Avaliação do desempenho de coagulantes recuperados de lodo de ETA por extração via alcalina-ácida
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Data
2020-02-21
Autores
Vilela, Ruan Larisson Toninatto
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Universidade Estadual Paulista (Unesp)
Resumo
No processo de tratamento de água visando sua potabilidade é gerado um resíduo (lodo) cujo manejo e disposição são problemas de caráter urgente, principalmente, devido à escassez de soluções eficazes. Um desafio extra a esses problemas é que esse lodo pode possuir em sua composição uma concentração acentuada de alumínio (elemento com efeitos nocivos aos organismos e ao meio ambiente) devido ao coagulante utilizado no processo de tratamento. Recuperar e reutilizar os componentes coagulantes do lodo pode ser uma alternativa para a sua destinação. Assim, com esse propósito, será possível economizar no custo de dosagem com a reciclagem do produto obtido, além de possibilitar a diminuição do volume final do lodo devido à remoção de água durante o processo. O método consistiu na recuperação, via alcalina-ácida, do coagulante do lodo (desaguado) de duas ETAs distintas. Inicialmente, os lodos foram submetidos a extração em pH 12, com hidróxido de sódio (NaOH – 20%) e, posteriormente, extração em pH 2, testando o ácido sulfúrico (H2SO4 – 20%) e o ácido clorídrico (HCl – 20%). A proporção utilizada foi 1:10 (m:v). A reutilização dos coagulantes recuperados foi realizada em Jar Test utilizando água bruta de um dos pontos de captação do município de Presidente Prudente – SP. O efeito coagulante foi validado fazendo comparativo com o coagulante comercial PAC, por meio dos parâmetros turbidez (NTU) e cor (PCU), além da análise frente aos valores máximos permitidos (VMP) pelo Ministério da Saúde para os mesmos parâmetros. Os resultados mostraram que três dos quatro coagulantes obtidos, se destacaram por apresentarem eficiências de remoção de cor e turbidez de águas brutas, superiores a 99%, com muitos valores próximos ou iguais aos obtidos pelo PAC, além de estarem dentro dos VMP. Com esse trabalho, levando em consideração os parâmetros analisados, foi possível concluir que o método de recuperação possui potencial de ser uma destinação parcial do lodo, uma vez que no processo, além do coagulante recuperado, uma parcela sólida remanescente do lodo necessita de destinação adequada. Mais estudos são necessários para avaliar a viabilidade, econômica e técnica, desse método, levando em consideração os fatores que influenciam na qualidade do produto final obtido, e os diversos outros parâmetros que o validem.
In water treatment process, aiming at its potability, a residue (sludge) is generated, which management and disposal are urgent problems, mainly due to the lack of effective solutions. An extra challenge to these problems is that the sludge may have a high aluminum concentration in its composition (an element with harmful effects to organisms and the environment) due to the coagulant used in the treatment process. Recovering and reusing coagulant components of the sludge can be an alternative for its destination, since for this purpose it is possible to save the dosage cost by recycling the obtained product, in addition to reducing the final sludge volume due to the water removal during the process. The method consisted of recovering, through an alkaline-acid, coagulant from two different WTPs sludge. Initially, the sludge was subjected to extraction at pH 12, with sodium hydroxide (NaOH - 20%) and, later, extraction at pH 2, testing sulfuric acid (H2SO4 - 20%) and hydrochloric acid (HCl - 20%). The proportion used was 1:10 (m: v). The reuse of the recovered coagulants was carried out in Jar Test using raw water from one of the collection points in the city of Presidente Prudente - SP. The coagulant effect was validated by comparing it with the commercial coagulant PAC, using the parameters turbidity (NTU) and color (PCU), besides to the analysis compared with the maximum allowed values (MAV) by the Ministry of Health for the same parameters. The results showed that three of the four coagulants obtained, stood out for presenting efficiencies in removing color and turbidity from raw water, greater than 99%, with many values close to or equal to those obtained by the PAC, in addition to being lower than the MAV. With this work, taking into account the analyzed parameters, it was possible to conclude that the recovering method has the potential to be a partial sludge destination, since in the process, in addition to the recovered coagulant, a remaining solid needs an adequate destination. Further studies are needed to assess the viability, economical and technical, of this method, taking into account the factors that influence the quality of the final product obtained, and the various parameters that validate it.
In water treatment process, aiming at its potability, a residue (sludge) is generated, which management and disposal are urgent problems, mainly due to the lack of effective solutions. An extra challenge to these problems is that the sludge may have a high aluminum concentration in its composition (an element with harmful effects to organisms and the environment) due to the coagulant used in the treatment process. Recovering and reusing coagulant components of the sludge can be an alternative for its destination, since for this purpose it is possible to save the dosage cost by recycling the obtained product, in addition to reducing the final sludge volume due to the water removal during the process. The method consisted of recovering, through an alkaline-acid, coagulant from two different WTPs sludge. Initially, the sludge was subjected to extraction at pH 12, with sodium hydroxide (NaOH - 20%) and, later, extraction at pH 2, testing sulfuric acid (H2SO4 - 20%) and hydrochloric acid (HCl - 20%). The proportion used was 1:10 (m: v). The reuse of the recovered coagulants was carried out in Jar Test using raw water from one of the collection points in the city of Presidente Prudente - SP. The coagulant effect was validated by comparing it with the commercial coagulant PAC, using the parameters turbidity (NTU) and color (PCU), besides to the analysis compared with the maximum allowed values (MAV) by the Ministry of Health for the same parameters. The results showed that three of the four coagulants obtained, stood out for presenting efficiencies in removing color and turbidity from raw water, greater than 99%, with many values close to or equal to those obtained by the PAC, in addition to being lower than the MAV. With this work, taking into account the analyzed parameters, it was possible to conclude that the recovering method has the potential to be a partial sludge destination, since in the process, in addition to the recovered coagulant, a remaining solid needs an adequate destination. Further studies are needed to assess the viability, economical and technical, of this method, taking into account the factors that influence the quality of the final product obtained, and the various parameters that validate it.
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Palavras-chave
Reciclagem, Toxicidade, Alumínio, Destinação, Reutilização, Recycling, Toxicity, Aluminum, Destination, Reuse