Biodegradation rates of aromatic contaminants in biofilm reactors

This study has shown that microorganisms can adapt to degrade mixtures of aromatic pollutants at relatively high rates in the μg/l concentration range. The biodegradation rates of the following compounds were investigated in biofilm systems: aromatic hydrocarbons, phenol, methylphenols, chlorophenols, nitrophenol, chlorobenzenes and aromatic nitrogen-, sulphur- or oxygen-containing heterocyclic compounds (NSO-compounds). Furthermore, a comparison with degradation rates observed for easily degradable organics is also presented. At concentrations below 20-100 μg/l the degradation of the aromatic compounds was typically controlled by first order kinetics. The first-order surface removal rate constants were surprisingly similar, ranging from 2 to 4 m/d. It appears that NSO-compounds inhibit the degradation of aromatic hydrocarbons, even at very low concentrations of NSO-compounds. Under nitrate-reducing conditions, toluene was easily biodegraded. The xylenes and ethylbenzene were degraded cometabolically if toluene was used as a primary carbon source; their removal was influenced by competitive inhibition with toluene. These interaction phenomena are discussed in this paper and a kinetic model taking into account cometabolism and competitive inhibition is proposed.

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The Kinetics of Clearance from the Circulation of Man of Heparin and a Semi-Synthetic Heparin Analogue

10.1055/s-0039-1680541 ◽

1977 ◽

Author(s):

D. A. Lane ◽

R. Michalski ◽

V. V. Kakkar

Keyword(s):

High Specificity ◽

Antithrombotic Agent ◽

First Order ◽

First Order Kinetics ◽

Zero Order Kinetics ◽

Low Concentrations ◽

Equal Dose ◽

Rapid Clearance ◽

The Difference ◽

High Concentrations

A study has been made of a low molecular weight semi-synthetic heparin analogue, (SSHA) that may be clinically useful as an antithrombotic agent because of itsreported high specificity for potentiating antithrombin III activity. The clearance from the circulation of both heparin and the analogue has been studied in man following intravenous injection. Heparin obeyed almost zero order kinetics when assayed using a specific anti-Xa assay and first order kinetics when measured with KCCT. At high concentrations the heparin analogue was cleared with first order kinetics when assayed both with the anti-Xa assay and with KCCT. At low concentrations the analogue produced between one half and two-thirds of the anti-Xa activity of an equal dose of heparin, producing only a small prolongation of KCCT. With increasing dose, the more specific anti-Xa potentiating effect of SSHA decreased in part because of the difference in kinetic behaviour between heparin and SSHAbut largely because of a flattening of its anti-Xa dose response curve. Because of the initial more rapid clearance of higher doses of heparin from plasma when it is measured by the KCCT, these results suggest that the use of KCCT can cause a small underestimate of circulating heparin anti-thrombotic activity.

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Iron-transport characteristics of vesicles of brush-border and basolateral plasma membrane from the rat enterocyte

Biochemical Journal ◽

10.1042/bj1640289 ◽

1977 ◽

Vol 164 (2) ◽

pp. 289-294 ◽

Cited By ~ 36

Author(s):

E J Eastham ◽

J I Bell ◽

A P Douglas

Keyword(s):

Small Intestine ◽

Plasma Membrane ◽

Brush Border ◽

Membrane Vesicles ◽

Enzyme Assays ◽

Facilitated Diffusion ◽

First Order ◽

First Order Kinetics ◽

Low Concentrations ◽

Basolateral Plasma Membrane

Vesicles of brush-border and basolateral plasma membrane were prepared from enterocytes of the rat small intestine. The separateness of these two varieties of plasma membrane was confirmed by appropriate enzyme assays. The uptake of Fe2+ by these membrane vesicles was studied, and the results suggest differences between the two types of membrane in both the amount of Fe2+ taken up and in the rate of uptake. At low (up to 3 micrometer) concentrations of Fe2+, uptake by both membrane types showed evidence of saturation and could be blocked with the thiol inactivator N-ethylmaleimide. The studies suggest that Fe2+ is taken into an osmotically active space by a process of facilitated diffusion at low concentrations, but that at higher concentrations the process appeared to obey first-order kinetics. The data provide further evidence for the existence of functional polarity in the epithelial cell of the small intestine.

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Composition of Soil Microbial Communities Enriched on a Mixture of Aromatic Hydrocarbons

Applied and Environmental Microbiology ◽

10.1128/aem.66.12.5282-5289.2000 ◽

2000 ◽

Vol 66 (12) ◽

pp. 5282-5289 ◽

Cited By ~ 74

Author(s):

E. Anne Greene ◽

Jason G. Kay ◽

Karim Jaber ◽

Les G. Stehmeier ◽

Gerrit Voordouw

Keyword(s):

Aromatic Hydrocarbons ◽

Contaminated Soils ◽

Soil Microbial Communities ◽

Time Dependent ◽

Community Members ◽

First Order ◽

Soil Microbial ◽

Benzene Degradation ◽

First Order Kinetics ◽

Genomic Dnas

ABSTRACT Soil contaminated with C5+, which contained benzene (45%, wt/wt), dicyclopentadiene (DCPD) plus cyclopentadiene (together 20%), toluene (6%), styrene (3%), xylenes (2%), naphthalene (2%), and smaller quantities of other compounds, served as the source for isolation of 55 genomically distinct bacteria (standards). Use of benzene as a substrate by these bacteria was most widespread (31 of 44 standards tested), followed by toluene (23 of 44), xylenes (14 of 44), styrene (10 of 44), and naphthalene (10 of 44). Master filters containing denatured genomic DNAs of all 55 standards were used to analyze the community compositions of C5+ enrichment cultures by reverse sample genome probing (RSGP). The communities enriched from three contaminated soils were similar to those enriched from three uncontaminated soils from the same site. The compositions of these communities were time dependent and showed a succession of Pseudomonas andRhodococcus spp. before convergence on a composition dominated by Alcaligenes spp. The dominant community members detected by RSGP were capable of benzene degradation at all stages of succession. The enrichments effectively degraded all C5+ components except DCPD. Overall, degradation of individual C5+ hydrocarbons followed first-order kinetics, with the highest rates of removal for benzene.

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Hepatic uptake and metabolism of galactose can be quantified in vivo by 2-[18F]fluoro-2-deoxygalactose positron emission tomography

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00004.2008 ◽

2008 ◽

Vol 295 (1) ◽

pp. G27-G36 ◽

Cited By ~ 17

Author(s):

Michael Sørensen ◽

Ole Lajord Munk ◽

Frank Viborg Mortensen ◽

Aage Kristian Olsen ◽

Dirk Bender ◽

...

Keyword(s):

Removal Rate ◽

Hepatic Uptake ◽

Metabolic Clearance ◽

Blood Concentrations ◽

First Order ◽

First Order Kinetics ◽

Significant Difference ◽

Saturation Kinetics ◽

Uptake And Metabolism

Metabolism of galactose is a specialized liver function. The purpose of this PET study was to use the galactose analog 2-[18F]fluoro-2-deoxygalactose (FDGal) to investigate hepatic uptake and metabolism of galactose in vivo. FDGal kinetics was studied in 10 anesthetized pigs at blood concentrations of nonradioactive galactose yielding approximately first-order kinetics (tracer only; n = 4), intermediate kinetics (0.5–0.6 mmol galactose/l blood; n = 2), and near-saturation kinetics (>3 mmol galactose/l blood; n = 4). All animals underwent liver C15O PET (blood volume) and FDGal PET (galactose kinetics) with arterial and portal venous blood sampling. Flow rates in the hepatic artery and the portal vein were measured by ultrasound transit-time flowmeters. The hepatic uptake and net metabolic clearance of FDGal were quantified by nonlinear and linear regression analyses. The initial extraction fraction of FDGal from blood-to-hepatocyte was unity in all pigs. Hepatic net metabolic clearance of FDGal, KFDGal, was 332–481 ml blood·min−1·l−1 tissue in experiments with approximately first-order kinetics and 15.2–21.8 ml blood·min−1·l−1 tissue in experiments with near-saturation kinetics. Maximal hepatic removal rates of galactose were on average 600 μmol·min−1·l−1 tissue (range 412–702), which was in agreement with other studies. There was no significant difference between KFDGal calculated with use of the dual tracer input (KdualFDGal) or the single arterial input (KarterialFDGal). In conclusion, hepatic galactose kinetics can be quantified with the galactose analog FDGal. At near-saturated kinetics, the maximal hepatic removal rate of galactose can be calculated from the net metabolic clearance of FDGal and the blood concentration of galactose.

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Efficient degradation of naproxen by persulfate activated with zero-valent iron: performance, kinetic and degradation pathways

Water Science & Technology ◽

10.2166/wst.2020.263 ◽

2020 ◽

Vol 81 (10) ◽

pp. 2078-2091

Author(s):

Shuyu Dong ◽

Xiaoxue Zhai ◽

Ruobing Pi ◽

Jinbao Wei ◽

Yunpeng Wang ◽

...

Keyword(s):

Aqueous Solution ◽

Hydroxyl Radical ◽

Rate Constants ◽

Zero Valent Iron ◽

Degradation Pathways ◽

First Order ◽

First Order Kinetics ◽

Degradation Rates ◽

Initial Ph ◽

Pseudo First Order

Abstract Degradation of naproxen (NAP) by persulfate (PS) activated with zero-valent iron (ZVI) was investigated in our study. The NAP in aqueous solution was degraded effectively by the ZVI/PS system and the degradation exhibited a pseudo-first-order kinetics pattern. Both sulfate radical (SO4•−) and hydroxyl radical (HO•) participate in the NAP degradation. The second-order rate constants for NAP reacting with SO4•− and HO• were (5.64 ± 0.73) × 109 M−1 s−1 and (9.05 ± 0.51) × 109 M−1 s−1, respectively. Influence of key parameters (initial pH, PS dosage, ZVI dosage, and NAP dosage) on NAP degradation were evaluated systematically. Based on the detected intermediates, the pathways of NAP degradation in ZVI/PS system was proposed. It was found that the presence of ammonia accelerated the corrosion of ZVI and thus promoted the release of Fe2+, which induced the increased generation of sulfate radicals from PS and promoted the degradation of NAP. Compared to its counterpart without ammonia, the degradation rates of NAP by ZVI/PS were increased to 3.6–17.5 folds and 1.2–2.2 folds under pH 7 and pH 9, respectively.

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Modeling the Effect of Plants and Peat on Evapotranspiration in Constructed Wetlands

International Journal of Chemical Engineering ◽

10.1155/2010/412734 ◽

2010 ◽

Vol 2010 ◽

pp. 1-6 ◽

Cited By ~ 9

Author(s):

Florent Chazarenc ◽

Simon Naylor ◽

Yves Comeau ◽

Gérard Merlin ◽

Jacques Brisson

Keyword(s):

Phragmites Australis ◽

Constructed Wetlands ◽

Typha Latifolia ◽

Growth Conditions ◽

First Order ◽

First Order Kinetics ◽

Hydraulic Behaviour ◽

Degradation Rates ◽

Wide Range ◽

Main Effect

Evapotranspiration (ET) in constructed wetlands (CWs) represents a major factor affecting hydrodynamics and treatment performances. The presence of high ET was shown to improve global treatment performances, however ET is affected by a wide range of parameters including plant development and CWs age. Our study aimed at modelling the effect of plants and peat on ET in CWs; since we hypothesized peat could behave like the presence of accumulated organic matter in old CWs. Treatment performances, hydraulic behaviour, and ET rates were measured in eight 1 m2CWs mesocosm (1 unplanted, 1 unplanted with peat, 2 planted withPhragmites australis, 2 planted withTypha latifoliaand 2 planted withPhragmites australiswith peat). Two models were built using first order kinetics to simulate COD and TKN removal with ET as an input. The effect of peat was positive on ET and was related to the better growth conditions it offered to macrophytes. Removal efficiency in pilot units with larger ET was higher for TKN. On average, results show for COD ak20value of 0.88d-1and 0.36d-1for TKN. We hypothesized that the main effect of ET was to concentrate effluent, thus enhancing degradation rates.

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Concepts and Models for Biofilm Reactor Performance

Water Science & Technology ◽

10.2166/wst.1990.0145 ◽

1990 ◽

Vol 22 (1-2) ◽

pp. 171-192 ◽

Cited By ~ 47

Author(s):

E. Arvin ◽

P. Harremoës

Keyword(s):

Simulation Models ◽

Biofilm Reactor ◽

Reactor Performance ◽

Design Procedures ◽

First Order ◽

Biofilm Reactors ◽

The Past ◽

First Order Kinetics ◽

Simple Simulation ◽

Waste Characteristics

This paper reviews the state of knowledge of the basic mechanisms governing transformation of pollutants and the present approaches with which to predict the performance of biofilm reactors. The design of biofilm reactors is based mainly on empirical loading criteria or empirical design formulae. Introduction of more stringent effluent requirements, new types of biofilm reactors, as well as application of biofilm reactors to more untraditional types of waste materials, calls for new design procedures with higher degrees of confidence. Most new attempts to model biofilm reactors are based on fundamental principles for mass transport to and through biofilms coupled with kinetic expressions for pollutant transformations in the biofilms. A simple simulation model based on half order kinetics is able to describe the removal of soluble substrates, mineralisation of organic matter, nitrification and denitrification. A simple first order kinetics is able to predict degradation of some xenobiotics. Advanced simulation models appearing in the past few years show a strong promise for detailed analysis of the effect of variation in influent waste characteristics, population dynamics, reactor configuration, etc. However, none of the models are able to predict properly the removal of particulate matter and mixtures of several groups of industrial organic chemicals. Again, insight in the basic removal mechanisms is required.

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Isolation, screening, and crude oil degradation characteristics of hydrocarbons-degrading bacteria for treatment of oily wastewater

Water Science & Technology ◽

10.2166/wst.2019.025 ◽

2018 ◽

Vol 78 (12) ◽

pp. 2626-2638 ◽

Cited By ~ 5

Author(s):

Xiumei Tian ◽

Xiaoli Wang ◽

Shitao Peng ◽

Zhi Wang ◽

Ran Zhou ◽

...

Keyword(s):

Crude Oil ◽

Bacterial Species ◽

Bohai Bay ◽

Oily Wastewater ◽

New Approach ◽

First Order ◽

Flame Ionization ◽

First Order Kinetics ◽

Degradation Rates ◽

Degrading Bacteria

Abstract The aim of this study was to isolate hydrocarbons-degrading bacteria for treatment of oily wastewater from long-standing petroleum-polluted sediments in Bohai Bay, China. Six hydrocarbons-degrading bacteria were screened and identified as Pseudomonas sp. and Bacillus sp. A new approach using a combination of various bacterial species in petroleum biodegradation was proposed and evaluated for its degradation characteristics. Gas chromatography-flame ionization detection (GC-FID) analysis showed that mixed bacterial agents (YJ01) degraded 80.64% of crude oil and 76.30% of crude oil alkanes, exhibiting good biodegradation effect. Besides, after 14 days of culture, the biodegradation assessment markers, pristane and phytane, showed significant degradation rates of 46.75% and 78.23%, respectively. Kinetic analysis indicated that the degradation trends followed a single first-order kinetics model and the degradation half-life (t1/2) of 15 g/L crude oil was significantly shorter (5.48 days). These results indicated that YJ01 could degrade a wider range of hydrocarbons as well as some recalcitrant hydrocarbon components, and can be applied for bioremediation and treatment of oil-contaminated environment.

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Low-Concentration Kinetics of Atmospheric CH4 Oxidation in Soil and Mechanism of NH4+ Inhibition

Applied and Environmental Microbiology ◽

10.1128/aem.64.11.4291-4298.1998 ◽

1998 ◽

Vol 64 (11) ◽

pp. 4291-4298 ◽

Cited By ~ 98

Author(s):

Jay Gulledge ◽

Joshua P. Schimel

Keyword(s):

Salt Effect ◽

Competitive Inhibition ◽

Ch4 Oxidation ◽

First Order ◽

First Order Kinetics ◽

Taiga Soil ◽

Independent Mechanism ◽

Temperate Soils ◽

Taiga Soils ◽

Kinetics Of

ABSTRACT NH4 + inhibition kinetics for CH4 oxidation were examined at near-atmospheric CH4 concentrations in three upland forest soils. Whether NH4 +-independent salt effects could be neutralized by adding nonammoniacal salts to control samples in lieu of deionized water was also investigated. Because the levels of exchangeable endogenous NH4 + were very low in the three soils, desorption of endogenous NH4 +was not a significant factor in this study. TheKm(app) values for water-treated controls were 9.8, 22, and 57 nM for temperate pine, temperate hardwood, and birch taiga soils, respectively. At CH4 concentrations of ≤15 μl liter−1, oxidation followed first-order kinetics in the fine-textured taiga soil, whereas the coarse-textured temperate soils exhibited Michaelis-Menten kinetics. Compared to water controls, the Km(app) values in the temperate soils increased in the presence of NH4 + salts, whereas the V max(app) values decreased substantially, indicating that there was a mixture of competitive and noncompetitive inhibition mechanisms for whole NH4 + salts. Compared to the corresponding K+ salt controls, the Km(app) values for NH4 + salts increased substantially, whereas the V max(app) values remained virtually unchanged, indicating that NH4 + acted by competitive inhibition. Nonammoniacal salts caused inhibition to increase with increasing CH4 concentrations in all three soils. In the birch taiga soil, this trend occurred with both NH4 + and K+ salts, and the slope of the increase was not affected by the addition of NH4 +. Hence, the increase in inhibition resulted from an NH4 +-independent mechanism. These results show that NH4 +inhibition of atmospheric CH4 oxidation resulted from enzymatic substrate competition and that additional inhibition that was not competitive resulted from a general salt effect that was independent of NH4 +.

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Treatment of Simulated Wastewater Containing Chlorobenzene by Iron-Carbon Micro-Electrolysis Packing

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.113-116.176 ◽

2010 ◽

Vol 113-116 ◽

pp. 176-180 ◽

Cited By ~ 1

Author(s):

Meng Li ◽

Dong Lei Zou ◽

Hao Chen Zou ◽

Dong Yan Fan

Keyword(s):

Activated Carbon ◽

Ph Value ◽

Raw Materials ◽

Removal Rate ◽

Reaction Rates ◽

First Order ◽

First Order Kinetics ◽

Low Degree ◽

Simulated Wastewater ◽

Pseudo First Order

Using iron filings, activated carbon power and clay as raw materials, the granular iron-carbon micro-electrolysis packing was made by the method of calcination. The influence of initial chlorobenzene (CB) concentration, pH value and reaction temperature on the removal rate of simulated wastewater containing CB were investigated. The results showed that the reaction followed the pseudo-ﬁrst-order kinetics model and the rate constants varied at a relatively low degree at various pH. Temperature is an important parameter and an increase in temperature could signiﬁcantly raise the reaction rates. The column packed with packing was designed to remove CB in wastewater. After running for 70 days, the packing still had good performance and there was no obvious decrease on the removal rate.

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