Tratamento combinado de efluente têxtil utilizando coagulante à base de tanino seguido por degradação por reator fotocatalítico

Abstract

The textile industry stands out as a major consumer of water for its production, generating a high volume of effluents. Among the effluent treatment stages we highlight coagulation / flocculation, which uses compounds called coagulants during its process. Aluminum sulphate is an inorganic coagulant widely used for the treatment of effluents, due to its low cost and high availability, however, its use presents negative points such as the presence of aluminum residues in the treated effluent and in the generated sludge, making it difficult Reuse or disposal. On the other hand, the possibility of using organic coagulants, such as tannin, has been increasing due to its biodegradability and the generation of sludge with properties that allow its reuse as a compound or to generate energy. The objective of this study was to evaluate the applicability, efficiency and economic viability of the use of organic coagulant tannin in the treatment of a textile effluent from an industry located in the municipality of Dois Vizinhos-PR, when compared to aluminum sulfate Such as photocatalysis as an advanced treatment process. The physical-chemical characterization of the effluent was carried out and different concentrations of both coagulants were tested in order to compare the removal efficiency and the suitability of the parameters: chemical oxygen demand, color and turbidity. In addition, economic analyzes and quantification and characterization of the sludge generated were carried out. The toxicity and mutagenicity analysis of the effluent (crude, treated with tannin, aluminum sulphate and treated by the industry) and the sludge generated in the laboratory tests using the bioindicators Artemia salina L. and Allium cepa L. were analyzed. The efficiency of the advanced treatment process with photocatalytic reactor was tested by testing the crude effluent, treated with tannin and aluminum sulphate. The optimum concentrations for tannin and aluminum sulphate of 400mg / L and 100mg / L, respectively, were stipulated, and both coagulants adapted the effluent to the current legislation, in relation to the parameters analyzed. The treatment with aluminum sulphate generated a smaller volume of sludge, but it presented aluminum content five times higher when compared to the sludge generated by the treatment with tannin. For the A. salina, the samples of all the effluents showed 100% toxicity, while the crude effluent also showed 50% toxicity, and in the highest concentration the effluent treated with tannin had the lowest toxicity. Using the A. strain, the effluent samples did not alter the mitotic index of the root cells, in contrast the sludge generated from the treatments with aluminum sulphate and tannin reduced the mitotic index during the 24 hours of treatment. The photocatalytic treatment process was effective only at the removal of the true color, using only the effluent without pretreatment. In general, there should be greater incentive regarding the use of tannin considering its physico-chemical and toxicological properties.