Paula Fernanda TeixeiraEngenheira Civil. Doutora pela EPUSP ResumoA oxidação biológica e aeróbia do metano em materiais de cobertura de aterros de resíduos sólidos urbanos é uma das alternativas para se minimizarem as emissões dos gases de efeito estufa. Este artigo tem como objetivo avaliar a oxidação biológica do metano em material de cobertura de três aterros brasileiros (dois municipais e uma célula experimental). O trabalho consistiu na coleta de amostras dos solos, as quais foram caracterizadas através de ensaios geotécnicos e microbiológicos. Em laboratório, avaliou-se o consumo de metano de uma amostra de cada aterro. Os resultados revelaram a presença de bactérias metanotróficas e consumo de metano em laboratório, o que sugere que exista uma relação inversa entre o grau de saturação no momento da coleta e o número de bactérias metanotróficas.Palavras-chave: aterro sanitário; metano; aquecimento global; efeito estufa; bactérias metanotróficas; oxidação aeróbica do metano; resíduos sólidos; cobertura. AbstractThe biological and aerobic oxidation of methane within the soil cover of municipal solid waste landfills is one an alternative to minimize emissions of greenhouse effect gases. This study aims at assess the biological oxidation of methane within the final cover of three landfills in Brazil (two municipal ones and one experimental cell). The soil samples obtained from the landfill cover were characterized by geotechnical and microbiological tests. In the laboratory the consumption of methane from each sample were evaluated. The results revealed the presence of methanotrophic bacteria and consumption of methane in the laboratory was observed, which also suggest that there is an inverse relation between the degree of saturation at the time of sampling and the number of methanotrophic bacteria.Keywords: sanitary landfill; methane; global warming; greenhouse effect; methanotrophic bacteria; methane oxidation; solid waste; landfill cover. (WHalen;reeBUrgH;sandBeCk, 1990;Bender;COnrad, 1995;BOeCkX;van CleemPUt; vIllaralvO, 1996;BarlaZ et al, 2004;HIlger;HUmer, 2003;nIkIema;BrZeZInskI;HeItZ, 2007;eInOla;karHU;rIntala, 2008). a oxidação do metano também foi constatada em ambientes anaeróbios (ZeHnder;BrOCk, 1980). a oxidação biológica do gás metano acontece através da ação de bactérias metanotróficas que são capazes de utilizar o metano como fonte de carbono e energia, principalmente quando próximo à superfície, onde existe um aporte maior de oxigênio (PELMONT, 1993;HANSON; HANSON, 1996, mUrrel;BOUrne, 1998, McDONALD et al, 2008. esse fenômeno biológico se instala espontanemante e é dependente do fluxo de metano pela cobertura e do oxigê-nio presente (Bender;COnrad, 1995;BOgner, 1995;kIgHtleY;nedWell, 1995;BÖrJessOn;svenssOn, 1997;BOeCkX;van CleemPUt; vIllaralvO, 1996;BarlaZ et al, 2004;nIkIema;BrZeZInskI;HeItZ, 2007;eInOla;karHU;rIntala, 2008).O gás metano que passa através da cobertura dos aterros de resíduos sólidos urbanos (rsU) é consumido pelas bactérias metanotróficas que o convertem em água, dióxid...

The performance of biofiltration to mitigate CH4 emissions from cow barns was investigated in the laboratory using two flow-through columns constructed with an acclimatized packed bed media composed of inexpensive materials and readily available in an agricultural context. The biofilters were fed with artificial exhaust gas at a constant rate of 0.036 m 3 h-1 and low inlet CH4 concentration (0.22 g m-3 = 300 ppm). The empty-bed residence time (EBRT) was equal to 0.21 h. Additionally, in order to simulate temperature changes under natural conditions and determine the influence of such cycles on CH4 removal efficiency, the upper part of the biofilters were submitted to temperature oscillations over time. The maximum oxidation rate (1.68 μg CH4 gdw-1 h-1) was obtained with the commercial compost mixed with straw. Accordingly, it was considered as packing bed media for the biofilters. The CH4 removal efficiency was affected by the temperature prevailing within the biofilters, by the way in which the cooling-warming cycles were applied and by the acclimatization process. The shorter the cooling-warming cycles, the more oxidation rates varied. With longer cycles, CH4 removal rates stabilized and CH4 removal efficiencies attained nearly 100% in both biofilters, and remained at this level for more than 100 days, irrespective of the temperature at the top of the biofilter, which was-at times-adverse for microbiological activity. The first order rate constant for CH4 oxidation kinetics of the entire system was estimated at 15 h-1. If such rate could be transposed to real field conditions in Canada, home to nearly 945,000 dairy cows, biofiltration may be applied to efficiently abate between 2 x 10 6 and 3 x 10 6 t yr-1 of CO2 equivalent (depending on how estimates are performed) from bovine enteric fermentation alone.

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ResumoO principal objetivo deste trabalho foi a avaliação quantitativa da influência do etanol sobre a volatilização de BTEX (benzeno, tolueno, etilbenzeno e xilenos) em mistura de gasolina e etanol anidro 25% (v/v) em colunas experimentais, que simularam solos contaminados com gasolina pura e gasolina/etanol. Todos os BTEX apresentaram expressivo aumento das taxas de volatilização na coluna contendo a mistura gasolina/etanol. Porém, em termos percentuais, o maior e menor aumento nas taxas de volatilização foi observado para tolueno e benzeno, respectivamente. Em amostras de controle, com o percentual de etanol variando entre 0 e 25%, não foi observado aumento no grau de volatilização do etilbenzeno, enquanto que o grau de volatilização dos xilenos foi reduzido.Estes resultados sugerem que, além de forças de interação intermoleculares, efeitos de interação líquido/estrutura do solo podem estar exercendo importante papel na volatilização dos BTEX.Palavras-chave: etanol; BTEX; cromatografia; GC/FID; volatilização; contaminação de solo. AbstractThe main objective of this paper was the quantitative evaluation of the ethanol's influence about the volatilization of BTEX (benzene, toluene, ethylbenzene and xylenes) in a mixture of gasoline and anhydrous ethanol 25% (v/v) in experimental columns that simulated soil contamination with gasoline/ethanol. All the BTEX presented expressive increase of volatilization rates in the gasoline-ethanol column. However, in terms of percentage, the highest and lowest volatilization grades were observed for toluene and benzene, respectively. In batch tests (control samples), with mixtures of gasoline ethanol with 0 and 25% (v/v) in ethanol, no increase of the volatilization grade was observed for ethylbenzene and the volatilization grade for xylenes was reduced. Matrix effects seem to be, besides the intermolecular interaction forces, important contributions for the volatilization grade of BTEX in this kind of sample.

The main objective of present study was to assess the evaporation profile of monoaromatic compounds, namely, benzene, toluene, and xylenes (BTX) from gasoline-ethanol-blend fuels. The vapors from two river sand columns contaminated with gasoline and gasoline-ethanol were monitored for 77 d. Standards mixtures (batch tests) of benzene, toluene, and xylenes with different ethanol contents were also analyzed for evaporation rates studies. The instrumental analysis was performed via gas chromatography. The concentration of benzene in the vapor phase of the gasoline-ethanol column was decreased by 89.09%, considering the entire experimental period, whereas the toluene and xylenes concentrations were increased by 239.34 and 251.78%, respectively. In the batch tests, the benzene concentration in the vapor phase varied from 0.4 to 0.9 mg/L for ethanol concentrations (v/v) of 5 and 10%, respectively. For ethanol concentrations higher than 10%, no important changes in the benzene concentration were observed. The toluene exponentially increases between 20 and 30% ethanol concentration. and the maximum concentration of xylenes was observed when the ethanol concentration was 20% (v/v). These results suggest that the benzene evaporation behavior is preferentially affected by the interactions among ethanol and other aromatic compounds rather than the ethanol concentration itself. The evaporation behaviors of toluene and xylenes are directly dependent on the ethanol content.