Pharmaceuticals as chemical markers of wastewater contamination in the vulnerable area of the Ebro Delta (Spain)

This study evaluated the occurrence and distribution of 81 pharmaceutically active compounds (PhACs) in the vulnerable area of the Ebro Delta region (Catalonia, Spain), to assess the environmental impact of wastewater treatment plants discharge to coastal environments. The occurrence of PhACs was followed along the wastewater-recipient water-sediment chain until they reach estuaries and the Mediterranean Sea. Water and sediment samples were collected in an integrated way at different sampling points covering three different seasons in reaches of the Ebro River located upstream and downstream from wastewater treatment plants (WWTPs), surrounding channels, estuaries, and the associated receiving seawater. 28 out of the 57 compounds detected in effluent wastewater were positively identified in estuary and seawaters, revealing that WWTP discharges are an important source of contamination in coastal environments and that PhACs are suitable markers of urban contamination in these areas. The substances with the highest frequency of detection belonged to the groups of analgesics/anti-inflammatories (acetaminophen, salicylic acid), antihypertensives (valsartan), psychiatric drugs (carbamazepine), and antibiotics (clarithromycin, trimethoprim). In general, a decrease in concentration was observed from inland sampling points towards the Mediterranean Sea, resulting from a dilution in the recipient marine water bodies. A reduced number of PhACs, at concentrations ranging from 0.1 to 12.5 ng g−1 dry weight (d.w.) was detected in sediment samples, indicating that sorption is a minor natural attenuation pathway for these compounds. Finally, a prioritization strategy, based on the compounds concentration and frequency of detection in seawater, removal efficiency in WWTP, bioaccumulation potential, toxicity to marine organisms and persistency, was used to highlight the PhACs of major ecological concern and that could be used as relevant indicators of wastewater contamination in coastal environments.