Anaerobic Degradation Processes Research Articles

Deciphering biodegradation effects on light hydrocarbons in crude oils using their stable carbon isotopic composition: A case study from the Gullfaks oil field, offshore Norway

Compound-specific isotope analysis has become an important tool in environmental studies and is an especially powerful way to evaluate biodegradation of hydrocarbons. Here, carbon isotope ratios of light hydrocarbons were used to characterise in-reservoir biodegradation in the Gullfaks oil field, offshore Norway. Increasing biodegradation, as characterised, for example, by increasing concentration ratios of Pr/ n-C 17 and Ph/ n-C 18, and decreasing concentrations of individual light hydrocarbons were correlated to 13C-enrichment of the light hydrocarbons. The δ 13C values of C 4 to C 9 n-alkanes increase by 7–3‰ within the six oil samples from the Brent Group of the Gullfaks oil field, slight changes (1–3‰) being observed for several branched alkanes and benzene, whereas no change (<1‰) in δ 13C occurs for cyclohexane, methylcyclohexane, and toluene. Application of the Rayleigh equation demonstrated high to fair correlation of concentration and isotope data of i- and n-pentane, n-hexane, and n-heptane, documenting that biodegradation in reservoirs can be described by the Rayleigh model. Using the appropriate isotope fractionation factor of n-hexane, derived from laboratory experiments, quantification of the loss of this petroleum constituent due to biodegradation is possible. Toluene, which is known to be highly susceptible to biodegradation, is not degraded within the Gullfaks oil field, implying that the local microbial community exhibits rather pronounced substrate specificities. The evaluation of combined molecular and isotopic data expands our understanding of the anaerobic degradation processes within this oil field and provides insight into the degradative capabilities of the microorganisms. Additionally, isotope analysis of unbiodegraded to slightly biodegraded crude oils from several oil fields surrounding Gullfaks illustrates the heterogeneity in isotopic composition of the light hydrocarbons due to source effects. This indicates that both source and also maturity effects have to be well constrained when using compound-specific isotope analysis for the assessment of biodegradation.

The anaerobic treatment approach towards a more sustainable and robust environmental protection

Anaerobic biological degradation processes (AnDe), when properly integrated with complementary biological and physical methods, constitute the ideal route to a sustainable protection of the life environment. However unfortunately for a smooth implementation of AnDe-processes drastic conceptual innovations are urgently needed in the field of environment protection; the present highly centralized approach in the public sanitation sector (CENSA) need to be substituted by a concept that focuses on optimal decentralization, problem prevention, self-sufficiency, resource recovery and reuse, with coupling to agriculture practices at or nearby the location (DESAR). Although a variety of excellent DESAR-based systems already are available and anaerobic digestion and treatment methods have found successful full-scale application for waste and wastewater treatment, there still is potential to improve these systems. Interesting questions to be elucidated are the effect of trace elements and macro-nutrients, the sludge immobilization phenomenon and the effect of environmental factors like temperature, pressure, mixing. Therefore tentatively a lot of challenging interdisciplinary research is waiting to attain further profitable innovations.

Groundwater contamination by chlorinated naphthalenes and related substances caused by activities of a former military base

Water samples derived from two different aquifer layers of six sampling sites were analysed by GC/MS in order to characterize a groundwater contamination caused by chemicals used for wood impregnation. Mono- and dichlorinated naphthalenes, chlorobenzo( b)thiophene, 1-chloro-4-naphthol, 1-chloronaphthoic acid, acenaphthene and methyled naphthalenes were identified as the main pollutants and quantified. 1-Chloro-4-naphthol and 1-chloronaphthoic acid are discussed as possible indicators for anaerobic degradation processes. Results of inorganic and compound specific stable carbon isotope analyses revealed only a minor degree of microbiological transformation. Thus, sorption was characterized as the main attenuation process within the aquifer affecting the contamination described.

Anaerobic hydrocarbon biodegradation in deep subsurface oil reservoirs.

Biodegradation of crude oil in subsurface petroleum reservoirs is an important alteration process with major economic consequences. Aerobic degradation of petroleum hydrocarbons at the surface is well documented and it has long been thought that the flow of oxygen- and nutrient-bearing meteoric waters into reservoirs was necessary for in-reservoir petroleum biodegradation. The occurrence of biodegraded oils in reservoirs where aerobic conditions are unlikely, together with the identification of several anaerobic microorganisms in oil fields and the discovery of anaerobic hydrocarbon biodegradation mechanisms, suggests that anaerobic degradation processes could also be responsible. The extent of anaerobic hydrocarbon degradation processes in the world's deep petroleum reservoirs, however, remains strongly contested. Moreover, no organism has yet been isolated that has been shown to degrade hydrocarbons under the conditions found in deep petroleum reservoirs. Here we report the isolation of metabolites indicative of anaerobic hydrocarbon degradation from a large fraction of 77 degraded oil samples from both marine and lacustrine sources from around the world, including the volumetrically important Canadian tar sands. Our results therefore suggest that anaerobic hydrocarbon degradation is a common process in biodegraded subsurface oil reservoirs.

Modeling Biodegradation of Organic Contaminants under Multiphase Conditions with TMVOCBio

The existing TMVOC numerical reservoir simulator, developed to model the migration of organic mixtures in the subsurface under multiphase conditions, was improved by adding capabilities for the modeling of aerobic and anaerobic biodegradation reactions of hydrocarbons and chlorinated solvents. Reactive transport is coupled with the multiphase nonisothermal flow of multicomponent fluid mixtures containing water and sets of user-defined noncondensible gases (NCG), volatile organic compounds (VOCs), and dissolved solids. The mathematical formulation of biodegradation reactions, a modified version of that developed for the BIOMOC computer code, is presented together with underlying assumptions. TMVOCBio allows the modeling of simultaneously occurring aerobic and anaerobic degradation processes involving multiple organic substrates, electron acceptors (EA), and nutrients, accounting for the inhibition phenomena conventionally considered by other analytical and numerical codes. Code verification against accurate numerical solutions and code validation against published laboratory and field experimental results relevant to saturated subsurface systems showed good agreement.

Modeling Biodegradation of Organic Contaminants under Multiphase Conditions with TMVOCBio

The existing TMVOC numerical reservoir simulator, developed to model the migration of organic mixtures in the subsurface under multiphase conditions, was improved by adding capabilities for the modeling of aerobic and anaerobic biodegradation reactions of hydrocarbons and chlorinated solvents. Reactive transport is coupled with the multiphase nonisothermal flow of multicomponent fluid mixtures containing water and sets of user‐defined noncondensible gases (NCG), volatile organic compounds (VOCs), and dissolved solids. The mathematical formulation of biodegradation reactions, a modified version of that developed for the BIOMOC computer code, is presented together with underlying assumptions. TMVOCBio allows the modeling of simultaneously occurring aerobic and anaerobic degradation processes involving multiple organic substrates, electron acceptors (EA), and nutrients, accounting for the inhibition phenomena conventionally considered by other analytical and numerical codes. Code verification against accurate numerical solutions and code validation against published laboratory and field experimental results relevant to saturated subsurface systems showed good agreement.

Biological degradation and greenhouse gas emissions during pre-storage of liquid animal manure.

Storage of manure makes a significant contribution to global methane (CH4) emissions. Anaerobic digestion of pig and cattle manure in biogas reactors before outside storage might reduce the potential for CH4 emissions. However, manure pre-stored at 15 to 20 degrees C in buildings before anaerobic digestion may be a significant source of CH4 and could reduce the potential CH4 production in the biogas reactor. Degradation of energy-rich organic components in slurry and emissions of CH4 and carbon dioxide (CO2) from aerobic and anaerobic degradation processes during pre-storage were examined in the laboratory. Newly mixed slurry was added to vessels and stored at 15 and 20 degrees C for 100 to 220 d. During storage, CH4 and CO2 emissions were measured with a dynamic chamber technique. The ratio of decomposition in the subsurface to that at the surface indicated that the aerobic surface processes contributed significantly to CO2 emission. The measured CH4 emission was used to calculate the methane conversion factor (MCF) in relation to storage time and temperature, and the total carbon-C emission was used to calculate the decrease in potential CH4 production by anaerobic digestion following pre-storage. The results show substantial methane and carbon dioxide production from animal manure in an open fed-batch system kept at 15 to 20 degrees C, even for short storage times, but the influence of temperature was not significant at storage times of <30 d. During long-term storage (90 d), a strong influence of temperature on the MCF value, especially for pig manure, was observed.

Biological Degradation and Greenhouse Gas Emissions during Pre-Storage of Liquid Animal Manure

Storage of manure makes a significant contribution to global methane (CH4) emissions. Anaerobic digestion of pig and cattle manure in biogas reactors before outside storage might reduce the potential for CH4 emissions. However, manure pre-stored at 15 to 20°C in buildings before anaerobic digestion may be a significant source of CH4 and could reduce the potential CH4 production in the biogas reactor. Degradation of energy-rich organic components in slurry and emissions of CH4 and carbon dioxide (CO2) from aerobic and anaerobic degradation processes during pre-storage were examined in the laboratory. Newly mixed slurry was added to vessels and stored at 15 and 20°C for 100 to 220 d. During storage, CH4 and CO2 emissions were measured with a dynamic chamber technique. The ratio of decomposition in the subsurface to that at the surface indicated that the aerobic surface processes contributed significantly to CO2 emission. The measured CH4 emission was used to calculate the methane conversion factor (MCF) in relation to storage time and temperature, and the total carbon-C emission was used to calculate the decrease in potential CH4 production by anaerobic digestion following pre-storage. The results show substantial methane and carbon dioxide production from animal manure in an open fed-batch system kept at 15 to 20°C, even for short storage times, but the influence of temperature was not significant at storage times of <30 d. During long-term storage (90 d), a strong influence of temperature on the MCF value, especially for pig manure, was observed.

Pharmaceuticals and health care products in wastewater effluents: the example of carbamazepine

Persistence and impact of pharmaceutics in the environment are discussed. The case of carbamazepine (CBZ), a widely used antiepileptic drug detected in rivers, lakes, sludges and even in ground water is examined. CBZ fate was investigated in all possible routes that may follow after it has been discharged to the sewage system: activated sludge, anaerobic digestion sludge, seawater, fresh water and soil. Carbamazepine slowed down, i.e. caused a decrease in the COD consumption rate in the activated sludge process, especially after longer term exposure, while the anaerobic sludge process was unaffected in the operating conditions that were applied. The compound was not degraded under either short term or long term exposure to either aerobic or anaerobic degradation processes. Carbamazepine seemed to biosorb to solid phases (soil, sludge) and this strength of sorption was related to the organic content of the solid phase. These results explain why CBZ is a very persistent xenobiotic compound, as is apparent from its detection in appreciable amounts in various aquatic environments.

Anaerobic degradation of organic materials - significance of the substrate surface area

In anaerobic degradation of substrates containing mainly particulate organic matter, solids hydrolysis is rate-limiting. In these investigations, the particle size of various substrates was reduced by comminution to support hydrolysis. Two positive effects of comminution were observed. For substrates with high fibre content, which are particularly resistant to biodegradation, a significant improvement of the degradation degree was observed as a result of comminution. Secondly, for all substrates tested, and particularly for those rich in fibres, the degradation rate of comminuted samples was significantly higher. The first reason for both effects is an increase of the sample surface area. Several methods for measuring the specific surface area of organic materials, including particle size analysis, Nitrogen-adsorption and enzyme adsorption, were used and compared for the purpose of this study, where the surface area accessible to microbial enzymes is critical. The significance of the surface area in anaerobic degradation of particulate substrates was investigated through a kinetic model where the hydrolysis rate was based on the sample surface area. Good agreements were obtained between model and experiments carried out with samples of various specific surface areas. These results reinforced the significance of the sample area in anaerobic degradation processes. However, other effects of comminution responsible for the increased degradation degree and degradation rate were identified and discussed. These include: the increase of dissolved compounds due to cell rupture, exposition of surface areas previously inacessible for microbial degradation, and alteration of the sample structure such as the lignin-cellulose arrangements.

Inverse modeling of BTEX dissolution and biodegradation at the Bemidji, MN crude-oil spill site

The U.S. Geological Survey (USGS) solute transport and biodegradation code BIOMOC was used in conjunction with the USGS universal inverse modeling code UCODE to quantify field-scale hydrocarbon dissolution and biodegradation at the USGS Toxic Substances Hydrology Program crude-oil spill research site located near Bemidji, MN. This inverse modeling effort used the extensive historical data compiled at the Bemidji site from 1986 to 1997 and incorporated a multicomponent transport and biodegradation model. Inverse modeling was successful when coupled transport and degradation processes were incorporated into the model and a single dissolution rate coefficient was used for all BTEX components. Assuming a stationary oil body, we simulated benzene, toluene, ethylbenzene, m, p-xylene, and o-xylene (BTEX) concentrations in the oil and ground water, respectively, as well as dissolved oxygen. Dissolution from the oil phase and aerobic and anaerobic degradation processes were represented. The parameters estimated were the recharge rate, hydraulic conductivity, dissolution rate coefficient, individual first-order BTEX anaerobic degradation rates, and transverse dispersivity. Results were similar for simulations obtained using several alternative conceptual models of the hydrologic system and biodegradation processes. The dissolved BTEX concentration data were not sufficient to discriminate between these conceptual models. The calibrated simulations reproduced the general large-scale evolution of the plume, but did not reproduce the observed small-scale spatial and temporal variability in concentrations. The estimated anaerobic biodegradation rates for toluene and o-xylene were greater than the dissolution rate coefficient. However, the estimated anaerobic biodegradation rates for benzene, ethylbenzene, and m, p-xylene were less than the dissolution rate coefficient. The calibrated model was used to determine the BTEX mass balance in the oil body and groundwater plume. Dissolution from the oil body was greatest for compounds with large effective solubilities (benzene) and with large degradation rates (toluene and o-xylene). Anaerobic degradation removed 77% of the BTEX that dissolved into the water phase and aerobic degradation removed 17%. Although goodness-of-fit measures for the alternative conceptual models were not significantly different, predictions made with the models were quite variable.

New Objectives of Sludge Treatment Considering a Safe Sludge Removal

AbstractSewage sludge consists of valuable components such as nutrients as well as harmful substances, e.g. heavy metals. For sludge with a low concentration of pollutants, its utilization in agriculture is the best way of sludge reuse. Carbon recycling is also possible by using disintegration in combination with anaerobic degradation processes. The other important compound in sludge is phosphorus, which is a limited resource on earth. Recycling options for phosphorus are also described in the paper. A safe disposal of the residues can be achieved by using incineration.

Burial and reactivity of sedimentary microalgal lipids in bioturbated Mediterranean coastal sediments

The fate of microalgal lipid biomarkers in marine coastal sediments when acted on by natural bioturbation processes (Carteau Bay, Gulf of Fos, Mediterranean Sea) was studied under laboratory conditions. Both dead phytoplanktonic cells ( Nannochloropsis salina) and luminophores (inert fluorescent particulate tracers) were deposited at the surface of intact sediment cores which were then incubated for 22, 44 and 63 days. Sediment reworking and concentration profiles of specific lipid components of N. salina ( n-alkenes, alkyl diols, sterols and fatty acids) were determined as a function of time and depth. The results show that, in the sediment investigated, bioturbation occurs essentially as a biodiffusive process and that it has a rapid and significant impact on the qualitative and quantitative record of sedimentary lipids. Whereas most of the biomarkers were detected in the entire reworked layer (0–6 cm) after 22 days, n-alkenes were never detected below 3 cm due to their low concentration and their high reactivity. For each individual lipid, the comparison of the amounts obtained from the inventories of biomarkers in the reworked zone, with the amount deposited initially at the sediment surface, allowed the determination of its extent and rate of degradation. These ranged from 72% to 99% and from 0.010 to 0.047 day −1, respectively, depending on the biomarker considered, with polyunsaturated fatty acids (PUFAs) and alkenes being degraded faster than the other components. Comparison with previous work suggests that, in biologically reworked sediments, the apparent reactivity of lipids is: (i) positively correlated with the biological mixing coefficient ( D b) and, (ii) generally much higher than in non-bioturbated (anoxic) sediments. Our results also support the idea that degradation of lipids in reworked sediments involves the combined effects of aerobic and anaerobic degradation processes, but that biological mixing results in diagenetic properties more characteristic of completely oxidized conditions.

Anaerobic digestion: concepts, limits and perspectives

Anaerobic degradation processes are faced with limitations with respect to reaction energetics and reaction kinetics. The small amount of energy available in methanogenic degradation of complex organic compounds allows in most cases only the conservation of minimum amounts of energy in the lowest range of energy exploitable by biochemical reactions for ATP-synthesis. This limit has to be defined in the range of 1/3-1/4 of an ATP unit, or 15-20 kJ per mol reaction. Such small amounts of energy are exploited efficiently by syntrophic microbial communities co-operating e.g. in fatty acid conversion to methane and CO2. Methanogens also set the stage for efficient conversion of sugars or amino acids, and channel electron fluxes to the utmost efficiency. Kinetic limitations are set by the inertness of certain compounds, e.g. hydrocarbons, to react in the absence of a strong oxidant. New reactions have been found recently which activate such compounds, e.g. aromatic hydrocarbons such as toluene, xylenes, naphthalene, methane, or ammonia. Refined techniques for analysis of microbial activities in ill defined natural environments such as digestive tracts of small invertebrates or polluted aquifers have shown an amazing capacity for anaerobic or oxygen-limited degradation processes that are still to be exploited. Thus, anaerobic digestion is still a matter of fast increasing knowledge, both on the side of basic research as well as on the side of application in treatment of soil, waste materials, or in understanding complex living communities.

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.

A laboratory-scale exploration of the long-term behaviour of mechanically separated organic residue in a flushing bioreactor

At VAM waste treatment company in Wijster (the Netherlands) a demonstration is in progress of bioreactor technology for treatment of the mechanically separated organic residue (MSOR) of a waste separation plant. In order to explore the long-term behaviour of MSOR in a bioreactor additional laboratory-scale research is initiated, which runs analogously with the bioreactor demonstration. In laboratory-scale test columns the anaerobic degradation processes are enhanced, and full biological stabilization was expected within a year. This paper examines the objectives, experimental set-up and first results from the laboratory-scale research.

A laboratory-scale exploration of the long-term behaviour of mechanically separated organic residue in a flushing bioreactor

At VAM waste treatment company in Wijster (the Netherlands) a demonstration is in progress of bioreactor technology for treatment of the mechanically separated organic residue (MSOR) of a waste separation plant. In order to explore the long-term behaviour of MSOR in a bioreactor additional laboratory-scale research is initiated, which runs analogously with the bioreactor demonstration. In laboratory-scale test columns the anaerobic degradation processes are enhanced, and full biological stabilization was expected within a year. This paper examines the objectives, experimental set-up and first results from the laboratory-scale research.

Identification and Quantification of Redox Reactions at the Sea Water-Brine Interface of the Orca Basin (Gulf of Mexico)

The Orca basin is a depression located on the northern slope of the Gulf of Mexico. It drops from the surrounding seafloor water depth (1800 m) to about 2400 m. The lower 150 m of the basin are filled with a brine which is separated from the overlying sea water by a strong density stratification due to the increase of salinity from 35 to about 260%o. The stratification lowers transport rates dramatically, hence, increasing the residence time of settling particulate organic matter in the salinity transition zone. Furthermore, resupply of oxygen to this zone is limited. As a result, the oxic-anoxic interface coincides with the salinity transition zone, promoting anaerobic degradation processes, as well as redox reactions involving reduced byproducts of anaerobic degradation such as Mn(II), Fe(II) or sulphide. The depth range over which these reactions occur extends over several meters, instead of the centimeter scale redox gradients usually observed in sediments.

Monitoring degradation processes of explosives by HPLC analysis with UV- and amperometric detection

The impact of spilled explosives, their by-products and degradation products on human beings and the environment has been recognised as a serious problem at areas of existing and former ammunition plants. In nature, aerobic and anaerobic degradation processes of explosives and their accompanying compounds yield polar contaminants with relatively high water solubilities. Most are potentially carcinogenic and mutagenic. An HPLC method applying UV-detection for nitroaromatic compounds and amperometric detection for aminoaromatic and phenolic compounds was used for monitoring the degradation of explosives in a polluted groundwater sample under natural conditions. Analysis was performed by direct injection of aliquots of the sample after exposition to daylight for different periods of time.

Temperature regulation of anaerobic degradation of organic matter

Anaerobic degradation of organic matter follows similar pathways in digesters and anaerobic freshwater sediments. The responsible microorganisms are linked in a complex food web, where short chain fatty acids and H2 are important intermediates. Degradation of short-chain fatty acids is endothermic under standard conditions and is only possible at low H2 partial pressures maintained by exothermic methanogenesis. The coupling between these endothermic and exothermic processes is delicate, and hence sensitive to environmental changes such as temperature variations. The effect of temperature on thermodynamics and on kinetics of these and other anaerobic degradation processes with emphasis on freshwater ecosystems is discussed.