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Abstract(s)
A modelação matemática de Estações de Tratamento de Águas Residuais (ETAR) tem sido uma ferramenta de enorme utilidade nas fases de projeto e de exploração destas estruturas de tratamento.
O presente estudo teve por objetivo principal construir um modelo matemático da ETAR de Bragança, em particular do seu tratamento biológico de lamas ativadas, com vista a avaliar, compreender e otimizar o seu desempenho. A construção do modelo foi efetuada com recurso ao ambiente de simulação WRc STOAT 5.0. O processo de lamas ativadas foi descrito pelo modelo de referência ASAL3.
O modelo construído foi calibrado e validado com base em dados experimentais de 2015, obtidos no âmbito do programa de controlo analítico da ETAR. O modelo foi ainda utilizado para avaliar a qualidade do efluente em resposta a alterações do caudal e composição do afluente, a alterações de condições operacionais e a outras alternativas de tratamento.
O modelo mostrou-se bastante adequado na descrição da evolução mensal da qualidade do efluente final da ETAR relativamente aos parâmetros Sólidos Suspensos Totais (SST) e Carência Bioquímica de Oxigénio (CBO5), embora apresente uma tendência para os subestimar em 1,5 e 3,5 mg/L, respetivamente. Em relação ao azoto total, os valores simulados aproximaram-se dos valores reais, quando se aumentaram as taxas de recirculação interna para 400%, um fator de cerca de 4 vezes superior.
Os resultados do modelo e dos cenários mostram e reforçam o bom desempenho e a operação otimizada da ETAR em relação a remoção de SST e CBO5. Em relação ao azoto total, a ETAR não assegura de forma sistemática uma eficiência elevada, mas apresenta um bom desempenho, face ao que o modelo consegue explicar para as mesmas condições operacionais.
Através do estudo de cenários procurou-se encontrar alternativas de tratamento eficientes e viáveis de remoção de azoto total, mas não se identificaram soluções que assegurassem decargas de azoto abaixo dos limites legais. Os melhores resultados que se alcançaram para a remoção deste contaminante estão associados ao aumento das taxas de recirculação interna do sistema pré-anóxico existente e a uma configuração do tipo Bardenpho de quatro estágios com alimentação distribuída, em proporções iguais, pelos dois estágios anóxicos. Outras soluções que envolvam tecnologias distintas podem e devem ser equacionadas em projetos futuros que visem a melhoria de eficiência de remoção de azoto da ETAR.
Modeling and simulation of wastewater treatment plants (WWTP) has been a useful tool to improve design quality and operating efficiency of these treatment facilities. This study aimed at building a mathematical model of the principal Bragança WWTP, especially focusing on its activated sludge biological process, to evaluate, understand and optimize its performance. The model was created on the WRc STOAT 5.0 simulation environment. The activated sludge process was described by the reference model ASAL3. The model was calibrated and validated based on the 2015 experimental data obtained under the framework of the analytical control program of the WWTP. The model was still used to evaluate the quality of the effluent in response to affluent flowrate and composition changes, operational condition modifications and other treatment alternatives. The model seemed to be fairly appropriate in describing the monthly evolution of the final effluent of the WWTP for the Total Suspended Solids (TSS) and Biochemical Oxygen Demand (BOD5) parameters, exhibiting however a tendency for underestimating TSS and BOD5 concentrations in 1,5 and 3,5 mg/L, respectively. Regarding the Total Nitrogen, simulated values approached the real values only when the internal recirculation rate was increased to 400%, a factor about four times higher than the mean operacional internal recirculation. Simulated values showed and reinforced the good performance and operation of the WWTP concerning the removal of TSS and BOD5. In relation to Total Nitrogen, the WWTP does not sistematically ensure high efficiency, but it shows a good performance when compared with the model description, under the same operacional conditions. Modeling scenarios were studied in order to find effective and viable treatment alternatives to improve Total Nitrogen removal, but any studied solution was able to produce a final effluent with nitrogen levels below the legal limits. The best results were linked not only to the increasing of internal recirculation rates of the existing pre-anoxic system, but also to a four stages Bardenpho configuration type with the feed equally distributed through the two anoxic stages. Others solutions involving new technologies should be envisaged on future projects, in order to increase the nitrogen removal efficiency of the WWTP.
Modeling and simulation of wastewater treatment plants (WWTP) has been a useful tool to improve design quality and operating efficiency of these treatment facilities. This study aimed at building a mathematical model of the principal Bragança WWTP, especially focusing on its activated sludge biological process, to evaluate, understand and optimize its performance. The model was created on the WRc STOAT 5.0 simulation environment. The activated sludge process was described by the reference model ASAL3. The model was calibrated and validated based on the 2015 experimental data obtained under the framework of the analytical control program of the WWTP. The model was still used to evaluate the quality of the effluent in response to affluent flowrate and composition changes, operational condition modifications and other treatment alternatives. The model seemed to be fairly appropriate in describing the monthly evolution of the final effluent of the WWTP for the Total Suspended Solids (TSS) and Biochemical Oxygen Demand (BOD5) parameters, exhibiting however a tendency for underestimating TSS and BOD5 concentrations in 1,5 and 3,5 mg/L, respectively. Regarding the Total Nitrogen, simulated values approached the real values only when the internal recirculation rate was increased to 400%, a factor about four times higher than the mean operacional internal recirculation. Simulated values showed and reinforced the good performance and operation of the WWTP concerning the removal of TSS and BOD5. In relation to Total Nitrogen, the WWTP does not sistematically ensure high efficiency, but it shows a good performance when compared with the model description, under the same operacional conditions. Modeling scenarios were studied in order to find effective and viable treatment alternatives to improve Total Nitrogen removal, but any studied solution was able to produce a final effluent with nitrogen levels below the legal limits. The best results were linked not only to the increasing of internal recirculation rates of the existing pre-anoxic system, but also to a four stages Bardenpho configuration type with the feed equally distributed through the two anoxic stages. Others solutions involving new technologies should be envisaged on future projects, in order to increase the nitrogen removal efficiency of the WWTP.
Description
Mestrado de dupla diplomação com a UTFPR - Universidade Tecnológica Federal do Paraná
Keywords
Águas residuais urbanas Lamas ativadas Modelação matemática Modelo ASAL3