RESUMO
This study investigated the microbial community developed in a UASB reactor for hydrogen production and correlated it to reactor performance. The reactor was inoculated with kitchen waste compost and fed with raw cheese whey at two organic loading rates, 20 gCOD/Ld and 30 gCOD/Ld. Hydrogen production was very variable, using an OLR of 30 gCOD/Ld averaged 1.0 LH(2)/Ld with no methane produced under these conditions. The hydrogen yield was also very variable and far from the theoretical. This low yield could be explained by selection of a mixed fermentative population with presence of hydrogen producing organisms (Clostridium, Ruminococcus and Enterobacter) and other non-hydrogen producing fermenters (Lactobacillus, Dialister and Prevotella). The molecular analysis of the raw cheese whey used for feeding revealed the presence of three predominant organisms that are affiliated with the genera Buttiauxella (a low-yield hydrogen producer) and Streptococcus (a lactic acid-producing fermenter). Although these organisms did not persist in the reactor, the continuous addition of these fermenters could decrease the reactor's hydrogen yield.
Assuntos
Bactérias/classificação , Bactérias/metabolismo , Reatores Biológicos , Hidrogênio/metabolismo , Proteínas do Leite/metabolismo , Anaerobiose , Biomassa , Fermentação , Indústria Alimentícia , Resíduos Industriais , Proteínas do Leite/química , Eliminação de Resíduos Líquidos , Proteínas do Soro do LeiteRESUMO
The hydrodynamic behaviour of UASB (Up Flow Anaerobic Sludge Blanket) reactors based on residence time distribution curves allows the implementation of global models, including the kinetic aspects of biological reactions. The most relevant hydrodynamic models proposed in the literature are discussed and compared with the extended tanks in series (ETIS) model. Although derived from the tanks in series model, the ETIS model's parameter is not an integer. The ETIS model can be easily solved in the Laplace domain and applied to a two-stage anaerobic digestion linear model. Experimental data from a 250 m3 UASB reactor treating malting wastewater are used to calibrate and validate the proposed model.
Assuntos
Bactérias Anaeróbias/fisiologia , Reatores Biológicos/microbiologia , Modelos Biológicos , Reologia/instrumentação , Esgotos/microbiologia , Simulação por Computador , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , CinéticaRESUMO
A full scale UASB reactor treating the effluent of a malting plant was operated during nearly two years. During 37 weeks of operation the reactor worked with a COD removal efficiency of 80% and a biogas production of nearly 300 m(3)/d with a methane content of 77%. After the start up and during these months of operation the volumetric organic load was 4 kgCOD/m(3).d and the specific organic load was between 0.2-0.4 kgCOD/kgVSS.d. The sludge SMA in this period was around 0.25 kgCOD/kg VSS.d. On week 37 as a result of a problem at the industrial process the pH in the reactor dropped to a value of 4.8. After pH recovering, the reactor worked with fluctuating COD values in the exit and showed a downward trend in the COD removal efficiency. On week 81 the presence of filaments in the granules was detected. High proportion of Chloroflexi filaments were detected by FISH in the sludge. Changes in the microbial population caused by the low pH probably destabilize the reactor performance. The presence of filamentous granules in the sludge and its further growing could be encouraged by the pH drop and the low specific organic load applied to the reactor. The low specific organic load was a consequence of the high VSS content in the UASB reactor, due to the lack of purges. The length of the filaments attached to the granules grew throughout time. In order to eliminate the sludge with poor settlement properties a recycle was applied to the reactor. As a consequence, low amount of granular sludge stayed in the reactor. At the end, COD concentration in the influent reached higher values than in normal operation; at the same time a complete sludge wash out occurred. On the other hand, using the same sludge (after the recycle implementation) in a bench scale reactor the good properties of the sludge were completely recovered.
Assuntos
Reatores Biológicos/microbiologia , Esgotos , Eliminação de Resíduos Líquidos/métodos , Chloroflexi/crescimento & desenvolvimento , Concentração de Íons de Hidrogênio , Metano/metabolismoRESUMO
At the present time, organic solid wastes from industries and agricultural activities are considered to be promising substrates for biogas production via anaerobic digestion. Moreover solids stabilisation is required before reutilization or disposal. Slaughterhouses are among the most important industries in Uruguay and produce 150,000 tons of ruminal content (RC) and 30,000 tons of blood per year. In order to determine the influence of the solids and blood contents, the ammonia inhibition and the inoculum adaptation co-digestion batch tests were performed. A set of experiences with TS concentration of 2.5%, 5% and 7.5% and different ratios of RC/blood were carried out using an inoculum from an UASB reactor. In all experiences fast blood hydrolisation was observed. A higher methane production was detected in the experiences with higher TS content. However, the fraction of solids degradation was lower in these experiences. A plateau in the biogas production was found. The free ammonia level, which was above the reported inhibitory levels, could explain this behaviour. After the inhibition period the biogas production restarted probably due to the biomass acclimatisation to the ammonia. In order to determine the inoculum adaptation a new experiment was performed. The inoculum used was the sludge coming from the first set of experiences. Based upon batch tests a 3.5 m3 pilot reactor was designed and started up. Ammonia inhibition was avoided by the start-up strategy and in two weeks the biogas production was 3.5 m3/d. The VS stabilisation with a solid retention time of 20 days was of 43%. The pilot reactor working at steady state had a TS concentration of 3-4% with a ratio of RC/blood of 10:1 at the entrance.
Assuntos
Matadouros , Sangue , Compostos de Amônio Quaternário/síntese química , Eliminação de Resíduos/métodos , Rúmen/química , Animais , UruguaiRESUMO
Aerobic and methanogenic consortia were evaluated as inocula for laboratory scale denitrifying reactors, fed with a synthetic wastewater with acetate as the main electron donor. The denitrifying microflora of inocula and reactors was evaluated by specific denitrifying activity, enumeration and isolation of denitrifiers, which were screened by amplified ribosomal DNA restriction analysis. Reactor performance was monitored by COD and nitrate removal efficiencies and granule size. The aerobic sludge failed to form granules, probably due to the development of a filamentous, nitrate-reducing organism which was characterised by 16SrDNA sequencing as Bacillus cereus. The methanogenic sludge showed denitrifying activity and adapted very rapidly to denitrifying conditions in the two reactors seeded with granules of different sizes. Denitrifiers grew around the granules, increasing the specific denitrifying activity of the sludge over 10-fold. Exopolymer-forming organisms, belonging to the same species, were isolated from both reactors. Granule size increased during operation, but flotation of the aggregates, related to gas retention was observed.
Assuntos
Bacillus cereus/fisiologia , Bactérias Aeróbias/fisiologia , Reatores Biológicos , Euryarchaeota/fisiologia , Eliminação de Resíduos Líquidos/métodos , Acetatos/metabolismo , DNA Bacteriano/análise , Nitratos/metabolismo , Tamanho da Partícula , Polímeros , RNA Ribossômico 16S/análiseRESUMO
A 3 m3 pilot UASB reactor was operated with malting wastewater. In order to find the aggregation characteristics, the sludge concentration profile was determined throughout time. Reactor behaviour concerning the physical properties of the sludge can be evaluated using this procedure. Moreover, organic load per VSS can be calculated from this profile. The organic load based per VSS is more accurate as a design parameter than the volumetric load. Under the study conditions imposed the COD removal efficiencies achieved were about 85%. Organic loads of 0.6-0.7 kg COD/(kgVSS.d) were reached. After operating at 30 degrees C, temperatures of 28 degrees C and 15 degrees C were tested, showing no decrease in COD removal efficiency. At week 15 the presence of granules was verified, and after that, sludge concentrations of 30-35 kg VSS/m3 were measured at the bottom of the reactor. The SVI of the granular sludge decreased to values below 20 mL/gVSS. The settlement velocity was 10 m/h, which is much greater than the recommended values for the settlement zone; therefore, no problems are to be expected in the settler regarding the sludge sedimentation. The biomass yield coefficient obtained was 0.10 gVSS/gCOD in agreement with literature values for brewering effluent.
Assuntos
Bebidas Alcoólicas , Resíduos Industriais , Eliminação de Resíduos Líquidos/métodos , Bactérias Anaeróbias/fisiologia , Biomassa , Compostos Orgânicos/análise , Oxigênio/metabolismo , TemperaturaRESUMO
En este trabajo se presentan los resultados obtenidos en los ensayos, que tienen como antecedentes estudios previos a escala de laboratorio, los que permitieron realizar el diseño del reactor industrial de 300 m3, en actual construcción
Assuntos
Engenharia Sanitária , Águas Residuárias , Purificação da Água , Reatores Anaeróbios de Fluxo Ascendente , CongressoRESUMO
En este trabajo se realizaron experiencias en un reactor a escala piloto, utilizando litio como trazador, para determinar el modelo de flujo de un reactor anaerobio del tipo manto de lodos (UASB). Se comparan los resultados de esta experiencia con otra realizada a escala de laboratorio y se discuten las diferencias de comportamiento a ambas escalas