Artigos de Revista

Flow monitoring in wastewater systems is used for system operation or for billing purposes, among others. Given the difficult measurement conditions, gaps in measurement series occur frequently and stakeholders need an appropriate method to estimate missing data. In data scarcity situations, mathematical modelling of the underlying physical processes may not be feasible and other methods are required. Partial least squares (PLS) regression is a multivariate statistical method suited to correlated data and has been frequently used for water quality estimates. PLS suitability for hourly and daily flow estimations was tested, based on previous flow and precipitation data, which urban water utilities currently monitor. Results were evaluated using proposed performance criteria and classes. The estimation errors were comparable to the ones obtained in physical process modelling. The application of the proposed method for flow estimation in sewers, in two common scenarios of wet and dry weather flows, is presented and discussed.

O fósforo é um recurso não renovável, fundamental para a produção agrícola e, portanto, estratégico para a Europa. O paradoxo do fósforo resulta da antecipação de dificuldades futuras na satisfação da procura mundial deste elemento, a par do crescente aumento da frequência e intensificação da eutrofização de massas de água, fruto da dispersão excessiva de nutrientes nos ecossistemas terrestres e aquáticos. Importa assim promover uma gestão sustentável do fósforo, designadamente aumentando a eficiência da sua utilização na agricultura e valorizando o que existe em materiais orgânicos. Neste artigo discute-se o papel do fósforo na redução das pressões sobre o nexus água-energia-alimentos num contexto de economia circular, e o potencial associado à sua recuperação a partir de águas residuais urbanas. Propõe-se uma estratégia de tratamento e descrevem-se várias opções tecnológicas que promovem a acumulação-libertação-recuperação de fósforo e apresenta-se um conjunto de indicadores chave para avaliação do desempenho das instalações na recuperação deste elemento. Os indicadores consideram a reutilização de água, valorização de lamas e/ou produção de estruvite, e a descarga de fósforo no meio recetor, e são parte de um sistema de apoio à operação e gestão patrimonial destas infraestruturas.

Serviceability limit states (related to deformation) rather than ultimate limit states (related to collapse)are often the reason for the need to assess existing timber structures. Prediction of timber members

Monitoring and evaluation of glued laminated timber structures in service is essential to warrant its integrity, where non-destructive techniques play an important role. This paper describes the results obtained on glued laminated timber beams of maritime pine, with and without preservative treatment, and of spruce, exposed to naturaloutdoor environment as well as to artificial weathering. The assessment of glue lines

Surface consolidation is a common practice in the conservation of the built heritage. However, the effectiveness of consolidation of calcareous materials is often doubtful, due to the lack of effective and compatible consolidation products. Dispersions of calcium hydroxide nanoparticles in alcohol, the so-called nanolimes, can recover the superficial consolidation of calcareous substrates. Nevertheless, they are often not able to guarantee an in-depth consolidation. Previous research by the authors has demonstrated that the effectiveness of nanolime can be improved by fine-tuning the properties and the application protocol of the dispersions, based on the moisture transport properties of the material to be treated. In this paper, we verify the consolidation effectiveness and physical compatibility of the developed nanolimes, when applied on coarse porous calcareous materials like Maastricht limestone and lime-based mortars. The results show that a suitable mass consolidation can be achieved with nanolimes, while maintaining a good compatibility with the substrate material.

A evolução das propriedades das geomembranas foi estudada com base em ensaios realizadossobre amostras expostas às condições climáticas, com e sem geotêxtil de cobertura, durante aproximadamente 12 anos, em diferentes locais de Portugal. Neste artigo, analisam-se a influência da exposição sobre diferentes geomembranas de PEAD, a influência da radiação ultravioleta sobre geomembranas expostas em locais com distintos índices de UV e a influência do geotêxtil de proteção às geomembranas. As propriedades em análise foram a massa volúmica, o índice de fluidez, a resistência à tração e a extensão na cedência e na rotura, o teor em negro de carbono e o tempo de indução à oxidação. Verificou-se que a exposição às condições climáticas afetou a massa volúmica e o tempo de indução à oxidação. Verificou-se, também, que o aumento do índice ultravioleta influenciou os resultados da resistência à tração e extensão na cedência e do tempo de indução à oxidação. Por fim, constatou-se que os resultados foram semelhantes para as geomembranas expostas com esem geotêxtil de cobertura

Desanding facilities are located between the water intake and the penstock of medium and high-headhydroelectric power plants to avoid the entrance of suspended sediments into the penstock and therefore toreduce hydro-abrasion at turbine parts. This paper focusses on the selection and description of measurementinstrumentation to characterize flow and sediment flux at desanding facilities with high spatial and temporalresolution. The selection criteria for the instrumentation are highlighted and the capabilities and limitations ofthe devices and techniques are described. The modular design of mounting system carrying the instrumentation allows for measurement under several structural constraints. The chosen concept for data acquisition in terms of measurement grid, measurement duration and sampling frequency provides high resolution data of flow quantities and sediment flux. For reliable quantification of sediment fluxes, in-line measurements of turbidity are correlated with suspended sediment concentration obtained by water sampling, also considering density and temperature. Selected findings from the field measurement campaign at two sites in Switzerland are presented and discussed. The employed experimental setup proved to be appropriate and reliable to characterize the flow field and sediment fluxes in desanding facilities at high resolutions.

The limitation of the progression of internal erosion in zoned dams, potentially caused by an upstream zone built of coarse, well-graded soils with non-plastic fines, is assessed using a new test cell. This device allows two types of tests to be conducted: the flow-limiting erosion test (FLET) and the crack-filling erosion test (CFET), which are designed to study the isolated influence of the flow-limiting action and the crack-filling action, respectively. The specimen is subjected to water flow along a hole drilled in the core and the upstream zone. In the CFET, the specimen additionally includes a downstream filter. Three upstream materials with non-plastic fines, a core and a filter are examined. The results of nine FLETs and nine CFETs are presented and analysed. The FLETs show the clear influence of the compaction water content, fines content and gravel content of the upstream soils in their capability to provide the flow-limiting action. The CFETs show that the specimen using the coarsest upstream soil (with 21% non-plastic fines) compacted on the dry side is capable of stopping the progression of erosion, enabling a partial crack-filling action. In all other test conditions, the filtering mechanism due to erosion of the upstream soil provides an important limitation of the erosion process. Based on the tests, practical recommendations to assess the influence of upstream zones on the limitation of internal erosion are proposed.

Geothermal energy production consists of two main types: low temperature or low enthalpy for temperatures below 150ºC, andhigh temperature or high enthalpy systems for temperatures over than 150ºC. In mainland Portugal the most common groundtemperature varies from 20 to 40ºC, depending on the place where the geothermal boreholes are placed, which means that lowenthalpy systems can be considered. Currently the increased development of ground source heat pumps (GSHP) lead to acontinuous development and innovation of ground heat exchangers (GHE). The geothermal systems can contribute with savingsbetween 25-75% of the energy demands of buildings

This paper presents work carried out with the aim of characterizing the mechanical behavior and developing visual and machine strength grading systems for Portuguese maritime pine roundwood for structural applications. Two samples of forty maritime pine logs each were collected, one in a northern region of Portugal and another in an interior central region. After drying, the logs were visually graded andsubjected to nondestructive tests, using vibration and ultrasounds, for determination of dynamic modulus of elasticity. The logs were then subjected to destructive tests for determining bending and compression strength and bending modulus of elasticity. These results were analyzed in order to identify the features to be considered in the strength grading process. From this analysis, a proposal was developed tovisually grade Portuguese maritime pine roundwood in two strength grades. According to the European strength class standard for solid timber, the upper grade has similar mechanical properties to the C50 class, whereas the lower grade is similar to the C35. The machine grading showed good potential as a result of the good correlation presented between the dynamic modulus of elasticity and the mechanical properties. However, the ultrasounds showed slightly better correlation than the vibration method, whereas the last one is more practical.