Incidencia de las tecnologías de tratamiento en el sector sanitario sobre la diseminación de resistencia a antimicrobianos para el potencial reúso de las aguas servidas tratadas.
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Date
2024
Journal Title
Journal ISSN
Volume Title
Publisher
Universidad de Concepción
Abstract
La resistencia a antimicrobianos (RAM) es un desafío que debe ser abordada desde una perspectiva interdisciplinaria. El uso indiscriminado de antimicrobianos por parte de la industria agropecuaria, acuícola, veterinaria y farmacéutica, han convertido a la RAM en un problema no sólo para la salud pública, sino que también para el medio ambiente.
Las plantas de tratamiento de aguas servidas (PTAS) han sido consideradas como un reservorio de diseminación de RAM para el medio ambiente. Dentro de sus principales componentes, las aguas servidas (AS) presentan concentraciones de antimicrobianos y abundancias de bacterias y genes de resistencia a antimicrobianos (BRA y GRA, respectivamente); elementos responsables de la diseminación de RAM. En general, las PTAS consisten en un tratamiento secuencial de procesos físicos, químicos y biológicos, donde éste último tiene un rol primordial en esta problemática. En los reactores biológicos, generalmente utilizados como tratamiento secundario, las AS entran en contacto con las bacterias propias del tratamiento siendo un ambiente ideal para la diseminación de la RAM. Las concentraciones y abundancias de materia orgánica, nutrientes y antimicrobianos, BRA y GRA junto con las condiciones de temperatura, oxígeno disuelto y tiempo de retención hidráulico generan un escenario propicio para el crecimiento bacteriano y para el intercambio genético de GRAs. Es así como el tratamiento biológico es una etapa que es necesaria estudiar para comprender cómo las diferentes tecnologías pueden tener un efecto sobre las eficiencias de eliminación y comunidades bacterianas.
Por otro lado, las PTAS actúan también como una fuente de diseminación en el medio ambiente, ya que sus efluentes son descargados a los cuerpos de agua como ríos, lagos u océanos. Debido al escenario de escasez hídrica y la aplicación de la economía circular, los efluentes de las PTAS, conocidos como aguas servidas tratadas (AST), están siendo consideradas como una nueva fuente de agua para el riego agrícola. La presencia de antimicrobianos, BRA y GRA pone en riesgo un reúso seguro tanto para la salud pública como también para el medio ambiente. Es por esta razón que los posibles impactos, en relación con la diseminación de la RAM, son necesarios de ser estudiados.
Ante este contexto, el objetivo principal de esta tesis doctoral fue evaluar la incidencia de las tecnologías en el sector sanitario sobre la diseminación de RAM para el potencial reúso de las aguas servidas tratadas (AST). En primer lugar, se evaluó el desempeño de las diferentes tecnologías en la eliminación de antimicrobianos en la corriente líquida (Capítulos III, IV; V, VI y VII). Luego, se analizó las comunidades microbianas (Capítulo VIII) y finalmente, se evaluó el potencial reúso de las AST provenientes de las diferentes tecnologías de tratamiento (Capítulos VII, VIII y XI). Para cumplir con dicho objetivo, se evaluaron diferentes tipos de tecnologías biológicas convencionales y no convencionales presentes en el sector sanitario. En el caso de las tecnologías convencionales, se utilizaron los sistemas de lodos activados (LA) y biodiscos (BD) mientras que, en las no convencionales, se evaluaron los sistemas de humedales construidos (HC) y vermifiltros (VF). Es importante mencionar que estas tecnologías se encuentran instaladas en la región del Biobío, Chile. En general, se tomaron muestras de agua tanto de los influentes (I) como efluentes secundarios (ES) y finales (EF) y se determinaron la presencia de los elementos de diseminación de RAM (antimicrobianos, BRA y GRAs), parámetros fisicoquímicos y microbiológicos para determinar el desempeño de las diferentes tecnologías. Asimismo, se evaluaron las comunidades bacterianas presentes a través de secuenciación masiva del gen ADNr 16S. Finalmente, con todos estos resultados, se determinó el potencial reúso de las AST generadas por las diferentes PTAS evaluadas.
Los principales resultados de esta tesis doctoral demostraron que las tecnologías convencionales y no convencionales presentan eficiencias de eliminación de antimicrobianos y reducciones de coliformes, BRA y GRAs que fluctuaron entre 20 – 90%, 4,1 – 4,5 unidades logarítmicas (ulog), 2,6 – 4,6 ulog y 2,3 – 4,0 ulog, respectivamente. Los análisis estadísticos reportaron que no existen diferencias significativas entre las diferentes tecnologías evaluadas (p > 0,05). Sin embargo, si se reportaron diferencias entre I y EF considerando todas las PTAS evaluadas. Este resultado demuestra que las PTAS instaladas son capaces de reducir las concentraciones y abundancias de los elementos responsables de la RAM y disminuir los riesgos asociados a esta problemática.
En cuanto a las comunidades microbianas presentes, los análisis filogenéticos reportaron que la composición de las comunidades bacterianas es similar e independiente del tipo de tecnología biológica evaluado donde predomina en más de un 50% los phyla Proteobacteria y Bacteroidota. Siguiendo la misma tendencia de los resultados asociados a los desempeños de las diferentes PTAS, los análisis estadísticos demuestran que existen diferencias entre las muestras I y EF lo que indica que las PTAS son capaces de reducir la diseminación de RAM. Además, se reportaron correlaciones positivas entre algunas comunidades bacterianas perteneciente al phyla Proteobacteria, GRA, BRA y coliformes.
Finalmente, al evaluar el potencial reúso de las AST en la agricultura, se puede constatar que a pesar de que las PTAS son capaces de reducir las abundancias de GRAs, se reportaron abundancias entre 1,2 – 5,2 log (copias/mL), donde no existen diferencias significativas entre las tecnologías biológicas (p > 0,05). Cuando los cultivos son irrigados con AST, estos valores varían dependiendo del tipo de cultivo y del tejido. En el caso de plantas de consumo directo como la lechuga (Lactuca sativa), las abundancias de GRAs son mayores en la hoja que en los suelos. En esta circunstancia, si existe un potencial riesgo de diseminación de RAM asociado al consumo de este tipo de hortalizas.
Antimicrobial resistance (AMR) is a challenge that must be addressed from an interdisciplinary perspective. The indiscriminate use of antimicrobials by the agricultural, aquaculture, veterinary, and pharmaceutical industries has turned AMR into a problem not only for public health but also for the environment. Wastewater treatment plants (WWTPs) have been considered as a reservoir for the spread of AMR in the environment. Among their main components, wastewater presents concentrations of antimicrobials and abundances of bacteria and antimicrobial resistance genes (ARB and ARGs, respectively), elements responsible for the spread of AMR. In general, WWTPs consist of a sequential treatment involving physical, chemical, and biological processes, with the latter playing a crucial role in this issue. In biological reactors, commonly used as secondary treatment, wastewater comes into contact with the bacteria inherent to the treatment, creating an ideal environment for the dissemination of AMR. The concentrations and abundances of organic matter, nutrients, antimicrobials, BRA, and GRA, along with conditions such as temperature, dissolved oxygen, and hydraulic retention time, create a favorable scenario for bacterial growth and genetic exchange of GRAs. For this reason, the biological treatment is a stage that is necessary to study to understand how different technologies may impact removal efficiencies and bacterial communities. On the other hand, WWTPs also act as a source of dissemination in the environment since their effluents are discharged into water bodies such as rivers, lakes, or oceans. Due to the scenario of water scarcity and the implementation of the circular economy, the effluents from WWTPs, known as treated wastewater (TWW), are being considered as a new source of water for agricultural irrigation. The presence of antimicrobials, BRA, and GRA poses a risk for safe reuse, both for public health and the environment. This is why the potential impacts, concerning the spread of AMR, need to be studied. In this context, the main objective of this doctoral thesis was to assess the impact of technologies in the sanitary sector on the spread of AMR for the potential reuse of treated wastewater (TWW). Firstly, the performance of different technologies in the removal of antimicrobials in the liquid stream was evaluated (Chapters III, IV; V, VI y VII). Subsequently, microbial communities were analyzed (Chapter VIII), and finally, the potential reuse of TWW from different treatment technologies was assessed (Chapter VII, VIII y XI XX). To achieve this objective, various types of conventional and non-conventional biological technologies in the sanitary sector were evaluated. In the case of conventional technologies, activated sludge (AS) and biodiscs (BD) systems were used, while non-conventional systems such as constructed wetlands (CW) and vermifilters (VF) were assessed. It's important to mention that these technologies are installed in the Biobío region, Chile. In general, water samples were taken from both the influents (I), secondary (SE) and final effluents (FE). The presence of elements related to the spread of AMR (antimicrobials, BRA, and GRAs), physicochemical and microbiological parameters were determined to assess the performance of different technologies. Additionally, bacterial communities were evaluated through massive sequencing of the 16S rDNA gene. Finally, based on all these results, the potential reuse of treated wastewater generated by the different WWTPs was determined. The main results of this doctoral thesis demonstrated that both conventional and non-conventional technologies show efficiencies in antimicrobial removal and reductions in coliforms, ARGs, and ARB ranging from 20% to 90%, 4.1 to 4.5 log units, 2.6 to 4.6 log units, and 2.3 to 4.0 log units, respectively. Statistical analyses reported no significant differences among the various evaluated technologies (p > 0.05). However, differences were reported between I and FE considering all evaluated WWTPs. This result indicates that WWTPs can reduce the concentrations and abundances of elements responsible for antimicrobial resistance and decrease associated risks. Regarding the present microbial communities, phylogenetic analyses reported that the composition of bacterial communities is similar and independent of the type of biological technology evaluated, where the phyla Proteobacteria and Bacteroidota predominate by more than 50%. Consistent with the trends in the results associated with the performances of different WWTPs, statistical analyses show differences between I and FE samples, indicating that WWTPs can reduce the spread of ARM. Furthermore, positive correlations were reported between certain bacterial communities belonging to the phylum Proteobacteria, ARGs, ARB, and coliforms. Finally, when evaluating the potential reuse of TWW in agriculture, it can be observed that, although WWTPs can reduce ARGs, the abundances between 1.2 to 5.2 log (copies/mL) were reported, with no significant differences between biological technologies (p > 0.05). When crops are irrigated with TWW, these values vary depending on the type of crop and tissue. In the case of direct consumption plants like lettuce (Lactuca sativa), ARGs abundances are higher in the leaves than in the soils. In this circumstance, there is a potential risk of antimicrobial resistance dissemination associated with the consumption of these types of vegetables.
Antimicrobial resistance (AMR) is a challenge that must be addressed from an interdisciplinary perspective. The indiscriminate use of antimicrobials by the agricultural, aquaculture, veterinary, and pharmaceutical industries has turned AMR into a problem not only for public health but also for the environment. Wastewater treatment plants (WWTPs) have been considered as a reservoir for the spread of AMR in the environment. Among their main components, wastewater presents concentrations of antimicrobials and abundances of bacteria and antimicrobial resistance genes (ARB and ARGs, respectively), elements responsible for the spread of AMR. In general, WWTPs consist of a sequential treatment involving physical, chemical, and biological processes, with the latter playing a crucial role in this issue. In biological reactors, commonly used as secondary treatment, wastewater comes into contact with the bacteria inherent to the treatment, creating an ideal environment for the dissemination of AMR. The concentrations and abundances of organic matter, nutrients, antimicrobials, BRA, and GRA, along with conditions such as temperature, dissolved oxygen, and hydraulic retention time, create a favorable scenario for bacterial growth and genetic exchange of GRAs. For this reason, the biological treatment is a stage that is necessary to study to understand how different technologies may impact removal efficiencies and bacterial communities. On the other hand, WWTPs also act as a source of dissemination in the environment since their effluents are discharged into water bodies such as rivers, lakes, or oceans. Due to the scenario of water scarcity and the implementation of the circular economy, the effluents from WWTPs, known as treated wastewater (TWW), are being considered as a new source of water for agricultural irrigation. The presence of antimicrobials, BRA, and GRA poses a risk for safe reuse, both for public health and the environment. This is why the potential impacts, concerning the spread of AMR, need to be studied. In this context, the main objective of this doctoral thesis was to assess the impact of technologies in the sanitary sector on the spread of AMR for the potential reuse of treated wastewater (TWW). Firstly, the performance of different technologies in the removal of antimicrobials in the liquid stream was evaluated (Chapters III, IV; V, VI y VII). Subsequently, microbial communities were analyzed (Chapter VIII), and finally, the potential reuse of TWW from different treatment technologies was assessed (Chapter VII, VIII y XI XX). To achieve this objective, various types of conventional and non-conventional biological technologies in the sanitary sector were evaluated. In the case of conventional technologies, activated sludge (AS) and biodiscs (BD) systems were used, while non-conventional systems such as constructed wetlands (CW) and vermifilters (VF) were assessed. It's important to mention that these technologies are installed in the Biobío region, Chile. In general, water samples were taken from both the influents (I), secondary (SE) and final effluents (FE). The presence of elements related to the spread of AMR (antimicrobials, BRA, and GRAs), physicochemical and microbiological parameters were determined to assess the performance of different technologies. Additionally, bacterial communities were evaluated through massive sequencing of the 16S rDNA gene. Finally, based on all these results, the potential reuse of treated wastewater generated by the different WWTPs was determined. The main results of this doctoral thesis demonstrated that both conventional and non-conventional technologies show efficiencies in antimicrobial removal and reductions in coliforms, ARGs, and ARB ranging from 20% to 90%, 4.1 to 4.5 log units, 2.6 to 4.6 log units, and 2.3 to 4.0 log units, respectively. Statistical analyses reported no significant differences among the various evaluated technologies (p > 0.05). However, differences were reported between I and FE considering all evaluated WWTPs. This result indicates that WWTPs can reduce the concentrations and abundances of elements responsible for antimicrobial resistance and decrease associated risks. Regarding the present microbial communities, phylogenetic analyses reported that the composition of bacterial communities is similar and independent of the type of biological technology evaluated, where the phyla Proteobacteria and Bacteroidota predominate by more than 50%. Consistent with the trends in the results associated with the performances of different WWTPs, statistical analyses show differences between I and FE samples, indicating that WWTPs can reduce the spread of ARM. Furthermore, positive correlations were reported between certain bacterial communities belonging to the phylum Proteobacteria, ARGs, ARB, and coliforms. Finally, when evaluating the potential reuse of TWW in agriculture, it can be observed that, although WWTPs can reduce ARGs, the abundances between 1.2 to 5.2 log (copies/mL) were reported, with no significant differences between biological technologies (p > 0.05). When crops are irrigated with TWW, these values vary depending on the type of crop and tissue. In the case of direct consumption plants like lettuce (Lactuca sativa), ARGs abundances are higher in the leaves than in the soils. In this circumstance, there is a potential risk of antimicrobial resistance dissemination associated with the consumption of these types of vegetables.
Description
Tesis presentada para optar al grado de Doctora en Ciencias Ambientales con Mención en Sistemas Acuáticos Continentales
Keywords
Aguas servidas, Antimicrobianos, Medio ambiente