Evaluation of bioremediation strategies of a controlled oil release in a wetland

A controlled petroleum release was conducted to evaluate bioremediation in a wetland near Houston, Texas. The 140-day study was conducted using a randomized, complete block design to test three treatments with six replicates per treatment. The three treatment strategies were inorganic nutrients, inorganic nutrients with an alternative electron acceptor, and a no-action oiled control. Samples were analyzed for petroleum chemistry and inorganic nutrients. These results are discussed in the context of our related research involving toxicology and microbiology at the site during the experiment. To evaluate biodegradation, the targeted compounds were normalized to the conservative compound C3017alpha, 21beta-[H]hopane, thus reducing the effects of spatial heterogeneity and physical transport. The two biostimulation treatments demonstrated statistically-higher rates of biodegradation than the oiled no-action control. For the majority of the experiment, target nutrient levels were maintained. Further research may be warranted to optimize these bioremediation strategies as well as evaluating additional treatment strategies for wetlands and other shoreline systems.     

Petroleum biodegradation and oil spill bioremediation

Hydrocarbon-utilizing microorganisms are ubiquitously distributed in the marine environment following oil spills. These microorganisms naturally biodegrade numerous contaminating petroleum hydrocarbons, thereby cleansing the oceans of oil pollutants. Bioremediation, which is accomplished by adding exogenous microbial populations or stimulating indigenous ones, attempts to raise the rates of degradation found naturally to significantly higher rates. Seeding with oil degraders has not been demonstrated to be effective, but addition of nitrogenous fertilizers has been shown to increase rates of petroleum biodegradation. In the case of the Exxon Valdez spill, the largest and most thoroughly studied application of bioremediation, the application of fertilizer (slow release or oleophilic) increased rates of biodegradation 3–5 times. Because of the patchiness of oil, an internally conserved compound, hopane, was critical for demonstrating the efficacy of bioremediation. Multiple regression models showed that the effectiveness of bioremediation depended upon the amount of nitrogen delivered, the concentration of oil, and time.     

In Situ Bioremediation of Toluene‐Polluted Vadose Zone: Integrated Column and Wetland Study

A vertical soil column setup integrated with wetlands is developed to study the biodegradation and transport of toluene, a light non‐aqueous phase liquid (LNAPL), in the subsurface environment. LNAPL‐contaminated water is applied to infiltrate from the top of the soil column. The observed and simulated breakthrough curves show high equilibrium concentration at top ports rather than at lower ports, indicating effective toluene biodegradation with soil depth. The observed equilibrium concentration of toluene is higher in the case of unplanted wetland, asserting an accelerated biodegradation rate in the planted case. A difference in the relative concentration of toluene between input and output fluxes at 100 h is found as 13.34% and 30.86% for planted and unplanted wetland setups, respectively. Estimated biodegradation rates show that toluene degradation is 2.5 times faster in the planted wetland setup. In addition, the difference in the observed bacterial count and dissolved oxygen prove that toluene degraded aerobically at a faster rate in the planted setup. Simulations show that as time reached 80–100 h, there is no significant change in concentration profile, thereby confirming the equilibrium condition. The results of this study will be useful to frame plant‐assisted bioremediation techniques for LNAPL‐contaminated soil–water resources in the field.     

Evaluation of two direct immunoassays for rapid detection of petroleum products on marine birds

To reduce rehabilitation time and improve survival, a practical, objective test is needed to determine if marine birds are contaminated with oil before they enter captivity. The RaPID Assays and EnviroGard immunoassays for detection of polycyclic aromatic hydrocarbons (PAHs) in soil were evaluated for their ability to detect petroleum on feather samples from 30 intermediate fuel oil contaminated and 30 uncontaminated common murres (Uria aalge). Sensitivity, specificity, positive and negative predictive value, precision, and time required to run each assay were determined. The RaPID Assays was 96.7% sensitive and specific, while the EnviroGard assay was 93.3% sensitive, and 90.0% specific. Sensitivity decreased at higher dilutions for both assays. Intra-replicate variation was less than 20%. Our evaluation showed that these immunoassays are rapid and cost-effective methods for detecting oil-contamination on the plumage of seabirds, with the EnviroGard assay being more practical in most oil spill response situations due to ease of use and rapidity of results.     

Temperature as a Tool to Evaluate Aerobic Biodegradation in Hydrocarbon Contaminated Soil

This study evaluates the theory, and some practical aspects of using temperature measurements to assess aerobic biodegradation in hydrocarbon contaminated soil. The method provides an easily applicable alternative for quantifying the rate of biodegradation and/or evaluating the performance of in situ remediation systems. The method involves two nonintrusive procedures for measuring vertical temperature profiles down existing monitoring wells; one using a thermistor on a cable for one‐time measurements and the other using compact temperature data loggers deployed for 3‐month to 1‐year period. These vertical temperature profile measurements are used to identify the depth and lateral extent of biodegradation as well as to monitor seasonal temperature changes throughout the year. The basic theory for using temperature measurements to estimate the minimum rate of biodegradation will be developed, and used to evaluate field measurements from sites in California where biodegradation of spilled petroleum hydrocarbons is due to natural processes. Following, temperature data will be used to evaluate the relative rates of biodegradation due to natural processes and soil vapor extraction (SVE) at a former refinery site in the North‐Central United States. The results from this study show that the temperature method can be a simple, cost effective tool for assessing biodegradation in the soil, and optimizing remediation systems at a wide variety of hydrocarbon spill sites.     

In situ bioventing of a diesel fuel spill

Abstract

An estimated 50 000 1 of diesel fuel contaminated soil over a depth of 1.5 to 3.5 m (approximately 1.5% by weight in the soil) following fuel recovery operations at the site of a diesel spill. Laboratory treatability identified oxygen supply treatment as having significant potential to enhance bioremediation of the soil in situ. A bioventing system was designed and tested on a quarter of the site. Venting alone over a period of six months reduced total hydrocarbon concentrations by 10 to 30% to a depth of 3 m. Venting with nutrient addition resulted in a further reduction of 30% over a subsequent 6 month period to the full depth of 3.5 m.     

Use of slow-release fertilizer and biopolymers for stimulating hydrocarbon biodegradation in oil-contaminated beach sediments

Nutrient concentration and hydrocarbon bioavailability are key factors affecting biodegradation rates of oil in contaminated beach sediments. The effect of a slow-release fertilizer, Osmocote, as well as two biopolymers, chitin and chitosan, on the bioremediation of oil-spiked beach sediments was investigated using an open irrigation system over a 56-day period under laboratory conditions. Osmocote was effective in sustaining a high level of nutrients in leached sediments, as well as elevated levels of microbial activity and rates of hydrocarbon biodegradation. Chitin was more biodegradable than chitosan and gradually released nitrogen into the sediment. The addition of chitin or chitosan to the Osmocote amended sediments enhanced biodegradation rates of the alkanes relative to the presence of Osmocote alone, where chitosan was more effective than chitin due to its greater oil sorption capacity. Furthermore, chitosan significantly enhanced the biodegradation rates of all target polycyclic aromatic hydrocarbons.     

Engineering and hydrogeological problems associated with in situ treatment

Abstract

Most organic materials that contaminate soil and the subsurface environment are readily degraded by natural biological processes. To this degree, in situ bioremediation can be thought of as a highly successful purification process. However, some organic molecules are naturally refractory to biodegradation, or other environmental factors induce molecular recalcitrance such as the absence of a proper microbial population or the presence of unsuitable environmental conditions. Examples of recalcitrant groundwater contaminants are soluble components of petroleum hydrocarbons (BTEX) and chlorinated aliphatic hydrocarbons (CAHs). Organic recalcitrance may be changed through introduction of degrading populations of microorganisms or by changing the environmental conditions through introduction of nutrients or other chemicals. The most significant engineering deficiency in in situ bioremediation is the absence of proven methods to introduce such materials into the subsurface environment for efficient mixing with microorganisms and the contaminants of concern.     

Demonstration of a Microbiologically Enhanced Vertical Ground Water Circulation Well Technology at a Superfund Site

A full-scale ground water circulation well (GCW) system was installed and operated to demonstrate in situ remediation of soil and ground water impacted with a mixture of chlorinated and nonchlorinated organic compounds at a Superfund site in upstate New York. System performance and applicability under site-specific conditions were evaluated based on the system's ability to meet the New York State Department of Environmental Conservation (NYSDEC) cleanup goals for target compounds in ground water and soil. Contaminants from the unsaturated zone were mobilized (volatilized) by one-way vacuum extraction, and treated via enhanced biodegradation (bioventing). In the saturated zone, contaminants were mobilized by soil flushing (solubilized) and treated by a combination of air stripping and biodegradation. An in situ aqueous phase bioreactor, and an ex situ gas phase bioreactor, were integrated into the system to enhance treatment via bioremediation. After 15 months of operation, the mass of target contaminants in soil and ground water combined had been reduced by 75%. Removal by biological mechanisms ranged from 35% to 56% of the total observed mass reduction. The in situ and the ex situ bioreactors mineralized 79% and 76%, respectively, of their target biodegradable contaminant loads. Results indicate that some mass reduction in target contaminants may have been from aerobic and aerobic processes within the circulation cell. Nonchlorinated compounds were relatively easy to mobilize (volatilize, solubilize, and/or transport) and treat when compared to chlorinated compounds. The data collected during the 15-month study indicate that remediation could be accomplished at the Sweden-3 Chapman site using the technology tested.     

Analytical approximation to characterize the performance of in situ aquifer bioremediation

The performance of in situ bioremediation to remove organic contaminants from contaminated aquifers depends on the physical and biochemical parameters. We characterize the performance by the contaminant removal rate and the region where biodegradation occurs, the biologically active zone (BAZ). The numerical fronts obtained by one-dimensional in situ bioremediation modeling reveal a traveling wave behavior: fronts of microbial mass, organic contaminant and electron acceptor move with a constant velocity and constant front shape through the domain. Hence, only one front shape and a linear relation between the front position and time is found for each of the three compounds. We derive analytical approximations for the traveling wave front shape and front position that agree perfectly with the traveling wave behavior resulting from the bioremediation model. Using these analytical approximations, we determine the contaminant removal rate and the BAZ. Furthermore, we assess the influence of the physical and biochemical parameters on the performance of the in situ bioremediation technique.     

BIOB: A mathematical model for the biodegradation of low solubility hydrocarbons

Modeling oil biodegradation is an important step in predicting the long term fate of oil on beaches. Unfortunately, existing models do not account mechanistically for environmental factors, such as pore water nutrient concentration, affecting oil biodegradation, rather in an empirical way. We present herein a numerical model, BIOB, to simulate the biodegradation of insoluble attached hydrocarbon. The model was used to simulate an experimental oil spill on a sand beach. The biodegradation kinetic parameters were estimated by fitting the model to the experimental data of alkanes and aromatics. It was found that parameter values are comparable to their counterparts for the biodegradation of dissolved organic matter. The biodegradation of aromatics was highly affected by the decay of aromatic biomass, probably due to its low growth rate. Numerical simulations revealed that the biodegradation rate increases by 3–4 folds when the nutrient concentration is increased from 0.2 to 2.0 mg N/L.     

Response of estuarine meio- and macrofauna to in situ bioremediation of oil-contaminated sediment

Numerous studies have demonstrated the efficacy of bioremediation for enhancing oil removal but the ecological effect on shoreline biota is unclear. Therefore, a field experiment was designed at an intertidal sandflat in SW England to assess the effects of nutrient addition to oiled sediments on meio- and macrofauna for a period of up to 45 weeks. Natural assemblages were exposed to different types of experimental treatments (no oil, oil alone, oil treated with slow-release fertiliser or liquid fertiliser). Bioremediation stimulated the microbial population and increased oil biodegradation. This, however, did not result in faster recolonisation rates of fertilised versus non-fertilised oiled sediments. Mild effects of oil and bioremediation treatments on benthic fauna were observed, including short-term shifts in dominance patterns. Decreased abundance of dominant species in the oiled compared to unoiled sediments resulted in significantly higher evenness of benthic assemblages within the first 11 weeks of the experiment.     

Evidence for Instantaneous Oxygen-Limited Biodegradation of Petroleum Hydrocarbon Vapors in the Subsurface

Petroleum hydrocarbon vapors biodegrade aerobically in the subsurface. Depth profiles of petroleum hydrocarbon vapor and oxygen concentrations from seven locations in sandy and clay soils across four states of Australia are summarized. The data are evaluated to support a simple model of biodegradation that can be used to assess hydrocarbon vapors migrating toward built environments. Multilevel samplers and probes that allow near‐continuous monitoring of oxygen and total volatile organic compounds (VOCs) were used to determine concentration depth profiles and changes over time. Collation of all data across all sites showed distinct separation of oxygen from hydrocarbon vapors, and that most oxygen and hydrocarbon concentration profiles were linear or near linear with depth. The low detection limit on the oxygen probe data and because it is an in situ measurement strengthened the case that little or no overlapping of oxygen and hydrocarbon vapor concentration profiles occurred, and that indeed oxygen and hydrocarbon vapors were largely only coincident near the location where they both decreased to zero. First‐order biodegradation rates determined from all depth profiles were generally lower than other published rates. With lower biodegradation rates, the overlapping of depth profiles might be expected, and yet such overlapping was not observed. A model of rapid (instantaneous) reaction of oxygen and hydrocarbon vapors compared to diffusive transport processes is shown to explain the important aspects of the 13 depth profiles. The model is simply based on the ratio of diffusion coefficients of oxygen and hydrocarbon vapors, the ratio of the maximum concentrations of oxygen and hydrocarbon vapors, the depth to the maximum hydrocarbon source concentration, and the stoichiometry coefficient. Whilst simple, the model offers the potential to incorporate aerobic biodegradation into an oxygen‐limited flux‐reduction approach for vapor intrusion assessments of petroleum hydrocarbon compounds.     

Development of oil hydrocarbon fingerprinting and identification techniques

Oil, refined product, and pyrogenic hydrocarbons are the most frequently discovered contaminants in the environment. To effectively determine the fate of spilled oil in the environment and to successfully identify source(s) of spilled oil and petroleum products is, therefore, extremely important in many oil-related environmental studies and liability cases. This article briefly reviews the recent development of chemical analysis methodologies which are most frequently used in oil spill characterization and identification studies and environmental forensic investigations. The fingerprinting and data interpretation techniques discussed include oil spill identification protocol, tiered analytical approach, generic features and chemical composition of oils, effects of weathering on hydrocarbon fingerprinting, recognition of distribution patterns of petroleum hydrocarbons, oil type screening and differentiation, analysis of “source-specific marker” compounds, determination of diagnostic ratios of specific oil constituents, stable isotopic analysis, application of various statistical and numerical analysis tools, and application of other analytical techniques. The issue of how biogenic and pyrogenic hydrocarbons are distinguished from petrogenic hydrocarbons is also addressed.     

Effect of Co‐culture and Nutrients Supplementation on Bioremediation of Crude Petroleum Sludge

Ex‐situ bioremediation of real‐field crude petroleum sludge was evaluated to elucidate the role of co‐culture (bioaugmentation) and external nutrients supplementation (biostimulation) under anaerobic microenvironment. Maximum removal of total petroleum hydrocarbons (TPH) was observed by integrating biostimulation with bioaugmentation (R5, 44.01%) followed by bioaugmentation alone (R4, 34.47%), co‐substrate supplemented operations [R6, 23.36%; R3, 16.5%; R2, 9.88%] and control (R1, 4.36%). Aromatics fraction showed higher degradation in all the conditions studied. Fate of six selected polycyclic aromatic hydrocarbons (PAHs) was evaluated during bioremediation. Among these, four ring PAHs compounds showed good degradation by integration of biostimulation with bioaugmentation (R5) while bioaugmentation alone (R4) documented good degradation of three ring PAHs. Lower ring PAHs compounds showed good degradation with the application of biostimulation (R6). Fluorescent in situ hybridization (FISH) detected the presence of known PAHs degrading microorganisms viz., Bacillus, Pseudomonas, Acido bacteria, Sulphur reducing bacteria Firmicutes, etc. Application of biostimulation and bioaugmentation strategies alone or in combinations documented noticeable influence on the degradation of petroleum sludge.     

巢湖沉积物柱样中正构烷烃初探

对巢湖湖心沉积物柱样样品的正构烷烃和有机碳进行了分析,利用正构烷烃碳数分布类型、L／H、OEP指标和有机碳数据,对该区近110年来正构烷烃的来源进行初步探讨。研究结果表明：21-25cm和16-20cm处正构烷烃以高等植物和低等生物输入并重;11．15cm即1952-1967年处具有外源性石油污染;从10cm开始,正构烷烃以细菌、藻类为代表的低等生物输人为主;尤其是1-5cm样品正构烷烃和TOC含量明显高值,表明该时期湖泊富营养化加剧。     

Differentiation of the Origins of BTX in Ground Water Using Multivariate Plots

Multivariate plots were utilized to create fingerprints of aromatic hydrocarbon residues in ground water. The technique allows hydrogeologists to distinguish between residues of benzene, toluene, ethyl benzene, and total xylenes originating from ground water contact with petroleum in natural deposits and refined petroleum waste products. Examples were taken from deep-well injection of refinery wastes, natural petroleum deposits, municipal and industrial landfill leachates, coal tar and creosote contaminated waters, and varnish industry contaminated ground water. The data were plotted from ASCII files generated through either Lotus 123™ or a database (The Manager™) report program, using a simple Fortran interactive program with Plot88™ subroutines.     

In Situ Bioreclamation: A Cost-Effective Technology to Remediate Subsurface Organic Contamination

In situ bioreclamation is a proven technology that cost-effectively treats organic contamination in subsurface environments. As a remediation strategy, it reduces both the contamination dissolved in ground water, as well as residual soil-bound contamination.
To maximize biodegradation, the technology is applied after conducting laboratory studies. Application of the technology involves infiltrating necessary nutrients to the contaminated subsurface.
Results of a specific case study indicate excellent performance with rapid cleanup of petroleum hydrocarbon contamination from soils and ground water.
Costs associated with in situ bioreclamation technology showed a savings of approximately 50 percent over simple pump-and-treat technology. Time frame for cleanup was shown to be approximately 30 percent of the projected time frame of simple pump-and-treat technology.     

Enhanced Degradation of Dissolved Benzene and Toluene Using a Solid Oxygen-Releasing Compound

A field lest to evaluate the applicability of an oxygon-releasing compound (ORC) to the rernediation of ground water contaminated with benzone and toluene was conducted in the Borden Aquifer in Ontario. Canada. Benzene and toluene were injected as organic substrates to represent BTEX compounds, bromide was used as a tracer, and nitrate was added to avoid nitrate-limited conditions.
The fate of the solutes was monitored along four lines of monitoring points and wells. Two lines studied the behavior of the solutes upgradient and downgradient of two large-diameter well screens filled with briquets containing ORC and briquets without ORC. One line was used to study the solute behavior upgradient and downgradient of columns of ORC powder placed directly in the saturated zone. The remaining line was a control.
The results indicate that ORC in both briquet and powder form can release significant amounts of oxygen to conlaminated ground water passing by it. In the formulation used in this work, oxygen release persisted for at least 10 weeks. Furthemiore, the study indicates that the enhancement of the available dissolved oxygen content of at least 4 mg/L each of the ground water by ORC can support biodegradation of benzene and toluene dissolved in ground water. Such concentrations are typical of those encountered at sites contaminated with petroleum hydrocarbons; therefore, these results suggest that there is promise for ORC to enhance in situ biodegradation of BTKX contaminants at such sites using passive (nonpumping) systems to contact the contaminated ground water with the oxygen source.     

Reduced Sediments: A Factor in the Design of Subsurface Oxidant Delivery Systems

A preliminary field performance evaluation of in situ bioremediation of a contaminated aquifer at the Libby, Montana, Superfund site, a former wood preserving site, was conducted for the Bioremediation Field Initiative sponsored by the U.S. Environmental Protection Agency (U.S. EPA). The current approach for site remediation involves injecting oxygen and nutrients into the aquifer to stimulate microbial degradation of target compounds that include polycyclic aromatic hydrocarbons and pentachlorophenol. The preliminary field evaluation determined that, in addition to the oxygen demand associated with the microbial oxidation of the organic contamination, uncontaminated aquifer sediments at the site are naturally reduced and also exert a significant oxygen demand. This conclusion is supported by three types of information: (1) analyses of ground water samples; (2) results from a field-scale tracer test; and (3) results of laboratory evaluations of oxygen use by reduced aquifer sediment samples. An estimate of the cost of supplying hydrogen peroxide to satisfy the oxygen demand of the uncontaminated reduced sediments is provided to demonstrate that the additional cost of oxidizing the reduced sediments could be significant. The presence of naturally occurring reduced sediments at a contamination site should be considered in the design of subsurface oxidant delivery systems.