Generation characteristics of polybrominated and polychlorinated dibenzo-p-dioxins/furans (PBDD/Fs and PCDD/Fs) under varying incineration conditions of municipal solid waste

Municipal solid waste incinerators (MSWIs) are deemed important sources of polychlorinated and polybrominated dibenzo-p-dioxin/furans (PCDD/Fs and PBDD/Fs). However, compared to PCDD/Fs, the emission characteristics of MSWI-derived PBDD/Fs have been rarely studied. Here we selected a long-term operating MSWI, investigated the generation of PBDD/Fs under varying incineration conditions within the normal range, and compared them to those of PCDD/Fs. Generally, PBDD/Fs exhibited mass-based emission factors (mass-EFs) one order of magnitude higher than those of PCDD/Fs and were predominantly released via slag, as were PCDD/Fs, though at lower percentages. Both PBDD/Fs and PCDD/Fs showed significant changes in emissions with the variations in waste load, O₂ content, and waste composition, particularly PBDD/Fs. Comparatively, furnace-derived PBDD/Fs demonstrated heightened sensitivity to waste load and composition, whereas PCDD/Fs were primarily influenced by O₂ levels, followed by waste composition; PCDD/Fs consistently exhibited increasing mass-EFs under unconventional conditions and PCDD/Fs in filtered fly ash were highly sensitive to all the three variables, while filtered PBDD/Fs remained insensitive to these conditions. Data comparison between raw flue gas and filtered fly ash indicated secondary generation of PBDD/Fs and PCDD/Fs during gas purification, as well as the insufficient dioxin-trapping efficiency of bag filters, particularly for PBDD/Fs. Therefore, MSWI-derived PBDD/Fs and dioxins in slag and other MSWI-derived wastes warrant significant attention.