New insights into the transformation of trimethoprim during biological wastewater treatment

Abstract

The antibiotic trimethoprim (TMP), a micropollutant found at μg/L levels in raw wastewater, was investigated with regard to its (bio)transformation during biological wastewater treatment. A pilot-scale, nitrifying/denitrifying Sequencing Batch Reactor (SBR) fed with municipal wastewater was monitored for TMP removal during a 16-month monitoring study. Laboratory-scaled bioreactors spiked with TMP were applied to identify the transformation products (TPs). In total, six TPs could be identified from TMP. However, the TP formation was influenced by the spike concentration. At an initial concentration of 500 μg/L TMP, only two TPs were found, whereas at 5 μg/L a completely different transformation pathway led to four further TPs. At low concentrations, TMP was demethylated forming 4-desmethyl-TMP, which was then quickly hydroxylated, oxidized and cleaved forming 2,4-diaminopyrimidine-5-carboxylic acid (DAPC) via two intermediate TPs. DAPC was detected in the SBR effluent in a 3-d composite sample with 61 ng/L, which accounts for 52% of the attenuated TMP. The primary degradation at low spiking levels was best modelled by a pseudo-first order kinetic. Considering the SBR, the model predicted a TMP removal of 88–94% for the reactor, consistent with a monitoring campaign exhibiting an average removal of >83%. Both the TP formation profiles and kinetic modelling indicated that only the results from the bioreactor tests at low spike concentrations were representative of the transformation in the SBR.

Effect of sulfadiazine and trimethoprim on activated sludge performance and microbial community dynamics in laboratory‐scale membrane bioreactors and sequencing batch reactors at 8°C

“…NOBs were representing less than 0.1% (mostly Candidatus Nitrotoga arctica ) of the community. These results can explain the differences in the negative effect of antibiotics on nitrifying community between this study and previously reported data because of different key nitrifying bacteria …”

Electrochemistry-High Resolution Mass Spectrometry to Study Oxidation Products of Trimethoprim

“…These results suggest that electrochemistry-high resolution mass spectrometry is an interesting technique for studying oxidative reactions of organic compounds of environmental interest, as was previously suggested by Hoffmann et al [12]. Nitrifying bacteria in activated sludge [34].…”

“…In a previous study of the transformation of TRI under aerobic conditions in nitrifying activated sludge, this same structure was assigned to a transformation product of TRI with the same exact mass, albeit a completely different MS/MS spectrum [34]. While differences in MS/MS could be the result of different mass analyzers (the present study used an QqTOF while in the study of Jewell et al a linear ion trap-orbitrap mass spectrometer was used) mass accuracy, spectral accuracy and comparison of MS/MS spectrum and in silico fragmentation suggests that the most likely structure of OP290 is isomer E or (2,4-diaminopyrimidin-5-yl)-(4-hydroxy-3,5-dimethoxyphenyl)methanone.…”

Understanding the biodegradation products and pathways of selected pharmaceuticals atenolol and acyclovir by an enriched nitrifying sludge through experiments and modeling

“…However, previous reports on the effect of initial concentrations on biotransformation pathways of pharmaceuticals were contradictory. The same degradation route was reported on trimethoprim by nitrifying activated sludge with two metabolites produced at initial concentrations of 20 mg L -1 and 20 µg L -1 whereas different biotransformation products were found under different spiked concentration (500 µg L -1 and 5 µg L -1 ) in another study (Eichhorn et al, 2005;Jewell et al, 2016). This discrepancy might be due to the properties of the activated sludge and the dominant microorganisms in different studies, which deserve further research.…”

“…Two metabolites were formed and the degradation route was independent on the initial concentration of trimethoprim (20 mg L -1 or 20 µg L -1 ). However, biodegradation of trimethoprim was also investigated by nitrifying activated sludge in another recent study (Jewell et al, 2016), resulting in different biotransformation products under different spiked concentration of trimethoprim (500 µg L -1 or 5 µg L -1 ). From the mass balance analysis, carboxy-acyclovir seems to be the only product by heterotrophs either in higher initial concentration or lower initial concentration of acyclovir.…”