Anaerobic Degradation Rates Research Articles

Monitoring of the three organophosphate esters TBP, TCEP and TBEP in river water and ground water (Oder, Germany).

The behaviour of the three organophosphate esters tributyl phosphate (TBP), tris(2-chloroethyl)phosphate (TCEP) and tris(2-butoxyethyl)phosphate (TBEP) during infiltration of river water to ground water has been investigated. The monitoring site is the Oder River and the adjacent Oderbruch aquifer. From March 2000 to July 2001, 76 ground water samples from monitoring wells located close to the Oder River and nine river water samples were collected. Additionally, influent and effluent samples from local waste water treatment plants, one sample of rain water and samples of roof runoff were collected. All samples were analysed by solid-phase-extraction followed by gas chromatography/mass spectrometry. TBP, TCEP and TBEP were detected at mean values of 622 ng l(-1), 352 ng l(-1), and 2955 ng l(-1), respectively in municipal waste water effluents. This points to a major input of these compounds into the Oder River by municipal waste water discharge. The concentrations of TBP and TBEP decreased downstream the Oder River possibly due to aerobic degradation. TBP, TCEP and TBEP were detected in ground water influenced predominantly by bank-filtered water. This demonstrates a transport of organic compounds by river water infiltration to ground water. TBP, TCEP and TBEP were also detected in rain water precipitation, roof runoff and ground water predominantly influenced by rain water infiltration. This hints to an input of these compounds to ground water by dry and wet deposition after atmospheric transport. Organophosphate esters were also detected in parts of the aquifer at 21 m depth. This demonstrates low anaerobic degradation rates of TBP, TCEP and TBEP.

Occurrence and microbial degradation of phthalate esters in Taiwan river sediments.

Concentrations and microbial degradation rates were measured for eight phthalate esters (PAEs) found in 14 surface water and six sediment samples taken from rivers in Taiwan. The tested PAEs were diethyl phthalate (DEP), dipropyl phthalate (DPP), di-n-butyl phthalate (DBP), diphenyl phthalate (DPhP), benzylbutyl phthalate (BBP), dihexyl phthalate (DHP), dicyclohexyl phthalate (DCP), and di-(2-ethylhexyl) phthalate (DEHP). In all samples, concentrations of DEHP and DBP were found to be higher than the other six PAEs. DEHP concentrations in the water and sediment samples ranged from ND to 18.5 microg/l and 0.5 to 23.9 microg/g, respectively; for DBP the concentration ranges were 1.0-13.5 microg/l and 0.3-30.3 microg/g, respectively. Concentrations of DHP, BBP, DCP and DPhP were below detection limits. Under aerobic conditions, average degradation half-lives for DEP, DPP, DBP, DPhP, BBP, DHP, DCP and DEHP were measured as 2.5, 2.8, 2.9, 2.6, 3.1, 9.7, 11.1 and 14.8 days, respectively; under anaerobic conditions, respective average half-lives were measured as 33.6, 25.7, 14.4, 14.6, 19.3, 24.1, 26.4 and 34.7 days. In other words, under aerobic conditions we found that DEP, DPP, DBP, DPhP and BBP were easily degraded, but DEHP was difficult to degrade; under anaerobic conditions, DBP, DPhP and BBP were easily degraded, but DEP and DEHP were difficult to degrade. Aerobic degradation rates were up to 10 times faster than anaerobic degradation rates.

Ongoing modification of Mediterranean Pleistocene sapropels mediated by prokaryotes.

Late Pleistocene organic-rich sediments (sapropels) from the eastern Mediterranean Sea harbor unknown, metabolically active chemoorganotrophic prokaryotes. As compared to the carbon-lean intermediate layers, sapropels exhibit elevated cell numbers, increased activities of hydrolytic exoenzymes, and increased anaerobic glucose degradation rates, suggesting that microbial carbon substrates originate from sapropel layers up to 217,000 years old. 16S ribosomal RNA gene analyses revealed that as-yet-uncultured green nonsulfur bacteria constitute up to 70% of the total microbial biomass. Crenarchaeota constitute a smaller fraction (on average, 16%). A slow but significant turnover of glucose could be detected. Apparently, sapropels are still altered by the metabolic activity of green nonsulfur bacteria and crenarchaeota.

Some Experiments and Conclusions about the Influence of Pure H2 Gason the Anaerobic Degradation of Propionate by Mixed Cultures

Reaction enthalpy for propionate degradationΔG0 is only negative when the partial pressure ofhydrogen pH2 is less than 10—4 bar. This means that for pH2 more than 10—4 bar, a total anaerobic degradation of propionate is impossible for thermodynamic reasons. Therefore, with increasing pH2, the anaerobic degradation rate of propionate via acetate is inhibited. There are two ways to investigate the inhibitory effect of pH2: to keep the concentration of hydrogen consuming bacteria low or to increase the mass transfer by feeding the hydrogen at higher flow rates. The author used an extended fixed bed reactor filled with polyurethane particles as a carrier for the bacteria, aerated with pure H2 gas. The results, compared with the literature by using model equations in order to standardize the data, correspond well: The addition of pure H2 gas has no observable effects on propionate degradation.In the fixed bed reactor with immobilized bacteria, it was not possible to reach an inhibitory concentration of H2 and high process stability could be maintained.

Impact of redox conditions on metolachlor and metribuzin degradation in mississippi flood plain soils

The effect of soil redox conditions on the degradation of metolachlor and metribuzin in two Mississippi soils (Forrestdale silty clay loam and Loring silt loam) were examined in the laboratory. Herbicides were added to soil in microcosms and incubated either under oxidized (aerobic) or reduced (anaerobic) conditions. Metolachlor and metribuzin degradation under aerobic condition in the Forrestdale soil proceeded at rates of 8.83 ngd‐1 and 25 ngd‐1, respectively. Anaerobic degradation rates for the two herbicides in the Forestdale soil were 8.44 ngd‐1 and 32.5 ngd‐1, respectively. Degradation rates for the Loring soil under aerobic condition were 24.8 ngd‐1 and 12.0 ngd‐1 for metolachlor and metribuzin, respectively. Metolachlor and metribuzin degradation rates under anaerobic conditions in the Loring soil were 20.9 ngd‐1 and 5.35 ngd‐1. Metribuzin degraded faster (12.0 ngd‐1) in the Loring soil under aerobic conditions as compared to anaerobic conditions (5.35 ngd‐1).

Natural attenuation of chlorinated ethene compounds: model development and field-scale application at the Dover site

A multi-dimensional and multi-species reactive transport model was developed to aid in the analysis of natural attenuation design at chlorinated solvent sites. The model can simulate several simultaneously occurring attenuation processes including aerobic and anaerobic biological degradation processes. The developed model was applied to analyze field-scale transport and biodegradation processes occurring at the Area-6 site in Dover Air Force Base, Delaware. The model was calibrated to field data collected at this site. The calibrated model reproduced the general groundwater flow patterns, and also, it successfully recreated the observed distribution of tetrachloroethene (PCE), trichloroethene (TCE), dichloroethylene (DCE), vinyl chloride (VC) and chloride plumes. Field-scale decay rates of these contaminant plumes were also estimated. The decay rates are within the range of values that were previously estimated based on lab-scale microcosm and field-scale transect analyses. Model simulation results indicated that the anaerobic degradation rate of TCE, source loading rate, and groundwater transport rate are the important model parameters. Sensitivity analysis of the model indicated that the shape and extent of the predicted TCE plume is most sensitive to transmissivity values. The total mass of the predicted TCE plume is most sensitive to TCE anaerobic degradation rates. The numerical model developed in this study is a useful engineering tool for integrating field-scale natural attenuation data within a rational modeling framework. The model results can be used for quantifying the relative importance of various simultaneously occurring natural attenuation processes.

Biodegradation of Three- and Four-Ring Polycyclic Aromatic Hydrocarbons under Aerobic and Denitrifying Conditions

PAHs are thought to be particularly persistent in environments where anaerobic conditions exist. This study presents evidence for the biodegradation of three- and four-ringed PAHs (anthracene, phenanthrene, and pyrene) under strict anaerobic, denitrifying conditions. Three pseudomonad strains, isolated from contrasting environments, were used in this study. All three strains were known PAH degraders and denitrifiers. Degradation proceeded to nondetectable levels (<0.001 mg/L) in 12−80 h for anthracene, 12−44 h for phenanthrene, and 24−72 h for pyrene. The rates of anaerobic degradation were typically slower than under aerobic conditions in almost all cases, except for strain SAG-R which had similar removal rates for all three and four-ring PAHs. Denitrification activity was verified by monitoring nitrate utilization and nitrous oxide production. Although none of the pseudomonads were adapted to the denitrifying conditions, only the pseudomonad isolated from a noncontaminated site (strain KBM-1) consistent...

Biodegradation of NSO-compounds under different redox-conditions

Laboratory experiments were carried out to investigate the potential of groundwater microorganisms to degrade selected heterocyclic aromatic compounds containing nitrogen, sulphur, or oxygen (NSO-compounds) under four redox-conditions over a period of 846 days. Eight compounds (pyrrole, 1-methylpyrrole, quinoline, indole, carbazole, dibenzothiophene, benzofuran, and dibenzofuran) were degraded under aerobic conditions, whereas thiophene and benzothiophene were degraded only when other compounds were degraded concomitantly. Quinoline and indole were the only two NSO-compounds degraded under anaerobic conditions, even though the microorganisms present in the anaerobic microcosms were active throughout the incubation period. A high variability in the lag period among the NSO-compounds was observed under aerobic conditions. While quinoline, indole, and carbazole were degraded with a lag period of 3–25 days, the lag periods for pyrrole, dibenzothiophene, benzofuran, and dibenzofuran were significantly longer (29–278 days). Under anaerobic conditions, lag periods of 100–300 days were observed. Differences in the degradation rate among the compounds were also observed. Indole, quinoline, carbazole, and benzofuran were quickly degraded in the aerobic microcosms, whereas a slow degradation of dibenzothiophene and dibenzofuran was observed. Pyrrole and 1-methylpyrrole were slowly degraded and 1-methylpyrrole was not completely removed within the 846 days. The anaerobic degradation rate was significantly slower than the aerobic degradation rate. The degradation rate under sulphate-reducing conditions was higher than under denitrifying and methanogenic conditions, though after re-addition of a compound a quick removal was observed. The persistence of many NSO-compounds under anaerobic conditions together with the long lag periods and the low degradation rates under aerobic conditions suggest that NSO-compounds might persist in groundwater at creosote-contaminated sites.

Effects of nitrobenzene and zinc on acetate utilizing methanogens

Determination of anaerobic degradation rates and toxic effects of nitrobenzene (NB) on acetate utilizing methanogens was the first objective of this research. Serum bottles were used for anaerobic toxicity assays with an acetate enrichment culture of methanogens. Ten mg/l of nitrobenzene did not inhibit total gas production in the acetate enrichment methanogenic culture. Twenty and thirty mg/l of nitrobenzene caused reversible inhibition of methanogenesis. Batch kinetic experiments showed that 20 mg/l of nitrobenzene was degraded with a first-order rate constant, k, of 0.37 d −1. Acetate was not degraded during the first 7 days when the measured nitrobenzene concentration was higher than about 1 mg/l. The second objective was to determine the effect of zinc on nitrobenzene degradation in methanogenic systems. Ten mg/l of spiked zinc caused a reduction of gas production in the systems with 10 mg/l of nitrobenzene; 20 mg/l of zinc led to failures of systems with 10 and 20 mg/l of nitrobenzene. With 10 and 20 mg/l of added zinc, the k value for nitrobenzene degradation decreased to 0.18 d −1 and 0.14 d −1, respectively. With 20 mg/l of Zn, acetate was not degraded at all even after nitrobenzene concentration reached 0.1 mg/l, indicating toxicity of Zn to methanogenesis. Abiotic control tests with autoclaved culture showed that adsorption alone could remove 60–70% of spiked nitrobenzene in 36 days. However, the samples extracted from solids in the methanogenic test systems showed that nitrobenzene was below the detection limit of 0.1 mg/l, indicating biodegradation of nitrobenzene in these systems. Traces of benzene were seen as an intermediate in the liquid samples. Headspace analysis showed that nitrobenzene and benzene were below detection limits.

Some biochemical aspects of the anaerobic degradation of dairy wastewater

Low rate of anaerobic degradation together with inhibition problems caused by components such as milk fat and proteins were found to be reasons for restricted activity of high-rate anaerobic reactors operated with dairy effluent. The present research was aimed to investigate the influence of some relevant compounds, such as casein and milk fat and their degradation compounds, on process efficiency. Methanogenic activity and ATP content of the sludge were used as major follow up criteria for evaluating the influence of the tested compounds on process efficiency. It was found that casein was not degraded by anaerobic cultures which were not pre-acclimated for this compound. On the other hand, cultures acclimated to casein, utilized it very efficiently. Amino acids typical for casein degradation were also used efficiently with no inhibitory effects under the test conditions and with no need for culture pre-acclimatization. Milk fat was found to be a major cause for inhibition of methanogenic activity. It was found to have an immediate influence on reducing gas production rate in reactors to which it was added. Milk fat was also found to have long term effects: sludge pre-exposed to milk fat exhibited reduced methanogenic activity when tested in medium free of milk fat. Milk fat also reduced the ATP concentration in the sludge, indicating reduction of its total physiological activity. Oleic acid, which is a major derivative of milk fat hydrolysis was found to have inhibitory effects on methane production and on ATP concentration. According to the results of the present research, it would be advisable to treat dairy effluents by anaerobic digestion only after reduction of the milk fat concentration below 100 mg/L, and after careful acclimatization of the digester culture to casein.

Aerobic and Anaerobic Degradation of Alachlor in Samples from a Surface‐to‐Groundwater Profile

AbstractEstimates of pesticide degradation rates in subsoils are needed to improve models predicting pesticide movement to groundwater. Biodegradation rates of the herbicide alachlor [2‐chloro‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)acetamide] in surface soil, vadose zone, and aquifer samples collected from a single site near Plains, GA were determined in the laboratory under aerobic and anaerobic conditions. Degradation was described by first‐order kinetics during 126 d of incubation. Under aerobic conditions the halflife (t1/2) of alachlor in the surface soil (t1/2 = 23 d) was less than in the vadose zone (t1/2 = 73 to 285 d) and aquifer samples (t1/2 = 320 to 324 d). Alachlor in anaerobic samples degraded less rapidly in the surface (0 to 0.6 m) and the next deepest (0.6 to 2.4 m) subsoil than under aerobic conditions (t1/2 = 100 and 144 d, respectively). Degradation in anaerobic aquifer samples was very slow (t1/2 = 337 to 553 d). Addition of organic nutrients enhanced aerobic degradation in subsurface soils and one aquifer sample, indicating that nutrient availability limits biodegradation. Total aerobic microbial populations ranged from 6.6 × 103 to 2.5 × 106 cells per gram of soil in the subsoils and aquifer samples, but were not correlated with aerobic or anaerobic degradation rates. The lower degradation rates in vadose zone and aquifer materials may be due to less microbial activity or the absence of alachlor degraders.

Petroleum and Chlorinated Hydrocarbon Analysis in Support of In Vitro Studies of Natural Anaerobic and Aerobic Microbial Degradation of Xenobiotics in Contaminated Groundwater and Soil

Abstract This program investigated in situ biological degradation as a remedial treatment technique at a United States Air Force Base in Texas. Soil and groundwater samples from the site were characterized regarding microbial populations and presence or absence of priority pollutant xenobiotics and petroleum hydrocarbon components. Time-series analyses of replicate nutrient-amended microcosms after approximately 1, 25, 50 and 100 days permitted aerobic and anaerobic degradation rate evaluation. Microcosm integrity was demonstrated throughout the experiment by observing appropriate dissolved oxygen, pH, oxidation/reduction potential, and sterile/viable conditions. Gas chromatographic analysis and ratios of straight-chain and isoprenoid components clearly demonstrated that aerobic conditions were preferred for degradation of aliphatic and aromatic petroleum hydrocarbons. Electron capture gas chromatographic analyses and purge-and-trap gas chromatographic/mass spectrometric analyses of lower molecular weight...

A study of the chemical stability of amphotericin B in N, N-dimethylacetamide

Studies have demonstrated the potential for using N, N-dimethylacetamide (DMA) as a solvent for solubilizing amphotericin B. The addition of sodium deoxycholate (NaDOC) to the DMA further enhanced the solubility of amphotericin B. To complement this solubility study the chemical stability of amphotericin B in DMA was investigated. The degradation of amphotericin B in DMA occurs by both an aerobic and an anaerobic pathway with the major route of decomposition at 30 °C involving oxygen. For example, under aerobic conditions at 30 °C, the pseudo-first-order rate constant for the degradation of amphotericin B in 1% (w/v) NaDOC/DMA is 1.23 × 10 −2 h −1 while under anaerobic conditions (carried out in an anhydrous, oxygen-free, nitrogen-filled glove box) the pseudo-first-order rate constant for the degradation of amphotericin B in 1% NaDOC/DMA at 3°C is 3.50 × 10 −3 h −1. Both of these pathways displayed Arrhenius temperature-dependent kinetics with activation energies of 17.5 and 23.5 kcal/mol for the aerobic reaction and the anaerobic reaction, respectively. In the concentration range studied (0.14–1.4% w/w), the percentage of water in the DMA did not alter the rate of anaerobic degradation of amphotericin B in 1% NaDOC/DMA. The influence of light, amphotericin A content, NaDOC level and heavy metal impurities on the rates of degradation of amphotericin B in 1% NaDOC/DMA (under aerobic and anaerobic contitions) was also determined and was found to be negligible.

Aldicarb degradation in sandy soils from different depths

AbstractAerobic and anaerobic degradation rates for aldicarb were measured in soil samples collected at different depths from a citrus grove near Davenport, Florida, together with the changes in concentration of its two toxic oxidation products, aldicarb sulfoxide and aldicarb sulfone. These data were used to estimate the first‐order rate‐constants for concurrent oxidation and hydrolysis of aldicarb, aldicarb sulfoxide, and aldicarb sulfone, and for the loss of total carbamate residues (TCR = aldicarb + aldicarb sulfoxide + aldicarb sulfone). Both oxidation and hydrolysis rate‐constants for aldicarb in surface samples (0‐30 cm) were larger than those in sub‐surface samples (30‐300 cm). Under aerobic conditions, microbial oxidation appeared to be the major route for aldicarb degradation in surface and shallow sub‐surface samples (30‐150 cm), whereas chemical hydrolysis appeared to be the dominant pathway in deep sub‐surface samples (150‐300 cm). Aldicarb in deep sub‐surface samples under anaerobic conditions was primarily degraded through hydrolysis and only trace amounts of aldicarb sulfoxide were detected. Time to 50% disappearance (DT50) values for TCR loss were generally invariant with depth. In sub‐surface samples, DT50 values under aerobic and anaerobic conditions were similar.

Anaerobic mineralization of marine sediment organic matter: Rates and the role of anaerobic processes in the oceanic carbon economy

Abstract This paper addresses three related questions: (1) What factors control the efficiency of carbon burial in sediments? (2) Are rates of anaerobic organic matter degradation intrinsically lower than aerobic rates? (3) How important are anaerobic processes in the global marine sediment carbon economy? Carbon burial efficiency (the ratio of the carbon burial rate and the carbon flux to the sediment surface) was estimated from literature data for a range of environments and was shown to be a function of sedimentation rate. No difference independent of sedimentation rate was found between aerobic and anaerobic sediments. A review of recent microcosm and laboratory studies shows that anaerobic rates are not intrinsically lower than aerobic rates; fresh organic matter degrades at similar rates under oxic and anoxic conditions. Aerobic decomposition rates near the sediment surface are typically greater than anaerobic rates at depth because the most labile carbon is consumed before it can be buried in the a...

Thermophilic Anaerobic Biodegradation of [ 14 C]Lignin, [ 14 C]Cellulose, and [ 14 C]Lignocellulose Preparations

Thermophilic (55 degrees C) anaerobic enrichment cultures were incubated with [C-lignin]lignocellulose, [C-polysaccharide]lignocellulose, and kraft [C]lignin prepared from slash pine, Pinus elliottii, and C-labeled preparations of synthetic lignin and purified cellulose. Significant but low percentages (2 to 4%) of synthetic and natural pine lignin were recovered as labeled methane and carbon dioxide during 60-day incubations, whereas much greater percentages (13 to 23%) of kraft lignin were recovered as gaseous end products. Percentages of label recovered from lignin-labeled substrates as dissolved degradation products were approximately equal to percentages recovered as gaseous end products. High-pressure liquid chromatographic analyses of CuO oxidation products of sound and degraded pine lignin indicated that no substantial chemical modifications of the remaining lignin polymer, such as demethoxylation and dearomatization, occurred during biodegradation. The polysaccharide components of pine lignocellulose and purified cellulose were relatively rapidly mineralized to methane and carbon dioxide; 31 to 37% of the pine polysaccharides and 56 to 63% of the purified cellulose were recovered as labeled gaseous end products. An additional 10 to 20% of the polysaccharide substrates was recovered as dissolved degradation products. Overall, these results indicate that elevated temperatures can greatly enhance rates of anaerobic degradation of lignin and lignified substrates to methane and low-molecular-weight aromatic compounds.

Microbial transformation of alkylpyridines in groundwater

The microbiological degradation of a mixture of alkylpyridines in groundwater maintained under aerobic and anaerobic conditions was examined. A marked difference was observed between the aerobic and anaerobic degradation rates. In the presence of a soil inoculum and under aerobic conditions, the residual alkylpyridine concentrations generally approached zero concentration within 10 to 31 days of incubation, whereas under anaerobic conditions the concentrations of residual alkylpyridines only decreased between 40 and 80% over a 33 day incubation period. Biodegradation rates under aerobic conditions were greatly affected by the specific ring substitution of structural isomers within a given weight class. A similar effect was not observed for anaerobic degradation rates.

FURTHER STUDY ON QUALITY CONTROL OF THE RED BLOOD CELLS PRESERVED IN VITRO

The buffer systems, Ringer's Tris-solution and Ringer's NaHCO_3 solution, have been compared for the determination of anaerobic degradation rate of the preserved red blood cells. The results obtained in the employment of these two solutions were very close to each other (r=0.9952). The experiment proved that Ringer's Tris-solution is superior to Ringer's NaHCO_3 solution. The method can eliminate the appearance of peak anaerobic degradation rate (over 100%) in the early stage of the preservation of red blood cells. The method is reliable, can be repeated, easy to handle and not exacting in condition requirements.It has been successfully applied to the preservation investigation of wholo blood, conoentrated red cells and frozen blood.

The Responses of Soils and Soil Microorganisms to Silver Iodide Weather Modification Agents

AbstractTo determine the consequences of AgI weather modification agent accumulation to the soil microbial environment, the effects of added silver compounds on microbial growth, anaerobic cellulose degradation, and the soil environment adjacent to a cloud seeding generator were investigated. Silver ion from AgNO3 inhibited microbial growth in cultures at concentrations as low as 6 × 10−9 g ml−1 and cultures saturated with AgI displayed an inhibition of growth initiation approximately equivalent to 35 × 10−9 g ml−1 silver ion. Muds containing AgI exhibited significantly decreased anaerobic cellulose degradation rates in long term experiments, when concentrations of 100 µg AgI/g were present. An analysis of the soil surrounding a seeding generator site in Steamboat Springs, Colorado indicated that deposited silver tends to remain near the soil surface (0–2 cm). Alterations in the soil environment due to high silver concentrations were indicated by consistently higher organic matter levels, water contents, microbial populations, and rates of soil respiration. These results suggest that high concentrations of seeding agent potentially can alter the soil microbial environment by inhibiting organic matter decomposition, but that the silver levels which accumulate in seeded target areas should have no overt effects on the soil environment.

Rate of Anaerobic Degradation of Ascorbic Acid in Aqueous Solution

The pH rate profile of the rate of disappearance of ascorbic acid from aqueous solution under anaerobic conditions has been determined at 96°. The dependency on pH is surprisingly low over pH range of 1-11. The profile shows a small but apparently real maximum at pH = pKa 1 , an effect which can be rationalized by assuming formation of a salt-acid complex in solutions. The anaerobic rate shows buffer dependency but relatively small ionic strength effect.