Purpose: The Llobregat River, which is characterized by important fluctuations of the flow rates, receives treated waters from WWTPs. During the years 2007 and 2008, the Llobregat River basin suffered from a severe drought which affected the supply of drinking water facilities (DWF) that rely on the exploitation of the river water. The Catalan Water Agency implemented a water reuse experiment with the objective of maintaining the river flow rate at sufficiently high level so as to ensure the supply of raw water to Barcelona's major DWF.
Method: A total of 103 emerging contaminants belonging to the groups of pharmaceuticals (74), illicit drugs (17) and oestrogens (12) were determined using LC-MS/MS methods in river water samples during the water reuse campaign. The effect of the reclaimed water discharge on the river water quality, in terms of contamination loads and environmental risk (based on the concentration addition mode), is discussed.
Results: Fifty-eight pharmaceuticals out of 74 monitored were detected at least in one sample. In river water upstream (site R0) majority of compounds were detected at low nanograms per litre levels, while downstream of discharge of tertiary effluent only few compounds were detected at levels higher than 100 ng L(-1) (i.e. acetaminophen, diclofenac, erythromycin, sulfamethazine), but never exceeding 500 ng L(-1). The total concentration of illicit drugs was found to be very low at both sampling sites (<50 ng L(-1)). No relevant ecotoxicity risks were identified, except for pharmaceuticals vs. algae.
Conclusions: In general, the discharge of reclaimed water in the river influenced perceptibly in terms of concentrations, mass loads and environmental risk, especially for pharmaceuticals and in less extent for illicit drugs. Nevertheless, it was not very significant in any case.