Loading...
Publication
Otimização do tratamento terciário de águas residuais urbanas através da utilização de microalgas
| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 1.73 MB | Adobe PDF |
Authors
Advisor(s)
Abstract(s)
A utilização de microalgas no tratamento de águas residuais tem despertado o interesse
da comunidade científica a nível internacional, como tecnologia promissora, constituindo
uma alternativa mais sustentável aos sistemas de tratamento convencionais, que
continuam a ser grandes consumidores de energia.
O presente trabalho integra-se dentro dos objetivos do projeto de investigação
“GreenTreat”, onde foram instalados 9 fotobiorreatores GreenDune (PBR), na ETAR da
Quinta do Lago, com uma capacidade de 450 L cada e com uma área de implantação no
terreno de cerca de 1 m2. Foram instalados em 3 linhas, que funcionam em paralelo, cada
uma composta por 3 unidades sequenciais.
Pretendeu-se otimizar a remoção dos principais nutrientes N, P e amónia (NH4+), assim
como dos parâmetros microbiológicos Escherichia coli (E. coli) e Enterococos intestinais,
recorrendo à configuração do parâmetro operacional Tempo de Retenção Hidráulico
(TRH), aproveitando o efeito desinfetante das culturas de microalgas para melhorar a
qualidade do efluente final, cumprindo as condições de descarga e viabilizando a sua
reutilização.
Para tal, foram monitorizadas as condições locais do efluente, em termos de pH e
temperatura (ºC), assim como foram analisadas as características físico-químicas e
microbiológicas do efluente tratado pelo processo proposto e estudados, de acordo com a
legislação em vigor, os possíveis cenários de reutilização.
Os resultados permitiram confirmar que os sistemas que recorrem à utilização de
microalgas possuem elevada eficiência na remoção de nutrientes, em especial de NH4+
(entre 60% e 90%), assim como, possuem elevado potencial de desinfeção, uma vez que,
no decorrer do processo de fotossíntese, as microalgas consomem grandes quantidades
de CO2, levando ao aumento do pH e impossibilitando a sobrevivência de organismos
patogénicos, devido ao ambiente hostil criado.
Por outro lado, este sistema específico, mostrou-se ineficiente na remoção de sólidos
suspensos totais (SST), pelo facto de a etapa de decantação/sedimentação não se encontrar
devidamente dimensionada, levando a que os sólidos/biomassa em suspensão,
característicos de processos que recorrem à utilização de microalgas, não
decantem/sedimentem nas melhores condições, inviabilizando a reutilização, para
quaisquer dos usos possíveis No entanto e, uma vez que para o uso urbano, apenas o valor de SST não cumpre o
estipulado na legislação, pode dizer-se que, caso fosse possível melhorar a etapa de
decantação/sedimentação, nomeadamente no que diz respeito ao seu dimensionamento, a
probabilidade deste parâmetro também vir a cumprir, seria grande, podendo, desta forma,
vir a reutilizar-se a água residual tratada para Lavagens de Ruas e Suporte dos
Ecossistemas.
Para os restantes parâmetros analisados, foram registados valores abaixo do seu Valor
Limite de Emissão (VLE), tendo sido obtidos melhores resultados, em termos globais,
para o TRH de ± 2 dias.
The use of microalgae in wastewater treatment has drawn increased interest among the international scientific community as a promising technology, constituting a more sustainable alternative to conventional treatment systems, which remain major energy consumers. The present work is integrated within the objectives of the research project "GreenTreat", where 9 GreenDune photobioreactors (PBR) were installed in the ETAR of Quinta do Lago. These photobioreactors, with a capacity of 450 L each and with a field deployment area of about 1 m2, were installed in 3 lines, which work in parallel, each one composed of 3 sequential units. The aim was to optimize the removal of the main nutrients N, P and ammonia (NH4+), as well as the microbiological parameters Escherichia coli (E. coli) and Intestinal Enterococci, using the configuration of the hydraulic retention time (HRT) operating parameter, taking advantage of the disinfectant effect of microalgae to improve the quality of the final effluent, complying with the discharge conditions and enabling its reuse. Accordingly, the local effluent conditions were monitored in terms of pH and temperature (ºC), as well as the physical-chemical and microbiological characteristics of the effluent treated by the process proposed. Finally, the possible scenarios of reuse were studied, in accordance with the current legislation. Results confirmed that the systems that use microalgae have high efficiency in nutrient removal, especially NH4+ (between 60% and 90%), and they have a high disinfection potential. Indeed, during the photosynthesis process, microalgae consume large amounts of CO2, leading to increased pH and making it impossible for pathogenic organisms to survive, due to the hostile environment created. On the other hand, this specific system proved to be inefficient in the removal of total suspended solids (TSS), because the decanting/sedimentation stage was not properly sized, preventing solids/biomass in suspension (characteristic of processes that use microalgae) to decant/sediment in the best conditions, making impossible its reuse, for any of the possible uses. However, since for urban use, only the value of TSS does not comply with the provisions of the legislation, it can be assumed that, if it were possible to improve the stage of decanting/sedimentation, particularly with regard to its dimensioning, the probability of this parameter will also meet, it would be high, thus being able to reuse the treated waste water for Street Washes and Ecosystem Support. For the remaining parameters analyzed, values below the Emission Limit Value (VLE) were recorded, and, overall, better results were obtained for the HRT of ± 2 days.
The use of microalgae in wastewater treatment has drawn increased interest among the international scientific community as a promising technology, constituting a more sustainable alternative to conventional treatment systems, which remain major energy consumers. The present work is integrated within the objectives of the research project "GreenTreat", where 9 GreenDune photobioreactors (PBR) were installed in the ETAR of Quinta do Lago. These photobioreactors, with a capacity of 450 L each and with a field deployment area of about 1 m2, were installed in 3 lines, which work in parallel, each one composed of 3 sequential units. The aim was to optimize the removal of the main nutrients N, P and ammonia (NH4+), as well as the microbiological parameters Escherichia coli (E. coli) and Intestinal Enterococci, using the configuration of the hydraulic retention time (HRT) operating parameter, taking advantage of the disinfectant effect of microalgae to improve the quality of the final effluent, complying with the discharge conditions and enabling its reuse. Accordingly, the local effluent conditions were monitored in terms of pH and temperature (ºC), as well as the physical-chemical and microbiological characteristics of the effluent treated by the process proposed. Finally, the possible scenarios of reuse were studied, in accordance with the current legislation. Results confirmed that the systems that use microalgae have high efficiency in nutrient removal, especially NH4+ (between 60% and 90%), and they have a high disinfection potential. Indeed, during the photosynthesis process, microalgae consume large amounts of CO2, leading to increased pH and making it impossible for pathogenic organisms to survive, due to the hostile environment created. On the other hand, this specific system proved to be inefficient in the removal of total suspended solids (TSS), because the decanting/sedimentation stage was not properly sized, preventing solids/biomass in suspension (characteristic of processes that use microalgae) to decant/sediment in the best conditions, making impossible its reuse, for any of the possible uses. However, since for urban use, only the value of TSS does not comply with the provisions of the legislation, it can be assumed that, if it were possible to improve the stage of decanting/sedimentation, particularly with regard to its dimensioning, the probability of this parameter will also meet, it would be high, thus being able to reuse the treated waste water for Street Washes and Ecosystem Support. For the remaining parameters analyzed, values below the Emission Limit Value (VLE) were recorded, and, overall, better results were obtained for the HRT of ± 2 days.
Description
Keywords
Tratamento de águas residuais Microalgas Tratamento terciário Reutilização