In order to evaluate the effects of several measures on the control of dioxin emissions in the incineration of organic waste liquid, the actual results for 12 years and annual changes in the dioxin concentrations at the Kyoto Institute of Technology were analyzed. Although the college disposal plant is small, the stringent campus standard for dioxin emissions of less than 0.1 ng-TEQ/m
3 (legal standard: 10 ng-TEQ/m
3) has been met for more than a decade. The dilution of chlorine in organic waste liquid by less than 10%, the improvement of the incineration method, and the introduction of catalyst equipment have been effective in reducing dioxin emissions. The catalyst equipment can reduce not only dioxin but also nitrous oxide emissions. The dioxin concentrations in sewage water were 3.576 pg-TEQ/L and 1.741 pg-TEQ/L in 2000 and 2001, respectively, but they declined sharply to 0.215 pg-TEQ/L in 2002. The dioxin concentrations remained around 0.2 pg-TEQ/L from 2002 through 2005, further decreased to 0.031 pg-TEQ/L in 2006 and decreased to 0.006 pg-TEQ/L in 2010, which was about one-six hundredth of that in 2000. The concentrations of PCDDs and PCDFs in 2000 and 2001 were 3.309 pg-TEQ/L (92.5%) and 1.547 pg-TEQ/L (88.9%), respectively, which accounted for the high values. The contributions of PCDDs and PCDFs to total dioxins in sewage water were 80% in 2002 and 2003. In most years after 2004, the contributions of coplanar PCBs were 60%. The dioxins in the sewage water may have been affected by the combustion origin in 2000 and 2001, and its contribution may have decreased after that. The soil dioxin concentration measured in 2000 was around 4 pg-TEQ/g.
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