Use of the ADM1 to investigate the effects of acetoclastic methanogen population dynamics on mesophilic digester stability

2006 ◽  
Vol 54 (4) ◽  
pp. 59-66 ◽  
Author(s):  
A.J. Straub ◽  
A.S.Q. Conklin ◽  
J.F. Ferguson ◽  
H.D. Stensel
Keyword(s):  
Hydrolysis Rate ◽  
Utilization Rate ◽  
Feeding Frequency ◽  
Acetate Production ◽  
First Order ◽  
Acetoclastic Methanogen ◽  
Acetate Utilization ◽  
Methanogen Population ◽  
Dual Pathway ◽  
Rate Functions

The ADM1 was employed to assess the effect of variations in solids hydrolysis and acetoclastic methanogen process characterizations on municipal digester stability relating to excess acetate utilization capacity. First-order single- and dual-pathway hydrolysis rate functions and single and competitive acetoclastic methanogen rate functions were implemented in the ADM1. The acetate capacity number (ACN), defined as the ratio between the maximum acetate utilization rate and the average acetate production rate, was used to index digester instability. Simulations of a single CSTR at steady state indicate a similar ACN can be obtained with a 12-day SRT digester dominated by Methanosarcina sp and a 24-day SRT digester dominated by Methanosaeta sp. An increase in ACN with a decrease in SRT representing Methanosarcina sp. selection was observed for particulate feed loadings from 40 g COD/L to 90 g COD/L. Feeding frequency and dual-pathway hydrolysis were found to have less effect on the ACN than the competitive acetoclastic model structure.

Inhibition kinetics for propionate degradation using propionate-enriched mixed cultures

1998 ◽  
Vol 38 (8-9) ◽  
pp. 443-451 ◽  
Author(s):  
S. H. Hyun ◽  
J. C. Young ◽  
I. S. Kim
Keyword(s):  
Phase I ◽  
Competitive Inhibition ◽  
Gas Production ◽  
Phase Iii ◽  
Utilization Rate ◽  
Inhibition Kinetics ◽  
Wide Range ◽  
Propionate Degradation ◽  
Acetate Utilization ◽  
Velocity Coefficient

To study propionate inhibition kinetics, seed cultures for the experiment were obtained from a propionate-enriched steady-state anaerobic Master Culture Reactor (MCR) operated under a semi-continuous mode for over six months. The MCR received a loading of 1.0 g propionate COD/l-day and was maintained at a temperature of 35±1°C. Tests using serum bottle reactors consisted of four phases. Phase I tests were conducted for measurement of anaerobic gas production as a screening step for a wide range of propionate concentrations. Phase II was a repeat of phase I but with more frequent sampling and detailed analysis of components in the liquid sample using gas chromatography. In phase III, different concentrations of acetate were added along with 1.0 g propionate COD/l to observe acetate inhibition of propionate degradation. Finally in phase IV, different concentrations of propionate were added along with 100 and 200 mg acetate/l to confirm the effect of mutual inhibition. Biokinetic and inhibition coefficients were obtained using models of Monod, Haldane, and Han and Levenspiel through the use of non-linear curve fitting technique. Results showed that the values of kp, maximum propionate utilization rate, and Ksp, half-velocity coefficient for propionate conversion, were 0.257 mg HPr/mg VSS-hr and 200 mg HPr/l, respectively. The values of kA, maximum acetate utilization rate, and KsA, half-velocity coefficient for acetate conversion, were 0.216 mg HAc/mg VSS-hr and 58 mg HAc/l, respectively. The results of phase III and IV tests indicated there was non-competitive inhibition when the acetate concentration in the reactor exceeded 200 mg/l.

In-vitro Kinetic Hydrolysis Study of Metronidazole Derivatives with Carvacrol and Eugenol Using Validated RP-HPLC Method

2020 ◽  
Vol 16 ◽  
Author(s):  
M. Alarjah
Keyword(s):  
Half Life ◽  
Hplc Method ◽  
Hydrolysis Rate ◽  
First Order ◽  
First Order Kinetics ◽  
Rp Hplc ◽  
Pharmacokinetic Properties ◽  
Pseudo First Order ◽  
Kinetic Hydrolysis

Background: Prodrugs principle is widely used to improve the pharmacological and pharmacokinetic properties of some active drugs. Much effort was made to develop metronidazole prodrugs to enhance antibacterial activity and or to improve pharmacokinetic properties of the molecule or to lower the adverse effects of metronidazole. Objective: In this work, the pharmacokinetic properties of some of monoterpenes and eugenol pro metronidazole molecules that were developed earlier were evaluated in-vitro. The kinetic hydrolysis rate constants and half-life time estimation of the new metronidazole derivatives were calculated using the validated RP-HPLC method. Method: Chromatographic analysis was done using Zorbbax Eclipse eXtra Dense Bonding (XDB)-C18 column of dimensions (250 mm, 4.6 mm, 5 μm), at ambient column temperature. The mobile phase was a mixture of sodium dihydrogen phosphate buffer of pH 4.5 and methanol in gradient elution, at 1ml/min flow rate. The method was fully validated according to the International Council for Harmonization (ICH) guidelines. The hydrolysis process carried out in an acidic buffer pH 1.2 and in an alkaline buffer pH 7.4 in a thermostatic bath at 37ºC. Results: The results followed pseudo-first-order kinetics. All metronidazole prodrugs were stable in the acidic pH, while they were hydrolysed in the alkaline buffer within a few hours (6-8 hr). The rate constant and half-life values were calculated, and their values were found to be 0.082- 0.117 hr-1 and 5.9- 8.5 hr., respectively. Conclusion: The developed method was accurate, sensitive, and selective for the prodrugs. For most of the prodrugs, the hydrolysis followed pseudo-first-order kinetics; the method might be utilised to conduct an in-vivo study for the metronidazole derivatives with monoterpenes and eugenol.

scholarly journals Kinetics of Biofilm Detachment

1992 ◽  
Vol 26 (9-11) ◽  
pp. 1995-1998 ◽  
Author(s):  
B. M. Peyton ◽  
W. G. Characklis
Keyword(s):  
Steady State ◽  
Utilization Rate ◽  
Carbon Utilization ◽  
Biofilm Thickness ◽  
First Order ◽  
Detachment Rate ◽  
Biofilm Detachment ◽  
Biofilm Modeling ◽  
Kinetics Of ◽  
Sensitive Variable

In predictive biofilm modeling, the detachment rate coefficient may be the most sensitive variable affecting both the predicted rate and the extent of biofilm accumulation. At steady state the detachment rate must be equal to the net growth rate in the biofilm. In systems where organic carbon is growth-limiting, the substrate carbon utilization rate determines the net biomass production rate and, therefore, the steady state biomass detachment rate. Detachment rates, first order with biofilm thickness, fit the experimental data well, but are not predictive since the coefficients must be determined experimentally.

Denitrifying kinetics and nitrous oxide emission under different copper concentrations

2013 ◽  
Vol 69 (4) ◽  
pp. 746-754 ◽  
Author(s):  
Guangxue Wu ◽  
Xiaofeng Zhai ◽  
Chengai Jiang ◽  
Yuntao Guan
Keyword(s):  
Nitrous Oxide ◽  
Electron Acceptor ◽  
Copper Concentration ◽  
N2o Emission ◽  
Utilization Rate ◽  
Batch Reactors ◽  
Sequencing Batch Reactors ◽  
Batch Experiments ◽  
Acetate Utilization ◽  
Effect Of Copper

Denitrifying activities and nitrous oxide (N2O) emission during denitrification can be affected by copper concentrations. Different denitrifiers were acclimated in sequencing batch reactors with acetate or methanol as the electron donor and nitrate as the electron acceptor. The effect of copper concentrations on the denitrifying activity and N2O emission for the acclimated denitrifiers was examined in batch experiments. Denitrifying activities of the acclimated denitrifiers declined with increasing copper concentrations, and the copper concentration exhibited a higher effect on denitrifiers acclimated with acetate than those acclimated with methanol. Compared with the control without the addition of copper, at the copper concentration of 1 mg/L, the acetate utilization rate reduced by 89% for acetate-acclimated denitrifiers, while the methanol utilization rate only reduced by 15% for methanol-acclimated denitrifiers. Copper also had different effects on N2O emission during denitrification carried out by various types of denitrifiers. For the acetate-acclimated denitrifiers, N2O emission initially increased and then decreased with increasing copper concentrations, while for the methanol-acclimated denitrifiers, N2O emission decreased with increasing copper concentrations.

Important limitations in the modeling of activated sludge: biased calibration of the hydrolysis process

2002 ◽  
Vol 45 (12) ◽  
pp. 23-36 ◽  
Author(s):  
G. Insel ◽  
Ö. Karahan Gül ◽  
D. Orhon ◽  
P.A. Vanrolleghem ◽  
M. Henze
Keyword(s):  
Activated Sludge ◽  
Hydrolysis Rate ◽  
Utilization Rate ◽  
Oxygen Utilization ◽  
Experimental Assessment ◽  
Experimental Database ◽  
Hydrolysis Process ◽  
Biochemical Mechanisms ◽  
Oxygen Utilization Rate ◽  
Activated Sludge Models

The merit of activated sludge models depends on the accuracy and reliability of the information they contain on the wastewater to be treated and the biochemical mechanisms involved. In most advanced calibration studies, respirometry i.e. the measurement of the oxygen utilization rate, (OUR), provides the majority of the required experimental database. However, currently used procedures still involve a number of basic and practical problems. Model evaluation of the OUR data may generate a distorted image of the processes involved. Hydrolysis is the most important, yet the most vulnerable process as far as the experimental assessment of accurate kinetic parameters is concerned. This study intends to provide an overview of major experimental limitations in the modeling of activated sludge, with emphasis on the appropriate experimental design for the assessment of the hydrolysis rate.

Analysis of Gas Utilization Efficiency in Injection Refining Process

2011 ◽  
Vol 391-392 ◽  
pp. 703-708
Author(s):  
Yan Liu ◽  
Ting An Zhang ◽  
Sano Masamichi ◽  
Ji Cheng He
Keyword(s):  
Gas Flow ◽  
Bubble Diameter ◽  
Operating Conditions ◽  
Utilization Efficiency ◽  
Utilization Rate ◽  
Theoretical Formula ◽  
Practical Situation ◽  
First Order ◽  
Physical Conditions ◽  
Gas Utilization

According to practical situation of Mg-based desulphurization, this paper has defined the formula of bubble effectiveness with low ratio of height to diameter, and derived the theoretical formula of the bubble utilization rate relating to gas flow rate, bubble diameter and mass transfer coefficient. When the absorption rate is treated as first order reaction, the theoretical formula is presented which includes physical conditions, equipment conditions and operating conditions. It indirectly reflects the three conditions on the effective of bubble utilization rate. The calculation formula of bubble utilization rate at different sizes and different residence time distribution is derived.

scholarly journals Acetate metabolism in lactating sheep

1982 ◽  
Vol 48 (2) ◽  
pp. 319-328 ◽  
Author(s):  
D. W. Pethick ◽  
D. B. Lindsay
Keyword(s):  
Blood Flow ◽  
Mammary Gland ◽  
Lactate Production ◽  
Utilization Rate ◽  
Acetate Metabolism ◽  
Oxygen Utilization ◽  
Milk Flow ◽  
Lactating Mammary Gland ◽  
Acetate Utilization

1. The metabolism of acetate, glucose and D(−)-3-hydroxybutyrate was studied in lactating and non lactating sheep in vivo. Special consideration was given to the utilization by hind-limb muscle in both groups of sheep and the uptake of nutrients by the lactating mammary gland was also measured.2. The entry of acetate into the circulation (mmol/h per kg body-weight) was similar in all experimental animals at a given arterial concentration of acetate. However, normal lactation was associated with a reduced extraction of acetate by muscle and the 'spared' acetate was comparable with that removed by the udder. Feeding lactating ewes a 700 g concentrate/kg ration tended to prevent this redistribution of acetate utilization.3. The muscle of non-lactating ewes utilized sufficient glucose, when corrected for lactate release, to account for 57% of the oxygen utilization by muscle. In lactation this fell to 32%, largely because of an increased lactate production. D(−)-3-Hydroxybutyrate utilization by muscle accounted for 16–17% of the O2 consumed by the muscle in non-lactating and lactating sheep.4. Lactating mammary gland metabolism in sheep was similar to published values for dairy cows and goals. Thus the extraction (%) of glucose, O2, acetate and D(−)-3-hydroxybutyrate was 25, 28, 62 and 53 respectively. Blood flow was 529 ml/min per kg udder and the ratio blood flow: milk flow was 475. Glucose used by the udder relative to the whole animal utilization rate may be less in sheep than in cows and goats, but the comparable proportion for acetate is as large or larger than in these species.

The chemistry of N,N′-dimethylformamidine. II. Hydrolysis. Kinetically controlled formation of cis-N-methylformamide

1978 ◽  
Vol 56 (11) ◽  
pp. 1463-1469 ◽  
Author(s):  
James D. Halliday ◽  
E. Allan Symons
Keyword(s):  
Aqueous Media ◽  
Hydrolysis Rate ◽  
Strong Base ◽  
First Order ◽  
H Nmr ◽  
Stereoelectronic Control ◽  
Pseudo First Order ◽  
Ph Range ◽  
Hydrolysis Of ◽  
Cis Isomer

The hydrolysis of N,N′-dimethylformamidine (DMFA) has been investigated in acid and alkaline aqueous media by 1H nmr; only a narrow basic pH range could be extensively studied kinetically. The pseudo-first-order kobs rose steadily from pH 11.5 to 13.0 (reaction approximately first order in OH−), then became independent of pH above 13.5 (9.3 × 10−4 s−1 at 10 °C). In contrast to many amidines, DMFA is quite stable in acid solution (estimated value of the pseudo-first-order hydrolysis rate constant is 1.4 × 10−1 s−1 at 10 °C, pH 0.05, from measurements at 100 and 140 °C). This stability is ascribed to the difficulty of eliminating the fairly strong base methylamine from the tetrahedral intermediate in acid solution.N-Methylformamide (NMF), one of the products, is formed initially as the cis isomer. A somewhat slower conversion then occurs to the thermodynamically more stable trans isomer. This unusual result is explained in terms of Deslongchamps and co-workers' theory of stereoelectronic control for the orbital-assisted breakdown of tetrahedral intermediates.

scholarly journals Measurement of the rates of acetyl-CoA hydrolysis and synthesis from acetate in rat hepatocytes and the role of these fluxes in substrate cycling

1990 ◽  
Vol 270 (1) ◽  
pp. 219-225 ◽  
Author(s):  
B Crabtree ◽  
M J Gordon ◽  
S L Christie
Keyword(s):  
Heat Production ◽  
Rat Hepatocytes ◽  
Total Heat ◽  
Acetate Production ◽  
Acetyl Coa ◽  
Acetyl Coa Synthesis ◽  
Acetate Utilization ◽  
Net Flux

1. Acetyl-CoA hydrolysis, acetyl-CoA synthesis from acetate and several related fluxes were measured in rat hepatocytes. 2. In contrast with acetyl-CoA hydrolysis, most of the acetyl-CoA synthesis from acetate occurred in the mitochondria. 3. Acetyl-CoA hydrolysis was not significantly affected by 24 h starvation or (-)-hydroxycitrate. 4. In the cytoplasm there was a net flux of acetyl-CoA to acetate, and substrate cycling between acetate and acetyl-CoA in this compartment was very low, accounting for less than 0.1% of the total heat production by the animal. 5. A larger cycle, involving mitochondrial and cytoplasmic acetate and acetyl-CoA, may operate in fed animals, but would account for only approx 1% of total heat production. 6. It is proposed that the opposing fluxes of mitochondrial acetate utilization and cytoplasmic net acetate production may provide sensitivity, feedback and buffering, even when these fluxes are not linked to form a conventional substrate cycle.

Wastewater COD characterization: biodegradability of physico-chemical fractions

2002 ◽  
Vol 45 (6) ◽  
pp. 89-97 ◽  
Author(s):  
P. Ginestet ◽  
A. Maisonnier ◽  
M. Spérandio
Keyword(s):  
Hydrolysis Rate ◽  
Affinity Constant ◽  
Characterization Methods ◽  
First Order ◽  
Physico Chemical ◽  
Wastewater Samples ◽  
Solids Analysis ◽  
Activated Sludge Processes ◽  
Limited Surface

Physico-chemical and biological characterization methods were applied to wastewater samples originating from 7 French WWTPs. The settleable fraction (S), unsettleable-coagulable fraction (US-C) and unsettleable-uncoagulable fraction (US-UC) were separated. Special emphasis was put on the determination of hydrolysis kinetics associated with coagulable- and settleable-fractions in order to model their behaviour in activated sludge processes, as both these fractions are influenced by the SRT. The “soluble” fraction (i.e. US-UC) was composed of readily biodegradable COD (2 to 27%), readily hydrolysable COD (37 to 90%) and inerts (2 to 47%). The “colloidal” fraction (i.e. US-C) was composed of heterotrophic biomass (9 to 24%) and readily hydrolysable COD (6 to 82%), with the rest being inerts or very slowly biodegradable COD (0 to 70%). The “particulate” fraction (i.e. settleable) was composed of biomass (14 ± 6%), readily hydrolysable COD (21 ± 14%), slowly hydrolysable COD (about 45–50%) and 15 to 20% which can be considered as inert matter (XI). “Readily hydrolysable COD” was correctly modeled by a global first-order reaction. First-order constants (KH) were 9 ± 2 d−1 for raw-wastewater, 12 ± 3 d−1 for primary settled-wastewater and 16 ± 5 d−1 for coagulated-wastewater. “Slowly hydrolysable COD” was correctly modeled by a limited surface reaction. Concerning this fraction, the specific hydrolysis rate (kH) ranged from 0.25 to 1.05 d−1, and the affinity constant (KX) ranged from 0.33 to 0.95 gCOD/gCOD based on settleable solids analysis.

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