Substrate Removal Kinetics Research Articles

Substrate removal evaluation of granular anammox process in a pilot-scale upflow anaerobic sludge blanket reactor

Process kinetics can present necessary information for granular anammox process but little study focused on the nitrogen removal kinetics of pilot-scale anammox granular process is available. In this study, the substrate removal kinetics in a pilot-scale anammox granular reactor were investigated by inoculating anammox granules in to an UASB reactor, which was then operated at different hydraulic retention times and nitrogen loading rates. The reactor showed good tolerance to substrate concentration shock while it was affected significantly by hydraulic shock. Molecular techniques confirmed the existence of at least four well-known anammox species and anammox cells accounted for 93.7% of total cells. Evaluation of the nitrogen removal kinetics indicated that the Grau second-order substrate removal model and the modified Stover–Kincannon model turned out to be appropriate to describe nitrogen removal of anammox granules, rather than the first-order substrate removal model, the Monod model, and the Contois model. Model evaluation was then carried out via assessing the linearity between the experimental data and predicted values, which proved the applicability of the two models. The information derived from the current study could guide and optimize the design of full-scale anammox granular reactors.

Kinetic analysis of phenol, thiocyanate and ammonia-nitrogen removals in an anaerobic–anoxic–aerobic moving bed bioreactor system

A simulated wastewater containing phenol (2500 mg/L), thiocyanate and ammonia-nitrogen (500 mg/L) was treated in an anaerobic (R1)–anoxic (R2)–aerobic (R3) moving bed biofilm reactor system at different hydraulic retention time (HRT) intervals (total HRT 3–8 days, R1: 1.5–4 days; R2: 0.75–2 days and R3: 0.75–2 days) and feed thiocyanate (SCN −) concentrations (110–600 mg/L) to determine substrate removal kinetics. In R1, phenol and COD reduction and specific methanogenic activity were inhibited due to the increase of SCN − in feed. Bhatia et al. model having inbuilt provision of process inhibition described the kinetics of COD and phenol utilization with maximum utilization rates of 0.398 day −1 and 0.486 day −1, respectively. In R2 and R3 modified Stover–Kincannon model was suitable to describe substrate utilization. In R2 respective maximum SCN −, phenol, COD and NO 3 −-N utilization rates were 0.23, 5.28, 37.7 and 11.82 g/L day, respectively. In aerobic reactor R3, COD, SCN − and NH 4 +-N removal rates were, respectively, 10.53, 1.89, and 2.17 g/L day. The minimum total HRT of three-stage system was recommended as 4 days.

Effects of Cr(VI) on the performance and kinetics of the activated sludge process

The substrates removal performance, removal kinetics and the electron transport system (ETS) of sludge were investigated by sequencing batch reactors (SBR) and batch assays, respectively. Compared to the control system, significant decreases were observed in substrate removal efficiency with the Cr(VI)-feeding concentration up to 5 mg L(-1) in SBR system. And the recovery for NH4+-N removal were more difficult than that of COD after the termination of Cr(VI)-feeding. Significant inhibitory effects of Cr(VI) on the ETS activity and substrate removal kinetics were observed in the batch assays. The inhibitory effects of Cr(VI) would be overestimated on COD removal and underestimated on NH4+-N removal by the short-term batch assay as compared to the long-term operations. Additionally, significant correlations between the ETS activity and the inhibitory rates of Cr(VI) on substrate removal indicated the ETS activity can provide effective predictions on the potential performance of substrate removal in activated sludge.

The kinetics of nitrogen removal and biogas production in an anammox non-woven membrane reactor

The anammox non-woven membrane reactor (ANMR) is a novel reactor configuration to culture the slowly growing anammox bacteria. Different mathematical models were used to study the process kinetics of the nitrogen removal in the ANMR. The kinetics of nitrogen gas production of anammox process was first evaluated in this paper. For substrate removal kinetics, the modified Stover-Kincannon model and the Grau second-order model were more applicable to the ANMR than the first-order model and the Monod model. For nitrogen gas production kinetics, the Van der Meer and Heertjes model was more appropriate than the modified Stover-Kincannon model. Model evaluation was carried out by comparing experimental data with predicted values calculated from suitable models. Both model kinetics study and model testing showed that the Grau second-order model and the Van der Meer and Heertjes model seemed to be the best models to describe the nitrogen removal and nitrogen gas production in the ANMR, respectively.

Dissolved oxygen as a key parameter to aerobic granule formation

Much research has asserted that high shear forces are necessary for the formation of aerobic granular sludge in Sequencing Batch Reactors (SBRs). In order to distinguish the role of shear and dissolved oxygen on granule formation, two separate experiments were conducted with three bench-scale SBRs. In the first experiment, an SBR was operated with five sequentially decreasing superficial upflow gas velocities ranging from 1.2 to 0.4 cm s(-1). When less than 1 cm s(-1) shear was applied to the reactor, aerobic granules disintegrated into flocs, with corresponding increases in SVI and effluent suspended solids. However, the dissolved oxygen also decreased from 8 mg L(-1) to 5 mg L(-1), affecting the Feast/Famine regime in the SBR and the substrate removal kinetics. A second experiment operated two SBRs with an identical shear force of 1.2 cm s(-1), but two dissolved oxygen concentrations. Even when supplied a high shear force, aerobic granules could not form at a dissolved oxygen less than 5 mg L(-1), with a Static Fill. These results indicate that the substrate removal kinetics and dissolved oxygen are more significant to granule formation than shear force.

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.

The removal of C.I. Basic Red 46 in a mixed methanogenic anaerobic culture

The removal of C.I. Basic Red 46 (BR 46) was investigated with anaerobic mixed culture using glucose (3000 mg l −1 COD) as carbon source and electron donor. Zero-, first- and second-order reaction kinetics were used to find out the suitable substrate removal and decolorization kinetics. The substrate removal (COD) process is suitable for first-order reaction kinetic among the kinetic models studied. Increases in dye concentrations from 0 to 1000 mg l −1 decrease the degradation rate constant ( k 1) values from 0.0083 to 0.0032 h −1 in batch experiments carried out with BR 46. Decolorization process approximates to first-order kinetic at 50, 100 and 250 mg l −1 of BR 46, and to zero-order kinetic at 500, 750, 1000 mg l −1 of BR 46 concentration. Substrate and color removal rates (mg l −1 h −1) were found to be 8.07, 7.78, 7.64, 7.23, 6.39, 5.98, 5.28 and 0.66, 1.37, 3.48, 4.95, 6.30, 5.99, respectively, in all serum bottles throughout incubation period.

Removal of Maxilon Yellow GL in a mixed methanogenic anaerobic culture

Degradation of dye Maxilon Yellow GL (MY GL) (Basic Yellow 45) was investigated with anaerobic mixed culture using glucose (3000 mg l −1 COD) as carbon source and electron donor throughout batch experiments. Zero-, first- and second-order reaction kinetics were used to find out the suitable substrate removal and decolorization kinetics. The substrate removal (COD) process is suitable for second-order reaction kinetics among the kinetic models studied. Decolorization process also approximates to second-order kinetics between 50 and 1000 mg l −1 of MY GL concentration. Substrate and color removal rates (mg l −1 h −1) were found to be 6.38, 5.98, 4.6, 4.16, 3.64, 2.86, 2.34 and 0.075, 0.0149, 0.0265, 0.0303, 0.0426, 0.053, respectively, in all serum bottles throughout the incubation period. Color removal efficiencies decreased as the influent dye concentration increased. The highest removal efficiency (80%) was obtained with 50 and 100 mg l −1 of MY GL dye concentrations. However, the lowest removal efficiency (28%) was found with a 1000 mg l −1 of MY GL dye concentration. Complete dye reduction was not found for this basic dye. The results indicate that anaerobic mixed culture can decolorize low concentration of this basic dye.

Substrate removal kinetics in an upflow anaerobic sludge blanket reactor decolorising simulated textile wastewater

A simulated wastewater containing sizing agents, azo dyes, salts and other additives was treated using a lab-scale upflow anaerobic sludge blanket (UASB) reactor at different hydraulic retention times (HRT) in order to obtain the substrate removal kinetic of the reactor through decolorization of dyes. COD removal efficiencies decreased from 80 to 29.5% when the HRT decreased from 100 to 6 h. The colour removal efficiencies were between 90 and 95% for HRTs of 100 and 6. Monod, Contois, Grau second order, modified Stover-Kincannon, and first order kinetic models were applied to determine the substrate removal kinetic of UASB reactor. The experimental data obtained from the steady-state conditions showed that Grau second order, modified Stover-Kincannon and Contois substrate removal kinetic models were suitable than the other applied models for predicting the performance of lab-scale UASB reactor treating the azo dyes.

Study and optimisation of the anaerobic acidogenic fermentation of two-phase olive pomace

A study of the effect of hydraulic retention time (HRT) on the anaerobic acidogenic fermentation of two-phase olive pomace (TPOP) was carried out at laboratory-scale and mesophilic temperature (35 °C). The experimental results obtained demonstrated that the optimum value of HRT for the acidogenic fermentation process was 12 days, for which a maximum production of total volatile fatty acids (TVFA) and, specifically, of acetic and butyric acids were obtained. It was found that a multicomponent substrate removal kinetics model adjusted very well to the experimental data obtained. A second-order kinetic model was used for the degradation of non-soluble COD whilst a first-order model was appropriate for studying both the total and soluble COD reduction. The values of the kinetic constants obtained were: 0.29, 0.29 and 0.12 g COD/g VSS per day for non-soluble, total and soluble COD degradation, respectively. A similar model was used to determine the kinetic constants for product formation, obtaining values of: 0.0007, 0.0024, 0.0022, 0.0031 and 0.0022 g COD per litre per day for acetic, propionic, butyric, valeric+caproic and TVFA, respectively. The order of the reaction of volatile fatty acids production was determined in each case, the values being in the range of 1.7–2.4, values very close to second-order. The value of the apparent kinetic constant was minimum for acetic acid formation (0.0009 g COD per litre per day) and maximum for valeric+caproic acids (0.0031 g COD per litre per day) because in the hydrolysis process of complex organic matter, long chain fatty acids appear first and faster than acetic acid. The kinetic model used was validated by comparing the theoretical and experimental values of the product formation rate ( R P). The small deviations obtained (in the range between 1.0 and 20.8%) suggest that the proposed model predicts the kinetics of volatile acids production accurately.

Improvement of Sludge Settleability in Activated Sludge Plants Treating Effluent from Pulp and Paper Industries

The main objective of many activated sludge plants treating wastewater from the pulp and paper industry is to remove COD only. These plants are often designed as high-load aerobic systems without any microbial selector system. As a consequence the sludge settling properties are normally poor due to fast growing filamentous microorganisms, which severely reduce the treatment capacity and the effluent quality. Implementation of selectors, in which the substrate concentration and the metabolic pathways can be manipulated, has in many cases reduced the bulking sludge problems in activated sludge systems. An example of a successful upgrading of a Danish pulp industry wastewater treatment plant with an anoxic selector is presented. the use of a novel technique to investigate the in situ physiology of filamentous microorganisms is discussed. It is concluded that a successful application of selectors relies on detailed knowledge about: a) physiology and substrate requirement of the filamentous microorganisms, b) wastewater composition and c) substrate removal kinetics in the selector system.

Improvement of sludge settleability in activated sludge plants treating effluent from pulp and paper industries

The main objective of many activated sludge plants treating wastewater from the pulp and paper industry is to remove COD only. These plants are often designed as high-load aerobic systems without any microbial selector system. As a consequence the sludge settling properties are normally poor due to fast growing filamentous microorganisms, which severely reduce the treatment capacity and the effluent quality. Implementation of selectors, in which the substrate concentration and the metabolic pathways can be manipulated, has in many cases reduced the bulking sludge problems in activated sludge systems. An example of a successful upgrading of a Danish pulp industry wastewater treatment plant with an anoxic selector is presented. the use of a novel technique to investigate the in situ physiology of filamentous microorganisms is discussed. It is concluded that a successful application of selectors relies on detailed knowledge about: a) physiology and substrate requirement of the filamentous microorganisms, b) wastewater composition and c) substrate removal kinetics in the selector system.

Kinetic analysis of an anaerobic filter treating soybean wastewater

An investigation into the kinetics of the treatment of soybean wastewater in an anaerobic filter is described. The substrate loading removal rate was compared with predictions from a modified Stover–Kincannon model, the Monod model and a regression relationship. The modified Stover–Kincannon model produced the best fit with the experimental results. The modified Stover–Kincannon model could also be used to determine the reactor volume required to decrease a set influent organic concentration to a given effluent concentration, or to determine the effluent substrate concentration for a given volume of an anaerobic filter and influent organic concentration. The overall reaction order in the anaerobic filter treating soybean wastewater appeared to be close to half order. The methane production kinetics could be described by a similar relationship that used to describe the organic substrate removal kinetics of the anaerobic filter treating soybean wastewater. The kinetic relationships derived from the lab-scale experiment provided good estimates of the performance of pilot- and full-scale anaerobic filters packed with the same media and treating the same wastewater in terms of the effluent chemical oxygen demand (COD) concentrations and the specific methane production rates.

Integration of performance, molecular biology and modeling to describe the activated sludge process

To study process performance and population dynamics in activated sludge, a pilot-scale Membrane Bioreactor (MBR) was installed in a municipal wastewater treatment plant (Aubergenville, France). Since no solids losses occur in the MBR effluent, the sludge residence time (SRT) can be: i) easily controlled by means of the sludge withdrawal, and ii) dissociated from the hydraulic residence time (HRT). A complete characterization of this activated sludge system was performed at three sludge ages (5, 10 and 20 days). Raw and treated wastewater quality, as well as sludge concentration, was analyzed, nucleic probe analysis was performed to determine the heterotrophic and nitrifier populations, and the results were compared to the output from a multispecies model that integrates substrate removal kinetics and soluble microbial products (SMP) production/consumption. This paper presents an integrated analysis of the activated sludge process based on chemical, molecular biology, and mathematical tools. The model was able to describe the MBR system with a high degree of accuracy, in terms of COD removal and nitrification, as well as sludge production and population dynamics through the ratio of active nitrifiers/bacteria. Both steady-state and transient conditions could be described accurately by the model, except for technical problems or sudden variations in the wastewater composition.

Integration of performance, molecular biology and modeling to describe the activated sludge process

To study process performance and population dynamics in activated sludge, a pilot-scale Membrane Bioreactor (MBR) was installed in a municipal wastewater treatment plant (Aubergenville, France). Since no solids losses occur in the MBR effluent, the sludge residence time (SRT) can be: i) easily controlled by means of the sludge withdrawal, and ii) dissociated from the hydraulic residence time (HRT). A complete characterization of this activated sludge system was performed at three sludge ages (5, 10 and 20 days). Raw and treated wastewater quality, as well as sludge concentration, was analyzed, nucleic probe analysts was performed to determine the heterotrophic and nitrifier populations, and the results were compared to the output from a multispecies model that integrates substrate removal kinetics and soluble microbial products (SMP) production/consumption. This paper presents an integrated analysis of the activated sludge process based on chemical, molecular biology, and mathematical tools. The model was able to describe the MBR system with a high degree of accuracy, in terms of COD removal and nitrification, as well as sludge production and population dynamics through the ratio of active nitrifters/bacteria. Both steady-state and transient conditions could be described accurately by the model, except for technical problems or sudden variations in the wastewater composition.

Anaerobic treatment of olive mill effluents

The anaerobic treatability of olive mill effluent was investigated using a laboratory scale upflow anaerobic sludge blanket reactor (UASBR) operated for about six months. The effects of various operating conditions including pH, feed strength and hydraulic retention time on the performance of the anaerobic treatment process were determined. In the first part of this study, the reactor was operated with feed COD concentrations from 5000 to 19,000 mg/l and a retention time of 1 day, giving organic loading rates from 5 to 18 kg COD/m3d. Soluble COD removal was around 75% under these conditions. In the second part of the study, feed CODs were varied from 15,000 to 22,600 mg/l while retention times ranged from 0.83 to 2 days; soluble COD removal was around 70%. A methane conversion rate of 0.35 m3 per kg COD removed was achieved during the study. The average volatile solids (VS) concentration in the reactor had increased from 12.75 g l−1 to 60 g l−1 by the end of the study. Sludge volume index (SVI) determinations performed to evaluate the settling characteristics of the anaerobic sludge in the reactor indicated excellent settleability with SVI values of generally less than 20 ml g−1. Sludge granules ranging from 3 to 8 mm in diameter were produced in the reactor. The second order substrate removal kinetics was applied by assuming that hydraulic conditions in the UASBR are approximately completely mixed and the model fitted well to the steady state operating results.

Anaerobic treatment of olive mill effluents

The anaerobic treatability of olive mill effluent was investigated using a laboratory scale upflow anaerobic sludge blanket reactor (UASBR) operated for about six months. The effects of various operating conditions including pH, feed strength and hydraulic retention time on the performance of the anaerobic treatment process were determined. In the first part of this study, the reactor was operated with feed COD concentrations from 5000 to 19,000 mg/l and a retention time of 1 day, giving organic loading rates from 5 to 18 kg COD/m 3 d. Soluble COD removal was around 75% under these conditions. In the second part of the study, feed CODs were varied from 15,000 to 22,600 mg/l while retention times ranged from 0.83 to 2 days; soluble COD removal was around 70%. A methane conversion rate of 0.35 m 3 per kg COD removed was achieved during the study. The average volatile solids (VS) concentration in the reactor had increased from 12.75 g l −1 to 60 g l −1 by the end of the study. Sludge volume index (SVI) determinations performed to evaluate the settling characteristics of the anaerobic sludge in the reactor indicated excellent settleability with SVI values of generally less than 20 ml g −1 . Sludge granules ranging from 3 to 8 mm in diameter were produced in the reactor. The second order substrate removal kinetics was applied by assuming that hydraulic conditions in the UASBR are approximately completely mixed and the model fitted well to the steady state operating results.

Competition in biofilms

Competitions in biofilms for substrate and space have been studied by using a microelectrode technique and a microslicing technique. Three different kinds of biofilms, cultured by laboratory-scale rotating drum biofilm reactors (RDBR) with synthetic wastewater, have been used as test materials. Oxygen, ammonium-nitrogen, nitrate-nitrogen, and pH concentration profiles in the biofilms were measured using microelectrodes. Experimental results showed that: 1) an increase of organic loading rate would result in a decrease of DO concentration in the biofilm. However, after the organic loading rate exceeded a certain value, the oxygen profiles within the biofilm did not change any more; 2) Heterotrophs competed for oxygen with nitrifiers, which resulted in the inhibition of nitrification because of the shortage of oxygen. Glucose itself, however, did not inhibit the nitrification processes; and 3) The competition for substrate in biofilms resulted in a stratified biofilm structure. Experiments showed that competition in biofilms resulted in non-uniform spatial distributions of bacterial populations and metabolically active bacteria. The spatial distributions of biotic and abiotic components in turn affected the substrate transfer and substrate competition within the biofilm. Traditional biofilm modelling will fail in many cases if they are based on substrate removal kinetics and uniform distributions of biofilm properties.

Macro‐scale modelling of substrate removal kinetics in multicomponent fixed‐film systems

AbstractDesign of aerobic fixed‐film systems is generally performed using a traditional chemical reactor theory which accounts for changes in both substrate and biomass concentration. As most of these systems do not behave as ideal reactors, the theoretical evidence clearly shows that the variation and impact of biomass cannot be accounted for by a single reactor concept. Refinements reported in the literature concerning the fate of soluble substrate are modified in this study to also include the variation of biomass viability for different substrate concentration along the aerobic reactor. Evaluations show that a multi‐stage modelling biofilm performance is likely to be a much more reliable predictive tool for removal efficiencies.

Micro‐scale modelling of substrate removal kinetics in multicomponent fixed‐film systems

AbstractModelling of fixed‐film reactors, as for suspended growth systems has to account for all the major components and biochemical processes responsible for the removal of substrate. Traditionally fixed‐film reactors are viewed as two‐component (substrate/biomass) systems interacting with the governing effect of molecular diffusion. Recent developments however have shown the importance of viability and product formation in the modelling of biological systems. This paper emphasizes these two new parameters and evaluates the kinetic relationships between the bulk substrate concentration and biofilm composition as it affects substrate removal and residual product formation.