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The growth of urbanization worldwide has contributed to the deterioration of the ecological status of water bodies. Efforts at improving the ecological status have been made either in isolated form or by means of integrated measures by stakeholders, but in many cases, these measures have not been evaluated to determine their benefit. In this study, we implemented a scenario analysis to restore the ecological water quality in the Cuenca River and its tributaries, which are located in the southern Andes of Ecuador. For this analysis, an integrated ecological model (IEM) was developed. The IEMlinked an urban wastewater system (IUWS) model, which gave satisfactory results in its calibration and validation processes, with ecological models. The IUWS is a mechanistic model that incorporated the river water quality model, a wastewater treatment plant (WWTP) with activated sludge technology, and discharges from the sewage system. The ecological status of the waterways was evaluated with the Andean Biotic Index (ABI), which was predicted using generalized linear models (GLMs). The GLMs were calculated with physicochemical results from the IUWS model. Four scenarios that would enhance the current ecological water quality were analyzed. In these scenarios, the inclusion of a new WWTP with carbon, and with carbon and nitrogen removal as well as the addition of retention tanks before the discharges of combined sewer overflows (CSOs) were assessed. The new WWTP with carbon and nitrogen removal would bring about a better restoration of the ecological water quality due to better nitrogen removal. The retention tanks would help to enhance the ecological status of the rivers during rainy seasons. The integrated model implemented in this study was shown to be an essential tool to support decisions in the Cuenca River basin management.

This paper aims to stimulate discussion based on the experiences derived from the QUICS project (Quantifying Uncertainty in Integrated Catchment Studies). First it briefly discusses the current state of knowledge on uncertainties in sub-models of integrated catchment models and the existing frameworks for analysing uncertainty. Furthermore, it compares the relative approaches of both building and calibrating fully integrated models or linking separate sub-models. It also discusses the implications of model linkage on overall uncertainty and how to define an acceptable level of model complexity. This discussion includes, whether we should shift our attention from uncertainties due to linkage, when using linked models, to uncertainties in model structure by necessary simplification or by using more parameters. This discussion attempts to address the question as to whether there is an increase in uncertainty by linking these models or if a compensation effect could take place and that overall uncertainty in key water quality parameters actually decreases. Finally, challenges in the application of uncertainty analysis in integrated catchment water quality modelling, as encountered in this project, are discussed and recommendations for future research areas are highlighted.

As sources of greenhouse gas (GHG) emissions, integrated urban drainage systems (IUDSs) (i.e., sewer systems, wastewater treatment plants and receiving water bodies) contribute to climate change. This paper, produced by the International Working Group on Data and Models, which works under the IWA/IAHR Joint Committee on Urban Drainage, reviews the state-of-the-art and modelling tools developed recently to understand and manage GHG emissions from IUDS. Further, open problems and research gaps are discussed and a framework for handling GHG emissions from IUDSs is presented. The literature review reveals that there is a need to strengthen already available mathematical models for IUDS to take GHG into account.

As sources of greenhouse gas (GHG) emissions, integrated urban drainage systems (IUDSs) (i.e., sewer systems, wastewater treatment plants and receiving water bodies) contribute to climate change. This paper, produced by the International Working Group on Data and Models, which works under the IWA/IAHR Joint Committee on Urban Drainage, reviews the state-of-the-art and modelling tools developed recently to understand and manage GHG emissions from IUDS. Further, open problems and research gaps are discussed and a framework for handling GHG emissions from IUDSs is presented. The literature review reveals that there is a need to strengthen already available mathematical models for IUDS to take GHG into account.

Joan Flasch Artists' Book Collection

Strain localization and quasi-brittle failure in frictional-cohesive materials is still an open and challenging problem in computational mechanics. Owing to its complexity and the significant implications on numerous engineering problems, a considerable effort has been devoted to the development of theories and techniques capable of dealing with this topic. The introduction of numerical methods in the 70's provided a way to compute solutions, even if approximated. The Finite Element Method is able to describe a large number of geometries, engineering problems and various boundary conditions and, for this reason, the displacement-based formulation represents the preferred choice in the mechanical analysis of solids. Moreover, assuming the displacement jump created by a crack to be smeared across an element band, the calculation of the onset and the evolution of a fracture can be performed. However, standard finite elements are well-known to behave poorly in the case of strain localization of softening materials. Indeed, the irreducible formulation is mesh-biased and the resulting fracture direction is frequently incorrect. Plasticity constitutive models are largely affected by this issue, being directional by their very nature. In addition, when dealing with isochoric conditions, locking of the stresses provokes spurious pressure oscillations, that spoil the numerical solution. Both problems can be shown not to be related to the mathematical statement of the continuous problem but to its discrete (FEM) counterpart. In this work, a novel mixed e-u strain-displacement finite element method for strain localization and failure in plasticity is presented. Thanks to the independent interpolation of the strain and displacement fields, it is characterized by enhanced kinematic properties which result in an improvement in the accuracy of stresses and deformations. Moreover, it is proved that the numerical quandaries typical of the irreducible formulation are alleviated with t, La resolución de problemas de localización de deformaciones y fallos cuasi-frágiles en materiales friccional-cohesivos sigue siendo un tema abierto a discusión. Debido a su complejidad y a las implicaciones en numerosos problemas de ingeniería, se ha dedicado un considerable esfuerzo al desarrollo de teorías y técnicas capaces de manejar el comportamiento inelástico de los sólidos. La introducción de los métodos numéricos en los años '70 proporcionó técnicas rápidas de cálculo que permitían obtener una solución, aunque aproximada, del problema a tratar. El Método de Elementos Finitos (FEM) es capaz de describir de manera eficiente un gran número de geometrías, problemas de ingeniería y condiciones de contorno, por lo que hace de la formulación irreducible la opción mayoritariamente escogida en el análisis de cuerpos sólidos. Asimismo, considerando la regularización del salto por el desplazamiento producido por una grieta a través de una banda de elementos, es posible calcular la aparición y evolución de una fractura. Sin embargo, los elementos finitos estándar se comportan de manera inadecuada en cálculos de localización de deformaciones en materiales con ablandamiento. La formulación irreducible está altamente influenciada por la malla empleada, y frecuentemente la dirección de fractura resultante es incorrecta. Este fenómeno aparece de manera significativa en plasticidad, siendo ortotrópica. De igual manera, con modelos isocóricos, el bloqueo de las deformaciones provoca oscilaciones de presión espurias, que hacen inutilizable la solución numérica obtenida. Es posible demostrar que ambos problemas no están relacionados por la definición continua del problema, sino con su formulación discreta. En este trabajo se presenta una nueva formulación mixta e-u de elementos finitos en desplazamientos y deformaciones para la localización de deformaciones y fallo en plasticidad. Solucionando independientemente deformaciones y desplazamientos, la formulación se caracteriza por, Postprint (published version)

The testing of mode III and mixed mode failure is every so often encountered in the dedicated literature of mechanical characterization of brittle and quasi-brittle materials. In this work, the application of the mixed strain displacement e-ue-u finite element formulation to three examples involving skew notched beams is presented. The use of this FE technology is effective in problems involving localization of strains in softening materials. The objectives of the paper are: (i) to test the mixed formulation in mode III and mixed mode failure and (ii) to present an enhancement in terms of computational time given by the kinematic compatibility between irreducible displacement-based and the mixed strain-displacement elements. Three tests of skew-notched beams are presented: firstly, a three point bending test of a PolyMethyl MethaAcrylate beam; secondly, a torsion test of a plain concrete prismatic beam with square base; finally, a torsion test of a cylindrical beam made of plain concrete as well. To describe the mechanical behavior of the material in the inelastic range, Rankine and Drucker-Prager failure criteria are used in both plasticity and isotropic continuum damage formats. The proposed mixed formulation is capable of yielding results close to the experimental ones in terms of fracture surface, peak load and global loss of carrying capability. In addition, the symmetric secant formulation and the compatibility condition between the standard irreducible method and the strain-displacement one is exploited, resulting in a significant speedup of the computational procedure., Peer Reviewed, Postprint (author's final draft)

Nitrous oxide (N2O) is a strong greenhouse gas (GHG) and ozone depleter, with a warming potential 300 times higher than carbon dioxide (CO2). 1.2% of the total antrophopogenic N2O emissions are believed to originate from the wastewater treatment (WWT) sector. Conventional biological nutrient removal processes relying on nitrification and denitrification are known to produce N2O. A one year long-term study of N2O production and emissions was performed at Lynetten, Denmark’s largest WWTP. Nitrification and denitrification takes place by alternating process conditions as well as influent and effluent flows in 20 pairs of interconnected and surface aerated reactors. The long-term data revealed that the N2O emissions contribute to as much as 30% of the total CO2 footprint from the WWTP. High ammonium concentrations and long aeration phases lead to high N2O production and emissions rates. Nitrification phases were identified to produce and emit most of the N2O. High production and emissions were also associated with the afternoon loading peaks at the WWTP. During denitrification phases N2O was produced initially but consumed consequently. An effective control strategy was implemented, whereby N2O emissions were reduced from 0.8% to 0.3% of the nitrogen load during the mitigation period.

This paper presents the 2D and 3D numerical analysis of pullout tests on steel anchorages in concrete blocks using standard and mixed finite elements. A novel (stabilized) mixed formulation in the variables of total strain 8 and displacements u is introduced to overcome the intrinsic deficiencies of the standard displacement-based one in the context of localization of strains, such as mesh dependency. The quasi brittle behavior of concrete is described through an elastoplastic constitutive law with a local Rankine yielding criterion. The proposed formulation is shown to be a reliable and accurate tool, sensitive to the physical parameters of the pullout tests, but objective with respect to the adopted FE mesh. Furthermore, the mixed epsilon/u finite element is able to capture the correct failure mechanism with relatively coarse discretizations. At the same time, the spurious behavior of the standard formulation is not alleviated by mesh-refinement., Peer Reviewed, Postprint (author's final draft)

This paper presents the application of a stabilized mixed strain/displacement finite element formulation for the solution of nonlinear solid mechanics problems involving compressible and incompressible plasticity. The variational multiscale stabilization introduced allows the use of equal order interpolations in a consistent way. Such formulation presents two advantages when compared to the standard, displacement based, irreducible formulation: (a) it provides enhanced rate of convergence for the strain (and stress) field and (b) it is able to deal with incompressible situations. The first advantage also applies to the comparison with the mixed pressure/displacement formulation. The paper investigates the effect of the improved strain and stress fields in problems involving strain softening and localization leading to failure, using low order finite elements with continuous strain and displacement fields (P1P1 triangles or tetrahedra and Q1Q1 quadrilaterals, hexahedra, and triangular prisms) in conjunction with an associative frictional Drucker-Prager plastic model. The performance of the strain/displacement formulation under compressible and nearly incompressible deformation patterns is assessed and compared to a previously proposed pressure/displacement formulation. Benchmark numerical examples show the capacity of the mixed formulation to predict correctly failure mechanisms with localized patterns of strain, virtually free from any dependence of the mesh directional bias. No auxiliary crack tracking technique is necessary., Peer Reviewed, Postprint (author’s final draft)

The development of slip lines, due to strain localization, is a common cause for failure of soil in many circumstances investigated in geotechnical engineering. Through the use of numerical methods - like finite elements - many practitioners are able to take into account complex geometrical and physical conditions in their analyses. However, when dealing with shear bands, standard finite elements display lack of precision, mesh dependency and locking. This paper introduces a (stabilized) mixed finite element formulation with continuous linear strain and displacement interpolations. Von Mises and Drucker-Prager local plasticity models with strain softening are considered as constitutive law. This innovative formulation succeeds in overcoming the limitations of the standard formulation and provides accurate results within the vicinity of the shear bands, specifically without suffering from mesh dependency. Finally, 2D and 3D numerical examples demonstrate the accuracy and robustness in the computation of localization bands, without the introduction of additional tracking techniques as usually required by other methods. (C) 2014 Elsevier Ltd. All rights reserved., Peer Reviewed, Postprint (author’s final draft)

This project aims at finding cost-efficient adaptive measures to meet the EU Water Framework Directive goals for the Dommel River (The Netherlands). Both acute and long-term impacts of the urban wastewater system (treatment plant and sewers) on the chemical and ecological quality of the river are studied. An integrated model, which proved to be a powerful tool to analyse the interactions within the integrated urban wastewater system, was used to evaluate several different measures in the urban wastewater system both using the existing as well as new infrastructure and real-time control (RTC) strategies. In this paper, emphasis is put on the results from the latest integrated RTC design and model-based evaluation, and on the first tests on the real system of selected measures, i.e. modified primary treatment, and improved rain buffer tank control and in-stream aeration.

The success of many modelling studies strongly depends on the availability of sufficiently long influent time series - the main disturbance of a typical wastewater treatment plant (WWTP) - representing the inherent natural variability at the plant inlet as accurately as possible. This is an important point since most modelling projects suffer from a lack of realistic data representing the influent wastewater dynamics. The objective of this paper is to show the advantages of creating synthetic data when performing modelling studies for WWTPs. This study reviews the different principles that influent generators can be based on, in order to create realistic influent time series. In addition, the paper summarizes the variables that those models can describe: influent flow rate, temperature and traditional/emerging pollution compounds, weather conditions (dry/wet) as well as their temporal resolution (from minutes to years). The importance of calibration/validation is addressed and the authors critically analyse the pros and cons of manual versus automatic and frequentistic vs Bayesian methods. The presentation will focus on potential engineering applications of influent generators, illustrating the different model concepts with case studies. The authors have significant experience using these types of tools and have worked on interesting case studies that they will share with the audience. Discussion with experts at the WWTmod seminar shall facilitate identifying critical knowledge gaps in current WWTP influent disturbance models. Finally, the outcome of these discussions will be used to define specific tasks that should be tackled in the near future to achieve more general acceptance and use of WWTP influent generators.

Joan Flasch Artists' Book Collection

In WWTP models, the accurate assessment of solids inventory in bioreactors equipped with solidliquid separators, mostly described using one-dimensional (1-D) secondary settling tank (SST) models, is the most fundamental requirement of any calibration procedure. Scientific knowledge on characterising particulate organics in wastewater and on bacteria growth is well-established, whereas 1-D SST models and their impact on biomass concentration predictions are still poorly understood. A rigorous assessment of two 1-DSST models is thus presented: one based on hyperbolic (the widely used Taka´ cs-model) and one based on parabolic (the more recently presented Plo´ sz-model) partial differential equations. The former model, using numerical approximation to yield realistic behaviour, is currently the most widely used by wastewater treatment process modellers. The latter is a convection-dispersion model that is solved in a numerically sound way. First, the explicit dispersion in the convection-dispersion model and the numerical dispersion for both SST models are calculated. Second, simulation results of effluent suspended solids concentration (XTSS,Eff), sludge recirculation stream (XTSS,RAS) and sludge blanket height (SBH) are used to demonstrate the distinct behaviour of the models. A thorough scenario analysis is carried out using SST feed flow rate, solids concentration, and overflow rate as degrees of freedom, spanning a broad loading spectrum. A comparison between the measurements and the simulation results demonstrates a considerably improved 1-D model realism using the convection-dispersion model in terms of SBH, XTSS,RAS and XTSS,Eff. Third, to assess the propagation of uncertainty derived from settler model structure to the biokinetic model, the impact of the SST model as sub-model in a plant-wide model on the general model performance is evaluated. A long-term simulation of a bulking event is conducted that spans temperature evolution throughout a summer/winter seq

Activated Sludge Models are widely used for simulation-based evaluation of wastewater treatment plant (WWTP) performance. However, due to the high workload and cost of a measuring campaign on a full-scale WWTP, many simulation studies suffer from lack of sufficiently long influent flow rate and concentration time series representing realistic wastewater influent dynamics. In this paper, a simple phenomenological modelling approach is proposed as an alternative to generate dynamic influent pollutant disturbance scenarios. The presented set of models is constructed following the principles of parsimony (limiting the number of parameters as much as possible), transparency (using parameters with physical meaning where possible) and flexibility (easily extendable to other applications where long dynamic influent time series are needed). The proposed approach is sub-divided in four main model blocks: 1) model block for flow rate generation, 2) model block for pollutants generation (carbon, nitrogen and phosphorus), 3) model block for temperature generation and 4) model block for transport of water and pollutants. The paper is illustrated with the results obtained during the development of the dynamic influent of the Benchmark Simulation Model no. 2 (BSM2). The series of simulations show that it is possible to generate a dry weather influent describing diurnal flow rate dynamics (low rate at night, high rate during day time), weekend effects (with different flow rate during weekends, compared to weekdays), holiday effects (where the wastewater production is assumed to be different for a number of weeks) and seasonal effects (with variations in the infiltration and thus also the flow rate to the WWTP). In addition, the dry weather model can be extended with a rain and storm weather generator, where the proposed phenomenological model can also mimic the “first flush” effect from the sewer network and the influent dilution phenomena that are typically observed at full-scale W

The objective of Task 7.5 was to develop tools for model-based planning of sampling campaigns in the design of monitoring strategies for priority pollutant emission barriers. Using integrated urban wastewater system (IUWS) models, measurement campaigns can be designed to improve the calibration of the model‟s parameters (Optimal Experiment Design for Parameter Estimation (OED/PE)). Furthermore, the knowledge contained in the IUWS models can be used to optimize the planning of sampling campaigns aiming at assessing the efficiency of emission control strategies. To do this, the emission barriers need to be implemented in the IUWS model, as well as the sampling and measuring devices that will be used. The simulation results are presented as a Substance Flow Analysis (SFA). These SFAs can be compared with empirical SFAs and can also be used to set up measurement campaigns aiming at gathering information to establish or improve empirical SFAs (OED/SFA). Moreover, the national Danish environmental monitoring programs were compared to the US programs under the Clean Water Act and the proposed environmental monitoring of the European water courses as described in the European Water Framework Directive. Also, kinetic passive sampling methods for the measurement of average water concentrations are presented.

The objective of Task 7.5 was to develop tools for model-based planning of sampling campaigns in the design of monitoring strategies for priority pollutant emission barriers. Using integrated urban wastewater system (IUWS) models, measurement campaigns can be designed to improve the calibration of the model‟s parameters (Optimal Experiment Design for Parameter Estimation (OED/PE)). Furthermore, the knowledge contained in the IUWS models can be used to optimize the planning of sampling campaigns aiming at assessing the efficiency of emission control strategies. To do this, the emission barriers need to be implemented in the IUWS model, as well as the sampling and measuring devices that will be used. The simulation results are presented as a Substance Flow Analysis (SFA). These SFAs can be compared with empirical SFAs and can also be used to set up measurement campaigns aiming at gathering information to establish or improve empirical SFAs (OED/SFA). Moreover, the national Danish environmental monitoring programs were compared to the US programs under the Clean Water Act and the proposed environmental monitoring of the European water courses as described in the European Water Framework Directive. Also, kinetic passive sampling methods for the measurement of average water concentrations are presented.

Il presente lavoro si propone di approfondire il tema della “responsabilità nel gruppo” , così come disciplinata dalla riforma del diritto societario. In particolare la riflessione si concentrerà sulle due diverse fattispecie di responsabilità disciplinate al II co., dell’art. 2497 c.c., al fine di -ricostruirne gli elementi costitutivi e i connotati; -proporne un inquadramento sistematico nel contesto del microsistema normativo della responsabilità speciale nel gruppo e, più ampiamente, delle categorie generali del dritto civile. A tal fine si è ritenuto indispensabile procedere preliminarmente a ricostruire la natura della responsabilità di cui al I co. dell’art. 2497 c.c. (cap. I), posto che il II comma, prima parte, di tale disposizione prevede l’imputazione di un’obbligazione risarcitoria solidale a “chiunque abbia preso parte al fatto lesivo”. Poiché con questa espressione si introduce, inequivocabilmente, una responsabilità da concorso, occorre stabilire quale sia il fatto al quale si prende parte. D’altronde l’intesse a definire la responsabilità per abuso di eterodirezione deriva dal fatto che, come si cercherà di dimostrare compiutamente, la responsabilità sia di “chi abbia preso comunque parte al fatto lesivo”, sia di “chi ne abbia tratto consapevolmente beneficio” risulta essere, già in base all’inequivoco tenore letterale della norma, accessoria e dipendente dalla prima. La riflessione relativa alla responsabilità principale da direzione e coordinamento contra legem è stata condotta alla luce delle diverse teorie proposte dalla dottrina civilistica per di distinguere l’ambito della responsabilità extracontrattuale da quella da inadempimento. La medesima indagine ha cercato di individuare anche l’oggetto e la fonte dell’obbligo di esercitare l’eterodirezione in conformità ai principi di corretta gestione societaria e imprenditoriale. La ricostruzione della responsabilità prevista al I comma dell’art. 2497 c.c. ha costituito, inoltre, un riferimento indis, This work deals with the new italian law of the liability in the groups of companies (art. 2497 c.c., which took effect with the reform of corporate law. In the first chapter we try to establish if the first paragraph of the art. 2497 c.c.provide for a contractual liability, due to a breach of a pre-existent obligation; or a tort liability, due to the commission of a tort. The second chapter analises the first part of the second paragraph of art. 2497 c.c. to establish the nature and the systematic function of the liability of who take part in the abuse of the holding company. The third chapter talks about the liability of the aware beneficiary (second part of the second paragraph of art. 2497 c.c.): in this work we try to establish the nature of the liability , considered as a case of unjustified enrichment (art. 2041 c.c.). In the last two chapter we apply the results of the previous reflection to: the case of the holding-individual person, to establish which discipline we must apply to it, which the first paragraph of the art. 2497 c.c.doesn't provide for; establish if the liability in the group can be applied to the bank, when it is holding, concurrent in its tort or aware beneficiary.

In the recent decade, the request for structural health monitoring expertise increased exponentially in the United States. The aging issues that most of the transportation structures are experiencing can put in serious jeopardy the economic system of a region as well as of a country. At the same time, the monitoring of structures is a central topic of discussion in Europe, where the preservation of historical buildings has been addressed over the last four centuries. More recently, various concerns arose about security performance of civil structures after tragic events such the 9/11 or the 2011 Japan earthquake: engineers looks for a design able to resist exceptional loadings due to earthquakes, hurricanes and terrorist attacks. After events of such a kind, the assessment of the remaining life of the structure is at least as important as the initial performance design. Consequently, it appears very clear that the introduction of reliable and accessible damage assessment techniques is crucial for the localization of issues and for a correct and immediate rehabilitation. The System Identification is a branch of the more general Control Theory. In Civil Engineering, this field addresses the techniques needed to find mechanical characteristics as the stiffness or the mass starting from the signals captured by sensors. The objective of the Dynamic Structural Identification (DSI) is to define, starting from experimental measurements, the modal fundamental parameters of a generic structure in order to characterize, via a mathematical model, the dynamic behavior. The knowledge of these parameters is helpful in the Model Updating procedure, that permits to define corrected theoretical models through experimental validation. The main aim of this technique is to minimize the differences between the theoretical model results and in situ measurements of dynamic data. Therefore, the new model becomes a very effective control practice when it comes to rehabilitation of structures

In the recent decade, the request for structural health monitoring expertise increased exponentially in the United States. The aging issues that most of the transportation structures are experiencing can put in serious jeopardy the economic system of a region as well as of a country. At the same time, the monitoring of structures is a central topic of discussion in Europe, where the preservation of historical buildings has been addressed over the last four centuries. More recently, various concerns arose about security performance of civil structures after tragic events such the 9/11 or the 2011 Japan earthquake: engineers looks for a design able to resist exceptional loadings due to earthquakes, hurricanes and terrorist attacks. After events of such a kind, the assessment of the remaining life of the structure is at least as important as the initial performance design. Consequently, it appears very clear that the introduction of reliable and accessible damage assessment techniques is crucial for the localization of issues and for a correct and immediate rehabilitation. The System Identification is a branch of the more general Control Theory. In Civil Engineering, this field addresses the techniques needed to find mechanical characteristics as the stiffness or the mass starting from the signals captured by sensors. The objective of the Dynamic Structural Identification (DSI) is to define, starting from experimental measurements, the modal fundamental parameters of a generic structure in order to characterize, via a mathematical model, the dynamic behavior. The knowledge of these parameters is helpful in the Model Updating procedure, that permits to define corrected theoretical models through experimental validation. The main aim of this technique is to minimize the differences between the theoretical model results and in situ measurements of dynamic data. Therefore, the new model becomes a very effective control practice when it comes to rehabilitation of structures