Browsing by Author "Lucas, Helena"
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- Avaliação económica preliminar da nanofiltração na remoção de cianotoxinas em águas naturaisPublication . Silva, Lucila; Lucas, Helena; Ribau Teixeira, MargaridaCom este trabalho pretende-se quantificar os custos associados à implementação e exploração de um sistema de nanofiltração (NF) na Estação de Tratamento de Águas (ETA) de Alcantarilha da Águas do Algarve, S.A. com uma capacidade de operação de 259.000 m3/d e efectuar uma comparação com os custos do actual sistema de tratamento implementado. A quantificação dos custos actuais foi efectuada através de dados obtidos a partir das operações desenvolvidas na ETA de Alcantarilha, fornecidos pelas Águas do Algarve, S.A. relativos a 2008 e 2009. Os custos foram estimados para as diferentes etapas de tratamento. Os resultados revelaram um custo associado ao tratamento de água para consumo humano de cerca de 0,10 €/m3.ano, para o esquema de tratamento existente na ETA de Alcantarilha. Realizaram-se ensaios experimentais à escala laboratorial e piloto onde se avaliou e optimizou o sistema de NF na remoção de matéria orgânica natural e cianotoxinas para diferentes taxas de recuperação de água (TxR), com águas que abastecem a actual ETA de Alcantarilha. A partir dos resultados obtidos com o estudo à escala piloto, verificou-se que a NF tem capacidade de produzir água de elevada qualidade com concentrações de microcistina muito inferiores ao valor legislado (1 mg/L), e baixo teor em matéria orgânica natural e de anatoxina- a, e que esta deve operar a TxR de pelo menos 75%. Com base nos resultados experimentais e através de modelos já desenvolvidos a partir de dados obtidos em trabalhos anteriormente realizados, determinaram-se os custos associados ao sistema de NF. O custo total estimado de implementação e operação/manutenção foi de 0,21 €/m3.ano para o ano de 2025. Conclui-se que apesar da implementação da NF na ETA de Alcantarilha provoque um acréscimo do custo de tratamento face ao tratamento convencional, este poderá ser justificável face à qualidade da água obtida.
- Monitoring of hazardous substances at Alcantarilha’s WTP, PortugalPublication . Rosa, Maria João; Cecilio, T.; Ribau Teixeira, Margarida; Viriato, M.; Coelho, R.; Lucas, HelenaA monitoring programme of hazardous substances was implemented in Alcantarilha’s water treatment plant (Algarve, Portugal) since 2002, in addition to the legally established monitoring of standard physical, chemical and microbiological parameters. The objective of this programme was to ensure the drinking water quality regarding the waterborne disease organisms Cryptosporidium, Giardia, Salmonella, Pseudomonas aeruginosa, enterovirus and cyanobacteria, and the potentially harmful chemicals aluminium, cyanotoxins, and disinfection by-products (THM) and their precursors (TOC, DOC, UV254nm, SUVA). Most of these parameters are new and still not regulated by the Portuguese and the European legislation. Data presented in this study refer to the period of August 2002 to October 2003. Results show that, despite the seasonal variations of the raw water quality, concentrations of the hazardous substances in the supplied drinking water were far below the legal standards and the WHO’s and EPA guideline values, demonstrating the high removal efficiencies of this treatment plant.
- Nanofiltration performance to remove microcystins from water for human consumption at a pilot scalePublication . Serrão Sousa, Vânia; Lucas, Helena; Ribau Teixeira, MargaridaThe presence of microcystins (MC) in drinking water reservoirs, even at low concentrations, is a problem for all involved in management and water treatment. This cyclic peptide hepatotoxin, produced by several species of toxic cyanobacteria as secondary metabolites, cause liver damage and is considered tumor promoter (Matsushima et al., 1992), representing a potential hazard to human health (Carmichael, 1994). Therefore, it is necessary to ensure their removal in water treatment plants (WTP) by innovative and effective treatments. In recent years, nanofiltration (NF) has become an attractive alternative technology to conventional water treatment due to the capacity to remove inorganic and organic compounds (disinfection by-products (DBP) precursors) with low molecular weight cut-offs and low operating pressures (Her et al., 2000; Costa and Pinho, 2006). However, the application of NF to drinking water treatment is affected by natural organic matter (NOM) fouling (Hong and Elimelech, 1997). Membrane fouling refers to plugging and external pore blocking (Gwon et al., 2003) which causes low performance and reduction of membrane time life, because of flux decline and/or transmembrane pressure increase (Her et al., 2000). In addition, good results were obtained with NF to remove cyanotoxins present in water for human consumption. According to some authors (Ribau Teixeira and Rosa, 2005; Gijsbertsen- Abrahamse et al., 2006; Ribau Teixeira and Rosa, 2006), NF removed cyanobacterial toxins from water, with removal rates greater than 99% at laboratory scale. However, pilot scale experiments in real context are missing. The aim of this work is to study NF performance to remove microcystins from natural water, at a pilot scale in a real context of WTP.
- OPTEXPLOR – new application for water resources management for private water supply utilitiesPublication . Nunes, L.; Monteiro, José Paulo; Stigter, T. Y.; Ribau Teixeira, Margarida; Nascimento, João; Ribeiro, L.; Lucas, HelenaThis article presents the steps made for the development of a new water management system (WMS) for a private water utility in the south of Portugal, and its main results. The WMS is composed of a set of models representing the water resources, surface and groundwater, water quality models, economic models, and water allocation optimization models. The system was developed at the request of the regional water utility (Águas do Algarve, S.A.), which is responsible for distributing water to the entire Algarve region (most touristic area in Portugal, with about ten million tourists per year, and a local population of about four hundred thousand). Results clearly show that independently of the amount of water available, inter-annual exploration is always the best solution, if possible. When water scarcity is high, as in consecutive dry years, the water utility will need to call municipalities to use their systems to complement supply. The level of supply deficit is higher, in any case, for annual exploration management, and so are exploration costs. These results clearly show that water resources management needs careful inter-annual planning, even for a private water supply utility with very limited control over water exploration by other competing users.
- Previsão da capacidade de remoção de cianobactérias e cianotoxinas na ETA de AlcantarilhaPublication . Campinas, Margarida Páscoa; Ribau Teixeira, Margarida; Lucas, Helena; Rosa, Maria JoãoOs blooms de cianobactérias em reservatórios de água destinada à produção de água para consumo humano originam muitos problemas, sendo o mais preocupante o facto de uma proporção significativa de cianobactérias produzirem uma ou mais toxinas. Num programa de prevenção da saúde pública, relativamente ao consumo de água com cianotoxinas, é essencial avaliar a eficiência de remoção destes compostos nas Estações de Tratamento de Água (ETA). Neste âmbito, o presente trabalho tem como objectivo efectuar uma previsão, com base em informação bibliográfica, da eficiência de remoção de cianobactérias e cianotoxinas pelo processo de tratamento instalado na ETA de Alcantarilha (Águas do Algarve, S.A.), face a um eventual bloom na água de origem. Prevê-se que a ETA de Alcantarilha (tratamento convencional com pré-ozonização) possibilite a remoção de cianobactérias e cianotoxinas intracelulares se forem utilizadas as doses de reagentes e residuais de ozono e cloro apropriados e com a utilização de carvão activado em pó (PAC) em doses relativamente elevadas. A principal incerteza prende-se com o desempenho da ETA na remoção de toxinas solúveis, uma vez que este está dependente da qualidade da água na origem e das condições de funcionamento da ozonização, da adsorção com PAC e da cloragem.
- A rapid small scale evaluation of ultrafiltration performance for surface water treatment at Alcantarilha’s WTW (Algarve, Portugal)Publication . Ribau Teixeira, Margarida; Lucas, Helena; Rosa, Maria JoãoA rapid small scale evaluation of ultrafiltration (UF) performance with and without physicalchemical pre-treatment was performed to up-grade the conventional treatment used for drinking water production in Alcantarilha’s WTW, Algarve, Portugal. Direct UF and pre-ozonation/ coagulation/ flocculation/ sedimentation/ UF (O/C/F/S/UF) were evaluated using polysulphone membranes of different apparent molecular weight cut-off (MWCO) (15-47 kDa). The results indicated that (i) UF is an effective barrier against microorganisms, including virus larger than 80 nm; (ii) for surface waters with low to moderate SUVA values, direct UF performance is equivalent or better than the conventional treatment in terms of residual turbidity, while UV254nm and TOC residuals require the use of O/C/F/S/UF; (iii) the permeate quality improves with the membrane apparent MWCO decrease, especially for the direct UF, although the conventional treatment performance is never reached using UF; (iv) membrane fouling and adsorption phenomena are more severe in direct UF than in O/C/F/S/UF sequence (preozonation decreases the membrane foulants by decreasing their hydrophobicity) and these phenomena increase with the membrane hydraulic permeability and, particularly, with the membrane apparent MWCO.
- Remoção de matéria orgânica por ultrafiltração. Caso de estudo: ETA de AlcantarilhaPublication . Ribau Teixeira, Margarida; Lucas, Helena; Rosa, Maria JoãoEstudou-se a remoção da matéria orgânica (MON) por ultrafiltração (UF), utilizando uma série de membranas comerciais de polissulfona.
- Screening of sustainable groundwater sources for integration into a regional drought-prone water supply systemPublication . Stigter, T. Y.; Monteiro, José Paulo; Nunes, L.; Vieira, João; Cunha, Maria da Conceição; Ribeiro, Luís; Nascimento, João; Lucas, HelenaThis paper reports on the qualitative and quantitative screening of groundwater sources for integration into the public water supply system of the Algarve, Portugal. The results are employed in a decision support system currently under development for an integrated water resources management scheme in the region. Such a scheme is crucial for several reasons, including the extreme seasonal and annual variations in rainfall, the effect of climate change on more frequent and long-lasting droughts, the continuously increasing water demand and the high risk of a single-source water supply policy. The latter was revealed during the severe drought of 2004 and 2005, when surface reservoirs were depleted and the regional water demand could not be met, despite the drilling of emergency wells. For screening and selection, quantitative criteria are based on aquifer properties and well yields, whereas qualitative criteria are defined by water quality indices. These reflect the well’s degree of violation of drinking water standards for different sets of variables, including toxicity parameters, nitrate and chloride, iron and manganese and microbiological parameters. Results indicate the current availability of at least 1100 l s−1 of high quality groundwater (55% of the regional demand), requiring only disinfection (900 l s−1) or basic treatment, prior to human consumption. These groundwater withdrawals are sustainable when compared to mean annual recharge, considering that at least 40% is preserved for ecological demands. A more accurate and comprehensive analysis of sustainability is performed with the help of steady-state and transient groundwater flow simulations, which account for aquifer geometry, boundary conditions, recharge and discharge rates, pumping activity and season. (tibor.stigter@ist.utl.pt) ality. They permit an advanced analysis of present and future scenarios and show that increasing water demands and decreasing rainfall will make the water supply system extremely vulnerable, with a high risk of groundwater salinization and ecosystem degradation.
- The water crisis in southern Portugal: how did we get there and how should we solve itPublication . Nunes, Luís; Monteiro, José Paulo; Cunha, Maria da Conceição; Vieira, João; Lucas, Helena; Ribeiro, LuísUntil very recently, public water supply in the Algarve region was almost entirely supported by groundwater wells. However, in the last years of the XX Century, the Portuguese central administration defined a scheme for the public water supply sector entirely based in surface water from large dams, in order to guarantee the public water supply. The efforts to abandon groundwater as a source for public supply started in 1998, after a large investment in new infrastructures and rehabilitation of other ones. However, the practical implementation of this water supply scheme showed that an integrated resource management is needed in order to implement a more economical and reliable solution. The present paper describes the historical background and the evolution of water use in the last decades until the present time in the Algarve, and a proposal for restructuring the management of the water supplies based in the development of a decision support system in the scope of an integrated water resources management.
- Ultrafiltração directa de águas superficiais turvas na ETA de AlcantarilhaPublication . Ribau Teixeira, Margarida; Lucas, Helena; Rosa, Maria JoãoEfectuou-se a ultrafiltração (UF), à escala laboratorial, de águas bruta e decantada da ETA de Alcantarilha para avaliar se, para águas turvas, o ajuste de pH pode substituir o pré-tratamento convencional (pré-ozonização/clarificação) à UF, na produção de água para consumo humano. A água bruta (30-40NTU, UV254nm (indicador de substâncias húmicas) 0.30–0.32cm-1 e COT 2.78–8.02mgC/l) foi permeada a diferentes valores de pH: 4.13, 7.60 (pH natural da água) e 8.33. A água decantada (2.9–5.1NTU, UV254nm 0.03–0.05cm-1 e COT < 3.5mgC/l) foi permeada a 7.48 (pH natural da água). Os resultados mostram que o ajuste de pH aumenta o desempenho da UF directa de águas turvas: os fluxos da UF directa, particularmente a pH básico, aproximam-se dos fluxos de água decantada e a turvação residual da água é equivalente à da UF com pré-tratamento convencional. Relativamente à MON, por acção da pré-ozonização, a presente na água decantada tem um peso molecular inferior e é mais hidrofílica. Assim, a UF directa produz uma água com maior concentração em substâncias húmicas (apesar das rejeições serem maiores), enquanto que em termos de COT a qualidade da água ultrafiltrada a pH ácido é semelhante à produzida por UF de água decantada. Em conclusão, o ajuste de pH parece viabilizar a UF directa de águas superficiais turvas. O efeito do pH é justificado por alteração da carga e tamanho da MON e das interacção membrana – matéria colmatante.