Combining robustness and recovery for airline schedules

In this thesis, we address different aspects of the airline scheduling problem. The main difficulty in this field lies in the combinatorial complexity of the problems. Furthermore, as airline schedules are often faced with perturbations called disruptions (bad weather conditions, technical failures, congestion, crew illness…), planning for better performance under uncertainty is an additional dimension to the complexity of the problem. Our main focus is to develop better schedules that are less sensitive to perturbations and, when severe disruptions occur, are easier to recover. The former property is known as robustness and the latter is called recoverability. We start the thesis by addressing the problem of recovering a disrupted schedule. We present a general model, the constraint-specific recovery network, that encodes all feasible recovery schemes of any unit of the recovery problem. A unit is an aircraft, a crew member or a passenger and its recovery scheme is a new route, pairing or itinerary, respectively. We show how to model the Aircraft Recovery Problem (ARP) and the Passenger Recovery Problem (PRP), and provide computational results for both of them. Next, we present a general framework to solve problems subject to uncertainty: the Uncertainty Feature Optimization (UFO) framework, which implicitly embeds the uncertainty the problem is prone to. We show that UFO is a generalization of existing methods relying on explicit uncertainty models. Furthermore, we show that by implicitly considering uncertainty, we not only save the effort of modeling an explicit uncertainty set: we also protect against possible errors in its modeling. We then show that combining existing methods using explicit uncertainty characterization with UFO leads to more stable solutions with respect to changes in the noise's nature. We illustrate these concepts with extensive simulations on the Multi-Dimensional Knapsack Problem (MDKP). We then apply the UFO to airline scheduling. First, we study how robustness is defined in airline scheduling and then compare robustness of UFO models against existing models in the literature. We observe that the performance of the solutions closely depend on the way the performance is evaluated. UFO solutions seem to perform well globally, but models using explicit uncertainty have a better potential when focusing on a specific metric. Finally, we study the recoverability of UFO solutions with respect to the recovery algorithm we develop. Computational results on a European airline show that UFO solutions are able to significantly reduce recovery costs

Design, synthesis, and evaluation of poly(1,2-glycerol carbonate)-paclitaxel conjugate nanoparticles for the tunable delivery of paclitaxel

Since their initial conceptualization, polymer-drug conjugate nanocarriers have been a mainstay of the drug delivery field. The conjugation of therapeutic agents to polymeric carriers offers several critical advantages including improved drug solubilization, controlled release, and enhanced safety. Accordingly, polymer-drug conjugate nanocarriers are uniquely positioned to remedy some of the limitations of conventional small molecule chemotherapeutics, namely their narrow window of therapeutic efficacy, rapid clearance, and limited tumor exposure. This dissertation describes the design, synthesis, and evaluation of a novel sustained release, biodegradable polymeric nanocarrier as a single administration replacement of multi-dose paclitaxel (PTX) treatment regimens. The synthesis of poly(1,2-glycerol carbonate)-graft-succinic acid-paclitaxel (PGC-PTX) is presented, and its use enables high, controlled PTX loadings. Moreover, the polymer backbone is composed of biocompatible building blocks—glycerol and carbon dioxide. When formulated as nanoparticles (NPs), PGC-PTX NPs exhibit high aqueous PTX concentrations, sub-100 nm diameters, narrow dispersity, prolonged storage stability, and sustained and controlled PTX release kinetics. In murine models of peritoneal carcinomatosis, in which the clinical implementation of multi-dose intraperitoneal (IP) treatment regimens is limited by catheter-related complications, PGC-PTX NPs exhibit improved safety at high doses, tumor localization, and efficacy even after a single IP injection, with comparable therapeutic effect to multi-dose IP PTX treatment regimens. The PGC-PTX NP platform is additionally amenable to optimization via modulation of nanocarrier properties. Specifically, the dual conjugation and physical entrapment of PTX in the NPs harnesses the physicochemical interactions between free and conjugated PTX to achieve unprecedented ultra-high drug loadings as well as facile control of nanomechanical properties and release kinetics. Optimization of these programmable carriers consequently enables the safe delivery of high drug doses as well as sustained therapeutic efficacy. In a murine model of peritoneal carcinomatosis, a single high dose of dual-loaded PGC-PTX nanocarriers affords significantly improved survival compared to weekly, multi-dose PTX treatment. Modulation of nanocarrier properties via the incorporation of poly(lactide-co-glycolide) (PLGA) is additionally explored. Although the integration of PLGA does not significantly alter NP physical properties, the polymer blend nanocarriers exhibit improved in vitro potency relative to PGC-PTX NPs, warranting the continued evaluation of the mechanism by which PLGA modulates nanocarrier efficacy.2020-07-02T00:00:00

Grazing time: the missing link : a study of the plant-animal interface by integration of experimental and modelling approaches

A series of grazing (chapters 2, 3, 5 and 6) in-vitro (chapter 4) and modelling trials (chapters 1 and 7) were combined with the following objectives: a) to gain insight in the main mechanisms controlling dry matter intake (DMI), intake rate (IR) and grazing time (GT), during the first grazing session after a.m. milking, b) to judge the relative importance of rumen fill and the concentration of fermentation products in the rumen liquor as candidates to signal the end of the grazing sessions and c) to develop new and modify and evaluate existing simulation model, to operate under non-steady state conditions with the aim to predict DMI, rumen fermentation and supply of nutrients.Increasing the length of the allowed grazing time significantly increased DMI (PThe interaction between starvation time and rumen fill before grazing on GT, although not significant (PThis research offered valuable information about the relative importance of several factors in the control of GT. Clearly it is necessary to understand the way in which the different signals produced at different places are integrated for the animal to modulate eating and other behaviour. In this sense the combination of analytical and synthetic research was proven to be an effective strategy.PhD Thesis, Animal Nutrition Group, Wageningen Agricultural University, Marijkeweg 40, 6709 PG, Wageningen, The Netherlands.</p

Improvement of anterior and posterior segment ocular drug delivery: application in ocular cystinosis and age-related macular degeneration

In this doctoral thesis, hydrogel-based formulations containing cysteamine of great potential for the treatment of ocular cystinosis have been developed. The hydrogel based on hyaluronic acid polymer has been extensively characterised and its preparation has been translated to Hospital Pharmacy Departments. On the other hand, regarding the study of intravitreal injections in AMD, this thesis has demonstrated the usefulness of the PET methodology for the study of intravitreal pharmacokinetics in rats, which has been subsequently used for the evaluation of the ocular pharmacokinetics after intravitreal administration of aflibercept and bevacizumab. Moreover, intravitreal chitosan-based implants containing aflibercept which permit its extended delivery have been developed

Algorithmes d'approximation pour des programmes linéaires et les problèmes de Packing avec des contraintes géometriques

In this thesis we approach several problems with approximation algorithms; these are feasibility problems as well as optimization problems. In Chapter 1 we give a brief introduction into the general paradigm of approximation algorithms, motivate the problems, and give an outline of the thesis. In Chapter 2, we discuss two algorithms to approximately generate a feasible solution of the mixed packing and covering problem which is a model from convex optimization. This problem includes a large class of linear programs. The algorithms generate approximately feasible solutions within O(M(ln M+epsilon^{-2} ln epsilon^{-1})) and O(M epsilon{-2} ln (M epsilon^{-1}))$iterations, respectively, where in each iteration a block problem which depends on the specific application has to be solved. Both algorithms, applied to linear programs, can result in column generation algorithms. In Chapter 3, we implement an algorithm for the so-called max-min-resource sharing problem. This is a certain convex optimization problem which, similar to the problem in Chapter 1, includes a large class of linear programs. The implementation, which is included in the appendix, is done in C++. We use the implementation in the context of an AFPTAS for Strip Packing in order to evaluate dynamic optimization of a parameter in the algorithm, namely the step length used for interpolation. We compare our choice to the static step length proposed in the analysis of the algorithm and conclude that dynamic optimization of the step length significantly reduces the number of iterations. In Chapter 4, we study two closely related scheduling problems, namely non-preemptive scheduling with fixed jobs and scheduling with non-availability for sequential jobs on m identical machines under the makespan objective, where m is constant. For the first problem, which does not admit an FPTAS unless P=NP, we obtain a new PTAS. For the second problem, we show that a suitable restriction (namely the permanent availability of one machine) is necessary to obtain a bounded approximation ratio. For this restriction, which does not admit an FPTAS unless P=NP, we present a PTAS; we also discuss the complexity of various special cases. In total, the results are basically best possible. In Chapter 5, we continue the studies from Chapter 4 where now the number m of machines is part of the input, which makes the problem algorithmically harder. Scheduling with fixed jobs does not admit an approximation ratio better than 3/2, unless P=NP; here we obtain an approximation ratio of 3/2+epsilon for any epsilon>0. For scheduling with non-availability, we require a constant percentage of the machines to be permanently available. This restriction also does not admit an approximation ratio better than 3/2 unless P=NP; we also obtain an approximation ratio of$3/2+\epsilon$ for any epsilon>0. With an interesting argument, the approximation ratio for both problems is refined to exactly 3/2. We also point out an interesting relation of scheduling with fixed jobs to Bin Packing. As in Chapter 4, the results are in a certain sense best possible. Finally, in Chapter 6, we conclude with some remarks and open research problems

Algorithmes d'approximation pour des programmes linéaires et les problèmes de Packing avec des contraintes géometriques

In this thesis we approach several problems with approximation algorithms; these are feasibility problems as well as optimization problems. In Chapter 1 we give a brief introduction into the general paradigm of approximation algorithms, motivate the problems, and give an outline of the thesis. In Chapter 2, we discuss two algorithms to approximately generate a feasible solution of the mixed packing and covering problem which is a model from convex optimization. This problem includes a large class of linear programs. The algorithms generate approximately feasible solutions within O(M(ln M+epsilon^{-2} ln epsilon^{-1})) and O(M epsilon{-2} ln (M epsilon^{-1}))$iterations, respectively, where in each iteration a block problem which depends on the specific application has to be solved. Both algorithms, applied to linear programs, can result in column generation algorithms. In Chapter 3, we implement an algorithm for the so-called max-min-resource sharing problem. This is a certain convex optimization problem which, similar to the problem in Chapter 1, includes a large class of linear programs. The implementation, which is included in the appendix, is done in C++. We use the implementation in the context of an AFPTAS for Strip Packing in order to evaluate dynamic optimization of a parameter in the algorithm, namely the step length used for interpolation. We compare our choice to the static step length proposed in the analysis of the algorithm and conclude that dynamic optimization of the step length significantly reduces the number of iterations. In Chapter 4, we study two closely related scheduling problems, namely non-preemptive scheduling with fixed jobs and scheduling with non-availability for sequential jobs on m identical machines under the makespan objective, where m is constant. For the first problem, which does not admit an FPTAS unless P=NP, we obtain a new PTAS. For the second problem, we show that a suitable restriction (namely the permanent availability of one machine) is necessary to obtain a bounded approximation ratio. For this restriction, which does not admit an FPTAS unless P=NP, we present a PTAS; we also discuss the complexity of various special cases. In total, the results are basically best possible. In Chapter 5, we continue the studies from Chapter 4 where now the number m of machines is part of the input, which makes the problem algorithmically harder. Scheduling with fixed jobs does not admit an approximation ratio better than 3/2, unless P=NP; here we obtain an approximation ratio of 3/2+epsilon for any epsilon>0. For scheduling with non-availability, we require a constant percentage of the machines to be permanently available. This restriction also does not admit an approximation ratio better than 3/2 unless P=NP; we also obtain an approximation ratio of$3/2+\epsilon$ for any epsilon>0. With an interesting argument, the approximation ratio for both problems is refined to exactly 3/2. We also point out an interesting relation of scheduling with fixed jobs to Bin Packing. As in Chapter 4, the results are in a certain sense best possible. Finally, in Chapter 6, we conclude with some remarks and open research problems

Annual Report 2018-2019

It contains the statement of R&D works undertaken, achievement made and the expenditure by the laboratory during the financial year 2018-2019

Advanced oxidation process models for optimisation and decision making support in water management

The objective of this thesis is contributing to the development of a systematic modelling approach for a more efficient and sustainable water management. The main aim is introducing Chemical and Process System Engineering methods and tools to provide a contribution to the AOPs (Advanced Oxidation Processes) investigation field by proposing process models that can be exploited to progress towards efficient management strategies for practical AOPs operation and inclusion in wastewater treatment networks. First, different advanced oxidation processes, namely Fenton, photo-Fenton and VUV photo-oxidation, were investigated and compared for the treatment of paracetamol (PCT) aqueous solution, by evaluating a series of performance indicators. Among the selected AOPs, VUV photo-oxidation and photo-Fenton showed the most promising results. Both processes allowed attaining total removal of the target compound and high mineralization levels. The second and main part of the thesis was focused on transforming “data into knowledge” by proposing different modelling approaches. The modelling effort focused on Fenton/photo-Fenton processes that showed the need of improving operating conditions. Accordingly, two practical kinetic models for Fenton and photo-Fenton degradation of organic compounds have been proposed and validated: • A conventional First Principles Model, based on a line source radiation model with spherical and isotropic emission, developed for the prediction of Fenton and photo-Fenton degradation of PCT and the oxidant (H2O2) consumption; • A general non-conventional First Principles Model, based on a wide-ranging contaminant degradation mechanism considering a variable number of carbon atoms for the characterization of the intermediates. Both models were experimentally validated and showed that were able to satisfactorily reproduce the system behavior. Particularly, the non-conventional First Principles Model showed to be a successful modelling approach for the Fenton/photo-Fenton degradation of different wastewater systems composed by single or multiple organic contaminants by means of lumped parameters (e.g. Total Organic Carbon-TOC). Thus, the approach proved to offer practical characterization of complex mixtures of chemicals. Once process models are proposed and validated, they can be systematically exploited to determine efficient operation modes or design alternatives. Accordingly, the thesis addressed two cases of practical interest: the optimization of a control recipe and the design of a treatment network. Particularly, a dynamic optimization framework for taking advantage of available kinetic models and determining the best hydrogen peroxide dosage profile, was proposed. Economic and environmental objectives and constraints were included to develop a dynamic optimization problem that was implemented in JModelica and solved using a direct simultaneous optimization method (IPOPT). Finally, the combination of cheaper conventional biological processes with more expensive AOPs was explored. A Mixed-Integer Non Linear Programming (MINLP) model for the optimization of a general wastewater network was proposed based on a superstructure of alternative designs, which was implemented and solved in GAMS. The novel formulation includes the BOD5/COD ratio method, describing the removal efficiency of BOD5 and COD of a treatment for modelling the variation of the biodegradability of the influents. This novel formulation allows determining the extent of the AOP treatments when combined with biological treatments, and paves the way for more complex models aimed at solving the trade-off between cost and treatment efficiency.El objetivo de esta tesis es contribuir al desarrollo de técnicas de modelado sistemático para una gestión del agua eficiente y sostenible. El objetivo principal es contribuir a la investigación de los PAOs (Procesos Avanzados de Oxidación). La tesis introduce métodos y herramientas de Ingeniería de Procesos Químicos y propone modelos que puedan ser explotados para producir estrategias eficientes de gestión y operación de los PAOs, así como para la integración de estos PAOs en redes de tratamiento de aguas residuales. Primero, se investigaron diferentes PAOs. Se consideraron los procesos Fenton, foto-Fenton y la foto-oxidación VUV, y se compararon en el tratamiento de soluciones acuosas de paracetamol (PCT) adoptando una serie de indicadores de rendimiento (Key Performance Indicators, KPI). Entre los PAOs seleccionados, la foto-oxidación VUV y foto-Fenton producieron los resultados más prometedores, permitiendo lograr la eliminación total del contaminante y alto nivel de mineralización. La segunda parte de la tesis se centró en transformar ¿datos en conocimiento¿ mediante la propuesta de modelos para los procesos Fenton / photo-Fenton con el fin de mejorar las condiciones operativas de los mismos. En concreto se han propuesto y validado dos modelos cinéticos que describen la degradación de compuestos orgánicos por procesos Fenton y foto-Fenton: ¿ Un Modelo de Principios Básicos (F convencional, que incluye la modelización de la radiación lineal con emisión esférica e isotrópica, desarrollado para predecir la degradación Fenton y foto-Fenton del PCT y el consumo de oxidante (H2O2); ¿ Un Modelo de Principios Básicos no convencional, que propone un mecanismo de degradación de contaminantes general puesto que considera el número de átomos de carbono del contaminante como la variable de partida para la propuesta de fragmentación y consiguiente generación de intermedios. Ambos modelos se validaron experimentalmente y mostraron reproducir satisfactoriamente el comportamiento del sistema. En particular, el Modelo de Principios Básicos no convencional genero resultados prometedores para la degradación Fenton / foto-Fenton de diferentes sistemas (compuestos por uno o más contaminantes orgánicos) por medio de parámetros globales (como el Carbono Orgánico Total). Por tanto, este enfoque ofrece un modelado práctico independiente del contaminante y válido para mezclas complejas de productos químicos. Una vez propuestos y validados, los modelos de proceso se pueden utilizar sistemáticamente para determinar modos de operación eficientes o alternativas de diseño. En consecuencia, la tesis se dirigió a dos casos de interés práctico: la optimización de una receta de control y el diseño de una red de tratamiento. En el primer caso, se propuso una estrategia de optimización dinámica para aprovechar los modelos cinéticos disponibles y determinar el mejor perfil de dosificación de peróxido de hidrógeno. Se incluyeron objetivos y limitaciones económicas y ambientales para desarrollar un problema de optimización dinámica que se implementó en JModelica y se resolvió utilizando un método de optimización simultánea directa (IPOPT). Finalmente, se exploró la combinación de procesos biológicos convencionales, más baratos, con PAOs, más costosos. Se propuso un modelo de Programación no Lineal de Enteros Mixtos (MINLP) para la optimización de una red general de aguas residuales, basado en una superestructura de diseños alternativos, que se implementó y resolvió en GAMS. La nueva formulación incluye la relación BOD5 / COD, que describe la eficiencia de eliminación de BOD5 y COD de un tratamiento con el fin de modelar la variación de la biodegradabilidad de los influentes. Esta novedosa formulación permite determinar el alcance de los tratamientos de PAOs cuando se combinan con tratamientos biológicos, y allana el camino para modelos más complejos destinados a resolver el equilibrio entre coste y eficiencia del tratamiento.L'objectiu d'aquesta tesi és contribuir al desenvolupament de tècniques de modelatge sistemàtic per a una gestió de l'aigua eficient i sostenible. L'objectiu principal és contribuir a la investigació dels PAOs (Processos Avançats d'Oxidació). La tesi introdueix mètodes i eines d'Enginyeria de Processos Químics i proposa models que puguin ser explotats per produir estratègies eficients de gestió i operació dels PAOs, així com per a la integració d'aquests PAOs en xarxes de tractament d'aigües residuals. Primer, es van investigar diferents PAOs. Es van considerar els processos Fenton, foto-Fenton i la foto-oxidació VUV, i es van comparar en el tractament de solucions aquoses de paracetamol (PCT) adoptant una sèrie d'indicadors de rendiment (Key Performance Indicators, KPI). Entre els PAOs seleccionats, la foto-oxidació VUV i foto-Fenton van produir els resultats més prometedors, permetent aconseguir l'eliminació total del contaminant i alt nivell de mineralització. La segona part de la tesi es va centrar en transformar "dades en coneixement" mitjançant la proposta de models per als processos Fenton / photo-Fenton amb la finalitat de millorar les condicions operatives dels mateixos. En concret, s’han proposat i validat dos models cinètics que descriuen la degradació de compostos orgànics per processos Fenton i foto-Fenton: • Un model de Principis Bàsics convencional, que inclou la modelització de la radiació lineal amb emissió esfèrica i isotròpica, desenvolupat per predir la degradació Fenton i foto-Fenton del PCT i el consum d'oxidant (H2O2); • Un model de Principis Bàsics no convencional que proposa un mecanisme de degradació de contaminants general, ja que considera el nombre d'àtoms de carboni del contaminant com la variable de partida per a la proposta de fragmentació i consegüent generació d'intermedis. Tots dos models es van validar experimentalment i van mostrar la seva capacitat de reproduir satisfactòriament el comportament del sistema. En particular, el Model de Principis Bàsics no convencional ha generat resultats prometedors per a la degradació Fenton / foto-Fenton de diferents sistemes (compostos per un o més contaminants orgànics) per mitjà de paràmetres globals (com el Carboni Orgànic Total). Per tant, aquest enfocament ofereix un modelatge pràctic, independent del contaminant i vàlid per a mescles complexes de productes químics. Un cop proposats i validats, els models de procés es poden utilitzar sistemàticament per determinar maneres d'operació eficients o alternatives de disseny. En conseqüència, la tesi es va dirigir a dos casos d'interès pràctic: l'optimització d'una recepta de control i el disseny d'una xarxa de tractament. En el primer cas, es va proposar una estratègia d'optimització dinàmica per aprofitar els models cinètics disponibles i determinar el millor perfil de dosificació de peròxid d'hidrogen. Es van incloure objectius i limitacions econòmiques i ambientals per desenvolupar un problema d'optimització dinàmica que es va implementar en JModelica i es va resoldre utilitzant un mètode d'optimització simultània directa (IPOPT). Finalment, es va explorar la combinació de processos biològics convencionals, més barats, amb PAOs, més costosos. Es va proposar un model de Programació No Lineal Entera Mixta (MINLP) per a l'optimització d'una xarxa general d'aigües residuals, basat en una superestructura de dissenys alternatius, que es va implementar i resoldre en GAMS. La nova formulació inclou la relació BOD5 / COD, que descriu l'eficiència d'eliminació de BOD5 i COD d'un tractament per tal de modelar la variació de la biodegradabilitat dels influents. Aquesta nova formulació permet determinar l'abast dels tractaments de PAOs quan es combinen amb tractaments biològics, i aplana el camí per a models més complexos destinats a resoldre l'equilibri entre cost i eficiència del tractament.L'obiettivo della presente tesi è contribuire allo sviluppo di tecniche di modellizzazione sistematica finalizzate ad una gestione efficiente e sostenibile delle risorse idriche. L'obiettivo principale è contribuire allo studio dei POA (Processi di Ossidazione Avanzata). La tesi introduce metodi e strumenti dell’ingegneria dei processi chimici e propone modelli che possano servire per lo sviluppo di strategie efficaci di gestione dei POA nonché per l'integrazione di questi ultimi nelle reti di trattamento delle acque reflue. In primo luogo, sono stati studiati diversi POA. Nello specifico, sono stati studiati i processi di foto-ossidazione Fenton, photo-Fenton e VUV per il trattamento di soluzioni acquose di paracetamolo (PCT) la cui efficacia è stata confrontata adottando una serie di indicatori di prestazione (Key Performance Indicators, KPI). Tra i POA selezionati, la foto-ossidazione VUV e il processo photo-Fenton hanno prodotto i risultati più promettenti, consentendo di ottenere l'eliminazione totale del contaminante e un alto livello di mineralizzazione. La seconda parte della tesi si è concentrata sulla trasformazione dei "dati in conoscenza" proponendo modelli finalizzati alla descrizione dei processi Fenton / photo-Fenton e con l’obiettivo ultimo di adoperarli per ottimizzare le condizioni operative di questi ultimi. In particolare, sono stati proposti e validati due modelli cinetici che descrivono la degradazione dei composti organici per mezzo dei processi Fenton e photo-Fenton: • Un modello convenzionale, che include la modellizzazione della radiazione basata sull’ipotesi di radiazione lineare ed emissione sferica e isotropica, e in grado di prevedere la degradazione del PCT ad opera dei processi Fenton e photo-Fenton nonché il consumo di ossidante (H2O2); • Un modello non convenzionale, che propone un meccanismo generale di degradazione degli inquinanti basato sul numero di atomi di carbonio del contaminante da degradare a partire dal quale si propone un meccanismo di frammentazione di quest’ultimo con conseguente generazione di prodotti intermedi. Entrambi i modelli sono stati validati sperimentalmente e hanno mostrato prestazioni soddisfacenti. In particolare, il modello non convenzionale ha mostrato di poter rappresentare la degradazione Fenton e photo-Fenton di diversi composti organici attraverso l’utilizzo di un parametro globale (come il carbonio organico totale) e qindi di offrire una proposta di modellizzazione pratica indipendente dal contaminante e che può pertanto essere adottata in caso di miscele complesse di prodotti chimici. Una volta proposti e convalidati, i modelli di processo possono essere utilizzati sistematicamente per determinare modalità operative efficienti o alternative di progettazione. Di conseguenza, la tesi ha affrontato due casi di interesse pratico: l'ottimizzazione della ricetta di controllo del processo e la progettazione di una rete di trattamento di acque reflue. Nel primo caso è stata proposta una strategia di ottimizzazione dinamica per sfruttare i modelli cinetici disponibili e determinare il miglior profilo di dosaggio del perossido di idrogeno. Sono stati inclusi obiettivi e limiti economici e ambientali per sviluppare un problema di ottimizzazione dinamica implementato in JModelica che è stato risolto utilizzando un metodo di ottimizzazione simultanea diretta (IPOPT). Infine, è stata esplorata la combinazione di processi biologici convenzionali, più economici, con i PAO, più costosi. È stato proposto un modello MINLP (Nonlinear Mixed Integer Programming) per l'ottimizzazione di una rete di acque reflue, basato su una struttura attraverso la quale è possibile rappresentare scelte progettuali alternative, che è stato implementato e risolto in GAMS. La nuova formulazione include il rapporto BOD5 / COD, che descrive l'efficienza di eliminazione di BOD5 e COD di un trattamento al fine di modellare la variazione della biodegradabilità degli influenti. Questa nuova formulazione consente di determinare le diverse possibilità di combinazione dei PAO con i trattamenti biologici e apre la strada a modelli più complessi volti a risolvere l'equilibrio tra costo ed efficienza del trattamento

Advanced oxidation process models for optimisation and decision making support in water management

Aplicat embargament des de la data de defensa fins a l'abril de 2019The objective of this thesis is contributing to the development of a systematic modelling approach for a more efficient and sustainable water management. The main aim is introducing Chemical and Process System Engineering methods and tools to provide a contribution to the AOPs (Advanced Oxidation Processes) investigation field by proposing process models that can be exploited to progress towards efficient management strategies for practical AOPs operation and inclusion in wastewater treatment networks. First, different advanced oxidation processes, namely Fenton, photo-Fenton and VUV photo-oxidation, were investigated and compared for the treatment of paracetamol (PCT) aqueous solution, by evaluating a series of performance indicators. Among the selected AOPs, VUV photo-oxidation and photo-Fenton showed the most promising results. Both processes allowed attaining total removal of the target compound and high mineralization levels. The second and main part of the thesis was focused on transforming “data into knowledge” by proposing different modelling approaches. The modelling effort focused on Fenton/photo-Fenton processes that showed the need of improving operating conditions. Accordingly, two practical kinetic models for Fenton and photo-Fenton degradation of organic compounds have been proposed and validated: • A conventional First Principles Model, based on a line source radiation model with spherical and isotropic emission, developed for the prediction of Fenton and photo-Fenton degradation of PCT and the oxidant (H2O2) consumption; • A general non-conventional First Principles Model, based on a wide-ranging contaminant degradation mechanism considering a variable number of carbon atoms for the characterization of the intermediates. Both models were experimentally validated and showed that were able to satisfactorily reproduce the system behavior. Particularly, the non-conventional First Principles Model showed to be a successful modelling approach for the Fenton/photo-Fenton degradation of different wastewater systems composed by single or multiple organic contaminants by means of lumped parameters (e.g. Total Organic Carbon-TOC). Thus, the approach proved to offer practical characterization of complex mixtures of chemicals. Once process models are proposed and validated, they can be systematically exploited to determine efficient operation modes or design alternatives. Accordingly, the thesis addressed two cases of practical interest: the optimization of a control recipe and the design of a treatment network. Particularly, a dynamic optimization framework for taking advantage of available kinetic models and determining the best hydrogen peroxide dosage profile, was proposed. Economic and environmental objectives and constraints were included to develop a dynamic optimization problem that was implemented in JModelica and solved using a direct simultaneous optimization method (IPOPT). Finally, the combination of cheaper conventional biological processes with more expensive AOPs was explored. A Mixed-Integer Non Linear Programming (MINLP) model for the optimization of a general wastewater network was proposed based on a superstructure of alternative designs, which was implemented and solved in GAMS. The novel formulation includes the BOD5/COD ratio method, describing the removal efficiency of BOD5 and COD of a treatment for modelling the variation of the biodegradability of the influents. This novel formulation allows determining the extent of the AOP treatments when combined with biological treatments, and paves the way for more complex models aimed at solving the trade-off between cost and treatment efficiency.El objetivo de esta tesis es contribuir al desarrollo de técnicas de modelado sistemático para una gestión del agua eficiente y sostenible. El objetivo principal es contribuir a la investigación de los PAOs (Procesos Avanzados de Oxidación). La tesis introduce métodos y herramientas de Ingeniería de Procesos Químicos y propone modelos que puedan ser explotados para producir estrategias eficientes de gestión y operación de los PAOs, así como para la integración de estos PAOs en redes de tratamiento de aguas residuales. Primero, se investigaron diferentes PAOs. Se consideraron los procesos Fenton, foto-Fenton y la foto-oxidación VUV, y se compararon en el tratamiento de soluciones acuosas de paracetamol (PCT) adoptando una serie de indicadores de rendimiento (Key Performance Indicators, KPI). Entre los PAOs seleccionados, la foto-oxidación VUV y foto-Fenton producieron los resultados más prometedores, permitiendo lograr la eliminación total del contaminante y alto nivel de mineralización. La segunda parte de la tesis se centró en transformar ¿datos en conocimiento¿ mediante la propuesta de modelos para los procesos Fenton / photo-Fenton con el fin de mejorar las condiciones operativas de los mismos. En concreto se han propuesto y validado dos modelos cinéticos que describen la degradación de compuestos orgánicos por procesos Fenton y foto-Fenton: ¿ Un Modelo de Principios Básicos (F convencional, que incluye la modelización de la radiación lineal con emisión esférica e isotrópica, desarrollado para predecir la degradación Fenton y foto-Fenton del PCT y el consumo de oxidante (H2O2); ¿ Un Modelo de Principios Básicos no convencional, que propone un mecanismo de degradación de contaminantes general puesto que considera el número de átomos de carbono del contaminante como la variable de partida para la propuesta de fragmentación y consiguiente generación de intermedios. Ambos modelos se validaron experimentalmente y mostraron reproducir satisfactoriamente el comportamiento del sistema. En particular, el Modelo de Principios Básicos no convencional genero resultados prometedores para la degradación Fenton / foto-Fenton de diferentes sistemas (compuestos por uno o más contaminantes orgánicos) por medio de parámetros globales (como el Carbono Orgánico Total). Por tanto, este enfoque ofrece un modelado práctico independiente del contaminante y válido para mezclas complejas de productos químicos. Una vez propuestos y validados, los modelos de proceso se pueden utilizar sistemáticamente para determinar modos de operación eficientes o alternativas de diseño. En consecuencia, la tesis se dirigió a dos casos de interés práctico: la optimización de una receta de control y el diseño de una red de tratamiento. En el primer caso, se propuso una estrategia de optimización dinámica para aprovechar los modelos cinéticos disponibles y determinar el mejor perfil de dosificación de peróxido de hidrógeno. Se incluyeron objetivos y limitaciones económicas y ambientales para desarrollar un problema de optimización dinámica que se implementó en JModelica y se resolvió utilizando un método de optimización simultánea directa (IPOPT). Finalmente, se exploró la combinación de procesos biológicos convencionales, más baratos, con PAOs, más costosos. Se propuso un modelo de Programación no Lineal de Enteros Mixtos (MINLP) para la optimización de una red general de aguas residuales, basado en una superestructura de diseños alternativos, que se implementó y resolvió en GAMS. La nueva formulación incluye la relación BOD5 / COD, que describe la eficiencia de eliminación de BOD5 y COD de un tratamiento con el fin de modelar la variación de la biodegradabilidad de los influentes. Esta novedosa formulación permite determinar el alcance de los tratamientos de PAOs cuando se combinan con tratamientos biológicos, y allana el camino para modelos más complejos destinados a resolver el equilibrio entre coste y eficiencia del tratamiento.L'objectiu d'aquesta tesi és contribuir al desenvolupament de tècniques de modelatge sistemàtic per a una gestió de l'aigua eficient i sostenible. L'objectiu principal és contribuir a la investigació dels PAOs (Processos Avançats d'Oxidació). La tesi introdueix mètodes i eines d'Enginyeria de Processos Químics i proposa models que puguin ser explotats per produir estratègies eficients de gestió i operació dels PAOs, així com per a la integració d'aquests PAOs en xarxes de tractament d'aigües residuals. Primer, es van investigar diferents PAOs. Es van considerar els processos Fenton, foto-Fenton i la foto-oxidació VUV, i es van comparar en el tractament de solucions aquoses de paracetamol (PCT) adoptant una sèrie d'indicadors de rendiment (Key Performance Indicators, KPI). Entre els PAOs seleccionats, la foto-oxidació VUV i foto-Fenton van produir els resultats més prometedors, permetent aconseguir l'eliminació total del contaminant i alt nivell de mineralització. La segona part de la tesi es va centrar en transformar "dades en coneixement" mitjançant la proposta de models per als processos Fenton / photo-Fenton amb la finalitat de millorar les condicions operatives dels mateixos. En concret, s’han proposat i validat dos models cinètics que descriuen la degradació de compostos orgànics per processos Fenton i foto-Fenton: • Un model de Principis Bàsics convencional, que inclou la modelització de la radiació lineal amb emissió esfèrica i isotròpica, desenvolupat per predir la degradació Fenton i foto-Fenton del PCT i el consum d'oxidant (H2O2); • Un model de Principis Bàsics no convencional que proposa un mecanisme de degradació de contaminants general, ja que considera el nombre d'àtoms de carboni del contaminant com la variable de partida per a la proposta de fragmentació i consegüent generació d'intermedis. Tots dos models es van validar experimentalment i van mostrar la seva capacitat de reproduir satisfactòriament el comportament del sistema. En particular, el Model de Principis Bàsics no convencional ha generat resultats prometedors per a la degradació Fenton / foto-Fenton de diferents sistemes (compostos per un o més contaminants orgànics) per mitjà de paràmetres globals (com el Carboni Orgànic Total). Per tant, aquest enfocament ofereix un modelatge pràctic, independent del contaminant i vàlid per a mescles complexes de productes químics. Un cop proposats i validats, els models de procés es poden utilitzar sistemàticament per determinar maneres d'operació eficients o alternatives de disseny. En conseqüència, la tesi es va dirigir a dos casos d'interès pràctic: l'optimització d'una recepta de control i el disseny d'una xarxa de tractament. En el primer cas, es va proposar una estratègia d'optimització dinàmica per aprofitar els models cinètics disponibles i determinar el millor perfil de dosificació de peròxid d'hidrogen. Es van incloure objectius i limitacions econòmiques i ambientals per desenvolupar un problema d'optimització dinàmica que es va implementar en JModelica i es va resoldre utilitzant un mètode d'optimització simultània directa (IPOPT). Finalment, es va explorar la combinació de processos biològics convencionals, més barats, amb PAOs, més costosos. Es va proposar un model de Programació No Lineal Entera Mixta (MINLP) per a l'optimització d'una xarxa general d'aigües residuals, basat en una superestructura de dissenys alternatius, que es va implementar i resoldre en GAMS. La nova formulació inclou la relació BOD5 / COD, que descriu l'eficiència d'eliminació de BOD5 i COD d'un tractament per tal de modelar la variació de la biodegradabilitat dels influents. Aquesta nova formulació permet determinar l'abast dels tractaments de PAOs quan es combinen amb tractaments biològics, i aplana el camí per a models més complexos destinats a resoldre l'equilibri entre cost i eficiència del tractament.L'obiettivo della presente tesi è contribuire allo sviluppo di tecniche di modellizzazione sistematica finalizzate ad una gestione efficiente e sostenibile delle risorse idriche. L'obiettivo principale è contribuire allo studio dei POA (Processi di Ossidazione Avanzata). La tesi introduce metodi e strumenti dell’ingegneria dei processi chimici e propone modelli che possano servire per lo sviluppo di strategie efficaci di gestione dei POA nonché per l'integrazione di questi ultimi nelle reti di trattamento delle acque reflue. In primo luogo, sono stati studiati diversi POA. Nello specifico, sono stati studiati i processi di foto-ossidazione Fenton, photo-Fenton e VUV per il trattamento di soluzioni acquose di paracetamolo (PCT) la cui efficacia è stata confrontata adottando una serie di indicatori di prestazione (Key Performance Indicators, KPI). Tra i POA selezionati, la foto-ossidazione VUV e il processo photo-Fenton hanno prodotto i risultati più promettenti, consentendo di ottenere l'eliminazione totale del contaminante e un alto livello di mineralizzazione. La seconda parte della tesi si è concentrata sulla trasformazione dei "dati in conoscenza" proponendo modelli finalizzati alla descrizione dei processi Fenton / photo-Fenton e con l’obiettivo ultimo di adoperarli per ottimizzare le condizioni operative di questi ultimi. In particolare, sono stati proposti e validati due modelli cinetici che descrivono la degradazione dei composti organici per mezzo dei processi Fenton e photo-Fenton: • Un modello convenzionale, che include la modellizzazione della radiazione basata sull’ipotesi di radiazione lineare ed emissione sferica e isotropica, e in grado di prevedere la degradazione del PCT ad opera dei processi Fenton e photo-Fenton nonché il consumo di ossidante (H2O2); • Un modello non convenzionale, che propone un meccanismo generale di degradazione degli inquinanti basato sul numero di atomi di carbonio del contaminante da degradare a partire dal quale si propone un meccanismo di frammentazione di quest’ultimo con conseguente generazione di prodotti intermedi. Entrambi i modelli sono stati validati sperimentalmente e hanno mostrato prestazioni soddisfacenti. In particolare, il modello non convenzionale ha mostrato di poter rappresentare la degradazione Fenton e photo-Fenton di diversi composti organici attraverso l’utilizzo di un parametro globale (come il carbonio organico totale) e qindi di offrire una proposta di modellizzazione pratica indipendente dal contaminante e che può pertanto essere adottata in caso di miscele complesse di prodotti chimici. Una volta proposti e convalidati, i modelli di processo possono essere utilizzati sistematicamente per determinare modalità operative efficienti o alternative di progettazione. Di conseguenza, la tesi ha affrontato due casi di interesse pratico: l'ottimizzazione della ricetta di controllo del processo e la progettazione di una rete di trattamento di acque reflue. Nel primo caso è stata proposta una strategia di ottimizzazione dinamica per sfruttare i modelli cinetici disponibili e determinare il miglior profilo di dosaggio del perossido di idrogeno. Sono stati inclusi obiettivi e limiti economici e ambientali per sviluppare un problema di ottimizzazione dinamica implementato in JModelica che è stato risolto utilizzando un metodo di ottimizzazione simultanea diretta (IPOPT). Infine, è stata esplorata la combinazione di processi biologici convenzionali, più economici, con i PAO, più costosi. È stato proposto un modello MINLP (Nonlinear Mixed Integer Programming) per l'ottimizzazione di una rete di acque reflue, basato su una struttura attraverso la quale è possibile rappresentare scelte progettuali alternative, che è stato implementato e risolto in GAMS. La nuova formulazione include il rapporto BOD5 / COD, che descrive l'efficienza di eliminazione di BOD5 e COD di un trattamento al fine di modellare la variazione della biodegradabilità degli influenti. Questa nuova formulazione consente di determinare le diverse possibilità di combinazione dei PAO con i trattamenti biologici e apre la strada a modelli più complessi volti a risolvere l'equilibrio tra costo ed efficienza del trattamento.Postprint (published version