PAHs in sewage sludge

Sewage sludge has been found to be a sink for PAH originating from both domestic households and industrial sources. Hence this matrix may reflect the actual environmental situation and can be used as a target matrix in a continuous monitoring of the PAH 

Centrifuged sewage sludge was obtained from a municipal waste water treatment plant of a large city (100 kg with dry matter content of 21% as mass fraction). The material was heat-sterilised (medium-pressure) at 134°C for three intervals of (1) 75 minutes, (2) 60 minutes and (3) 60 minutes by autoclavation. In between the material was allowed to cool for 60 minutes at ambient temperature. The material was dried in a climate chamber at 20°C under air while being crushed mechanically. This was performed in stainless steel-containers in which the material had been spread and frequently raked for 3 months. Finally the material was dried in a ventilated oven for 48 h at 40°C. 

Sub-samples of 1 g were taken for the analysis. The PAHs were extracted under reflux with toluene/acetone (1 1 v/v, 150 mL) for 30 minutes. The efficiency of the extraction procedure was tested by adding an internal standard (indeno[l,2,3-c t/]fluoranthene) and was found to be 95 99%. An additional extraction with tetrahydrofurane did not enhance the PAH yield. The extract was evaporated to about 2 mL. A cydohexane/dimethylformamide (DMF)/water (100 mL cyclohexane, 90 mL DMF and 10 mL water) partition was performed. The cyclohexane phase was discarded and the DMF/water phase diluted with 80 mL water. This phase was re-extracted with cyclohexane. The cyclohexane phase was evaporated to a volume of 2 mL and cleaned-up over a silica column (5 g, 9.1% water). The PAHs were eluted with 80 mL cyclohexane, which was evaporated afterwards to a volume of 0.1-0.5 mL. The obtained concentrate was placed on a Sephadex LH 20 column (10 g) and eluted with propanol-2. The fraction of 0-46 mL was discarded. The fraction from 46-170 mL was evaporated to a small volume and analysed by high resolution gas chromatography (on column injection) using a fused silica capillary column of which the conditions are described elsewhere [26]. 

The stability of the PAHs in the sewage sludge was tested over a period of 12 months 

The final determination of the PAHs was performed by capillary gas chromatography using flame ionisation or mass spectrometric detection, or by high-performance liquid chromatography using UV- and fluorescence detection. Each participant had validated its method by performing experiments on recovery, extraction efficiency, procedure blanks and detector linearity. 

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Wild, S.R., Berrow, M.L., Jones, K.C. (1991) The persistence of polynuclear aromatic hydrocarbons (PAHs) in sewage sludge amended agricultural soils. Environ. Pollut. 72(2), 141-157. 

Wild et al. [21] reported a long-term study of the persistence of PAHs applied in sewage sludges to agricultural soils. The compounds with greater... 

The common extraction method for PCBs in sewage sludges, choosen for this exercice, gives a very good comparabihty between results and it is easy to perform. In addition this method is also able to extract PAHs... 

Average PAH-contents in sewage sludges in different regions of the project area Concentrations in /tg/kg solid matter (ppb)... 

Berset, J.D. Holzer, R. Quantitative determination of polycyclic aromatic hydrocarbons, polychlorinated biphenyls and organochlorine pesticides in sewage sludges using supercritical fluid extraction and mass spectrometric detection. J. Chromatogr., A 1999, 852, 545-558. Gongalves, C. De-Rezende Pinto, M. Alpendurada, MJ. Benefits of a binary modifier with balanced polarity for an efficient supercritical fluid extraction of PAHs from solid samples followed by HPLC. J. Liq. Chromatogr. Relat. Technol. 2001, 24 (19), 2943 -2959. 

Litz [2] PCDDs, PCDFs, AOX, PCBs, PAHs, LAS, nonylphenol, tributyltin oxides, DEHP Risk assessment were conducted in this study, concentrations were not addressed Sewage sludge... 

Moeller J, Reech U (2003) Degradation of DEHP, PAHs and LAS in source separated MSW and sewage sludge during composting. Compos Sci Utiliz 11 370-378... 

PAH-contents in 57 sewage sludges from 38 treatment plants in the total project area. Concentrations in ... 

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