Análise de viabilidade da utilização de lodo de ETA coagulado com cloreto de polialumínio (PAC) composto com areia como agregado miúdo em concreto para recomposição de calçadas: estudo de caso na ETA do município de Mirassol-SP
Data
2017-11-15
Autores
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Biblioteca Digital de Teses e Dissertações da USP
Universidade de São Paulo
Escola de Engenharia de São Carlos
Universidade de São Paulo
Escola de Engenharia de São Carlos
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O presente trabalho foi elaborado com o intuito de equacionar dois problemas: redução do impacto ambiental do lançamento do lodo da ETA Mirassol in naturanos córregos e a redução de custos através da redução na quantidade de lodo enviada para o aterro sanitário e da redução no volume do agregado miúdo o qual, apesar de não representar o maior custo entre os materiais necessários para a confecção do concreto, representa uma redução de custos para a empresa concessionária que precisa recompor diariamente as calçadas que são quebradas para a execução de seus serviços de manutenção nos sistemas de água e esgoto. Devido ao fato de a ETA Mirassol ainda não dispor de um plano de gerenciamento dos resíduos de seu tratamento, como metodologia de secagem das amostras de lodo, optou-se pela simulação de lagoa de lodo fora de escala em que o lodo ficou exposto ao sol durante períodos diferentes de 15 e 30 dias. A primeira amostra, mais seca, foi utilizada nos ensaios de lixiviação e solubilização e a segunda nos ensaios envolvendo o concreto. Foram realizados ensaios de lixiviação e solubilização com o objetivo de classificar o lodo de acordo com a ABNT NBR 10.004/2004 os quais, resultaram em excesso nos teores de cádmio, chumbo e, principalmente, de manganês, cerca de 400 vezes maior que o permitido. Por conta disto, o lodo pôde ser classificado como um resíduo classe II A, ou seja, não perigoso e não inerte. Vale destacar que apesar de coagulado com policloreto de alumínio, o lodo não apresentou teores deste metal que superassem os limites da norma. Voltando a atenção para o concreto de calçada, verificou-se que não existem normas ou padrões que determinem a maneira adequada de executá-Io. Desta forma, optou-se por simular a confecção do concreto realizada no dia-a-dia pelos pedreiros, compreendendo o traço 1:2:3 (cimento:areia:brita) em massa e com o acompanhamento visual da sua trabalhabilidade. A análise de viabilidade da utilização do lodo como agregado foi realizada com base nos ensaios de compressão axial e compressão diametral, também conhecido como ensaio brasileiro (tração). Estes ensaios demonstraram que para os traços que utilizam 5%, 10% e 20% de lodo, foram obtidas resistências à compressão axial superiores à meta de 15 MPa o que foi considerado bastante satisfatório uma vez que são recomendados para calçadas valores de 10 MPa. Já para os ensaios de tração, não há referências, mas pôde-se constatar que a utilização do lodo como composto com areia como agregado miúdo interfere sensivelmente nos resultados, sendo recomendada a utilização de porcentagens próximas a 10%. Portanto, concluiu-se que a utilização do lodo da ETA Mirassol em concretos para recomposição de calçadas é viável nas porcentagens até 10%.
This work was done wishing to solve two problems: the reduction of the environmental impact caused by the inappropriate sludge disposal in Mirassol and also the reduction in the costs by reducing the volume of sludge destined to landfill and by reducing the volume of concrete small aggregates which, in spite of not representing the biggest cost of all materials involved, actually represents a cost reduction to the concessionary which needs to remake daily the pavement broke to the execution of maintenance and operation works in the water and wastewater systems. Considering the fact that Mirassol\'s water treatment plant does not have a sludge management plan, it was chosen the sun exposal method with two different times (15 and 30 days) to dry the samples of sludge. The first sample, the driest, was used in the lixiviation and solubilization experiments and the second one in the experiments involving the concrete. The objective of lixiviation and solubilization experiments was to classify the sludge according to ABNT NBR 10.004/2004. This experiments resulted manganese, plumbean and cadmium excess, especially the manganese with 400 times more concentration than the permitted by the law. So, according to these results, Mirassol\'s water treatment plant sludge was classified as Class II A. That\'s important to observe that, despite the fact that in Mirassol they use the CPA, the sludge did not shown high concentrations of aluminum. Keeping the attention on the concrete to pavements, it was noticed that doesn\'t exist in Brazil any law to discipline its confection and because of that, it was chosen the empirical method, used by the workers daily with 1:2:3 in mass. The viability analysis of the sludge use as aggregate to concrete pavement was based on the compression and traction experiments which demonstrated that, considering traces with 5%, 10% and 20% of sludge incorporated, the results was satisfactory. In fact, all of the samples had results above the aim for compression (15 MPa). On the other hand, considering the traction experiments, there\'s no references in Brazil for pavements, but it was possible to observe that the sludge addiction affected more this characteristic than the compression. However, the traction results were also satisfactory. Finally, this work recommends the utilization of 10% of sludge incorporated in concrete to pavements because they had the best results considering the compression and traction experiments.
This work was done wishing to solve two problems: the reduction of the environmental impact caused by the inappropriate sludge disposal in Mirassol and also the reduction in the costs by reducing the volume of sludge destined to landfill and by reducing the volume of concrete small aggregates which, in spite of not representing the biggest cost of all materials involved, actually represents a cost reduction to the concessionary which needs to remake daily the pavement broke to the execution of maintenance and operation works in the water and wastewater systems. Considering the fact that Mirassol\'s water treatment plant does not have a sludge management plan, it was chosen the sun exposal method with two different times (15 and 30 days) to dry the samples of sludge. The first sample, the driest, was used in the lixiviation and solubilization experiments and the second one in the experiments involving the concrete. The objective of lixiviation and solubilization experiments was to classify the sludge according to ABNT NBR 10.004/2004. This experiments resulted manganese, plumbean and cadmium excess, especially the manganese with 400 times more concentration than the permitted by the law. So, according to these results, Mirassol\'s water treatment plant sludge was classified as Class II A. That\'s important to observe that, despite the fact that in Mirassol they use the CPA, the sludge did not shown high concentrations of aluminum. Keeping the attention on the concrete to pavements, it was noticed that doesn\'t exist in Brazil any law to discipline its confection and because of that, it was chosen the empirical method, used by the workers daily with 1:2:3 in mass. The viability analysis of the sludge use as aggregate to concrete pavement was based on the compression and traction experiments which demonstrated that, considering traces with 5%, 10% and 20% of sludge incorporated, the results was satisfactory. In fact, all of the samples had results above the aim for compression (15 MPa). On the other hand, considering the traction experiments, there\'s no references in Brazil for pavements, but it was possible to observe that the sludge addiction affected more this characteristic than the compression. However, the traction results were also satisfactory. Finally, this work recommends the utilization of 10% of sludge incorporated in concrete to pavements because they had the best results considering the compression and traction experiments.
Palavras-chave
Agregado miúdo, Calçadas, Concreto, Lodo de ETA, Concrete, Pavements, Small aggregates, Water treatment plant sludge