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Evaluation of a pilot-scale biotrickling filter as a VOC control technology for the plastic coating sector
Abstract
The performance and feasibility of a biotrickling filter (BTF) pilot unit for the treatment of exhaust gases from two robotic spray paint booths at a plastic coating facility were investigated. The volatile organic compound (VOC) concentrations in the emissions of the exhaust gases from the paint booths were relatively stable, although the VOC composition depended on the applied solvent-paint formulation in the booths. The pilot plant was operated for one year at empty bed residence times (EBRTs) ranging from 30 to 93s. The performance of the system was affected by the solvent-paint formulations. An EBRT between 30 and 40s was enough to meet legal requirements for products containing more than 60% biodegradable compounds, whereas a minimum EBRT of 80s was required for emissions mainly composed of hydrophobic VOCs. The dynamics of the microbial population was carried out by fluorescence in situ hybridisation (FISH), indicating a high microbial diversity with composition changes associated with the solvent-paint used. The feasibility of the BTF was evaluated, showing that this technology is economically and environmentally competitive in comparison with thermal treatment technology.
... To date, several pilots and field-scale biotreatment units have been successfully installed and deployed for removal of HAPs, VOCs and odors from various industrial air emission sources such as wood product industries, paint and coatings, paper and pulp and petrochemical facilities. [5][6][7][8] A field study was conducted between 1992 and 1994 by the petroleum environmental research forum (PERF) to remove volatile petroleum hydrocarbons (PHC) from two soil vapor extraction sites and one source of refinery wastewater with biofiltration. The results showed the removal efficiency (RE) of the aromatic compounds such as benzene and reduced sulfur compounds was more than 95% at empty bed residence time (EBRT) of one minute while light aliphatics needed a residence time of several minutes to achieve more than 70% removal efficiency. ...
... However, as indicated by other researchers, the degradation of benzene and alkylated benzenes which were the hazardous pollutants emitted from the tank battery would be high due to their higher solubility in water. 5,26 Inoculation and start-up of the system The biofilter microbial acclimation period, which can range from a few hours to months, is one important step which is needed to develop an optimum population of VOC-degrading microorganisms to achieve maximum removal efficiency. Relatively long start-up periods have been reported in full-scale bioreactors; as long as 8 weeks. ...
... reported the RE of 51% at an EBRT of 93 s for removal of VOCs from spray paint booths at a plastic coating facility, when the formulation of the solvent paint consisted of slowly biodegradable and hydrophobic compounds. 5 Generally, in biofilters the elimination capacity increases with the inlet loading rate of the pollutants until it reaches a maximum EC. However, in this field test, the actual maximum EC was not reached according to Fig. 6, and higher VOC loading rates should be tested in order to determine these thresholds. ...
BACKGROUND
Petrochemical refineries and production sites are considered to be the second greatest source of VOC emissions after vehicle exhausts. The feasibility and performance of a novel sequential biotrickling‐biofiltration unit for the treatment of a mixture of VOCs in the headspace of an oil and gas production tank battery was evaluated for three months at the Apache TAMU#2 well storage tank battery in Snook, Texas.
RESULTS
The results demonstrated that the main VOC constituents of the headspace of the storage tanks were alkanes along with smaller amounts of aromatics such as benzene, toluene and xylenes. Monitoring results for the biotreatment unit showed an average removal efficiency of 50–60% at an empty bed residence time of 120 s in each tank of the unit. After inoculation of the system with wastewater from a sedimentation basin of a local refinery, the removal efficiency of the system increased dramatically which demonstrated the importance of inoculation to achieve a rapid and successful start‐up in industrial biofilters. The most optimal performance was achieved after 77 days, obtaining the highest elimination capacity of 23 g m‐3 h‐1 at total VOCs loading rate of 39 g m‐3 h‐1.
CONCLUSION
The operation of the field‐scale sequential BTF‐BF unit for more than three months demonstrated the robustness of this technology and the degradation capabilities of a combination of the suspended and attached growth treatment. The project results demonstrated the potential for even more optimization for improved effectiveness of this novel biological treatment technology for removal of highly variable aromatic VOC concentrations. © 2017 Society of Chemical Industry
... Therefore, add-on control techniques have high applicability (Khan and Ghoshal, 2000). However, because the flue gas volume is large and the compositions and concentrations of VOCs from the painting process are very complicated, VOCs are not easy to control or remove (Alvarez-Hornos et al., 2011;Chang et al., 2002;Pierucci et al., 2005). Some popular control technologies were used and reported (Alvarez-Hornos et al., 2011;Hussey and Gupta, 1997;Stone, 1997). ...
... However, because the flue gas volume is large and the compositions and concentrations of VOCs from the painting process are very complicated, VOCs are not easy to control or remove (Alvarez-Hornos et al., 2011;Chang et al., 2002;Pierucci et al., 2005). Some popular control technologies were used and reported (Alvarez-Hornos et al., 2011;Hussey and Gupta, 1997;Stone, 1997). Thermal oxidizers such as regenerative thermal oxidizer and catalytic oxidizer are used to remove VOCs from coating processes. ...
A sampling system was designed to determine the composition ratios of VOCs emitted from 31 surface coating materials (SCMs). Representative architectural, automotive, and marine SCMs in Korea were investigated. Toluene, ethylbenzene, and xylene were the predominant VOCs. The VOC levels (wt%) from automotive SCMs were significantly higher than those from architectural and marine paints. It was found that target SCMs comprised mainly VOCs with 6-10 carbon atoms in molecules, which could be adsorbed by activated carbon. The saturated activated carbon which had already adsorbed toluene, ethylbenzene, and m-xylene was combusted. The saturated activated carbon was more combustible than new activated carbon because it comprised inflammable VOCs. Therefore, it could be an alternative fuel when using in a "fuelization system". To use the activated carbon as a fuel, a control technology of VOCs from a coating process was also designed and introduced.
... Numerous physical, chemical, and biological treatments for removing VOCs and other gases have been suggested in the literature (Bouzaza et al., 2004;Wang et al., 2007;Ralebitso-Senior et al., 2012;Padhi & Gokhale, 2014;Kureel et al., 2018;Pui et al., 2019). Of these treatments, biological treatments for VOCs have proven to be more advantageous due to lower economic and operational investments and a better removal rate of pollutants, leading to less secondary pollution (Álvarez-Hornos et al., 2011;Zamir et al., 2015;Yang et al., 2019). ...
Volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) are the major pollutants in industrial and agricultural emissions. This study targets the efficiency and applicability of biofiltration to remove methanol and n-hexane, two common air pollutants, using Chir pine cone nuts as filter media and Pseudomonas putida as the inoculant. The designed biofilter was operated between 25-35°C, with an airflow rate of 0.35 m3 h-1 and nutrient supply of 1-2 L Day-1. From a 60-day operating period, methanol's removal efficiency was higher than n-hexane, with a maximum removal efficiency of 93.91% achieved at an inlet loading rate of 101.39 g m-3h-1 for methanol and 87.96% at 398.46 g m-3h-1 for n-hexane. The effects of varying loading rates on the elimination capacity for both pollutants were also studied. In addition, the temperature profile of the biofilter, microbial analysis, and the BOD concentration of leachate was also studied during the operation period. The findings offer insights into the potential use of Chir pine nuts as filter media for the biodegradation of methanol and n-hexane and provide a foundation for future research to optimize the biofilter system's design and operation to increase its removal efficiency of other contaminants.
... Pilot plants are often employed to test the overall feasibility of selected technology (Álvarez-Hornos et al. 2011) and selected catalyst (Baldovino-Medrano et al. 2019) as well to access data on long-term reliability, identify possible technical problems, and also for economic evaluation before upscaling to full-scale industrial solution. It is the logical step to test the developed catalyst from the first stage of development in the more natural form of a monolith or spherical/pelletized shape to assess the activities or compare the different catalysts (Brummer et al. 2013) and provide benchmark testing with already developed and commercially adopted solutions and catalysts. ...
Catalytic oxidation of volatile organic compounds (VOCs) is a widely used method for VOC emissions mitigation essential for the long-term sustainability of clean and efficient industrial production. In this experimental study, chemical representatives of different VOC groups were subjected to deep catalytic oxidation on a pilot scale. State-of-the-art monolithic and spherical pelletized commercially available catalysts containing precious metals (Pt, Pd) as the active compounds were used. Experimental conditions (gas flow, high loads of VOC, and real flue gas mixture) were as close as possible to the real full-scale applications. For each catalyst and the tested VOC, a light-off curve was obtained and T50 and T90 values (temperatures corresponding to 50% and 90% conversions) were calculated. T50 and T90 values obtained in this pilot-scale study were compared with other laboratory-scale studies outcomes. T50 values are not significantly different; however, T90 are higher for the pilot scale. The interesting aspect of this comparison is to see if newly developed catalysts have better performance than already adopted and used commercial samples of VOC oxidation catalysts. The lowest T50 values were observed over Pt,Pd (1:1)—monolith sample, and lowest T90 over Pt,Pd/Al2O3,CeO2—pelletized catalyst.
Graphical abstract
CatOX pilot VOC emissions mitigation over noble metal catalysts
... Various VOCs control technologies were developed and applied such as adsorption, condensation, membrane separation, combustion, catalytic oxidation, and biological methods [4]. Biotrickling filter (BTF) is one of main bioreactors treating VOCs in biological methods due to its easy spraying and pH control, adaptation to hydrophilic VOCs and low pressure drop, and it come to be paid attention [5,6]. Some previous studies showed that the BTFs could effectively remove hydrophilic and biodegradable VOCs [7,8]. ...
The effects of rhamnolipid chelating La (III) or Nd (III) on m-dichlorobenzene removal and biofilm growth were investigated. The rhamnolipid chelating La (III) or Nd (III) significantly increased the average m-dichlorobenzene elimination capacity by 24% and 29%, respectively, on day 70–130, and the average wet weights of biomass ranged from 11 kg/m³ to 15 kg/m³ in BTFs on day 100–180 at an inlet load of at 47–98 gm³/h and an EBRT of 60s-90s. Microbial community functional genes about biofilm growth and m-dichlorobenzene removal were also increased. In addition, the rhamnolipid chelating La (III) or Nd (III) can improve the membrane permeability, extracellular polymeric substance (EPS) production, catechol 2,3 dioxygenase (C23O) enzyme, and chlorobenzene dioxygenase activity. These results demonstrate that rhamnolipid chelating La (III) or Nd (III) have the potential to improve the performance of BTFs treating hydrophobic and highly toxic VOCs.
... Biological molecular tools, such as fluorescence in situ hybridisation (FISH) [22,23], polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) [24,25], cloning and sequencing [26,27] and pyrosequencing [28,29], have been applied in the field of biofiltration. For example, Á lvarez-Hornos et al. [30] evaluated the dynamics of the microbial population using the FISH technique in a BTF pilot unit for the treatment of exhaust gases of a plastic coating facility. The pilot unit was inoculated with activated sludge and changes in the bacterial community were observed. ...
... Among the chemical industries, the solvent-based manufacturing like: paint, paper, resin, and adhesives contribute significantly to a mixture of VOCs production (e.g. toluene, benzene, xylene, etc.) in their effluents [36,37]. On the other hand, certain facilities, such as wastewater treatment plants, landfills and livestock emit CH 4 and several VOCs. ...
Hazardous airborne pollutants are frequently emitted to the atmosphere in the form of a gaseous mixture. Air biofilters as the primary biotechnological choice for waste gas treatment (low inlet concentration and high gas flow rate) should run properly when the feed contains multiple pollutants. Simultaneous removal of pollutants in biofilters has been extensively studied over the last 10 years. In this review, the results and findings of the mentioned studies including different groups of pollutants, such as methane (CH4) and volatile organic compounds (VOCs) are discussed. As the number of pollutants in a mixture increases, their elimination might become more complicated due to interactions between the pollutants. Parallel batch studies might be helpful to better understand these interaction effects in the absence of mass transfer limitations. Setting optimum operating conditions for removal of mixtures in biofilters is challenging because of opposing properties of pollutants. In biofilters, concerns, such as inlet gas composition variation and stability while dealing with abrupt inlet load and concentration changes, must be managed especially at industrial scales. Biofilters designed with multi-layer beds, allow tracking the fate of each pollutant as well as analyzing the diversity of microbial culture across the filter bed. Certain strategies are recommended to improve the performance of biofilters treating mixtures. For example, addition of (bio)surfactants as well as a second liquid phase in biotrickling filters might be considered for the elimination of multiple pollutants especially when hydrophobic pollutants are involved.
... Despite the success of biotrickling filters, situations exist, where satisfactory levels of exhaust gas purification could not be achieved. In particular, exhaust gases containing certain VOC (volatile organic compound) mixtures can be recalcitrant to bioremediation [13][14][15][16][17]. An industrial scale biofilter was inadequate for the degradation of VOCs from dip spin coating of metallic components, where the pollutants consisted of hydrophilic methoxypropyl acetate and hydrophobic xylene isomers. ...
This is a knowledge contribution to the unsatisfactory biodegradation problem, when biotrickling filters are purifying mixed paint solvents. A biotrickling filter manufacturer reported low biodegradation rates during the purification of a hydrocarbon pollutant mix from an industrial paint spraying floor. From a gas chromatograph/mass spectrometer analysis both hydrophilic and hydrophobic solvents were found in the polluted air. It is known that biodegradation is retarded, if the pollutant does not transfer from gas to liquid into the biofilm and it was therefore suspected that hydrophobic pollutants do not sufficiently migrate into the water/biofilm. To test this hypothesis, pure, rather than mixed pollutants, were injected into the abiotic biotrickling filter. When hydrophobic paint solvent (xylene) was sprayed into the biotrickling filter, the solvent load at the outlet of the filter was almost as high as at the inlet. But when pure, hydrophilic paint solvent (PGME) was sprayed into the abiotic biotrickling filter, the solvent load measured at the outlet of the filter was zero, indicating complete dissolution into the circulation water. Carbon/solvent loads at the filter outlet and inlet were measured with a portable flame ionization detector instrument. The experiment confirms that the hydrophobic solvent does not migrate into the liquid phase. This poor mass transfer of hydrophobic solvents is likely to be the reason for the low biodegradation rate. The result is highly relevant to the paint spraying industry and manufacturers of exhaust gas treatment equipment alike, who spend millions in non-sustainable incineration of exhaust gases.
... First, the process mechanism of the biofiltration of compounds with different hydrophobicity is not fully understood, revealing a considerably lower number of scientific papers discussing the biotrickling filtration of gas mixtures compared to the results of treating air polluted with a single component [23]. Second, real gas mixtures contain components with different chemical properties (affinity to aqueous phase, among others), thus resulting in a varied elimination capacity, depending on the types of compounds present in a gas stream [24][25][26][27][28][29]. ...
Biofiltration is a well-accepted method for the removal of malodorous compounds from air streams. Interestingly, the mechanisms underlying this process are not fully understood. The aim of this paper was to investigate the simultaneous removal of hydrophobic hexane with hydrophilic ethanol, resulting in the enhanced removal of hexane in the presence of ethanol. Investigations were performed in a peat-perlite packed biotrickling filter and the process performance was monitored using both gas chromatography and electronic nose techniques. The results indicate that the length as well as the efficiency of biofiltration during the start-up period depend on the feed composition, with higher efficiency obtained when hexane and ethanol were fed together from the process initiation. The experiments in the steady-state period present the biofilter performance when different ratios of hydrophilic to hydrophobic compounds were fed to the biofilter. The obtained results show the synergistic effects of the addition of a hydrophilic compound on the removal efficiency of hydrophobic hexane. The influence of the ratio of hydrophilic to hydrophobic compounds is discussed in terms of enhancing the mass transfer phenomena for hydrophobic volatile organic compounds.
... In this regard, previous studies pointed out that the cost of treating air emissions of different VOCs in several type of industrial sectors (coating, fibre-reinforced plastic) was significantly lower than that of conventional technologies such as a regenerative catalytic oxidizer [5] or a regenerative thermal oxidizer. [6] Acetone is one of the most widely used solvents in industrial processes due to its high volatility and non-harmful properties in comparison with other chemicals. Despite that fact, literature about the treatment of acetone air emissions by biofiltration is relatively scarce, [7][8][9][10][11] and only few sources deal with industrial applications of BTF. ...
A full-scale biotrickling filter (BTF) treating acetone air emissions of wood-coating activities showed difficulties to achieve outlet concentrations lower than 125 mg C m⁻³, especially for high inlet concentrations and oscillating emissions. To solve this problem, a laboratory investigation on acetone removal was carried out simulating typical industrial conditions: discontinuous and variable inlet concentrations and intermittent spraying. The results were evaluated in terms of removal efficiency and outlet gas emission pattern. Industrial emissions and operational protocols were simulated: inlet load up to 70 g C m⁻³ h⁻¹ during 2 cycles of 4 h per day and intermittent trickling of 15 min per hour. The outlet gas stream of the pollutant was affected by intermittent spraying, causing a fugitive emission of pollutant. Complete removal efficiency was obtained during non-spraying. Average removal efficiencies higher than 85% were obtained, showing the feasibility of BTF to treat acetone. The outlet gas stream showed a clear dependence on the pH of the trickling liquid, decreasing the removal at pH < 5.5. Thus, a proper control of alkalinity, with regular NaHCO3 addition, was required for successful operation. The laboratory findings were fruitfully transferred to the industry, and the removal of acetone by full-scale BTF was improved.
... Therefore, BTFs commonly perform better than biofilters, having greater stability and robustness while maintaining lower pressure drops. 9 ...
BACKGROUND
Biotrickling filters ( BTFs ) are among the most widely used biological technologies for air pollution control. The pollutant removal rate in BTFs relies to a large extent on its gas–liquid mass transfer performance. Therefore, knowledge of the design parameters affecting the mass transfer and mixing performance of full‐scale BTFs is of paramount importance.
RESULTS
This work showed that the height‐to‐diameter (H/D) ratio is an important parameter in the design of BTFs devoted to air pollution control. The H/D ratio significantly affected the mass transfer and mixing performance of the BTF with and without additional stirring in the holding tank. It was observed that under the same liquid velocity, the mass transfer coefficient ( k L a ) and the mixing time (t mix ) can be optimized only by selecting an adequate H/D ratio. Additional stirring in the holding tank also affected k L a and t mix , this effect being different for each H/D ratio tested.
CONCLUSIONS
The H/D ratio should be considered in the design of full‐scale BTFs since this parameter will significantly affect the mass transfer and mixing performance, regardless of the agitation conditions prevailing in the holding tank. As far as the authors know this is first report addressing the combined effect of the H/D ratio, liquid velocity and holding tank stirring on k L a and t mix in BTFs devoted to air pollution control. © 2017 Society of Chemical Industry
... For this reason, BTFs do not require prehumidification of the air, which reaches saturation rapidly. If compared with conventional biofilters, BTFs ensure greater stability of the process, better pH control, lower pressure drops and lower volume required (Á lvarez-Hornos et al., 2011;Copelli et al., 2012;Lebrero et al., 2014), thanks to the continuous trickling of water and nutrients (Mudliar et al, 2010). In recent years, BTFs have been adopted more and more frequently for biogas sweetening and to remove VOCs, ammonia and odors from industrial plants and wastewater treatments Torretta et al., 2013b). ...
The biological removal of pollutants, especially through biotrickling filters (BTFs), has recently become attractive for the low investment and operational costs and the low secondary pollution. This paper is intended to investigate the state of the art on BTF applications. After an overview on the biodegradation process and the typical parameters involved, this paper presents the analysis of a group of 16 literature studies chosen as the references for this sector. The reference studies differ from one another by the pollutants treated (volatile organic compounds [VOC], hydrogen sulphide, nitrogen oxides and trimethylamine), the geometry and size of the BTFs, and the procedures of the tests. The reference studies are analyzed and discussed in terms of the operational conditions and the results obtained, especially with respect to the removal efficiencies (REs) and the elimination capacities (ECs) of the pollutants considered. Empty bed residence time (EBRT), pollutant loading rate, temperature, pH, oxygen availability, trickling liquid flow rate, inoculum selection and biomass control strategies revealed to be the most important operational factors influencing the removal performance of a BTF.
... [8][9][10][11] In addition, a number of studies have examined methods of reducing emissions from surface coating facilities. 6,[12][13][14][15][16][17] Wadden et al. (1995) estimated VOC emissions for a sheetfed offset printing facility. 18 McCarthy and Senser (2006) developed a numerical model for paint transfer and deposition in electrostatic air sprays. ...
... Despite the success of biotrickling filters, situations exist, where satisfactory levels of exhaust gas purification could not be achieved. In particular, exhaust gases containing certain VOC (volatile organic compound) mixtures can be recalcitrant to bioremediation [13][14][15][16][17]. An industrial scale biofilter was inadequate for the degradation of VOCs from dip spin coating of metallic components, where the pollutants consisted of hydrophilic methoxypropyl acetate and hydrophobic xylene isomers. ...
Source separated food waste is a valuable feedstock for renewable energy production through anaerobic digestion, and a variety of collection schemes for this material have recently been introduced. The aim of this study was to identify options that maximise collection efficiency and reduce fuel consumption as part of the overall energy balance. A mechanistic model was developed to calculate the fuel consumption of kerbside collection of source segregated food waste, co-mingled dry recyclables and residual waste. A hypothetical city of 20,000 households was considered and nine scenarios were tested with different combinations of collection frequencies, vehicle types and waste types. The results showed that the potential fuel savings from weekly and fortnightly co-collection of household waste range from 7.4% to 22.4 % and 1.8% to 26.6% respectively, when compared to separate collection. A compartmentalised vehicle split 30:70 always performed better than one with two compartments of equal size. Weekly food waste collection with alternate weekly collection of the recyclables and residual waste by two-compartment collection vehicles was the best option to reduce the overall fuel consumption.
... A typical biofilter may contain colony forming units (CFU) of bacteria and actinomycetes in order of 10 6-10 10 , and of fungi in order of 10 3-10 6 g À1 of bed [56]. Lastly, the degrading species of Biofilter Mixture of hydrophilic and hydrophobic VOCs 90-95 Presence of hydrophilic compound, suppressed the growth of hydrophobic degrading microbial community, thereby reducing the removal of hydrophobic compound [26] Biotrickiling filter VOCs 60 Increase in EBCT is needed to degrade the hydrophobic VOCs, which increases the performance of a reactor [27] Bioscrubber Mixture of VOCs 80-85 Doubling of inlet load involved a decrease in the removal efficiency of the VOC [28] Membrane bioreactor ...
... Biofilter as a cost-effective reactor for degradation of poorly soluble VOCs is not appropriate for treatment of high concentrations of acid-producing pollutants such as DCM. On the other hand, bubble column bioreactor is not sensitive to high concentrations of acid-producing pollutants [11][12][13][14]. Therefore in this study, in order to benefit from advantages of both biofilter and bubble column bioreactor, a hybrid bubble column/biofilter (HBCB) bioreactor was developed and operated in continuous mode for several months to optimize removal of DCM from waste gas streams. ...
Background and objectives: Dichloromethane (DCM) is one of the hazardous contaminants of the environment, especially ambient air that threatens human health at both acute and chronic exposures. In this study, the performance of a pilot-scale hybrid bubble column/biofilter (HBCB) bioreactor was studied for the removal of DCM from waste gas streams at steady state.
Materials and methods: The experiments were conducted in four stages with relatively constant concentrations of DCM (approximately 240 ppm) and variable empty bed residence time (EBRT) of 50, 100, 150 and 200 s. In addition to determining DCM removal rate and efficiency, quality parameters of mixed liquor of the bubble column bioreactor were studied and kinetic of biofiltration was analyzed.
Results: The average DCM removal efficiency of the HBCB bioreactor at EBRT of 200 and 150 s were 79 and 71% respectively. However, further reduction of EBRT resulted in significantly decreased DCM removal efficiency, so that at EBRT of 50 s, the DCM removal efficiency decreased to 32%. In addition, the EBRT reduction from 200 s to 50 s through increasing DCM loading rate resulted in increasing DCM removal rate from 12.1 to 19.6 g/m3.h. The results of kinetic analysis showed that the kinetic data of biofiltration were in the best fitness with the first order rate equation (R2>0.99 and ε%
... Several studies have evaluated the contribution of surface coating facilities to regional emission inventories891011. In addition, a number of studies have examined methods of reducing emissions from surface coating fa- cilities [6,121314151617. Wadden et al. (1995) estimated VOC emissions for a sheetfed offset printing facility [18]. ...
Surface coating facilities are major sources of volatile organic compounds (VOCs) in urban areas. These VOCs can contribute to ground-level ozone formation, and many are hazardous air pollutants (HAPs), including xylene, ethylbenzene, and toluene. This project was conducted in order to provide information for updating the Texas Commission on Environmental Quality (TCEQ), USA, permit by rule for Surface Coating Facilities. Project objectives were: 1) To develop a database of information regarding surface coating facilities in Texas; 2) To estimate maximum emission rates for various VOC species from surface coating facilities in Texas; 3) To conduct dispersion modeling to estimate off-site
impacts from surface coating facilities. The database was developed using 286 TCEQ permit files authorizing surface
coating facilities in Texas during 2006 and 2007. The database was designed to include information important for esti-
mating emission rates, and for using as inputs to the dispersion model. Hourly and annual emissions of volatile organic
compounds (VOCs), particulate matter (PM), and exempt solvents (ES) were calculated for each permitted entity/
company in the database, according to equations given by TCEQ. Dispersion modeling was then conducted for 3 facil-
ity configurations (worst-case stack height, good practice stack height, and fugitive emissions), for urban and rural dis-
persion parameters, for 8-hour and 24-hour operating scenarios, and for 1-hour, 24-hour, and annual averaging times,
for a total of 36 scenarios. The highest modeled concentrations were for the worst-case stack height, rural dispersion parameters, 24-hour operation scenario, and 1-hour averaging time. 108 specific chemical species, which are components of surface coatings, were identified as candidates for further health impacts review.
Biotrickling filters (BTFs) for volatile organic compounds (VOCs) have attracted tremendous research attention in the field of environmental engineering. However, the problem of clogging occurred during the long-term operation limits their practical applications. To alleviate the clogging, an integral polypropylene (PP) packing coated with polydimethylsiloxane (PDMS) was prepared, and in combination with fungus, its performance was investigated for toluene elimination. Two laboratory-scale BTFs were started at low toluene concentrations of 200–900 mg∙m⁻³. Subsequently, a series of experiments were conducted at toluene concentrations of 47–2906 mg∙m⁻³, with empty bed residence time (EBRT) values of 50 and 40 s. Toluene removal efficiency reached 100% at the inlet toluene concentration of 296–560 mg∙m⁻³ for EBRT of 50 s. The maximum elimination capacity (EC) of 98 g∙m−3∙h⁻¹ was obtained at an inlet toluene load of 117.67 g∙m−3∙h⁻¹. Clogging was relieved by manual cleanup, and the BTFs were operated steadily for nearly 8 months. CO2 production was monitored during the whole operation, and toluene mineralization was evaluated simultaneously. Furthermore, the biofilm structure and microbial diversity were analyzed.
Air pollution is a topic of important global concern because it has contributed significantly to an increase in the earth's global warming potential and contributed to severe health and environmental impacts. In this review, the different bioreactor configurations commonly used for waste gas treatment, namely the biofilters, the biotrickling filters and the bioscrubbers, and their industrial applications were compared in terms of the type of inoculum, the packing material/media, removal efficiency and elimination capacity. Typically, biofilters are operated under the following range of operating conditions: gas residence time = 15–60 s; gas flow rate = 50–300,000 m³ h⁻¹; temperature = 15–30 °C; pH = 6.0–7.5; filter area = 100–3000 m²; relative humidity >95.0%; and removal efficiencies >75.0% depending on the waste gas composition and concentration. The biotechnological approaches for resource recovery, i.e., the conversion of C1 gaseous compounds (CO, CO2 and CH4) to liquified value-added products or biofuels have been discussed. From this review, it was evident that the performances of different aerobic, anoxic and/or anaerobic lab, pilot and full-scale bioreactors for waste gas treatment and resource recovery depend on the composition, the individual concentration of pollutants present in the waste gas and the gas flow rate. Although most of the research on product recovery from waste gas is rather limited to lab/pilot-scale studies, there are some key commercialized technologies that have proven to be economical at the full-scale. Thus, this review, comprehensively presents a complete overview of the current trends and limitations of conventional waste gas treatment systems, the benefits of novel bioreactor configurations and their potential to be applied for resource recovery from waste gases.
Changes in the microbial community can not only reflect the efficiency of waste disposal, but also reveal the effect of odor control during the treatment process. This study aimed to evaluate the removal efficiency of volatile organic compounds (VOCs) by the process of mechanical and biological pretreatment (MBP) coupled with a bio-filter (BF). An interesting phenomenon was found that the VOCs were effectively reduced through the MBP process. To understand the removal mechanism of VOCs, the abundance and diversity of microbial bacteria and fungi in the biological dehydration (BD) process, biological fermentation process, and BF process were explored. The abundance and diversity of microbes in the BF were relatively high, of which the bacteria such as Lactobacillus, Bacillus and Candida were the dominant species for VOCs treatment. The proposed technical process and the positive effects observed in this study indicate that it could be applied to the control of VOCs in the treatment of domestic waste.
The automotive painting industry is a source of environmental pollution caused by Volatile Organic Compounds (VOCs) present in the discharged ventilation air. To contribute to the mitigation of this type of air pollution, Ekoinwentyka Ltd. developed – from pilot scale to full scale – and adapted the technology of Compact Trickle Bed Bioreactor (CTBB) whose operating principle builds upon co-current downflow of the gas phase (polluted air) and liquid phase (solution of mineral salts) through a packed bed where active microorganisms are immobilized in the biofilm on the surfaces of packing elements. Pilot-scale bioreactor 0.32 m in diameter and 1.50 m total height had its packed bed inoculated with a consortium of microorganisms dominated by Pseudomonas fluorescens bacteria. During the experimental programme that lasted several months, the flow rate of air drawn from the ventilation system of the painting shop was changing between 1.0 and 10.0 m³/h and the inlet concentration of VOCs ranged from 10 to 200 ppm. By measuring VOC concentration in the purified air, the factor of VOC biodegradation was found to range between 85 and 99%. Based on pilot-scale experiments, full-scale CTBB has been developed 2.8 m in diameter and 10 m total height and installed as an add-on component of the ventilation system of the painting shop. Test operation at gas flow rates up to 6000 m³/h, confirmed VOC biodegradation factor at the level of 85–99% thus proving a positive result of CTBB technology adaptation to the conditions of the automotive painting industry.
The performance of lab- and pilot-scale bio-trickling filters (BTFs) for the treatment of emissions from a chemical fibre wastewater treatment plant was investigated. These systems were installed mainly to demonstrate the effectiveness of bio-trickling technologies in purifying exhaust gases containing different kinds of volatile organic compounds (VOCs). Results showed that 12 days more were necessary for the pilot-scale BTF to start up successfully than the lab-scale one. Both the lab- and pilot-scale BTFs exhibited contaminant removal efficiency higher than 90% at an empty bed residence time of 59 s, corresponding to gas flow of 0.2 m3 h-1 and 550 m3 h-1, respectively. The reduction of the microelement in the nutrient solution had little effect on the performance of the pilot-scale BTF. The abundance and diversity of the microorganism analysis showed that the diversity of the contaminants had a significant influence on the microorganism distribution in the BTF. Economic feasibility study showed that BTF might be an efficient solution for VOCs control with a lower cost than adsorption technology and regenerative catalytic oxidation.
Volatile organic compounds (VOCs) present in crude oil can be released to the atmosphere from storage tanks, wastewaters and equipment leaks in petroleum industries. A pilot-scale sequential biotrickling-biofiltration (BTF-BF) unit as an environmentally safe and economical treatment procedure was designed and tested for removal of VOCs from a wastewater sump at the CITGO Corpus Christi Refinery. To identify and quantify VOC emissions from the refinery wastewater sump, the air was sampled using 6 L canisters and characterized using gas chromatography-mass spectrometry. The pilot-scale unit included a BTF for removal of more water soluble compounds followed by a BF for removal of poorly soluble compounds. Performance of the BTF and BF units containing plastic cross flow and compost-based media were investigated at pollutant loading rates of 6 g/m3hr to 1750 g/m3hr.
The characterization results of the pilot test showed benzene as the main constituent of the vapor stream (85% of vapor) emitted from the wastewater sump. The ratio of benzene to toluene and xylene was determined to be 12:2:1 in these samples. The high concentration of benzene as an amenable food and energy source for the microorganisms lead to high biomass growth and more than 85% removal efficiency (RE) for total emitted VOCs.
Application of an innovative sequential biotrickling-biofiltration unit was also demonstrated to effectively handle the cyclic emissions of VOCs at most oil and gas industries. Although several researches have been done to evaluate the performance of BFs and/or BTFs in the laboratory, this pilot study can be used to design and optimize the performance of a bio-oxidation unit under actual refinery operating conditions.
Biological based emissions control has been demonstrated to be an efficient and cost effective alternative to thermal oxidation technology or flaring for volatile organic compounds (VOCs) from the forest products and paint and coatings industries. This type of technology applicationhas promising advantages such as the potential for a low carbon footprint, low secondary pollutants such as NOx and SOx, lower energy demands, and lower cost. The objective of this project was to design and implement a sequential field scale biotrickling-biofilter treatment unit to remove VOCs and hazardous air pollutants (HAPs) emissions at the Apache TAMU#2 well storage tank battery in Snook, Texas.
The field scale biotreatment system included a biotrickling filter followed by a biofilter with the total treatment volume of 100 ft3, skid mounted on a 22 foot trailer. The biotrickling filter was packed with structured cross flow media with large surface area and high void fraction designed to remove the more water soluble compounds and control the humidity and temperature variations of the inlet gas stream. The biofilter unit was loaded with plastic spheres packed with compost which is referred to as the engineered media. Each of the bio-oxidation units was operated at the air flow rate of 25 CFM and empty bed residence time (EBRT) of 2 minutes. The system was inoculated with local stormwater and wastewater from a sedimentation basinclarifier of a local refinery to provide a mixed culture of microorganisms for degradation of the VOC emissions.
VOC emissions were collected from the headspace of a storage tank battery leading into a pressure relief vent system. Based on the photo ionization detector (PID) measurements at the inlet of the bio-oxidation unit, the VOC concentration loadings was cyclic and appeared to be correlated to the gas lift cycle of liquid loading to the crude oil storage tank.
During the evaluation period, the biotrickling unit demonstrated a surprisingly higher removal efficiency compared to the biofilter. This may be related to the more stable and higher density of biomass growth observed on the surface of the cross flow media. The lower removal efficiency in the biofilter unit could be due to the lack of uniform moisture and nutrients in the second vessel as a result of spray nozzle inefficiency. This aspect of operation can be further optimized by changing the nozzle and the frequency of watering/spraying of the compost media. A removal efficiency of 50-60% for the total VOCs, across the complete unit, was achieved during the 3 month evaluation period while the unit was operated at an average inlet VOC concentration of 400 ppm.
The relatively high concentration of alkenes and alkanes (compared to aromatics and water soluble organics in this crude oil vapor), may have decreased the degradation of the total VOCs in the bio-oxidation unit because these long-chain compounds are more difficult to biodegrade by bacterial biofilms in an aerobic environment.
The results suggest biological emission treatment systems may be cost effective when compared to thermal oxidizers and flares and should be evaluated as a Maximum Achievable Control Technology (MACT) to mitigate HAPs (and VOCs) from some oil and gas operations.
This innovative biological emissions control technology effectively controlled the cyclic emissions produced at the remote site. The strong increase in removal of VOCs after the oil refinery wastewater inoculation suggests an important optimization parameter for more rapid acclimation and increased efficiency for the system in the future applications.
Two pilot-scale bio-trickling filters (BTFs) with counter-current and cross-current flow modes were constructed, and their performance tested, for purifying chemical fibre waste gas containing H2S, NH3 and VOCs with a maximum gas flow rate of 1008 m³ h⁻¹. The counter-current type of BTF presented with superior biodegradation results compared to the cross-current type: it could start up quickly, tolerated high transient shock loadings, and possessed an average contaminant removal efficiency higher than 90% with an empty bed residence time of 59 s. The contaminant removal efficiency could be increased by 50% during winter due to the addition of pipeline insulation. The abundance and diversity from microorganism analysis showed that Dyella, Bacillus, Candidimonas, Pandoraea and Thiomonas were the main bacterial strains forming the community treating the pollutants. The counter-current type BTF functioned most effectively and is proposed for practical application.
The performance and feasibility of a pilot unit of biotrickling filter (BTF) for the treatment of industrial emissions polluted by styrene was investigated for one year at a fiber reinforced plastic industrial site. The pilot unit was packed with a structured material with a volume of 0.6 m³. Monitoring results have shown successful treatment of the industrial styrene emissions working at empty bed residence times (EBRT) between 31 and 66 s. The best performance was obtained after 300 days when a more stable biofilm had been developed, obtaining the highest elimination capacity of 18.8 g m⁻³ h⁻¹ (removal efficiency of 75.6%) working at 31 s of EBRT. In addition, a photocatalytic reactor was evaluated as pretreatment of the biological process, but results have shown very low capacity for improving the BTF performance due to catalyst deactivation. The economic feasibility of the BTF was evaluated. The total direct cost, excluding capital recovery, of the biotrickling filter technology was estimated in 0.71 € year⁻¹ per Nm³ h⁻¹ of treated air whereas 2.27 € year⁻¹ per Nm³ h⁻¹ was obtained for the regenerative catalytic oxidizer equipped with a zeolite pre-concentrator. Results show that this technology is economically and environmentally competitive in comparison with thermal treatment.
Biofiltration has been widely applied to remove odours and volatile organic compounds (VOCs) from industrial off-gas and mechanical-biological waste treatments. However, conventional open biofilters cannot guarantee an efficient dispersion of air pollutants emitted into the atmosphere. The aim of this paper is to compare conventional open biofilters with biotrickling filters (BTFs) in terms of VOC dispersion in the atmosphere and air quality in the vicinity of a hypothetical municipal solid waste bio-drying plant. Simulations of dispersion were carried out regarding two VOCs of interest due to their impact in terms of odours and cancer risk: dimethyl disulphide and benzene, respectively. The use of BTFs, instead of conventional biofilters, led to significant improvements in the odour impact and the cancer risk: when adopting BTFs instead of an open biofilter, the area with an odour concentration > 1 OU m(-3) and a cancer risk > 10(-6) was reduced by 91.6% and 95.2%, respectively. When replacing the biofilter with BTFs, the annual mean concentrations of odorants and benzene decreased by more than 90% in the vicinity of the plant. These improvements are achieved above all because of the higher release height of BTFs and the higher velocity of the outgoing air flow.
EU environmental policy makes controlling the emissions of Volatile Organic Compounds (VOC) in waste gases necessary. Biotrickling filtration, an emergent biotreament, could be a viable technology for the coating sector. In this study, field-scale applications in two different industrial sectors are presented. A full-scale biotrickling system, including an activated carbon-smoothing prefilter, was installed at a furniture facility. Two spray booths were tested. n-Butyl acetate (20–50%) and xylenes (10–30%) were identified as the main solvents of one of the booths, while acetone (85–100%) was the main VOC coming from the other source. Due to the uneven emission pattern, the activated carbon prefilter allowed the VOC fluctuations to be buffered, increasing significantly the removal efficiency (10–20%). The second case consisted of a pilot-scale biotrickling filter tested in a plastic coating facility of the auxiliary automotive sector. In this case, emissions were quite stable, although VOC composition depends on the paint formulation used in the two robotic spray booths connected to the bioreactor. Some paints contained n-butyl acetate, butyl glycol acetate and methyl acetate in a proportion greater than 70% with a small proportion of aromatics (xylenes and ethylbenzene), while other products were mainly composed of naphtha, heavy aromatic fraction (75–100%). The systems were able to comply with legal emission limits under suitable operational conditions; with Empty Bed Residence Time (EBRT) ranging from 20 to 85 s depending on the waste gas source. The composition and pattern emissions were shown to be the crucial parameters determining the performance of the systems. Economic evaluation, including amortization and operational cost, showed a total cost of around 1.5 and 5.0 ε per year per Nm3 h-1 of air to be treated depending on the source.
BACKGROUND: Biotrickling filtration could be considered as a suitable and viable technology for controlling the industrial emissions of volatile organic compounds (VOCs) in waste gases. In this study, the performance of a full-scale biotrickling system, including a passively activated carbon-smoothing prefilter was investigated for the treatment of exhaust gases from two different paint spray sources at a furniture facility.
RESULTS: The VOC profiles were uneven for both sources, but the second source was more irregular, with highly variable VOC loads. The plant was operated at empty bed residence times (EBRTs) between 20 and 100 s. The system was able to control the VOC emissions, so air treated could comply with local legal emission limits under suitable operating conditions (EBRT ∼20 s and EBRT ∼85 s for the first and the second source, respectively). Economic evaluation of the treatment, including investment amortization, showed a total cost per 10,000 m3 of treated air of around 8 € and 35 € for the first and the second sources, respectively.
CONCLUSION: The profile, type, and composition of VOC sources were shown to be crucial parameters determining the VOC removal ability and the viability of the biotrickling system. Copyright
Emission characteristics of volatile organic compounds (VOCs) were investigated in an automotive coating manufacturing enterprise. Air samples were taken from eight different manufacturing areas in three workshops, and the species of VOCs and their concentrations were measured by gas chromatography-mass spectrometry (GC-MS). Safety evaluation was also conducted by comparing the concentration of VOCs with the permissible concentration-short term exposure limit (PC-STEL) regulated by the Ministry of Health. The results showed that fifteen VOCs were detected in the indoor air of the automotive coatings workshop, including benzene, toluene, ethylbenzene, xylene, ethyl acetate, butyl acetate, methyl isobutyl ketone, propylene glycol monomethyl ether acetate, trimethylbenzene and ethylene glycol monobutyl ether, Their concentrations widely ranged from 0.51 to 593.14 mg x m(-3). The concentrations of TVOCs were significantly different among different manufacturing processes. Even in the same manufacturing process, the concentrations of each component measured at different times were also greatly different. The predominant VOCs of indoor air in the workshop were identified to be ethylbenzene and butyl acetate. The concentrations of most VOCs exceeded the occupational exposure limits, so the corresponding control measures should be taken to protect the health of the workers.
The evolution of the microbial community was analysed over one year in two biotrickling filters operating under intermittent feeding conditions and treating isopropanol emissions, a pollutant typically found in the flexography sector. Each reactor was packed with one media: plastic cross-flow-structured material or polypropylene rings. The communities were monitored by fluorescence in situ hybridization (FISH) and denaturing gradient gel electrophoresis (DGGE) analysis of the 16S rRNA region. After inoculation with activated sludge, the biotrickling filters were operated using inlet loads (ILs) from 20 to 65 g C m(-3) h(-1) and empty-bed residence times (EBRTs) from 14 to 160 s. Removal efficiencies higher than 80% were obtained with ILs up to 35 g C m(-3) h(-1) working at EBRTs as low as 24 s. There was an increase in the total percentage of the target domains of up to around 80% at the end of the experiment. Specifically, the Gammaproteobacteria domain group, which includes the well-known volatile organic compound (VOC)-degrading species such as Pseudomonas putida, showed a noticeable rise in the two biotrickling filters of 26% and 27%, respectively. DGGE pattern band analysis revealed a stable band of Pseudomonas putida in all the samples monitored, even in the lower diversity communities. In addition, at similar operational conditions, the biotrickling filter with a greater relative abundance of Pseudomonas sp. (19.2% vs. 8%) showed higher removal efficiency (90% vs. 79%). Results indicate the importance of undertaking a further in-depth study of the involved species in the biofiltration process and their specific function.
A 0.75-m3 pilot-scale biotrickling filter was run for over 1 yr in a Spanish furniture company to evaluate its performance in the removal of volatile organic compounds (VOCs) contained in the emission of two different paint spray booths. The first one was an open front booth used to manually paint furniture, and the second focus was an automatically operated closed booth operated to paint pieces of furniture. In both cases, the VOC emissions were very irregular, with rapid and extreme fluctuations. The pilot plant was operated at an empty bed residence time (EBRT) ranging from 10 to 40 sec, and good removal efficiencies of VOCs were usually obtained. When a buffering activated carbon prefilter was installed, the system performance was improved considerably, so a much better compliance with legal constraints was reached. After different shutdowns in the factory, the period to recover the previous performance of the biotrickling reactor was minimal. A weekend dehydration strategy was developed and implemented to control the pressure drop associated with excessive biomass accumulation.
The frequent discrepancy between direct microscopic counts and numbers of culturable bacteria from environmental samples is just one of several indications that we currently know only a minor part of the diversity of microorganisms in nature. A combination of direct retrieval of rRNA sequences and whole-cell oligonucleotide probing can be used to detect specific rRNA sequences of uncultured bacteria in natural samples and to microscopically identify individual cells. Studies have been performed with microbial assemblages of various complexities ranging from simple two-component bacterial endosymbiotic associations to multispecies enrichments containing magnetotactic bacteria to highly complex marine and soil communities. Phylogenetic analysis of the retrieved rRNA sequence of an uncultured microorganism reveals its closest culturable relatives and may, together with information on the physicochemical conditions of its natural habitat, facilitate more directed cultivation attempts. For the analysis of complex communities such as multispecies biofilms and activated-sludge flocs, a different approach has proven advantageous. Sets of probes specific to different taxonomic levels are applied consecutively beginning with the more general and ending with the more specific (a hierarchical top-to-bottom approach), thereby generating increasingly precise information on the structure of the community. Not only do rRNA-targeted whole-cell hybridizations yield data on cell morphology, specific cell counts, and in situ distributions of defined phylogenetic groups, but also the strength of the hybridization signal reflects the cellular rRNA content of individual cells. From the signal strength conferred by a specific probe, in situ growth rates and activities of individual cells might be estimated for known species. In many ecosystems, low cellular rRNA content and/or limited cell permeability, combined with background fluorescence, hinders in situ identification of autochthonous populations. Approaches to circumvent these problems are discussed in detail.
Domain-, class-, and subclass-specific rRNA-targeted probes were applied to investigate the microbial communities of three industrial and three laboratory-scale biofilters. The set of probes also included a new probe (named XAN818) specific for the Xanthomonas branch of the class Proteobacteria; this probe is described in this study. The members of the Xanthomonas branch do not hybridize with previously developed rRNA-targeted oligonucleotide probes for the alpha-, beta-, and gamma-Proteobacteria. Bacteria of the Xanthomonas branch accounted for up to 4.5% of total direct counts obtained with 4',6-diamidino-2-phenylindole. In biofilter samples, the relative abundance of these bacteria was similar to that of the gamma-Proteobacteria. Actinobacteria (gram-positive bacteria with a high G+C DNA content) and alpha-Proteobacteria were the most dominant groups. Detection rates obtained with probe EUB338 varied between about 40 and 70%. For samples with high contents of gram-positive bacteria, these percentages were substantially improved when the calculations were corrected for the reduced permeability of gram-positive bacteria when formaldehyde was used as a fixative. The set of applied bacterial class- and subclass-specific probes yielded, on average, 58.5% (+/- a standard deviation of 23.0%) of the corrected eubacterial detection rates, thus indicating the necessity of additional probes for studies of biofilter communities. The Xanthomonas-specific probe presented here may serve as an efficient tool for identifying potential phytopathogens. In situ hybridization proved to be a practical tool for microbiological studies of biofiltration systems.
Air artificially contaminated with increasing concentrations of benzene was treated in a laboratory scale compost-packed biofilter for 240 days with a removal efficiency of 81-100%. The bacterial community in the packing material (PM) at different heights of the biofilter was analysed every 60 days. Bacterial plate counts and ribosomal intergenic spacer analysis (RISA) of the isolated strains showed that the number of cultivable aerobic heterotrophic bacteria and the species diversity increased with benzene availability. Identification of the isolated species and the main bands in denaturing gradient gel electrophoresis (DGGE) profiles from total compost DNA during the treatment revealed that, at a relatively low volumetric benzene load (1.2< or =VBL< or =6.4 g m(-3) (PM) h(-1)), besides low G+C Gram positive bacteria, originally present in the packing compost, bacteroidetes and beta- and gamma-proteobacteria became detectable in the colonising population. At the VBL value (24.8 g m(-3) (PM) h(-1)) ensuring the maximum elimination capacity of the biofilter (20.1 g m(-3) (PM) h(-1)), strains affiliated to the genus Rhodococcus dominated the microflora, followed by beta-proteobacteria comprising the genera Bordetella and Neisseria. Under these conditions, more than 35% of the isolated strains were able to grow on benzene as the sole carbon source. Comparison of DGGE and automated RISA profiles of the total community and isolated strains showed that a complex bacterial succession occurred in the reactor in response to the increasing concentrations of the pollutant and that cultivable bacteria played a major role in benzene degradation under the adopted conditions.
probeBase is a curated database of annotated rRNA-targeted oligonucleotide probes and supporting information. Rapid access
to probe, microarray and reference data is achieved by powerful search tools and via different lists that are based on selected
categories such as functional or taxonomic properties of the target organism(s) or the hybridization format (fluorescence
in situ hybridization or microarray) in which the probes were applied. Additional information on probe coverage and specificity is
available through direct submissions of probe sequences from probeBase to RDP-II and Greengenes, two major rRNA sequence databases.
A freely editable user comments field for each probe entry allows any user to add, modify or remove information or to report
errors in real-time. probeBase entries increased from 700 to more than 1200 during the past three years. Several options for
submission of single probes or entire probe sets, even prior to publication of newly developed probes, should further contribute
to keeping probeBase an up-to-date and useful resource. probeBase is freely accessible at http://www.microbial-ecology.net/probebase. Email correspondence can be addressed to probebase{at}microbial-ecology.net.
Biological processes, most notably biofilters and biotrickling filters, are increasingly used to remove and biodegrade a wide variety of volatile organic compounds (VOCs) present in gas streams emitted from industrial operations. In the research described herein, a laboratory-scale biofilter was operated for a period of more than 180 days to treat a waste gas comprised of a four-component VOC mixture representative of solvents present in off-gases emitted by painting operations. The biofilter, packed with a cubed polyurethane foam media and initially inoculated with a pure culture of the fungus Cladosporium sphaerospermum, was maintained under acidic conditions throughout the duration of the experiments. The system was supplied with a mixture of n-butyl acetate, methyl ethyl ketone, methyl propyl ketone, and toluene with influent concentrations of 124, 50.5, 174, and 44.6 mgm−3 , respectively. The biofilter’s empty bed residence time (EBRT) was varied from 2.0 min to 15 s. When the influent gas stream was properly humidified, the system exhibited stable long-term performance with an average total VOC removal greater than 98% even with an EBRT as low as 15 s. Under the loading condition tested, this corresponds to an average elimination capacity of 92 gm−3h−1 . VOC concentration profiles measured along the height of the biofilter revealed a distinct VOC degradation pattern that was observed under all loading conditions tested. Although the column was initially inoculated with only Cladosporium sphaerospermum, several additional species of fungi tentatively identified as Penicillium brevicompactum, Exophiala jenselmei, Fusarium oxysporum, Fusarium nygamai, Talaromyces flavus, and Fonsecaea pedrosi were found growing attached to the packing medium by the end of experiment. Results demonstrate that fungal biofilters can consistently maintain high removal efficiency for paint VOC mixtures over extended periods of operation. The results also indicate that it would be difficult and likely unnecessary to maintain specific species in full-scale fungal biofilters treating paint spray booth emissions.
Interactions amongst the degradation rates of toluene, xylenes, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and n-butyl acetate (n-BA) were investigated. Experiments were performed in a biotrickling filter reactor packed with polypropylene Pall rings in a counter-current air–water mode of operation. Under pseudo-steady-state conditions, the removal efficiency (RE) of the individual components in the middle of and at the effluent above the reactor bed was evaluated. By using a mixed microbial culture as the biocatalyst, the results revealed that an increased loading of toluene and xylene had a competitive effect on the RE of MIBK. After reaching a saturation point of the overall catabolic capacity of the biocatalyst, variations of RE were observed for the different components. This was most pronounced under conditions of overloading with the water-soluble components mixture. Despite such variations, the system was able to efficiently degrade this complex pollutant mixture for a period of 1 yr. © 2006 American Institute of Chemical Engineers Environ Prog, 2006
BACKGROUND: Fluorescence in situ hybridization (FISH) together with confocal laser scanning microscopy (CLSM) is widely used for the analysis and quantification of biomass fractions of activated sludge or biofilm systems in wastewater treatment research. Unlike the FISH technique, the CLSM image analysis and quantification is not generally unique and thus, several manual and automated methods exist that can lead to very different results.
RESULTS: A method based on the analysis of negative control images is reported in this paper. Histograms of negative control images were used in the segmentation of positive images (hybridized with FISH probes). The threshold ( I th r ) was defined as the minimum intensity value that satisfies the following condition: the proportion of pixels with intensity I ≤ I th r in the negative control images is greater than or equal to a value α. It was found that the optimal α–value was 99.90% for the specific case studied (nitrifying activated sludge samples) by comparing the automatic thresholding with manual thresholding by three expert operators.
CONCLUSION: The method developed was useful for following systematically the evolution of ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) fractions in a nitrifying system under changing operating conditions. Copyright © 2009 Society of Chemical Industry
This study presents a comparison of the efficiency of a bioscrubber and a biotrickling filter (BTF) for the removal of ethyl acetate (EA) vapour from a waste gas stream, under the same operating conditions. The maximum EA elimination capacity achieved in the bioscrubber was 550 g m−3 h−1 with removal efficiency higher than 96%. For higher EA loadings the bioscrubber was oxygen limited, which caused incomplete EA biodegradation. When pure oxygen was fed to the bioscrubber at a rate of 0.02 L min−1, the bioscrubber recovered and could treat higher EA loadings without any oxygen limitation. The BTF achieved EA elimination capacity of 600 g m−3 h−1 with removal efficiency higher than 97% and the dissolved oxygen concentration remained substantially higher than in the bioscrubber. However, severe channelling and blockage of the spray nozzle occurred due to the excessive biomass growth. Overall, the bioscrubber system was easier to operate and control than the BTF, while an enhancement of the oxygen mass transfer in the bioscrubber could potentially increase its performance by up to three times. Copyright © 2005 Society of Chemical Industry
The robustness of a conventional biofilter and an air diffusion bioreactor (ADB) was comparatively evaluated in laboratory-scale plants treating a mixture of H2S, butanone, toluene and alpha-pinene at gas residence times of 50 s. Under steady state conditions, H2S, butanone and toluene were almost completely degraded, while alpha-pinene removal did not exhibit removal efficiencies (REs) higher than 11.0 +/- 2.3%. Fluctuations in temperature from 8 degrees C to 30 degrees C did not impact significantly process performance in any of the biotechnologies tested. However, while the ADB unit was able to cope with three and six fold step increases in pollutant loadings, volatile organic compounds (VOCs) REs noticeably decreased in the biofilter when subjected to a six fold step change (i.e. 90% reduction for butanone and 30% for toluene). A process shutdown of five days resulted in the temporary loss of butanone and toluene RE in the ADB system. A lack of irrigation during five days caused a slight decrease in the biofilter REs, while a failure in the pH control system drastically affected the ADB performance. Finally, process robustness was quantified. The calculated overall risks showed that both biotechnologies were reliable for H2S and VOCs treatment in wastewater treatment plants, ADB diffusion exhibiting a higher robustness towards fluctuations commonly found under routine operation. This robustness was further confirmed by the high stability of the DGGE profiles.
The bacterial composition of a lab-scale biotrickling filter (BTF) treating high loads of H(2)S was investigated by the rRNA approach. Two 16S rRNA gene clone libraries were established 42 and 189 d after reactor startup, while fluorescent in-situ hybridization (FISH) with DNA probes was performed throughout 260d of reactor operation. Diversity, community structure and metamorphosis were studied from reactor startup to fully-established pseudo-steady state operation at near neutral pH and at an inlet H(2)S concentration of 2000 ppmv (load of 55.6g H(2)S m(-3)h(-1)). In addition, FISH was used for assessing the spatial distribution of sulfur-oxidizing bacteria (SOB) along the length of the reactor under pseudo-steady state operation. A major shift in the diversity of the community was observed with the operating time, from a well-diverse community at startup to pseudo-steady state operation with a majority of retrieved sequences affiliated to SOB of the sulfur cycle including Thiothrix spp., Thiobacillus spp., and Sulfurimonas denitrificans. Although aerobic species were predominant along the BTF, a vertical stratification was encountered, in which facultative anaerobes had a major relative abundance in the inlet part of the BTF, where the sulfide to oxygen ratio was higher. The observed changes were related to the trophic properties of the community, the DO concentration, the accumulation of elemental sulfur and the operation at neutral pH.
A biofilter treating alkylbenzene vapors was characterized for its optimal running conditions and kinetic parame-ters. Kinetics of the continuous biofilter were compared to batch kinetic data obtained with biofilm samples as well as with defined microbial consortia and with pure culture isolates from the biofilter. Both bacteria and fungi were present in the bioreactor. Five strains were isolated. Two bacteria, Bacillus and Pseudomonas, were shown to be dominant, as well as a Trichosporon strain which could, however, hardly grow on alkylbenzenes in pure culture. The remaining two strains were most often overgrown by the other three organisms in liquid phase batch cultures μ
max, KS, KI values and biodegradation rates were calculated and compared for the difterent mixed and pure cultures. Since filter bed acidification was observed during biofiltration studies reaching a pH of about 4, experiments were also undertaken to study the influence of pH on performance of the different cultures. Biodegradation and growth were possible in all cases, over the pH range 3.5–7.0 at appreciable rates, both with mixed cultures and with pure bacterial cultures. Under certain conditions, microbial activity was even observed in the presence of alkylbenzenes down to pH 2.5 with mixed cultures, which is quite unusual and explains the ability of the present biocatalyst to remove alkylbenzenes with high efficiency in biofilters under acidic conditions.
A study was conducted to investigate the microbial community structure, the physicochemical properties, and the relationships between these parameters of a full-scale industrial biofilter used for waste gas abatement in an animal-rendering plant. Fluorescence in situ hybridization (FISH) was successfully combined with digital image analysis to study the composition of the microbial community. Several new nucleic acid probes were designed and established based on published 16S rDNA sequences and on ones retrieved from the biomass of the biofilter under investigation. Bacterial detection rates varied greatly over time and filterbed depth between 27.2% and 88.1% relative to DAPI counts. Overall, members of the Betaproteobacteria followed by Actinobacteria, Alphaproteobacteria, Cytophaga-Flavobacteria, Firmicutes and Gammaproteobacteria were the most abundant groups. Among the groups below phylum level, members of the Alcaligenes/Bordetella lineage were on average the most abundant group accounting for up to 8.5% of DAPI-stained cells. Whereas the community composition generally showed no vertical gradient, the lower 50 cm of the biofilter proved to be the most active part for the degradation of aldehydes such as 2- and 3-methylbutanal, 2-methylpropanal, and hexanal. This zone of the filterbed being operated in up-flow direction degraded about 80% of these compounds. Dimethyldisulphide was the most common reduced sulphur compound. Statistical analysis of microbial versus waste gas parameters generally revealed only weak or non-significant correlations between the two. Possible explanations for this finding are discussed.
To investigate the relationships between the operation of the volatile organic compound (VOC) removal biofilter and the structure of microbial communities, and to study the impact on degradation activities and the structuring of microbial communities of biofilter malfunctions related to the qualitative composition of the polluted air.
A microbiological study and a measurement of biodegradation activities were simultaneously carried out on two identical peat-packed columns, seeded with two different inocula, treating polluted air containing 11 VOCs. For both reactors, the spatial structure of the microbial communities was investigated by means of single-strand conformation polymorphism (SSCP) analysis. For both reactors, stratification of degradation activities in function of depth was observed. Oxygenated compounds were removed at the top of the column and aromatics at the bottom. Comparison of SSCP patterns clearly showed a shift in community structure in function of depth inside both biofilters. This distribution of biodegradation activities correlates with the spatialization of microbial density and diversity. Although the operating conditions of both reactors were identical and the biodegradation activities similar, the composition of microflora differed for biofilters A and B. Subdivision of biofilter B into two independent parts supplied with polluted air containing the complex VOC mixture showed that the microflora having colonized the bottom of biofilter B retained their potential for degrading oxygenated compounds.
This work highlights the spatialization of biodegradation functions in a biofilter treating a complex mixture of VOCs. This distribution of biodegradation activities correlates with the spatialization of microbial density and diversity.
This vertical structure of microbial communities must be taken into consideration when dealing with the malfunctioning of bioreactors. These results are also useful information about changes in microbial communities following natural or anthropogenic alterations in different ecosystems (soils and sediments) where structuring of microbial communities according to depth has been observed.
Two biofilters were operated to treat a waste gas stream intended to simulate off-gases generated during the manufacture of reformulated paint. The model waste gas stream consisted of a five-component solvent mixture containing acetone (450 ppm(v)), methyl ethyl ketone (12 ppm(v)), toluene (29 ppm(v)), ethylbenzene (10 ppm(v)), and p-xylene (10 ppm(v)). The two biofilters, identical in construction and packed with a polyurethane foam support medium, were inoculated with an enrichment culture derived from compost and then subjected to different loading conditions during the startup phase of operation. One biofilter was subjected to intermittent loading conditions with contaminants supplied only 8 hr/day to simulate loading conditions expected at facilities where manufacturing operations are discontinuous. The other biofilter was subjected to continuous contaminant loading during the initial start period, and then was switched to intermittent loading conditions. Experimental results demonstrate that both startup strategies can ultimately achieve high contaminant removal efficiency (>99%) at a target contaminant mass loading rate of 80.3 g m(-3) hr(-1) and an empty bed residence time of 59 sec. The biofilter subjected to intermittent loading conditions at startup, however, took considerably longer to reach high performance. In both biofilters, ketone components (acetone and methyl ethyl ketone) were, more rapidly degraded than aromatic hydrocarbons (toluene, ethylbenzene, and p-xylene). Scanning electron microscopy and plate count data revealed that fungi, as well as bacteria, populated the biofilters.
The microbial communities established in three laboratory-scale compost matrix biofilters fed with toluene were characterized. The biofilters were operated for 7 weeks at inlet concentrations of toluene ranging over 250-500 ppm with daily irrigation, using a nutrient solution containing variable concentrations of nitrogen, supplied as urea, and other inorganic salts. The indigenous microflora of the compost included toluene-degrading species, making inoculation unnecessary. The numerically predominant toluene-degrading strains were isolated from the most diluted positive wells of most-probable-number counts on mineral medium with toluene as sole carbon source and identified by rRNA 16S gene sequencing. On the basis of sequence similarity, all the isolated strains were assigned to the species Pseudomonas putida, although some variations were observed in their respective sequences. It is concluded that the mode of biofilter operation including a daily supply of non-carbon nutrients created an environment favoring the constant numerical predominance of this fast-growing toluene-degrading species.
A biofilter packed with granular activated carbon (GAC) was applied to eliminate volatile-sulfur compounds (VSC) emitted from solid-liquid separation tank in swine wastewater treatment system. Hydrogen sulfide, methanethiol, dimethyl disulfide, and dimethyl sulfide were effectively reduced to 96-100% at gas residence times of 13-30s. Elemental sulfur and sulfate are their primary oxidation metabolites. Regarding odor, an average of 86% reduction was achieved at short residence time (13s). In addition, bioaerosol emissions could also be effectively reduced by 90% with the biofilter. Advantages of the system include low moisture demand, low pressure drop, and high biofilm stability. Further characterization of bacterial populations of the activated carbon samples using the fluorescent in situ hybridization (FISH) technique revealed that Pseudomonas sp. remained the predominant community (56-70%) after long-term evaluation of 415 days.
In the present study, removal of methyl ethyl ketone (MEK), toluene, n-butyl acetate and o-xylene (MTBX) emitted from the paint industry was carried out in a coal based biotrickling filter. When the influent MTBX loadings were less than 120 gm(-3)h(-1), nearly 100% removal could be achieved. A maximum elimination capacity of 184.86 gm(-3)h(-1) was obtained at a MTBX load of 278.27 gm(-3)h(-1) with an empty bed residence time of 42.4s in phase V. Results showed that the condition was the most favorable for n-butyl acetate degradation followed by MEK, toluene and then o-xylene. The corresponding maximum removal rate, r(max) values of MTBX were calculated as 0.085, 0.033, 0.16 and 0.024 gm(-3)h(-1), respectively. Standard deviation of error in prediction of MEK, toluene and o-xylene removal were within limit of 10%, while in the case of n-butyl acetate this was approximately 60%. The MTBX concentration profiles along the depth were also determined by using convection-diffusion reaction (CDR) model. It was observed that at low concentration and low flow rate, the model is in good agreement with the experimental values for MEK, toluene and n-butyl acetate, but for o-xylene the model results deviated from the experimental.
Biofiltration of the exhaust gas contaminated by six VOC compounds for testing the feasibility of its application to a painting process
- T Higuchi
- Y Morita
- R Minato
T. Higuchi, Y. Morita, R. Minato, Biofiltration of the exhaust gas contaminated by six VOC compounds for testing the feasibility of its application
to a painting process, in: Proceedings of the 2010 Duke-UAM Conference
on Biofiltration for Air Polllution Control, Washington, October 28-29, 2010,
pp. 273-278.
Pilot-scale evaluation of a biotrickling filter as a VOC control technology for plastic coating facilities in the automotive sector
- F J Álvarez-Hornos
- V Martínez-Soria
- J M Penya-Roja
- C Lafita
- P Marzal
- C Gabaldón
F.J. Álvarez-Hornos, V. Martínez-Soria, J.M. Penya-Roja, C. Lafita, P. Marzal, C.
Gabaldón, Pilot-scale evaluation of a biotrickling filter as a VOC control technology for plastic coating facilities in the automotive sector, in: Proceedings
of the 2010 Duke-UAM Conference on Biofiltration for Air Pollution Control,
Washington, October 28-29, 2010, pp. 7-14.