Presence Of BTEX Research Articles

Aerobic BTEX biodegradation increases yield of perfluoroalkyl carboxylic acids from biotransformation of a polyfluoroalkyl surfactant, 6:2 FtTAoS.

Aqueous film-forming foams (AFFFs) are important sources of per- and polyfluoroalkyl substances (PFASs) in soil, groundwater, and surface water. Soil microorganisms can convert polyfluorinated substances into persistent perfluoroalkyl acids, but the understanding of co-contaminant stimulation or inhibition of PFASs biotransformation is limited. In this study, we investigate how aerobic biotransformation of polyfluorinated substances was affected by common AFFF co-contaminants, such as gasoline aromatics: benzene, toluene, ethylbenzene, and o-xylene (BTEX). We performed aerobic microcosm studies by inoculating AFFF-impacted soil with medium containing 6:2 fluorotelomer thioether amido sulfonate (FtTAoS) and either diethyl glycol monobutyl ether (DGBE), a common AFFF ingredient, or BTEX compounds as the main carbon and energy source. BTEX-amended microcosms produced 4.3-5.3 fold more perfluoroalkyl carboxylates (PFCAs) than DGBE-amended ones, even though both organic carbon sources induced similar 6:2 FtTAoS biotransformation rates. In enrichments of AFFF-impacted solids selecting for BTEX biodegradation, we detected the presence of genes encoding toluene dioxygenase as well as larger abundances of transformation products from thioether oxidation that complement larger quantities of terminal transformation products. Our findings indicate that enrichment of BTEX-degrading microorganisms in the AFFF-impacted soil enhanced the conversion of 6:2 FtTAoS to PFCAs. These results provide insights into the high ratio of PFAAs to precursors at AFFF-impacted sites with history of BTEX bioremediation.

Using dynamic flux chambers to estimate the natural attenuation rates in the subsurface at petroleum contaminated sites

In this work, we introduce a screening method for the evaluation of the natural attenuation rates in the subsurface at sites contaminated by petroleum hydrocarbons. The method is based on the combination of the data obtained from standard source characterization with dynamic flux chambers measurements. The natural attenuation rates are calculated as difference between the flux of contaminants estimated with a non-reactive diffusive model starting from the concentrations of the contaminants detected in the source (soil and/or groundwater) and the effective emission rate of the contaminants measured using dynamic flux chambers installed at ground level. The reliability of this approach was tested in a contaminated site characterized by the presence of BTEX in soil and groundwater. Namely, the BTEX emission rates from the subsurface were measured in 4 seasonal campaigns using dynamic flux chambers installed in 14 sampling points. The comparison of measured fluxes with those predicted using a non-reactive diffusive model, starting from the source concentrations, showed that, in line with other recent studies, the modelling approach can overestimate the expected outdoor concentration of petroleum hydrocarbons even up to 4 orders of magnitude. On the other hand, by coupling the measured data with the fluxes estimated with the diffusive non-reactive model, it was possible to perform a mass balance to evaluate the natural attenuation loss rates of petroleum hydrocarbons during the migration from the source to ground level. Based on this comparison, the estimated BTEX loss rates in the test site were up to almost 0.5kg/year/m2. These rates are in line with the values reported in the recent literature for natural source zone depletion. In short, the method presented in this work can represent an easy-to-use and cost-effective option that can provide a further line of evidence of natural attenuation rates expected at contaminated sites.

Biodegradation of n -hexane as single pollutant and in a mixture with BTEX in a scoria/compost-based biofilter

Abstract This study evaluated the biodegradation of n -hexane as single pollutant, and in a mixture with benzene, toluene, ethylbenzene, and xylenes (BTEX) in a scoria/compost-based biofilter. Initially, the biofilter was fed with n -hexane and maximum elimination capacities (EC max ) of 10.7 and 8.1 g m −3 h −1 were obtained for inlet loading rates (ILR) of 14.0 and 11.6 g m −3 h −1 at empty bed retention times (EBRT) of 138 and 108 s, respectively. Michaelis–Menten kinetic model was well fitted to the experimental EC of n -hexane in the single pollutant condition. In the presence of BTEX, the removal efficiency of n -hexane dramatically decreased from 76 to 21% at EBRT of 108 s. In this condition, BTEX was easily degraded with an EC max of 110.6 g m −3 h −1 for ILR of 119.1 g m −3 h −1 . A competitive inhibition kinetic well described the n -hexane removal in the presence of BTEX with an inhibition constant of 0.151 g m −3 . Moreover, the interaction index of benzene with the addition of BTEX was −0.702, indicating the significant inhibitory effect of BTEX on n -hexane biodegradation. This study revealed that, in the biofiltration of n -hexane/BTEX mixture, a significant decrease in BTEX concentration is a prerequisite for the efficient removal of n -hexane.

Avaliação do uso da cromatografia gasosa para detecção de hidrocarbonetos monoaromáticos na água subterrânea na região norte do município de Fortaleza (CE)

A contaminação das águas subterrâneas por derivados do petróleo, como a gasolina é um dos principais impactos causados pela atividade comercial varejista de revenda de combustíveis automotivos. Uma das formas de se detectar esse tipo de impacto é realizar a caracterização da qualidade das águas subterrâneas próximas a esses locais quanto à presença de hidrocarbonetos monoaromáticos, como benzeno, tolueno, etilbenzeno e os isômeros do xileno (BTEX). Nesse sentido, buscou-se caracterizar a qualidade da água subterrânea quanto à presença de BTEX na região norte do município de Fortaleza - CE, área de estudo desta pesquisa. Para isso, foi implantada a metodologia analítica de detecção dos BTEX por cromatografia gasosa, acoplada aos detectores PID (fotoionização) e FID (ionização em chama), antecedida da técnica de pré-concentração da amostra headspace estático. O método foi validado através da avaliação dos parâmetros seletividade, linearidade, precisão (repetibilidade), exatidão (recuperação), limite de detecção (LD) e limite de quantificação (LQ). A amostragem da água subterrânea foi realizada pelo método de baixa-vazão, conforme a norma ABNT NBR 15847/2010, com o auxílio de um sistema de amostragem automatizado - Low-Flow Sampling, em 11 poços de monitoramento. O método analítico mostrou-se bastante seletivo, repetitivo, linear, apresentou boa recuperação (70 a 110%) e baixos limites de detecção (0,01 a 0,08 µg/L) e limite de quantificação (0,04 a 0,32 µg/L). Os compostos BTEX foram detectados em todos os poços monitorados, entretanto as concentrações medidas ficaram muito a baixo dos valores máximos estabelecidos pela Resolução CONAMA 396/2008, que é de 5 µg.L-1, 170 µg.L-1, 200 µg.L-1 e 300µg.L-1, para o benzeno, tolueno, etilbenzeno e xilenos, respectivamente.

DEGRADATION OF AROMATIC PETROLEUM HYDROCARBONS (BTEX) BY A SOLVENT TOLERANT BACTERIAL CONSORTIUM

Petroleum aromatic hydrocarbons like benzene, toluene, ethyl benzene and xylene, together known as BTEX, has almost the same chemical structure. These aromatic hydrocarbons are released as pollutants in the environment. This work was taken up to develop a solvent tolerant bacterial consortium that could degrade BTEX compounds as they all share a common chemical structure. We have isolated almost 60 different types of bacterial strains from different petroleum contaminated sites. Of these 60 bacterial strains almost 20 microorganisms were screened on the basis of capability to tolerate high concentration of BTEX. Ten different consortia were prepared and the compatibility of the bacterial strains within the consortia was checked by gram staining and BTEX tolerance level. Four successful microbial consortia were selected in which all the bacterial strains concomitantly grew in presence of high concentration of BTEX (10% of toluene, 10% of benzene 5% ethyl benzene and 1 % xylene). Consortium no 2 showed the highest growth rate in presence of BTEX. Degradation of BTEX by consortium no 2 was monitored for 5 days by gradual decrease in the volume of the solvents. The maximum reduction observed was 85% in 5 days. Gas chromatography results also reveal that could completely degrade benzene and ethyl benzene within 48 hours. Almost 90% degradation of toluene and xylene in 48 hours was exhibited by consortium no 2. It could also tolerate and degrade many industrial solvents such as chloroform, DMSO, acetonitrile having a wide range of log P values (0.03 - 3.1). Degradation of aromatic hydrocarbon like BTEX by a solvent tolerant bacterial consortium is greatly significant as it could degrade high concentration of pollutants compared to a bacterium and also reduces the time span of degradation.

DEGRADATION OF AROMATIC PETROLEUM HYDROCARBONS (BTEX) BY A SOLVENT TOLERANT BACTERIAL CONSORTIUM

Petroleum aromatic hydrocarbons like benzene, toluene, ethyl benzene and xylene, together known as BTEX, has almost the same chemical structure. These aromatic hydrocarbons are released as pollutants in the environment. This work was taken up to develop a solvent tolerant bacterial consortium that could degrade BTEX compounds as they all share a common chemical structure. We have isolated almost 60 different types of bacterial strains from different petroleum contaminated sites. Of these 60 bacterial strains almost 20 microorganisms were screened on the basis of capability to tolerate high concentration of BTEX. Ten different consortia were prepared and the compatibility of the bacterial strains within the consortia was checked by gram staining and BTEX tolerance level. Four successful microbial consortia were selected in which all the bacterial strains concomitantly grew in presence of high concentration of BTEX (10% of toluene, 10% of benzene 5% ethyl benzene and 1 % xylene). Consortium no 2 showed the highest growth rate in presence of BTEX. Degradation of BTEX by consortium no 2 was monitored for 5 days by gradual decrease in the volume of the solvents. The maximum reduction observed was 85% in 5 days. Gas chromatography results also reveal that could completely degrade benzene and ethyl benzene within 48 hours. Almost 90% degradation of toluene and xylene in 48 hours was exhibited by consortium no 2. It could also tolerate and degrade many industrial solvents such as chloroform, DMSO, acetonitrile having a wide range of log P values (0.03 - 3.1). Degradation of aromatic hydrocarbon like BTEX by a solvent tolerant bacterial consortium is greatly significant as it could degrade high concentration of pollutants compared to a bacterium and also reduces the time span of degradation.

Biodegradation of alkylates under less agitated aquifer conditions

The biodegradability of three alkylates (2,3-dimethylpentane, 2,4-dimethylpentane and 2,2,4-trimethylpentane) under less agitated aquifer conditions was investigated in this study. All three alkylates biodegraded completely under these conditions regardless of the presence or absence of ethanol or benzene, toluene, ethylbenzene, and xylenes (BTEX) in the feed. In the presence of ethanol, alkylates degradation was not inhibited by ethanol. However, alkylates degraded more slowly in the presence of BTEX suggesting competitive inhibition to microbial utilization of alkylates. In the sterile controls, alkylates concentrations remained unchanged throughout the experiments.

Biodegradability of alkylates as a sole carbon source in the presence of ethanol or BTEX

The biodegradability of alkylate compounds in serum bottles was investigated in the presence and absence of ethanol or benzene, toluene, ethylbenzene, and p-xylene (BTEX). The biomass was acclimated to three different alkylates, 2,3-dimethylpentane, 2,4-dimethylpentane and 2,2,4-trimethylpentane in porous pot reactors. The alkylates were completely mineralized in all three sets of experiments. They degraded more slowly in the presence of BTEX than in their absence because BTEX inhibited the microbial utilization of alkylates. However, in the presence of ethanol, their slower biodegradation was not related to inhibition by the ethanol. Throughout the experiments alkylates, ethanol, and BTEX concentrations did not change in the sterile controls.

Biodegradability of Alternative Oxygenates as a Sole Carbon Source or in the Presence of Btex

Biodegradability of Alternative Oxygenates as a Sole Carbon Source or in the Presence of Btex

95/00217 Effects of modified poly(vinyl alcohol)s as a dispersant for coal-water slurry

The biodegradability of alkylate compounds in serum bottles was investigated in the presence and absence of ethanol or benzene, toluene, ethylbenzene, and p-xylene (BTEX). The biomass was acclimated to three different alkylates, 2,3-dimethylpentane, 2,4-dimethylpentane and 2,2,4-trimethylpentane in porous pot reactors. The alkylates were completely mineralized in all three sets of experiments. They degraded more slowly in the presence of BTEX than in their absence because BTEX inhibited the microbial utilization of alkylates. However, in the presence of ethanol, their slower biodegradation was not related to inhibition by the ethanol. Throughout the experiments alkylates, ethanol, and BTEX concentrations did not change in the sterile controls.