Distribution of polycyclic aromatic hydrocarbons and polychlorinated dibenzo-p-dioxins/dibenzofurans in ash from different units in a municipal solid waste incinerator.

Polycyclic aromatic hydrocarbons (PAHs), polychlorinated-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are some of the major organic contaminants emitted in municipal solid waste incinerators (MSWIs). The distribution of PAHs and PCDD/Fs in different MSWI unit ashes, including bottom residue (BR), fly ash pit (FAP), fabric filter (FF), semi-dryer absorber (SDA), economizer (EC) and super heater (SH), has seldom been discussed. Average PAHs content in ash samples from BR, FAP, FF, SDA, EC and SH were found to be 0.020, 0.237, 0.234, 0.125, 0.037 and 0.034 µg TEQ g(-1), respectively. In addition, the range of total emission factor from different unit ashes varied between 0.30-13.85 mg TEQ tonne(-1) of waste, low molecular weight compounds (2~3-ring) being the dominant species. Furthermore, PAHs in ashes were mainly found in BR (41%) and FAP (31%). The FAP ash included 18% of PAHs coming from FF ash. On the other hand, PCDD/Fs content in BR, FAP, FF, SDA, EC and SH was found to be 0.0329, 1.1589, 1.2807, 0.1476, 0.6868 and 0.0921 ng I-TEQ g(-1), respectively. PCDD/ Fs emission factors in this study ranged between 1.029-67.740 µg I-TEQ tonne(-1) of waste, most PCDD/Fs being present in FAP (55%). The FAP ash included 33% of PCDD/Fs coming from FF ash. Therefore, PCDD/Fs content in FAP and FF exceeded the legal limit of 1 ng I-TEQ g( -1); therefore, a solidification process is necessary before landfilling in Taiwan.