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Abstract:
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Pharmaceuticals are consumed in high quantities in the modern society and especially in industrialized countries. Residues of the consumed pharmaceuticals are carried to sewage treatment plants and can end up in the aquatic environment via discharges of the treated effluents to surface waters. In the environment, the compounds and there mixtures may cause adverse effects on aquatic organisms or they can be carried to drinking water treatment plants.
In this thesis, two analytical methods were developed to allow the determination of thirteen pharmaceuticals at low ng Lˉ¹ concentrations in environmental samples. These pharmaceuticals were: ciprofloxacin, norfloxacin and ofloxacin (antibiotics), carbamazepine (antiepileptic), diclofenac, ibuprofen, ketoprofen and naproxen (anti-inflammatories), and bezafibrate (lipid modifying agent). The methods included the following steps: isolation and concentration with solid phase extraction, separation by liquid chromatography and detection with triple quadrupole mass spectrometry. Quantification limits were 0.2 22 ng Lˉ¹ in drinking water and 3.5 163 ng Lˉ¹ in raw sewage. Sulfamethoxazole, an antibiotic, was also selected for the study but could only be analyzed at concentrations above 5 µg Lˉ¹. Hence, the compound could not be analyzed in the environmental samples. The methods were utilized to study the occurrence of the pharmaceuticals in raw and treated sewages, rivers and drinking waters in Finland. Additionally, the elimination of the pharmaceuticals was studied in different drinking water treatment processes.
The studied pharmaceuticals were detected in the sewage influents at concentrations ranging from <0.02 to 29 µg Lˉ¹. The compounds were not fully eliminated in the treatment processes and were measured at concentrations as high as 3.9 µg Lˉ¹ in the effluent samples. Low sewage temperature as well as the increase of the influent flow rate during heavy rain with a subsequent lowering of the hydraulic retention time hampered the elimination of the pharmaceuticals in the treatment plants.
Sewage effluents were found to be the main source of the studied pharmaceuticals in the sampled rivers. All compounds but norfloxacin were detected above their LOQ concentrations at least in one sample. The concentrations of the compounds were mainly <100 ng Lˉ¹. Residuals of pharmaceuticals can be harmful to aquatic organisms at the measured concentrations. Downstream of the treatment plants, lower concentrations of the pharmaceuticals were measured especially in the summer. It was suggested that this was due to more effective phototransformation and biodegradation of the pharmaceuticals in the rivers in the summer than in the winter.
Some of the studied pharmaceuticals were detected at concentrations of 5 8 ngLˉ¹ in the drinking water samples. Of the different drinking water treatment techniques, coagulation and sand filtration were inefficient in elimination of pharmaceuticals whereas granular activated carbon filtration and ozonation effectively eliminated the compounds from the raw water. Only ciprofloxacin was not fully eliminated in these unit operations. The effects on humans caused by chronic exposure to low concentrations of pharmaceuticals over a long period of time are unknown. Still, the risk for the consumers is most probably negligible. |