Probing the degradation of pharmaceuticals in urine using MFC and studying their removal efficiency by UPLC-MS/MS

Abstract

Nutrient recovery from source-separated human urine has attracted interest as it is rich in nitrogen and phosphorus that can be utilized as fertilizer. However, urine also contains pharmaceuticals, steroid hormones, etc. and their removal is crucial as they have detrimental effects on the environment and human health. The current study focuses on investigating the degradation of pharmaceuticals using a double-chamber microbial fuel cell (MFC). Urine was spiked with four pharmaceuticals (trimethoprim, lamivudine, levofloxacin, and estrone) at a concentration of 2 μg/mL. The MFC was operated for 7 months in batch mode with this spiked urine as feed. The degradation efficiency of the MFC was studied, for which a selective liquid chromatography-tandem mass-spectrometric method was developed for the quantitation of compounds used in the spiking experiments and was validated with a lower limit of quantification of 0.39 ng/mL. The maximum removal rate achieved was 96% ± 2%. The degradation mechanism involved processes like sorption and anoxic biodegradation. The voltage curve obtained showed that the presence of pharmaceuticals had an initial negative impact on power generation along with increased organic content; however, after the reactor acclimatization, increased power output was achieved with maximum organics removal at 30 h of retention time. This work opens a new perspective for the anoxic biodegradation of pharmaceuticals and can be useful in future bioremediation studies.

Keywords: Biodegradation; Liquid chromatography mass spectroscopy; MFC; Pharmaceuticals; Urine.

Graphical abstract

Fig. 1

Voltage curve of microbial fuel cell (MFC) reactor at different phases of pharmaceuticals addition. Phase 1: fresh urine without any pharmaceutical, Phase 2: EST spiked urine, Phase 3: TRI and EST spiked urine, Phase 4: 3TC, TRI, and EST spiked urine and Phase 5: LFL, 3TC, TRI, and EST spiked urine.

Fig. 2

Change in chemical oxygen demand (COD) in MFC at different phases with different pharmaceuticals addition. Phase 1: fresh urine without any pharmaceutical, Phase 2: EST spiked urine, Phase 3: TRI and EST spiked urine, Phase 4: 3TC, TRI, and EST spiked urine and Phase 5: LFL, 3TC, TRI, and EST spiked urine.

Fig. 3

Chromatogram and positive ion electrospray mass spectra of LFL; (A) MRM of CIP (retention time: 4.4 min), (B) MRM of LFL (retention time: 4.1 min), (C) product ion spectra of LFL. LFL: levofloxacin; MRM: multiple reaction monitoring; CIP: ciprofloxacin.

Fig. 4

Chromatogram and positive ion electrospray mass spectra of TRI and 3TC; (A) MRM of CBZ (retention time: 5.5 min), (B) MRM of TRI (retention time: 2.9 min), (C) MRM of 3TC (retention time: 3.1 min), (D) product ion spectra of TRI, (E) product ion spectra of 3TC. TRI: trimethoprim; 3TC: lamivudine; CBZ: carbamazepine.

Fig. 5

Chromatogram and positive ion electrospray mass spectra of EST. (A) MRM of DXM (RT = 3.8 min), (B) MRM of EST (RT = 4.25 min), (C) Product ion spectra of EST.

Fig. 6

Variation in effluent concentration of spiked pharmaceuticals with time.