Organic markers in the lipidic fraction of sewage sludges

The lipidic organic fraction of 48 sewage sludges that originated from food-processing, paper-mill and domestic (urban, small urban, and rural) wastewater-treatment plants of the Lorraine region (Northeast of France) was characterised by gas chromatography coupled with mass spectrometer (GC-MS). This study enables us to define an average organic composition typical of each group of sewage sludges. Linear alkyl benzenes (LABs) are only present in domestic sludges, sterols in food-processing and domestic sludges. Paper-mill sludges are characterised by the specific distribution of n-alkanes. Besides, all the domestic sludges, whatever the size of the wastewater catchment, are characterised by the same distribution of polar compounds. Differences can be evidenced in the distribution of the aliphatic compounds of some domestic sewage sludges and are attributed to the important contribution of petroleum products in their sewer system. Moreover, this study highlights the correlation between abundance of polycyclic aromatic hydrocarbons (PAHs) in the aromatic fraction of some sewage sludges and a distribution of n-alkanes characteristic of heavy petroleum products into the corresponding aliphatic fraction. This might be a clue for the determination of punctual sources of PAHs.