The treatment of ethanol vapors in biotrickling filters for air pollution control was investigate... more The treatment of ethanol vapors in biotrickling filters for air pollution control was investigated. Two reactors were operated in parallel, one at ambient temperature (22°C) and one at high temperature (53°C). After a short adaptation phase, the removal of ethanol was similar in both reactors. At a bed contact time of 57 s, the elimination capacity exceeded 220 g m -3 h -1 at both temperatures. The experiments performed revealed that the process was most likely limited by biodegradation in the biofilm. The high-temperature biotrickling filter exhibited a higher degree of ethanol mineralization to CO 2 (60 vs 46% at ambient temperature); hence, a lower rate of biomass accumulation was observed. Plating and cultivation of biofilm samples revealed that the high-temperature biotrickling filter hosted a process culture composed of both mesophilic and thermotolerant or thermophilic microorganisms, whereas the ambient-temperature reactor lacked microorganisms capable of growing at high temperature. Consequently, the performance of the control biotrickling filter was significantly affected by a short incursion at 53°C. The upper temperature limit for treatment was 62°C. Overall, the results of this study open new possibilities for biotrickling filtration of hot gases.
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.
Http Dx Doi Org 10 1080 09593330902838106, May 13, 2009
Moisture control is one the most important parameters in biofilters for air pollution control. Bi... more Moisture control is one the most important parameters in biofilters for air pollution control. Biofilters tend to experience drying at the air inlet port, which causes decreased pollutant removal over time. In this study, the installation of an irrigation system within the lower part of the biofilter bed was proposed, and its effect was quantified in a laboratory scale biofilter operated side by side with a control biofilter. The removal of toluene vapours at short gas residence time (13.5 s) served as a model system. The results showed that the rate of toluene elimination in the biofilter with the lower irrigation system was 1.2-1.7 times greater than the rate of toluene elimination in the control biofilter. At the completion of the two-month experiment, a detailed examination was conducted of the packing materials with the immobilized pollutant-degrading culture. The results highlighted the effects of bed drying on cell viability in the control biofilter. They also revealed that the bottom segment of the biofilter with the lower irrigation system had a higher moisture content, a higher biomass density and a larger fraction of active biomass than the corresponding segment in the conventional biofilter. These detailed examinations explained why an increased toluene removal was observed in the system equipped with a lower irrigation system. Overall, this study demonstrates enhanced pollutant removal in biofilters equipped with a lower irrigation system through a better control of moisture.
Crystalline maghemite (␥-Fe 2 O 3 ) nanoparticles were cathodically electrodeposited at room temp... more Crystalline maghemite (␥-Fe 2 O 3 ) nanoparticles were cathodically electrodeposited at room temperature from environmentally benign electrolytes. The shape, size, and production rate of nanoparticles were strongly influenced by electrochemical conditions (e.g. FeCl 3 concentration, current density). X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis indicated that randomly oriented polycrystalline maghemite nanoparticles were synthesized with the and peaks as the main diffraction peaks. Transmission electron microscopy (TEM) images revealed that average particle size decreased from approximately 23 to 7 nm with increased current density. Magnetic saturation (M S ) of maghemite nanoparticles was determined to be 66 emu g −1 (66 Am 2 kg −1 ) at 300 K. The present maghemite nanoparticles showed a greater As(V) adsorption compared to iron nanoparticles, which might be attributed to a higher specific surface area.
Contamination of groundwater with the gasoline additive methyl tert-butyl ether (MTBE) is often a... more Contamination of groundwater with the gasoline additive methyl tert-butyl ether (MTBE) is often accompanied by many aromatic components such as benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene (BTEX). In this study, a laboratory-scale biotrickling filter for groundwater treatment inoculated with a microbial consortium degrading MTBE was studied. Individual or mixtures of BTEX compounds were transiently loaded in combination with MTBE. The results indicated that single BTEX compound or BTEX mixtures inhibited MTBE degradation to varying degrees, but none of them completely repressed the metabolic degradation in the biotrickling filter. Tert-butyl alcohol (TBA), a frequent co-contaminant of MTBE had no inhibitory effect on MTBE degradation. The bacterial consortium was stable and showed promising capabilities to remove TBA, ethylbenzene and toluene, and partially degraded benzene and xylenes without significant lag time. The study suggests that it is feasible to deploy a mixed bacterial consortia to degrade MTBE, BTEX and TBA at the same time.
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.
We report the development of an electrochemical disinfection system for human urine, which does n... more We report the development of an electrochemical disinfection system for human urine, which does not require the addition of any external water or chemical reagents. It is designed to minimize energy consumption so that it may be powered from point-of-use sources such as photovoltaic solar panels. The system will be part of a modular outdoor toilet for use in less developed countries. Initial tests were conducted with a physiological saline solution and an organic dye to determine minimum-energy operating conditions. Disinfection was then quantified using synthetic urine and E. coli as the indicator organism. The colony forming unit (CFU) count of E. Coli was reduced from >10 9 CFU/100 mL to <1000 CFU/100 mL, World Health Organization permissible limits after treatment [World Health Organization, Guidelines for the safe use of wastewater, excreta and greywater, ]. The effects of suspended fecal matter on disinfection efficiency were also studied.
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.
Proceedings International Conference on MEMS, NANO and Smart Systems, 2003
Biofilms form in nearly every environment that provides a surface, nutrients, and water. They can... more Biofilms form in nearly every environment that provides a surface, nutrients, and water. They can be found, for example, in almost all natural aquatic environments; on teeth, bone interstices, and oral epithelia of animals and humans; on hulls of marine installations and ship bottoms; on prosthetic devices and medical implants; on water conduits and in filters; and even ion the "sterile" surfaces of the computer chip manufacturing industry. The generally accepted stages in the development of microbial biofilms are transport to the surface, initial attachment, "more permanent" adhesion, proliferation, and biofilm formation . In some of the systems described above transport is dominated by microorganism mobility (combination of thermal diffusion and motility), in others convective drag forces influence the transport of microbes toward the surface of interest. Once in close proximity to a surface, microorganisms may initially attach via any combination of intermolecular (van der Waals), electrostatic, or hydrophobic forces like simple colloids, and later become more permanently adhered by exuding extra-cellular polymeric substances (EPS).
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.
Journal of the Air & Waste Management Association, 1999
To date, biofilters have been used primarily to control dilute, usually odorous, off-gases with r... more To date, biofilters have been used primarily to control dilute, usually odorous, off-gases with relatively low volatile organic compound (VOC) concentrations (<1 g m -3 ) and VOC loads (<50 g m -3 hr -1 ). Recently, however, U.S. industry has shown an interest in applying biofilters to higher concentrations of VOCs and hazardous air pollutants (HAPs).
Journal of the Air & Waste Management Association, 2006
Four different biofilter packing materials (two porous ceramics, perlite, and open pore polyureth... more Four different biofilter packing materials (two porous ceramics, perlite, and open pore polyurethane foam) were compared for the removal of toluene vapors. The focus was on evaluating performance at relatively short gas retention time (13.5 and 27 sec). The reactors were initially operated as biotrickling filters with continuous feeding and trickling of a nutrient solution. After significant plugging of the biotrickling filter beds with biomass was observed, the operation mode was switched to biofiltration with only periodic supply of mineral nutrients. This resulted in stable conditions, which allowed detailed investigations over Ͼ6 months. The reactor packed with cattle bone Porcelite (CBP), a ceramic material containing some macronutrients and micronutrients, exhibited the highest performance. The critical load (i.e., load at which 95% removal occurred) was 29 g m Ϫ3 hr Ϫ1 at a gas retention time of 13.5 sec and 66 g m Ϫ3 hr Ϫ1 at a gas retention time of 27 sec. After the long-term experiment, the packing materials were taken from the reactors and examined. The reactors were divided into three sections, top, middle, and bottom, to determine whether spatial differentiation of biomass occurred. The assays included a double-staining technique to count total and live microorganisms and determination of moisture, protein, and dry weight contents. Microbial community analysis was also conducted by denaturing gradient gel electrophoresis. The results showed that most reactors had a significant fraction of inactive biomass. Comparatively, the CBP biofilter held significantly higher densities of active biomass, which may be the reason for the higher toluene removal performance. The analyses suggest that favorable material properties and the nutrients slowly released by the CBP provided better environmental conditions for the process culture.
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 ...
Moisture control is one the most important parameters in biofilters for air pollution control. Bi... more Moisture control is one the most important parameters in biofilters for air pollution control. Biofilters tend to experience drying at the air inlet port, which causes decreased pollutant removal over time. In this study, the installation of an irrigation system within the lower part of the biofilter bed was proposed, and its effect was quantified in a laboratory scale biofilter operated side by side with a control biofilter. The removal of toluene vapours at short gas residence time (13.5 s) served as a model system. The results showed that the rate of toluene elimination in the biofilter with the lower irrigation system was 1.2-1.7 times greater than the rate of toluene elimination in the control biofilter. At the completion of the two-month experiment, a detailed examination was conducted of the packing materials with the immobilized pollutant-degrading culture. The results highlighted the effects of bed drying on cell viability in the control biofilter. They also revealed that the bottom segment of the biofilter with the lower irrigation system had a higher moisture content, a higher biomass density and a larger fraction of active biomass than the corresponding segment in the conventional biofilter. These detailed examinations explained why an increased toluene removal was observed in the system equipped with a lower irrigation system. Overall, this study demonstrates enhanced pollutant removal in biofilters equipped with a lower irrigation system through a better control of moisture.
Emissions of H 2 S from publicly owned treatment works is a serious problem, therefore collection... more Emissions of H 2 S from publicly owned treatment works is a serious problem, therefore collection and treatment of these emissions is essential. In this work, the performance of a bench scale activated sludge system used for the removal of H 2 S from foul air was investigated, and the effects of H 2 S concentration (5 to 50 ppm v ) on COD reduction and biomass settleability were studied. After biomass acclimation, the reactor was operated in a continuous mode at a hydraulic retention time of 5 h and a mean cell residence time of 6 days. Results showed that COD and H 2 S removal were 93.5 and 94.5%, respectively. Furthermore, H 2 S concentration up to 50 ppm v did not significantly affect the COD reduction. H 2 S loading rates of up to 7.5 mg H2S g -1 MLSS d -1 were treated with greater than 94% efficiency. The only adverse effect of H 2 S that was observed was an increase in the sludge volume index at loading rates over 4.5 mg H2S g -1 MLSS d -1 , at which bulking of the sludge occurred. Overall, the results indicate that H 2 S at concentrations usually emitted from wastewater treatment processes (lower than 50 ppm v ), can be efficiently treated by diffusion into activated sludge without compromising the performance of the activated sludge process.
The treatment of ethanol vapors in biotrickling filters for air pollution control was investigate... more The treatment of ethanol vapors in biotrickling filters for air pollution control was investigated. Two reactors were operated in parallel, one at ambient temperature (22°C) and one at high temperature (53°C). After a short adaptation phase, the removal of ethanol was similar in both reactors. At a bed contact time of 57 s, the elimination capacity exceeded 220 g m -3 h -1 at both temperatures. The experiments performed revealed that the process was most likely limited by biodegradation in the biofilm. The high-temperature biotrickling filter exhibited a higher degree of ethanol mineralization to CO 2 (60 vs 46% at ambient temperature); hence, a lower rate of biomass accumulation was observed. Plating and cultivation of biofilm samples revealed that the high-temperature biotrickling filter hosted a process culture composed of both mesophilic and thermotolerant or thermophilic microorganisms, whereas the ambient-temperature reactor lacked microorganisms capable of growing at high temperature. Consequently, the performance of the control biotrickling filter was significantly affected by a short incursion at 53°C. The upper temperature limit for treatment was 62°C. Overall, the results of this study open new possibilities for biotrickling filtration of hot gases.
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.
Http Dx Doi Org 10 1080 09593330902838106, May 13, 2009
Moisture control is one the most important parameters in biofilters for air pollution control. Bi... more Moisture control is one the most important parameters in biofilters for air pollution control. Biofilters tend to experience drying at the air inlet port, which causes decreased pollutant removal over time. In this study, the installation of an irrigation system within the lower part of the biofilter bed was proposed, and its effect was quantified in a laboratory scale biofilter operated side by side with a control biofilter. The removal of toluene vapours at short gas residence time (13.5 s) served as a model system. The results showed that the rate of toluene elimination in the biofilter with the lower irrigation system was 1.2-1.7 times greater than the rate of toluene elimination in the control biofilter. At the completion of the two-month experiment, a detailed examination was conducted of the packing materials with the immobilized pollutant-degrading culture. The results highlighted the effects of bed drying on cell viability in the control biofilter. They also revealed that the bottom segment of the biofilter with the lower irrigation system had a higher moisture content, a higher biomass density and a larger fraction of active biomass than the corresponding segment in the conventional biofilter. These detailed examinations explained why an increased toluene removal was observed in the system equipped with a lower irrigation system. Overall, this study demonstrates enhanced pollutant removal in biofilters equipped with a lower irrigation system through a better control of moisture.
Crystalline maghemite (␥-Fe 2 O 3 ) nanoparticles were cathodically electrodeposited at room temp... more Crystalline maghemite (␥-Fe 2 O 3 ) nanoparticles were cathodically electrodeposited at room temperature from environmentally benign electrolytes. The shape, size, and production rate of nanoparticles were strongly influenced by electrochemical conditions (e.g. FeCl 3 concentration, current density). X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis indicated that randomly oriented polycrystalline maghemite nanoparticles were synthesized with the and peaks as the main diffraction peaks. Transmission electron microscopy (TEM) images revealed that average particle size decreased from approximately 23 to 7 nm with increased current density. Magnetic saturation (M S ) of maghemite nanoparticles was determined to be 66 emu g −1 (66 Am 2 kg −1 ) at 300 K. The present maghemite nanoparticles showed a greater As(V) adsorption compared to iron nanoparticles, which might be attributed to a higher specific surface area.
Contamination of groundwater with the gasoline additive methyl tert-butyl ether (MTBE) is often a... more Contamination of groundwater with the gasoline additive methyl tert-butyl ether (MTBE) is often accompanied by many aromatic components such as benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene (BTEX). In this study, a laboratory-scale biotrickling filter for groundwater treatment inoculated with a microbial consortium degrading MTBE was studied. Individual or mixtures of BTEX compounds were transiently loaded in combination with MTBE. The results indicated that single BTEX compound or BTEX mixtures inhibited MTBE degradation to varying degrees, but none of them completely repressed the metabolic degradation in the biotrickling filter. Tert-butyl alcohol (TBA), a frequent co-contaminant of MTBE had no inhibitory effect on MTBE degradation. The bacterial consortium was stable and showed promising capabilities to remove TBA, ethylbenzene and toluene, and partially degraded benzene and xylenes without significant lag time. The study suggests that it is feasible to deploy a mixed bacterial consortia to degrade MTBE, BTEX and TBA at the same time.
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.
We report the development of an electrochemical disinfection system for human urine, which does n... more We report the development of an electrochemical disinfection system for human urine, which does not require the addition of any external water or chemical reagents. It is designed to minimize energy consumption so that it may be powered from point-of-use sources such as photovoltaic solar panels. The system will be part of a modular outdoor toilet for use in less developed countries. Initial tests were conducted with a physiological saline solution and an organic dye to determine minimum-energy operating conditions. Disinfection was then quantified using synthetic urine and E. coli as the indicator organism. The colony forming unit (CFU) count of E. Coli was reduced from >10 9 CFU/100 mL to <1000 CFU/100 mL, World Health Organization permissible limits after treatment [World Health Organization, Guidelines for the safe use of wastewater, excreta and greywater, ]. The effects of suspended fecal matter on disinfection efficiency were also studied.
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.
Proceedings International Conference on MEMS, NANO and Smart Systems, 2003
Biofilms form in nearly every environment that provides a surface, nutrients, and water. They can... more Biofilms form in nearly every environment that provides a surface, nutrients, and water. They can be found, for example, in almost all natural aquatic environments; on teeth, bone interstices, and oral epithelia of animals and humans; on hulls of marine installations and ship bottoms; on prosthetic devices and medical implants; on water conduits and in filters; and even ion the "sterile" surfaces of the computer chip manufacturing industry. The generally accepted stages in the development of microbial biofilms are transport to the surface, initial attachment, "more permanent" adhesion, proliferation, and biofilm formation . In some of the systems described above transport is dominated by microorganism mobility (combination of thermal diffusion and motility), in others convective drag forces influence the transport of microbes toward the surface of interest. Once in close proximity to a surface, microorganisms may initially attach via any combination of intermolecular (van der Waals), electrostatic, or hydrophobic forces like simple colloids, and later become more permanently adhered by exuding extra-cellular polymeric substances (EPS).
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.
Journal of the Air & Waste Management Association, 1999
To date, biofilters have been used primarily to control dilute, usually odorous, off-gases with r... more To date, biofilters have been used primarily to control dilute, usually odorous, off-gases with relatively low volatile organic compound (VOC) concentrations (<1 g m -3 ) and VOC loads (<50 g m -3 hr -1 ). Recently, however, U.S. industry has shown an interest in applying biofilters to higher concentrations of VOCs and hazardous air pollutants (HAPs).
Journal of the Air & Waste Management Association, 2006
Four different biofilter packing materials (two porous ceramics, perlite, and open pore polyureth... more Four different biofilter packing materials (two porous ceramics, perlite, and open pore polyurethane foam) were compared for the removal of toluene vapors. The focus was on evaluating performance at relatively short gas retention time (13.5 and 27 sec). The reactors were initially operated as biotrickling filters with continuous feeding and trickling of a nutrient solution. After significant plugging of the biotrickling filter beds with biomass was observed, the operation mode was switched to biofiltration with only periodic supply of mineral nutrients. This resulted in stable conditions, which allowed detailed investigations over Ͼ6 months. The reactor packed with cattle bone Porcelite (CBP), a ceramic material containing some macronutrients and micronutrients, exhibited the highest performance. The critical load (i.e., load at which 95% removal occurred) was 29 g m Ϫ3 hr Ϫ1 at a gas retention time of 13.5 sec and 66 g m Ϫ3 hr Ϫ1 at a gas retention time of 27 sec. After the long-term experiment, the packing materials were taken from the reactors and examined. The reactors were divided into three sections, top, middle, and bottom, to determine whether spatial differentiation of biomass occurred. The assays included a double-staining technique to count total and live microorganisms and determination of moisture, protein, and dry weight contents. Microbial community analysis was also conducted by denaturing gradient gel electrophoresis. The results showed that most reactors had a significant fraction of inactive biomass. Comparatively, the CBP biofilter held significantly higher densities of active biomass, which may be the reason for the higher toluene removal performance. The analyses suggest that favorable material properties and the nutrients slowly released by the CBP provided better environmental conditions for the process culture.
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 ...
Moisture control is one the most important parameters in biofilters for air pollution control. Bi... more Moisture control is one the most important parameters in biofilters for air pollution control. Biofilters tend to experience drying at the air inlet port, which causes decreased pollutant removal over time. In this study, the installation of an irrigation system within the lower part of the biofilter bed was proposed, and its effect was quantified in a laboratory scale biofilter operated side by side with a control biofilter. The removal of toluene vapours at short gas residence time (13.5 s) served as a model system. The results showed that the rate of toluene elimination in the biofilter with the lower irrigation system was 1.2-1.7 times greater than the rate of toluene elimination in the control biofilter. At the completion of the two-month experiment, a detailed examination was conducted of the packing materials with the immobilized pollutant-degrading culture. The results highlighted the effects of bed drying on cell viability in the control biofilter. They also revealed that the bottom segment of the biofilter with the lower irrigation system had a higher moisture content, a higher biomass density and a larger fraction of active biomass than the corresponding segment in the conventional biofilter. These detailed examinations explained why an increased toluene removal was observed in the system equipped with a lower irrigation system. Overall, this study demonstrates enhanced pollutant removal in biofilters equipped with a lower irrigation system through a better control of moisture.
Emissions of H 2 S from publicly owned treatment works is a serious problem, therefore collection... more Emissions of H 2 S from publicly owned treatment works is a serious problem, therefore collection and treatment of these emissions is essential. In this work, the performance of a bench scale activated sludge system used for the removal of H 2 S from foul air was investigated, and the effects of H 2 S concentration (5 to 50 ppm v ) on COD reduction and biomass settleability were studied. After biomass acclimation, the reactor was operated in a continuous mode at a hydraulic retention time of 5 h and a mean cell residence time of 6 days. Results showed that COD and H 2 S removal were 93.5 and 94.5%, respectively. Furthermore, H 2 S concentration up to 50 ppm v did not significantly affect the COD reduction. H 2 S loading rates of up to 7.5 mg H2S g -1 MLSS d -1 were treated with greater than 94% efficiency. The only adverse effect of H 2 S that was observed was an increase in the sludge volume index at loading rates over 4.5 mg H2S g -1 MLSS d -1 , at which bulking of the sludge occurred. Overall, the results indicate that H 2 S at concentrations usually emitted from wastewater treatment processes (lower than 50 ppm v ), can be efficiently treated by diffusion into activated sludge without compromising the performance of the activated sludge process.
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Papers by Marc Deshusses