Complementary use of GCxGC-TOF-MS and statistics for differentiation of variety in biosolid samples

Formation of biosolid cakes, which are one of the main wastes generated in wastewater treatment plants, is connected with emission of many hazardous chemical compounds, including odoriferous ones. To optimize particular processes of biosolid cake processing, it is necessary to assess chemical composition of the gas mixtures containing the compounds released from the cakes. The paper proposes application of two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-TOF-MS) to identification of the compounds released from four main types of biosolid cakes and to quantitative determination of the markers characteristic for particular types of cake. Based on the analysis of variance, the following compounds, which could be potential markers of the investigated biosolid cakes, were selected: 1-propanol, 2-hexanone, toluene, o-xylene, p-xylene, and organosulfur compounds (methanethiol, ethanethiol, dimethyl sulfide, dimethyl disulfide, and diethyl disulfide). Theoretical odour concentrations of four investigated types of biosolid cakes were determined, based on measured concentrations and olfactory thresholds of the aforementioned compounds. The highest concentration was revealed for a primary cake (634 ou/m(3)), whereas the lowest concentration was found for an excess cake (136 ou/m(3)) (ou/m(3)-odour unit per m(3); one odour unit is equivalent to collective odour threshold of odorants mixture present in 1 m(3)). The proposed methodology allows preliminary evaluation of the odour nuisance markers connected with formation of the biosolid cakes, without a need for quantitative analysis of all determined compounds. [GRAPHICS] .