Submeteu-se um Reator Anaeróbio Horizontal de Leito Fixo (RAHLF) de bancada, ao aumento progressivo da concentração de matéria orgânica afluente, e a cargas de choque orgânicas, com o objetivo de verificar-se seu desempenho e estabilidade operacional. O RAHLF foi construído com um tubo de boro-silicato de 100 cm de comprimento, 5,0 cm de diâmetro e 1995 ml de volume total e preenchido com lodo anaeróbio imobilizado em matrizes de espuma de poliuretano. O reator foi alimentado, inicialmente, com substrato composto principalmente de carboidratos em concentrações, expressas como Demanda Química de Oxigênio (DQO) de, aproximadamente, 200, 1000 e 2000 mg/l. Posteriormente, os carboidratos foram substituídos por metanol e ácidos voláteis, em concentrações totais, aproximadas, de 2000, 3000, 4000 e 5000 mg DQO/l. Atingido o estado estacionário para cada condição operacional, foram aplicadas cargas de choque, aumentando-se em três vezes o valor da DQO afluente, durante período equivalente ao tempo de detenção hidráulica (sete horas). O sistema apresentou problemas operacionais durante os experimentos com carboidratos, quando submetido a 2000 mg DQO/l, correspondente à taxa volumétrica de carregamento orgânico de 8,77 KgDQO/m3.d. Não foi verificado qualquer problema operacional durante os experimentos com substrato contendo metanol e ácidos voláteis, e o reator apresentou eficiência de remoção de DQO superior a 90%. Para o experimento com DQO afluente igual a 2000 mg/l, os parâmetros cinéticos foram estimados a partir de modelo cinético de 1ª ordem, obtendo-se valor de k1 igual a 0,049 h-1, nos demais experimentos ajustou-se modelo cinético de 2ª ordem com valor médio de k2 equivalente a 2,0 x 10-4 l/mg.h Foram aplicadas cargas de choque orgânicas equivalentes a, aproximadamente, 17; 27; 40 e 47 kgDQO/m3.d. Os efeitos das sobrecargas orgânicas no reator foram transientes em todos os casos, tendo o reator voltado à condição inicial em, no máximo, 15 horas após o início das sobrecargas. / A Horizontal flow Anaerobic lmmobilized Sludge Reactor (HAIS) was subjected to progressively increasing concentrations of organic effluent material and to organic shock loads with the purpose of investigating its operational performance and stability. The HAIS, consisting of a 100 cm long, 5 cm diameter borosilicate tube with a total volume capacity of 1995 mL, was filled with anaerobic sludge immobilized in foam and polyurethane matrixes. The reactor was initially fed with a substrate composed mainly of carbohydrates in concentrations, expressed as Chemical Oxygen Demand (COD), of approximately 200, 1000 and 2000 mg/L. These carbohydrates were later replaced by methanol and volatile acids in total concentrations of 2000, 3000, 4000 and 5000 mg COD/L. Shock loads were applied after each operational condition became stationary, with the effluent COD tripled for a period equivalent to the hydraulic detention time (seven hours). The system presented operational problems during the experiments with carbohydrates when subjected to 2000 mg DQO/l, which corresponded to a volumetric organic load index of 8,77 Kg COD/m3.d. No operational problems were detected during the experiments with substrates containing methanol and volatile acids, and the reactor presented a COD removal efficiency of over 90%. The kinetic parameters for the COD effluent with 2000 mg/L were estimated based on a first arder kinetic model, which resulted in a k1 value of 0,049 h-1, while a kinetic model of the second order was used for the remaining experiments, with a mean value of k2 equivalent to 2,0 x 10-4 L/mg.h. Organic shock loads of approximately 17; 27; 40 and 47 kg COD/m3.d were applied. The effects of the organic overloads on the reactor were transient in every case, with the reactor returning to its initial condition at the most 15 hours after the beginning of the overloads.

O objetivo deste trabalho foi avaliar a possibilidade de acelerar o processo de digestão anaeróbia da fração orgânica de resíduos sólidos urbanos domésticos em sistemas de duas fases, com taxas crescentes de recirculação de lixiviado, variando a taxa de recirculação de lixiviado em função da concentração de ácidos voláteis. Para tanto, foram operados dois sistemas de reatores, cada um composto por um reator de sólidos, que continha o resíduo sólido a ser tratado e um filtro anaeróbio de fluxo ascendente, que tratava o lixiviado do primeiro, antes que esse lixiviado fosse recirculado ao reator de sólidos. Um dos sistemas teve sua taxa de recirculação aumentada a intervalos constantes, enquanto que no outro o momento do aumento da taxa foi função da concentração de ácido propiônico no sistema. O trabalho teve ainda dois objetivos secundários: avaliar a validade de comparar os resultados dos dois sistemas, operados em paralelo, em função das características dos resíduos sólidos e dos procedimentos adotados para coleta e preparação do substrato e para o carregamento dos reatores; e avaliou-se a possibilidade de utilizar filtros anaeróbios para recuperar reatores acidificados. Durante o desenvolvimento do experimento, foram monitorados os seguintes parâmetros: DQO (não filtrada e filtrada), pH, alcalinidade, série de sólidos, nitrogênio total Kjeldahl, nitrogênio amoniacal, ácidos voláteis e composição do biogás. Foram realizados ainda exames qualitativos da microbiota que se desenvolveu nos reatores, através de microscopia óptica de fluorescência e contraste de fase. Os resultados obtidos permitiram concluir que: a) os procedimentos testados para o carregamento dos reatores de sólidos permitiram a comparação de resultados entre os sistemas; b) os filtros foram capazes de recuperar reatores acidificados; e c) a utilização da concentração de ácido propiônico para determinar o momento da variação da taxa de recirculação permitiu acelerar o processo, embora de forma restrita, para a escala de reatores utilizada. / The purpose of this dissertation was to evaluate the possibility of accelerating the process of anaerobic digestion of the organic fraction of domestic municipal solid waste, in two-stage systems, with increasing leachate recirculation rate, through the use of volatile acids as determining parameter of the moment in which the rate must be varied. To do so, two systems of reactors were operated, each being composed by a solids reactor, which contained the solid waste intended to be treated, and an upflow anaerobic filter, which treated the leachate of the first reactor, before recirculation. One of the systems had its recirculation rate increased at constant spells of time, while, in the other system, the moment of the increase in the recirculation rate was a function of the concentration of propionic acid in the system. This study had yet two secondary purposes: evaluating the validity of comparing the results from the two systems of reactors, operated in parallel, in view of the characteristics of solid waste and the adopted procedures for collecting and preparing the substrate, as well as for the loading of reactors; and evaluating the possibility of using anaerobic filters to recover acidified reactors. The following parameters were measured during the process: COD (filtered and non-filtered), pH, alkalinity, solids, Kjeldahl nitrogen, ammonium nitrogen, volatile acids and biogas composition. The development of microorganisms in the reactors was observed qualitatively, using optical microscopy. It was possible to reach the following conclusions: a) the tested procedures allow the comparison of results between the systems; b) the filters are capable of recovering acidified reactors; and c) the employment of the concentration of propionic acid to determine the moment of increase of leachate recirculation rate is capable of accelerating the process, though in a restricted way, for the scale of reactors used.

Nesta tese foi estudada a influência da recirculação do percolado, ajustando as melhores taxas e freqüências, para degradação da fração orgânica dos resíduos sólidos urbanos, em sistema de batelada de uma e duas fases (híbrido). Foram utilizados reatores de 3,45 litros preenchidos com resíduo sólido urbano padrão (FORSUp), percolado como inóculo e um filtro anaeróbio como reator metanogênico. Foram testadas as taxas de recirculação do inóculo de 1%, 2,5%, 5%, 10%, 20%, 30% e 50% e seu monitoramento feito por análises físico-químicas e microbiológicas. O reator que apresentou melhores valores de produção de metano e redução de DQO foi aquele com taxa de recirculação de 20% do percolado metanogênico. Na segunda etapa foram operados três digestores de 50L, alimentados com a FORSUp com as melhores taxas de recirculação determinadas na primeira etapa desse trabalho e a obtida no trabalho de Salgado (2003). Um reator simulou o reator acidogênico de um sistema de duas fases, no qual 20% de seu inóculo foi injetado em um filtro anaeróbio (com tempo de detenção hidráulico de 24 horas). Um outro sistema com taxa de 10% de recirculação de percolado foi operado como reator de uma fase. Outro reator, inoculado com a mesma quantidade de FORSUp e percolado, porém, não se realizou qualquer recirculação do seu inóculo (controle), servindo para comparar os digestores de uma e duas fases. O sistema de duas fases, comparado aos demais reatores, confirmou que a taxa de recirculação de 20%, obteve maior eficiência na partida, com elevada produção de metano e maior percentual de degradação de sólidos. Os exames microscópicos realizados em amostras de percolado desses reatores revelaram predominância de organismos de morfologia com características de Methanococcus e Methanosarcina. Concluiu-se que a taxa de recirculação de percolado influi significativamente nos reatores degradando a matéria orgânica. O estudo cinético confirmou que o processo de digestão obedece a cinética das reações em série, com elevados valores de k´1 / This thesis studied the influence of the leachate recirculation, adjusting to the best rates and frequencies, for degradation of the organic fraction of the urban solid wastes, in one and two-phases (hybrid) system. Bioreactors of 3.45 L were used and filled out with OFMSW pattern, leachate as seed and an anaerobic filter as methanogenic reactor. The performance of the reactors was analyzed varying recirculation rates (1, 2.5, 5, 10, 20, 30 and 50 % in volume of seed). Leachate samples from these reactors were examined through microscopical examinations and physical-chemical analyses to evaluate its performance. The reactor with 20% recirculation rate, got larger efficiency in the departure, methane production and percentage of solid degradation, compared to the others reactors. In the second stage, three 50L digesters were operated and fed with standard OFMSW with the best recirculation rates of the first stage and the best rate obtained in Salgado (2003). A bioreactor simulated the acidogenic reactor of a two-phase system, in which 20% of its seed was injected in anaerobic filter (with hydraulic detention time of 24 hours). Another system, with 10% of recirculation rate of leachate was operated in a one-phase reactor. Once more bioreactor, inoculated like others, however, without any recirculation were studied to compare with one and two-phase reactor. The two-phase system confirmed that the 20% recirculation rate, compared to the others reactors, obtained better efficiency with high methane production and solid degradation. The microscopical examinations in the leachate samples from this reactor presented predominance of organisms with characteristical morphology from Methanococcus and Methanosarcina. It was concluded that the leachate recirculation has significant influence in the degradation of organic matter bioreactors. The kinetic study confirmed that the anaerobic process for OFMSW proceed the in series kinetics, with high constants values of first order

Le secteur de la méthanisation à la ferme ou territoriale connait un fort développement, entrainant la production de grandes quantités de digestats. Si la fraction solide de ces digestats est généralement utilisée en tant qu’amendement organique, la fraction liquide peut être valorisée par la récupération des éléments minéraux bien que la présence de composés organiques pose des problèmes de traitement et d’élimination. Les objectifs de cette thèse sont i) de caractériser la fraction liquide des digestats et donner des premiers éléments pour leur futur traitement et ii) d’expliquer la variabilité des composés résiduels présents dans cette fraction liquide en relation avec l’origine des substrats, les paramètres du procédé de méthanisation et le type de séparation solide/liquide. Dans une première partie, nous avons caractérisé de manière détaillée onze digestats issus d’installations industrielles de co-digestion. Le fractionnement par neuf filtrations successives de la fraction liquide des digestats a permis de quantifier la contribution des matières en suspension, des colloïdes grossiers et fins et des matières dissoutes aux différents paramètres physico-chimiques et biologiques. Il a été montré la faible biodégradabilité aérobie des composés organiques dont la majeure partie se trouve dans la matière en suspension (> 1,2 µm). Pour élargir la base de données, nous avons caractérisé dix-huit digestats supplémentaires et un digestat de boues de station d’épuration dont les fractions liquides ont été fractionnées par deux filtrations successives (1,2 μm et 1 kDa). L’analyse en composantes principales, la classification hiérarchique et la matrice de corrélation réalisées sur l’ensemble des 30 digestats ont mis en avant l’impact majeur des techniques de séparation solide/liquide sur la composition de la fraction liquide des digestats. Dans le groupe des techniques de séparation hautement performantes, des sous-groupes ont permis de distinguer les digestats à base de boues d’épuration, ceux à base de lisiers porcins et ceux issus de procédés piston thermophiles. Dans le groupe des procédés de séparation à faible performance, les teneurs en DCO et matières sèches de la fraction liquide des digestats ont été corrélées aux teneurs en cultures énergétiques et fumiers bovins dans l’alimentation. Finalement, pour l’ensemble des digestats, le paramètre SUVA, lié à la teneur en matière aromatique et à la stabilisation des composés, a été corrélé au temps de séjour des digesteurs. Pour comprendre l’origine des composés résiduels observés dans la fraction liquide des digestats issus de la co-digestion avec de fortes proportions de fumier bovin, quatre réacteurs CSTR alimentés avec respectivement de la paille de blé, de la bouse de vache et du fumier ont été conduits pendant 48 semaines. Les performances de méthanisation ont mis en évidence le caractère âgé du fumier qui avait été partiellement dégradé pendant le stockage à la ferme. Ainsi la fraction liquide du digestat du fumier a présenté les plus fortes concentrations en composés organiques qui en outre présentaient une complexité, mesurée par fluorimétrie 3D, plus élevée que les autres substrats. La fraction liquide du digestat issue de la méthanisation de la paille a révélé les plus fortes proportions de DCO dans les fractions colloïdales et dissoutes. La faible biodégradabilité des composés organiques et leur forte proportion dans les matières en suspension suggèrent le développement de procédés physico-chimiques de séparation tels que la coagulation pour le traitement de la fraction liquide des digestats. / Agricultural and centralized biogas plants are facing a fast development, leading to the production of huge amounts of digestates. Whereas the solid fraction of digestates is used as fertilizer, the liquid fraction can be valorized by the recovery of mineral materials, although the presence of organic compounds may be problematic for the treatment and disposal of this effluent. The objectives of this thesis are: i) to characterize the liquid fraction of digestates and to provide guidelines for its further treatment, ii) to explain the variability of residual compounds in the liquid fraction of digestates in relation with substrate origin, process parameters and the type of solid-liquid separation. In a first part, eleven digestates from full scale codigestion plants were thoroughly characterized. Their liquid fractions were fractionated by nine successive filtrations, which allowed quantifying the contribution of suspended particles, coarse and fine colloids and dissolved matter on several physico-chemical and biological parameters. Organic compounds were mainly found in suspended particles (> 1.2 µm) and presented low aerobic biodegradability. To enlarge the data base, eighteen more digestates from codigestion and one digestate from waste activated sludge were characterized; their liquid fractions were fractionated by two successive filtrations (1.2 μm and 1 kDa). Principal component analysis, hierarchical clustering analysis and correlation matrix carried out on the 30 digestates set, highlighted the major impact of the solid-liquid separation process on the composition of the liquid fraction of digestates. In the high performance separation process group, subgroups allowed separating digestates from sewage sludge, digestates from pig manure and digestates from plug-flow thermophilic processes. In the low performance separation process group, COD and total solids concentration in the liquid fraction of digestates were correlated to the percentage of energy crops and cow manure in the feed. Finally, SUVA parameter which accounts for aromatic compounds content and the stabilization of organic matter, was correlated to the retention time in digester for the whole digestates set. To understand the origin of residual compounds in the liquid fraction of digestates from co-digestion of high proportions of cattle manure, four CSTR reactors fed with wheat straw, cow dung and cow manure were operated for 48 weeks. Anaerobic digestion performances showed that cow manure had undergone some aerobic degradation during its storage at the farm. Therefore, the liquid fraction of manure digestate had the highest concentrations in organic compounds. In addition, these organic compounds had the highest complexity measured by 3D fluorimetry. The low biodegradability of organic compounds and their high percentage in suspended particles suggest the development of physico-chemical separation process such as coagulation for the treatment of the liquid fraction of digestates

La digestion anaérobie est utilisée depuis près d’un siècle comme un traitement efficace des déchets organiques. L’intérêt de ce traitement en anaérobie est en essor, car il présente des avantages significatifs sur les traitements alternatifs biologiques et d’autres options d’élimination des déchets. Cette étude se focalise sur l’optimisation du processus de digestion anaérobie en utilisant deux stratégies différentes. La première vise à augmenter la biodégradabilité du substrat par un prétraitement thermique. La seconde technique repose sur l’utilisation d’un système de biofilms pour augmenter le taux de production de biogaz et minimiser la taille du réacteur.Les déchets alimentaires sont principalement utilisés comme substrat modèle de par leur composition, leur abondance et leur renouvellement. Dans ces travaux de thèse, l’influence de la température des prétraitements thermiques sur la solubilisation de la matière organique, ainsi que la production de méthane des déchets alimentaires sous différentes conditions ont été étudié. Une amélioration significative de la solubilisation et de la biodégradabilité des déchets alimentaires ont été observés pour tous les prétraitements thermiques sur les déchets alimentaires comparativement aux déchets non traités. La plus importante amélioration (28%) de la biodégradabilité a été observée pour les déchets alimentaires traités à la plus basse température de prétraitements (80°C). Les résultats montrent une corrélation forte entre le type de substrats (carbohydrate, protéines et teneur en lipides), la température de prétraitement thermique et son efficacité dans l’amélioration de la biodégradabilité.Dans une seconde partie, une opération prolongée d’un système intégré à deux étages, incluant une cuve agitée en continu et un réacteur à biofilm anaérobie a été réalisé pour produire du biohytane (biohydrogène et méthane) à partir de déchets alimentaires. Le réacteur à biofilm anaérobie a été utilisé pour remédier au lessivage de la biomasse du réacteur. La formation d’une biomasse mature et équilibrée a amélioré de façon importante la stabilité du processus, ce dernier n’ayant pas été affecté par un raccourcissement du temps de rétention hydraulique (HRT) de 6 à 3,7 jours dans le premier réacteur, et de 20 à 1,5 jours dans le second réacteur. De plus, le système à deux étages, constitué d’un pilote à l’échelle d’un batch pour la fermentation sombre et d’un réacteur à biofilm anaérobie, coproduisant de l’hydrogène et du méthane à partir de la fraction organique des déchets solide ménagers (OFMSW), a été utilisé afin de déterminer la capacité d’un réacteur à biofilm anaérobie à supporter un choc de charge organique. Les résultats montrent une récupération plus rapide du réacteur à biofilm anaérobie après un évènement de charge organique / Anaerobic digestion (AD) has been used over a century for an effective treatment of organic wastes. Interest in anaerobic treatment is continually increasing since it presents significant advantages when compared to alternative biological treatments and waste disposal options. This research study was mainly focused on optimization of the AD process, that was achieved through two different strategies. The first aimed at increasing the substrate biodegradability by a means of thermal pretreatment. The second was focused on the application of a biofilm based system to improve the biogas production rates and minimize the reactor size.Food waste (FW) was mainly used as a model substrate due to its suitable composition, abundance and renewability. In this thesis the influence of thermal pretreatment temperature on organic matter solubilization and methane yield of FW under different operational conditions was investigated. Significant improvement of the FW solubilization and biodegradability were observed for all thermally pretreated FW compared to the untreated FW. The highest biodegradability enhancement, i.e. + 28 %, was observed for FW treated at the lowest thermal pretreatment temperature, i.e. 80 ⁰C. The results showed a strong correlation between the substrate type (e.g. carbohydrate, protein and lipid content), the thermal pretreatment temperature and its effectiveness in promoting the biodegradability.In the second part of the work, a prolonged operation of an integrated two-stage system, including a continuously stirred tank and an anaerobic biofilm reactor, was carried out to produce biohythane (biohydrogen and methane) from the FW. The anaerobic biofilm reactor was employed to overcome the biomass wash-out from the reactor. The formation of a well-matured and balanced AD biomass greatly improved the process stability, which was not affected by shortening the hydraulic retention time (HRT) from 6 to 3.7 days in the first reactor and from 20 to 1.5 days in the second reactor. Moreover a two-stage system, comprised of a pilot scale batch dark fermenter and an anaerobic biofilm reactor co-producing hydrogen and methane from the organic fraction of municipal solid waste (OFMSW), was used to assess the capability of the anaerobic biofilm reactor to face an organic shock loads. The results showed a faster recovery of anaerobic biofilm reactor performance after the shock load events

La digestion anaérobie est un processus biologique de transformation de la matière organique permettant la production d’énergie sous forme de biogaz et de fertilisant sous forme de digestat. C’est une filière émergente en France, dont les objectifs de développement sont ambitieux. Le développement d’une filière industrielle sur l’ensemble du territoire Français nécessite la mise en oeuvre d’outils d’aide à la décision.Dans le cadre de cette Thèse nous proposons d’évaluer le potentiel de développement de la méthanisation collective, territoriale et agricole par injection du biogaz dans les réseaux de gaz naturel. Les travaux de recherchent portent sur trois axes : (1)l’évaluation du potentiel de mobilisation de biomasse d’origine agricole ; (2) la conception et l’étude de la viabilité économique de « modèle type » d’usine de méthanisation ; (3) l’évaluation de la performance technico-économique d’une exploitation agricole ayant recours à la méthanisation dans but d’accroitre son autonomie face aux énergies fossiles et aux engrais chimiques.Sur le premier volet, nous avons réalisé une étude cartographique des gisements agricoles mobilisables. Nous avons localisé et quantifié les quantités de coproduits de cultures et d’effluents d’élevage présent sur le territoire Français. Nous avons mis en évidence que le potentiel de mobilisation de biomasse agricole est de l’ordre de 57millions de tonnes de matière sèche. Ceci correspond à une production énergétique maximale de l’ordre de 158 TWh/an.Sur le deuxième volet, nous avons conçu des « modèles types » d’usines de méthanisation de différentes tailles, dont le biogaz est valorisé en biométhane par injection dans le réseau. Pour chacun des « modèles types » nous avons comparé la viabilité technico-économiques des modèles selon différentes « recettes » de biomasse. L’évaluation met en avant que pour chaque « modèle type », il existe un nombre limité de « recettes » permettant à chacun d’entre eux de trouver un équilibre technico-économique.Sur le troisième volet, nous nous sommes intéressés à l’autonomie azote et carburant que pourrait atteindre une exploitation agricole en méthanisant des cultures énergétiques dédiées de légumineuse. L’évaluation a été menée sur des fermes présentant des configurations différentes d’assolement et de rendement. Nous avons mis en évidence les conditions nécessaires pour que chaque configuration de ferme puisse atteindre l’autonomie. Il en ressort que dans certaines conditions, une exploitation « autonome » présente des marges brutes supérieures à celle d’une exploitation conventionnelle. / Anaerobic digestion is a biological process of transformation of organicmatter allowing the production of energy in the form of biogas and fertilizer in the formof digestate. It is an emerging sector in France, whose development objectives are ambitious. The development of an industrial sector throughout the French territory requires the implementation of decision support tools.As part of this thesis, we propose to evaluate the development potential of collective,territorial and agricultural methanation by injecting biogas into natural gas networks.Research work focuses on three axes: (1) the evaluation of the biomass mobilization potential of agricultural origin; (2) the design and study of the economic viability of a"typical model" of methanation plant; (3) the evaluation of the technical and economic performance of a farm using methanation in order to increase its autonomy in the face of fossil fuels and chemical fertilizers.We first carried out a cartographic study of mobilizable agricultural deposits. The quantities of co-products of crops and livestock effluents present on the French territor ywere located and quantified. Thus, we have shown that the potential for mobilization of agricultural biomass is of the order of 57 million tons of dry matter. This corresponds to a maximum energy production of about 158 TWh / year.And second, we have designed "model models" of biogas plants of different sizes,whose biogas is valorized in biomethane by injection into the network. For each of the"standard models" we compared the techno-economic viability of the models according to different "recipes" of biomass. The evaluation points out that for each "standard model" there is a limited number of "recipes" allowing each of them to find a technoeconomic balance.Finally, we focused on the nitrogen and fuel autonomy that an agricultural operationcould achieve by methanising dedicated energy crops of legumes. The assessment was conducted on farms with different rotational and yield configurations. We have highlighted the conditions necessary for each farm configuration to achieve autonomy.It shows that under certain conditions, an "autonomous" farm has gross margins higher than that of a conventional farm.

Le processus de digestion anaérobie conduit à la production de biométhane, un vecteur flexible d’énergie renouvelable. L’amélioration du rendement de ce processus est souvent évoquée comme dépendante de la compréhension approfondie de la structure et de la dynamique des communautés microbiennes qui y sont impliquées. L’objectif de la thèse a été de caractériser les communautés microbiennes impliquées dans le processus de digestion anaérobie et de déterminer l’influence de facteurs opérationnels sur leurs dynamiques. Nous nous sommes en particulier intéressés à l’augmentation du taux de charge organique, le type de digesteurs anaérobies (réacteur continu perpétuellement mélangé vs réacteur anaérobie à chicane), mais aussi à la phase de démarrage d’un digesteur de ferme avec une montée en température. En absence de conditions contraignantes, nous avons observé l’installation de populations méthanogènes les mieux adaptées à la production de biogaz dans les réacteurs étudiés et la mise en place de communautés microbiennes similaires entre réacteurs réplicats. Cependant, des changements au niveau opérationnel ont conduit au développement de communautés divergentes en termes de structure. En effet, en présence d’un environnement déterministe, la plupart des bactéries et archées impliquées en digestion anaérobie ont montré une redondance fonctionnelle à la perturbation. Toutefois, certaines populations bactériennes dominantes ont également pu montrer des phénomènes de résistance, en termes de présence et d’abondance, à l’évolution des conditions environnementales. Au cours de nos études, les différentes communautés s’installant dans les digesteurs étudiés ont également montré des aptitudes variables pour la production de biogaz. De plus, des corrélations entre les communautés bactériennes, archées et eucaryotes ont aussi été démontrées, soulignant le rôle non négligeable des eucaryotes dans le processus de digestion anaérobie et l’installation de communautés microbiennes dominantes et spécifiques à la production de biogaz. Ainsi, les changements au sein de la communauté microbienne résultant de la modification progressive de facteurs opérationnels, et ce bien avant l’apparition des premiers symptômes d’inhibition de la production de biogaz, pourraient permettre le développement d’indicateurs microbiens de l’état du processus de digestion anaérobie et donc la mise en place d’une gestion microbiologique raisonnée des digesteurs anaérobies / The anaerobic digestion process leads to the production of biomethane, a versatile renewable energy vector. The dynamics and interactions between specific microbial groups are currently considered as key research subjects towards the improvement of the anaerobic digestion (AD) process. Indeed, deeper knowledge of the ecology of AD, the dynamics of the microbial populations and their structure could provide valuable information regarding unexplained and unpredictable failures or malfunctioning of the anaerobic digestion process. The aim of this work was to characterize the microbial communities involved in the AD process, and to study their responses due to the change of operational parameters such as an increase of the organic loading rate, the reactor type (completely stirred tank reactor vs anaerobic baffled reactor), or the start-up phase of a farm reactor with a shift from psychrophilic to mesophilic temperature range. While we observed the installation of similar microbial populations between replicated reactors under stable conditions, best adapted to biogas production, the microbial communities started to diverge once the operational parameters changed. Indeed, due to deterministic environment, most of bacteria and archaea showed redundant functional adaptation to the changing environmental conditions. However, some dominant bacterial populations were also resistant in terms of presence and abundance to the environmental change. The specific microbial communities established in our studied reactors showed also discrepancies in terms of biogas yields. Furthermore, correlations between the bacterial, archaeal and eukaryotic communities were pointed out, indicating the putative influence of eukaryotes on the anaerobic digestion process and the establishment of the other microbes having crucial functions during the anaerobic biomass digestion. Interestingly, shifts inside the anaerobic microbial community due to the gradual change of operational parameters, were detected prior to any biogas production inhibition, giving the opportunity for the development of potential early microbial indicators for assessing the AD process status and improving the microbial management of anaerobic reactors

La produzione di biogas è un tematica di forte impatto globale per due ragioni principali: il prossimo esaurimento dei combustibili fossili e l’inquinamento ambientale dovuto allo smaltimento di scarti organici. La Digestione Anaerobica (DA) è un processo biologico che permette la risoluzione di entrambi i problemi, producendo energia (in forma di biogas) e convertendo gli scarti organici in metano e anidride carbonica. Tale processo è basato su una complessa catena sintrofica tra consorzi microbici che produco il substrato per la fase finale di metanogenesi. Il siero di latte è uno scarto altamente inquinante derivante dal processo di lavorazione del formaggio e per questo è stato ampiamente investigato come substrato per la DA. Tuttavia esiste uno scarto meno noto prodotto dalle fasi di porzionatura e grattugia del formaggio a lunga stagionatura. Il presente studio analizza il microbioma di digestori anaerobici processanti scarti dell’industria lattiero-casearia, quali letame bovino, siero di latte e scarto del formaggio a pasta dura. In particolare, viene analizzato l’effetto dei parametri di processo, delle diverse configurazioni dei reattori e del tipo di scarto, su tale microbioma. L’obiettivo è raggiunto tramite tecniche biomolecolari che permettono di quantificare e identificare le principali specie presenti nei reattori, insieme alla differente espressione genica in seguito all’iniezione di idrogeno a scopo di upgrading del biogas. / Biogas production is a hot topic, which has globally gained interest from many researchers over the past years. This fact is mainly due to the depletion of fossil fuels and environmental concerns regarding wastes disposal. Anaerobic Digestion (AD) represents a biological way to obtain both energy (in form of biogas) and waste discard, by converting the polluting organic matter. The overall process relies on a syntrophic chain where different microbial consortia produce the feed necessary for the final methanogenic step. Cheese whey has been largely investigated for AD treatment, since is a high polluting waste derived from the cheese-making process. However, there is a less-known waste originating from the portioning and shaving phases of long-ripened hard-cheese. This study aimed to investigate the microbiome of anaerobic digesters processing dairy industry wastes, such as cattle manure, cheese whey and hard-cheese powder wastes. In particular, the effects of process parameters, reactor configurations and type of dairy wastes, on the microbial populations, have been analyzed. The goal was achieved by means of culture-independent methods and high throughput sequencing, which allowed quantifying and identifying the main species present, as well as their differential gene expression in relation to hydrogen injection for biogas upgrading purposes.

Les stations d’épuration constituent une voie majeure de dissémination des micropolluants minéraux et organiques dans l’environnement. De nombreux composés émergents ne sont pas totalement éliminés des eaux usées et sont transférés aux boues par sorption du fait de leurs propriétés physico-chimiques. Parmi ces composés, les résidus de médicaments doivent être suivis car ils peuvent avoir des effets indésirables sur les organismes une fois rejetés dans l’environnement. L’épandage des boues stabilisées sur les sols étant le procédé de valorisation le plus employé en France, le choix du traitement des boues en amont, permettant de réduire au maximum la dissémination des micropolluants constitue une question scientifique et technique fondamentale. Dans ce travail, le devenir de micropolluants métalliques (cadmium et cuivre) et de plusieurs médicaments (carbamazépine, ciprofloxacine, sulfaméthoxazole, acide salicylique, ibuprofène, paracétamol, diclofénac, kétoprofène, éconazole, aténolol et propranolol) a été étudié pour différents lots de boues urbaines (avec ou sans traitement par ozonation) et aussi de manière originale sur des boues provenant exclusivement du traitement d’effluents hospitaliers (station de SIPIBEL), au cours de leur traitement (épaississement puis stabilisation par compostage, chaulage ou digestion anaérobie). La méthodologie proposée a reposé sur la mise en relation : d’une part des coefficients de répartition de ces micropolluants entre les fractions soluble et particulaire (Kdsorption) dans la boue après chaque traitement de stabilisation ainsi que de leur potentiel de désorption (Kdésorption) avec d’autre part les propriétés des micropolluants et les caractéristiques des boues (composition biochimique et groupements fonctionnels). Cette mise en relation a abouti, grâce à une analyse statistique de type PLS à la proposition de modèles permettant de prédire les valeurs de Kdsorption et Kdésorption. Il a ainsi pu être démontré que le pH des boues ainsi que les groupements fonctionnels de type phosphorique dans la phase soluble et de type amine/hydroxyle dans la fraction particulaire des boues avaient une influence majeure sur le comportement de sorption des micropolluants organiques, de même que la masse molaire et la solubilité de ces derniers. D’autre part, ce travail a permis de montrer que l’ozonation des boues en amont des traitements de stabilisation s’est avérée efficace car elle a permis d’éliminer huit composés pharmaceutiques sur les onze étudiés. Pour tous les lots de boues, le sulfaméthoxazole a été biodégradé au cours de la digestion anaérobie. Les tests de désorption en batch effectués sur les boues après chaulage et digestion ont montré que les micropolluants dans les boues chaulées ont tendance à être plus facilement relargués qu’après digestion anaérobie. Enfin, l’étude de la disponibilité des micropolluants lors de l’épandage des différents lots de boues urbaines et hospitalières stabilisées sur des colonnes de sol à l’échelle du laboratoire a montré que l’ibuprofène, l’acide salicylique, le diclofénac et le paracétamol étaient les seuls composés détectés dans les phases lixiviées des sols amendés, ce qui traduit une faible mobilité des autres composés dans le sol. / Wastewater treatment plants represent the main transfer pathways for micropollutants to enter the environment. Emerging contaminants are not totally eliminated and are transferred to the sludge by sorption process due to their physico-chemical properties. Among them, pharmaceutical compounds are of a great concern because of their potential adverse effects to ecosystems. As sludge landspreading is the main process of valorization employed in France, the choice of the kind of sludge stabilization treatment able to reduce the amount of micropollutants is crucial. In this work, the fate of trace metallic elements (cadmium and copper) and pharmaceutical compounds (carbamazepine, ciprofloxacin, sulfamethoxazole, salicylic acid, ibuprofen, paracetamol, diclofenac, ketoprofen, econazole, atenolol and propranolol) has been investigated in sludge from different origins: urban (with and without ozone oxidation treatment) and hospital, during their treatment (thickening and stabilization by composting, liming or anaerobic digestion). The methodology developed in this work consisted in connecting the partition coefficients of micropollutants (between the soluble and particulate fractions of sludge, Kdsorption) and their desorption potential (Kdesorption) with micropollutants physico-chemical properties and sludge characteristics (biochemical composition and functional groups). Statistical analysis leads to the determination of models able to predict Kdsorption and Kdesorption. Molecular weight and solubility of pharmaceutical compounds, sludge’s pH, phosphoric functional groups in the soluble phase and amine/hydroxyl groups in the particulate fraction of sludge had the main impact on the sorption behavior. Moreover the oxidation of sludge with ozone before stabilization was efficient to eliminate eight from eleven organic compounds. For all sludge samples, sulfamethoxazole was biodegraded during anaerobic digestion. Batch desorption tests showed that micropollutants were more easily desorbed in limed sludge compared to digested sludge. Finally, the study of micropollutants availability during stabilized urban and hospital sludge landspreading on laboratory soil columns revealed that ibuprofen, salicylic acid, diclofenac and paracetamol were the only compounds present in leachates. This means that the other pharmaceutical compounds exhibited a lower mobility in soil.

Hydrothermal carbonization (HTC) is a process where elevated temperature and pressure is used in order to convert biomass to hydrochar, a coal-like substance with good dewatering properties and many potential uses. HTC can be used to treat digestate from anaerobic digestion, but the process water that remains after the hydrochar has been recovered needs to be treated further in the wastewater treatment plant. In order to make HTC more competitive compared to other sludge treatments it is important to find a good use for the process water. The main objective of this master thesis was to investigate the effects of recirculating HTC process water to the anaerobic digestion. To achieve the objective, both theoretical calculations and experimental trials were performed. The experimental trials were conducted with an Automatic Methane Potential Test System (AMPTS II) in order to investigate the anaerobic digestion in laboratory scale. In the first trial, three substrates, process water, hydrochar, and primary sludge were tested for their biochemical methane potential (BMP). All substrates were mixed with inoculum. Process water had a BMP of 335 ± 10 % NmL/gvs (normalized CH4 production in mL per g added VS (volatile solids)), hydrochar had BMP of 150 ± 5 % NmL/gvs, and primary sludge had a BMP of 343 ± 2 % NmL/gvs. The methane production was almost the same for process water as for primary sludge i.e. no inhibitory effects could be seen when process water was mixed with only inoculum. In the second trial, a more realistic scenario was tested where process water was co-digested with primary sludge at different ratios. The results from the second trial were not statistically reliable and therefore cannot be used on their own to determine with certainty if the process water could have an inhibitory effect in a full-scale anaerobic digester. However, the combined results from both trials indicate that it is unlikely that the process water would have an inhibitory effect. The possible increase in methane yield, if the digestate from a biogas facility was treated in full-scale implementation of the HTC process, was calculated theoretically. The produced process water would have the capacity to increase the methane production with approximately 10 % for a biogas facility. For the calculations, the BMP for process water was assumed to be 335 NmL/gvs and no synergetic effects was considered.