Biofiltration of ketone compounds by a composite bead biofilter

In this study, the biochemical kinetic behaviors of ketone compounds in a composite bead biofilter were investigated. Both microbial growth rate kg and biochemical reaction rate kd would be inhibited at higher average inlet concentration. For the microbial growth process, the inhibitive effect was the least pronounced for acetone and the order of kg value was MEK>MIPK>acetone in the average inlet concentration range of 100-150 ppm. The degree of inhibitive effect was almost the same for three ketone compounds and the order of kg value was acetone>MEK>MIPK in the average inlet concentration range of 200-300 ppm. The values of half-saturation constant Ks for acetone, MEK and MIPK were 26.80, 21.56 and 22.96 ppm, respectively. The values of maximum reaction rate Vm for acetone, MEK and MIPK were 8.55, 9.06 and 7.55 g-C/h-kg packed material, respectively. The zero-order kinetic with the diffusion rate limitation could be regarded as the most adequate biochemical reaction model. For the biochemical reaction process, the inhibitive effect was the most pronounced for MEK and the order of kd value was MEK>acetone>MIPK in the average inlet concentration range of 100-150 ppm. The degree of inhibitive effect was MIPK>MEK>acetone and the order of kd value was acetone>MEK>MIPK in the average inlet concentration range of 200-300 ppm. The maximum elimination capacity of acetone, MEK and MIPK were 0.157, 0.127 and 0.101 g-C/h-kg packed material.     

Biochemical kinetic behaviors between n-butyl acetate and composite bead in biofilter

In this study, the kinetic behaviors between n-butyl acetate and composite bead were investigated. Both microbial growth rate and biochemical reaction rate would be inhibited with increasing average inlet concentration. The order of the inhibitive effect, which resulted from increased average inlet concentration for four operation temperatures, was 30>35>40>25 °C. Both microbial growth rate and biochemical reaction rate would be enhanced and inhibited with increasing operation temperature in the operation temperature ranges of 25 to 30 and 30 to 40 °C, respectively. The enhancing and inhibitive effects resulting from increased operation temperature were the most pronounced at the average inlet concentration of 200 ppm. The values of maximum reaction rate V _m and half-saturation constant K _s ranged from 0.011 to 0.047 g C h⁻¹ kg⁻¹ packed material and from 19.30 to 62.40 ppm, respectively. The zero-order kinetic with the diffusion rate limitation could be regarded as the most adequate biochemical reaction kinetic model. The values of maximum elimination capacity ranged from 0.51 to 0.20 g C h⁻¹ kg⁻¹ packed material, and the optimal maximum elimination capacity of biofilter occurred at the operation temperature of 30 °C.     

Kinetic characteristics of n-butyl alcohol and iso-butyl alcohol in a composite bead air biofilter

Kinetic characteristics of n-butyl alcohol and iso-butyl alcohol in a composite bead biofilter were investigated. The microbial growth rate of n-butyl alcohol was greater than that of iso-butyl alcohol in the average inlet concentration range of 50-300 ppm. The microbial growth rate was inhibited at higher inlet concentration, and the inhibitive effect in the concentration range of 50-150 ppm was more pronounced than that in the concentration range of 150-300 ppm. The degree of inhibitive effect for n-butyl alcohol was more sensitive than that for iso-butyl alcohol in the concentration range of 50-150 ppm. The zero-order kinetic with the diffusion rate limitation could be regarded as the most adequate biochemical reaction model. The biodegradation rate of n-butyl alcohol was greater than that of iso-butyl alcohol in the average inlet concentration range of 50-300 ppm. The biochemical reaction rate was also inhibited at higher inlet concentration, and the inhibitive effect for iso-butyl alcohol was more pronounced than that for n-butyl alcohol. The factor of the chemical structure of compound was more predominant in the microbial growth and biochemical reaction processes. The maximum elimination capacity of n-butyl alcohol and iso-butyl alcohol were 55.7 and 34.8 g C h(-1)m(-3) bed volume, respectively. The compound with no side group in the main chain would be easier biodegraded by the microbial.     

Biodegradation kinetic behaviors of n-butyl alcohol and sec-butyl alcohol in a composite bead biofilter

Biodegradation kinetic behaviors of n-butyl alcohol and sec-butyl alcohol in a composite bead biofilter were investigated. The microbial growth rate of n-butyl alcohol was greater than that of sec-butyl alcohol in the inlet concentration range of 50–300 ppm. The microbial growth rate was inhibited at higher inlet concentration, and the inhibitive effect in the concentration range of 50–150 ppm was more pronounced than that in the concentration range of 150–300 ppm. The degree of inhibitive effect for n-butyl alcohol was more sensitive than that for sec-butyl alcohol in the concentration range of 50–150 ppm. The zero-order kinetic with the diffusion rate limitation could be regarded as the most adequate biochemical reaction model. For the biochemical reaction process, the biochemical reaction rate coefficient of n-butyl alcohol was greater than that of sec-butyl alcohol in the inlet concentration range of 50–300 ppm. The biochemical reaction rate coefficient was decreased with increasing inlet concentration. The inhibitive effect for sec-butyl alcohol was more pronounced than that for n-butyl alcohol. The factor of the chemical structure of compound was more predominant in the microbial growth and biochemical reaction processes. The maximum elimination capacity of n-butyl alcohol and sec-butyl alcohol were 55.7 and 20.9 g C h^?1 m^?3 bed volume, respectively. The primary alcohol was easily biodegraded by the microbial.     

Biodegradation of Methyl Ethyl Ketone and Methyl Isopropyl Ketone in a Composite Bead Biofilter

Biodegradation of methyl ethyl ketone (MEK) and methyl isopropyl ketone (MIPK) in a composite bead biofilter was investigated. The composite bead represents a spherical PVA/peat/KNO₃/GAC one. Both the microbial growth rate μ and the biochemical reaction rate coefficient k_d could be affected with increasing inlet concentration. For the microbial growth process, an inhibitory effect of almost the same sensitivity for the two ketone compounds and the μ value of MEK was more pronounced than that of MIPK in the inlet concentration range of 100 to 300 ppm. The half‐saturation constant K_s values of MEK and MIPK were 21.56 and 22.96 ppm, respectively. The maximum reaction rate V_m values of MEK and MIPK were 9.06 and 7.55 g C/h kg of packed material, respectively. Zero‐order kinetics with diffusion limitation could be regarded as the most adequate biochemical reaction model. For the biochemical process, the inhibitory effect for MEK was more notable than that for MIPK in the inlet concentration range of 100 to 150 ppm whereas it was the reverse in the inlet concentration range of 150 to 300 ppm. The k_d value of MEK was greater than that of MIPK in the inlet concentration range of 100 to 300 ppm. The maximum elimination capacities of MEK and MIPK were found to be 44.2 and 35.2 g C/h m³ of bed volume. MEK, in particular the compound with a lower number of carbons or no side groups in the main chain, was easier biodegraded by the microorganisms than MIPK.     

Biofiltration of ethyl acetate and amyl acetate using a composite bead biofilter

Biodegradation kinetic behaviors of ethyl acetate and amyl acetate in a composite bead biofilter were investigated. The composite bead was the spherical PVA/peat/KNO(3)/GAC composite bead which was prepared in our previous works. Both microbial growth rate and biochemical reaction rate were inhibited at higher inlet concentration. For the microbial growth process, the microbial growth rate of ethyl acetate was greater than that of amyl acetate in the inlet concentration range of 100-400ppm. The degree of inhibitive effect was almost the same for ethyl acetate and amyl acetate in this concentration range. The half-saturation constant K(s) values of ethyl acetate and amyl acetate were 16.26 and 12.65ppm, respectively. The maximum reaction rate V(m) values of ethyl acetate and amyl acetate were 4.08 and 3.53gCh(-1)kg(-1) packed material, respectively. Zero-order kinetic with the diffusion limitation could be regarded as the most adequate biochemical reaction model. For the biochemical reaction process, the biochemical reaction rate of ethyl acetate was greater than that of amyl acetate in the inlet concentration range of 100-400ppm. The inhibitive effect for ethyl acetate was more pronounced than that for AA in this concentration range. The maximum elimination capacity of ethyl acetate and amyl acetate were 82.3 and 37.93gCh(-1)m(-3) bed volume, respectively. Ethyl acetate degraded by microbial was easier than amyl acetate did.     

The start-up period of styrene degrading biofilters

Styrene vapors from contaminated air were eliminated using long-term adapted mixed microbial culture inoculated on four perlite packed biofilters (serial arrangement, up-flow configuration). During start-up the inlet concentration of styrene rose from 175 to 1300 mg/m³ of total carbon. The total actual residence time in the four biofilters was 24 s. Styrene was successfully degraded by the microbial population in the biofilter. An average of 66% of eliminated styrene was transformed to CO₂. The removal efficiency of the pollutant was, after 18 d of start-up, nearly 85% at an organic load of 170g/m³ per h. The concentration profiles along the bed height were linear for various pollutant inlet concentrations. The total amount of microorganisms in analyzed biomass from the biofilters was about 10⁹ per gram of dry packing mass. The moisture content was around 80% in all biofilters.     

增加降水对干旱河谷区云南松人工林土壤呼吸的影响

2013年5月至2014年6月,对干旱河谷区云南松(Pinus yunnanensis)人工林进行增加降水试验,试验设置对照(CK,0 mm m~(-2)a~(-1))、增水10%(A1,80 mm m~(-2)a~(-1))、增水20%(A2,160 mm m~(-2)a~(-1))和增水30%(A3,240 mm m~(-2)a~(-1))4个处理水平。采用LI-8100开路式土壤碳通量测量系统测定每月土壤呼吸速率。结果表明,4个处理云南松人工林土壤呼吸速率均呈明显的季节变化,7月最高,2月最低。与CK相比,A1年均土壤呼吸速率无显著性差异(P0.05),A2显著增加了12.88%(P0.05),而A3明显减少了17.71%(P0.05)。3个增水处理均提高了土壤呼吸的温度敏感性,减弱了土壤呼吸与土壤湿度的关系。与土壤温度相比,土壤湿度对土壤呼吸的影响相对较小。增水增加了湿季土壤微生物碳、氮含量,干季对微生物碳含量无影响,但明显降低了微生物氮含量。这说明,降水增加对干旱河谷区云南松人工林土壤呼吸的影响是不尽相同的,适当的增水会促进土壤呼吸,而过量的增水会抑制土壤呼吸。     

Biotrickling air filtration of 2-chlorophenol at high loading rates

The degradation of 2-chlorophenol vapours in air was performed in a trickling biofilter packed with ceramic material seeded with the bacterium Pseudomonas pickettii, strain LD1. The system performance was evaluated under varying operating conditions (inlet 2-chlorophenol air concentrations from 0.10 to 3.50 g m^?3, and superficial air velocities of 30.0, 60.0, and 120.0 m h^?1). For all air velocity the maximum degradation rate was obtained for loading rates of 40 g m^?2 h^?1. Higher loading conditions resulted in strong inhibition of microbial activity, particularly severe at high air velocity. Process analysis, performed using data on pollutant concentration profiles along the filter packing obtained under different conditions of inlet concentration and air velocity, proves that best performance (i.e. maximum degradation efficiency and capacity) can be obtained for a narrow range of operating conditions, which can be ensured by proper design of biofilter size (i.e. diameter and height). Kinetic analysis of experimental data confirms that 2-CP inhibits microbial activity in the biofilter bed. Experimental data are satisfactorily fitted by the Haldane kinetic equation up to a critical value of loading rate, beyond which the experimental degradation rate is overestimated by the kinetic model. The inhibition appears to be affected by the loading rate, and the estimated inhibition constant linearly increases with increasing empty bed residence time.     

Simulation of glucose isomerase reactor: optimum operating temperature

A design equation for immobilized glucose isomerase (IGI) packed bed reactor is developed assuming enzyme deactivation and substrate protection. The developed equation is used to simulate the performance of the reactor at various temperatures (50–80 °C). Enzyme deactivation is significant at high temperature. Substrate protection showed to have significant effect in reducing enzyme deactivation and increasing the enzyme half-life. Factors affecting the optimum operating temperature are discussed. The optimum operating temperature is greatly influenced by the operating period and to a lesser extent with both initial glucose concentration and glucose conversion.Two modes of reactor operation are tested i.e., constant feed flow rate and constant conversion. Reactor operating at constant conversion is more productive than reactor operating at constant flow rate if the working temperature is higher than the optimum temperature. Although at lower temperatures than the optimum, the two modes of operation give the same result.List of Symbols a residual enzyme activity - E [mg/l] concentration of active enzyme - E _a [kJ/mole] activation energy - E ₀ [mg/l] initial concentration of active enzyme - k [Specific] kinetic parameter - k _d [h^–1] first order thermal deactivation rate constant - k _e equilibrium constant - k _m [mole/l] apparent Michaelis constant - k _p [mole/l] Michaelis constant for product - k _s [mole/l] Michaelis constant for substrate - k ₀ [Specific] pre-exponential factor - Q [1/h] volumetric flow rate - ¯Q [1/h] average volumetric flow rate - R [kJ/mol·k] ideal gas constant - s [mole/l] apparent substrate concentration - s [mole/l] substrate concentration - s _e [mole/l] substrate concentration at equilibrium - s ₀ [mole/l] substrate concentration at reactor inlet - p [mole/l] product concentration - p _e [mole/l] product concentration at equilibrium - P _r [mole fructose/l·h] reactor productivity - T [k] temperature - t [h] time - t _p [h] operating time - V [l] reactor volume - v [mole/l·h] reaction rate - v [mole/l] reaction rate under enzyme deactivation and substrate protection - v _m [mole/l·h] maximum apparent reaction rate - v _p [mole/l·h] maximum reaction rate for product - v _s [mole/l·h] maximum reaction rate for substrate - x substrate fractional conversion - x _e substrate fractional conversion at equilibrium Greek Symbols effectiveness factor - mean effectiveness factor - substrate protection factor - [h] residence time - [h] average residence time - ₀ [h] initial residence time     

Macrokinetic and quantitative microbial investigation on a bench-scale biofilter treating styrene-polluted gaseous streams

We performed a macrokinetic and quantitative microbial investigation of a continuously operating bench-scale biofilter treating styrene-polluted gases. The device was filled with a mixture of peat and glass beads as packing medium and inoculated with the styrene-oxidizing strain, Rhodococcus rhodochrous AL NCIMB 13259. The experimental data of styrene and microbial concentrations, obtained at different biofilter heights, were used to evaluate the pollutant concentration profiles as well as the influence of styrene loading on biomass distribution along the packing medium. Styrene and biomass concentration profiles permitted detection of a linear relationship between the amount of biomass grown in a given section of the biofilter and that of pollutant removed, regardless of the operating conditions tested. Biomass development in the bed appeared to: depend linearly on pollutant concentration at an inlet styrene concentration of <0.10 g m(-3) in the gaseous stream; achieve a maximum value (7. 10(7) colony forming units per gram of packing material) within a wide styrene concentration range (0.10 to 1.0 g m(-3)); and fall sharply beyond this inhibition threshold. The process followed zeroth-order macrokinetics with respect to styrene concentration, which is consistent with zeroth-order microkinetics with either fully active or not fully active biofilm. The maximal volumetric styrene removal rate was found to be 63 g m(packing material) (-3) h(-1) for an influent pollutant concentration of 0.80 g m(-3) and a superficial gas velocity of 245 m h(-1).     

Kinetic studies of constitutive human granulocyte-macrophage colony stimulating factor (hGM-CSF) expression in continuous culture of <Emphasis Type="Italic">Pichia pastoris</Emphasis>

Extracellular human granulocyte-macrophage colony stimulating factor (hGM-CSF) expression was studied under the control of the GAP promoter in recombinant Pichia pastoris in a series of continuous culture runs (dilution rates from 0.025 to 0.2 h⁻¹). The inlet feed concentration was also varied and the steady state biomass concentration increased proportionally demonstrating efficient substrate utilization and constancy of the biomass yield coefficient (Y_x/s) for a given dilution rate. The specific product formation rate (q_P) showed a strong correlation with dilution rates demonstrating growth associated product formation of hGM-CSF. The volumetric product concentration achieved at the highest feed concentration (4×) and a dilution rate of 0.2 h⁻¹ was 82 mg l⁻¹ which was 5-fold higher compared to the continuous culture run with 1× feed concentration at the lowest dilution rate thus translating to a 40 fold increase in the volumetric productivity. The specific product yield (Y_P/X) increased slightly from 2 to 2.5 mg g⁻¹, with increasing dilution rates, while it remained fairly invariant, for all feed concentrations demonstrating negligible product degradation or feed back inhibition. The robust nature of this expression system would make it easily amenable to scale up for industrial production.     

Effects of Stratification, Gibberellic acid and Germination Temperature on the Germination of Betula nana

Experiments were carried out with three seed lots of Betula nana collected in 1967 from different localities in Norway. Seeds were stratified for 0-20 days in dark at +2-+3 °C on filter papers moistened with distilled water, or treated with solution of GA₃ for 24 h at room temperature, and then moved into special germination boxes that were placed in different temperature conditions. All the seed lots had conditional dormancy. Quantitatively, the dormancy was different in the different seed lots (pronenances), but there were no qualitative difference in the reaction to stratification gibberellic acid and to germination temperature. Differences between seed lots may have been due to different stage of seed development. The dormancy was deepest at low temperatures(12 and 15°C) decreasing gradually with increasing temperature (to 24 °C). The dormancy was effectively broken by a short stratification (from 5 to 15 days), and by treatment with gibberellic acid. The deeper the dormancy and the lower the germination temperature the longer the stratification that was needed for maximum germination. Similarly, the concentration of GA₃ needed for maximum germination increased with decreasing temperature and with increasing dormancy.     

Mathematical modeling of Kluyveromyces marxianus growth in solid-state fermentation using a packed-bed bioreactor

This work investigated the growth of Kluyveromyces marxianus NRRL Y-7571 in solid-state fermentation in a medium composed of sugarcane bagasse, molasses, corn steep liquor and soybean meal within a packed-bed bioreactor. Seven experimental runs were carried out to evaluate the effects of flow rate and inlet air temperature on the following microbial rates: cell mass production, total reducing sugar and oxygen consumption, carbon dioxide and ethanol production, metabolic heat and water generation. A mathematical model based on an artificial neural network was developed to predict the above-mentioned microbial rates as a function of the fermentation time, initial total reducing sugar concentration, inlet and outlet air temperatures. The results showed that the microbial rates were temperature dependent for the range 27–50°C. The proposed model efficiently predicted the microbial rates, indicating that the neural network approach could be used to simulate the microbial growth in SSF.     

Detachment and emission of airborne bacteria in gas-phase biofilm reactors

Three laboratory scale biofilters filled with different packing materials (peat and sieved sugarcane bagasse) and operating with different microbial cultures (allochthonous and autochthonous bacteria) were run and monitored in parallel to assess the emission rate of airborne bacteria in the biofiltration of benzene-contaminated air streams. The effect of the fluid dynamic and loading conditions on the rate of microbial emission in the air environment was investigated by performing continuous experiments at different inlet benzene concentrations and superficial gas velocities. The experiments prove that the concentration of airborne bacteria in the effluent air from lab-scale biofilters is only slightly higher than in the ambient air. The emission rate is not dependent on superficial gas velocity because of low shear stress exerted by the gas flow. On the other hand, the loading conditions have a strong effect on the emission rate, which increases with increasing growth and degradation rate, and different packing media show remarkably different behaviors.     

Treatment of odorous volatile fatty acids using a biotrickling filter

In this study, a novel fibrous bioreactor was developed for treating odorous compounds present in contaminated air. The first stage of this work was a preliminary study which aimed at investigating the feasibility of using the fibrous bioreactor for the removal of malodorous volatile fatty acids (VFA) that is a common odorous contaminant generated from anaerobic degradation of organic compounds. The kinetics of microbial growth and VFA degradation in the selected culture, and the performance of the submerged bioreactor at different VFA mass loadings were studied. Above 95% of VFA removal efficiencies were achieved at mass loadings up to 22.4 g/m(3)/h. In the second stage, the odour treatment process was scaled up with system design and operational considerations. A trickling biofilter with synthetic fibrous packing medium was employed. The effects of inlet VFA concentration and empty bed retention time (EBRT) on the process performance were investigated. The bioreactor was effective in removing VFA at mass loadings up to 32 g/m(3)/h, beyond which VFA started to accumulate in the recirculation liquid, indicating the biofilm was unable to degrade all of the VFA introduced. Although VFA accumulated in the liquid phase, the removal efficiency remained above 99%. This suggested that the biochemical reaction rather than gas-liquid mass transfer was the limiting step of the treatment process. In addition, the biotrickling filter was stable for long-term operation with relatively low and steady pressure drop, no clogging and degeneration of the packing material occurred during the four-month study.     

Removal characteristics of high load ammonia gas by a biofilter seeded with a marine bacterium, Vibrio alginolyticus

When the cells of the newly isolated marine bacterium, Vibrio alginolyticus, were inoculated on to an inorganic packing material in biofilter, and a load of ammonia of 2.4–22.5 g-N kg^–1dry packing material was introduced continuously under non-sterile conditions, the average amount of NH₃removed exceeded 85% over 61-d operation. The maximum removal capacity and the complete removal capacity were 22.8 g-N kg^–1dry packing material dand 18.6 g-N kg^–1dry packing material d, respectively, which were about four times larger than those obtained in autotrophic nitrifying sludge inoculated on the same packing material.     

Optimization of operating temperature for continuous glucose isomerase reactor system

The Optimal temperature control policy for an immobilized glucose isomerase reactor system was studied. This optimization study takes into consideration the enzyme deactivation during the continuous reactor operation. The Kinetic parameters including reduced Michaelis–Menten constant (K?_m), reduced maximum reaction rate (V?_m), equilibrium constant (K_e), and enzyme deactivation constant (k_d) and their functional relationships to temperature were determined experimentally. The optimization problem was formulated in terms of maximization of fructose productivity as the objective function. The optimization problem was solved by making use of a maximum principle and the control vector iteration method. Approximately optimal temperature control policy was employed as compared with the reactor operation at an optimum constant temperature.     

Exhaust gas purification using biocatalysts (fixed bacteria monocultures) — the influence of biofilm diffusion rate (O2) on the overall reaction rate

Summary This paper presents results of experiments on the influence of O₂ and substrate (pollutant) concentration on the overall reaction rate of a trickle-bed reactor used for biological waste gas purification. The biocatalyst was a pollutant-specific bacterial monoculture fixed on porous glass carriers. The conversion of acetone and propionaldehyde, as model pollutants that are easily soluble in water, was measured. Under constant hydrodynamic conditions (gas and liquid flow rates) the inlet pollutant concentration was varied. The O₂ partial pressure in the model gas was increased to investigate the influence of O₂ supply on pollutant conversion. At higher pollutant concentrations (>117 mg acetone.m^-3 gas and > 150 mg propionaldehyde.m^-3 gas) higher concentrations of dissolved O₂ led to a significant rise in the maximum degradation capacity of the reactor. This maximum reaction rate was independent of the pollutant mass flow. It seems that the diffusion of O₂ in the biofilm is rate-determining. The reaction rate at lower inlet concentrations was not affected by the improved O₂ supply. Here the external mass transfer through the liquid film limits the reaction rate and the maximum separation efficiency of about 80% at a residence time of 1.2s (space velocity 3000h^-1) is achieved.     

Biohydrogen production from carbon monoxide and water byRhodopseudomonas palustris P4

A reactor-scale hydrogen (H₂) productionvia the water-gas shift reaction of carbon monoxide (CO) and water was studied using the purple nonsulfur bacterium,Rhodopseudomonas palustris P4. The experiment was conducted in a two-step process: an aerobic/chemoheterotrophic cell growth step and a subsequent anaerobic H₂ production step. Important parameters investigated included the agitation speed, inlet CO concentration and gas retention time. P4 showed a stable H₂ production capability with a maximum activity of 41 mmol H₂ g cell⁻¹h⁻¹ during the continuous reactor operation of 400 h. The maximal volumetric H₂ production rate was estimated to be 41 mmol H₂ L¹h⁻¹, which was about nine-fold and fifteen-fold higher than the rates reported for the photosynthetic bacteriaRhodospirillum rubrum andRubrivivax gelatinosus, respectively. This is mainly attributed to the ability of P4 to grow to a high cell density with a high specific H₂ production activity. This study indicates that P4 has an outstanding potential for a continuous H₂ productionvia the water-gas shift reaction once a proper bioreactor system that provides a high rate of gas-liquid mass transfer is developed.