Environmental Science and Technology, Jan 10, 2008
Hydrogen sulfide (H2S) is a very common odor nuisance which is best controlled by chemical or bio... more Hydrogen sulfide (H2S) is a very common odor nuisance which is best controlled by chemical or biological scrubbing. Under alkaline pH, the amount of H2S that can be solubilized in a scrubbing liquid increases significantly, and therefore, gas-liquid mass transfer limitations can be reduced. To date, biological scrubbing of H2S has been limited to neutral or acidic pH, despite the potential benefit of reduced mass transfer limitations at alkaline pH. In the present paper, an alkaliphilic sulfoxidizing bacterial consortium was deployed in a laboratory-scale biotrickling filter treating H2S at pH 10. The gas contact time ranged from 1 to 6 s, and H2S inlet concentrations, from 2.5 to 18 ppm(v). The results showed that under most conditions, H2S removal exceeded 98% and the degradation end-product was sulfate. At the highest H2S concentrations and shortest gas contacttimes, when the loading exceeded 30 g m(-3) h(-1), the H2S removal efficiency decreased significantly due to biological reaction limitation, and incompletely oxidized sulfides were measured in the trickling liquid. An analysis of the process demonstrated that operating the biotrickling filter at high pH results in an enhancement of the mass transfer by a factor of 1700-11 000. Overall, alkaline biotrickling filtration was shown to be very effective at low concentration of H2S and very short gas contact time. This is the first demonstration of a biotrickling filter for air pollution control operated at high pH.
We report a sensitive, selective, and fast responding room temperature chemiresistive sensor for ... more We report a sensitive, selective, and fast responding room temperature chemiresistive sensor for hydrogen sulfide detection and quantification using polyaniline nanowires-gold nanoparticles hybrid network. The sensor was fabricated by facile electrochemical technique. Initially, polyaniline nanowires with a diameter of 250-320 nm bridging the gap between a pair of microfabricated gold electrodes were synthesized using templateless electrochemical polymerization using a two step galvanostatic technique. Polyaniline nanowires were then electrochemically functionalized with gold nanoparticles using cyclic voltammetry technique. These chemiresistive sensors show an excellent limit of detection (0.1 ppb), wide dynamic range (0.1-100 ppb), and very good selectivity and reproducibility.
The widespread use of methyl tert-butyl ether (MTBE) as a gasoline additive has resulted in a lar... more The widespread use of methyl tert-butyl ether (MTBE) as a gasoline additive has resulted in a large number of cases of groundwater contamination. Bioremediation is often proposed as the most promising alternative after treatment. However, MTBE biodegradation appears to be quite different from the biodegradation of usual gasoline contaminants such as benzene, toluene, ethyl benzene and xylene (BTEX). In the present paper, the characteristics of a consortium degrading MTBE in liquid cultures are presented and discussed. MTBE degradation rate was fast and followed zero order kinetics when added at 100 mg l(-1). The residual MTBE concentration in batch degradation experiments ranged from below the detection limit (1 microg l(-1)) to 50 microg l(-1). The specific activity of the consortium ranged from 7 to 52 mgMTBE g(dw)(-1) h(-1) (i.e. 19-141 mgCOD g(dw) (-1) h(-1)). Radioisotope experiments showed that 79% of the carbon-MTBE was converted to carbon-carbon dioxide. The consortium was a...
VOC biodegradation in waste air biofilters is discussed, and a general model for the description ... more VOC biodegradation in waste air biofilters is discussed, and a general model for the description of either the maximum elimination capacity or the load at which 95% pollutant removal occurs is presented and evaluated. The model used Henry's law coefficient, log of octanol-water partition, a molecular connectivity index and group contributions. Model parameters were calibrated using removal data for 17 compounds and excellent description of experimental data was achieved. Future efforts will focus on demonstrating the predictability of the model to improve its applicability for reactor design purposes.
ABSTRACT In the present paper, the possibility of using sulfur oxidizing denitrifying organisms f... more ABSTRACT In the present paper, the possibility of using sulfur oxidizing denitrifying organisms for NOx treatment in biotrickling filters is evaluated. In this approach, nitric oxide (NO) is used as an electron acceptor and various sulfur species are used as electron donors. Preliminary laboratory study showed that NO removal efficiency was between 25-90%, depending on the conditions of biotrickling filter (empty bed residence time (EBRT), gas composition). As expected the higher the EBRT, the better the removal of NO. More than 90% NO removal was achieved at an EBRT of 189 seconds. However, oxygen in the inlet gas inhibited the NO removal. At 0.5% oxygen the removal dropped from 12.4 to 7.7 g/m3 h. Overall, the research shows new possibilities for using autotrophic organisms in biotrickling filters for the treatment of combustion gases from power generation equipment.
Anaerobic digester effluent collected from a swine farm was nitrified in lab-scale bioreactors mi... more Anaerobic digester effluent collected from a swine farm was nitrified in lab-scale bioreactors mimicking an innovative manure management system to understand factors relevant to a successful start-up. The effects of digester effluent strength, aeration time, nitrifying sludge inoculation, and initial pH control on the startup of the nitrification system were investigated. The results showed that initial NH4+-N concentrations higher than 800 mg L−1 could severely inhibit the onset of nitrification if relying on native bacterial populations. When aeration time was increased from 4 to 12 h d−1, ammonium oxidation occurred earlier, but nitrite oxidation was delayed. However, the delay was not observed when bioaugmentation with nitrifying sludge was conducted. Initial addition of acid for pH control was unsuccessful as initial depletion of alkalinity eventually resulted in self-inhibition of nitrification cause by decreasing pH over time. Overall, these results provide guidance on how to effectively start large-scale innovative animal waste treatment systems.
Mercury emissions from coal combustion have become a global concern as growing energy demands hav... more Mercury emissions from coal combustion have become a global concern as growing energy demands have increased the consumption of coal. The effective implementation of treatment technologies requires knowledge of mercury speciation in the flue gas, namely concentrations of elemental, oxidized and particulate mercury at the exit of the boiler. A model that can accurately predict mercury species in flue gas would be very useful in that context. Here, a Bayesian regularized artificial neural network (BRANN) that uses five coal properties and combustion temperature was developed to predict mercury speciation in flue gases before treatment technology implementation. The results of the model show that up to 97 percent of the variation in mercury species concentration is captured through the use of BRANNs. The BRANN model was used to conduct a parametric sensitivity which revealed that the coal chlorine content and coal calorific value were the most sensitive parameters, followed by the combustion temperature. The coal sulfur content was the least important parameter. The results demonstrate the applicability of BRANNs for predicting mercury concentration and speciation in combustion flue gas and provide a more efficient and effective technique when compared to other advanced non-mechanistic modeling strategies.
Microcosms and column experiments were carried out using soil and groundwater from a MTBE contami... more Microcosms and column experiments were carried out using soil and groundwater from a MTBE contaminated site or using distilled water amended with mineral salts. The biodegradation of MTBE was tested under aerobic and anaerobic conditions ...
Environmental Science and Technology, Jan 10, 2008
Hydrogen sulfide (H2S) is a very common odor nuisance which is best controlled by chemical or bio... more Hydrogen sulfide (H2S) is a very common odor nuisance which is best controlled by chemical or biological scrubbing. Under alkaline pH, the amount of H2S that can be solubilized in a scrubbing liquid increases significantly, and therefore, gas-liquid mass transfer limitations can be reduced. To date, biological scrubbing of H2S has been limited to neutral or acidic pH, despite the potential benefit of reduced mass transfer limitations at alkaline pH. In the present paper, an alkaliphilic sulfoxidizing bacterial consortium was deployed in a laboratory-scale biotrickling filter treating H2S at pH 10. The gas contact time ranged from 1 to 6 s, and H2S inlet concentrations, from 2.5 to 18 ppm(v). The results showed that under most conditions, H2S removal exceeded 98% and the degradation end-product was sulfate. At the highest H2S concentrations and shortest gas contacttimes, when the loading exceeded 30 g m(-3) h(-1), the H2S removal efficiency decreased significantly due to biological reaction limitation, and incompletely oxidized sulfides were measured in the trickling liquid. An analysis of the process demonstrated that operating the biotrickling filter at high pH results in an enhancement of the mass transfer by a factor of 1700-11 000. Overall, alkaline biotrickling filtration was shown to be very effective at low concentration of H2S and very short gas contact time. This is the first demonstration of a biotrickling filter for air pollution control operated at high pH.
We report a sensitive, selective, and fast responding room temperature chemiresistive sensor for ... more We report a sensitive, selective, and fast responding room temperature chemiresistive sensor for hydrogen sulfide detection and quantification using polyaniline nanowires-gold nanoparticles hybrid network. The sensor was fabricated by facile electrochemical technique. Initially, polyaniline nanowires with a diameter of 250-320 nm bridging the gap between a pair of microfabricated gold electrodes were synthesized using templateless electrochemical polymerization using a two step galvanostatic technique. Polyaniline nanowires were then electrochemically functionalized with gold nanoparticles using cyclic voltammetry technique. These chemiresistive sensors show an excellent limit of detection (0.1 ppb), wide dynamic range (0.1-100 ppb), and very good selectivity and reproducibility.
The widespread use of methyl tert-butyl ether (MTBE) as a gasoline additive has resulted in a lar... more The widespread use of methyl tert-butyl ether (MTBE) as a gasoline additive has resulted in a large number of cases of groundwater contamination. Bioremediation is often proposed as the most promising alternative after treatment. However, MTBE biodegradation appears to be quite different from the biodegradation of usual gasoline contaminants such as benzene, toluene, ethyl benzene and xylene (BTEX). In the present paper, the characteristics of a consortium degrading MTBE in liquid cultures are presented and discussed. MTBE degradation rate was fast and followed zero order kinetics when added at 100 mg l(-1). The residual MTBE concentration in batch degradation experiments ranged from below the detection limit (1 microg l(-1)) to 50 microg l(-1). The specific activity of the consortium ranged from 7 to 52 mgMTBE g(dw)(-1) h(-1) (i.e. 19-141 mgCOD g(dw) (-1) h(-1)). Radioisotope experiments showed that 79% of the carbon-MTBE was converted to carbon-carbon dioxide. The consortium was a...
VOC biodegradation in waste air biofilters is discussed, and a general model for the description ... more VOC biodegradation in waste air biofilters is discussed, and a general model for the description of either the maximum elimination capacity or the load at which 95% pollutant removal occurs is presented and evaluated. The model used Henry's law coefficient, log of octanol-water partition, a molecular connectivity index and group contributions. Model parameters were calibrated using removal data for 17 compounds and excellent description of experimental data was achieved. Future efforts will focus on demonstrating the predictability of the model to improve its applicability for reactor design purposes.
ABSTRACT In the present paper, the possibility of using sulfur oxidizing denitrifying organisms f... more ABSTRACT In the present paper, the possibility of using sulfur oxidizing denitrifying organisms for NOx treatment in biotrickling filters is evaluated. In this approach, nitric oxide (NO) is used as an electron acceptor and various sulfur species are used as electron donors. Preliminary laboratory study showed that NO removal efficiency was between 25-90%, depending on the conditions of biotrickling filter (empty bed residence time (EBRT), gas composition). As expected the higher the EBRT, the better the removal of NO. More than 90% NO removal was achieved at an EBRT of 189 seconds. However, oxygen in the inlet gas inhibited the NO removal. At 0.5% oxygen the removal dropped from 12.4 to 7.7 g/m3 h. Overall, the research shows new possibilities for using autotrophic organisms in biotrickling filters for the treatment of combustion gases from power generation equipment.
Anaerobic digester effluent collected from a swine farm was nitrified in lab-scale bioreactors mi... more Anaerobic digester effluent collected from a swine farm was nitrified in lab-scale bioreactors mimicking an innovative manure management system to understand factors relevant to a successful start-up. The effects of digester effluent strength, aeration time, nitrifying sludge inoculation, and initial pH control on the startup of the nitrification system were investigated. The results showed that initial NH4+-N concentrations higher than 800 mg L−1 could severely inhibit the onset of nitrification if relying on native bacterial populations. When aeration time was increased from 4 to 12 h d−1, ammonium oxidation occurred earlier, but nitrite oxidation was delayed. However, the delay was not observed when bioaugmentation with nitrifying sludge was conducted. Initial addition of acid for pH control was unsuccessful as initial depletion of alkalinity eventually resulted in self-inhibition of nitrification cause by decreasing pH over time. Overall, these results provide guidance on how to effectively start large-scale innovative animal waste treatment systems.
Mercury emissions from coal combustion have become a global concern as growing energy demands hav... more Mercury emissions from coal combustion have become a global concern as growing energy demands have increased the consumption of coal. The effective implementation of treatment technologies requires knowledge of mercury speciation in the flue gas, namely concentrations of elemental, oxidized and particulate mercury at the exit of the boiler. A model that can accurately predict mercury species in flue gas would be very useful in that context. Here, a Bayesian regularized artificial neural network (BRANN) that uses five coal properties and combustion temperature was developed to predict mercury speciation in flue gases before treatment technology implementation. The results of the model show that up to 97 percent of the variation in mercury species concentration is captured through the use of BRANNs. The BRANN model was used to conduct a parametric sensitivity which revealed that the coal chlorine content and coal calorific value were the most sensitive parameters, followed by the combustion temperature. The coal sulfur content was the least important parameter. The results demonstrate the applicability of BRANNs for predicting mercury concentration and speciation in combustion flue gas and provide a more efficient and effective technique when compared to other advanced non-mechanistic modeling strategies.
Microcosms and column experiments were carried out using soil and groundwater from a MTBE contami... more Microcosms and column experiments were carried out using soil and groundwater from a MTBE contaminated site or using distilled water amended with mineral salts. The biodegradation of MTBE was tested under aerobic and anaerobic conditions ...
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