Designed to be active and interact with receptors in humans and animals or to be toxic for many infectious organisms, pharmaceuticals (PhACs) can easily have unintended effects on animals and microorganisms in the environment. Therefore, this group of emerging contaminants has received noticeable attention over the past decade. Traces of PhACs have been detected in surface water and aquatic sediment, as well as in soil irrigated with reclaimed water or treated with biosolids from urban wastewater treatment plants (WWTPs). WWTPs have been mostly studied as they were identified as the main point of collection and subsequent release of PhACs into the environment. Nevertheless, the information is mostly related to the water train of WWTP, and less is known about the occurrence and fate of PhACs during sludge treatment processes. Chemical characterization of sludge is not at all simple, and this might be the main reason for the lack of information. Besides, the quality of sludge depends on the composition of wastewater and the type of treatments applied to both water and sludge. Among sludge treatment processes, anaerobic digestion (AD) is the most commonly applied stabilization method. AD is the best option for the stabilization of waste activated sludge (WAS) from an economic and environmental standpoint. It is a very good solution for the reduction of the organic fraction of municipal solid waste (OFSMW) in separate or combined AD. Although AD is the most studied sludge stabilization process, the data on the occurrence and fate of PhACs in AD are very scarce. In this study, we aimed at assessing the occurrence and behavior of 42 selected PhACs during wastewater treatment, with an accent on anaerobic co-digestion stage. The PhACs of interest belong to different therapeutic groups, i.e. analgesics and anti-inflammatories, psychiatric and antiepileptic drug, antibiotics etc. The studied municipal integrated WWTP treats low loaded domestic wastewater in a nitrogen and phosphorous biological removal process. The sludge treatment train provides the anaerobic co-digestion of WAS and the OFMSW, with the following separate short-cut nitrogen removal from the anaerobic supernatant. Samples of influent (i.e. aqueous phase and suspended solids), and effluent; thickened and digested sludge were collected to determine the mass flows of the target PhACs throughout the WWTP. Partitioning of PhACs between aqueous and solid phases of AD was studied to obtain more information on their fate during the treatment, and to understand better the contribution of biodegradation and sorption on the overall removal. The preparation and analysis of the samples were performed according to the previously developed multiresidual methodologies for analysis of PhACs in wastewater and sludge samples. Acknowledgements. This work has been supported by the Spanish Ministry of Science and Innovation through the project Consolider-Ingenio 2010 SCARCE.
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