Elimination of pharmaceuticals in sewage treatment plants in Finland.

The occurrence of eight pharmaceuticals (beta-blockers: acebutolol, atenolol, metoprolol and sotalol; antiepileptic: carbamazepine; fluoroquinolone antibiotics: ciprofloxacin, norfloxacin, ofloxacin) were assessed in the raw and treated sewage of 12 sewage treatment plants (STPs) in Finland. The average concentrations in the raw and treated sewage ranged from 100 to 1060 ng L(-1) and from <24 to 755 ng L(-1), respectively. The average daily loads ranged from 36 to 405 mg/1000 inh and from 2 to 302 mg/1000 inh, respectively. In the treatment plants, fluoroquinolones were eliminated by >80%. Carbamazepine was not eliminated during the treatment and in fact even higher concentrations were frequently found in the treated than in the raw sewages. The increase in concentration was shown to be most likely due to enzymatic cleavage of the glucuronic conjugate of carbamazepine and release of the parent compound in the treatment plant. The beta-blockers were eliminated in average by less than 65% and the elimination varied greatly between the treatment plants. Especially the dilution of raw sewage by rainwater and a consequent decrease in the hydraulic retention time of a treatment plant was found to deteriorate the elimination of the beta-blockers. The work shows that especially carbamazepine and the beta-blockers may reach the recipient waters and there is a need to enhance their elimination in the sewage treatment plants. In this attempt, a denitrifying biofilter as a tertiary treatment could be of minor importance since in this study it did not result in further elimination of the target compounds.