Rate Of Oil Biodegradation Research Articles

Evaluating The Addition of Fine Particles To Enhance Oil Degradation

ABSTRACT Natural biodegradation rates of oil within the marine environment are partly controlled by surface availability, as microbial attack primarily occurs at the oil-water interface. Therefore, increasing the surface area of residual oil by the addition of fine oleophilic particles may prove to be an effective bioremediation strategy. Considering commercial availability and cost, heat-treated peat was identified to be a promising particle source as it has high oil absorption properties and does not compete with oil as an alternative carbon source to oil-degrading bacteria. A preliminary laboratory experiment conducted with a respirometry system demonstrated the feasibility of nutrient and peat additions to enhance the metabolic activity of bacteria within oil-contaminated sand beach sediments. Field trials were conducted with similar peat and nutrient concentrations in a north-temperate beach environment with weathered Scotian Light crude oil over a 138-day period. The rates of microbial respiration and productivity were enhanced significantly above unoiled and oiled control sediments with the addition of inorganic nutrients with and without peat amendments. Treatment of sediments with inorganic nutrients and peat did not increase the toxicity of the residual oil. Gas chromatography/mass spectroscopy analysis was used to quantify bioremediation success by normalizing the loss of individual components to the conserved marker 17?(H), 21?H)-hopane. While there is evidence of a stimulatory effect with the addition of peat, results suggest that nutrient availability in the interstitial water limited optimal rates of oil bioremediation.

Effect of Dispersants on Oil Biodegradation Under Simulated Marine Conditions

ABSTRACT A study was undertaken on the dispersion, microbial colonisation and biodegradation of chemically-dispersed weathered Forties crude oil under simulated marine conditions in laboratory microcosms. The measurements of droplet size, number and microbial colonisation were made using new techniques developed by the project team. Rapid growth of indigenous micro-organisms capable of degrading both crude oil and dispersants was observed in the presence of chemically-dispersed oil. These organisms colonised the dispersed oil and biodegraded the aliphatic and aromatic hydrocarbons. These processes was stimulated by the addition of inorganic nutrients. Some colonised droplets agglomerated into neutrally-buoyant “clusters” (100 µm- 2 mm diameter) consisting of oil, bacteria, protozoa, and nematodes. After substantial hydrocarbon biodegradation these clusters sank to the bottom of the microcosms. No biodegradation or cluster formation was noted in “killed” controls in which biological activity had been inhibited. Different dispersants promoted microbial growth to differing extents. These results suggest that the addition of dispersants can increase the rate of oil biodegradation under natural conditions by promoting the growth of indigenous hydrocarbon-degrading bacteria, as well as increasing the surface area of oil available for microbial colonisation.

Optimal Nitrate Concentration for the Biodegradation of n-Heptadecane in a Variably-Saturated Sand Column

Bioremediation of oil spills on beaches commonly involves the addition of nutrients (especially nitrogen and phosphorus) to stimulate the growth of indigenous oil-degrading bacteria. Very little information is available regarding the relationship between nutrient concentration and the rate of oil biodegradation. This information is necessary to design an appropriate nutrient delivery technology. We used continuous-flow beach microcosms containing heptadecane-coated sand (2.0 g per kg of dry sand) to evaluate the effect of nitrate concentration on the hydrocarbon biodegradation rate. Heptadecane biodegradation was determined by monitoring oxygen consumption and carbon dioxide production in the microcosms. The maximum biodegradation occurred at 2.5 mg nitrate-N l−1. Nitrogen recycling by the biomass was evidenced by the presence of microbial activity at zero influent nitrate concentration.

Bioremediation of Oil on Shoreline Environments: Development of Techniques and Guidelines

Abstract Over the last 20 years, the development of operational procedures to accelerate the natural biodegradation rates of oil spilled on shoreline environments has been the focus of numerous research programs. As a result, bioremediation has been demonstrated to be an effective oil spill countermeasure for use in cobble, sand beach, salt marsh, and mudflat environments. Today, studies are directed towards improving the efficacy and evaluating the ecological impacts of available bioremediation agents and/or procedures. This review describes the latest developments in bioremediation strategies and their key success factors.

Effectiveness of bioremediation for oil-polluted Antarctic seawater

The effectiveness of a specific fertiliser (INIPOL EAP 22) addition on bioremediation of oil-contaminated Antarctic coastal seawater was determined in the “Terre Adelie” area. Mesocosm studies were conducted to evaluate the effects of “Arabian light” crude oil contamination on coastal bacterioplanktonic communities. After oil addition, regular surveys of the bacterial changes of the oil-contaminated seawater were performed during 5-week periods during the austral summer of 1992/1993 and 1993/1994. All results (total, saprophytic and hydrocarbon-utilising bacterial abundance) clearly revealed a significant response of Antarctic bacterial communities to hydrocarbon contamination. A 1 order of magnitude increase of bacterial microflora occurred in seawater after crude oil contamination. A concomitant enrichment in oil-degrading bacteria was generally observed, from less than 0.001% of the community in uncontaminated samples to up to 50% after 3 weeks of contamination. Addition of fertiliser (INIPOL EAP 22) induced clear enhancement of both saprophytic and hydrocarbon-utilising microflora. Chemical analysis of the residual hydrocarbon fractions confirmed that fertiliser application increased the rate of oil biodegradation.

Weathering rates of oil components in a bioremediation experiment in estuarine sediments

The influence of the addition of a slow release fertiliser on the biodegradation rate of crude oil in experimental plots set up in the mid-tide sediments of an estuarine environment in the bay of Brest, France, was studied during a 9 month experiment. The weathering of total oil and fractions was monitored relative to the internal conservative biomarker 17α(H), 21β(H)-30-norhopane by computerised capillary gas-chromatography. At the end of the experiment, the biodegradation rates for total oil, aliphatics, cycloalkanes and aromatics were respectively 40±7, 83±6, 49±10 and 55±18%. The resins and asphaltenes were not degraded. No significant difference in biodegradation rates was observed between fertilised and non-fertilised plots, which was attributed to the high background level of N and P in the site under study. It is thought that if background level of N in the interstitial pore water of the sediment is ≥100μmoles litre−1 then bioremediation through fertilisation may be of limited use only.

THE EFFECT OF CLAY-OIL FLOCCULATION ON NATURAL OIL DEGRADATION

ABSTRACT Small-scale shaker flask experiments were conducted over 56 days with a weathered crude oil to investigate the significance of clay-oil flocculation processes on natural oil degradation rates. Clay-oil flocculation processes mediated the transfer of oil from solid surfaces into the aqueous phase where oil biodegradation rates are higher. As a result, within 7 days, 34% of the total n-alkanes (n-C12 to n-C35) were degraded in the oiled flasks containing mineral fines whereas no significant degradation was observed in flasks without mineral fines. After 56 days, only 25% and 48% of the n-alkane fraction remained in the flasks treated with and without mineral fines, respectively. No significant difference was observed between treatments for a selected number of 2-4 ring aromatic compounds. Microbiological results that showed an increase in the numbers of oil-degrading bacteria supported the results and conclusions derived from the chemical data.

BIOAUGMENTATION AND BIOSTIMULATION: A PARADOX BETWEEN LABORATORY AND FIELD RESULTS

ABSTRACT In both shaker-flask and mesocosm-scale experiments, a commercial oleophilic bioremediation agent containing biostimulation (nutrients) and bioaugmentation (bacterial inocula) properties was more effective in enhancing oil biodegradation rates than that of no treatment and/or periodic inorganic nutrient addition. However, similar results were not obtained from a subsequent 129-day field trial conducted in a sand beach environment. In this case, periodic additions of inorganic nutrients, with and without the commercial bioremediation agent, enhanced the number of heterotrophic bacteria and microbial respiration rates within the oiled sediments. The commercial product appeared to elevate the number of oil-degrading bacteria within the oiled sediment between days 17 and 89. However, the addition of inorganic nutrients alone, on a periodic basis, was the most effective means of enhancing the extent of oil biodegradation within the residual oil and of reducing sediment toxicity. By retaining residual oil and altering the physical and chemical characteristics of the treated sediment, the oleophilic product suppressed both the rate and extent of oil loss by tidal activity and biodegradation. This is not to say that the use of the product was ineffective in protecting the environment or was detrimental to it; the product does enhance natural biodegradation rates, and it limits the transport of beached oil to more sensitive areas. This study clearly illustrates the complexity associated with the selection of bioremediation agents, the need for improved experimental protocols for evaluating the performance and toxicity of bioremediation agents, and the potential of nutrient enrichment as a bioremediation strategy.

Field evaluations of marine oil spill bioremediation.

Bioremediation is defined as the act of adding or improving the availability of materials (e.g., nutrients, microorganisms, or oxygen) to contaminated environments to cause an acceleration of natural biodegradative processes. The results of field experiments and trials following actual spill incidents have been reviewed to evaluate the feasibility of this approach as a treatment for oil contamination in the marine environment. The ubiquity of oil-degrading microorganisms in the marine environment is well established, and research has demonstrated the capability of the indigenous microflora to degrade many components of petroleum shortly after exposure. Studies have identified numerous factors which affect the natural biodegradation rates of oil, such as the origin and concentration of oil, the availability of oil-degrading microorganisms, nutrient concentrations, oxygen levels, climatic conditions, and sediment characteristics. Bioremediation strategies based on the application of fertilizers have been shown to stimulate the biodegradation rates of oil in aerobic intertidal sediments such as sand and cobble. The ratio of oil loading to nitrogen concentration within the interstitial water has been identified to be the principal controlling factor influencing the success of this bioremediation strategy. However, the need for the seeding of natural environments with hydrocarbon-degrading bacteria has not been clearly demonstrated under natural environmental conditions. It is suggested that bioremediation should now take its place among the many techniques available for the treatment of oil spills, although there is still a clear need to set operational limits for its use. On the basis of the available evidence, we have proposed preliminary operational guidelines for bioremediation on shoreline environments.

Field evaluations of marine oil spill bioremediation.

Bioremediation is defined as the act of adding or improving the availability of materials (e.g., nutrients, microorganisms, or oxygen) to contaminated environments to cause an acceleration of natural biodegradative processes. The results of field experiments and trials following actual spill incidents have been reviewed to evaluate the feasibility of this approach as a treatment for oil contamination in the marine environment. The ubiquity of oil-degrading microorganisms in the marine environment is well established, and research has demonstrated the capability of the indigenous microflora to degrade many components of petroleum shortly after exposure. Studies have identified numerous factors which affect the natural biodegradation rates of oil, such as the origin and concentration of oil, the availability of oil-degrading microorganisms, nutrient concentrations, oxygen levels, climatic conditions, and sediment characteristics. Bioremediation strategies based on the application of fertilizers have been shown to stimulate the biodegradation rates of oil in aerobic intertidal sediments such as sand and cobble. The ratio of oil loading to nitrogen concentration within the interstitial water has been identified to be the principal controlling factor influencing the success of this bioremediation strategy. However, the need for the seeding of natural environments with hydrocarbon-degrading bacteria has not been clearly demonstrated under natural environmental conditions. It is suggested that bioremediation should now take its place among the many techniques available for the treatment of oil spills, although there is still a clear need to set operational limits for its use. On the basis of the available evidence, we have proposed preliminary operational guidelines for bioremediation on shoreline environments.

Evaluation of bioremediation agents in beach microcosms

A spill of weathered Arabian Light crude oil (3.7 kg m −2) on an intertidal sand zone was simulated in the laboratory. Respirometry, chemical and microbiological methods were employed to assess the effectiveness of two bioremediation agents: a slow-release inorganic fertilizer (Max Bac ®) and an oleophilic organic fertilizer (Inipol EAP22). Inipol EAP22 stimulated additional CO 2 evolution, increased both the total chemoheterotrophic population and the number of hydrocarbon-degrading microorganisms significantly, and increased the rate of mineralization of radiolabelled hexadecane. While the differences were not dramatic after 41 days of exposure, the residual oil extracted from the Inipol-treated sand was significantly more biodegraded (based on the application of the conserved biomarkers: phytane and 17α, 21β hopane) than that observed within the other sand columns. There was no evidence that Max Bac stimulated natural oil biodegradation rates relative to those observed in the control. These observations contrast with findings made previously in the field. The results suggest that differences in product formulations and their interaction with physical factors within sandy beach environments regulate nutrient release and persistence. These effects are significant factors in controlling the efficacy of bioremediation agents.

Effects of nitrogen source on crude oil biodegradation

The effects of NH4Cl and KNO3 on biodegradation of light Arabian crude oil by an oil-degrading enrichment culture were studied in respirometers. In poorly buffered sea salts medium, the pH decreased dramatically in cultures that contained NH4Cl, but not in those supplied with KNO3. The ammonia-associated pH decline was severe enough to completely stop oil biodegradation as measured by oxygen uptake. Regular adjustment of the culture pH allowed oil biodegradation to proceed normally. A small amount of nitrate accumulated in all cultures that contained ammonia, but nitrification accounted for less than 5% of the acid that was observed. The nitrification inhibitor, nitrapyrin, had no effect on the production of nitrate or acid in ammonia-containing cultures. When the culture pH was controlled, either by regular adjustment of the culture pH or by supplying adequate buffering capacity in the growth medium, the rate and extent of oil biodegradation were similar in NH4Cl- and KNO3-containing cultures. the lag time was shorter in pH-controlled cultures supplied with ammonia than in nitrate-containing cultures.

Effectiveness of bioremediation for the Exxon Valdez oil spill

The effectiveness of bioremediation for oil spills has been difficult to establish on dynamic, heterogeneous marine shorelines. A new interpretative technique used following the 1989 Exxon Valdez spill in Alaska shows that fertilizer applications significantly increased rates of oil biodegradation. Biodegradation rates depended mainly on the concentration of nitrogen within the shoreline, the oil loading, and the extent to which natural biodegradation had already taken place. The results suggest ways to improve the effectiveness of bioremediation measures in the future.

Biodegradation rates of crude oil in seawater

ABSTRACT: Measurements of the rate of biodegradation of crude oil in seawater in laboratory, mesocosm, and field systems from 16 published reports were reviewed and compared. Volumetric biodegradation rates range widely from approximately 0.01 to 1 000 gC/m3‐d. Laboratory studies report rates at the higher end of this range, while field and mesocosm studies, of which there are fewer, suggest much lower rates ranging from 0.01 to 0.3 gC/m3‐d. Possible explanations for the discrepancy between measurements made at different scales are differences in oil concentration and in mixing energy. When temperature‐scaled degradation rates from all systems are plotted versus initial oil concentration on a log‐log scale, the data are approximately linear (r2 = 0.86) over several orders of magnitude. The slope of the regressed line is near 1, indicating that the process can be interpreted as first order with respect to oil concentration. The half‐life for biodegradation is estimated to be approximately two months at 20°C. This analysis suggests that crude oil biodegradation in seawater is relatively slow and indicates that further research is required to bridge the gap between laboratory and field systems.

BIOREMEDIATION EFFECTIVENESS FOLLOWING THE EXXON VALDEZ SPILL

ABSTRACT Statistical analyses of changes in the composition of oil residues remaining on beaches following the Exxon Valdez oil spill in Prince William Sound have demonstrated that bioremediation was effective in accelerating oil removal. Extensive data were obtained in a joint bioremediation monitoring program conducted during the summer of 1990 by the U.S. Environmental Protection Agency (EPA), the State of Alaska, and Exxon. Composition changes in the oil relative to hopane, a trace oil component very resistant to biodegradation, provided the basis for accurately determining rates and extent of biodegradation. Results show that on fertilized beaches the rate of oil biodegradation was from three to more than five times faster than on adjacent, unfertilized control beaches. Further, most hydrocarbon components of the oil were biodegraded simultaneously, although at different rates. On one beach studied, about 60 percent of the total hydrocarbons detectable by gas chromatograph and 45 percent of the total PAH were biodegraded in three months. Bioremediation effectiveness was determined to depend primarily on the amount of nitrogen fertilizer delivered to the sediment per unit of oil present, time, and the extent of oil degradation prior to fertilizer application. The results suggest ways to improve future bioremediation application strategies and monitoring.

Microbial populations and hydrocarbon biodegradation potentials in fertilized shoreline sediments affected by the T/V Exxon Valdez oil spill.

The effort of clean up the T/V Exxon Valdez oil spill in Prince William Sound, Alaska, included the use of fertilizers to accelerate natural microbial degradation of stranded oil. A program to monitor various environmental parameters associated with this technique took place during the summer of 1990. Microbiological assays for numbers of heterotrophic and oil-degrading microbes and their hydrocarbon mineralization potentials were performed in support of this program. Fertilizer addition resulted in higher hexadecane and phenanthrene mineralization potentials on treated plots than on untreated reference plots. Microbial numbers in treated and reference surface sediments were not significantly different immediately after the first nutrient application in May 1990. However, subsurface sediments from treated plots had higher numbers of hydrocarbon degraders than did reference sediments shortly after treatment. The second application of fertilizer, later in summer, resulted in surface and subsurface increases in numbers of hydrocarbon degraders with respect to reference sediments at two of the three study sites. Elevated mineralization potentials, coupled with increased numbers of hydrocarbon degraders, indicated that natural hydrocarbon biodegradation was enhanced. However, these microbiological measurements alone are not sufficient to determine in situ rates of crude oil biodegradation.

Bioremediation as a technology: Experiences with the Exxon Valdez oil spill

The results from our oil spill bioremediation project have demonstrated convincingly that fertilizers can be applied to oiled beaches to overcome nutrient limitations, thereby enhancing biodegradation of the oil. In Prince William Sound, the natural biodegradation rate of oil on the beaches was found to be quite high, primarily because of small concentrations of ammonia and phosphate in seawater that are introduced into the beach material with each tide. However, the addition of fertilizers was capable of increasing this biodegradation as much as two to three fold above background activity. In addition, the extent of enhanced degradation was such that beaches became visually cleaner and aesthetically improved.

Bioremediation Technology Development and Application to the Alaskan Spill

ABSTRACT Bioremediation was used to clean oil-contaminated shorelines in Prince William Sound following the Exxon Valdez oil spill. Among the approaches considered for enhancing natural rates of oil biodegradation, nutrient applications became the principal focus. Bioremediation studies were conducted in a cooperative effort of Exxon, the U.S. Environmental Protection Agency, and scientists in academia. Field testing of nutriation of indigenous oil-eating microorganisms was conducted early in the summer of 1989, and full-scale application followed. Monitoring during the fall and winter of 1989–90 revealed the evident benefit of the technique and supported additional applications in 1990. The efficacy of bioremediation was demonstrated by measurement of numbers of hydrocarbon-degrading microorganisms, microbial hydrocarbon-degrading activities, and chemical changes in residual oil. This paper discusses laboratory and field programs demonstrating the efficacy and environmental safety of bioremediation, and reviews the materials and methods chosen for large-scale application.

Capacités dégradatives de bactéries et de champignons isolés d'un sol contaminé par un fuel

The long-term influence of a fuel spill on the bacterial and fungal communities of an agricultural soil was studied. Three years after the contamination, biodegradation of the fuel in the soil was achieved and after 5 years the residual compounds had no significant effect on the density and the specific composition of the microbial populations of the soil. Hydrocarbon-oxidizing bacteria Corynebacterium and Nocardia spp. were isolated. Most of the active fungi were Aspergillus and Penicillium spp., but strains of Paecilomyces, Acremonium, Fusarium, and Gliocladium were also identified. In laboratory experiments, the biodegradation rate of a reference crude oil by pure cultures of oil-degrading strains was nearly the same as in mixed cultures. The biodegradation potential of the strains isolated from the control plot was as high as strains isolated from the oiled plot. In the soil, as in laboratory cultures, the saturate hydrocarbons were more degraded than the aromatics, whereas the resins and asphaltenes were resistant to microbial attack, as were polycyclic alkanes steranes and triterpanes. Nocardia degraded preferentially the aromatics and attacked significantly the asphaltenes, as did Fusarium oxysporum. Aspergillus niger, Aspergillus flavus, and Fusarium oxysporum degraded part of the resins. The spectrum of the initial degradation of petroleum by the most active fungi and bacteria was identical, and it appears that the enzymatic equipment necessary to oxidize hydrocarbons is quite complete in these strains.

Quantitative studies on marine biodegradation of oil II. Effect of temperature

The rates of oil biodegradation, as judged by oxygen uptake, were com-pared at 14 and 4 °C, under conditions of continuous replenishment of nitrogen and phosphorus without high concentrations of either. A value of 2.7 was obtained for Q ' 10 (the ratio of oxidation rates at 14 and 4 °C per unit nitrogen uptake). This agrees with figures for Q 10 quoted for enriched culture conditions. The uptake of nitrogen and phosphorus was not reduced very markedly at lower temperatures and it is considered that nitrogen supply controls the rate of oxidation at 4 °C as it did at 14 °C. On this basis, tentative estimates of the biodegradative capacity of local seawater are made.