Monod Kinetic Model Research Articles

Modeling and control of dissolved oxygen concentration in the fermentation of Glucose to Gluconic Acid

Fermentation systems are often highly nonlinear, with poorly understood dynamic behaviour of the reactor. In this work, mathematical modeling of the fermentation process based on aeration rate control was performed in a semi-batch airlift loop bioreactor. The bioconversion of glucose to gluconic acid by the Aspergillus niger strain was considered in an oxygen consuming system in the liquid phase. The proper kinetic model for the bioconversion of glucose to gluconic acid was investigated using experimental data from a 40 dm3 reactor. Kinetic parameter estimation was used from the literature. The model was validated by experimental data and was compared with the Monod kinetic model. The comparison showed that the Contois kinetic model was in a better agreement with the experimental data of dissolved oxygen concentration (DO) than the Monod kinetic model. An optimal substrate-to-microorganism concentration ratio of 55 was suggested by applying the model, which led to achieving the maximum conversion of glucose to gluconic acid. The conventional PID controller with fixed parameters obtained from the Ziegler-Nichols tuning method was used to control the dissolved oxygen concentration at a constant level of 2 mg/dm3, which was important for microorganism survival and growth.

Process model comparison and transferability across bioreactor scales and modes of operation for a mammalian cell bioprocess

A Monod kinetic model, logistic equation model, and statistical regression model were developed for a Chinese hamster ovary cell bioprocess operated under three different modes of operation (batch, bolus fed-batch, and continuous fed-batch) and grown on two different bioreactor scales (3 L bench-top and 15 L pilot-scale). The Monod kinetic model was developed for all modes of operation under study and predicted cell density, glucose glutamine, lactate, and ammonia concentrations well for the bioprocess. However, it was computationally demanding due to the large number of parameters necessary to produce a good model fit. The transferability of the Monod kinetic model structure and parameter set across bioreactor scales and modes of operation was investigated and a parameter sensitivity analysis performed. The experimentally determined parameters had the greatest influence on model performance. They changed with scale and mode of operation, but were easily calculated. The remaining parameters, which were fitted using a differential evolutionary algorithm, were not as crucial. Logistic equation and statistical regression models were investigated as alternatives to the Monod kinetic model. They were less computationally intensive to develop due to the absence of a large parameter set. However, modeling of the nutrient and metabolite concentrations proved to be troublesome due to the logistic equation model structure and the inability of both models to incorporate a feed. The complexity, computational load, and effort required for model development has to be balanced with the necessary level of model sophistication when choosing which model type to develop for a particular application.

Enhanced Bioethanol Production in Batch Fermentation by Pervaporation Using a PDMS Membrane Bioreactor

The integration of batch fermentation and membrane-based pervaporation process in a membrane bioreactor (MBR) was studied to enhance bioethanol production compared to conventional batch fermentation operated at optimum condition. For this purpose, a laboratory-scale MBR system was designed and fabricated. Dense hydrophobic Polydimethylsiloxane (PDMS) membrane was used for pervaporation. For fermentation, pure stock culture of Saccharomyces cerevisiae as microorganism and glucose as substrate were used. Compared to conventional batch fermentation, the MBR resulted in increase of cell density, decreasing ethanol inhibition, improved productivity and yield, and resumption of clean and concentrated ethanol. These effects can be attributed to the presence of membrane as a selective separation barrier for removal of ethanol from fermentation broth. The ethanol productivity increased at least by 26.83% over conventional batch fermentation; while concentrated ethanol was obtained in the condensate of cold-trap. Furthermore, ethanol concentration in permeated side was approximately 6 to 7 times higher than that of the broth. Some biological kinetic models were investigated for determination of growth rate kinetics in conventional and MBR batch fermentation. The best results were obtained using the Monod kinetic model.

Coupled transport and reaction kinetics control the nitrate source‐sink function of hyporheic zones

The fate of biologically available nitrogen (N) and carbon (C) in stream ecosystems is controlled by the coupling of physical transport and biogeochemical reaction kinetics. However, determining the relative role of physical and biogeochemical controls at different temporal and spatial scales is difficult. The hyporheic zone (HZ), where groundwater–stream water mix, can be an important location controlling N and C transformations because it creates strong gradients in both the physical and biogeochemical conditions that control redox biogeochemistry. We evaluated the coupling of physical transport and biogeochemical redox reactions by linking an advection, dispersion, and residence time model with a multiple Monod kinetics model simulating the concentrations of oxygen (O2), ammonium (NH4), nitrate (NO3), and dissolved organic carbon (DOC). We used global Monte Carlo sensitivity analyses with a nondimensional form of the model to examine coupled nitrification‐denitrification dynamics across many scales of transport and reaction conditions. Results demonstrated that the residence time of water in the HZ and the uptake rate of O2 from either respiration and/or nitrification determined whether the HZ was a source or a sink of NO3 to the stream. We further show that whether the HZ is a net NO3 source or net NO3 sink is determined by the ratio of the characteristic transport time to the characteristic reaction time of O2 (i.e., the Damköhler number, DaO2), where HZs with DaO2 < 1 will be net nitrification environments and HZs with DaO2 ≪ 1 will be net denitrification environments. Our coupling of the hydrologic and biogeochemical limitations of N transformations across different temporal and spatial scales within the HZ allows us to explain the widely contrasting results of previous investigations of HZ N dynamics which variously identify the HZ as either a net source or sink of NO3. Our model results suggest that only estimates of residence times and O2uptake rates are necessary to predict this nitrification‐denitrification threshold and, ultimately, whether a HZ will be either a net source or sink of NO3.

Performance Evaluation of Sequencing Batch Reactor for Beverage Industrial Wastewater Treatment

Attempts were made in this study to examine the effectiveness of sequencing batch reactor (SBR) for the treatment of beverage industrial wastewater. The SBR was operated at three different organic loading rates (OLRs): 2, 1.7 and 1.1 kg COD/m3 d. Results of continuous long-term operation showed that by decreasing OLR from 2 to 1.7 kg COD/m3 day, the removal efficiency was increased from 95.5 to 99.3% for COD, from 95.3 to 98.1% for BOD and from 87 to 97.7% for TSS. While further decreasing of the OLR to 1.1 kg COD/m3 day, there is no significant adverse effect on organics removal. Also, residual total nitrogen (TN) concentration decreased by decreasing the OLR. However, increasing the OLRs exerted a slightly negative effect on the removal of total phosphorous. On the other hand, the experimental data indicated that the substrate utilization kinetic followed Monod's kinetics model approximately. The maximum specific substrate utilization rate (micro(max), half velocity coefficient (Ks), growth yield coefficient (Y) and decay coefficient (Kd) were 2.94 d(-1), 15.22 mg/L, 0.2384 g VSS/g COD and 0.2019 h(-1), respectively.

Evaluation of microbial systems for biotreatment of cassava mill waste water in Nigeria: biodegradation of cyanide

The capability of six isolated bacterial strains to utilise cyanide in cassava mill wastewater as a nitrogen source in a batch bioreactor was examined and evaluated. The results revealed that all the isolates were capable of degrading cyanide with percent degradation between 60 and 94% in 96 h. There was high positive correlation between cyanide biodegradation and microbial growth (0.90 ≤ R2 ≤ 0.97). The Monod kinetic model adequately described the dynamic behaviour of cyanide degradation by the different bacterial isolates. Thus, the study revealed the possibility of using the bacterial isolates in the biotreatment of cyanide waste effluents.

Biodegradation of tobacco waste by composting: Genetic identification of nicotine-degrading bacteria and kinetic analysis of transformations in leachate

AbstractThe tobacco industry produces large quantities of solid and liquid waste. This waste poses a significant environmental problem, as some major components are harmful and toxic. The aim of this work is to isolate and identify the nicotine-degrading microorganisms in the composting of tobacco waste. The bioremediation process for the detoxification of waste was carried out in a column reactor at an airflow-rate of 0.4 L min−1 kg−1. The concentrations of nicotine and number of CFU in the samples taken from reactor were monitored over nineteen days. After nineteen days, 89.8 % of nicotine conversion was obtained. A nicotine-degrading bacterium, strain FN, was isolated from the composting mass and identified as Pseudomonas aeruginosa on the basis of morphology, 16S rDNA sequence, and the phylogenetic characteristics. To confirm that the isolated Pseudomonas aeruginosa FN is the actual nicotine degrader, batch experiments were performed using tobacco leachate. It was confirmed that the strain FN possesses a considerable capacity to degrade nicotine with simultaneous COD removal. The Monod kinetic model for single substrate was applied to obtain the substrate degradation rate and half saturation constant.

Growth kinetic models for phenol biodegradation in a batch culture of Pseudomonas putida

Biodegradation of phenol with pure culture of Pseudomonas putida was investigated. P. putida (PTCC 1694) was grown in facultative anaerobic condition at 27°C and media pH value of 7. The effect of initial phenol concentration on the biodegradation rate was studied. The initial concentrations of phenol varied from 300 to 1000 mg/l. Experiments were performed for the duration of seven days while daily samples were withdrawn. The initial rate of biodegradation of phenol increased with initial concentration of 300–500 mg/l. Further increase in phenol concentration resulted in a slight decrease in the rate of biodegradation due to phenol inhibition. It was observed that by increasing the concentration of phenol, the lag phase was prolonged. Phenol is known to be an inhibitory substrate, thus Monod, Haldane and logistic kinetic models were applied to evaluate the growth kinetic parameters. The Monod model was unable to present the growth parameters over the defined concentration range. However, Haldane and logistic models perfectly fitted with the experimental data. The yield coefficients for the growth on phenol at concentrations of 300, 500, 700 and 1000 mg/l were 0.177, 0.062, 0.035 and 0.012 mg/mg, respectively.

Multisubstrate monod kinetic model for simultaneous degradation of chlorophenol mixtures

Chlorophenols (CPs) are persistent and highly toxic compounds rated as priority pollutants by the Environmental Protection Agency (EPA). Frequently, these compounds are present as mixtures of CPs in industrial wastewaters. Therefore the study of biodegradation on mixed pollutants is an important aspect of biodegradation and wastewater treatment. In this work, we studied the multisubstrate degradation of CPs by a mixed culture of Pseudomonas aeruginosa and a novel Acromobacter sp. capable of using pentachlorophenol (PCP), 2,4,6 trichlorophenol (2,4,6 TCP) and 2,3,5,6 tetrachlorophenol (2,3,5,6 TeCP) as the sole sources of carbon and energy. The main objective of this work was to evaluate the effect of substrate mixtures on the degradation kinetics of PCP. Batch experiments were conducted with each CP separately and in mixtures of PCP + 2,4,6 TCP, PCP + 2,3,5,6 TeCP, and PCP + 2,4,6 TCP + 2,3,5,6 TeCP. Based upon our results we have concluded that the simultaneous degradation of CPs is a key factor contributing to the improvement of PCP degradation. The kinetic parameters for PCP and 2,4,6 TCP were obtained by fitting the data to a Monod kinetics model. Using such parameters, the model was able to predict simultaneous multisubstrate degradation of PCP with others CPs.

Kinetic model for an up-flow anaerobic packed bed bioreactor: Dairy wastewater treatment

Kinetic studies of anaerobic digestion process of cheese whey were conducted in a pilot-scale up-flow anaerobic packed bed bioreactor (UAPB). An influent COD concentration of 59419 mg/l was utilized at steady state condition. Logistic and Monod kinetic models were employed to describe microbial activities of cheese whey in an anaerobic digester. The hydraulic retention times (HRT) in the range of 6 to 24 h were investigated throughout the experiments. Lactose conversions were 58.5 and 99.4% for HRT of 6 and 16 h, respectively. The methane production rates were 6.57 and 3.25 l/h for HRT of 6 and 24 h, respectively. Monod biokinetic coefficients, K s, s, s, m m and methane yield (Y M ) were 8.59, 7.63 (h -1 ) and 0.11 (g methane/g lactose), respectively

Bioaugmentation for chlorinated ethenes using Dehalococcoides sp.: Comparison between batch and column experiments

Batch and column experiments were performed to evaluate the transport, growth and dechlorination activity of Dehalococcoides sp. (DHC) during bioaugmentation for chlorinated ethenes. Batch experiments showed that the reductive dechlorination of trichloroethene (TCE), cis-1,2-dichloroethene (DCE), and vinyl chloride (VC), as well as growth of the DHC, were well described by the Monod kinetic model. The measured maximum utilization rate coefficients for TCE, DCE, and VC were 1.3 × 10 −12, 5.2 × 10 −13, and 1.4 × 10 −12 mmol Cl − (cell h) −1, respectively. Results of the column experiments showed that dechlorination occurred throughout the length of the column, and that extractable DHC concentrations associated with the soil phase throughout the column were negligible relative to the aqueous phase concentrations. Dechlorination rates relative to aqueous DHC concentrations in the column were approximately 200-times greater than in the batch experiments. Additional batch experiments performed using column effluent water confirmed this result. Incorporation of these enhanced dechlorination kinetics in the transport model provided a reasonable prediction of the column data. Overall results of this study suggest that aqueous phase (as opposed to soil phase) DHC concentrations can be used to estimate dechlorination activity in saturated soils, and DHC dechlorination activity in porous media may be substantially greater than DHC dechlorination activity measured in batch experiments.

Modeling of Xanthophyllomyces dendrorhous growth on glucose and overflow metabolism in batch and fed‐batch cultures for astaxanthin production

An astaxanthin-producing yeast Xanthophyllomyces dendrorhous ENM5 was cultivated in a liquid medium containing 50 g/L glucose as the major carbon source in stirred fermentors (1.5-L working volume) in fully aerobic conditions. Ethanol was produced during the exponential growth phase as a result of overflow metabolism or fermentative catabolism of glucose by yeast cells. After accumulating to a peak of 3.5 g/L, the ethanol was consumed by yeast cells as a carbon source when glucose in the culture was nearly exhausted. High initial glucose concentrations and ethanol accumulation in the culture had inhibitory effects on cell growth. Astaxanthin production was partially associated with cell growth. Based on these culture characteristics, we constructed a modified Monod kinetic model incorporating substrate (glucose) and product (ethanol) inhibition to describe the relationship of cell growth rate with glucose and ethanol concentrations. This kinetic model, coupled with the Luedeking-Piret equation for the astaxanthin production, gave satisfactory prediction of the biomass production, glucose consumption, ethanol formation and consumption, and astaxanthin production in batch cultures over 25-75 g/L glucose concentration ranges. The model was also applied to fed-batch cultures to predict the optimum feeding scheme (feeding glucose and corn steep liquor) for astaxanthin production, leading to a high volumetric yield (28.6 mg/L) and a high productivity (5.36 mg/L/day).

Development of models for predicting carbon mineralization and associated phytotoxicity in compost-amended soil

Phytotoxicity of compost-amended soil is related to carbon mineralization associated with compost decomposition. The objective of this research was to determine if compost carbon mineralization potential, estimated using compost respiration rate measurements, could be combined with carbon mineralization kinetic models to predict phytotoxicity of compost-amended soil. First-order, second-order, and Monod kinetic models that include compost carbon mineralization potential, compost amendment rate, incubation time, and temperature were developed and compared for their ability to predict carbon mineralization kinetics. Experiments utilized two soil types amended with 0%, 5%, and 50% (v/v) food waste and green waste composts, incubated at 20 °C, 25 °C, 30 °C, 35 °C, and 45 °C for model development and under a diurnal temperature cycle from 20 °C to 30 °C for model validation. For most cases, a first-order model had an equivalent or better fit to the data than the other models. Mineralizable carbon estimated using the first-order model was significantly correlated to the probability of phytotoxicity in compost-amended soil.

Kinetics of batch microbial degradation of phenols by indigenous Pseudomonas fluorescence

The potential of various organisms to metabolize organic compounds has been observed to be a potentially effective means in disposing of hazardous and toxic wastes. Phenols and their compounds have long been recognized as one of the most recalcitrant and persistent organic chemicals in the environment. The bioremediation potential of an indigenous Pseudomonas fluorescence was studied in batch culture using synthetic phenol in water in the concentration range of (100–500) mg/L as a model limiting substrate. The effect of initial phenol concentration on the degradation process was investigated. Phenol was completely degraded at different cultivation times for the different initial phenol concentrations. Increasing the initial phenol concentration from 100 mg/L to 500 mg/L increased the lag phase from 0 to 66 h and correspondingly prolonged the degradation process from 84 h to 354 h. There was decrease in biodegradation rate as initial phenol concentration increased. Fitting data into Monod kinetic model showed the inhibition effect of phenol The kinetic parameters have been estimated up to initial phenol concentration of 500 mg/ L. The rsmax decreased and Ks increased with higher concentration of phenol. The rsmaxhas been found to be a strong function of initial phenol concentration. The culture followed substrate inhibition kinetics and the specific phenol consumption rates were fitted to Haldane, Yano and Koga, Aiba et al., Teissier and Webb models. Between the five inhibition models, the Haldane model was found to give the best fit. Therefore, the biokinetic constants estimated using these models showed good potential of the Pseudomonas fluorescence and the possibility of using it in bioremediation of phenol waste effluents.

Effect of liquid distribution on the organic removal in a trickle bed filter

Abstract The effect of liquid distribution on the biological removal of propylene glycol methyl ether (PGME) in a trickle bed filter was investigated using a 0.3 m diameter column filled with 2-cm plastic spheres. Various liquid flowrates, bed heights (the ratio of bed height to bed diameter H / D = 2.3 and 4.6) and initial concentrations of PGME were used in experiments. The effect of initial liquid distribution was also examined using the multipoint (MPD) and single-point liquid distributors (SPD). The effect of liquid flow rate on liquid distribution, and hence, the BOD 5 removal was found more significant for the short bed ( H / D = 2.3). The BOD 5 removal using MPD increased about 29% when the liquid flow rate was increased from 0.184 to 0.918 kg m −2 s −1 . On the other hand, for H / D = 4.6 with both MPD and SPD, the effect of liquid flowrate on the BOD 5 removal was insignificant although the dynamic liquid hold-up increased about two fold. It was also found that local distribution of the BOD 5 removal corresponded well with local liquid distribution in the bed. In addition, a 37% decrease in the percentage BOD 5 removal was observed while the BOD 5 removal amount increased from 62 to 211 mg L −1 with increases in the initial concentration from 100 to 500 ppm. Based on the Monod kinetic model, the maximum BOD 5 removal rate in the trickle bed filter was found to be 11.7 mg L −1 h −1 and the Monod constant was 759 mg L −1 .

Analytical solutions for bacterial energy taxis (chemotaxis): Traveling bacterial bands

Motile bacteria may form bands that travel with a constant speed of propagation through a medium containing a dissolved substrate, to which they respond energy tactically. We generalize the analytical solution by Keller and Segel for such bands by accounting for (1) the presence of a porous medium, (2) substrate consumption described by a Monod kinetics model, and (3) an energy tactic response model derived by Rivero et al. Specifically, we determine the concentration profiles of the bacteria and the substrate. We also derive various expressions for the band velocity. The band velocity is also shown to equal the energy tactic velocity at the bacterial peak divided by tortuosity.

Kinetics of Chemoheterotrophic Microbially Mediated Reduction of Ferric EDTA and the Nitrosyl Adduct of Ferrous EDTA for the Treatment and Regeneration of Spent Nitric Oxide Scrubber Liquor

Biomass from a prototype reactor was used to investigate the kinetics of chemoheterotrophic reduction of solutions of ferric ethylenediaminetetraacetic acid (EDTA) and solutions containing the nitrosyl adduct of ferrous EDTA using ethanol as the primary electron donor and carbon source. A series of batch experiments were conducted using biomass extracted from the scrubber solution treatment and regeneration stage of a prototype iron EDTA-based unit process for the absorption of nitric oxide with subsequent biological treatment. Using a linear-sweep voltammetric method for analysis of the ferric EDTA concentration, iron-reducing bacteria were found to behave according to the Monod kinetic model, at initial concentrations up to 2.16 g chemical oxygen demand (COD) as ethanol per liter, with a half-velocity constant of 0.532 g COD as ethanol/L and a maximum specific utilization rate of 0.127 mol/L of ferric ethylenediamine-tetraacetic acid [Fe(III)EDTA]*(g volatile suspended solids [VSS]/L)d(-1). Based on batch analyses, biomass yield and endogenous decay values of iron-reducing bacteria were estimated to be 0.055 g VSS/g COD and 0.017 L/d, respectively. An average of 1.64 times the theoretical (stoichiometric) demand of ethanol was used to complete reduction reactions. Kinetics of the reduction of the nitrosyl adduct of ferrous EDTA are summarized by the following kinetic constants: half-velocity constant (Ks) of 0.39 g COD/L, maximum specific utilization rate (k) of 0.2 mol/L [NO x Fe(II)EDTA(2-)](g VSS/L)d(-1), and inhibition constant (K(I)) of 0.33 g COD/L, as applied to the modified Monod kinetic expression described herein. Based on batch analyses, the biomass yield of nitrosyl-adduct-reducing bacteria was estimated to be 0.259 g VSS/g COD, endogenous decay was experimentally determined to be 0.0569 L/d, and an average of 1.26 times the stoichiometric demand of ethanol was used to complete reduction reactions.

Kinetic of carbonaceous substrate in an upflow anaerobic sludge sludge blanket (UASB) reactor treating 2,4 dichlorophenol (2,4 DCP)

The performance of an upflow anaerobic sludge blanket (UASB) reactor treating 2,4 dichlorophenol (2,4 DCP) was evaluated at different hydraulic retention times (HRTs) using synthetic wastewater in order to obtain the growth substrate (glucose-COD) and 2,4 DCP removal kinetics. Treatment efficiencies of the UASB reactor were investigated at different hydraulic retention times (2–20 h) corresponding to a food to mass ( F/ M) ratio of 1.2–1.92 g-COD g −1 VSS day −1. A total of 65–83% COD removal efficiencies were obtained at HRTs of 2–20 h. In all, 83% and 99% 2,4 DCP removals were achieved at the same HRTs in the UASB reactor. Conventional Monod, Grau Second-order and Modified Stover–Kincannon models were applied to determine the substrate removal kinetics of the UASB reactor. The experimental data obtained from the kinetic models showed that the Monod kinetic model is more appropriate for correlating the substrate removals compared to the other models for the UASB reactor. The maximum specific substrate utilization rate ( k) (mg-COD mg −1 SS day −1), half-velocity concentration ( K s) (mg COD l −1), growth yield coefficient ( Y) (mg mg −1) and bacterial decay coefficient ( b) (day −1) were 0.954 mg-COD mg −1 SS day −1, 560.29 mg-COD l −1, 0.78 mg-SS g −1-COD, 0.093 day −1 in the Conventional Monod kinetic model. The second-order kinetic coefficient ( k 2) was calculated as 0.26 day −1 in the Grau reaction kinetic model. The maximum COD removal rate constant ( U max) and saturation value ( K B) were calculated as 7.502 mg COD l −1 day −1 and 34.56 mg l −1 day −1 in the Modified Stover–Kincannon Model. The ( k)(mg-2,4 DCP mg −1 SS day −1), ( K s) (mg 2,4 DCP l −1), ( Y) (mg SS mg −1 2,4 DCP) and ( k d) (day −1) were 0.0041 mg-2,4 DCP mg −1 SS day −1, 2.06 mg-COD l −1, 0.0017 mg-SS mg −1 2,4 DCP and 3.1×10 −5 day −1 in the Conventional Monod kinetic model for 2,4 DCP degradation. The second-order kinetic coefficient ( k 2) was calculated as 0.30 day −1 in the Grau reaction kinetic model. The maximum 2,4 DCP removal rate constant ( U max) and saturation value ( K B) were calculated as 0.01 mg COD l −1 day −1 and 9.8×10 −3 mg l −1 day −1 in the Modified Stover–Kincannon model.

Exploring temporal variations of oxygen saturation constants of nitrifying bacteria

Activated sludge models (ASM) are generally accepted as state-of-the-art in modeling wastewater treatment plants. In this paper, we assess the temporal variability of an ASM parameter—the oxygen half-saturation constant of autotrophic bacteria ( K O, AUT). A series of respirometric experiments is performed for conventional activated sludge and sludge from a membrane bioreactor. K O values are estimated for both ammonium-oxidizing and nitrite-oxidizing bacteria. For parameter estimation, the Monod kinetic model structure is extended by a sensor model. Still remaining systematic deviations between data and model are considered by a thorough residual analysis: (1) uncertainty estimates of K O are corrected to reflect model structure deficiencies and (2) the inter-experimental cross-correlation of residuals is taken into account to assess temporal changes. We conclude that K O, AUT is a time variable parameter and should be considered accordingly.

Kinetics of biodegradation of p‐xylene and naphthalene and oxygen transfer in a novel airlift immobilized bioreactor

The scope of this study included the biodegradation performance and the rate of oxygen transfer in a pilot-scale immobilized soil bioreactor system (ISBR) of 10-L working volume. The ISBR was inoculated with an acclimatized population of contaminant degrading microorganisms. Immobilization of microorganisms on a non-woven polyester textile developed the active biofilm, thereby obtaining biodegradation rates of 81 mg/L x h and 40 mg/L x h for p-xylene and naphthalene, respectively. Monod kinetic model was found to be suitable to correlate the experimental data obtained during the course of batch and continuous operations. Oxygen uptake and transfer rates were determined during the batch biodegradation process. The dynamic gassing-out method was used to determine the oxygen uptake rate (OUR) and volumetric oxygen mass transfer, K(L) a. The maximum volumetric OUR of 255 mg O(2)/L x h occurred approximately at 720-722 h after inoculation, when the dry weight of biomass concentration was 0.67 g/L.