Improvement of Dredged Sediment Using Air Bubbles or Carbonized Sewage Sludge

    Published: Nov 2012

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    The geotechnical utilization of dredged sludges has been an important issue in Japan, with the aims of utilizing limited natural resources efficiently and minimizing the volume of wastes to be disposed of. Prior to their reuse, sludge materials with a high water content might be subjected to some physical/chemical treatment such as dehydration and/or stabilization/solidification in order to improve their engineering properties and achieve the required durability and strength of earthen materials. These technologies usually require either or both treatment plants (e.g., dehydrator) and chemical agents (e.g., cement) and consume a certain amount of materials and energy. In this study, two environmentally friendly improvement methods for dredged sludge are newly proposed. The first one allows the use of micro air bubbles to enhance water evaporation by air drying without any dramatic change in soil properties. This method can also have the advantage of low cost. Liquid limit tests have been conducted on specimens with various initial water contents that were mixed with and without air bubbles and cured for certain periods. Under conditions simulating air drying in the field, the water content decreased more rapidly in the sludge mixed with air bubbles than the sludge without air bubbles. A decrease in water content induced by mixing with air bubbles also contributed to the lowered liquid limits of the dredged sediments, which implies a lower water holding capacity. In another method, porous carbonized sewage sludge (CSS) with water absorption and deodorization capacities is employed not only to reduce the water content of the soil matrix of the sludge but to reduce the level of ammoniacal odor that is caused by the cement stabilization of organic-rich sediment. Experimental results indicate that CSS showed the expected performance to a certain degree and prove the validity of this method for the improvement of soft clayey soils.


    dredged sludge, water content, air bubbles, carbonized sewage sludge

    Author Information:

    Inui, Toru
    Kyoto Univ., Kyoto,

    Ikeda, Kazuki
    Kyoto Univ., Kyoto,

    Katsumi, Takeshi
    Kyoto Univ., Kyoto,

    Mizuno, Katsumi
    Daiko Kogyo Co. Ltd., Osaka,

    Kamon, Masashi
    Kagawa National College of Technology, Takamatsu,

    Committee/Subcommittee: D18.25

    DOI: 10.1520/STP104301

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