O desenvolvimento industrial tem, como conseqüência, a maior geração de resíduos, muitos deles tóxicos aos seres vivos. Dentre esses, benzeno, tolueno e xilenos (BTX), derivados do petróleo, estão contaminando aqüíferos por acidentes no transporte e no armazenamento. Por esse motivo, diversas pesquisas têm sido realizadas buscando formas de biodegradar BTX. Esses trabalhos indicam que os principais fatores que podem influenciar a degradação biológica dos BTX são temperatura, pH, disponibilidade de nutrientes, concentração de tóxicos e diversidade de microrganismos. Visando contribuir com o estudo desses fatores, este trabalho teve por objetivo avaliar a influência do inóculo e de aceptores de elétrons no processo de degradação anaeróbia de BTX. Neste trabalho três inóculos foram pesquisados: 1- biomassa proveniente de reator anteriormente submetido à mistura de gasolina comercial e água; 2- biomassa proveniente de reator da estação de tratamento de esgoto da USP - São Carlos; 3- biomassa proveniente de reator tratando água residuária de abatedouro de aves. Os resultados obtidos comprovaram que a origem do inóculo foi fundamental na degradação anaeróbia de BTX, pois os inóculos apresentaram diferentes períodos de adaptação e porcentagens de degradação do tóxico. Depois de 93 dias de operação os inóculos 1, 2 e 3 apresentaram eficiência de remoção de BTX da ordem de 57%, 83% e 90%, respectivamente. O reator com o inóculo 3 foi submetido a condições metanogênica, sulfetogênica com presença e ausência de Ferro (III). Os resultados demonstraram que a degradação dos BTX foi influenciada pelas diferentes condições adotadas. A adição de Fe (III) melhorou a degradação dos BTX, do reator sob condições sulfetogênicas. / The industrial development has increased the generation of residues. Some of them are toxics and impact the environment. Benzene, toluene and xylenes (BTX), petroleum sub products, are examples of such toxic compounds. These compounds may contaminate aquifers as a result of accidents during transportation or of leakages of storage tanks. Several factors are reported to affect the biodegradation of BTX, such as: temperature, pH, availability of nutrients, concentration of toxics and diversity of microorganisms. This research aimed to study some of these factors, such as different inoculum sources and different electrons acceptors during BTX degradation processes in an horizontal-flow anaerobic immobilized biomass (HAIB) reactor. In this research three inocula were studied: 1- an adapted microbial community for BTX degradation; 2 - microorganisms collected from a pilot-scale UASB reactor treating domestic wastewater; and 3 - Microorganisms collected from an UASB treating poultry slaughterhouse industry wastewater. The results have shown that the inoculum sources were fundamental to the adaptation period for the toxic biodegradation, producing different BTX removal efficiencies. After 93 days of operation, the inocula 1, 2 and 3 showed BTX removal efficiency of 57, 83 and 90%, respectively. The inoculum 3 was submitted to conditions of methanogesis and sulfetogenesis in the presence and absence of Fe (III). The results demonstrated that BTX degradation was affected by the different conditions adopted, showing that the addition of Fe (III) improved biodegradation in the reactor under sulfate reduction condition.

The depth of the sulfate-methane transition (SMT) above gas hydrate systems is a direct proxy to interpret upward methane flux and hydrate saturation. However, two competing reaction pathways can potentially form the SMT. Moreover, the pore water profiles across the SMT in shallow sediment show broad variability leading to different interpretations for how carbon, including CH4, cycles within gas-charged sediment sequences over time. The amount and distribution of marine gas hydrate impacts the chemistry of several other dissolved pore water species such as the dissolved inorganic carbon (DIC). A one-dimensional (1-D) numerical model is developed to account for downhole changes in pore water constituents, and transient and steady-state profiles are generated for three distinct hydrate settings. The model explains how an upward flux of CH4 consumes most SO42- at a shallow SMT implying that anaerobic oxidation of methane (AOM) is the dominant SO42- reduction pathway, and how a large flux of 13C-enriched DIC enters the SMT from depth impacting chemical changes across the SMT. Crucially, neither the concentration nor the d13C of DIC can be used to interpret the chemical reaction causing the SMT. The overall thesis objective is to develop generalized models building on this 1-D framework to understand the primary controls on gas hydrate occurrence. Existing 1-D models can provide first-order insights on hydrate occurrence, but do not capture the complexity and heterogeneity observed in natural gas hydrate systems. In this study, a two-dimensional (2-D) model is developed to simulate multiphase flow through porous media to account for heterogeneous lithologic structures (e.g., fractures, sand layers) and to show how focused fluid flow within these structures governs local hydrate accumulation. These simulations emphasize the importance of local, vertical, fluid flux on local hydrate accumulation and distribution. Through analysis of the fluid fluxes in 2-D systems, it is shown that a local Peclet number characterizes the local hydrate and free gas saturations, just as the Peclet number characterizes hydrate saturations in 1-D, homogeneous systems. Effects of salinity on phase equilibrium and co-existence of hydrate and gas phases can also be investigated using these models. Finally, infinite slope stability analysis assesses the model to identify for potential subsea slope failure and associated risks due to hydrate formation and free gas accumulation. These generalized models can be adapted to specific field examples to evaluate the amount and distribution of hydrate and free gas and to identify conditions favorable for economic gas production.

Ce travail de thèse visait à développer des procédés d'élimination des sulfates permettant la réduction des teneurs en sulfates des DC et des sols gypsifères afin d'améliorer la qualité des déchets et des sols à des fins agricoles ou des applications de recyclage. Le concept de traitement des DC par lixiviation à l'eau a été étudié (colonne de lixiviation). Les sulfates contenus dans les lixiviats sont ensuite éliminés à l'aide d'un traitement chimique ou biologique. L'approche biologique mise en oeuvre dans ce travail a consisté à mettre en oeuvre la réduction biologique des sulfates au sein de bioréacteurs de conception différente (i.e. réacteur UASB, réacteur à lit fluidisé inverse (IFB) ou d'un réacteur anaérobie gas lift). L'efficacité d'élimination des sulfates la plus élevée atteinte par ces trois systèmes varie de 75 à 95%. L'eau traitée provenant du bioréacteur peut alors ensuite être réutilisé dans la colonne de lixiviation. Le traitement chimique des sulfates est une option alternative pour traiter les lixiviats. Plusieurs produits chimiques ont été testés, (chlorure de baryum, nitrate de plomb (II), le chlorure de calcium, le carbonate de calcium, l'oxyde de calcium, et du sable recouvert d'un mélange d'oxydes d'aluminium et de fer). Un rendement de 99,9% d'élimination des sulfates (par précipitation) a été atteint avec le chlorure de baryum et le nitrate de plomb (II).Pour le traitement des DMA et des sols gypseux, cinq types de substrat organique tel que les copeaux de bambou, les boues d'épuration des eaux usées municipales, de l'écorce de riz, de coques de noix de coco broyée et des boues d'épuration des eaux usées d'une ferme porcine ont été testés comme donneurs d'électrons pour la réduction biologique des sulfates. L'efficacité de la réduction des sulfates la plus élevé (84%) a été obtenue en utilisant un mélange d'écorce de riz, de coques de noix de coco broyée et des boues d'épuration des eaux usées d'une ferme porcine comme donneurs d'électrons. Ensuite, ce mélange organique a été utilisé pour le traitement des sols gypsifères. Le sol de la mine de gypse a été mélangé avec le mélange organique en différentes proportions (10, 20, 30 et 40% de sol). Le rendement le plus élevé de 59 % de réduction des sulfates a été atteint dans le mélange de sol qui contient 40 % de matière organique. L'élimination des sulfures présents dans l'effluent des procédés de réduction biologique des sulfates est nécessaire. En effet, les sulfures peuvent causer plusieurs impacts environnementaux ou être ré-oxydé en sulfate si ils sont directement rejetés dans l'environnement. Le traitement électrochimique des effluents est l'une des solutions alternatives pour la récupération du soufre élémentaire à partir des sulfures. Une électrode de graphite a été testée comme électrode permettant l'oxydation électrochimique des sulfures en soufre élémentaire. Une électrode en graphite de grande surface est nécessaire afin d'avoir une résistance électrique la plus faible possible. La vitesse d'oxydation des sulfures la plus élevée est atteinte lors de l'application d'une résistance de 30 Ω à une concentration en sulfure de 250 mg.L-1 / Solid wastes containing sulfate, such as construction and demolition debris (CDD), are an important source of pollution, which can create a lot of environmental problems. It is suggested that these wastes have to be separated from other wastes, especially organic waste, and place it in a specific area of the landfill. This results in the rapid rise of the disposal costs of these gypsum wastes. Although these wastes can be reused as soil amendment or to make building materials, a concern has been raised by regulators regarding the chemical characteristics of the material and the potential risks to human health and the environment due to CDD containing heavy metals and a high sulfate content. Soils containing gypsum, namely gypsiferous soils, also have several problems during agricultural development such as low water retention capacity, shallow depth to a hardpan and vertical crusting. In some mining areas, gypsiferous soil problems occur, coupled with acid mine drainage (AMD) problems which cause a significant environmental threat. Reduction of the sulfate content of these wastes and soils is an option to overcome the above mentioned problems. This study aimed to develop sulfate removal systems to reduce the sulfate content of CDD and gypsiferous soils in order to decrease the amount of solid wastes as well as to improve the quality of wastes and soils for recycling purposes or agricultural applications. The treatment concept leaches the gypsum contained in the CDD by water in a leaching step. The sulfate containing leachate is further treated in biotic or abiotic systems. Biological sulfate reduction systems used in this research were the Upflow Anaerobic Sludge Blanket (UASB) reactor, Inverse Fluidized Bed (IFB) Reactor and Gas Lift Anaerobic Membrane Bioreactor (GL-AnMBR). The highest sulfate removal efficiency achieved from these three systems ranges from 75 to 95%. The treated water from the bioreactor can then be reused in the leaching column. Chemical sulfate removal (abiotic system) is an alternative option to treat the CDD leachate. Several chemicals were tested including barium chloride, lead(II) nitrate, calcium chloride, calcium carbonate, calcium oxide, aluminium oxide and iron oxide coated sand. A sulfate removal efficiency of 99.9% was achieved with barium chloride and lead(II) nitrate.For AMD and gypsiferous soils treatment, five types of organic substrate including bamboo chips (BC), municipal wastewater treatment sludge (MWTS), rice husk (RH), coconut husk chip (CHC) and pig farm wastewater treatment sludge (PWTS) were tested as electron donors for biological sulfate reduction treating AMD. The highest sulfate reduction efficiency (84%) was achieved when using the combination of PWTS, RH and CHC as electron donors. Then, this organic mixture was further used for treatment of the gypsiferous soils. The gypsum mine soil (overburden) was mixed with an organic mixture in different amounts including 10, 20, 30 and 40% of soil. The highest sulfate removal efficiency of 59% was achieved in the soil mixture which contained 40% organic material.The removal of sulfide from the effluent of the biological sulfate reduction process is required as sulfide can cause several environmental impacts or be re-oxidized to sulfate if directly discharged to the environment. Electrochemical treatment is one of the alternatives for sulfur recovery from aqueous sulfide. A non-catalyzed graphite electrode was tested as electrode for the electrochemical sulfide oxidation. A high surface area of the graphite electrode is required in order to have less internal resistance as much as possible. The highest sulfide oxidation rate was achieved when using the external resistance at 30 Ω at a sulfide concentration of 250 mg L-1

O presente projeto avaliou um reator anaeróbio operado em batelada e batelada alimentada seqüenciais (ASBR), em ciclos de 8 horas, utilizando biomassa granulada e agitação mecânica em um draft-tube, alimentado com água residuária sintética (500 mgDQO/L), contendo sulfato em diferentes relações DQO/[\'SO IND.4\' POT.2-\']. Em todos os ensaios o reator apresentou uma operação estável, produzindo alcalinidade e com concentração de ácidos voláteis totais em níveis adequados. Para os tempos de alimentação de 10 min, 3 h e 6 h, respectivamente, as eficiências de remoção de sulfato foram de 30, 72 e 72% nas operações nas quais o reator foi alimentado com uma relação DQO/[\'SO IND.4\'POT.2-\'] de 1,34. Nos ensaios nos quais o reator foi alimentado na relação DQO/[\'SO IND.4\'POT. 2-\'] de 0,67, as eficiências para a redução de sulfato foram de 25, 58 e 55%, respectivamente. Na operação com relação DQO/[\'SO IND.4\'POT.2-\'] de 0,34, as eficiências para redução de sulfato foram de 23, 37 e 27%, respectivamente. Desta maneira, pode-se concluir que as operações em batelada alimentada favoreceram a remoção de sulfato, enquanto foi observado que nas operações em batelada a remoção de matéria orgânica atingiu melhores eficiências. / This present work evaluate an anaerobic sequencing batch reactor (ASBR), fed in batch and fed-batch, and cycles of 8 hours, using granulated biomass and mechanical stirring in a draft-tube, fed with synthetic wastewater (500 mgCOD/L), enriched with sulfate in some COD/[\'SO IND.4\'POT.2-\'] relations. In all operations the reactor showed a stable operation, producing alkalinity and maintaining the volatile acids in adequate levels. Considering the fed periods of 10 min, 3 h and 6 h, respectively, the removal efficiencies of the sulfate was 30, 72 e 72%, in the operations when the reactor was fed with a COD/[\'SO IND.4\'POT.2-\'] relation of 1,34. In the essays when the reactor was fed in COD/[\'SO IND.4\'POT.2-\'] relation of 0,67, the efficiencies of the sulfate reduction was 25, 58 e 55%, respectively. When the reactor was operated with COD/[\'SO IND.4\'POT.2-\'] relation of 0,34, the efficiencies of sulfate reduction 23, 37 e 27%, respectively. Thus, is possible to conclude that the operations in fed-batch increased the efficiency of sulfate removal, at what time was observed that in batch operations the organic matter removal attained improved efficiencies.

O desenvolvimento industrial tem, como conseqüência, a maior geração de resíduos, muitos deles tóxicos aos seres vivos. Dentre esses, benzeno, tolueno e xilenos (BTX), derivados do petróleo, estão contaminando aqüíferos por acidentes no transporte e no armazenamento. Por esse motivo, diversas pesquisas têm sido realizadas buscando formas de biodegradar BTX. Esses trabalhos indicam que os principais fatores que podem influenciar a degradação biológica dos BTX são temperatura, pH, disponibilidade de nutrientes, concentração de tóxicos e diversidade de microrganismos. Visando contribuir com o estudo desses fatores, este trabalho teve por objetivo avaliar a influência do inóculo e de aceptores de elétrons no processo de degradação anaeróbia de BTX. Neste trabalho três inóculos foram pesquisados: 1- biomassa proveniente de reator anteriormente submetido à mistura de gasolina comercial e água; 2- biomassa proveniente de reator da estação de tratamento de esgoto da USP - São Carlos; 3- biomassa proveniente de reator tratando água residuária de abatedouro de aves. Os resultados obtidos comprovaram que a origem do inóculo foi fundamental na degradação anaeróbia de BTX, pois os inóculos apresentaram diferentes períodos de adaptação e porcentagens de degradação do tóxico. Depois de 93 dias de operação os inóculos 1, 2 e 3 apresentaram eficiência de remoção de BTX da ordem de 57%, 83% e 90%, respectivamente. O reator com o inóculo 3 foi submetido a condições metanogênica, sulfetogênica com presença e ausência de Ferro (III). Os resultados demonstraram que a degradação dos BTX foi influenciada pelas diferentes condições adotadas. A adição de Fe (III) melhorou a degradação dos BTX, do reator sob condições sulfetogênicas. / The industrial development has increased the generation of residues. Some of them are toxics and impact the environment. Benzene, toluene and xylenes (BTX), petroleum sub products, are examples of such toxic compounds. These compounds may contaminate aquifers as a result of accidents during transportation or of leakages of storage tanks. Several factors are reported to affect the biodegradation of BTX, such as: temperature, pH, availability of nutrients, concentration of toxics and diversity of microorganisms. This research aimed to study some of these factors, such as different inoculum sources and different electrons acceptors during BTX degradation processes in an horizontal-flow anaerobic immobilized biomass (HAIB) reactor. In this research three inocula were studied: 1- an adapted microbial community for BTX degradation; 2 - microorganisms collected from a pilot-scale UASB reactor treating domestic wastewater; and 3 - Microorganisms collected from an UASB treating poultry slaughterhouse industry wastewater. The results have shown that the inoculum sources were fundamental to the adaptation period for the toxic biodegradation, producing different BTX removal efficiencies. After 93 days of operation, the inocula 1, 2 and 3 showed BTX removal efficiency of 57, 83 and 90%, respectively. The inoculum 3 was submitted to conditions of methanogesis and sulfetogenesis in the presence and absence of Fe (III). The results demonstrated that BTX degradation was affected by the different conditions adopted, showing that the addition of Fe (III) improved biodegradation in the reactor under sulfate reduction condition.

L'oxydation anaérobie du méthane (AOM) couplé à la réduction du sulfate (AOM-SR) est un processus biologique médié par méthanotrophes anaérobie (ANME) et de bactéries sulfato-réductrices. La communauté scientifique s'inquiète de AOM, en raison de sa pertinence dans la régulation du cycle global du carbone et de la potentielle application biotechnologique pour le traitement de sulfate riches eaux usées.Pour améliorer les connaissances récentes sur les conditions de distribution et d'enrichissement ANME, cette recherche a étudié AOM-SR avec les objectifs suivants: (i) caractériser les communautés microbiennes responsables de AOM dans les sédiments marins, (ii) de les enrichir dans les bioréacteurs avec différentes configurations, à savoir bioréacteur à membrane (MBR), filtre biotrickling (BTF) et bioréacteur à haute pression (HPB), et (iii) d'évaluer l'activité de l'ANME et le processus AOM dans différentes conditions de pression et de température.Les microbes habitant peu profonde dans les sédiments de Marine lac Grevelingen (Pays-Bas) ont été caractérisés et leur capacité de faire AOM-SR a été évaluée. Un test d'activité a été réalisée en discontinu pour 250 jours, AOM-SR est mise en évidence par la production de sulfure et de la prise concomitante de sulfate et de méthane dans des rapports équimolaires et il a été atteint 5 µmoles par gramme de poids par jour de taux de réduction du sulfate. L'analyse des séquences de gènes 16SrRNA a montré la présence de méthanotrophes anaérobie ANME-3 dans les sédiments marins du lac Grevelingen.Deux configurations de bioréacteurs, à savoir MBR et BTF ont été opérés dans des conditions ambiantes pendant 726 jours et 380 jours, respectivement, pour enrichir les micro-organismes de Ginsburg Mud Volcano performantes AOM. Les réacteurs sont exploités en mode fed-batch pour la phase liquide avec un apport continu de méthane. Dans le MBR, une membrane d'ultrafiltration externe a été utilisée pour retenir la biomasse, alors que, dans la BTF, la rétention de biomasse a été accomplie par la fixation de la biomasse sur le matériau d'emballage. AOM-SR a été enregistrée seulement après ~ 200 jours dans les deux configurations de bioréacteurs. L'opération du BTF a montré l'enrichissement de l'ANME dans le biofilm par la méthode Illumina Miseq, en particulier ANME-1 (40%) et ANME-2 (10%). Dans le MBR, les agrégats d'ANME-2 et Desulfosarcina ont été visualisées par CARD-FISH. La production d'acétate a été observée dans le MBR, ce qui indique que l'acétate était un possible intermédiaire d'AOM. Bien que les deux configurations de bioréacteurs ont montré de bonnes performances, le taux de réduction du sulfate était légèrement plus élevée et plus rapide dans la BTF (1,3 mM par jour âpres 280 jours) que le MBR (0,5 mM par jour jour âpres 380 jours).Afin de simuler les conditions de suintement froid et de différencier l'impact des conditions environnementales sur AOM, les sédiments fortement enrichi avec le clade ANME-2a ont été incubées dans HPB à différentes températures (4, 15 et 25 °C à 100 bars) et pressions (20, 100, 200 et 300 bar à 15 °C). L'incubation à une pression de 100 bar et 15 ° C a été observé comme la condition la plus appropriée pour la phylotype ANME-2a, qui est similaire aux conditions in situ (Capitaine Aryutinov Mud Volcano, Golfe de Cadix). L'incubation de ce sédiment aux conditions in situ pourrait être une option privilégiée pour obtenir une activité AOM-SR plus élevée.Dans cette thèse, il a été démontré expérimentalement que la rétention de la biomasse et l'approvisionnement continu de méthane peuvent favoriser la croissance de la lente communauté microbienne qui oxyde le méthane en anaérobiose dans des bioréacteurs, même dans des conditions ambiantes. Par conséquent, la localisation des habitats de ANME dans des environnements peu profonds et l'enrichissant dans des conditions ambiantes peut être avantageuse pour les futures applications de la biotechnologie environnementale / Anaerobic oxidation of methane (AOM) coupled to sulfate reduction (AOM-SR) is a biological process mediated by anaerobic methanotrophs (ANME) and sulfate reducing bacteria. Due to its relevance in regulating the global carbon cycle and potential biotechnological application for treating sulfate-rich wastewater, AOM-SR has drawn attention from the scientific community. However, the detailed knowledge on ANME community, its physiology and metabolic pathway are scarcely available, presumably due to the lack of either pure cultures or the difficulty to enrich the biomass. To enhance the recent knowledge on ANME distribution and enrichment conditions, this research investigated AOM-SR with the following objectives: (i) characterize the microbial communities responsible for AOM in marine sediment, (ii) enrich ANME in different bioreactor configurations, i.e. membrane bioreactor (MBR), biotrickling filter (BTF) and high pressure bioreactor (HPB), and (iii) assess the AOM-SR activity under different pressure and temperature conditions.The microbes inhabiting coastal sediments from Marine Lake Grevelingen (the Netherlands) was characterized and the ability of the microorganisms to carry out AOM-SR was assessed. By performing batch activity tests for over 250 days, AOM-SR was evidenced by sulfide production and the concomitant consumption of sulfate and methane at approximately equimolar ratios and a sulfate reduction rate of 5 µmol sulfate per gram dry weight per day was attained. Sequence analysis of 16S rRNA genes showed the presence of ANME-3 in the Marine Lake Grevelingen sediment.Two bioreactor configurations, i.e. MBR and BTF were operated under ambient conditions for 726 days and 380 days, respectively, to enrich the microorganisms from Ginsburg Mud Volcano performing AOM. The reactors were operated in fed-batch mode for the liquid phase with a continuous supply of gaseous methane. In the MBR, an external ultra-filtration membrane was used to retain the biomass, whereas, in the BTF, biomass retention was achieved via biomass attachment to the packing material. AOM-SR was recorded only after ~ 200 days in both bioreactor configurations. The BTF operation showed the enrichment of ANME in the biofilm by Illumina Miseq method, especially ANME-1 (40%) and ANME-2 (10%). Interestingly, in the MBR, aggregates of ANME-2 and Desulfosarcina were visualized by CARD-FISH. Acetate production was observed in the MBR, indicating that acetate was a possible intermediate of AOM. Although both bioreactor configurations showed good performance and resilience capacities for AOM enrichment, the sulfate reduction rate was slightly higher and faster in the BTF (1.3 mM day-1 at day 280) than the MBR (0.5 mM day-1 at day 380).In order to simulate cold seep conditions and differentiate the impact of environmental conditions on AOM activities, sediment highly enriched with the ANME-2a clade was incubated in HPB at different temperature (4, 15 and 25 oC at 100 bar) and pressure (20, 100, 200 and 300 bar at 15 oC) conditions. The incubation at 100 bar pressure and 15 oC was observed to be the most suitable condition for the ANME-2a phylotype, which is similar to in-situ conditions where the biomass was sampled, i.e. Captain Aryutinov Mud Volcano, Gulf of Cadiz. The incubations at 200 and 300 bar pressures showed the depletion in activities after 30 days of incubation. Incubation of AOM hosting sediment at in-situ condition could be a preferred option for achieving high AOM activities and sulfate reduction rates.In this thesis, it has been experimentally demonstrated that biomass retention and the continuous supply of methane can favor the growth of the slow growing anaerobic methane oxidizing community in bioreactors even under ambient conditions. Therefore, locating ANME habitats in shallow environments and enriching them at ambient conditions can be advantageous for future environmental biotechnology applications

On retrouve des contaminations d’aquifèr à l’arsenic dans touts les deltaï de l'Asie du Sud-Est, y compris dans le delta du Mékong, ce qui affecte la santé de millions de personnes. L’arsenic est très sensible aux fluctuations des conditions redox qui sont générés par les cycles alternés humides/secs pendant la saison de mousson. Une étude sur les caractéristiques géophysiques et chimiques du sol et des eaux souterraines dans le district de An Phu, dans le haut du delta du Mékong au Vietnam, suggère une forté contamination à l’As dans cette région. Les données chimiques et géophysiques indiquent une forte corrélation entre concentrations dans les eaux souterraines anoxiques et conductivité des sols. La liberation de l’arsenic est associée à la dissolution réductrice induih par des microorganisms des colloïdes et (oxyhydr)oxydes de fer dans des conditions d'oxydo-réduction oscillantes. La présence de bactéries sulforéductrices a le potentiel de stabiliser l’arsenic dans la phase solide et de l’atténuer dans la phase aqueuse par adsorption / désorption de l’arsenic sur les (oxyhydr)oxydes, et / ou sulfures de fer via la formation de complexes thiols. En raison de la teneur en pyrite élevée dans les sédiments, l'oxydation de la pyrite peut abaisser le pH et conduire à l'inhibition de la réduction microbienne du sulfate et aime empêcher la séquestration de l’arsenic dissous. Bien que le cycle biogéochimique de l’arsenic dans un système dynamique d’oxydoréduction soit une problématique complexe, il a été possible de renforcer notre compréhension de ce système / Aquifer arsenic (As) contamination is occuring throughout deltaic areas of Southeast Asia, including the Mekong Delta, and affects the health of millions of people. As is highly sensitive to fluctuations of redox conditions which are generated by the alternating wet-dry cycles during the monsoonal seasons. A survey of geophysical and chemical characteristics of soil and groundwater in the An Phu district, located in the vicinity of the Mekong Delta in Vietnam, shows the occurrence high As aqueous concentration in this region. Chemical and geophysical data indicate a strong positive correlation between As concentrations in the anoxic groundwater and conductivity of soils. In addition, mechanisms of As release are shown to be associated with colloidal and iron (oxyhydr)oxides which undergo microbial mediated reductive dissolution under redox oscilatting conditions. The presence of sulfate microbial reduction potentially stabilizes As in the solid phase and diminish As in the aqueous phase through the adsorption/desorption of As onto iron (oxyhydr)oxides and/ or sulfides with formation of thiols complexes in solid phase. Because of the high pyrite content in sediment, pyrite oxidation may drop in pH values, leads to inhibition of sulfate reducing bacteria and reduces sequestration of dissolved As. Although the biogeochemical cycling of redox sensitive species such as As in dynamic systems is challenging, it has been possible to strengthen our collective understanding of such system.

No description available.

Os efeitos das relações DQO/sulfato e das variações progressivas da concentração de sulfato sobre o desempenho de um reator anaeróbio horizontal de leito fixo (RAHLF) em escala de bancada, tratando substrato sintético submetido a aumentos na concentração de sulfato afluente, foram investigados. O substrato sintético foi composto por glicose, acetato de amônio, bicarbonato de sódio e soluções nutricionais de sais e metais traços. O reator foi preenchido com matrizes cúbicas de espuma de poliuretano para imobilização da biomassa. A demanda química de oxigênio (DQO) no afluente foi de cerca de 2435 '+ OU -' 632 mg/L ao longo dos experimentos, enquanto a concentração de sulfato afluente foi progressivamente aumentada de 28 para 1000 e 2000 mg/L, resultando em relações DQO/sulfato de 87, 2,4 e 1,22, respectivamente, nas quatro etapas experimentais avaliadas. Sob relação DQO/sulfato de 87 houve indicações de sintrofismo entre microrganismos metanogênicos (MM) e microrganismos redutores de sulfato (MRS). Na relação DQO/sulfato de 2,4 houve predomínio da redução de sulfato, e portanto dos MRS, enquanto na relação DQO/sulfato de 1,22 houve limitação da redução de sulfato, indicando provável predomínio de MM sobre MRS, devida a limitações de biomassa ou de matéria orgânica disponível, ou de transferência de massa para o sulfato. Entretanto, metanogênese e redução de sulfato não foram processos excludentes. De maneira a melhorar a separação líquido-gás, uma nova configuração segmentada foi internamente testada no reator, de modo que o mesmo fosse capaz de atingir e manter o estado de equilíbrio dinâmico aparente / The effects of the COD to sulfate ratio and of the progressive variations of sulfate concentrations on the performance of a bench-scale horizontal-flow anaerobic immobilized sludge (HAIS) reactor treating a synthetic substrate under increasing sulfate concentrations was investigated. The synthetic substrate was composed of glucose, ammonium acetate, sodium bicarbonate and trace metal nutritional solution. The reactor was filled with polyurethane foam cubic matrices for biomass immobilization. Influent chemical oxigen demand (COD) was kept almost constant along the experiments (2453 '+ OR -' 632 mg/L) while the influent sulfate concentration was increased from 28 to 1000 and 2000 mg/L, resulting in COD/'SO IND.4 POT.-2' ratios of 87; 2,4; and 1,22, respectively, in the four experimental phases assayed. Under COD/'SO IND.4 POT.-2' ratio of 87, there was indication of syntrophism between methanogenic microorganisms (MM) and sulfatereducing microorganisms (SRM). Under COD/'SO IND.4 POT.-2' ratio of 2,4, there was a sulfate reduction predominance and therefore, of SRM, while under COD/'SO IND.4 POT.-2' of 1,22, there was a sulfate reduction limitation, that probably indicates a MM predominance over SRM, due to biomass limitation, or available organic matter limitation, or sulfate mass transfer limitation. Meanwhile, there was no exclusion between methanogenesis and sulfate reduction processes. In order to improve better liquid-gas separation, a new staged configuration was tested inside the reactor, so that it was able to reach and to maintain the dynamic steady-state equilibrium

Solid wastes containing sulfate, such as construction and demolition debris (CDD), are an important source of pollution, which can create a lot of environmental problems. It is suggested that these wastes have to be separated from other wastes, especially organic waste, and place it in a specific area of the landfill. This results in the rapid rise of the disposal costs of these gypsum wastes. Although these wastes can be reused as soil amendment or to make building materials, a concern has been raised by regulators regarding the chemical characteristics of the material and the potential risks to human health and the environment due to CDD containing heavy metals and a high sulfate content. Soils containing gypsum, namely gypsiferous soils, also have several problems during agricultural development such as low water retention capacity, shallow depth to a hardpan and vertical crusting. In some mining areas, gypsiferous soil problems occur, coupled with acid mine drainage (AMD) problems which cause a significant environmental threat. Reduction of the sulfate content of these wastes and soils is an option to overcome the above mentioned problems. This study aimed to develop sulfate removal systems to reduce the sulfate content of CDD and gypsiferous soils in order to decrease the amount of solid wastes as well as to improve the quality of wastes and soils for recycling purposes or agricultural applications. The treatment concept leaches the gypsum contained in the CDD by water in a leaching step. The sulfate containing leachate is further treated in biotic or abiotic systems. Biological sulfate reduction systems used in this research were the Upflow Anaerobic Sludge Blanket (UASB) reactor, Inverse Fluidized Bed (IFB) Reactor and Gas Lift Anaerobic Membrane Bioreactor (GL-AnMBR). The highest sulfate removal efficiency achieved from these three systems ranges from 75 to 95%. The treated water from the bioreactor can then be reused in the leaching column. Chemical sulfate removal (abiotic system) is an alternative option to treat the CDD leachate. Several chemicals were tested including barium chloride, lead(II) nitrate, calcium chloride, calcium carbonate, calcium oxide, aluminium oxide and iron oxide coated sand. A sulfate removal efficiency of 99.9% was achieved with barium chloride and lead(II) nitrate.For AMD and gypsiferous soils treatment, five types of organic substrate including bamboo chips (BC), municipal wastewater treatment sludge (MWTS), rice husk (RH), coconut husk chip (CHC) and pig farm wastewater treatment sludge (PWTS) were tested as electron donors for biological sulfate reduction treating AMD. The highest sulfate reduction efficiency (84%) was achieved when using the combination of PWTS, RH and CHC as electron donors. Then, this organic mixture was further used for treatment of the gypsiferous soils. The gypsum mine soil (overburden) was mixed with an organic mixture in different amounts including 10, 20, 30 and 40% of soil. The highest sulfate removal efficiency of 59% was achieved in the soil mixture which contained 40% organic material.The removal of sulfide from the effluent of the biological sulfate reduction process is required as sulfide can cause several environmental impacts or be re-oxidized to sulfate if directly discharged to the environment. Electrochemical treatment is one of the alternatives for sulfur recovery from aqueous sulfide. A non-catalyzed graphite electrode was tested as electrode for the electrochemical sulfide oxidation. A high surface area of the graphite electrode is required in order to have less internal resistance as much as possible. The highest sulfide oxidation rate was achieved when using the external resistance at 30 Ω at a sulfide concentration of 250 mg L-1