Potencial de aplicação de coagulantes orgânicos no controle da eutrofização de águas de reservatórios do semiárido brasileiro

• Ano de defesa: 2024
• Autor(a) principal: Sousa, Maria Emília de Freitas
• Orientador(a): Ferreira, Weruska Brasileiro
• Banca de defesa: Ferreira, Weruska Brasileiro , Vieira, Fernando Fernandes , Lima, Vera Lúcia Antunes De
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso embargado
• Idioma: por
• Instituição de defesa: Universidade Estadual da Paraíba
• Programa de Pós-Graduação: Programa de Pós-Graduação em Ciência e Tecnologia Ambiental - PPGCTA
• Departamento: Pró-Reitoria de Pós-Graduação e Pesquisa - PRPGP
• País: BR
• Palavras-chave em Português: Coagulantes orgânicos; Taninos; Anadenanthera colubrina; Mimosa tenuiflora; Anacardium occidentale
• Área do conhecimento CNPq: ENGENHARIAS
• Link de acesso: https://repositorio.uepb.edu.br/handle/123456789/72401

Eutrophication is a process caused by excess nutrients, such as phosphorus and nitrogen, in bodies of water, leading to the uncontrolled proliferation of algae and cyanobacteria. This phenomenon is aggravated in semi-arid regions, where irregular rainfall and the accumulation of nutrients intensify the process, resulting in the degradation of water quality and affecting human supply. As an alternative for treating water from eutrophicated reservoirs and aiming to replace the use of conventional inorganic coagulants, such as aluminum salts, the study proposed the production of three coagulants based on tannins extracted from three plant species present in the Brazilian semi-arid region, the angico-vermelho, jurema-preta and cashew trees. Vegetable tannins are phenolic compounds that, in addition to being biodegradable, do not release metals into treated water, presenting themselves as a solution for water treatment. Thus, the study included the delimitation of the study area and collection of water samples for treatment, followed by the production of coagulants, using tree barks, subjected to drying, grinding, quantification of tannin levels using the stiasny method, optimization of extraction and cationization concentrations, by the Mannich reaction. The application of coagulants occurred in two stages: (i) comparison between the coagulants produced and aluminum sulfate applied to a water sample from a reservoir used for public supply, and (ii) phosphorus removal tests and phytotoxicity assessment of the coagulants produced applied to samples from the three reservoirs studied. The results indicate that tannin-based coagulants were effective in removing phosphorus, with prominent removals varying between 41-96% in applications between 300, 500 and 700 mg.L-1. Furthermore, phytotoxicity tests, carried out with lettuce seeds (Lactuca sativa), led to the conclusion that at lower doses the coagulants did not cause adverse effects, however at higher doses, such as 700 mg.L-1, may have phytotoxic effects, especially with angico-vermelho coagulant. Therefore, this study reinforces the viability of natural coagulants in controlling eutrophication, providing an efficient and ecologically correct alternative for treating water from eutrophicated reservoirs and improving water quality in the semi-arid region of Brazil.