Neste trabalho avaliou-se a influência das condições operacionais da célula a combustível microbiana (CCM) na remoção de matéria orgânica de águas residuárias e na geração de energia elétrica direta. As Hipóteses 1, 2 e 3 verificaram respectivamente as influências do tempo de detenção hidráulica (TDH), das condições mesofílica (25 ºC) e termofílica (55 ºC) de temperatura e da razão de recirculação (R) do efluente no cátodo da CCM (0, 1, 3 e 5) na geração de energia elétrica, na adesão e na comunidade microbiana e na remoção de DQO em CCM sem membrana de íon seletiva alimentada com água residuária sintética a base de sacarose. As Hipóteses 1, 2 e 3 foram aceitas. A redução do TDH permitiu maior geração de energia e dominância na comunidade microbiana e menor adesão da comunidade microbiana ao eletrodo. Enquanto que longos TDH removeram mais DQO, porém geraram menores valores de tensão elétrica. As condições termofílicas apresentaram maiores valores de tensão elétrica gerada e maior dominância da comunidade microbiana e menor adesão microbiana ao eletrodo e eficiência de remoção de DQO. A constante cinética aparente em condição termofílica ( 0,035 h-1) foi duas vezes menor que em condição mesofílica ( 0,083 h-1). O aumento da R melhorou a geração de energia e a remoção de DQO, pois houve melhor transferência de massa do meio líquido para os microrganismos e do meio gasoso para liquido e menor concentração de biomassa aderida ao eletrodo do cátodo aumentando a tensão elétrica gerada. Na Hipótese 4, verificou-se o uso e o efeito do TDH no tratamento de vinhaça de cana de açúcar em CCM sem membrana trocadora de íon seletivo operada em condição termofílica. A CCM foi capaz de remover a matéria orgânica da vinhaça de cana de açúcar e gerar energia elétrica direta, validando a Hipótese 4. As hipóteses 5, 6 e 7 avaliaram as influências da relação DQO, nitrogênio e fósforo da água residuária de produção de vinho, do tempo de retenção celular (TRC) e da configuração do eletrodo no desempenho de CCM de duas câmaras usando membrana de íon seletivo. Acataram-se as hipóteses 5, 6 e 7. O desbalanceamento entre DQO, nitrogênio e fósforo da água residuária de produção de vinho é um dos principais obstáculos para o uso desta tecnologia e a relação de DQO:N:P de 700:10:1 tem elevado potencial para gerar energia elétrica direta em CCM, embora não seja eficiente na remoção de matéria orgânica. A geração de energia aumenta com a redução do TRC, visto que há seleção dos microrganismos eletrogênicos e aumento da carga orgânica volumétrica específica reduzindo a competição por substrato. Entretanto, o TRC não influenciou a remoção de matéria orgânica, pois somente uma pequena parte da DQO foi removida similar em todos os TRC. As características físicas do eletrodo como a porosidade, a rugosidade e a densidade de área do eletrodo e a biocompatibilidade do eletrodo são fatores determinantes para aumentar o desempenho da CCM. Entre os eletrodos estudados, o feltro de carbono foi o melhor material encontrado. / In this work the influence of the operational conditions of the microbial fuel cell (MFC) were evaluated in organic matter removal from wastewater treatment and in the power generation. Hypotheses 1, 2 and 3 respectively checked the influences of hydraulic retention time (HRT), of mesophilic and thermophilic conditions (25 °C and 55 °C, respectively) and the recirculation ratio (R) of the effluent in cathode of MFC (0, 1, 3 and 5) in the power generation, microbial adhesion and community and COD removal of membraneless MFC fed with synthetic wastewater based on sucrose. Hypotheses 1, 2 and 3 have been accepted. Reducing the HRT increased the power generation and the dominance in microbial community and decreased the COD removal efficiency and microbial adhesion to the electrode. Long HRT more efficiently removed the organic matter but generated lower voltages. The thermophilic conditions yielded a more dominant microbial community that favored power generation compared with the mesophilic conditions because of reduced microbial adhesion to the electrode. The COD removal efficiencies were higher under mesophilic conditions than under thermophilic conditions due to the higher apparent kinetic constant at mesophilic conditions (0.083 h-1) than in thermophilic conditions (0.035 h-1). Increasing the R improved the power generation and the COD removal, because the mass transfer in the liquid medium for microorganisms was improved and the biomass adhered to the cathode electrode decreased increasing the voltage. In Hypothesis 4, the use and effect of HRT in treating sugar cane vinasse in membraneless MFC operated at thermophilic conditions were evaluated. The CCM was able to remove the COD of sugarcane vinasse and generate electricity directly, confirming the hypothesis 4. Hypotheses 5, 6 and 7 assessed the influences of COD, nitrogen and phosphorus ratio in winery wastewater, of sludge retention time (SRT) and of electrode configuration in dual chamber MFC. Hypotheses 5, 6 and 7 were adopted. The misbalance between COD, nitrogen and phosphorus from winery wastewater is a major obstacle to the use of this technology and COD:N:P ratio of 700:10:1 had high potential to generate power in MFC, although it is not effective in removing organic matter. The power generation increases with the reduction of the SRT, since there were the selection of bioeletrogenic microorganisms and increased the volumetric organic load rate reducing competition for substrate. However, the SRT did not affect the removal of organic matter, because only a small part of COD was removed regardless of SRT. Physical characteristics of the electrode as porosity, roughness and the electrode area density and the biocompatibility of the electrode are key factors to increase the performance of CCM. The carbon felt was the best studied material having the highest values of porosity, roughness and the electrode area density.

De multiples micro-organismes ont la capacité de catalyser l’oxydation électrochimique de matières organiques en s’organisant en biofilm à la surface d’anodes. Ce processus est à la base de procédés électro-microbiens très innovants tels que les piles à combustible microbiennes ou les électrolyseurs microbiens. L’interface biofilm/électrode a été l’objet de nombreuses étudesdont les conclusions restent difficiles à démêler en partie du fait de la diversité des paramètres interfaciaux mis en jeu. L’objet de ce travail de thèse est d’exploiter les technologies microsystèmes pour focaliser l’impact de la topographie de surface des électrodes sur le développement du biofilm et sur ses performances électro-catalytiques. La formation de biofilmsélectroactifs de Geobacter sulfurreducens a été étudiée sur des électrodes d’or présentant des topographies bien contrôlées, sous la forme de rugosité, porosité, réseau de piliers, à des échellesallant du nanomètre à quelques centaines de micromètres. La présence de microrugosité a permis d’accroitre les densités de courant d’un facteur 8 par rapport à une surface lisse et son effet a étéquantifié à l’aide du paramètre Sa. Nous avons tenté de distinguer les effets des différentes échelles de rugosité sur le développement du biofilm et la vitesse des transferts électroniques.L’intérêt de la microporosité a été discuté. L’accroissement de surface active par la présence de micro-piliers s’est avéré très efficace et une approche théorique a donné des clés de compréhension et d’optimisation. Les connaissances acquises dans les conditions de culture pure ont finalement été confrontées avec la mise en oeuvre de biofilms multi-espèces issus d’un inoculum complexe provenant de sédiments marins. / Many microorganisms have the ability to catalyze the electrochemical oxidation of organic matterby self-organizing into biofilm on the surface of anodes. This process is the basis of highlyinnovative electro-microbial processes such as microbial fuel cells or microbial electrolysis cells.The biofilm/electrode interface has been the subject of numerous studies whose conclusionsremain difficult to disentangle partly because of the diversity of the interfacial parameters involved.The purpose of this thesis work is to exploit microsystem technologies to focus the impact ofelectrode surface topography on biofilm development and electro-catalytic performance. Theformation of electroactive biofilms of Geobacter sulfurreducens was studied on gold electrodespresenting well-controlled topographies, in the form of roughness, porosity, pillar networks, atscales ranging from nanometer to a few hundred micrometers. The presence of micro-roughnessincreased the current densities by a factor of 8 compared to a smooth surface and its effect wasquantified using the Sa parameter. We have tried to distinguish the effects of different roughnessscales on biofilm development and electron transfer rates. The suitability of micro-porosity wasdiscussed. The increase of active surface area by the presence of micro-pillars has proved veryeffective and a theoretical approach has given keys to understanding and optimization. Theknowledge acquired under pure culture conditions was finally confronted with the use of multispeciesbiofilms formed from a complex inoculum coming from marine sediments.

Une Pile à Combustible Microbienne (PCM) convertit l’énergie chimique issue de l’oxydation de la matière organique directement en énergie électrique. L’oxydation du combustible est assurée par un biofilm dit « électroactif » se développant à la surface de l’anode et jouant le rôle de catalyseur microbien. L’anode microbienne formée à partir d’un consortium bactérien, issu dans cette étude de terreau de jardin, est associée à une cathode à air abiotique à la surface de laquelle se produit la réduction de l’oxygène. L’assemblage d’une anode microbienne et d’une cathode à air abiotique pour construire une PCM est un réel challenge tant les conditions optimales de chacune sont différentes. Ces travaux de thèse ont donc pour objectif d'anticiper le fonctionnement global de la PCM pour concevoir une anode microbienne et une cathode abiotique capables de fonctionner ensemble de façon optimale. Une partie expérimentale conséquente vise à concevoir une PCM optimale en menant des essais sur différents designs de réacteur. Un modèle numérique, basé sur l’expérimentation et calculant les distributions secondaires de courant et de potentiel au sein de la PCM, vient compléter l’étude expérimentale afin d’optimiser l’architecture de la PCM et maximiser les performances délivrées. La configuration « Assemblage Séparateur-Electrodes » consiste à intercaler le séparateur entre la bioanode et la cathode à air dans le but de diminuer la résistance interne du système. Ce design a permis de concevoir des PCMs délivrant d’excellentes performances jusqu’à 6.42 W.m-2. In fine, le prototype « Bioelec », utilisé comme modèle de démonstration, est réalisé à l’échelle du laboratoire avec un assemblage en série et en parallèle de plusieurs PCMs élaborées avec cette configuration « ASE ». / A Microbial Fuel Cell (MFC) can convert the chemical energy contained in low-cost organic matter directly into electrical energy. The oxidation of organic matter is performed by a biofilm known as “electroactive” that develops on the anode surface and acts as a microbial catalyst. The microbial anode, formed from indigenous bacteria of compost leachate, is combined with an abiotic air-cathode catalyzing the reduction of oxygen. The association of a bioanode and an abiotic air-cathode in an MFC is a major challenge as their optimal conditions are so divergent. The purpose of this PhD work is to anticipate the global mechanisms of an MFC in order to develop a microbial anode and an abiotic air-cathode able to operate together in an optimal way. A consequent experimental part aims to develop an optimal MFC by carrying out tests on several reactor designs. A numerical model, based on the experimental results, calculates the secondary distributions of current and potential in the cell. The model supports the experimental study and is used to optimize the MFC architecture and maximize the delivered performances. The configuration “Separator-Electrodes Assembly” consists of sandwiching the separator between the bioanode and the air-cathode in order to decrease the internal resistance of the system. This design provided excellent results as MFCs delivered great power densities up to 6.42 W.m-2. Finally, a prototype “Bioelec”, used as a demonstrative model, was built with several MFCs connected in series or in parallel, each of them designed with the “ASE” configuration.

Neste trabalho avaliou-se a influência das condições operacionais da célula a combustível microbiana (CCM) na remoção de matéria orgânica de águas residuárias e na geração de energia elétrica direta. As Hipóteses 1, 2 e 3 verificaram respectivamente as influências do tempo de detenção hidráulica (TDH), das condições mesofílica (25 ºC) e termofílica (55 ºC) de temperatura e da razão de recirculação (R) do efluente no cátodo da CCM (0, 1, 3 e 5) na geração de energia elétrica, na adesão e na comunidade microbiana e na remoção de DQO em CCM sem membrana de íon seletiva alimentada com água residuária sintética a base de sacarose. As Hipóteses 1, 2 e 3 foram aceitas. A redução do TDH permitiu maior geração de energia e dominância na comunidade microbiana e menor adesão da comunidade microbiana ao eletrodo. Enquanto que longos TDH removeram mais DQO, porém geraram menores valores de tensão elétrica. As condições termofílicas apresentaram maiores valores de tensão elétrica gerada e maior dominância da comunidade microbiana e menor adesão microbiana ao eletrodo e eficiência de remoção de DQO. A constante cinética aparente em condição termofílica ( 0,035 h-1) foi duas vezes menor que em condição mesofílica ( 0,083 h-1). O aumento da R melhorou a geração de energia e a remoção de DQO, pois houve melhor transferência de massa do meio líquido para os microrganismos e do meio gasoso para liquido e menor concentração de biomassa aderida ao eletrodo do cátodo aumentando a tensão elétrica gerada. Na Hipótese 4, verificou-se o uso e o efeito do TDH no tratamento de vinhaça de cana de açúcar em CCM sem membrana trocadora de íon seletivo operada em condição termofílica. A CCM foi capaz de remover a matéria orgânica da vinhaça de cana de açúcar e gerar energia elétrica direta, validando a Hipótese 4. As hipóteses 5, 6 e 7 avaliaram as influências da relação DQO, nitrogênio e fósforo da água residuária de produção de vinho, do tempo de retenção celular (TRC) e da configuração do eletrodo no desempenho de CCM de duas câmaras usando membrana de íon seletivo. Acataram-se as hipóteses 5, 6 e 7. O desbalanceamento entre DQO, nitrogênio e fósforo da água residuária de produção de vinho é um dos principais obstáculos para o uso desta tecnologia e a relação de DQO:N:P de 700:10:1 tem elevado potencial para gerar energia elétrica direta em CCM, embora não seja eficiente na remoção de matéria orgânica. A geração de energia aumenta com a redução do TRC, visto que há seleção dos microrganismos eletrogênicos e aumento da carga orgânica volumétrica específica reduzindo a competição por substrato. Entretanto, o TRC não influenciou a remoção de matéria orgânica, pois somente uma pequena parte da DQO foi removida similar em todos os TRC. As características físicas do eletrodo como a porosidade, a rugosidade e a densidade de área do eletrodo e a biocompatibilidade do eletrodo são fatores determinantes para aumentar o desempenho da CCM. Entre os eletrodos estudados, o feltro de carbono foi o melhor material encontrado. / In this work the influence of the operational conditions of the microbial fuel cell (MFC) were evaluated in organic matter removal from wastewater treatment and in the power generation. Hypotheses 1, 2 and 3 respectively checked the influences of hydraulic retention time (HRT), of mesophilic and thermophilic conditions (25 °C and 55 °C, respectively) and the recirculation ratio (R) of the effluent in cathode of MFC (0, 1, 3 and 5) in the power generation, microbial adhesion and community and COD removal of membraneless MFC fed with synthetic wastewater based on sucrose. Hypotheses 1, 2 and 3 have been accepted. Reducing the HRT increased the power generation and the dominance in microbial community and decreased the COD removal efficiency and microbial adhesion to the electrode. Long HRT more efficiently removed the organic matter but generated lower voltages. The thermophilic conditions yielded a more dominant microbial community that favored power generation compared with the mesophilic conditions because of reduced microbial adhesion to the electrode. The COD removal efficiencies were higher under mesophilic conditions than under thermophilic conditions due to the higher apparent kinetic constant at mesophilic conditions (0.083 h-1) than in thermophilic conditions (0.035 h-1). Increasing the R improved the power generation and the COD removal, because the mass transfer in the liquid medium for microorganisms was improved and the biomass adhered to the cathode electrode decreased increasing the voltage. In Hypothesis 4, the use and effect of HRT in treating sugar cane vinasse in membraneless MFC operated at thermophilic conditions were evaluated. The CCM was able to remove the COD of sugarcane vinasse and generate electricity directly, confirming the hypothesis 4. Hypotheses 5, 6 and 7 assessed the influences of COD, nitrogen and phosphorus ratio in winery wastewater, of sludge retention time (SRT) and of electrode configuration in dual chamber MFC. Hypotheses 5, 6 and 7 were adopted. The misbalance between COD, nitrogen and phosphorus from winery wastewater is a major obstacle to the use of this technology and COD:N:P ratio of 700:10:1 had high potential to generate power in MFC, although it is not effective in removing organic matter. The power generation increases with the reduction of the SRT, since there were the selection of bioeletrogenic microorganisms and increased the volumetric organic load rate reducing competition for substrate. However, the SRT did not affect the removal of organic matter, because only a small part of COD was removed regardless of SRT. Physical characteristics of the electrode as porosity, roughness and the electrode area density and the biocompatibility of the electrode are key factors to increase the performance of CCM. The carbon felt was the best studied material having the highest values of porosity, roughness and the electrode area density.

Les biofilms électroactifs (EA) sont des consortia de bactéries mono- ou multi-espèces qui ont la capacité de catalyser des réactions électrochimiques en échangeant des électrons avec les électrodes sur lesquelles ils se développent. Les biofilms EA ont ouvert la voie à de nombreux procédés électrochimiques innovants, l’exemple le plus connu étant la pile à combustible microbienne. Dans ce cadre, des électrodes tridimensionnelles poreuses sont couramment mises en oeuvre afin d’offrir aux biofilms EA une surface maximale pour se développer. Toutefois, à ce jour les études théoriques qui permettraient de guider l’élaboration de ces électrodes restent très peu nombreuses. Une synthèse bibliographique a mis en évidence l’importance cruciale de la taille des pores et a montré que des pores de l’ordre du millimètre conduisent aux densités de courant les plus élevées. La première partie de la thèse a donc été consacrée à caractérise l’impact de la taille des pores, entre 1 à 5 mm, sur le développement et les performances électrochimiques d’un biofilm EA multiespèces. Ces tailles permettent la colonisation microbienne sur plusieurs centimètres de profondeur et favorisent la stabilité du courant à long terme. Par contre, l’effet limitant des transferts de matière est significatif, particulièrement pour ce qui concerne les espèces tampon. Enfin, un découplage est mis en évidence entre la colonisation qui se déploie sur plusieurs semaines et l’établissement du courant qui se réalise en quelques jours seulement. Un second dispositif expérimental a mis en évidence une sélection des populations microbiennes en fonction des longueurs de pore de 5 à 24 mm. La deuxième partie de la thèse se focalise sur l’étude des premiers instants de formation du biofilm électroactif à la surface d’une électrode. Une tentative d’identification des mécanismes impliqués dans le mouvement des bactéries électroactives vers l’électrode est proposée. / Electroactive (EA) biofilms refer to single- or multi-species bacterial consortia, which have theability to catalyse electrochemical reactions by exchanging electrons with the electrodes on whichthey develop. EA biofilms have paved the way for many innovative electrochemical processes, themost well-known example is microbial fuel cell. In this context, 3-dimensional porous electrodesare commonly used to offer EA biofilms a maximum surface area for development. However, todate, very few theoretical studies have been carried out to guide the development of theseelectrodes. A bibliographic synthesis highlighted the importance of the pore size and indicated thatpore sizes of the order of a few millimetres lead to the highest current densities. The first part ofthe thesis was therefore devoted to characterizing the impact of size, between 1 and 5 mm, on thedevelopment and electrochemical performance of a multi-species EA biofilm. These sizes allowmicrobial colonization several centimetres deep and promote long-term current stability. However,limiting effect of the mass transfer is significant, particularly for the buffer species. Finally, adecoupling is highlighted between the colonisation, which takes place over several weeks, and theestablishment of the current which takes a few days only. A second experimental set up showsthat a selection occurs on the microbial populations in function of pore lengths from 5 to 24 mm.The second part of the thesis focuses on the study of the early stages of the EA biofilm formation at the electrode surface. In particular, an attempt to identify the mechanisms involved in the electroactive bacteria movement towards the electrode is proposed.

A long-held practice is to mix agricultural soil with a soil amendment to improve growing conditions in crops. A common soil amendment is biosolids produced from both municipal and dairy wastewater due to the macro- and micronutrients within it. Both the agricultural and wastewater industries are participating in the Circular Economy concept (CEC). Two experiments explored using expended bioelectrochemical systems (BES) that treated either synthetic dairy wastewater (DWW) or synthetic municipal wastewater (SWW) as soil amendments to improve corn plant growth when treated with three different nutrient treatments: 100%- 50%- and 0% Hoagland Nutrient Solutions. Biochar and used terracotta clay were used as soil amendments too. Additionally, the DWW and SWW soil amendments are being invested to see if soil moisture can be retained during simulated drought conditions. The experiments took place in the late fall and winter of 2021 and summer of 2022 in Starkville, Mississippi.

Landfill leachate contains valuable, recoverable organics, water, and nutrients. This project investigated leachate treatment and resource recovery from landfill leachates by innovative methods such as forward osmosis (FO), bioelectrochemical systems (BES), and advanced oxidation. In this study, a microbial fuel cell (MFC) removed 50-75% of the ammonia from a leachate through the electricity driven movement of ammonium to the cathode chamber followed by air stripping at high pH (> 9). During this process, the MFC system removed 53-64% of the COD, producing a net energy of 0.123 kWh m-3. Similarly, an integrated microbial desalination cell (MDC) in an FO system recovered 11-64% of the ammonia from a leachate; this was affected by current generation and hydraulic retention time in the desalination chamber. The MDC-FO system recovered 51.5% of the water from a raw leachate. This increased to 83.5% when the FO concentrate was desalinated in the MDC and then recirculated through the FO unit. In addition, the project investigated humic acid (HA) recovery from leachate during the synergistic incorporation of FO, HA recovery, and Fenton's oxidation to enhance leachate treatment and to reduce Fenton's reagent requirements. This led to the investigation of harmful disinfection byproducts (DBPs) formation during Fenton's oxidation of landfill leachate. The removal of leachate UV-quenching substances (humic, fulvic, and hydrophilic acids) using an MFC and a chemical oxidant (i.e., sodium percarbonate) with a focus on energy production and cost efficiency were also studied. BES treatment can reduce leachate organics concentrations; lower UV absorbance; recover ammonia; and, in combination with FO, recover water. Although BES is promising, significant work is needed before its use in landfill leachate becomes practical. FO application to leachate treatment must consider the choice of an appropriate draw solute, which should require minimal effort for regeneration. Resources like HA in leachate deserve more attention. Further efforts can focus on purification and application of the recovered products. The emerging issue of DBP formation in leachate treatment also requires attention due to the potential environmental and human health effects. The broader impact of this study is the societal benefit from more sustainable and cost-efficient leachate treatment. / Doctor of Philosophy / On average, each of us produces 3 – 4 pounds of solid waste every day. In the U.S., the yearly generation of solid waste is 250 million tons, while the global generation is 1.1 billion tons. The global management cost of solid waste is around 200 billion dollars. About half of U.S. municipal solid waste ends up in landfills, in China, this number is 80%. Among the different municipal solid waste (MSW) management approaches, landfilling is the most common because of its low cost and relatively low maintenance requirements. In a landfill, the combination of precipitation and solid waste degradation produce leachate, a complex wastewater. A ton of municipal solid waste can generate 0.05–0.2 tons of leachate in its lifetime during the process of landfilling. Leachate contains a vast array of pollutants, which can result in major environmental impact and adverse human health risk if not contained and treated appropriately. At present, leachate is mostly treated biologically, without any resource recovery. Among the myriad recoverable resources in landfill leachates, water and ammonia are the most abundant. We applied innovative approaches such as, bioelectrochemical systems, forward osmosis, advanced oxidation to recover resources and remove contaminants from leachate simultaneously. We also incorporated these novel technologies to help each other. For instance, we recovered humic fertilizer from leachate prior to advanced oxidation (i.e., Fenton’s oxidation) that helped the reduction of Fenton’s reagent requirements. The next step of our study could be the pilot scale application of the proposed techniques so that it can be applied in field. The broader impacts of this study include improvements in sustainability and cost efficiency of leachate treatment that can benefit the society.