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Controlo dinâmico da dosagem da Coagulação/ Floculação no tratamento físico-químico da ETAR da Guia
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A presente dissertação analisou e avaliou o funcionamento do tratamento primário avançado
da ETAR da Guia, mais concretamente da coagulação química, durante a época balnear. Neste
sentido, o objetivo foi a otimização da coagulação química, alterando a potência dos agitado-
res da câmara de mistura rápida, com o propósito de reduzir da dosagem de coagulante o
cumprimento da Licença de Utilização de Recursos Hídricos (LURH).
Foi efetuada uma validação das condições de operação em
Jar Test, com dosagens de coagu-
lante de 200 ppm e 0,7 ppm de floculante, tendo-se garantindo uma eficiência de remoção de
turvação semelhante.
Foram realizados vários ensaios em escala laboratorial em que foi estudado a alteração do
gradiente de velocidade (G) da câmara de mistura rápida. O valor de G foi alterado entre 500
-1000 s-1. Considerou-se que a melhor opção será aumentar o G de 339 s-1 para 500 s-1, o que
permitiu reduzir a dosagem para 170 ppm. Esta opção apresenta também o menor custo total
anual, de 169 620€, resultando numa redução de cerca de 14,86% no consumo de coagulante,
e consequentemente no custo de operação,
OPEX.
Com o objetivo de prever o valor esperado de Sólidos Suspensos Totais (SST), permitindo to-
mar decisões operacionais, foram desenvolvidas duas retas de regressão múltipla com um R2
de 0,80 e 0,81, relacionando, na primeira o valor de turvação e transmitância e, na segunda
adicionou-se a eficiência de remoção.
Conclui-se com esta dissertação, que a otimização do tratamento do físico-químico é bastante
benéfica para a ETAR da Guia, uma vez que alterando o G é possível reduzir custos operacionais.
This dissertation analysed and evaluated the operation of the advanced primary treatment at the Guia WWTP, specifically chemical coagulation, during the bathing season. The aim was to optimise chemical coagulation by changing the power of the agitators in the rapid mixing chamber, with the aim of reducing the coagulant dosage and complying with the Water Re- sources Use Licence (LURH). The operating conditions were validated in a Jar Test with dosages of 200 ppm coagulant and 0,7 ppm flocculant, ensuring similar turbidity removal efficiency. Several laboratory-scale tests were carried out in which the change in the velocity gradient (G) of the rapid mixing chamber was studied. The value of G was changed between 500 -1000 s-1. It was considered that the best option would be to increase the G from 339 s-1 to 500 s-1, which allowed the dosage to be reduced to 170 ppm. This option also has the lowest total annual cost of 169 620€, resulting in a reduction of around 14,86% in coagulant consumption, and consequently in the operating cost, OPEX. In order to predict the expected value of Total Suspended Solids (TSS), allowing operational decisions to be made, two multiple regression lines were developed with an R2 of 0,80 and 0,81, relating the turbidity and transmittance value in the first and the removal efficiency in the second. The conclusion of this dissertation is that optimising the physico-chemical treatment is very beneficial for the Guia WWTP, since by changing G it is possible to reduce operating costs.
This dissertation analysed and evaluated the operation of the advanced primary treatment at the Guia WWTP, specifically chemical coagulation, during the bathing season. The aim was to optimise chemical coagulation by changing the power of the agitators in the rapid mixing chamber, with the aim of reducing the coagulant dosage and complying with the Water Re- sources Use Licence (LURH). The operating conditions were validated in a Jar Test with dosages of 200 ppm coagulant and 0,7 ppm flocculant, ensuring similar turbidity removal efficiency. Several laboratory-scale tests were carried out in which the change in the velocity gradient (G) of the rapid mixing chamber was studied. The value of G was changed between 500 -1000 s-1. It was considered that the best option would be to increase the G from 339 s-1 to 500 s-1, which allowed the dosage to be reduced to 170 ppm. This option also has the lowest total annual cost of 169 620€, resulting in a reduction of around 14,86% in coagulant consumption, and consequently in the operating cost, OPEX. In order to predict the expected value of Total Suspended Solids (TSS), allowing operational decisions to be made, two multiple regression lines were developed with an R2 of 0,80 and 0,81, relating the turbidity and transmittance value in the first and the removal efficiency in the second. The conclusion of this dissertation is that optimising the physico-chemical treatment is very beneficial for the Guia WWTP, since by changing G it is possible to reduce operating costs.
Descrição
Palavras-chave
Época Balnear Tratamento Primário Avançado Doseamento de Reagentes Coagulação Sólidos Suspensos Totais Gradiente de velocidade