Controlling the mobility of organic carbon (OC) ant its impact on metal transport from incineration residues
Abstract (Summary)Incineration residues contain both inorganic and organic material. The organic material may affect the mobility of pollutants in e.g. landfills or geotechnical constructions. Limit values of TOC (total organic carbon), determined according to European standard are stipulated to reduce the disposal of organic materials. The European standard methods to determine TOC and DOC (dissolved organic carbon) are evaluated. Factors controlling the mobility of DOC and its effect on metal mobility have also been studied. Determination of TOC according to European standard methods EN 13 137 and EN 1 484 include those carbon fractions that are oxidized during combustion. The definition of TOC as total organic carbon is not equivalent with the analytical result. The European standards on the definition of TOC need revision. Both organic and elemental carbon are oxidized upon heating, and the analytical TOC is thus a sum of organic and elemental carbon present in the sample. Since elemental carbon comprise the major part of the analytical TOC in solid samples of incineration residues, such results will most likely be misunderstood. Revision of the standard method EN 13 137 is recommended to better suit incineration residues. The L/S ratio (the relationship between the mass of liquid and the mass of solid material), excessive carbonation (addition of CO2 until the pH in the solution was stable for 2.5 h) and extraction pH were the main factors controlling the mobility of DOC in incineration bottom ash. Up to ~60 weight-% of the TOC in the bottom ash could be mobilized by controlling these factors (i. e. by using them as parameters). Only a minor part of the TOC (~7 weight-%) in APC residues was extractable with water, indicating a high proportion of elemental carbon. Water-soluble organic compounds may affect the mobility of metals in several ways. The formation of DOC-metal complexes has a direct effect on the metal mobility. Biological degradation of organic material may also affect the metal mobility indirectly due to changes of pH and redox- potential. The complexation capacity of DOC can be used in the development of washing as a pre-treatment process of incineration residues. Excessive carbonation may be useful in a washing process to enhance the separation of metals. Further treatment-oriented investigations of bottom ashes and APC residues are recommended in the development of a washing process of the materials.
School:Luleå tekniska universitet
Source Type:Master's Thesis
Date of Publication:01/01/2006