Characteristics of elements in waste ashes from a solid waste incinerator in Taiwan

Incineration, one of the most effective methods used to treat solid wastes, reduces the volume of solid wastes significantly and enables recovery of thermal energy. However, during this waste treatment, a small amount of heavy metals can be present in the form of fly ash or vapor in the flue gas, becoming a threat to human health and other living organisms once emitted into the environment. This study focuses on the characteristics and behavior of elements contained in the combustion residues and their impact on various wastes at Taiwan's municipal solid waste incinerator (MSWI). Three kinds of waste, municipal solid waste (MSW), industrial waste (IW), and biomass waste (BM), were analyzed to obtain their physical properties and elemental composition before incineration. The combustion residues were collected with a sampler at various locations such as the furnace bottom, a heat economizer, a semi-dry scrubber, a bag-house filter and a gas stack. Twenty-one elements were determined to establish the actual mass fraction and to estimate the possible impact on the environment. Owing to its volatility, Cd was found in high concentrations in bag-house filter ash. In addition, the mass fraction of Zn, As, Pb, Sb and V in bag-house filter ash was found greater than 20% for the three kinds of wastes. Iron (Fe) content was found to be high in MSW, S, Cd, Ni, Pb and Sb content were high in IW and Se content was high in BW.