Tratamento de efluentes da indústria de concentrados de sumos de fruta: aplicação de processos biológicos e químicos
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2013-11-05
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As indústrias agro-alimentares caracterizam-se por produzirem elevadas quantidades de águas residuais nos seus processos de transformação. Os efluentes de concentrados de fruta, exemplo de águas residuais provenientes destas indústrias, encontram-se muito contaminados por matéria orgânica e sólidos em suspensão.
O presente trabalho teve como objectivo geral analisar a problemática ambiental associada aos efluentes agro-alimentares. Em particular, investigou-se a tratabilidade das águas residuais de uma indústria de concentrados de fruta por aplicação de uma combinação de processos: tratamento biológico aeróbio (1ª parte) seguido de coagulação/floculação química (2ª parte).
No processo biológico, utilizaram-se reactores descontínuos aos quais se adicionaram diferentes dosagens de lamas biológicas para tratar o efluente em estudo avaliando-se o efeito de diferentes tempos de arejamento. Neste processo procurou verificar-se a actuação das lamas activadas na redução da carga poluente do efluente.
No processo de coagulação/floculação química, utilizou-se um sistema Jar-Test, para avaliar o efeito de distintos agentes coagulantes/floculantes: Ca(OH)2, Al2(SO4)3, FeSO4, FeCl3. Para cada agente coagulante estudou-se o efeito do pH do meio e procurou optimizar-se a dosagem do coagulante para o melhor pH obtido.
A eficiência de cada um dos processos anteriores foi acompanhada pela determinação de diferentes parâmetros como CQO, turvação, sólidos suspensos, polifenóis totais, pH e TOC.
Os ensaios de biodegradabilidade realizados permitiram a decomposição de grande parte da matéria orgânica e redução do teor em sólidos suspensos por parte dos microrganismos presentes nas lamas, verificando-se que para maiores tempos de arejamento maior era a redução dos parâmetros estudados. Os ensaios de coagulação/floculação química permitiram identificar, entre os quatro coagulantes, o cloreto férrico como o melhor compromisso para a redução dos parâmetros estudados, utilizando uma dosagem de 0,44 g/L por 250 mL de efluente a pH=5,5.
No final do tratamento biológico, observou-se uma redução de CQO na ordem dos 96%, da turvação de 40%, do teor em polifenóis totais de 94 % e de 82% dos sólidos em suspensão. Após a aplicação do agente coagulante/floculante cloreto férrico, na segunda fase, verifica-se uma redução global de CQO de 99,6%, da turvação de 94,4%, polifenóis totais de 97,3% e sólidos em suspensão de 98,1%.
Os resultados obtidos no presente trabalho mostram que a conjugação de um processo biológico aeróbio seguido de um processo de coagulação/floculação química, envolvendo cloreto férrico, é eficaz na redução dos principais parâmetros característicos dos efluentes agro-industriais colocando-os em conformidade com os valores limites de emissão para descarga em águas superficiais.
The agro-alimentary industries are characterized by producing great amounts of wastewater in their transformation processes. Concentrated fruit effluents are an example of residual water proceeding from these industries, highly contaminated by organic matter and suspended solids. The present work aimed to analyze the environmental problematic associated to these effluents. In particular, the treatability of wastewater from concentrated fruit industry was investigated by applying a combination of processes: aerobic biological treatment (first part) followed by chemical coagulation/flocculation (second part). In biological processes, batch reactors had been used which was added different dosages of activated sludge to wastewater to treat wastewater in study. The effect of different aeration times was evaluated. In this process was studied the performance of activated sludge to reduce the pollutant load of effluent. In chemical coagulation/flocculation process, was used a Jar-Test system to assess the effect of different coagulants/flocculants: Ca(OH)2, Al2(SO4)3, FeSO4, FeCl3. For each coagulant agent studied the effect of pH of the medium and tried to optimize the dosage of coagulant for the best pH obtained. The efficiency of each one of previous processes was followed by the determination of different parameters as COD, turbidity, suspended solids, total polyphenols, pH and TOC. The biodegradability tests allowed a great decomposition of organic matter and suspended solids by microorganisms present in sludge, verifying for longer periods of aeration greater reduction of the parameters studied. Chemical coagulation/flocculation experiments had allowed to identify, between four coagulants, ferric chloride as the best compromise to reduce the parameters studied, using a dosage of 0.44 g/L in 250 mL of effluent to pH = 5.5. At the end of biological treatment, was observed a reduction of COD in the order of 96%, 40% of turbidity, 94% to total polyphenols and 82% of suspended solids. After application of coagulant/flocculant agent ferric chloride in the second phase, there is an overall reduction in COD of 99.6%, 94.4% to turbidity, 97.3% to total polyphenol and 98.1% to solids. The results obtained in present work show that the combination of an aerobic biological process followed by a process of chemical coagulation/flocculation, involving ferric chloride, is effective in reducing of main parameters characteristics of the agro-industrial effluents by placing them in accordance with the emission limit values for discharge to surface in superficial waters.
The agro-alimentary industries are characterized by producing great amounts of wastewater in their transformation processes. Concentrated fruit effluents are an example of residual water proceeding from these industries, highly contaminated by organic matter and suspended solids. The present work aimed to analyze the environmental problematic associated to these effluents. In particular, the treatability of wastewater from concentrated fruit industry was investigated by applying a combination of processes: aerobic biological treatment (first part) followed by chemical coagulation/flocculation (second part). In biological processes, batch reactors had been used which was added different dosages of activated sludge to wastewater to treat wastewater in study. The effect of different aeration times was evaluated. In this process was studied the performance of activated sludge to reduce the pollutant load of effluent. In chemical coagulation/flocculation process, was used a Jar-Test system to assess the effect of different coagulants/flocculants: Ca(OH)2, Al2(SO4)3, FeSO4, FeCl3. For each coagulant agent studied the effect of pH of the medium and tried to optimize the dosage of coagulant for the best pH obtained. The efficiency of each one of previous processes was followed by the determination of different parameters as COD, turbidity, suspended solids, total polyphenols, pH and TOC. The biodegradability tests allowed a great decomposition of organic matter and suspended solids by microorganisms present in sludge, verifying for longer periods of aeration greater reduction of the parameters studied. Chemical coagulation/flocculation experiments had allowed to identify, between four coagulants, ferric chloride as the best compromise to reduce the parameters studied, using a dosage of 0.44 g/L in 250 mL of effluent to pH = 5.5. At the end of biological treatment, was observed a reduction of COD in the order of 96%, 40% of turbidity, 94% to total polyphenols and 82% of suspended solids. After application of coagulant/flocculant agent ferric chloride in the second phase, there is an overall reduction in COD of 99.6%, 94.4% to turbidity, 97.3% to total polyphenol and 98.1% to solids. The results obtained in present work show that the combination of an aerobic biological process followed by a process of chemical coagulation/flocculation, involving ferric chloride, is effective in reducing of main parameters characteristics of the agro-industrial effluents by placing them in accordance with the emission limit values for discharge to surface in superficial waters.
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Dissertação de Mestrado em Engenharia do Ambiente
Palavras-chave
Tratamento de efluentes , Biodegradabilidade aeróbia , Efluentes agro-industriais , Concentrados de fruta , Coagulação/floculação química , CQO , Arejamento , Cloreto férrico