The bottom ash and fly ash from the co-combustion of wood residues and peat at a bubbling fluidised bed boiler（296 MW） contained only quartz（SiO_2）, microcline（KAl Si_3O_8） and albite（NaAlSi_3O_8）. Thus, X-ray...The bottom ash and fly ash from the co-combustion of wood residues and peat at a bubbling fluidised bed boiler（296 MW） contained only quartz（SiO_2）, microcline（KAl Si_3O_8） and albite（NaAlSi_3O_8）. Thus, X-ray powder diffraction（XRD） was not useful for clarifying the difference in the release of associated heavy metals from ash matrices. In order to assess the release of heavy metals from ashes under changing environmental conditions, they were sequentially extracted and fractionated by the BCR-procedure into acid soluble/exchangeable（CH_3COOH）, reducible（NH_2OH-HCl） and oxidizable（H_2O_2/CH_3COONH_4） phases. The CH_3 COOH extractable fraction in conjunction with the total heavy metals concentrations were used to calculate the risk assessment code values for heavy metals leaching from the ash matrix. The leaching studies indicate that the heavy metals in the bottom ash and fly ash are bound to different fractions with different strengths. From the environmental and utilization perspectives, heavy metals in ashes posed different levels of environmental contamination risk. Only As in the bottom ash posed a very high risk. High risk metals were Cd in the bottom ash as well as As, Cd and Se in the fly ash.展开更多
In this study,we have determined the main important physical and chemical properties as well as the heavy metal concentrations of the primary and secondary wastewater treatment sludge from a pulp and board mill comple...In this study,we have determined the main important physical and chemical properties as well as the heavy metal concentrations of the primary and secondary wastewater treatment sludge from a pulp and board mill complex located in Finland in order to evaluate the utilization of these by-products as a soil amendment agent or a fertilizer product.Easily soluble Ca,Mg,K,Na,P and S concentrations in the sludges were extracted by ammonium acetate(CH3COONH4)and easily soluble Cu,Mn and Zn concentrations by CH3COONH4+Na2EDTA.For the determination of total nutrient and total heavy metal concentrations in sludges,they were digested using aqua regia(3 mL HCl+9 mL HNO3).The total heavy concentrations in the primary sludge were lower than the Finnish heavy metal limit values for fertilizer products.In the secondary sludge,all other total heavy metals than the total Cd concentration(4.8 mg/kg;d.w.)were lower than the heavy metal limit values for fertilizer products.Due to the low total heavy metal concentrations,which were lower than the Finnish limit values for fertilizer products,the primary sludge is a potential fertilizer.Although the total Cd concentration(4.8 mg/kg;d.w.)in the secondary sludge exceed the limit value of 1.5 mg/kg(d.w.)for fertilizer products,this residue may be used as a soil improver,a growing media or as a fertilizer product in landfill sites or in other closed industrial areas,because the Finnish limit values for fertilizer products are not applied at these sites.展开更多
文摘The bottom ash and fly ash from the co-combustion of wood residues and peat at a bubbling fluidised bed boiler（296 MW） contained only quartz（SiO_2）, microcline（KAl Si_3O_8） and albite（NaAlSi_3O_8）. Thus, X-ray powder diffraction（XRD） was not useful for clarifying the difference in the release of associated heavy metals from ash matrices. In order to assess the release of heavy metals from ashes under changing environmental conditions, they were sequentially extracted and fractionated by the BCR-procedure into acid soluble/exchangeable（CH_3COOH）, reducible（NH_2OH-HCl） and oxidizable（H_2O_2/CH_3COONH_4） phases. The CH_3 COOH extractable fraction in conjunction with the total heavy metals concentrations were used to calculate the risk assessment code values for heavy metals leaching from the ash matrix. The leaching studies indicate that the heavy metals in the bottom ash and fly ash are bound to different fractions with different strengths. From the environmental and utilization perspectives, heavy metals in ashes posed different levels of environmental contamination risk. Only As in the bottom ash posed a very high risk. High risk metals were Cd in the bottom ash as well as As, Cd and Se in the fly ash.
文摘In this study,we have determined the main important physical and chemical properties as well as the heavy metal concentrations of the primary and secondary wastewater treatment sludge from a pulp and board mill complex located in Finland in order to evaluate the utilization of these by-products as a soil amendment agent or a fertilizer product.Easily soluble Ca,Mg,K,Na,P and S concentrations in the sludges were extracted by ammonium acetate(CH3COONH4)and easily soluble Cu,Mn and Zn concentrations by CH3COONH4+Na2EDTA.For the determination of total nutrient and total heavy metal concentrations in sludges,they were digested using aqua regia(3 mL HCl+9 mL HNO3).The total heavy concentrations in the primary sludge were lower than the Finnish heavy metal limit values for fertilizer products.In the secondary sludge,all other total heavy metals than the total Cd concentration(4.8 mg/kg;d.w.)were lower than the heavy metal limit values for fertilizer products.Due to the low total heavy metal concentrations,which were lower than the Finnish limit values for fertilizer products,the primary sludge is a potential fertilizer.Although the total Cd concentration(4.8 mg/kg;d.w.)in the secondary sludge exceed the limit value of 1.5 mg/kg(d.w.)for fertilizer products,this residue may be used as a soil improver,a growing media or as a fertilizer product in landfill sites or in other closed industrial areas,because the Finnish limit values for fertilizer products are not applied at these sites.
