Combined hydraulic and biological modelling and full-scale validation of SBR process

The biological reactions during the settling and decant periods of Sequencing Batch Reactors (SBRs) are generally ignored as they are not easily measured or described by modelling approaches. However, important processes are taking place, and in particular when the influent is fed into the bottom of the reactor at the same time (one of the main features of the UniFed process), the inclusion of these stages is crucial for accurate process predictions. Due to the vertical stratification of both liquid and solid components, a one-dimensional hydraulic model is combined with a modified ASM2d biological model to allow the prediction of settling velocity, sludge concentration, soluble components and biological processes during the non-mixed periods of the SBR. The model is calibrated on a full-scale UniFed SBR system with tracer breakthrough tests, depth profiles of particulate and soluble compounds and measurements of the key components during the mixed aerobic period. This model is then validated against results from an independent experimental period with considerably different operating parameters. In both cases, the model is able to accurately predict the stratification and most of the biological reactions occurring in the sludge blanket and the supernatant during the non-mixed periods. Together with a correct description of the mixed aerobic period, a good prediction of the overall SBR performance can be achieved.

Field hydraulic properties of an Alfisol under various fallow systems in southwestern Nigeria

The effects of various fallow management systems and cropping intensities on water infiltration were measured on an Alfisol at Ibadan in southwestern Nigeria. The objective was to determine the influence of the land use systems (a combination of crop-fallow sequences and intercropping types) on soil hydraulic properties obtained by disc permeameter and double-ring infiltration measurements. The experiment was established in 1989 as a split-plot design with four replications. The main plots were natural fallow, planted Pueraria phaseoloides and planted Leucaena leucocephala. The subplots were 1 year of maize/cassava intercrop followed by 3-year fallow (25% cropping intensity), or 2-year fallow (33% cropping intensity), or 1-year fallow (50% cropping intensity), or no fallow period (100% cropping intensity). Water infiltration rates and sorptivities were measured under saturated and unsaturated flow. Irrespective of land use, infiltration rates at the soil surface (121-324 cm h(-1)) were greater than those measured at 30 cm depth (55-144 cm h(-1)). This indicated that fewer large pores were present below 30 cm depth compared with 0-30 cm, depth. Despite some temporal variation, sorptivities with the highest mean value of 93.5 cm h(-1/2) increased as the cropping intensity decreased, suggesting a more continuous macropore system under less intensive land use systems. This was most likely due to continuous biopores created by perennial vegetation under long fallow systems. Intercropped maize and cassava yields also increased as cropping intensity decreased. The weak relationship between crop yields and hydraulic conductivity/infiltration rates suggests that the rates were not limiting.

Hydraulic conductivity in response to exchangeable sodium percentage and solution salt concentration

Hydraulic conductivity is determined in laboratory assays to estimate the flow of water in saturated soils. However, the results of this analysis, when using distilled or deionized water, may not correspond to field conditions in soils with high concentrations of soluble salts. This study therefore set out to determine the hydraulic conductivity in laboratory conditions using solutions of different electrical conductivities in six soils representative of the State of Pernambuco, with the exchangeable sodium percentage adjusted in the range of 5-30%. The results showed an increase in hydraulic conductivity with both decreasing exchangeable sodium percentage and increasing electrical conductivity in the solution. The response to the treatments was more pronounced in soils with higher proportion of more active clays. Determination of hydraulic conductivity in laboratory is routinely performed with deionized or distilled water. However, in salt affected soils, these determinations should be carried out using solutions of electrical conductivity different from 0 dS m-1, with values close to those determined in the saturation extracts.

Computational evaluation of hydraulic system behaviour with entrapped air under rapid pressurization

The pressurization of hydraulic systems containing entrapped air is considered a critical condition for the infrastructure's security due to transient pressure variations often occurred. The objective of the present study is the computational evaluation of trends observed in variation of maximum surge pressure resulting from rapid pressurizations. The comparison of the results with those obtained in previous studies is also undertaken. A brief state of art in this domain is presented. This research work is applied to an experimental system having entrapped air in the top of a vertical pipe section. The evaluation is developed through the elastic model based on the method of characteristics, considering a moving liquid boundary, with the results being compared with those achieved with the rigid liquid column model.

Computational evaluation of hydraulic system behaviour with entrapped air under rapid pressurization

The pressurization of hydraulic systems containing entrapped air is considered a critical condition for the infrastructure's security due to transient pressure variations often occurred. The objective of the present study is the computational evaluation of trends observed in variation of maximum surge pressure resulting from rapid pressurizations. The comparison of the results with those obtained in previous studies is also undertaken. A brief state of art in this domain is presented. This research work is applied to an experimental system having entrapped air in the top of a vertical pipe section. The evaluation is developed through the elastic model based on the method of characteristics, considering a moving liquid boundary, with the results being compared with those achieved with the rigid liquid column model.

Estudo da influência da fragmentação no custo da produção de agregados graníticos

Hoje em dia algumas das principais preocupações que se tem na exploração a céu aberto, são a diminuição de custos e a máxima rentabilidade dos equipamentos. São dois aspectos que estão interligados uma vez que a rentabilização dos equipamentos tem como resultado directo a diminuição dos custos de todas as operações inerentes à exploração a céu aberto e, consequentemente, a diminuição dos custos finais de produção. É por essa lógica de pensamento que se procurou perceber e compreender o funcionamento e a rentabilidade dos equipamentos em função dos diferentes estados de fracturação do maciço rochoso. Este estudo foi realizado numa pedreira a norte de Portugal e complementa outros estudos já realizados, com o objectivo de definir características do diagrama de fogo que assegurem a maior rentabilidade da referida exploração. O estudo baseia-se em determinar os rendimentos da pá carregadora calculando os tempos de ciclo, isto é, o tempo que a pá demorou a carregar, a movimentar e a descarregar o material desmontado dos vários rebentamentos. Calculou-se o rendimento do martelo demolidor na fragmentação de grandes blocos, que não entrariam directamente no britador primário, o qual também foi alvo de estudo, nomeadamente, no que diz respeito aos tempos de encravamento e de britagem, onde se tentou correlacionar esses tempos com os vários desmontes e estimou-se o consumo de energia do britador primário utilizando a equação de Bond. Por fim, realizou-se um estudo comparativo do consumo energético entre as várias fases da exploração a céu aberto. Foram realizados levantamentos geológico-geotécnicos de superfícies de descontinuidades recorrendo à técnica de amostragem linear nas superfícies do maciço rochoso para perceber o tipo de fragmentação e orientação do mesmo.

Fouling of a drinking water system in relation to hydraulic circumstances and customer complaints

In a “perfect” drinking water system, the water quality for the consumers should be the same as the quality of the water leaving the treatment plant. However, some variability along the system can lead to a decrease in water quality (such as discolouration) which is usually reflected in the number of the customer complaints. This change may be related to the amount of sediment in the distribution network, leading to an increase in turbidity at the water supply. Since there is no such thing as a perfect drinking water system, the behaviour of particles in a drinking water network needs a suitable approach in order to understand how it works. Moreover, the combination of measurements, such as turbidity patterns and the Resuspension Potential Method (RPM) aid in the prevention of discoloured water complaints and intervention in the treatment upgrade or the network cleaning. Besides sediments there is also bacterial regrowth in the network, which is related to the water quality and distribution network characteristics. In a theoretical drinking water system higher velocities, temperature and shorter residences times lead to wider bacterial growth. In this study we observe velocity and residence steady-states and bacterial does not seem to be related to either. It can be concluded that adequate measurements of RPM, customer complaints and bacterial concentrations allow a wider knowledge on particle behaviour in drinking water systems.

Conceptual analogy for modelling entrapped air action in hydraulic systems

Hydraulic systems are dynamically susceptible in the presence of entrapped air pockets, leading to amplified transient reactions. In order to model the dynamic action of an entrapped air pocket in a confined system, a heuristic mathematical formulation based on a conceptual analogy to a mechanical spring-damper system is proposed. The formulation is based on the polytropic relationship of an ideal gas and includes an additional term, which encompasses the combined damping effects associated with the thermodynamic deviations from the theoretical transformation, as well as those arising from the transient vorticity developed in both fluid domains (air and water). These effects represent the key factors that account for flow energy dissipation and pressure damping. Model validation was completed via numerical simulation of experimental measurements.

Hydraulic binders

Hydraulic binders play a vital role in the economic and social development because they are essential components of concrete, the most widely used construction material. Nowadays, Portland cement is the most predominantly used hydraulic binder due to its properties and widespread availability. Cement manufacture consumes large amount of non-renewable raw materials and energy, and it is a carbon-intensive process. Many efforts are, therefore, being undertaken towards the developing “greener” hydraulic binders. Concomitantly, binders must also correspond to market demand in terms of performance and aesthetic as well as fulfill mandatory regulations. In order to pursue these goals, different approaches have been followed including the improvement of the cement manufacturing process, production of blended cements, and testing innovative hydraulic binders with a different chemistry. This chapter presents a brief history of hydraulic binder’s discovery and use as well as the environmental and economic context of cement industry. It, then, describes the chemistry and properties of currently most used hydraulic binders—common cements and hydraulic limes—and that of the more promising binders for future applications, namely special Portland cements, aluminous cements, calcium sulfoaluminate cements, and alkali-activated cements.

Natural hydraulic lime mortars: influence of the aggregates

3rd Historic Mortars Conference, 11-14 September 2013, Glasgow, Scotland

Mechanical and mineralogical properties of natural hydraulic lime-metakaolin mortars in different curing conditions

Construction and Building Materials 51 (2014) 287–294

The effect of hydraulic components on lime mortars

XXX IAHS World Congress on Housing - Housing Construction: An Interdisciplinary Task, September 9-13, 2002, Coimbra, Portugal

New natural hydraulic lime mortars – Physical and microstructural properties in different curing conditions

Construction and Building Materials 54 (2014) 378–384

Natural hydraulic lime mortars with ceramic residues for masonry

9th International Masonry Conference 2014, 7-9 July, Universidade do Minho, Guimarães

Rheology of natural hydraulic lime grouts for masonry consolidation

Tese para obtenção do Grau de Doutor em Engenharia Civil, Especialidade Ciências da Construção