Aerobic granular sludge has been regarded as a promising alternative to the conventional activated sludge which has been used for a century in that granular sludge offers advantages in high biomass retention, fast sludge-water separation, and small footprint requirement. However, this technology has been rarely applied in continuous flow reactors (CFRs) which are the most common type of bioreactors used in water resource recovery facilities across the world. Hence, the overarching goal of this study is to provide advanced understanding of biogranulation mechanism to enable industrial application of this technology. The lack of long-term stability study in CFRs has restricted its full-scale acceptability. The high settling velocity-based selection pressure has been regarded as the ultimate driving force towards biogranulation in sequential batch reactors (SBRs). In this study, this physical selection pressure was firstly weakened and then eliminated in CFRs to investigate its role in maintaining the long-term structural stability of aerobic granules. Given the fact that implementing settling velocity-based selection pressure only can cultivate biogranules in SBRs but not in completely stirred tank reactors (CSTRs), the essential role of feast/famine conditions was investigated. Seventeen sets of data collected from both literature and this study were analyzed to develop a general understanding of the granulation mechanisms. The outcome indicated that granulation is more sensitive to the feast/famine conditions than to the settling velocity-based selection pressure. The theory was tested in a CFR with 10-CSTR chambers connected in series to provide feast/famine conditions followed by a physical selector separating the slow-settling bioflocs and fast-settling biogranules into feast and famine zones, respectively. Along with successful biogranulation, the startup performance interruption problem inherent in SBRs was also resolved in this innovative design because the sludge loss due to physical washout selection was mitigated by returning bioflocs to the famine zone. Then, a cost-effective engineering strategy was put forward to promote the full-scale application of this advanced technology. With this generalized biogranulation theory, pure culture biogranules with desired functions for high value-added bioproducts were also investigated and achieved for the first time in this study, which paves a new avenue to harnessing granulation technology for intensifying waste valorization bioprocesses. / Doctor of Philosophy / Nowadays, the rapid population growth and unprecedented urbanization are overloading the capacity of many wastewater resource recovery facilities (WRRFs). Therefore, there is a need to develop a cost-effective strategy to upgrade the treatment capacity of existing WRRFs without incurring major capital investment. Because conventional activated sludge comes with loose structure and poor settleability, replacing them with dense aerobic granular sludge offers the opportunity to intensify the capacity of existing WRRF tankage and clarifiers through better retention of high bacterial mass that offers not only a fast pollutant removal rate but also a high water-solids separation rate. The aerobic granulation technology turns traditional activated sludge into granular sludge by inducing microbial cell-to-cell co-aggregation. Although this technology has been developed for more than 20 years, its application in full-scale WRRFs is still limited because majority of WRRFs are constructed with continuous flow reactors in which the aerobic granulation mechanism largely remains unknown. Besides, the long-term stability of aerobic granules in continuous flow reactors also remain unstudied, further constraining the full-scale application of the technology. The sensitivity of aerobic granulation to physical selection and biological selection was analyzed in this study. The results concluded that aerobic granulation is more sensitive to the latter but not to the former. Subsequently, this theory was tested in a novel bioreactor setup that creates feast/famine conditions for biological selection. A physical selector was installed at the end of the bioreactor to separate and return the fast- and slow- settling bioparticles to the feast and famine zones, respectively. This unique reactor design and operational strategy provided an economical approach to retrofitting current WRRFs for achieving treatment capacity upgrading without major infrastructure alternation. It also protected the bioreactor startup performance by enhancing the stability of WRRFs in the future application. Last but not least, this updated understanding of aerobic granulation theory was for the first time extrapolated to and verified with the formation of pure culture biogranules harnessed in this study for value-added bioproduct valorization from waste materials.

Novel settling characteristic metrics were developed based on the fundamental mechanisms of coagulation, flocculation, and settling. The settling metrics determined parameters that are essential in monitoring and optimizing the activated sludge process without the need for expensive or specialized equipment. Current settling characteristic measurements that don't require specialized instruments such as sludge volume index (SVI) or initial settling velocity (ISV), have no fundamental basis in solid-liquid separation and only indicate whether settling is good or bad without providing information as to limitations present in a sludge matrix. Furthermore, the emergence of aerobic granulation as a potential pathway to mitigate solid-separation issues further stresses the need for new settling characteristic metrics to enable integration of the new technology with the current infrastructure. The granule or intrinsic aggregate fraction in different types was of sludge was quantified by simulating different surface overflow rates (SOR). The technique named Intrinsic Settling Classes (ISC) was able to separate granules and floc by simulating high SOR values due to the lack of a flocculation time needed for granules. The method had to be performed in a discrete settling environment to characterize a range of flocculation behavior and was able to classify the granular portion of five different types of sludge. ISC was proven to accurately (±2%) determine the granule fraction and discrete particle distribution. The major significance of the test is its ability to show if a system is producing particles that will eventually grow to become granules. This methodology proved to be very valuable in obtaining information as to the granular fraction of sludge and the granular production of a system. Flocculent settling (stokesian) was found to be predominant within ideally operating clarifiers, and the shift to 'slower' hindered settling (non-stokesian) causes both failure and poor effluent quality. Therefore, a new metric for settling characteristics was developed and classified as Limit of Stokesian Settling (LOSS). The technique consisted of determining the total suspended solids (TSS) concentration at which mixed liquor settling characteristics transition from stokesian to non–stokesian settling. An image analytical technique was developed with the aid of MATLAB to identify this transition. The MATLAB tool analyzed RGB images from video, and identified the presence of an interface by a dramatic shift in the Red indices. LOSS data for Secondary activated-sludge systems were analyzed for a period of 60 days at the Blue Plains Advanced Wastewater Treatment Plant. LOSS numbers collected experimentally were validated with the Takacs et al. (1991) settling model. When compared to flux curves with small changes in the sludge concentration matrix, LOSS was found to be faster at characterizing the hindered settling velocity and was less erratic. Simple batch experiments based on the critical settling velocity (CSV) selection were used as the basis for the development of two novel parameters: threshold of flocculation/flocculation limitation (TOF/a), and floc strength. TOF quantified the minimum solids concentration needed to form large flocs and was directly linked to collision efficiency. In hybrid systems, an exponential fitting on a CSV matrix was proposed to quantify the collision efficiency of flocs (a). Shear studies were conducted to quantify floc strength. The methods were applied to a wide spectrum of sludge types to show the broad applicability and sensitivity of the novel methods. Three different activated sludge systems from the Blue Plains AWWTP were monitored for a 1 year period to explore the relationship between effluent suspended solids (ESS) and activated sludge settling and flocculation behavior. Novel metrics based on the transitional solids concentration (TOF, and LOSS) were also collected weekly. A pilot clarifier and settling column were run and filmed to determine floc morphological properties. SVI was found to lose sensitivity (r < 0.20) when characterizing ISV above a hindered settling rate of 3 m h-1. ISV and LOSS had a strong correlation (r = 0.71), but ISV was subject to change, depending on the solids concentration. Two sludge matrix limitations influencing ESS were characterized by transition concentrations; pinpoint floc formation, and loose floc formation. Pinpoint flocs had TOF values above 400 mg TSS L-1; loose floc formation sludge had TOF and LOSS values below 400 mg TSS L-1 and 900 mg TSS L-1, respectively. TOF was found to correlate with the particle size distribution while LOSS correlated to the settling velocity distribution. The use of both TOF and LOSS is a quick and effective way to characterize limitations affecting ESS. / Ph. D.

Attached growth biological processes offer advantages over traditional water purification technologies through high biomass retention, easy sludge-water separation, multiple multispecies synergies in proximity, resilience to shock loading, low space requirements, and reactor operational flexibility. Traditionally, attached growth refers to biofilms that require abiotic carrying media for bacteria to attach and grow on. While biofilms have been broadly applied in wastewater treatment, its potential for potable reuse or stormwater treatment has not been well studied. The treatment trains of pre-ozonation followed by biologically active filtration (ozone- BAF) is an advanced biofilm technology for potable reuse that can generate high-quality potable water at reduced energy and chemical demands by removing pollutant through three different pathways: oxidation, adsorption, and biodegradation. However, these pathways can result in both desirable and undesirable effects, and the mechanism behind it is still unclear. To understand the mechanisms of various pollutant removal, parallel performance comparisons of ozone-BAF treatment trains with spent and regenerated granular activated carbon (GAC), along with a range of pre-oxidant ozone doses were performed. Another common issue of BAF is the headloss buildup during its operation, which has become a significant energy and maintenance burden at many utilities. Thus, a mathematical model was developed to predict BAF headloss buildup in response to organic removal and nitrification. For stormwater treatment, the feasibility of using biofilms for stormwater biological nitrogen removal (BNR) is still largely unknown, as very limited research effort has been dedicated to this aspect. Thus, a mathematical model was developed to evaluate the potential of using BNR techniques for stormwater nitrogen removal. Aerobic granules are an even more advanced attached growth process, which eliminates the need for abiotic carrying media. So far, aerobic granular sludge is only formed in sequential batch reactors but not in a continuous flow system. Therefore, continuous flow aerobic granulation from traditional activated sludge was investigated and, for the first time, successfully achieved in continuous flow plug-flow bioreactors fed with real municipal wastewater. Besides, the role and critical value of an essential operational parameter, feast/famine ratio, for continuous flow aerobic granulation were determined. / Doctor of Philosophy / Water scarcity and increasing water demand caused by urban population growth and climate change is a reality throughout the world. Thus, process intensification of the current water and wastewater technologies is gaining increasing attention globally. Comparing to traditional water purification technologies, attached growth biological processes offers advantages such as high biomass retention, easy sludge-water separation, multiple multispecies synergies in proximity, resilience to shock loading, small footprint requirement, and reactor operational flexibility. Traditionally, attached growth refers to biofilms that require abiotic carrying media for bacteria to attach and grow on. While biofilms have been broadly applied in wastewater treatment, its potential for potable reuse or stormwater treatment has not been well studied. For potable reuse, the treatment trains of pre-ozonation followed by biologically active filtration (ozone-BAF) is an advanced biofilm technology that can generate high-quality potable water at reduced energy and chemical demands by removing pollutant through different pathways. However, the mechanism behind it is still unclear. To understand the mechanisms of various pollutant removal, parallel performance comparisons of ozone-BAF treatment trains operated with different operational conditions were performed in this dissertation. Another common issue of BAF is the headloss buildup during its operation, which has become a significant energy and maintenance burden at many utilities. Thus, a mathematical model was developed to predict the headloss buildup during BAF operation. For stormwater treatment, the feasibility of using biofilms for stormwater biological nitrogen removal (BNR) is still largely unknown, as very limited research effort has been dedicated to this aspect. Thus, a mathematical model was developed to evaluate the potential of using BNR technique for stormwater. Aerobic granules are an even more advanced attached growth process. However, aerobic granular sludge is so far only formed in sequential batch reactors which are incompatible with the continuous flow nature of most wastewater treatment plants. Therefore, aerobic granulation from traditional activated sludge was investigated and, for the first time, successfully achieved in continuous flow plug-flow bioreactors fed with real municipal wastewater. Besides, the role of an essential operational parameter, feast/famine ratio, for continuous flow aerobic granulation was determined.

Twin screw wet granulation (TSG) has been studied as a continuous manufacturing alternative to batch granulation for nearly twenty years. One of the main differences between batch granulation and TSG lies in the exiting granules being presented as a bimodal particle size distribution (PSD) in the latter case. Current process analytical technologies (PAT) can monitor a monomodal distribution well but there have been no techniques disclosed in the public domain so far that can accurately monitor this unusually shaped PSD. Acoustic emissions (AE) has been identified as a PAT of interest due to its ease of use (lack of calibration), low cost, and non-invasive design relative to other PATs used for monitoring PSDs. Hence the goal of this thesis was to develop AE as a process analytical technology (PAT) capable of estimating the full distribution of produced granules by TSG in real time. The first research study of this thesis focused on the development of the new technology. The AE PAT consisted of an acoustic sensor, an impact plate, and software to convert the time-domain signal of particle collisions into a time-averaged frequency-domain spectrum to be subsequently used to estimate a weight-averaged particle size distribution. A novel and much required addition to the PAT was inclusion of a digital filter based on particle mechanics parameters to overcome auditory masking which hindered accurately converting the cumulative sounds of impact into a PSD. The PAT was tested in this study with granulated lactose monohydrate and with the new digital filter, obtaining a maximum error of 1 wt% across all particle sizes tested. In the second research study, as more formulations commonly used in the industry were tested, the filter proved unable by itself to account for the differences in impact mechanics and therefore needed to be modified to incorporate the more inelastic behaviour now being seen. Two micromechanical models were explored, and the Walton-and-Braun model was found to be the most suitable for the AE PAT – reducing its error from 8 wt% down to 2.75 wt% across four formulations producing coefficients of restitution from 0.79 to 0.24. In the last research study in this thesis, the now-functional inline PAT was used to reveal mechanistic details related to the transition state in granulation as a TSG starts up, to improve the field’s understanding of the granulation mechanism. The technique was able to estimate the PSD over much shorter periods of material collection compared to sieving, allowing the evolution of the PSD as a function of time to be examined for varying degrees of fill (DF) and liquid-to-solids ratios. It was determined that the time to steady state, at both DF tested, occurred at approximately 5 times the mean residence time of the process by both PAT and sieving analyses. Particle sizes between 102-2230 μm were then tracked as a function of time below 120 s and variations of granule growth were seen for each degree of fill which added to the understanding of the granulation mechanism. This PAT shows great promise as a monitoring tool to implement quality by design principles for TSG in pharmaceutical manufacturing. / Thesis / Doctor of Philosophy (PhD)

La fabrication de comprimés pharmaceutiques par granulation humide a typiquement recours aux lits fluidisés pour le séchage des particules. Encouragée par les agences réglementaires, l'industrie a entamé une migration vers la production continue et automatisée, mais les procédés discontinus (batch) opérés sans rétroaction, excepté un contrôle qualité en fin de cycle, demeurent largement majoritaires dans le secteur. Dans le cas des séchoirs à lit fluidisé, cette approche occasionne plusieurs complications comme le sous-séchage, le surséchage et la surchauffe des granules thermosensibles, qui peuvent conduire au rejet du lot. Toutefois, la commande avancée et la production en continu peuvent réduire les problèmes d'opération. Ce projet de recherche concerne donc l'automatisation du séchage par lit fluidisé ou, plus spécifiquement, sa modélisation, sa commande et son observation. La conception et la comparaison de diverses stratégies d'estimation et de contrôle nécessitent d'abord un modèle mathématique représentatif du procédé. Pour y parvenir, une identification « boite grise » estime les paramètres empiriques d'une description phénoménologique à deux phases du lit fluidisé à partir de données expérimentales et un second lot de données valide les simulations qui en résultent. Cet ouvrage évalue ensuite la commande prédictive linéaire, non linéaire et économique sur le simulateur calibré. L'étude explore aussi les filtres de Kalman standard et non parfumé, ainsi que l'estimateur à fenêtre glissante, comme capteur virtuel de teneur en eau des particules, le principal indicateur de qualité au séchage. La première partie de cette thèse se concentre sur les séchoirs verticaux discontinus, et la deuxième, sur un nouveau prototype de réacteur horizontal entièrement continu. Les résultats de cette recherche confirment les avantages indéniables de ces technologies, soit un contrôle serré de la qualité du produit, et une diminution des coûts et de l'empreinte environnementale des opérations. / Manufacturing pharmaceutical tablets through wet granulation typically relies on fluidized bed drying for the particles. Advocated by regulatory agencies, the industry initiated a paradigm shift towards fully continuous and automated production, but batch processes operated without feedback, except a quality control at the end of the cycle, still prevail in the sector. For the case of fluidized bed dryers, this approach results in several issues like under drying, over drying, overheating of thermosensitive granules, that can lead to the rejection of the batch. However, advanced control and continuous processing can reduce the operational hurdles. This research project investigates the automation of fluidized bed drying or, more specifically, its modeling, control and observation. The design and comparison of various estimation and feedback strategies first require a representative mathematical model of the process. For this, a grey-box identification estimates the empirical parameters of a two-phase fluidized bed description from experimental data, and a second dataset validates the resulting simulations. This work then investigates linear, nonlinear, and economic model predictive control on the calibrated simulator. The study also explores the standard and unscented Kalman filter, and the moving-horizon estimator, as soft sensors for the particle moisture content, a critical quality attribute at drying. The first part of this thesis focuses on vertical batch dryers, and the second one, on a new prototype of a fully continuous horizontal reactor. The results of this research confirm the undeniable advantages of those technologies, namely a tight control of the product quality, and reductions in the costs and the environmental footprint of the operations.

No description available.

Im Rahmen der vorliegenden Arbeit wird die Kompaktier-Granulierung von Kalisalzen zur Herstellung von Düngemittelgranulat experimentell untersucht und ein Modellansatz zur Beschreibung von derartigen Kreisläufen abgeleitet. Bei der Kompaktier-Granulierung wird fein-disperses Kalisalz mit Hilfe von Walzenpressen zu sogenannten Schülpen verpresst. Diese werden durch nachfolgende Zerkleinerung und Klassierung zu Düngemittelgranulat (enge Partikelgrößenklasse, wie beispielsweise 2 – 4 mm) verarbeitet. Basierend auf halb-industriellen Kreisläufen werden im vorliegenden Beitrag wesentliche Prozesswechselwirkungen zwischen Kompaktierung, Zerkleinerung und Klassierung ausgearbeitet. Detailuntersuchungen zeigen, dass sich insbesondere die Schülpenfestigkeiten wie auch die schüttgutmechanischen Eigenschaften des Pressenaufgabegutes im Kreislaufbetrieb ändern. Darauf aufbauend wird ein Modellansatz abgeleitet der die Abschätzung des Kreislaufbetriebs erlaubt.

L'objet du projet CALAS est l'étude de la supergranulation solaire, structure à grande échelle de la photosphère. L'origine de la supergranulation est encore controversée et nécessite des observations à très haute résolution spatiale sur un grand champ de vue. Le projet CALAS répond à ces exigences en proposant de concevoir une caméra rapide combinant grand champ et haute résolution, installée à la Lunette Jean Rösch, réfracteur de 50 cm de diamètre situé au Pic du Midi. Cette caméra utilise des capteurs CMOS (Complementary Metal Oxide Semi-conductor) dont les avantages sont notamment la rapidité de lecture, le coût réduit et de grands formats disponibles.<br />Nous avons conçu une chaîne d'acquisition complète, comprenant la caméra et son électronique de commande, une électronique de lecture couplée à un logiciel de prise de vues, et un système de stockage des données.<br />Le projet a également consisté à concevoir un banc optique sur deux voies permettant l'observation de la surface solaire en mode imagerie mais aussi en mode Doppler et magnétographie, par l'utilisation d'un filtre magnéto-optique. Le travail a également nécessité d'étudier l'intégration de CALAS au sein de la Lunette Jean Rösch, en participant à la jouvence de cet instrument.<br />Enfin, au cours de ce projet, outre de nombreuses missions d'observation à la Lunette Jean Rösch, j'ai également été amené à participer à une campagne internationale d'observations coordonnées consacrée à l'étude des mouvements de la photosphère dans l'environnement de filaments. A l'issue de cette thèse, les premières observations à grand champ et haute résolution de la photosphère solaire ont été réalisées à la LJR, et leur excellente qualité se révèle déjà tout à fait prometteuse pour la suite de l'exploitation scientifique.

In this thesis, a thorough study of the batch top-spray fluidized bed granulation was carried out including experimental study, population balance model (PBM), computational fluid dynamic (CFD) study and control strategy development. For the experimental study, the influence variables of pulsed frequency, binder spray rate and atomization pressure of a batch top-spray fluidized bed granulation process were studied using the Box-Behnken experimental design method. Different mathematical models were developed to predict the mean size of granules, yield, relative width of granule distribution, Hausner ratio and final granule moisture content. Validation experiments have shown the reliability and effectiveness of using the Box-Behnken experimental design method to study a fluidized bed granulation process. The one-dimensional population balance models (ODPBMs) have been developed to model a pulsed top-spray fluidized bed granulation, linking the operating factors of the pulsed frequency, the binder spray rate, and atomization air pressure with the granule properties to predict granule growth behavior at different operating conditions. A multi-stage open optimal control strategy based on the developed ODPBMs was proposed to reduce the model and process mismatch through adjusting the trajectory of the evolution of the granule size distribution at predefined sample intervals. The effectiveness of the proposed modeling and multi-stage open optimal control strategy has been validated by experimental and simulation tests. In addition, an Eulerian-Eulerian two-fluid model (EETFM) was developed to describe the gas-particle two-phase flow in the fluidized bed granulator. By computational fluid dynamic analysis, it has been proven that the fluidized bed granulation system is not homogeneous, based on which a two-compartmental population balance model (TCPBM) was developed to describe the particle growth in the fluidized bed granulation. Validation experiments have shown the effectiveness and superior accuracy of the TCPBM comparing with the ODPBM in predicting the final particle size distribution.

Depuis une dizaine d'années, les procédés de granulation aérobie sont apparus comme une technologie prometteuse pour le traitement des effluents fortement chargés en azote, phosphore et carbone, tels que ceux issus de l'agro-industrie. La complexité microbienne de ces granules et les mécanismes qui leur donnent des propriétés exceptionnelles de décantation et de cohésion, constituent encore des axes de recherche importants. Dans cette thèse, le travail s'est axé sur un mécanisme encore non étudié : les processus de précipitation des phosphates au cœur des granules microbiennes. Différentes techniques d'analyses spectrales, parfois adaptés pour la première fois à ce type de systèmes, comme la spectroscopie Raman, ont permis de caractériser la nature de ces minéraux formés au cœur des granules. L'analyse menée sur des réacteurs de laboratoires a démontré la présence des phosphates de calcium sous forme d'hydroxyapatite [Ca5(PO4)3(OH)]. Cette précipitation est potentiellement induite par les variations locales de pH et de sursaturation provoqués par les réactions microbiennes à l'intérieur des granules. L'étude des phénomènes de biominéralisation à été étendu aux granules anaérobies issus des réacteurs de type UASB de l'industrie laitière. Un modèle physico-chimique sur les processus de précipitation sous forme matriciel sur AQUASIM®, couplé avec des bases de calcul de sursaturation (PHREEQC®), ont permis d'avancer des hypothèses sur les mécanismes influençant ces processus de biominéralisation, tels que la formation d'un précurseur amorphe de l'hydroxyapatite (ACP), ainsi que d'identifier les constantes de précipitation thermodynamiques (pKsp|20ºC=28.07±0.58) et cinétiques dans différentes conditions opératoires. Grâce au suivi d'un système biologique GSBR (Granular Sludge Sequenced Batch Reactor) pendant plus de 900 jours, la contribution de ce phénomène aux processus de déphosphatation a été estimé (46% dans les conditions testées). L'utilisation de ce processus pour immobiliser efficacement le phosphore et apporter des propriétés physiques stables aux granules a été également discutée. Une évaluation des performances et de la stabilité du réacteur à été mis en œuvre en alternant des cycles anoxies/aérobies ou anaérobies/aérobies vis-à-vis d'une future application industrielle. L'induction locale de la précipitation par les variations de pH et par le relargage des phosphates par les réactions microbiennes, nécessite une modélisation appropriée, qui a été également initiée dans cette thèse / Over the last decade, aerobic granulation processes have araised as a promising technology for treating wastewater effluents containing high nitrogen, phosphorus and carbon concentrations. The microbial complexity of granules and the mechanisms by which they acquire excellent settleability properties, still constitute important research goals to investigate. This thesis is focused on a mechanism that has been little addressed in literature, that is, phosphate precipitation in the core of aerobic granules. Different analytical techniques, sometimes adapted for the first time to this type of systems, like Raman spectroscopy, have let an exhaustive characterization of biominerals in the core of granules. Analyses performed on aerobic granules grown with synthetic fed in a lab-scale SBR (Sequential Batch Reactor), revealed a calcium phosphate core made of hydroxyapatite [Ca5(PO4)3(OH)]. This precipitation phenomenon is induced by local pH and supersaturation gradients issued of biological reactions inside granules. The study of the biomineralization phenomenon has been extended into anaerobic granules coming from UASB reactors at different cheese wastewater treatment plants. A physico-chemical model has been described in a form of matrix with AQUASIM® software, and coupled with a thermodynamic database (PHREEQC®), in an attempt to hypothesize the mechanisms that influence the biomineralization phenomena. It has been proposed the formation of an amorphous precursor (ACP) prior hydroxyapatite precipitation in the core of granules, suggesting the thermodynamic constant (pKsp|20ºC=28.07±0.58) and kinetic constants at different operating conditions. It has been also estimated the contribution of the biomineralization to the overall phosphorus removal process (up to 46% at the operating conditions tested), thanks to the development and study of a GSBR (Granular Sludge Batch Reactor) in labscale, for more than 900 days. The fate of the biomineralization process in granules, regarding the contribution to their stabilization and physical properties, has been also dealt in this thesis. The reactor stability and performances have been assessed by alternating anoxic/aerobic and anaerobic/aerobic cycles, in sights of a future industrial application. The induction of precipitation by local variation of pH and supersaturation issued of biological reactions has been here introduced, although it will need further investigation