Sewage Sludge as Inhibitor of the Formation of Persistent Organic Pollutants during Incineration

Abstract

With the objective of suppressing dioxins and furans (PCDD/Fs) emission in municipal solid waste incineration plants (MSWI), different chemical inhibitors have been tested. Among these inhibitors, nitrogen and sulphur compounds can significantly suppress PCDD/Fs formation via de novo synthesis, which gives very interesting results with very little capital investment. In recent years, the possibility of using waste rich in nitrogen and/or sulphur as a source of inhibitor compounds has been considered, and thus has reduced the emissions of pollutants while the waste is treated. The effect of adding sludge from urban sewage treatment plants in three variants has been specially studied: directly mixing the waste, using the decomposition gas of the previously dried sludge, and using the decomposition gas of the sludge together with other inhibitors such as thiourea. Reduction of emissions in laboratory tests using model samples indicated the efficiency to be higher than 99%, using sewage sludge (SS) as an inhibitor whereas, in actual MSWI plants, the efficiency can be as high as 90%.