Occurrence and toxicological assessment of six non–steroidal anti–inflammatory drugs (NSAIDs) in a wastewater treatment plant in Słupsk (Poland)

Pharmaceuticals are unique class of water pollutants due to their ability to modify the physiological effects of living organisms at low doses. Intensive use in healthcare as well as insufficient removal in conventional wastewater treatment processes make pharmaceuticals ubiquitous in the aquatic environment. The study aimed to assess the load of selected non–steroidal anti–inflammatory drugs (NSAIDs) in the influent and effluent from the wastewater treatment plant (WWTP) in Słupsk. Samples were collected in the period between May and September 2021. Once taken samples were filtered and the analytes were extracted using solid phase extraction (SPE) and then analyzed using the ultra–high performance liquid chromatography. Ibuprofen (IBU), salicylic acid (SA), acetylsalicylic acid (ASA), naproxen (NPX), ketoprofen (KET), and diclofenac (DIC) were found in raw and treated wastewater. Detected concentration ranged from 1.656 μg L^–1 to 25.912 μg L^–1 in the influent, and from 0.676 µg L^–1 to 10.484 µg L^–1 in the effluent. Removal was incomplete and its efficiency ranged between 57.3 % and 81.4 %. The ecotoxicological assessment was performed using a set of certified test organisms including marine bacteria (Aliivibrio fscheri), freshwater crustaceans (Daphnia magna), and freshwater plants (Lemna minor). Toxic concentrations ranged from 4.50 to 18.82 mg L^–1 for marine bacteria after 30 min of exposure, from 27.11 to 74.77 mg L^–1 for crustaceans after 48 h of exposure, and from 10.70 to 29.67 mg L^–1 for aquatic plants after 7 days of exposure. Studied pharmaceuticals were mostly classified as toxic or harmful to test organisms.