title: Identification of surfactant degradation products as toxic organic compounds present in sewage sludge.
abstract: A cost-effective strategy combining chemical analysis and bioassays for the identification of polar toxic compounds in sewage sludge is reported. ToxAlert 100 bioluminescence inhibition assay was used in combination with chemical analysis involving extraction, clean-up, chromatographic separation and mass spectrometry detection. This methodology was applied to real samples of sludge from three wastewater treatment plants (WWTP) located in Catalonia (Spain) during a 3 month period. In the first step, sewage sludge was lyophilized, treated by sonication with a mixture of methanol and chloroform and finally cleaned up using a sequential solid phase extraction (SSPE) with an octadecylsilica cartridge (C18) in series with a polymeric Lichrolut EN cartridge (Lic EN). In the second step, the toxicity of each fraction of the sludge sample was investigated using the ToxAlert 100. The unequivocal identification and quantification of polar organic cytotoxic substances present in the fractionated extracts were determined by liquid chromatography-mass spectrometry (LC-MS). Major toxic compounds identified were: non-ionic polyethoxylated surfactants (nonylphenol polyethoxylates, alcohol polyethoxylates), their intermediates (polyethylene glycol polyethoxylated, nonylphenol carboxylates and polyethoxylated alcohol carboxylates), linear alkylbenzenesulfonates and heavy metals. The toxic response (in terms of bioluminescence inhibition using ToxAlert 100), defined by the 50% effective concentration (EC50), and the toxicity units (TU) for every standard non-ionic surfactant were calculated. The results provided the identification of polar cytotoxic compounds as well as the evaluation of their contribution to the total toxicity observed in sewage sludge.
authors.affiliation: Department of Environmental Chemistry IIQAB-CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain.
authors.forename: M
authors.initials: M
authors.lastname: la Farré
authors.forename: M J
authors.initials: MJ
authors.lastname: García
authors.forename: M
authors.initials: M
authors.lastname: Castillo
authors.forename: J
authors.initials: J
authors.lastname: Riu
authors.forename: D
authors.initials: D
authors.lastname: Barceló
mesh_terms: D001673:Biodegradation, Environmental; D001681:Biological Assay; D002623:Chemistry Techniques, Analytical / Q000379:methods; D002851:Chromatography, High Pressure Liquid; D004784:Environmental Monitoring / Q000379:methods; D008163:Luminescent Measurements; D009930:Organic Chemicals / Q000032:analysis; D010776:Photobacterium / Q000187:drug effects / Q000502:physiology; D012722:Sewage / Q000737:chemistry*; D013057:Spectrum Analysis; D013501:Surface-Active Agents / Q000009:adverse effects / Q000032:analysis* / Q000378:metabolism; D014733:Vibrio / Q000187:drug effects / Q000502:physiology; D015262:Xenobiotics / Q000009:adverse effects / Q000032:analysis* / Q000378:metabolism
chemical_list: D009930:Organic Chemicals; D012722:Sewage; D013501:Surface-Active Agents; D015262:Xenobiotics