Renato C Leitao | EMBRAPA - Empresa Brasileira de Pesquisa Agropecuária (original) (raw)

Papers by Renato C Leitao

Revista DAE, 2014

Resumo O Brasil gera uma grande quantidade de resíduos lignocelulósicos provenientes das cadeias ... more Resumo O Brasil gera uma grande quantidade de resíduos lignocelulósicos provenientes das cadeias produtivas dos biocombustíveis, que podem ser aproveitados para produção de combustíveis de segunda geração como, por exemplo, o metano. No entanto, o aproveitamento desta biomassa como fonte de energia pela via fermentativa normalmente requer pré-tratamento do material lignocelulósico, visando solubilização de açúcares ou remoção de lignina, que será definido em função da característica do substrato utilizado ou da posterior utilização do hidrolisado. A escolha deve ainda considerar aspectos operacionais, custos e geração de substâncias tóxicas.

Engenharia Sanitaria e Ambiental, 2011

Processos convencionais de tratamento de efluentes utilizam microrganismos vivos, o que sugere li... more Processos convencionais de tratamento de efluentes utilizam microrganismos vivos, o que sugere limitações relativas À toxicidade de metais para os microrganismos. O experimento consistiu em adicionar soluções monoelementares de Cr (VI) e Zn(II) em diferentes concentrações (0, 20, 50, 100, 200, 300, 400, 500 mg.L-1) ao meio de crescimento e observar a influência dos metais no crescimento micelial e germinativo do fungo Aspergillus Níger por verificação visual da expansão radial do micélio e da germinação de esporos, seguida de registro fotográfico. Os resultados mostraram que o metabolismo do fungo foi completamente inibido em concentrações acima de 500 mg Zn (II).L-1 e 150 mg Cr (VI).L-1. O ED50 (concentração de ingrediente ativo capaz de inibir 50% do crescimento micelial do fungo) para os dois íons metálicos, nas condições estudadas, está na faixa entre 100 e 150 mg.L-1. Palavras-chave: metais pesados; inibição; crescimento micelial; Aspergillus niger; ED50.

Engenharia Sanitaria e Ambiental, 2006

Nesta pesquisa, estudou-se a influência do tempo de detenção hidráulica (TDH) em um sistema const... more Nesta pesquisa, estudou-se a influência do tempo de detenção hidráulica (TDH) em um sistema constituído de um reator anaeróbio tipo UASB seguido de um reator biológico com fungos (RBF) para tratar efluente de uma indústria de beneficiamento de castanha de caju. O presente trabalho foi dividido em uma fase de fluxo descontínuo (batelada) e uma fase de fluxo contínuo (UASB - RBF), que constituiu-se de sete etapas ( 8h e 2h, 8h e 1h, 4h e 8h, 4h e 6h, 4h e 4h, 4h e 2h e 4h e 1h), onde foi avaliada a influência do TDH na remoção de: DQO (Demanda Química de Oxigênio), amônia, nitrato e ortofosfato. Uma combinação que apresentou melhores resultados, foi a etapa de 4h (TDH do reator UASB) e 2h (TDH do RBF), apresentando remoções de: 93,8% de DQO, 86,7% de nitrato, 38,3% de amônia e 16% de ortofosfato.

Water Science & Technology, 2011

This work aims to evaluate the hydrodynamic properties of the sludge bed of Upflow Anaerobic Slud... more This work aims to evaluate the hydrodynamic properties of the sludge bed of Upflow Anaerobic Sludge Blanket (UASB) reactors based on its settleability and expansion characteristics. The methodologies used for the evaluation of the settleability of aerobic activated sludge, and for the expansibility of a sludge bed of Expanded Granular Sludge Bed reactors and Fluidised Bed Reactors were adapted and applied to the particular characteristics of the sludge of UASB reactors. An easy-to-build experimental set-up was developed to assess the parameters necessary for the equations of settleability and of expansibility. The results obtained from the sludges of seven differently operated reactors show that, for the treatment of low strength wastewater, settleability increased and expansibility decreased at decreased hydraulic retention time, from 6 to 1 h, and/or increased influent concentrations, from 136 to approximately 800 mg chemical oxygen demand/L. The results also show that it is usele...

Journal of Biotechnology, 2008

The market for coconut water causes environmental problems as it is one of the major agroindustri... more The market for coconut water causes environmental problems as it is one of the major agroindustrial solid wastes in some developing countries. With the aim of reusing the coconut husk, Embrapa developed a system for processing this raw material. During the dewatering stage Coconut Husk Liquor (CHL) is generated with chemical oxygen demand (COD) varying from 60 to 70 g/L due to high concentrations of sugars and tannins. The present study evaluated the feasibility of anaerobic treatment of CHL through Anaerobic Toxicity Assay and the operation of a lab-scale Upflow Anaerobic Sludge Blanket (UASB) reactor. Results showed that CHL can be treated through a UASB reactor operating with an OLR that reaches up to 10 kg/m 3 •d and that is maintained stable during the whole operation. With this operational condition, the removal efficiency was higher than 80% for COD and approximately 78% for total tannins, and biogas production was 20 m 3 of biogas or 130 KWh per m 3 of CHL. Seventy-five percent of the biogas composition was methane and toxicity tests demonstrated that CHL was not toxic to the methanogenic consortia. Conversely, increasing the concentration of CHL leads to increased methanogenic activity.

… Sanitaria e Ambiental, 2006

In this research, it was studied the effect of hydraulic retention time (HRT) in a system compris... more In this research, it was studied the effect of hydraulic retention time (HRT) in a system comprised of an Upflow Anaerobic Sludge Blanket (UASB) reactor and a Biological Reactor with Fungi (BRF) for treatment of the efluent of the industry of cashew nut improvement. ...

Biotechnology Letters, 2014

The fermentative production of H2 from residual glycerol is an attractive alternative for clean e... more The fermentative production of H2 from residual glycerol is an attractive alternative for clean energy production from a waste product. Selection of operational variables for microbial populations with an adequate diversity in order to improve H2 yields is an issue faced during optimization of biological production of H2. Operational and environmental factors affect both microbial diversity and the activity of specific enzymes. Therefore, these variables must be controlled to obtain the best H2 yields. This review covers the main variables involved in the fermentative production of H2 from crude glycerol and the biochemistry of the anaerobic digestion of glycerol, with a focus on the microbial diversity involved in this process.

… Sanitária e Ambiental, 2004

... EMÍLIA MARIA ALVES SANTOS Professora da Universidade Federal do Ceará. ... A alternância de p... more ... EMÍLIA MARIA ALVES SANTOS Professora da Universidade Federal do Ceará. ... A alternância de produção e remo-ção de nitrato observada no RBF deste experimento, também foi verificada por Sá (1997) tratando água residuária de laticínio com fungos, com TDH de 31h, 21h ...

Acta Scientiarum. Biological Sciences, 2013

This study evaluated the trophic conditions of the reservoir located in the urban perimeter of th... more This study evaluated the trophic conditions of the reservoir located in the urban perimeter of the town General Sampaio, semiarid region of the Ceará State, Brazil and its relationship with seasonal variation in rainfall between 2010 and 2011. It was obtained data for Secchi disk transparency, total phosphorus, and chlorophyll a to calculate the Trophic State Index (TSI), as well as rainfall data. The Trophic State Index (TSI) proposed by Carlson (1977) and modified by Toledo Junior (1990) was used to test the influence of the seasonal variation in rainfall on hydrological variables and on trophic conditions of the reservoir in 2010 and 2011. There was seasonal variability in variables analyzed between climatic periods (rainy and dry) and trophic conditions determined through the trophic index indicated conditions ranging from oligotrophic to eutrophic during the two years analyzed in this reservoir. Under these circumstances, one may conclude that the trophic status is related to seasonal fluctuations in the hydrology of the system controlled by rainfall, which is a common feature of semiarid regions.

Bioresource Technology, 2006

With the aim of improving knowledge about the stability and reliability of anaerobic wastewater t... more With the aim of improving knowledge about the stability and reliability of anaerobic wastewater treatment systems, several researchers have studied the effects of operational or environmental variations on the performance of such reactors. In general, anaerobic reactors are affected by changes in external factors, but the severity of the effect is dependent upon the type, magnitude, duration and frequency of the imposed changes. The typical responses include a decrease in performance, accumulation of volatile fatty acids, drop in pH and alkalinity, change in biogas production and composition, and sludge washout. This review summarises the causes, types and effects of operational and environmental variation on anaerobic wastewater treatment systems. However, there still remain some unclear technical and scientific aspects that are necessary for the improvement of the stability and reliability of anaerobic processes.

This PhD thesis presents results and discussions to elucidate the matters of performance and robu... more This PhD thesis presents results and discussions to elucidate the matters of performance and robustness of the Upflow Anaerobic Sludge Blanket (UASB) reactors for the treatment of municipal wastewater in tropical countries. The research focuses on the main operational parameters (hydraulic retention time -HRT, influent COD concentration - COD Inf , organic loading rate - OLR, and sludge retention time - SRT) that affect the UASB loading potentials and its performance in "steady state" conditions, and on the response of the system when submitted to transient conditions. The experimental investigation was performed using 11 pilot-scale UASB reactors (120 L) which were organised into three sets: Set 1, five reactors were operated with the same hydraulic retention time (HRT = 6 h) and different COD Inf , ranging from 92 to 816 mg/L. Set 2, four reactors were operated with approximately the same COD Inf (~800 mg/L), but with different HRTs, ranging from 1 to 6 hours. Set 3, the...

Base de dados : REPIDISCA. Pesquisa : 15293 [Identificador único]. Referências encontradas : 1 [r... more Base de dados : REPIDISCA. Pesquisa : 15293 [Identificador único]. Referências encontradas : 1 [refinar]. Mostrando: 1 .. 1 no formato [Detalhado]. página 1 de 1, 1 / 1, REPIDISCA, seleciona. para imprimir. Fotocópia. Texto completo. Id: 15293. ...

Environmental technology, Jan 26, 2016

The aim of this research was to estimate the production of hydrogen, organic acids and alcohols b... more The aim of this research was to estimate the production of hydrogen, organic acids and alcohols by the strain of Clostridium acetobutylicum ATCC 824 using residual glycerol as a carbon source. The experiments were carried out in pure and mixed cultures in batch experiments. Three different sources of inocula for mixed culture were used. Ruminal liquid from goats and sludge collected from two upflow anaerobic sludge blanket reactors treating municipal wastewater and brewery effluent were tested for hydrogen, organic acids and alcohols production with or without C. acetobutylicum ATCC 824. The main detected end-products from the glycerol fermentation were hydrogen, organic acids (acetic, propionic, butyric and caproic) and alcohol (ethanol and 1,3-propanediol - 1,3PD). High hydrogen (0.44 mol H2/mol glycerol consumed) and 1,3PD (0.32 mol 1,3PD/mol glycerol consumed) yields were obtained when the strain C. acetobutylicum ATCC 824 was bioaugmented into the sludge from municipal wastewat...