Uso da semente de moringa oleifera como coagulante no tratamento terciário de efluente sanitário
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Data
2021-01-29
Autores
Andrade, Priscila Vega
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A inclusão de um tratamento terciário pode se fazer necessária para prover um efluente de qualidade suficiente para lançamento ou para o reuso. Não foram encontrados na literatura estudos do uso da semente de Moringa oleifera (MO) como coagulante em tratamento terciário de efluente sanitário. Portanto, o objetivo do presente estudo é avaliar o uso do extrato aquoso da semente de MO como coagulante natural no tratamento terciário de um efluente sanitário em comparação com o sulfato de alumínio (SA) através das operações unitárias de coagulação, floculação, sedimentação e filtração. Para tanto, amostras de efluente secundário foram coletadas e ensaios de jar test com filtro de areia acoplado foram realizados com dosagens de MO (150 a 750 mg/L) e de SA (40 a 200 mg/L) para determinação da dosagem ideal em função da remoção de turbidez e de cor aparente. Com as dosagens ótimas de MO (600 mg/L) e SA (200 mg/L), novos ensaios de jar test com filtro de areia acoplado foram realizados para comparar: lodo gerado, pH, alcalinidade, remoções de cor aparente, turbidez, SST, nutrientes, DBO, DQO, COT, carga bacteriana (coliformes totais e Escherichia coli), atividade antibacteriana in vitro (Escherichia coli cepa ATCC 25922) e citotoxicidade (células Vero). Os resultados demonstraram que o aumento da dosagem de MO refletiu no aumento do potencial zeta, tendendo a sua neutralidade. Quanto menor o valor de pH do efluente, maior a remoção de cor aparente e turbidez, em função do potencial zeta das partículas. Nas dosagens ideais, MO e SA apresentaram resultados similares, com remoções acima de 99%, 66% e 92% para carga bacteriana, cor aparente e turbidez, respectivamente. O uso de MO não afetou alcalinidade ou pH, e resultou em um efluente com menor citotoxicidade quando comparado com o uso do SA. No entanto, a MO não removeu nutrientes e aumentou o COT, DBO e DQO. Além disso, tanto MO quanto SA não apresentaram significativa atividade antibacteriana, o que pode estar relacionado à faixa de dosagem avaliada de MO. O tratamento com a MO gerou um lodo 3 vezes menos volumoso que o SA, com concentração de sólidos totais 1,8 vezes menor e com composição predominantemente orgânica. Portanto, o extrato aquoso da semente de MO tem potencial de usado como coagulante no tratamento terciário de efluente sanitário. Porém, é recomendada a obtenção da proteína purificada de MO quando é exigido a redução da carga orgânica do efluente.
Inclusion of tertiary treatment may be necessary for providing effluent of sufficient quality for disposal or reuse. Studies of Moringa oleifera (MO) as a coagulant in tertiary wastewater treatment have not been found in the literature. Thus, the aim of the present study is to evaluate the use of aqueous extraction of MO seeds as a natural coagulant in the tertiary treatment of a sanitary effluent, in comparison to alum, through unit operations of coagulation, flocculation, sedimentation, and filtration. Therefore, samples of secondary effluent were collected and jar test assays with sand filter were performed with MO dosages (150 - 750 mg/L) and alum dosages (40 - 200 mg/L) to determine the optimal dosage as a function of turbidity and apparent color removal. With the ideal dosages of MO (600 mg/L) and alum (200 mg/L), new jar test assays with sand filter were performed to compare: the generated sludge, pH, alkalinity, apparent color, turbidity, TSS, nutrients, BOD, COD, TOC, bacterial load (total coliform and Echerichia coli), in vitro antibacterial activity (Escherichia coli strain ATCC 25922), and cytotoxicity (Vero cells). The results showed that the increase in the dosage of MO reflected in the increase of the zeta potential, tending to its neutrality. The lower the effluent pH value, the greater the apparent color and turbidity removal as a function of the zeta potential of the particles. MO and alum at the ideal dosages showed similar results with removals higher than 99%, 66%, and 92% for bacterial load, apparent color, and turbidity, respectively. The use of MO did not affect alkalinity or the pH and provided an effluent less cytotoxic when compared to the use of alum. However, MO did not remove nutrients, and increased TOC, BOD, and COD. In addition, both MO and alum did not show significant antibacterial activity, which may be related to the MO dosage range applied. The treatment with MO generated 3 times less bulky sludge than alum, with total solids concentration 1.8 times lower and predominantly organic composition. Therefore, the aqueous extraction of the MO seed has the potential to be used as a coagulant in the tertiary treatment of domestic wastewater. However, a purification of the extraction of the MO seed is recommended when reduction of the organic load of the effluent is required.
Inclusion of tertiary treatment may be necessary for providing effluent of sufficient quality for disposal or reuse. Studies of Moringa oleifera (MO) as a coagulant in tertiary wastewater treatment have not been found in the literature. Thus, the aim of the present study is to evaluate the use of aqueous extraction of MO seeds as a natural coagulant in the tertiary treatment of a sanitary effluent, in comparison to alum, through unit operations of coagulation, flocculation, sedimentation, and filtration. Therefore, samples of secondary effluent were collected and jar test assays with sand filter were performed with MO dosages (150 - 750 mg/L) and alum dosages (40 - 200 mg/L) to determine the optimal dosage as a function of turbidity and apparent color removal. With the ideal dosages of MO (600 mg/L) and alum (200 mg/L), new jar test assays with sand filter were performed to compare: the generated sludge, pH, alkalinity, apparent color, turbidity, TSS, nutrients, BOD, COD, TOC, bacterial load (total coliform and Echerichia coli), in vitro antibacterial activity (Escherichia coli strain ATCC 25922), and cytotoxicity (Vero cells). The results showed that the increase in the dosage of MO reflected in the increase of the zeta potential, tending to its neutrality. The lower the effluent pH value, the greater the apparent color and turbidity removal as a function of the zeta potential of the particles. MO and alum at the ideal dosages showed similar results with removals higher than 99%, 66%, and 92% for bacterial load, apparent color, and turbidity, respectively. The use of MO did not affect alkalinity or the pH and provided an effluent less cytotoxic when compared to the use of alum. However, MO did not remove nutrients, and increased TOC, BOD, and COD. In addition, both MO and alum did not show significant antibacterial activity, which may be related to the MO dosage range applied. The treatment with MO generated 3 times less bulky sludge than alum, with total solids concentration 1.8 times lower and predominantly organic composition. Therefore, the aqueous extraction of the MO seed has the potential to be used as a coagulant in the tertiary treatment of domestic wastewater. However, a purification of the extraction of the MO seed is recommended when reduction of the organic load of the effluent is required.
Descrição
Palavras-chave
Moringa oleifera, Coagulação, Tratamento terciário, Potencial zeta, Atividade antibacteriana, Coagulation, Tertiary treatment, Zeta potential, Antibacterial activity