Journal
WATER RESEARCH
Volume 161, Issue -, Pages 191-201Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.watres.2019.06.010
Keywords
Sulfate-reducing bacteria (SRB); Pharmaceuticals removal; Biotransformation; Adsorption; Sulfate reduction
Funding
- Natural Science Foundation of China [51778643, 51638005]
- Pearl River S&T Nova Program of Guangdong [201504281527416]
- Tip-top Scientific and Technical Innovative Youth Talents of Guangdong Special Support Program [2016TQ03Z336]
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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 (similar to 98%) via adsorption on SRB sludge with adsorption coefficient (K-d) 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 (Delta G degrees) <0 kJ/mol), exothermic (enthalpy change (Delta H degrees) <0 kJ/mol), and the adsorption process involved both physisorption and chemisorption (absolute value of Delta H degrees = 20 to 80 kJ/mol). Three widely prescribed antibiotics (SMX, TMP and an) 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. (C) 2019 Elsevier Ltd. All rights reserved.
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