Abstract
The objective of this study is to clarify the characteristics of dioxins discharged from liquid organic waste incineration facilities at Nagasaki University. The dioxin concentrations in flue gas, burned ash, and discharged water generated at the facilities were measured once a year and data for 13 years were analyzed. Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (DL-PCBs), which have non-zero toxic equivalency factors (TEF), were selected as important dioxins, and toxic equivalent quantities (TEQ) were calculated using the TEF of 29 congeners. Although the amount of liquid organic waste at the university increased by approximately 1.6 times over the investigation term, it was confirmed that the TEQ values were much lower than the corresponding waste standards, even when the data from 2005, in which there was an accident that caused incineration to be stopped, was included. Considering the flue gas only, the TEQ value for 2005 was much higher than for other years. It is thought that the combustion temperature during the accident gave rise to conditions conductive to the generation of dioxins. It was shown that dioxin concentrations did not clearly correlate with the concentrations of monitored compounds. The contribution pattern of the 29 congeners to the dioxin concentration in the flue gas was very similar to that of the burned ash, although the profile of the discharged water was quite different. Unlike in the case of the concentration profile, it was found that the TEQ profile was almost the same for all sample types. The profile of the main dioxin congeners was compared with a previous report that considered the use of an indicative congener. This showed that the TEQ values of the flue gas and the burned ash estimated using only the indicative congener were near to the normal TEQ values if 2,3,4,7,8-PeCDF was detected and more than 14 kinds of congeners were detected.
