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Otimização do funcionamento de um ACTIFLO® em tempo seco na ETAR de Alcântara
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No presente trabalho, estudou-se a utilização de uma linha ACTIFLO em substituição de uma
linha MULTIFLO desativada na ETAR de Alcântara. A instalação ACTIFLO, constitui um órgão da
linha de tratamento primário de tempo húmido (caudais afluentes superiores a 3,3 m3/s). A
instalação MULTIFLO é utilizada na linha de tratamento primário de tempo seco (caudais
afluentes até 3,3 m3/s). O objetivo do estudo efetuado foi a otimização da linha ACTIFLO
relativamente aos parâmetros de funcionamento, por forma a aumentar a eficiência de remoção
de SST do tratamento primário da ETAR, que se encontrava diminuída devido à paragem de uma
linha MULTIFLO.
Para a definição de dosagens de reagentes e concentração de micro-areia na instalação ACTIFLO,
foram realizados ensaios jar test. Nestes ensaios, verificou-se que as doses de reagentes
predefinidas poderiam ser reduzidas sem comprometer a eficiência de tratamento. No entanto,
estes ensaios não permitiram definir uma concentração ótima de micro-areia, tendo-se adotado
os valores teóricos previstos para a operação da instalação (4 a 6 g/L).
Durante a operação da linha ACTIFLO 1 na linha de tempo seco, foram efetuados ensaios
industriais para avaliar a sua eficiência de remoção de SST através de amostras pontuais com
diferentes condições de funcionamento. A monitorização da concentração de micro-areia foi
também efetuada para controlo do processo e avaliação das suas perdas no sistema. Nos
ensaios industriais, foram obtidas eficiências de remoção de SST médias diárias entre 45 e 76%,
verificando-se que as dosagens de reagentes poderiam ser reduzidas para 12 ppm de Fe e 1 ppm
de polímero aniónico sem comprometer a eficiência. Os resultados obtidos revelaram
igualmente que o caudal afluente e a concentração de micro-areia são os parâmetros
determinantes para o desempenho da instalação. Pela monitorização da micro-areia, constatou-
se que as perdas variam em função do caudal afluente à instalação, tendo sido obtidos valores
de perdas de 15 a 35 g/m3, bastante superiores aos valores teóricos de 3 a 5 g/m3.
Visando estudar a velocidade de sedimentação das partículas no decantador da instalação
ACTIFLO, utilizaram-se os resultados das análises efetuadas nos ensaios industriais para uma
sumária calibração do modelo de sedimentação do programa de simulação GPS-X.
Pela avaliação dos efeitos provocados pela introdução da linha ACTIFLO 1 na linha de tempo
seco sobre o tratamento primário da ETAR, concluiu-se que a eficiência de remoção SST não
registou um aumento significativo comparativamente à eficiência obtida com apenas 3 linhas
MULTIFLO devido à instabilidade da sua eficiência para caudais elevados. Verificou-se também
um aumento de custos de exploração considerável, principalmente devido ao aumento do
consumo de reagentes. Os resultados obtidos sugerem que as eficiências obtidas nos ensaios
industriais poderão não ser representativas da realidade devido ao carácter pontual das
amostras recolhidas e à ocorrência de um curto-circuito hidráulico no decantador.
Embora os objetivos não tenham sido totalmente alcançados, o trabalho efetuado permitiu
estudar os parâmetros de funcionamento mais relevantes da instalação ACTIFLO e o impacto da
sua utilização a ter em conta para eventuais trabalhos futuros.
In the present study, the use of an ACTIFLO line replacing a deactivated MULTIFLO line in the Alcântara Wastewater Treatment Plant (WWTP) was investigated. The ACTIFLO constitutes a primary treatment organ of the wet season line (affluent flow rates greater than 3,3 m3/s). The MULTIFLO is used for primary treatment of the dry season line (affluent flow rates up to 3,3 m3/s). The objective of the study was to optimize the ACTIFLO line in terms of its operating parameters in order to increase the Total Suspended Solids (TSS) removal efficiency from the primary treatment of the WWTP, which was reduced due to the stoppage of a MULTIFLO line. For the definition of reagent dosages and micro-sand concentration in the ACTIFLO installation, jar test tests were performed. It was found that the predefined reagent doses could be reduced without compromising the treatment efficiency. However, these tests did not allow to define an optimal micro-sand concentration. For this reason, the theoretical values for the installation operation (4 to 6 g/L) were adopted. During the operation of the ACTIFLO line 1 in the dry weather timeline, industrial tests were carried out to evaluate its TSS removal efficiency with different operating conditions using point samples. The monitoring of the micro-sand concentration was also carried out to control the process and assess its losses in the system. In the performed industrial tests, average daily TSS removal efficiencies between 45 and 76% were obtained, verifying that the reagent dosages could be reduced to 12 ppm Fe and 1 ppm anionic polymer without compromising efficiency. The results indicated as well that the affluent flow rate and micro-sand concentration are the determining parameters for the installation's performance. By monitoring the micro-sand, it was found that the losses vary according to the affluent flow rate to the installation, with loss values of 15 to 35 g/m3 being obtained. These obtained values were much higher than the theoretical values of 3 to 5 g/m3. In order to study the particle settling velocity in the clarifier of the ACTIFLO installation, the results of the analyzes carried out in the industrial tests were used for a summary calibration of the sedimentation model of the GPS-X simulation program. By assessing the effects caused by the introduction of the ACTIFLO line 1 in the dry weather timeline on the primary treatment of the WWTP, it was concluded that the TSS removal efficiency did not register a significant increase compared to the efficiency obtained with only 3 MULTIFLO lines due to the instability of its efficiency for high flow rates. It also resulted in a considerable increase in operating costs, mainly due to the increase in reagent consumption. The results obtained suggest that the efficiencies obtained in industrial tests may not be representative of reality. A reason for this may be the punctual nature of the collected samples and the occurrence of a hydraulic short circuit in the clarifier. Although the main goal has not been achieved, the carried-out work has made possible to study the most relevant operating parameters of the ACTIFLO installation and the impact of its use to be considered for possible future works.
In the present study, the use of an ACTIFLO line replacing a deactivated MULTIFLO line in the Alcântara Wastewater Treatment Plant (WWTP) was investigated. The ACTIFLO constitutes a primary treatment organ of the wet season line (affluent flow rates greater than 3,3 m3/s). The MULTIFLO is used for primary treatment of the dry season line (affluent flow rates up to 3,3 m3/s). The objective of the study was to optimize the ACTIFLO line in terms of its operating parameters in order to increase the Total Suspended Solids (TSS) removal efficiency from the primary treatment of the WWTP, which was reduced due to the stoppage of a MULTIFLO line. For the definition of reagent dosages and micro-sand concentration in the ACTIFLO installation, jar test tests were performed. It was found that the predefined reagent doses could be reduced without compromising the treatment efficiency. However, these tests did not allow to define an optimal micro-sand concentration. For this reason, the theoretical values for the installation operation (4 to 6 g/L) were adopted. During the operation of the ACTIFLO line 1 in the dry weather timeline, industrial tests were carried out to evaluate its TSS removal efficiency with different operating conditions using point samples. The monitoring of the micro-sand concentration was also carried out to control the process and assess its losses in the system. In the performed industrial tests, average daily TSS removal efficiencies between 45 and 76% were obtained, verifying that the reagent dosages could be reduced to 12 ppm Fe and 1 ppm anionic polymer without compromising efficiency. The results indicated as well that the affluent flow rate and micro-sand concentration are the determining parameters for the installation's performance. By monitoring the micro-sand, it was found that the losses vary according to the affluent flow rate to the installation, with loss values of 15 to 35 g/m3 being obtained. These obtained values were much higher than the theoretical values of 3 to 5 g/m3. In order to study the particle settling velocity in the clarifier of the ACTIFLO installation, the results of the analyzes carried out in the industrial tests were used for a summary calibration of the sedimentation model of the GPS-X simulation program. By assessing the effects caused by the introduction of the ACTIFLO line 1 in the dry weather timeline on the primary treatment of the WWTP, it was concluded that the TSS removal efficiency did not register a significant increase compared to the efficiency obtained with only 3 MULTIFLO lines due to the instability of its efficiency for high flow rates. It also resulted in a considerable increase in operating costs, mainly due to the increase in reagent consumption. The results obtained suggest that the efficiencies obtained in industrial tests may not be representative of reality. A reason for this may be the punctual nature of the collected samples and the occurrence of a hydraulic short circuit in the clarifier. Although the main goal has not been achieved, the carried-out work has made possible to study the most relevant operating parameters of the ACTIFLO installation and the impact of its use to be considered for possible future works.
Descrição
Palavras-chave
ACTIFL Tratamento primário de águas residuais Tempo seco Jar test com micro-areia Sedimentação por balastro