Intensification of continuous bio-hydrogen production from C5/C6 sugars

Chemoheterotrophic (”dark”) fermentation at extreme thermophilic (70oC) conditions presents a promising route of biological hydrogen production. To achieve satisfactory hydrogen production rate, immobilized-cell systems such as EGSB could be an alternative to carrier-free (suspended-cell) systems. However, a major drawback in the immobilized system is the long period that takes to develop the active hydrogen producing granules. Therefore, ready constructed anaerobic granules containing active and fast growing hydrogen producers is a prerequisite for fast and efficient hydrogen production. This work aimed to develop an efficient EGSB reactor system containing engineered granules for high rate extreme thermophilic biohydrogen production from carbohydrate feedstocks. Heat treated methanogenic granules (HTG) and engineered heat treated methanogenic granules (EHTG) were individually inoculated in each reactor operated at 70±1ºC, pH 5.5 and fed with a mixture of glucose and arabinose (1:1) at a final concentration of 5 g COD.L-1. HTG were obtained by treatment of the granules at 121oC for 45 min heat treatment, to completely inhibit methanogenic activity. EHTG were obtained by surface attachment immobilized-cell technique with an H2-producing mixed culture enriched from digested household solid waste, using HTG as carriers. Scaning electron microscope (SEM) analysis showed microorganisms attached to surface of granules in both reactor systems. A greatly improved hydrogen production rate amounting up to 2500 mL H2 L-1d-1 in steady state was demonstrated by EHTG in EGSB system. In comparison, almost no hydrogen production was recorded by HTG, only occasional hydrogen production peaks in the range 800-1500 mL H2 L-1d-1 without real steady state were observed. EGSB reactor system with EHTG as microbial carriers, appears to be the most preferred a promising process for highly efficient dark fermentative hydrogen production from sugar containing feedstocks under extreme thermophilic conditions

Comparação dos efeitos secundários agudos da Radioterapia por intensidade modulada com a Radioterapia tridimensional conformada no carcinoma de próstata

Introdução: Este trabalho tem como principal objectivo comparar os efeitos secundários agudos da Radioterapia por Intensidade Modulada (IMRT) e a Radioterapia Tridimensional Conformada (3 D-CRT) no carcinoma de Próstata; Materiais e métodos: Foram observados os processos clínicos de 30 doentes e analisados os efeitos colaterais da RT ocorridos no decurso do tratamento. Resultados: A percentagem de toxicidade aguda dermatológica foi superior no grupo tratado com 3D-CRT. Nenhum doente apresentou toxicidade aguda grave. Conclusões: O tamanho reduzido da amostra e a ausência de valores estatisticamente significativos, não permite concluir a influência da técnica de RT no desenvolvimento de efeitos secundários agudos.Introduction: This study has as main objective to compare the acute side effects for Intensity Modulated Radiotherapy (IMRT) and Tridimensional Conformal Radiotherapy (3D-CRT) in prostate cancer; Materials and methods: We observed the clinical files of 30 patients and analyzed the side effects of RT occurred in the course of treatment. Results: The percentage of acute dermatological toxicity was higher in the group treated with 3D-CRT. No patient showed severe acute toxicity. Conclusions: The small sample size and lack of statistically significant values, does not suggest the influence of RT on the development of acute side effects

Induction of hydrogen production affects micro and macro structure of granular sludge

Mixed-culture dark fermentation is an environmentally friendly bio-hydrogen production process. In this work we study the potential for directing microbial anaerobic mixed communities towards improved hydrogen production. Strategies applied for promoting the selection of hydrogen-producing bacteria in anaerobic granules consisted of Heat treatment and chemical treatment with 2-bromo-ethane sulfonate (BES) and with BES+Chloroform. Three EGSB reactors, RHeat, RBES and RBES+Chlo, where inoculated with each treated granules and fed with synthetic sugar-based wastewater. Hydrogen production was monitored. Morphological integrity and microbial diversity of the granules were studied using image analysis technique and 16S rRNA gene based techniques, respectively. Hydrogen production in RHeat was below 300 mLH2L-1d-1, with the exception of a single transient production of 1000 mLH2L-1d-1, after decrease the HRT. In RBES+Chlo hydrogen production rate never exceeded 300 mLH2L-1d-1. In this sludge, a physical deterioration of the granules was observed along with a decrease of their density and microbial diversity. In RBES, a transient period of unstable H2 production was observed but an additional pulse of BES triggered hydrogen production rate to an average value of 700 ± 200 mLH2L-1d-1, which was kept for 30 days. This strategy did not affect significantly granules structure. Dominant bacterial ribotypes found in RBES were closely related to Clostridium species and to uncultured microorganisms belonging to Clostridiaceae and Ruminococcaceae. This work demonstrates that different methods applied for directing granular sludge for hydrogen production can cause changes in the macro- and microstructure of granular sludge, which can be incompatible with the long-term operation of high-rate reactors

Directing mixed cultures for optimized hydrogen dark fermentation

Hydrogen is recognized as an ideal future energy carrier for the replacement of fossil fuels. Among hydrogen production processes, mixed culture dark fermentation has been viewed as the most promising and environmental friendly. If waste/wastewaters can be used as raw materials for the production of hydrogen in such process, its overall sustainability can be even augmented. For this purpose, it is of utmost importance to select, e.g. by means of environmental pressure, the seed sludge used to start-up. The aim is to obtain a reliable method for the development of microbial anaerobic mixed communities specialized in hydrogen production, in which methanogenic activity has to be prevented. In this work, different strategies (heat, BES+Chloroform and BES) were used for promoting the selection of hydrogen-producing microorganisms in anaerobic granular sludge (AGS). Three EGSB reactors (RHeat, RBES/Chlo and RBES) were inoculated with the AGS resulting from the 3 different treatments and fed with synthetic sugar-based wastewater. Morphological properties of the sludges during reactors’ operation were studied using image analysis techniques. Microbial community dynamics was followed by using 16S rRNA gene based techniques (DGGE, cloning and sequencing). Hydrogen production in RHeat was unstable and rather low. No methane was produced and acetate concentrations were high (up to 1878mgl-1), suggesting hydrogen consumption by homoacetogenic bacteria. Homoacetogenic activity in RBES/Chlo was lower, but an increase on propionate formation decreased the overall hydrogen yield. This AGS showed higher free filaments length per VSS, lower granules density and an evident granule fragmentation. This was coincident with a decrease on microbial diversity. In RBES there was an initial period in which homoacetogenenic activity could be detected. However, an additional pulse of BES triggered hydrogen production rate to an average value of 700mlH2 l-1d-1. In terms of morphological integrity of AGS this strategy revealed higher potential. Bacterial communities present during RBES operation were predominantly composed of bacteria branching the Clostridiaceae family

Enhancement of methane production from long chain fatty acid based effluents

Two anaerobic sludges previously loaded with oleate and palmitate accumulated 4570 ± 257 and 5200 ± 9 mgCOD-LCFA gVSS−1, respectively. These sludges were incubated in batch assays and methane production was recorded after addition of 100–900 mg L−1 of oleate and palmitate, respectively. The batch assays were conducted before and after allowing the depletion of the biomass-associated LCFA. The presence of biomass-associated LCFA decreased the capacity of both sludges to convert the added LCFA to methane. After the degradation of biomass-associated LCFA, the lag phases observed before the onset of methane production were significantly reduced, evidencing an increase in the tolerance of the acetotrophic methanogens to the presence of LCFA. In another experiment, three recurrent pulses were performed with a real dairy wastewater containing 3.6 gCOD L−1, from which 53% was fat. Methane yields of 0.45 ± 0.01, 0.88 ± 0.02 and 1.29 ± 0.08 gCOD- CH4 gCODfed-1 were achieved in the first, second and third pulses, respectively, evidencing an increasing capacity of the sludge to convert substrate accumulated in previous additions.Fundo Social Europeu (FSE)Fundação para a Ciência e a Tecnologia (FC

Efeito da aclimatização do inóculo e da recirculação da biomassa na degradação de ácido oléico em filtro anaeróbio

Este trabalho teve por objectivo o estudo da degradação do ácido oleico (um dos mais tóxicos e mais abundante entre os Ácidos Gordos de Cadeia Longa - AGCL presentes em efluentes) em filtro anaeróbio, avaliando o efeito da aclimatização da biomassa utilizada como inóculo e também da recirculação da biomassa. Operaram-se três filtros anaeróbios (R1, R2 e R3) em paralelo. Em R1 inoculou-se biomassa não aclimatizada e não se recirculou a biomassa que saía do reactor. Em R2 inoculou-se biomassa não aclimatizada e recirculou-se a biomassa e em R3, também com recirculação, inoculou-se biomassa aclimatizada com lípidos e oleato. O desempenho dos digestores foi avaliado durante 233 dias em termos de CQO (Carência Química de Oxigénio) solúvel removida, AGV (Ácidos Gordos Voláteis) e SSV (Sólidos Suspensos Voláteis) à saída, e produção de metano. Obtiveram-se eficiências de remoção entre 70 a 77%, para uma carga aplicada de oleato de 12.5 kgCQO/m³.dia, mesmo com concentrações molares oleato/(Ca2++Mg2+) de 6.79. Os rendimentos em metano diminuíram com o aumento da carga aplicada em oleato, embora as remoções de CQO solúvel se tenham mantido superiores a 70%. Este facto sugere que parte do oleato possa ter sido retida por adsorção na biomassa. Verificou-se que a recirculação da biomassa foi vantajosa no desempenho deste sistema, promovendo a minimização do efeito de lavagem (“washout”) e a diluição da carga tóxica aplicada, conduzindo a uma menor inibição da população acetogénica e metanogénica. Além disso, o efeito inibitório do oleato de sódio sobre as populações acetogénicas e metanogénicas foi menos sentido num filtro anaeróbio inoculado com biomassa previamente aclimatizada. Conclui-se que, do ponto de vista do tratamento de efluentes com elevada carga em oleato, o efeito combinado da recirculação de biomassa e utilização de um inóculo aclimatizado é benéfico, melhorando a eficiência do desempenho do filtro anaeróbio