Occurrence and risk assessment of nonylphenol and nonylphenol ethoxylates in sewage sludge from different conventional treatment processes M.M. González, J. Martín, J.L. Santos, I. Aparicio, E. Alonso ⁎ Department of Analytical Chemistry, Chemical Engineering School, University of Seville, C/ Virgen de África 7, E-41011 Seville, Spain abstract article info Article history: Received 27 May 2009 Received in revised form 30 September 2009 Accepted 10 October 2009 Available online 5 November 2009 Keywords: Nonylphenol Nonylphenol ethoxylate Sewage sludge Compost Risk assessment In the present work, the concentrations of the organic pollutants nonylphenol (NP) and nonylphenol mono- and diethoxylates (NP1EO and NP2EO, respectively) in primary, secondary, mixed, aerobically-digested, anaerobically-digested, dehydrated, compost and lagoon sludge samples from different sludge treatments have been evaluated. Toxicological risk assessment of these compounds in sludge and sludge-amended soil has also been reported. NP, NP1EO and NP2EO were monitored in sludge samples obtained from treatment plants located in Andalusia (south of Spain) based on anaerobic treatments (11 anaerobic-digestion waste- water treatment plants and 3 anaerobic wastewater stabilization ponds) or on aerobic treatments (3 aerobic- digestion wastewater treatment plants, 1 dehydration treatment plant and 2 composting plants). The sum of NP, NP1EO and NP2EO (NPE) concentrations has been evaluated in relation to the limit value of 50 mg/kg set by the European Union Sludge Directive draft published in April 2000 (Working Document on Sludge). In most of the samples, NP was present at higher concentration levels (mean value 88.0 mg/kg dm) than NP1EO (mean value 33.8 mg/kg dm) and NP2EO (mean value 14.0 mg/kg dm). The most contaminated samples were compost, anaerobically-digested sludge, lagoon sludge and aerobically-digested sludge samples, which contained NPE concentrations in the ranges 44–962 mg/kg dm, 8–669 mg/kg dm, 27–319 mg/kg dm and 61–282 mg/kg dm, respectively. Risk quotients, expressed as the ratios between environmental concentra- tions and the predicted no-effect concentrations, were higher than 1 for NP, NP1EO and NP2EO in the 99%, 92% and 36% of the studied samples, respectively; and higher than 1 in the 86%, 6% and 2%, respectively, after sludge application to soil, leading to a significant ecotoxicological risk mainly due to the presence of NP. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Sewage sludge is a product of wastewater treatment processes which tends to concentrate potential contaminants such as pesticides, metals, pathogens, industrial solvents, dyes, plasticizers and other organic chemical residues (Gibson et al., 2005). Monoalkylphenol polyethoxylates, mainly parasubstituted, constitute an important group of non-ionic surfactants widely used in many commercial and house- hold applications, including non-agricultural pesticides, cosmetics, cleaning products and office products such as correction fluids and inks (Stasinakis et al., 2008). Because of the frequent use of nonylphenol polyethoxylates as cleaning products, they are continuously being discharged into the environment through effluents from wastewater treatment plants (WWTPs). During wastewater treatment, nonylphenol polyethoxylates are degraded to shorter-chain metabolic intermediates including non- ylphenol (NP), nonylphenol monoethoxylate (NP1EO) and nonylphe- nol diethoxylate (NP2EO) (Ahel et al., 1994). These compounds are toxic for aquatic and terrestrial organisms, probably as a result of their interactions with proteins (Scott-Fordsmand and Krogh, 2004). Besides their direct toxicity, these compounds have been classified as endocrine disrupting chemicals by several organizations and NP has even been listed as a priority substance in the European Union (EU) Water Framework Directive (EC, 2001). Among the high amount of waste substances discharged through the sewer systems, NP, NP1EO and NP2EO are some of the organic compounds with a significant tendency to be accumulated into sewage sludge (Zhang et al., 2009) and, as a result, they are commonly detected not only in wastewater (Gatidou et al., 2007) but also in sludge (Aparicio et al., 2009, 2007; Fountoulakis et al., 2005; Lee et al., 1997) and in sludge- amended soil samples (Gibson et al., 2005; Núñez et al., 2007; Petrovic and Barceló, 2000). Sewage sludge is usually aerobically or anaerobically treated before disposal in order to reduce its organic matter content. The organic matter is often more effectively removed under anaerobic conditions, but a higher persistence of these pollutants has been reported to occur under such conditions (Santos et al., 2007; Núñez et al., 2007). Nevertheless, further composting processes applied to anaerobically-treated sludge appear to be useful for the removal of these pollutants (Núñez et al., 2007; Gibson et al., 2007). The type Science of the Total Environment 408 (2010) 563–570 ⁎ Corresponding author. Tel.: +34 9 5455 2858; fax: +34 9 5428 2777. E-mail address: ealonso@us.es (E. Alonso). 0048-9697/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2009.10.027 Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv