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Avaliação da segurança microbiológica de framboesas produzidas em estufa irrigadas com águas residuais tratadas e reutilizáveis
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A água é o recurso mais precioso do planeta, pelo que, a sua conservação
constitui um dos desafios mais importantes do desenvolvimento sustentável. No entanto,
sabe-se que este recurso tem sido mal aproveitado e que a sua escassez é uma realidade.
A agricultura é o setor de intervenção humana com maior impacto no consumo de água,
utilizando cerca de 70% deste recurso híbrido natural. Assim, algumas alternativas
como a reutilização da água residual (AR) tratada na rega agrícola, por exemplo, tem
sido considerada como uma prática sustentável e recomendável.
No entanto, os tratamentos convencionalmente aplicados nas Estações de
Tratamento de Água Residuais (ETARs) são ainda considerados insuficientes na
remoção/inativação de diversos agentes patogénicos causadores de doenças infeciosas,
incluindo bactérias resistentes a antibióticos e vírus patogénicos humanos, que são
libertados para o meio ambiente constituindo um perigo para a saúde pública. Mais
ainda, a reutilização deste tipo de águas tratadas convencionalmente na rega agrícola
pode ser nocivo, uma vez que estes agentes podem persistir ou ser internalizados pelas
plantas irrigadas.
Atualmente, a avaliação da qualidade das AR é efetuada com recurso a bactérias
indicadoras de contaminação fecal, sendo os mais comummente utilizados, os
coliformes fecais, em particular Escherichia coli. Vários estudos também têm vindo a
demonstrar a importância de utilizar as partículas virais, a partir de análises dos seus
genomas, como possíveis indicadores de contaminação fecal nas águas.
Desta forma, o presente trabalho teve como principal objetivo a avaliação da
segurança microbiológica de framboesas produzidas em estufa, irrigadas durante cinco
meses, com três tipos de AR tratadas: 1 – Efluente após tratamento secundário; 2 -
Efluente reutilizável, após o tratamento terciário; 3 - Efluente secundário seguido de
uma nanofiltração in-house. Como controlo foi utilizado a água da rede pública.
Amostras de substrato, folhas e fruto irrigados com cada tipo de água foram avaliadas
ao longo do tempo para a presença de bactérias resistentes a carbapenemos e
(fluoro)quinolonas, genes de resistência aos antibióticos (carbapenemos – blaKPC,
blaOXA48, blaNDM, blaVIM, blaIMP, e (fluoro)quinolonas qnrA, qnrB, qnrS), e de seis
genomas virais: Norovírus (NoV) GI/GII, Hepatite A e E (HAV e HEV), Adenovírus e
Poliomavírus), através de protocolos de multiplex qPCR.
Nas amostras de substrato, folhas e fruto não foram detetados os oito genes de
resistência em estudo. No entanto, os genomas virais de NoV GII e HEV foram
detetados com concentrações superiores a 103
cópias de genoma/g nas amostras de
substrato, folhas e fruto irrigados com o efluente reutilizável, efluente após tratamento
com nanofiltração, e efluente secundário. A sua deteção não significa que os respetivos
vírus estejam ativos ou infeciosos, mas a sua presença poderá representar um perigo de
saúde pública. Assim, é necessário otimizar o tipo de tratamentos aplicados nas ETARs,
a fim de se obter AR tratadas e microbiologicamente seguras de modo a serem
reutilizadas, por exemplo, na rega agrícola.
Abstract Water is the planet´s most precious resource, and its conservation is one of the most important challenges of sustainable development. However, it is known that this resource has been misused and that its scarcity is a reality. Agriculture is the sector of human intervention with the greatest impact on water consumption, using about 70% of this natural hybrid resource. Thus, some alternatives such as the reuse of treated wastewater (WW) in agricultural irrigation, for example, have been considered a sustainable and recommendable practice. However, the treatments conventionally applied in Wastewater Treatment Plants (WWTPs) are still considered inefficient in removing/inactivating several pathogens causing infectious diseases, including antibiotic resistant bacteria and human pathogenic viruses, which are released into the environment constituting a danger to public health. Moreover, the reuse of this type of conventionally treated water in agricultural irrigation can be harmful, since these agents can persist or be internalized by the irrigated plants. Currently, the evaluation of the quality of WW is performed using indicator bacteria of faecal contamination, being the most commonly used, the faecal coliforms, in particular Escherichia coli. Several studies have also demonstrated the importance of using viral particles, from analysis of their genomes, as possible indicators of faecal contamination in water. Thus, the present work had as main objective the evaluation of the microbiological safety of raspberries produced in greenhouse, irrigated for five months with three types of treated WW: 1 – Effluent after secondary treatment; 2 - Reusable effluent after tertiary treatment; 3 - Secondary effluent followed by an in-house nanofiltration. As a control, water from the public mains was used. Samples of substrate, leaves and fruit irrigated with each type of water were evaluated over time for the presence of bacteria resistant to carbapenems and (fluoro)quinolones, antibiotic resistance genes (carbapenems - blaKPC, blaOXA48, blaNDM, blaVIM, blaIMP, and (fluoro)quinolones qnrA, qnrB, qnrS), and of six viral genomes: Norovirus (NoV) GI/GII, Hepatitis A and E (HAV and HEV), Adenovirus and Polyomavirus) using multiplex qPCR protocols. In the substrate, leaf, and fruit samples, the eight studied resistance genes were not detected. However, NoV GII and HEV viral genomes were detected with concentrations higher than 103 genome copies/g in the substrate, leaf and fruit samples irrigated with the reusable effluent, effluent after nanofiltration treatment, and secondary effluent. Their detection does not mean that the respective viruses are active or infectious, but their presence may represent a public health hazard. Thus, it is necessary to optimize the type of treatments applied in the WWTPs, in order to obtain microbiologically safe treated WW so that they can be reused, for example, in agricultural irrigation.
Abstract Water is the planet´s most precious resource, and its conservation is one of the most important challenges of sustainable development. However, it is known that this resource has been misused and that its scarcity is a reality. Agriculture is the sector of human intervention with the greatest impact on water consumption, using about 70% of this natural hybrid resource. Thus, some alternatives such as the reuse of treated wastewater (WW) in agricultural irrigation, for example, have been considered a sustainable and recommendable practice. However, the treatments conventionally applied in Wastewater Treatment Plants (WWTPs) are still considered inefficient in removing/inactivating several pathogens causing infectious diseases, including antibiotic resistant bacteria and human pathogenic viruses, which are released into the environment constituting a danger to public health. Moreover, the reuse of this type of conventionally treated water in agricultural irrigation can be harmful, since these agents can persist or be internalized by the irrigated plants. Currently, the evaluation of the quality of WW is performed using indicator bacteria of faecal contamination, being the most commonly used, the faecal coliforms, in particular Escherichia coli. Several studies have also demonstrated the importance of using viral particles, from analysis of their genomes, as possible indicators of faecal contamination in water. Thus, the present work had as main objective the evaluation of the microbiological safety of raspberries produced in greenhouse, irrigated for five months with three types of treated WW: 1 – Effluent after secondary treatment; 2 - Reusable effluent after tertiary treatment; 3 - Secondary effluent followed by an in-house nanofiltration. As a control, water from the public mains was used. Samples of substrate, leaves and fruit irrigated with each type of water were evaluated over time for the presence of bacteria resistant to carbapenems and (fluoro)quinolones, antibiotic resistance genes (carbapenems - blaKPC, blaOXA48, blaNDM, blaVIM, blaIMP, and (fluoro)quinolones qnrA, qnrB, qnrS), and of six viral genomes: Norovirus (NoV) GI/GII, Hepatitis A and E (HAV and HEV), Adenovirus and Polyomavirus) using multiplex qPCR protocols. In the substrate, leaf, and fruit samples, the eight studied resistance genes were not detected. However, NoV GII and HEV viral genomes were detected with concentrations higher than 103 genome copies/g in the substrate, leaf and fruit samples irrigated with the reusable effluent, effluent after nanofiltration treatment, and secondary effluent. Their detection does not mean that the respective viruses are active or infectious, but their presence may represent a public health hazard. Thus, it is necessary to optimize the type of treatments applied in the WWTPs, in order to obtain microbiologically safe treated WW so that they can be reused, for example, in agricultural irrigation.
Descrição
Palavras-chave
Microbiologia médica Biologia molecular Saúde pública Reutilização de AR qPCR Genes de resistência a antibióticos Genomas virais Irrigação de framboesas.