Potential emissions from two mechanically-biologically pretreated (MBT) wastes.

The interaction of parameters determining the potential emissions of two different mechanically-biologically pretreated municipal solid wastes (MBT wastes) is elucidated in this work. The origins of the wastes are Germany and Sweden. By means of lab-scale experiments, increased stabilisation through composting is preferably determined by a decrease in respiration activity. Concurrently, the stabilisation is verified for the leachates by a decrease in COD, DOC, and BOD(5). Total organic carbon content reflects stabilisation less accurately. FT-IR and thermal analytical methods add valuable information about the state of degradation, especially when several distinct thermal parameters are taken into account. Mobility of Cr, Ni, Pb, and Zn produced by a batch leaching test with deionized water is reduced by the pretreatment of both materials. Mobility of copper unambiguously increased. A principle component analysis (PCA) of membrane fractionated leachates indicates an affinity of Cu to mobile humic acids or dissolved organic carbon. High Cr, Zn, and Ni contents in the solid co-occur with high contents of solid humic acids. To a lesser extent, this is also true for solid Cd, Cu, and Pb contents. Due to differences in required landfilling conditions, actual emissions and after-care phase length will depend on whether each waste is landfilled in Germany or Sweden.

Fate of 14C-labeled anthracene and hexadecane in compost-manured soil.

Experiments were carried out to evaluate the impact of the addition of ripe compost on the degradation of two 14C-labeled hydrocarbon model compounds (anthracene and hexadecane) in soil. The addition of mature compost (20% dry wt./dry wt) stimulated significantly the disappearance of the extractable fraction of both compounds. With compost, 23% of the labeled anthracene was transformed into 14CO2 and 42% was fixed to the soil matrix irreversibly. In the unsupplemented control reactor, more than 88% of the original anthracene could be recovered by either of two organic extraction procedures. THe formation of non-extractable bound residues was significantly less with 14C-hexadecane since only 21% of the labeled carbon had become non-extractable after 103 days. The results presented show that compost could stimulate the depletion of hydrocarbons by either mineralization or the formation of unextractable bound residues (humification). The latter process might be a significant route of depletion in soil especially, for those hydrocarbons that are mineralized only slowly. The meaning of this finding for the assessment of soil bioremediation is discussed.