Effects of activated sludge and UV disinfection processes on the bacterial community and antibiotic resistance profile in a municipal wastewater treatment plant

• Published in: Environmental science and pollution research international Vol. 29; no. 24; pp. 36088 - 36099
• Main Authors: Dias, Marcela França, Leroy-Freitas, Deborah, Machado, Elayne Cristina, da Silva Santos, Leticia, Leal, Cintia Dutra, da Rocha Fernandes, Gabriel, de Araújo, Juliana Calábria
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-05-2022; Springer Nature B.V
• Subjects: Activated sludge; Angiotensin Receptor Antagonists - pharmacology; Angiotensin-Converting Enzyme Inhibitors; Anti-Bacterial Agents - pharmacology; Antibiotic resistance; Antibiotics; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Bacteria; Bacteria - genetics; Cephalexin; Ciprofloxacin; Disinfectants; Disinfection; Drug resistance; Drug Resistance, Microbial - genetics; Earth and Environmental Science; Ecotoxicology; Effluents; Environment; Environmental Chemistry; Environmental Health; Environmental science; Genes, Bacterial; Heterotrophic bacteria; Irradiation; Metagenomics; Microorganisms; Municipal wastewater; Research Article; Sewage - microbiology; Sludge; Sulfamethoxazole; Tertiary treatment; Ultraviolet radiation; Waste Water - microbiology; Waste Water Technology; Wastewater treatment; Wastewater treatment plants; Water Management; Water Pollution Control; Water Purification; Water treatment; 16S RRNA; Metagenomics; Wastewater; Antibiotic resistance genes; Tertiary treatment; Antibiotic resistant bacteria
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-022-18749-3

Wastewater tertiary treatment has been pointed out as an effective alternative for reducing the concentration of antibiotic resistant bacteria and genes (ARB and ARGs) in wastewaters. The present work aimed to build on the current knowledge about the effects of activated sludge and UV irradiation on antibiotic resistance determinants in biologically treated wastewaters. For that, the microbial community and ARGs’ composition of samples collected after preliminary (APT), secondary (AST), and tertiary (ATT) treatments in a full-scale wastewater treatment plant using a modified activated sludge (MAS) system followed by an UV stage (16 mJ/cm
2
) were investigated through culture-dependent and independent approaches (including metagenomics). A total of 24 phyla and 460 genera were identified, with predominance of Gammaproteobacteria in all samples. Pathogenic genera corresponded to 8.6% of all sequences on average, mainly
Acinetobacter
and
Streptococcus
. Significant differences (
p
 < 0.05) in the proportion of pathogens were observed between APT and the other samples, suggesting that the secondary treatment reduced its abundance. The MAS achieved 64.0–99.7% average removal efficiency for total (THB) and resistant heterotrophic bacteria, although the proportions of ARB/THB have increased for sulfamethoxazole, cephalexin, ciprofloxacin, and tetracycline. A total of 10
7
copies/mL of
intI1
gene remained in the final effluent, suggesting that the treatment did not significantly remove this gene and possibly other ARGs. In accordance, metagenomic results suggested that number of reads recruited to plasmid-associated ARGs became more abundant in the pool throughout the treatment, suggesting that it affected more the bacteria without these ARGs than those with it. In conclusion, disinfected effluents are still a potential source for ARB and ARGs, which highlights the importance to investigate ways to mitigate their release into the environment.