Separação de microalgas cultivadas em água negra digerida anaerobiamente por meio da coagulação/floculação e sedimentação utilizando a Moringa Oleifera Lam como coagulante natural
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Data
2019-08-12
Autores
Silva, Débora Fernanda Santos da
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Universidade Estadual Paulista (Unesp)
Resumo
As águas residuárias geradas pelo homem são fontes mais acessíveis e sustentáveis para a recuperação de macro e micronutrientes. A recuperação efetiva de nutrientes nas águas residuárias pode ser realizada por microalgas cultivadas em fotobiorreatores. Entretanto, o desafio enfrentado no cultivo de microalgas está direcionado as tecnologias existentes e disponíveis para a separação, que contribuem com elevados custos e baixa eficiência na remoção de microalgas. As etapas de coagulação/floculação seguido pela sedimentação apresentam ser uma alternativa atraente, se aplicados coagulantes naturais, devido à boa eficiência, baixos custos de operação e manutenção, além de garantir uma biomassa com baixa toxicidade. O objetivo da pesquisa foi avaliar a separação de microalgas, cultivadas em água negra digerida anaerobiamente, por meio de ensaios de coagulação/floculação e sedimentação utilizando a Moringa Oleifera Lam como coagulante natural e o teor de macro e micronutrientes presentes na biomassa seca a fim de avaliar sua aplicação como fertilizante orgânico. Foram realizados ensaios, em escala de bancada, sendo avaliado as dosagens do coagulante natural (50 a 550 mg.L-1), em diferentes valores de pH (3, 5, 7 e 9) e tempo de sedimentação (15, 30, 35, 40, 45, 60 e 120 minutos). Após a etapa de separação das microalgas, a biomassa algal foi seca em estufa e analisada a quantidade de macro e micronutrientes. A dosagem ótima de coagulante foi de 475 mg.L-1, o qual promoveu redução de 92% da turbidez e 86%, 92% e 85% da densidade óptica em 540, 682 e 750 nm, 55% de demanda química de oxigênio (DQO), 58% de nitrogênio total, 11% de nitrogênio amoniacal e 53% de fósforo total, em um tempo de sedimentação de 45 minutos. A biomassa de microalgas recuperada apresentou boa concentração de macro e micronutrientes para a aplicação como fertilizante orgânico composto.
Wastewaters generated by mankind are a more affordable and sustainable source for macro and micronutrient recovery. The effective recovery of nutrients in wastewaters can be performed by microalgae grown in photobioreactors. However, the challenge faced in the cultivation of microalgae is directed to existing and available technologies for the separation, which contribute with high costs and low efficiency in the removal of microalgae. The coagulation/flocculation steps followed by sedimentation present an attractive alternative, if natural coagulants are applied, due to the good efficiency, low operation and maintenance costs, in addition to ensuring a biomass with low toxicity. The objective of the research was to evaluate the separation of microalgae, cultivated in anaerobically digested black water, by coagulation/flocculation and sedimentation tests using Moringa Oleifera Lam as a natural coagulant and the content of macro and micronutrients present in dry biomass in order to evaluate its application as an organic fertilizer. The assays were carried out on a bench scale, and the dosages of the natural coagulant (50 to 550 mg.L-1) were evaluated at different pH values (3, 5, 7 and 9) and sedimentation time (15, 30, 35, 40, 45, 60 and 120 minutes). After the microalgae separation stage, the algal biomass was dried in an oven and analyzed the amount of macro and micronutrients. The optimal coagulant dosage was 475 mg.L-1, which promoted a reduction of 92% in turbidity and 86%, 92% and 85% of the optical density at 540, 682 and 750 nm, 55% of chemical oxygen demand (COD), 58% of total nitrogen, 11% of ammoniacal nitrogen and 53% of total phosphorus, in a sedimentation time of 45 minutes. The recovered microalgae biomass presented a good concentration of macro and micronutrients for the application as compound organic fertilizer.
Wastewaters generated by mankind are a more affordable and sustainable source for macro and micronutrient recovery. The effective recovery of nutrients in wastewaters can be performed by microalgae grown in photobioreactors. However, the challenge faced in the cultivation of microalgae is directed to existing and available technologies for the separation, which contribute with high costs and low efficiency in the removal of microalgae. The coagulation/flocculation steps followed by sedimentation present an attractive alternative, if natural coagulants are applied, due to the good efficiency, low operation and maintenance costs, in addition to ensuring a biomass with low toxicity. The objective of the research was to evaluate the separation of microalgae, cultivated in anaerobically digested black water, by coagulation/flocculation and sedimentation tests using Moringa Oleifera Lam as a natural coagulant and the content of macro and micronutrients present in dry biomass in order to evaluate its application as an organic fertilizer. The assays were carried out on a bench scale, and the dosages of the natural coagulant (50 to 550 mg.L-1) were evaluated at different pH values (3, 5, 7 and 9) and sedimentation time (15, 30, 35, 40, 45, 60 and 120 minutes). After the microalgae separation stage, the algal biomass was dried in an oven and analyzed the amount of macro and micronutrients. The optimal coagulant dosage was 475 mg.L-1, which promoted a reduction of 92% in turbidity and 86%, 92% and 85% of the optical density at 540, 682 and 750 nm, 55% of chemical oxygen demand (COD), 58% of total nitrogen, 11% of ammoniacal nitrogen and 53% of total phosphorus, in a sedimentation time of 45 minutes. The recovered microalgae biomass presented a good concentration of macro and micronutrients for the application as compound organic fertilizer.
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Palavras-chave
Microalgas, Nutrientes, Coagulantes naturais, Moringa Oleifera Lam, Fertilizante orgânico, Microalgae, Nutrients, Natural coagulants, Organic fertilizer