluting board mill were assessed to determine their suitability for use as an earth construction agent. In addition, the extractability of heavy metals in the ashes was determined using artificial sweat and gastric fluids to assess the potential occupational risk from ash handling. Owing to the relatively high total concentration of polycyclic aromatic hydrocarbons (PAHs) [23.0 mg/kg; dry weight (d.w.)], and the extractable concentrations of Mo (3.9 mg/kg; d.w.) and Se (0.2 mg/kg; d.w.) in the fly ash, which exceed the Finnish limit values for materials used in covered earth construction (20 mg/kg; d.w. for PAHs, 0.5 mg/kg; d.w. for Mo, and 0.1 mg/kg; d.w. for Se), the utilization of this ash residue fraction in such structures requires an environmental permit. Because of the high extractability of certain heavy metals in fly ash by using an artificial gastric fluid, e.g., Ba (446 mg/kg; d.w.), V (65.6 mg/kg; d.w.), Zn (100 mg/kg; d.w.), Cu (38.3 mg/kg; d.w.), and As (36.7 mg/kg; d.w.), the careful handling of this ash residue is recommended to prevent the ingestion and penetration of ash particles across the human gastrointestinal tract.