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PW08 Ecotoxicity and Environmental Chemistry of Antibiotics
(PW138) Degradation of 14C-labelled antibiotics in a modified laboratory sewage treatment plant.
Junker, T.1, Roembke, J.1, Kuemmerer, K.2, Alexy, R.2, 1 ECT Oekotoxikologie GmbH, Floersheim, Germany2 Institute of Environmental Medicine and Hospital Epidemiology, University Hospital, Freiburg, Germany
ABSTRACT- Antibiotics rank among the most important pharmaceuticals, based on the amounts consumed. Depending on the sub-stance and the type of application, different portions of the active substances or metabolites reach the environment. The microorganisms found in biological wastewater treatment play an important role in this process. First of all, low-degradable antibiotics or their metabolites could reach the surface water via the effluents of sewage treatment plants. Furthermore, the cleaning process itself could be affected by the presence of antibiotics. Therefore, the German Federal Environmental Agency (UBA) has originated the project Degradation of antibiotics and their release into the aquatic environment: Identification of potential risks (Grant No. 298 63 722). One part of the project deals with the examination of the biodegradability of several antibiotics in a laboratory sewage treatment plant. Following OECD Guideline No. 303 A, the biodegradation of selected antibiotics (benzylpenicillin, ceftriaxone and trimethoprim) was tested at low concentra-tions (close to reality) using radiolabelled (14C) test substances. For this purpose, the laboratory sewage treatment plant described in the guideline had to be modified to create an almost closed system. The degradation of the organic sub-stances was detected by means of mineralisation to 14CO2. The radiolabelled test substance was added continuously at a constant rate and the radioactivity was measured in all compartments of the activated sludge unit. Developed 14CO2 and other volatile radioactive compounds were trapped by drawing the gas out of the vessels and entraining it through wash bottles. Thus, the distribution of the test substance in the activated sludge could be accurately measured in the various compartments. The results indicate that these antibiotics pass the sewage treatment plant for the most part and therefore could reach the surface water. Consequently, the examinations make an important contribution to the risk as-sessment for antibiotics in the aquatic environment.
Key words: aquatic systems, environmental risk assessment, pharmaceuticals, standard test
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