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Reaction Fronts in Brick-Sand Layers: Column Experiments and Modeling
No full textAdmixing waste materials with common raw materials in brick production is a promising treatment technology to overcome contamination problems, because organic pollutants are destroyed and inorganic contaminants are thought to be immobilized. During their use in constructions and after the use as part of the demolition masses bricks can be leached by runoff waters and seepage waters. A possible application of recycling crushed bricks consists of their use as a surface layer material on sports grounds or in road construction. To investigate the potential leaching during acidification of a brick-sand layer and the resultant leaching of heavy metals, crushed material from two bricks was examined in several column experiments. Deionized water at pH 4 percolated through the water-saturated columns at a Darcy velocity which was varied between 0.37 and 2.2 m/d. Another column was run under unsaturated conditions. A reaction front evolved in all experiments characterized by a pH increase from pH 4 to pH 8. The chemical composition of the percolating water changed at the reaction front. Several heavy metals (Cd, Co, Cu, Ni) and Al were immobilized at this front. Other parameters such as Ca, S as SO4, V, and Mo were depleted within several days. The reaction front moved forward depending on the Darcy velocity in the column and the buffer capacity of the brick sand. Thermodynamic calculations (PHREEQC 2.0) indicated that mobilization of As was influenced by Ba(AsO4)2. The solubility of Ba and Mn was controlled by barite and manganite, respectively. Reactive transport modeling was applied to describe the dissolution of the bricks with regard to their main components Ca, SO4, Al, and Si
Experimental data from column and batch samples
No full textThe presented thesis was written in the frame of a project called 'seepage water prognosis'. It was funded by the Federal Ministry for Education and Science (BMBF). 41 German institutions among them research institutes of universities, public authorities and engineering companies were financed for three years respectively. The aim was to work out the scientific basis that is needed to carry out a seepage water prognosis (Oberacker und Eberle, 2002). According to the Federal German Soil Protection Act (Federal Bulletin, 1998) a seepage water prognosis is required in order to avoid future soil impacts from the application of recycling products. The participants focused on the development of either methods to determine the source strength of the materials investigated, which is defined as the total mass flow caused by natural leaching or on models to predict the contaminants transport through the underlying soil. Annual meetings of all participants as well as separate meetings of the two subprojects were held.
The department of Geosciences in Bremen participated with two subprojects. The aim of the subproject that resulted in this thesis was the development of easily applicable, valid, and generally accepted laboratory methods for the determination of the source strength. In the scope of the second subproject my colleague Veith Becker developed a computer model for the transport prognosis with the source strength as the main input parameter
A 1.4.2.3. Data of the saturated column experiments with the sandy fraction of harbour sediments - outlet - trace elements
No full textA 1.3.3. Data of the batch experiments with the sandy fraction of harbour sediments - trace elements
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A 3.2.3. Data of the batch experiments with municipal waste incineration ash - trace elements
No full textA 2.3.2.3. Data of the saturated column experiment with demolition waste - outlet - trace elements
No full textA 3.3.3.3. Data of the saturated column experiment with municipal waste incineration ash - flow-path sampling after 276 days - trace elements
No full textA 1.4.3.1. Data of the saturated column experiments with the sandy fraction of harbour sediments - flow-path sampling after 90 days - liquid/solid ratio, electric conductivity, pH and Eh value, inorganic carbon, dissolved organic carbon and anions
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