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This study compared two anammox sequencing batch reactors (SBR) for one year. SBRconstantT was kept at 30 degrees C while temperature in SBRloweringT was decreased step-wise from 30 degrees C to 20 degrees C and 15 degrees C followed by over 140 days at 12.5 degrees C and 10 degrees C. High retention of anammox bacteria (AnAOB) and minimization of competition with AnAOB were key. 5-L anoxic reactors with the same inoculum were fed synthetic influent containing 25.9 mg NH4+-N/L and 34.1 mg NO2--N/L (no COD). Specific ammonium removal rates continuously increased in SBRconstantT, reaching 785 mg NH4+-N/gVSS/d, and were maintained in SBRloweringT, reaching 82.2 and 91.8 mg NH4+-N/gVSS/d at 12.5 and 10 degrees C respectively. AnAOB enrichment (increasing hzsA and 16S rDNA gene concentrations) and adaptation (shift from Ca. Brocadia to Ca. Kuenenia in SBRloweringT) contributed to these high rates. Rapidly settling granules developed, with average diameters of 1.2 (SBRconstantT) and 1.6 mm (SBRloweringT). Results reinforce the potential of anammox for mainstream applications.

In this work, we focus on the anaerobic digestion model no 1 proposed by I.W.A. working group (Batstone et al. 2002) as a basis for the development of a comprehensive distributed parameter model, which combined ADM1’s kinetics of biomass growth and substrate transformation with axial dispersion material balances. Then we present a two-step procedure to validate the simulations using the software COMSOL MULTIPHYSICS to resolve the complex system of PDEs. It is based on situations in which solutions must be approached from those of the homogeneous system. Then we study the influence of certain operational parameters such as residence time on the performance of the reactor.

Background Volatile fatty acid intoxication (acidosis), a common process failure recorded in anaerobic reactors, leads to drastic losses in methane production. Unfortunately, little is known about the microbial mechanisms underlining acidosis and the potential to recover the process. In this study, triplicate mesophilic anaerobic reactors of 100 L were exposed to acidosis resulting from an excessive feeding with sugar beet pulp and were compared to a steady-state reactor. Results Stable operational conditions at the beginning of the experiment initially led to similar microbial populations in the four reactors, as revealed by 16S rRNA gene T-RFLP and high-throughput amplicon sequencing. Bacteroidetes and Firmicutes were the two dominant phyla, and although they were represented by a high number of operational taxonomic units, only a few were dominant. Once the environment became deterministic (selective pressure from an increased substrate feeding), microbial populations started to diverge between the overfed reactors. Interestingly, most of bacteria and archaea showed redundant functional adaptation to the changing environmental conditions. However, the dominant Bacteroidales were resistant to high volatile fatty acids content and low pH. The severe acidosis did not eradicate archaea and a clear shift in archaeal populations from acetotrophic to hydrogenotrophic methanogenesis occurred in the overfed reactors. After 11 days of severe acidosis (pH 5.2 ± 0.4), the process was quickly recovered (restoration of the biogas production with methane content above 50 %) in the overfed reactors, by adjusting the pH to around 7 using NaOH and NaHCO3. Conclusions In this study we show that once the replicate reactors are confronted with sub-optimal conditions, their microbial populations start to evolve differentially. Furthermore the alterations of commonly used microbial parameters to monitor the process, such as richness, evenness and diversity indices were unsuccessful to predict the process failure. At the same time, we tentatively propose the replacement of the dominant Methanosaeta sp. in this case by Methanoculleus sp., to be a potential warning indicator of acidosis. Electronic supplementary material The online version of this article (doi:10.1186/s13068-015-0309-9) contains supplementary material, which is available to authorized users.

Procédé de traitement d'effluents chargés en azote ammoniacal dans un réacteur à chambre unique (R), pour en éliminer l'azote ammoniacal, selon lequel : on prévoit dans le réacteur une anode (A) sur laquelle un biofilm contenant essentiellement des bactéries autotrophes est formé, et une cathode (C), puis on établit des conditions d'anaérobie totale dans le réacteur; on introduit dans le réacteur un volume d'effluent à traiter; on applique et on maintient une différence de potentiel entre l'anode et la cathode pendant la durée du traitement d'élimination de l'azote ammoniacal., Process for treating effluents loaded with ammoniacal nitrogen in a single-chamber reactor (R), to remove the ammoniacal nitrogen therefrom, according to which: provided in the reactor is an anode (A) on which a biofilm essentially containing autotrophic bacteria is formed, and a cathode (C), then completely anaerobic conditions are established in the reactor; a volume of effluent to be treated is introduced into the reactor; a potential difference is applied and maintained between the anode and the cathode throughout the duration of the treatment for eliminating the ammoniacal nitrogen.

This study investigated the effect, on reactor performance and biomass retention inside the bed, of the material used to make the supports of anaerobic fixed-bed reactors. Three inert supports of similar shape but made of three different materials polyvinyl chloride, polypropylene, high-density polyethylene were manufactured and used. All three supports had the same specific surface area but different relative densities. Three identical 10 L lab-scale upflow anaerobic fixed-bed reactors were filled (80% of the working volume) each respectively with polyvinyl chloride, polypropylene and polyethylene support, and fed with vinasse (44 g total COD/L) for 140 days at 35 °C. The organic loading rates were increased from 0.5 g/L.d to the maximum acceptable by each reactor. Fairly similar maximum organic loading rates were reached for each type of support, with values above 20 g of COD/L.d and more than 80 % soluble chemical oxygen demand removal efficiency. A very large amount of biomass was entrapped and attached in all the supports and represented more than 95% of the total biomass inside the reactors. In terms of performance and biomass accumulation, this study demonstrated quite similar behavior for anaerobic fixed-bed reactors with supports made of different materials, which suggests that the nature of the material used to make the supports has no major influence. The chemical nature of the support material clearly has negligible effect and thus the size, shape, and porosity of the support must be more influential.

Transferts couplés au sein des réacteurs biologiques: Quelques exemples d'approches physiques au service de la compréhension et du contrôle des bioprocédés. Atelier de Formation sur la Fermentation ISBS/ENIS

Procédé de traitement d'effluents chargés en azote ammoniacal dans un réacteur à chambre unique (R), pour en éliminer l'azote ammoniacal, selon lequel : on prévoit dans le réacteur une anode (A) sur laquelle un biofilm contenant essentiellement des bactéries autotrophes est formé, et une cathode (C), puis on établit des conditions d'anaérobie totale dans le réacteur; on introduit dans le réacteur un volume d'effluent à traiter; on applique et on maintient une différence de potentiel entre l'anode et la cathode pendant la durée du traitement d'élimination de l'azote ammoniacal.

The present work is focused on developing an original micro to mesoscale approach to investigate various phenomena and then to intensify the performance of a reactor. At mesoscale, the emphasis is given to the interactions between granular sludge particles as well as the biogas production efficiency in a 2D reactor under various hydrodynamic conditions at different concentrations of substrate. Then, within the microdevices, a single sludge particle of various sizes was used under different operating conditions such as superficial liquid velocity and concentration of substrate. The effect of different hydrodynamic conditions and concentration of substrate was studied; Ce travail vise à développer une approche originale à micro et à méso-échelle pour étudier divers phénomènes et intensifier les performances du réacteur. A méso-échelle, l'accent est mis sur l'efficacité de la production de biogaz dans un réacteur anaérobie 2D sous différentes conditions hydrodynamiques ainsi qu'à différentes concentrations de substrat. Puis, dans un dispositif microfluidique transparent, une seule granule de différentes tailles a été utilisée sous différentes conditions d'exploitation. Les effets des différentes conditions hydrodynamiques et des concentrations de substrat associés à la taille et la densité des granules de boues sur la production de biogaz ont été étudiés

The present work is focused on developing an original micro to mesoscale approach to investigate various phenomena and then to intensify the performance of a reactor. At mesoscale, the emphasis is given to the interactions between granular sludge particles as well as the biogas production efficiency in a 2D reactor under various hydrodynamic conditions at different concentrations of substrate. Then, within the microdevices, a single sludge particle of various sizes was used under different operating conditions such as superficial liquid velocity and concentration of substrate. The effect of different hydrodynamic conditions and concentration of substrate was studied, Ce travail vise à développer une approche originale à micro et à méso-échelle pour étudier divers phénomènes et intensifier les performances du réacteur. A méso-échelle, l'accent est mis sur l'efficacité de la production de biogaz dans un réacteur anaérobie 2D sous différentes conditions hydrodynamiques ainsi qu'à différentes concentrations de substrat. Puis, dans un dispositif microfluidique transparent, une seule granule de différentes tailles a été utilisée sous différentes conditions d'exploitation. Les effets des différentes conditions hydrodynamiques et des concentrations de substrat associés à la taille et la densité des granules de boues sur la production de biogaz ont été étudiés

L'invention concerne un procédé d'épuration d'effluent en réacteur (1) anaérobie dans lequel les microorganismes sont retenus par des supports, les supports formant un lit fixe dans une partie (4, 5) du réacteur, caractérisé en ce qu'il comporte l'étape consistant à procéder à un décolmatage du réacteur une fois qu'il est au moins partiellement colmaté, par mise en suspension temporaire des supports. L'invention concerne également une utilisation d'un réacteur (1) biologique comportant des microorganismes retenus par des supports et des moyens de fluidisation (6, 7, 9) aptes à mettre en suspension les supports, caractérisée en ce que le réacteur est utilisé pour l'épuration d'un effluent par traitement anaérobie, les moyens de fluidisation étant utilisés temporairement de manière à décolmater le réacteur, les supports étant immobiles et formant un lit fixe dans le réacteur lorsque les moyens de fluidisation ne sont pas utilisés.