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Abstract The aim of the study was to investigate the biodegradability of guanyl urea (GU) and the behavior of other transformation products (TPs) of Metformin (MF). Most biodegradation studies of MF with activated sludge of waste water treatment plants (WWTPs) showed GU as the only bacterial dead-end metabolite without further degradation. In this study, batch experiments with activated sludge revealed biodegradability of GU. GU degradation was much faster under anaerobic than under aerobic conditions. Degradation kinetics for MF was much slower under anaerobic conditions. Adsorptive removal of up to 20% was an additional elimination process of MF and GU. The batch experiments were conducted with sludge of 2 WWTPs, WWTP 1 showed decreasing concentrations of GU from influent to effluent and the other increasing concentrations. This indicates a different adaption of the sludge to GU and may explain the better GU degradation capability of the sludge from WWTP 1. Furthermore, the biodegradation potential of MF was confirmed and in addition, occurrence of the TPs methylbiguanide (MBG), 2-amino-4-methylamino-1,3,5-triazine (2,4-AMT) and the secondary TP 2,4-diamino-1,3,5-triazine (2,4-DAT) was observed in batch experiments with activated sludge of WWTP 1. After fast formation, degradation in turn was slower, especially for 2,4-AMT. In general, TPs played a minor role in MF and GU degradation. Graphical abstract Image 1 Highlights • Guanyl urea revealed as biodegradable under anaerobic and aerobic conditions. • Degradation capability of guanyl urea in lab experiments is also reflected in full-scale plants. • Other transformation products of metformin were formed below 2%. [ABSTRACT FROM AUTHOR]

The aim of this work was to investigate the occurrence and fate of the antidiabetic metformin (MF) and its transformation products (TPs) in wastewater and surface water samples. New TPs of MF were approached by electrochemical degradation with a boron-doped-diamond electrode (at 1.5 V for 10 min). 2,4-Diamino-1,3,5-triazine (2,4-DAT), methylbiguanide (MBG), 2-amino-4-methylamino-1,3,5-triazine (2,4-AMT) and 4-amino-2-imino-1-methyl-1,2-dihydro-1,3,5-triazine (4,2,1-AIMT) were identified by hydrophilic interaction chromatography (HILIC) with quadrupole time-of-flight mass spectrometry (QTOF-MS) and accurate mass fragmentation. However, the well-known transformation product guanyl urea (GU) could not be formed electrochemically. In samples from wastewater treatment plants (WWTP), 2,4-AMT and 2,4-DAT showed an increasing trend from influents to effluents, which implies formation of the TPs during WWT. MBG is also formed by hydrolysis of MF and therefore didn't show this trend in WWTPs. Compared to GU, the concentrations of other TPs are generally three orders of magnitude lower. MBG and 2,4-DAT were also detected in surface water which was impacted by waste water, while 4,2,1-AIMT could not be detected in any sample. The concentrations of MF were in an expected range for influent (14 to 95 μg/l), effluent (0.7 to 6.5 μg/l), surface water (up to 234 ng/l) and tap water (34 ng/l). GU concentrations, however, were in one of the two investigated WWTP much higher in the influent (between 158 μg/l and 2100 μg/l) than in the effluent (between 26 and 810 μg/l). This is a rather unexpected result which has not been reported yet. Obviously, GU has been already formed in parts of the sewer system from MF or from other biguanide compounds like antidiabetics or disinfection chemicals. Furthermore, lower concentrations of GU in the effluents than in the influents indicate degradation processes of guanyl urea in the waste water treatment. [ABSTRACT FROM AUTHOR]

Denatonium, one of the bitterest substances known to man, was recently identified as wastewater borne micropollutant in surface waters. Therefore, photodegradation experiments and electrochemical degradation were performed to identify abiotic and putative biotic transformation products (TPs). Indirect rather than direct photodegradation proved to be important for denatonium removal by solar irradiation and produced seven TPs. Amide hydrolysis, hydroxylation, N-dealkylation, and N-dearylation were revealed as the main mechanisms. Anodic oxidation of denatonium was related to the formation of overall ten products and despite considerable different yields, all TPs from indirect photodegradation were mimicked electrochemically. Among them, lidocaine was the only TP detected after conventional wastewater treatment and in surface waters. The occurrence of lidocaine was however associated with its application as local anesthetic rather than to a degradation of denatonium. The absence of additional products suggests that denatonium degradation is negligible under environmental conditions, supporting the previously described persistent nature of this compound. Advanced water treatment techniques however have the potential to degrade denatonium. About 74% of the initial denatonium load was removed from wastewater during pilot-scale ozonation. The degradation of denatonium was accompanied here with the formation of at least two polar products, which are passing unchanged through a sand filter after ozonation. Both substances have completely unknown (toxicological) properties and this study seems to be the first report about their structures in general, as none of them was found in any of the large compound libraries (e.g. PubChem). Unlabelled Image • Indirect photodegradation and electrochemical oxidation resulted in overall ten TPs. • Five products were identified with a confidence level of 2 or better. • High persistence of denatonium in conventional wastewater treatment and in surface waters observed. • Denatonium removal by ozonation is associated with the formation of polar TPs. [ABSTRACT FROM AUTHOR]

Abstract β‑Lactam antibiotics are among the most widely used antibiotics in human medicine and their effects on the aquatic environment - concerning bacterial resistance - are controversially discussed. This study focused on the photolysis of the four β‑lactam antibiotics - amoxicillin, ampicillin, penicillin V and piperacillin - under simulated environmental conditions. It was observed that all investigated β‑lactam antibiotics are photolytically degradable by simulated sunlight (1 kW/m2) with half-lives between 3.2 and 7.0 h. Structure elucidation of transformation products performed with liquid chromatography coupled to high resolution mass spectrometry showed that the hydrolysis of the β‑lactam ring is the primary transformation reaction, followed by the elimination of carboxylic and dimethyl thiazolidine carboxylic acid. Growth inhibition tests on Bacillus subtilis showed the loss of bactericide activity of irradiated solutions of amoxicillin, ampicillin and piperacillin, suggesting the transformation of the β‑lactam ring is responsible for the antibiotic effect. In contrast, the solutions of penicillin V did not show any decline of the antibacterial activity after photolytic degradation, probably due to the formation of still active epimers. Graphical abstract Unlabelled Image Highlights • Simulated sunlight was shown to be able to degrade β‑lactam antibiotics. • New transformation products of β‑lactam antibiotics were elucidated. • Photolysis of amoxicillin, ampicillin and piperacillin reduces the growth inhibition effect. • Photolytically transformed penicillin V keeps the ability to inhibit bacterial growth. [ABSTRACT FROM AUTHOR]

The pharmaceutical torasemide is an important loop diuretic and was 2017 one of the ten most prescribed drugs in Germany. Despite its detection in different compartments of the urban water cycle including drinking water, no studies were so far performed to elucidate its fate in the environment and the occurrence of transformation products (TPs). Therefore, we investigated the phototransformation, microbial degradation, transformation with human liver microsomes and anodic oxidation of torasemide to obtain good coverage of environmentally relevant degradation products. Overall sixteen products were identified, covering the following reaction mechanisms: aromatic and aliphatic hydroxylation, including further oxidation to carboxylic acids and quinone imines, amide cleavage, N-dealkylation, N-dearylation, and sulfonamide hydrolysis to sulfonic acids. Especially the formation of quinone imines could be of concern as they are highly reactive electrophiles. Torasemide itself was observed in all investigated wastewater treatment plant (WWTP) samples and wastewater-impacted surface waters. The maximum detected concentration was about 350 ng L−1. Only three of the sixteen transformation products were generally observed in at least one of the samples and the most frequently detected TPs were the human metabolites hydroxytorasemide (TP 364a) and carboxytorasemide (TP 378a). The complete removal of TP 364a during wastewater treatment was in agreement with the results of microbial degradation experiments. TP 364a was most likely transformed into TP 378a, which was microbially less degraded in lab experiments. Based on estimated concentrations, TP 378a could reach about 1 μg L−1 in the investigated wastewater matrices. Image 1 • Overall sixteen abiotic and biotic products identified for torasemide. • Formation of reactive products proven with trapping experiments using reduced glutathione. • Torasemide and carboxytorasemide detected in all WWTPs and wastewater-impacted surface waters. [ABSTRACT FROM AUTHOR]