Performance evaluation of anaerobic structured and packed bed bioreactors for sulfamethoxazole and ciprofloxacin antibiotics removal

Author(s)

Rodrigo Braz Carneiro

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2019-09-06

Examining board members

Marcelo Zaiat; Pedro Sérgio Fadini; Paulo Clairmont Feitosa de Lima Gomes; Rogers Ribeiro; Adriano Luiz Tonetti

• Advisor: Marcelo Zaiat; Álvaro José dos Santos Neto

Abstract

The biodegradation of antibiotics in usual biological sewage treatment plants is generally not satisfactory and their presence in wastewater and water supply is aggravated by the fact that these emerging micropollutants promote the development and spread of resistance genes in the environment. In this context, this study aimed to evaluate the removal of sulfamethoxazole (SMX) and ciprofloxacin (CIP) antibiotics in two configurations of anaerobic fixed bed reactors -structured (ASBR) and packed (APBR). The reactors achieved high performance in the removal of COD (93 ± 2 %), SMX (93 ± 4 %) and CIP (85 ± 10 %), applying lab-made sewage and hydraulic retention time (HRT) of 12 h. ASBR showed greater potential of application in operational and economic terms, since it presented smaller amount of support material and equivalent or higher performance compared to APBR. The HRT reduction to 4 h led to a decrease in the removal efficiency of COD (79 ± 6 % in APBR; 88 ± 5 % in ASBR), SMX (69 ± 7 % in APBR; 81 ± 7 % in ASBR) and CIP (66 ± 8 % in APBR; 64 ± 8 % in ASBR), likely due to the smaller time of substrate-biomass contact in the biofilm. The application of domestic sewage as a feed substrate for the reactors in HRT of 12 h led to a decrease in the system performance – COD (80 ± 7 %), SMX (77 ± 9 % in APBR; 73 ± 13 % in ASBR), and CIP (67 ± 19 % in APBR; 72 ± 14 % in ASBR), due to the alteration of the microbial community in the reactors bed, since it was observed a drastic reduction in the population of methanogenic archaea, mainly hydrogenotrophic, and of bacteria of the genus Clostridium and Bacillus, associated to the antibiotics biodegradation. The HRT decrease did not affect the apparent removal kinetic constant of the compounds but resulted in higher effluent residual concentration. Applying domestic sewage, the removal kinetic constants were reduced, indicating the decrease of the pharmaceutical\'s biodegradation capacity. The SMX and CIP elimination was practically due to biotransformation, but CIP removal was influenced by the sorption mechanism onto the biomass, since a high logKD (2.6 to 2.8 L kg-1SS) was obtained. The effluent from the reactors neither presented an acute and chronic ecotoxicological potential on Chironomus sancticaroli nor antimicrobial activity on the microorganisms Ochrobactrum sp., Brevundimonas sp., Sphingomonas sp. and Escherichia coli. The analysis of the molecular structures of the identified transformation products revealed that they maintained the structure of quinolone and sulfonamide intact and could present residual bioactivity. The evaluation of the SMX and other organic micropollutants biodegradation during acidogenesis showed that each stage of anaerobic digestion can act differently on the biotransformation of the compounds due to enzymatic mechanisms and specific microorganisms of each stage. The results obtained in this study proved the potential of fixed bed anaerobic bioreactors in the removal of pharmaceutical compounds present in sewage, especially the sulfonamides and fluoroquinolones antibiotics, and represent a primary barrier to the dispersion of these micropollutants into the environment. (AU)

• FAPESP's process: 15/04427-4 - Performance evaluation of structured and packed bed reactor for removal of sulfamethoxazole and ciprofloxacin
• Grantee: Rodrigo Braz Carneiro
• Support Opportunities: Scholarships in Brazil - Doctorate