Adequação da vinhaça de cana-de-açúcar para reuso agrícola: avaliação de diferentes tecnologias de tratamento e potenciais impactos ambientais
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Data
2016-07-22
Autores
Rodrigues, Isabella Junqueira [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Os processos de coagulação-floculação surgem como uma alternativa para o pós-tratamento de efluentes de reatores anaeróbios, normalmente caracterizados pela presença de matéria orgânica e cor residual. O presente trabalho buscou ajustar os melhores parâmetros de coagulação, mistura rápida, floculação e sedimentação para vinhaça anaerobicamente tratada e, dessa forma, verificar se o efluente final admite reuso, com ênfase na aplicação agrícola. Os coagulantes testados foram: solução de amido 2% (m/v) e cloreto férrico 40% sendo que as faixas das dosagens de coagulante testadas foram, respectivamente, 1 a 120 mg.L-1 e 1 a 25 g.L-1. Para as condições testadas, os resultados obtidos mostraram a ineficiência da solução de amido como coagulante para esse efluente. Para os ensaios realizados utilizando-se cloreto férrico como coagulante, os parâmetros otimizados foram: dosagem de solução de cloreto férrico 40% (1,6 g.L-1), gradiente e tempo de mistura rápida (325 rpm; 10 s), gradiente e tempo de floculação (65 rpm; 20min) e tempo de sedimentação (20 min). Dentre os parâmetros, apenas a dosagem de coagulante e o tempo de sedimentação influenciaram significativamente (α=5%) o desempenho do processo. A correção do pH do afluente não se mostrou satisfatória para o desempenho do tratamento. Os resultados indicaram que os processos de coagulação/floculação são mais eficazes quando aplicados à vinhaça metanizada em comparação às vinhaças acidificada e bruta. A partir dos resultados obtidos foi realizada analisada a possibilidade de reuso do efluente tratado na ferti-irrigação, constatando-se que maiores volumes de vinhaça tratada podem ser aplicados ao solo, quando comparados à vinhaça bruta.
Coagulation-flocculation processes emerge as an alternative to the post-treatment of effluent streams from anaerobic reactors, usually characterized by residual organic matter and color. This study aimed to adjust the best coagulation, rapid mixing, flocculation and sedimentation parameters applied to anaerobically treated vinasse and thus check whether the final effluent allows reuse, with emphasis on agricultural application. Solutions of starch 2% (m/v) and ferric chloride 40% were tested as coagulants, with dosages ranging from 1 to 120 mg.L-1 and 1 to 25 g.L-1, respectively. For the conditions tested, the results indicated the ineffectiveness of the starch solution as a coagulant for this effluent. For the tests performed with ferric chloride as coagulant, the optimal parameters were: ferric chloride solution dosage 40% (1.6 g.L-1), rapid mixing gradient and time (325 rpm, 10 s), flocculation gradient and time (65 rpm; 20 min) and settling time (20 min). Among the parameters, only coagulant dosage and settling time significantly (α=5%) impacted the performance of the process. The correction of the influent pH was not satisfactory for the performance of treatment. The results indicated that the coagulation/flocculation processes are most effective when applied to methanized compared to acidified and raw vinasses. From the results obtained, analyses were performed to verify the possibility of reuse of treated effluent in fertigation, observing that higher volumes of treated vinasse can be applied to the soil, as compared to raw vinasse.
Coagulation-flocculation processes emerge as an alternative to the post-treatment of effluent streams from anaerobic reactors, usually characterized by residual organic matter and color. This study aimed to adjust the best coagulation, rapid mixing, flocculation and sedimentation parameters applied to anaerobically treated vinasse and thus check whether the final effluent allows reuse, with emphasis on agricultural application. Solutions of starch 2% (m/v) and ferric chloride 40% were tested as coagulants, with dosages ranging from 1 to 120 mg.L-1 and 1 to 25 g.L-1, respectively. For the conditions tested, the results indicated the ineffectiveness of the starch solution as a coagulant for this effluent. For the tests performed with ferric chloride as coagulant, the optimal parameters were: ferric chloride solution dosage 40% (1.6 g.L-1), rapid mixing gradient and time (325 rpm, 10 s), flocculation gradient and time (65 rpm; 20 min) and settling time (20 min). Among the parameters, only coagulant dosage and settling time significantly (α=5%) impacted the performance of the process. The correction of the influent pH was not satisfactory for the performance of treatment. The results indicated that the coagulation/flocculation processes are most effective when applied to methanized compared to acidified and raw vinasses. From the results obtained, analyses were performed to verify the possibility of reuse of treated effluent in fertigation, observing that higher volumes of treated vinasse can be applied to the soil, as compared to raw vinasse.
Descrição
Palavras-chave
Digestão anaeróbia, Coagulação-floculação, Reuso, Anaerobic digestion, Coagulation-flocculation, Reuse