Total and extractable element concentrations in bed sand material from a medium-sized (32 MW) municipal district heating plant incinerating peat, stumps, sawdust and recycled wood

In Finland, the new limit values of total heavy metal, polychlorinated biphenyl (PCB) and polycyclic aromatic hydrocarbon (PAH), as well as the extractable heavy metal, dissolved organic carbon (DOC), fluoride, sulphate, and chloride concentrations for bed sand material used as an earth construction agent came into force in June 2009. The total heavy metal (i.e. Cd, Cu, Pb, Cr, Zn, As, V, Ba and Mo) concentrations in the studied bed sand material were clearly lower than the current Finnish limit values for the maximum allowable heavy metal concentrations for materials used as an earth construction agent. However, the extractable concentration of Ba (24.6 mg kg−1; d.w.) in the bed sand material exceeded the limit value for covered structures (20 mg kg−1; d.w.). However, in Finland, the competent environmental authority may relax the maximum limit values up to 30% in certain circumstances. Therefore, if, the environmental authority relaxes the maximum limit value for the extractable concentration of Ba by up to 30% to the value of 26 mg kg−1 (d.w.) for covered structures, the extractable concentration of Ba (24.6 mg kg−1; d.w.) in the bed sand material is below this relaxation.

Research Highlights
► The extractable concentration of Ba exceeded the limit value for covered structures.
► The environmental authority may relax the limit value by up to 30%.
► The extractable concentration of Ba is below this relaxation (26 mg kg−1; d.w.).
► The BFB bed sand material is a therefore a potential earth construction material.