Dissertação
Ocorrência e remoção de genes de resistência a antibióticos em sistemas simplificados de tratamento de esgoto, em Belo Horizonte
Fecha
2021-04-26Autor
Letícia da Silva Santos
Institución
Resumen
Antimicrobial resistance has been indicated by the World Health Organization as a global
problem that threatens the gains achieved with the use of antibiotics developed to date. The
intense contact between bacteria, antibiotics and the possibility of horizontal gene transfer are
conditions found in WWTPs that can provide increase in antimicrobial resistance. Thus,
WWTPs are considered important points of bacterias resistants dissemination and ARGs and
have been the subject of studies to understand how these elements spread through the
environment, in order to propose ways to mitigate their spread. The removal of ARGs in sewage
treatment plants has been addressed in several studies, however, knowledge about the dynamics
of these elements in WWTPs is still limited, and further studies are necessary. Thus, the present
study seeks to contribute to the understanding of sewage treatment plants roles in the
dissemination of GRAs, quantifying the genes blaTEM (gives resistance to beta-lactams), sul1
(gives resistance to sulfonamides), tetA (gives resistance tetracillin), intI1 (integron class 1) and
RNAr 16S (genetic marker of bacteria) in three simplified sewage treatment systems. The
monitored systems consist of: (a) UASB reactor followed by a percolating biological filter
(FBP), (b) UASB reactor followed by two high-rate algal ponds in parallel and (c) two vertical
flow constructed wetlands. It was also evaluated a tertiary treatment in the system (a) with a
photoreactor with emerged UV lamps, as well as the influence of the radiation dose in the
removal of ARGs. The results showed concentrations of ARGs ranging from 1E + 06 to 1E +
08 in the raw sewage and from 3E + 04 to 3E + 07 in the treated effluent, considering the three
treatment systems. Overall, removals of each component from the systems resulted in maximum
about 1 log, however, the blaTEM gene was the most susceptible to removal (3.5 logs in
UASB/LAT system), and sul1 was the most persistent. Regarding the photoreactor, no trend
towards an increase in the ARGs removal was identified with an increase in the applied UV
dose. The principal components analysis and Spearman showed that the COD and pH had
greater influence on the concentrations of ARGs than TSS and VSS. In general, it was observed
there was no increase in the concentration of ARGs after wastewater passing through the
treatment systems.