A method using granulated coal ash for disposal of the sludge carried by tsunami

摘要

Large amounts of sludge and debris accumulated on agricultural and residential areas after the Great EastudJapan Earthquake. Since the sludge carried by the Tsunami has high contents of unstable-form organic matter ???UFOM???ud(burned at 300??C), this sludge is considered to be the origin of malodorous gas generation that affects human activities.udTherefore, disposal of the sludge plays an important role in the reconstruction effort. Previously, it is obvious thatudgranulated coal ash (GCA) comprised of silica (44%), calcium oxide (21%) and aluminum oxide (13%) improves theudorganic condition of sewage sludge. For example, the generation of malodorous gases, e.g. hydrogen sulfide andudammonia, was greatly reduced after mixing GCA with the sewage sludge. In this study, we aim to propose a methodudusing GCA to disposal the sludge carried by Tsunami. For this purpose, changes in organic conditions and malodorousudgas generation of the sludge after mixing GCA are investigated based on laboratory experiments. In the laboratoryudexperiments, the sludge was mixed with GCA, and then was burned at 200??C to 600??C (intervals of 100??C) in 4 hours atudeach temperature step. Furthermore, other experiments were conducted to measure amounts of gas generated from theudsludge in the absence and the presence of GCA. It was found that ignition behaviors of the sludge with and withoutudGCA were different, namely, the ignition loss at 300??C of the sludge mixing with GCA was lower than that of the sludgeudwithout mixing GCA. This ensures that organic conditions (e.g. decreases in amounts of UFOM) of the sludge changesudafter mixing GCA. Moreover, it was also found that malodorous gases did not generate from the sludge mixing withudGCA, indicating that GCA affects the digestion process of organic matter. It is expected that our proposed method isudalso useful for the capitalization of dredged soil and the development of lowland.