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Aplicação de reator eletroquímico para remoção de compostos ativos farmacêuticos de efluente de ETAR: influência da variabilidade da matriz
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Ao longo dos anos, os recursos hídricos têm sido cada vez mais sobre explorados em todo o mundo, o que tem conduzido a um stress hídrico. Uma das soluções que tem vindo a ser adotada é o uso da água residual tratada. A agricultura é dos setores que necessita de um maior volume de água disponível, e é o setor que mais beneficiaria do uso desta água, uma vez que esta é uma fonte de nutrientes que aumentaria as funções do ecossistema solo. Em contrapartida, a água residual tratada pode possuir riscos químicos e microbiológicos, uma vez que as tecnologias utilizadas nas estações de tratamento de águas residuais (ETAR) não removem completamente os contaminantes emergentes, como os produtos farmacêuticos e de cuidado pessoal (PFCP).
Várias tecnologias têm vindo a ser desenvolvidas para remover os PFCP, entre estas destaca-se o processo eletroquímico. A presente dissertação explora a aplicação deste processo num reator eletroquímico, por forma a estudar a degradação de dez compostos orgânicos emergentes: cafeína (CAF), sulfametoxazol (SMX), carbamazepina (CBZ), diclofenac (DCF), oxibenzona (OXY), triclosan (TCS), bisfenol A (BPA), 17β-estradiol (E2), 17α-etinilestradiol (EE2) e ibuprofeno (IBU). Para além disto, também foi avaliada a aplicação deste processo na comunidade microbiológica presente no efluente, através da contagem de unidades formadoras de colónias (CFU) que crescem em meio de agar dextrose de batata, passado um período de 24 horas da sua inoculação. Foram elaborados dois conjuntos de experiências, onde foi aplicada uma intensidade de corrente fixa de 100 mA entre elétrodos de óxido de metal misto. Cada ensaio teve uma duração de 4 horas.
Numa primeira fase, observou-se que os compostos possuem diferentes tempos de meia vida e que estes tempos de remoção podem ser influenciados pela variação dos parâmetros da matriz associados a cada dia de recolha, como é o caso dos sólidos suspensos totais (SST), carência bioquímica de oxigénio (CBO) e azoto amoniacal (N-NH4). Numa segunda fase, verificou-se que os compostos que obtiveram percentagens de degradação mais elevadas foram a SMX, OXY, BPA, E2 e EE2, e as mais baixas foram observadas na CAF, DCF e IBU. As propriedades físico-químicas dos diferentes compostos, incluindo a sua estrutura molecular, foram determinantes para o processo de degradação.
Uma vez que o reator eletroquímico permitiu remover, total ou parcialmente, os PFCP e microrganismos presentes no efluente nas condições testadas, conclui-se que a tecnologia desenvolvida apresenta potencial de aplicação em maior escala, tanto para fins de remediação como de desinfeção.
Over the years, water resources have been increasingly overexploited worldwide, which has led to a water stress. One of the solutions that has been adopted is the use of treated wastewater. Agriculture is one of the sectors that needs a greater volume of available water, and is the sector that would benefit most from the use of treated wastewater, since this is a source of nutrients that would increase soil ecosystem functions. In contrast, the treated wastewater may have chemical and microbiological risks, since the technologies used in wastewater treatment plants (WWTPs) do not completely remove emerging contaminants, such as pharmaceuticals and personal care products (PPCPs). Several technologies have been developed to remove PPCP, among these stands out the electrokinetic process. This dissertation explores the application of this process in an electrochemical reactor, in order to study the degradation of ten emerging organic compounds: caffeine (CAF), sulfamethoxazole (SMX), carbamazepine (CBZ), diclofenac (DCF), oxybenzone (OXY), triclosan (TCS), bisphenol A (BPA),17β-estradiol (E2) and 17α-ethynyl-estradiol (EE2). In addition, it was also evaluated the application of this process in the microbiological community present in the effluent, by counting the colony forming unit (CFU) grown in potato dextrose agar, after a period of 24 hours. Two sets of experiments were developed where a fixed current intensity of 100 mA was applied between mixed metal oxide electrodes. Each test had the duration of 4 hours. In a first phase, it was observed that the compounds have different half-lives and that these removal times can be influenced by the variation of matrix parameters associated with each collection day, such as total suspended solids (SST), biochemical oxygen demand (CBO) and ammonium (N-NH4). In a second phase, it was found that the compounds that had higher degradation percentages were SMX, OXY, BPA, E2 and EE2, and the lowest degradations were observed in CAF, DCF and IBU. The physico-chemical properties of the different compounds, including their molecular structures, were crucial to the degradation process. Since the use of the electrokinetic reactor allowed to remove, totally or partially, the PPCPs and microorganisms present in the effluent in the tested conditions, it is concluded that the developed technology has potential for application on a larger scale, both for remediation and disinfection.
Over the years, water resources have been increasingly overexploited worldwide, which has led to a water stress. One of the solutions that has been adopted is the use of treated wastewater. Agriculture is one of the sectors that needs a greater volume of available water, and is the sector that would benefit most from the use of treated wastewater, since this is a source of nutrients that would increase soil ecosystem functions. In contrast, the treated wastewater may have chemical and microbiological risks, since the technologies used in wastewater treatment plants (WWTPs) do not completely remove emerging contaminants, such as pharmaceuticals and personal care products (PPCPs). Several technologies have been developed to remove PPCP, among these stands out the electrokinetic process. This dissertation explores the application of this process in an electrochemical reactor, in order to study the degradation of ten emerging organic compounds: caffeine (CAF), sulfamethoxazole (SMX), carbamazepine (CBZ), diclofenac (DCF), oxybenzone (OXY), triclosan (TCS), bisphenol A (BPA),17β-estradiol (E2) and 17α-ethynyl-estradiol (EE2). In addition, it was also evaluated the application of this process in the microbiological community present in the effluent, by counting the colony forming unit (CFU) grown in potato dextrose agar, after a period of 24 hours. Two sets of experiments were developed where a fixed current intensity of 100 mA was applied between mixed metal oxide electrodes. Each test had the duration of 4 hours. In a first phase, it was observed that the compounds have different half-lives and that these removal times can be influenced by the variation of matrix parameters associated with each collection day, such as total suspended solids (SST), biochemical oxygen demand (CBO) and ammonium (N-NH4). In a second phase, it was found that the compounds that had higher degradation percentages were SMX, OXY, BPA, E2 and EE2, and the lowest degradations were observed in CAF, DCF and IBU. The physico-chemical properties of the different compounds, including their molecular structures, were crucial to the degradation process. Since the use of the electrokinetic reactor allowed to remove, totally or partially, the PPCPs and microorganisms present in the effluent in the tested conditions, it is concluded that the developed technology has potential for application on a larger scale, both for remediation and disinfection.
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Palavras-chave
PFCP processo eletroquímico microrganismos cultiváveis variabilidade de matriz propriedades físico-químicas estrutura molecular