Bottom ash (BA) is the main residue left by municipal solid waste incineration (MSWI). As the circular economy is strengthened, the use of BA in civil engineering is increasing, but its successful use is hampered by heavy metal leaching. In this study, we investigated the influence of natural weathering (6 months) on the stabilization of heavy metals (Cu, Zn, and Pb) with different particle sizes in MSWI BA. Natural weathering is the most popular and cost-effective treatment method for BA. During this process, calcium carbonate (CaCO3) is produced, which causes a reduction in heavy metal leaching. We used the following methods in the analysis: The fractionation of BA, XRF, and XRD; an extraction test (LST EN 12457-2:2003); and AAS. The results showed that the concentrations of all elements in BA decreased during natural weathering. An analysis of the mineralogical composition showed a very high (>20%) content of calcium carbonate (CaCO3). The calcium carbonate content increased by 3.2% during weathering because the Ca(OH)2 in fractions <5.6 mm and <40.0 mm was hydrolyzed to CaCO3. Our analysis showed that the metal concentrations (Cu and Pb) in untreated MSWI bottom ash eluate exceeded the limit values, and thus it cannot be used in civil engineering. After three months of stabilization, the heavy metal concentrations were less than the limit values.
Abstract. Municipal solid wastes incineration (MSWI) is an important part of the waste management systems in many European countries. Incineration process generates two main by-products: fly ash (FA) and bottom ash (BA). Bottom ash is composed of a variety of oxides, heavy metals and salts. Landfilling of untreated (fresh) BA can cause soil, surface and ground water contamination problems, because atmospheric precipitation in BA formed leachate, which contains of various materials. In this study investigates the influence of natural weathering to heavy metals leaching from BA. Leaching tests of bottom ash were carried out in 6 months, leachate samples were taken at 12 times (every 2 weeks). Heavy metals (Pb, Cu) concentrations were determined by atomic adsorption of spectral analysis method. The research shown, that the highest lead and copper concentration was determinated in 2 weeks weathered bottom ash leachate, respectively was 0.613 mg l -1 and 0.068 mg l -1 . In both cases the concentration of Pb (0.010-0.052 mg l -1 ) and Cu (0.010-0.018 mg l -1 ) became almost stable after 12 weeks. Can be concluded, that short-term (3 months) natural weathering is sufficient time for stabilise MSWI bottom ash and heavy metals (Cu and Pb) leaching. After 18-24 weeks heavy metals concentrations stabilized and remained almost constant.
Komunalinių atliekų deginimo metu susidaro du pagrindiniai proceso atliekų srautai – lakieji ir dugno pelenai. Pastarųjų sudėtyje gausu oksidų, druskų ir metalų. Šviežių dugno pelenų panaudojimas ar deponavimas gali sukelti aplinkos komponentų užtaršos problemas, nes veikiant atmosferos krituliams susidaro įvairių medžiagų turintis filtratas. Šiame darbe tiriama meteorologinių sąlygų įtaka dugno pelenuose esančių sunkiųjų metalų išsiplovimui. Eksperimentiniams tyrimams atlikti buvo sukonstruotas laboratorinis stendas, parinkta bei sudaryta tyrimų metodika. Tyrimai atlikti esant nepastovioms (lauko) meteorologinėms sąlygoms. Dugno pelenų išsiplovimo tyrimai buvo atliekami 3 mėn., filtrato mėginiai imti 6 kartus (kas 2 sav.). Sunkiųjų metalų (Pb, Cu,) koncentracijos filtrate nustatytos atominės adsorbcijos spektrinės analizės metodu. Atlikus tyrimus nustatyta, kad švino koncentracija mėginiuose yra 0,020–0,355 mg/l. Didžiausios Pb koncentracijos nustatytos po 2 ir 8 sav. Didžiausia vario koncentracija (0,0663 mg/l) nustatyta 2 sav. sendintų pelenų filtrate. Komunalinių atliekų deginimo dugno pelenams išbuvus lauke 6–12 sav. vario koncentracija buvo 0,0207–0,0243 mg/l.
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