CONSERVATION OF ENVIRONMENT WITH EMPHASIS ON CONTROL OF HAZARDOUS SUBSTANCES

Polychlorinated dibenzo[b, e][1, 4]dioxins (PCDDs) and Polychlorinated dibenzofurans (PCDFs), called as "the dioxins" in general and Polychlorinated biphenyl (PCB) are well-known to be the most toxic substances and to be difficult to decompose in the natural environment because of their stable properties, and to be polluting the environment globally and accumulating in the animals and human body. This paper summarized and overviews the sources, the generation mechanism, some analytical problems, and the emission control of dioxins from municipal solid waste (MSW) incinerators based on the research results of the author's group and the investigation and available literature data, and describes the thermal destruction of waste liquid PCB. Incineration of wastes seems to be one of the major sources of "the dioxins" with serious public concerns. Main results of research as follows, 1) concentrations of dioxins in the flue gas and fly ash from the MSW incinerators are measured and it makes clear that the dioxins are mainly synthesized through the cooling zone of waste heat boiler and the formation of dioxins takes occur in the electrostatic precipitator when the inlet temperature of gas is above 200-degrees-C. It was concluded based on the many researches that the carbon and metals in the fly ash act as the catalyzer of formation of dioxins. 2) The dioxins are also formed through the filter in the sampling procedures kept above 120-degrees-C. The author's group proposed the recommendable sampling and analytical procedures. 3) The generation mechanism are investigated and proposed the emission control methods of dioxins from MSW incinerators. It was indicated that the waste liquid PCB can thermally be decomposed in the high temperature conditions with enough residence time. Based on the investigation, the waste liquid PCB of about 5500 tons was thermally destructed and its results are described.