Biotransformation of ibuprofen in biological sludge systems: Investigation of performance and mechanisms.

Ibuprofen (IBU), a common non-steroidal anti-inflammatory drug (NSAID), is widely used by humans for controlling fever and pain, and is frequently detected in the influent of wastewater treatment plants and different aquatic environments. In this study, the biotransformation of IBU in activated sludge (AS), anaerobic methanogenic sludge (AnMS) and sulfate-reducing bacteria (SRB)-enriched sludge systems was investigated at three different concentrations of 100, 500 and 1000 μg/L via a series of batch and continuous studies. IBU at concentration of 100 μg/L was effectively biodegraded by AS whereas AnMS and SRB-enriched sludge were less effective in IBU biodegradation at all concentrations tested. However, at higher IBU concentrations of 500 and 1000 μg/L, AS showed poor IBU biodegradation and chemical oxygen demand (COD) removal due to inhibition of aerobic heterotrophic bacteria (i.e., Candidatus Competibacter) by IBU and/or IBU biotransformation products. The microbial analyses showed that IBU addition shifted the microbial community structure in AS, AnMS and SRB-enriched sludge systems, however, the removals of COD, nitrogen and sulfur in both anaerobic sludge systems were not affected significantly (p > 0.05). The findings of this study provided a new insight into biotransformation of IBU in three important biological sludge systems.

Jia Y ，Yin L ，Khanal SK ，Zhang H ，Oberoi AS ，Lu H ... -  《-》

Influence of ibuprofen and its biotransformation products on different biological sludge systems and ecosystem.

Ibuprofen (IBU) is one of the frequently detected non-steroidal anti-inflammatory drugs (NSAIDs) in wastewater treatment plants (WWTPs) and aquatic environment. However, little is known about the effect of IBU and its biotransformation products (TPs) on different biological sludge systems and aquatic environment. The effects and toxicity of IBU and TPs on three biological sludge systems (i.e., activated sludge (AS), sulfate-reducing bacteria (SRB)-enriched sludge and anaerobic methanogenic (AnM) sludge systems) and aquatic environment were comprehensively evaluated through a long-term operation of three bioreactors and a series of batch experiments. Both of the SRB-enriched sludge and AnM sludge systems were not affected under a long-term exposure to IBU, based on removing organic carbon and sulfur and producing methane. This could be attributed to the high tolerance of functional microbes in the SRB-enriched sludge (e.g., genus Desulfobacter) and AnM sludge systems (e.g., genus Candidatus Methanomethylicus) for IBU. In contrast, IBU had some apparently inhibitory effects on the AS system, such as reduced organic removal efficiency and poor sludge settling. The analysis on microbial community revealed that IBU significantly inhibited the genera involved in organic degradation (e.g., genus Candidatus Competibacter) and also stimulated those genera (e.g., genus Brachymonas) to secret excess extracellular polymeric substances (EPS), which thus caused sludge bulking in the AS system. The toxicity of IBU and its TPs in the effluent of the AS system was also investigated with Vibrio fischeri bioluminescence inhibition tests and quantitative structure activity relationship (QSAR) analysis by ecological structure-activity relationship (ECOSAR) program. The results indicated that the AS system could effectively eliminate the acute toxicity of both IBU and TPs, but a potential chronic toxicity of IBU could still existed, which could be more harmful to aquatic organisms than that of its TPs. These findings provide an insight into the toxic effects of IBU and its TPs on biological sludge systems and ecosystem.

Jia Y ，Khanal SK ，Yin L ，Sun L ，Lu H ... -  《-》

Comprehensive study of ibuprofen and its metabolites in activated sludge batch experiments and aquatic environment.

Even though Ibuprofen is one of the most studied pharmaceutical in the aquatic environment, there is still a lack of information about its fate and the generation of different transformation products along wastewater treatment plants (WWTPs). Ibuprofen biotransformation products can be generated by human metabolism or by microorganisms present in WWTPs and in natural waters, soils, and sediments, which increase the probability to find them in environment. In this work, the presence of ibuprofen and its main metabolites: ibuprofen carboxylic acid (CBX IBU), 2-hydroxylated ibuprofen (2-OH IBU) and 1-hydroxylated ibuprofen (1-OH IBU), was monitored quantitatively along the biodegradation processes occurring in different batch activated sludge (BAS) experiments under different working conditions. Total ibuprofen removal, achieved in almost all the experiments, was related in part to the formation of the metabolites mentioned. Another ibuprofen metabolite, 1,2-dihydroxy ibuprofen, was detected in BAS experiments for the first time. The metabolites 2-OH IBU and 1-OH IBU remained in solution at the end of ibuprofen biodegradation experiments whereas CBX IBU disappeared faster than hydroxylated metabolites. In addition, also the biodegradation of 1-OH IBU, 2-OH IBU and CBX IBU was evaluated in batch experiments: CBX IBU removal occurred at the highest rate followed by IBU, 2-OH IBU, and 1-OH IBU, which exhibited the lowest removal rate. Finally, Ibuprofen and ibuprofen metabolites were monitored in sewage and natural water samples, where they were found at higher levels than expected: the maximum concentration in influent wastewater samples were 13.74, 5.8, 38.4, 94.0μg/L for IBU, 1-OH IBU, CBX IBU and 2-OH IBU respectively; whereas maximum levels in effluent wastewater samples were 1.9, 1.4, 10.7, 5.9 μg/L for IBU, 1-OH IBU, CBX IBU and 2-OH IBU respectively. High levels of the compounds were also found in river samples, in particular for CBX IBU, which was detected up to 3.9 μg/L.

Ferrando-Climent L ，Collado N ，Buttiglieri G ，Gros M ，Rodriguez-Roda I ，Rodriguez-Mozaz S ，Barceló D ... -  《-》

Metabolite identification of ibuprofen biodegradation by Patulibacter medicamentivorans under aerobic conditions.

Salgado R ，Brito D ，Noronha JP ，Almeida B ，Bronze MR ，Oehmen A ，Carvalho G ，Barreto Crespo MT ... -  《-》

Insights into pharmaceuticals removal in an anaerobic sulfate-reducing bacteria sludge system.

In this study, we examined eight typical and widely detected pharmaceuticals (PhAs) removal in an anaerobic sulfate-reducing bacteria (SRB) sludge system (five antibiotics: sulfadiazine (SD), sulfamethoxazole (SMX), trimethoprim (TMP), ciprofloxacin (CIP) and enoxacin (ENO), and three nonsteroidal anti-inflammatory drugs (NSAIDs): ibuprofen (IBU), ketoprofen (KET) and diclofenac (DIC)). The results showed that the SRB sludge had the higher removal efficacy (20 to 90%) for antibiotics (SD, SMX, TMP, CIP and ENO) than NSAIDs (<20%) via adsorption and biodegradation under different operating conditions. Based on a series of batch studies, fluoroquinolone antibiotics (CIP and ENO) were instantly (<15 min) removed (∼98%) via adsorption on SRB sludge with adsorption coefficient (Kd) as high as 25.3 ± 1.8 L/g-suspended solids (SS). And thermodynamics results indicated that the adsorption of CIP and ENO on SRB sludge was spontaneous (Gibbs free energy change (ΔG°) <0 kJ/mol), exothermic (enthalpy change (ΔH°) <0 kJ/mol), and the adsorption process involved both physisorption and chemisorption (absolute value of ΔH° = 20 to 80 kJ/mol). Three widely prescribed antibiotics (SMX, TMP and CIP) were further investigated for their possible biodegradation pathways along with functional enzymes involved through a series of batch experiments. The biotransformation intermediates indicated that biotransformations of SMX and CIP in SRB sludge system could be initiated from the cleavage of isoxazole and piperazinyl rings catalyzed by sulfite reductase (SR) and cytochrome P450 (CYP450) enzymes, respectively. TMP was likely biotransformed via O-demethylation and N-acetylation coupled with hydroxylation reactions with CYP450 enzymes as the main functional enzymes. This study provided new insight into PhAs removal in SRB sludge system, and has significant potential of implementing sulfur-mediated biological process for the treatment of PhAs containing wastewater.

Jia Y ，Zhang H ，Khanal SK ，Yin L ，Lu H ... -  《-》