Migratory Behavior Of Major Contaminant In The Thermal Treatment Process Of Sludge

As the extension of sewage treatment, the output of municipal sludge is increasing constantly. And sludge treatment and disposal has been an important topic of environmental science and municipal engineering that needs to be resolved as soon as possible. The transformation and release to the environment of several kinds of toxic substance in the sludge are important environmental problem in the process of sludge treatment. But there is not enough research on the problems (e.g. migratory behavior and relevant conditions of sludge contaminations in the treatment process). But they are important information on controlling and eliminating secondly pollution in the process of sludge treatment and disposal. This paper is absorbed in making simulation experiment research of the behavior and mechanism of contamination produced in the thermal treatment process. The major conclusions are as follows:There are large amount of trace metal in the sludge. Then we evaluate the potential risk of the metals and the conclusion is that potential risk of Zn and Cr is low, potential risk of Cu and Pb is high and potential risk of Cd, Hg and As is the highest. In the thermal treatment process the content of the metals are transformed to more stable status.Migratory rule of the two substances is related to the temperature directly. The temperature of translation and release from sludge for PAHs is 300-750℃, which is 350-1000℃for PCBs. In the temperature space of 300-750℃, 90% of PAHs is transferred and released. In the temperature space of 350-900℃, 80% of PCBs is transferred and released. In the process there are reactions between different monomers, the situation is complicated, and much more researches are needed.