Robin L. Autenrieth

Degradation of petroleum hydrocarbons by facultative anaerobic bacteria under aerobic and anaerobic conditions

Abstract Nitrate-reducing bacterial strains ( Pseudomonas sp. BS2201, BS2203 and Brevibacillus sp. BS2202) isolated from petroleum-contaminated soil were capable of degrading petroleum hydrocarbons under aerobic and anaerobic conditions. Under aerobic conditions (a 10-day experiment in liquid media) the strains degraded 20–25% of the total extractable material (TEM), including up to 90–95% of all alkanes analyzed ( n -C 10 –C 35 ). Under anaerobic conditions (a 50-day experiment) these organisms degraded 15–18% of the TEM, 20–25% of some alkanes, and 15–18% of selected polycyclic aromatic hydrocarbons. The strains also degraded saturated hydrocarbons under anaerobic conditions in the absence of nitrates as electron acceptors.

Biodegradation of phenolic wastes

Phenolic biodegradation kinetics were determined in bioreactors with large solids retention times (SRT). Long term kinetic experiments were conducted in pulse-fed batch reactors for single substrate (phenol) and multiple substrates (combinations of glucose, phenol and pentachlorophenol). Short term initial rate experiments were also conducted on the single and multiple substrate reactors. Results indicate that phenol is metabolized at a maximum rate of 0.55 h−1 with a half saturation coefficient of 10 mg/1. Phenol concentrations in excess of 50 mg/1 inhibit the biodegradation rate. Our results also indicate that pentachlorophenol is cometabolized in the presence of phenol. It can be concluded that biodegradation of phenolic waste is a viable treatment option because the organisms, through their metabolic processes, reduced the waste concentrations below our detection limits.

MODELING COAGULATION KINETICS INCORPORATING FRACTAL THEORIES: A FRACTAL RECTILINEAR APPROACH

Abstract Conventional coagulation kinetic models are usually based on Smoluchowski’s work, which employs the coalesced sphere assumption. Much evidence, however, has recently been provided that particle aggregates from natural waters and engineered systems have fractal structures. Consequently, the traditional models should be modified to include the fractal nature of aggregates. This paper describes a modeling approach that simulates changes in particle size distribution (PSD) due to coagulation by incorporating recently proposed fractal mathematics and introducing a new conceptual framework called the coalesced fractal sphere (CFS) assumption. The developed modeling method, which includes the traditional Euclidean case as a subset, was applied to a 2-m settling column system with estuarine sediment particles, and a one-dimensional numerical model was developed. Model simulations were conducted varying the fractal dimension ( D F ) and the collision efficiency factor ( α ). For the conventional Euclidean case, the model indicated that coagulation played an important role in the vertical transport of the estuarine sediment particles. The simulations with the fractal cases indicated that both D F and α significantly affected the evolution of PSD, and that with lower values of D F and α , the model predicted a trend of PSD similar to that of the Euclidean case. This finding may be interpreted as dependence of α on the assumed collision models (or D F ), that seems to leave a new challenge to our understanding of α . The developed model may be used in various particle aggregation systems.

Biodegradation kinetics of select polycyclic aromatic hydrocarbon (PAH) mixtures by Sphingomonas paucimobilis EPA505

Many contaminated sites commonly have complex mixtures of polycyclic aromatic hydrocarbons (PAHs) whose individual microbial biodegradation may be altered in mixtures. Biodegradation kinetics for fluorene, naphthalene, 1,5-dimethylnaphthalene and 1-methylfluorene were evaluated in sole substrate, binary and ternary systems using Sphingomonas paucimobilis EPA505. The first order rate constants for fluorene, naphthalene, 1,5-dimethylnaphthalene, and 1-methylfluorene were comparable; yet Monod parameters were significantly different for the tested PAHs. S. paucimobilis completely degraded all the components in binary and ternary mixtures; however, the initial degradation rates of individual components decreased in the presence of competitive PAHs. Results from the mixture experiments indicate competitive interactions, demonstrated mathematically. The generated model appropriately predicted the biodegradation kinetics in mixtures using parameter estimates from the sole substrate experiments, validating the hypothesis of a common rate-determining step. Biodegradation kinetics in mixtures were affected by the affinity coefficients of the co-occurring PAHs and mixture composition. Experiments with equal concentrations of substrates demonstrated the effect of concentration on competitive inhibition. Ternary experiments with naphthalene, 1,5-dimethylnaphthalene and 1-methylfluorene revealed delayed degradation, where depletion of naphthalene and 1,5-dimethylnapthalene occurred rapidly only after the complete removal of 1-methylfluorene. The substrate interactions observed in mixtures require a multisubstrate model to account for simultaneous degradation of substrates. PAH contaminated sites are far more complex than even ternary mixtures; however these studies clearly demonstrate the effect that interactions can have on individual chemical kinetics. Consequently, predicting natural or enhanced degradation of PAHs cannot be based on single compound kinetics as this assumption would likely overestimate the rate of disappearance.

Microbial degradation of crude oil in marine environments tested in a flask experiment

Abstract Thirteen different bioremediation products were evaluated for their effectiveness in biodegrading petroleum hydrocarbons. All 13 products tested in this experiment were listed on the NCP product schedule. Of these 13 products, 12 were bioaugmentation agents and one was a biostimulation agent. All the products were tested for toxicity levels initially, using standardized protocols. The products were sampled and analyzed three times over a 28-day period for most-probable number (MPN) of hydrocarbon degraders and total petroleum hydrocarbon as separate fractions. A subsample was analyzed for MPN, and the rest of the sample was extracted and fractionated in total saturated petroleum hydrocarbons (TsPH) and total aromatic petroleum hydrocarbons (TarPH). This experiment revealed that the petroleum hydrocarbons were biodegraded to an extent significantly greater than that achieved by the naturally occurring microorganisms. After 28 days, some products reduced the TsPH fraction to 60% of its initial weight and the TarPH fraction to 65%. Three of the 13 products tested enhanced microbial degradation of the petroleum to a degree significantly better than the nutrient control treatments. Of these three products, only one showed a toxicity level below that of the control treatment.

Intrinsic bioremediation of a petroleum-impacted wetland

Following the 1994 San Jacinto River flood and oil spill in southeast Texas, a petroleum-contaminated wetland was reserved for a long-term research program to evaluate bioremediation as a viable spill response tool. The first phase of this program, presented in this paper, evaluated the intrinsic biodegradation of petroleum in the contaminated wetland. Sediment samples from six test plots were collected 11 times over an 11-month period to assess the temporal and spatial petroleum concentrations. Petroleum concentrations were evaluated using gas chromatography-mass spectrometer analyses of specific target compounds normalized to the conservative biological marker, C(30)17alpha,21beta(H)-hopane. The analyses of specific target compounds were able to characterize that significant petroleum biodegradation had occurred at the site over the one-year period. Total resolved saturate and total resolved aromatic hydrocarbon data indicated the petroleum was degraded more than 95%. In addition, first-order biodegradation rate constants were calculated for the hopane-normalized target compounds and supported expected biodegradation patterns. The rapid degradation rates of the petroleum hydrocarbons are attributed to conditions favorable to biodegradation. Elevated nutrient levels from the flood deposition and the unconsolidated nature of the freshly deposited sediment possibly provided a nutrient rich, oxic environment. Additionally, it is suggested that an active and capable microbial community was present due to prior exposure to petroleum. These factors provided an environment conducive for the rapid bioremediation of the petroleum in the contaminated wetland.

Arbuscular Mycorrhiza and Petroleum-Degrading Microorganisms Enhance Phytoremediation of Petroleum-Contaminated Soil

While plants can phytoremediate soils that are contaminated with petroleum hydrocarbons, adding microbes to remediate contaminated sites with petroleum-degrading microorganisms and arbuscular mycorrhizal fungi (AMF) is not well understood. The phytoremediation of Arabian medium crude oil (ACO) was done with a Lolium multiflorum system inoculated with an AMF (Glomus intraradices) and a mixture of petroleum-degrading microorganisms—the bacterium, Sphingomonas paucimobilis (Sp) and the filamentous fungus, Cunninghamella echinulata (Ce, SpCe)—or with a combination of microorganisms (AMF + SpCe). Based on an earlier study on screening plants for phytoremediation of ACO, L. multiflorum (Italian ryegrass) was selected for its tolerance and rapid growth response (Alarcón, 2006). The plants were exposed to ACO-contaminated soil (6000 mg kg−1) for 80 d under greenhouse conditions. A modified Long Ashton Nutrient Solution (LANS) was supplied to all treatments at 30 μg P mL−1, except for a second, higher P, control treatment at 44 μg P mL−1. Inoculation with AMF, SpCe, or AMF + SpCe resulted in significantly increased leaf area as well as leaf and pseudostem dry mass as compared to controls at 30 μg P mL−1. Populations of bacteria grown on a nitrogen-free medium and filamentous fungi increased with AMF + SpCe and SpCe treatments. The average total colonization and arbuscule formation of AMF-inoculated plants in ACO-contaminated soil were 25% and 8%, respectively. No adverse effects were caused by SpCe on AMFcolonization. Most importantly, ACOdegradation was significantly enhanced by the addition of petroleum-degrading microorganisms and higher fertility controls, as compared to plants at 30 μg P mL−1. The highest ACOdegradation (59%) was observed with AMF + SpCe. The phytoremediation of ACO was also enhanced by single inoculation of AMF or SpCe. The effect of AMF and petroleum-degrading microorganisms on plant growth and ACOdegradation was not attributable to differences in proline, total phenolics, nitrate reductase levels, or variation in plant–gas exchange.

Evolutionary toxicology: population-level effects of chronic contaminant exposure on the marsh frogs (Rana ridibunda) of Azerbaijan.

We used molecular methods and population genetic analyses to study the effects of chronic contaminant exposure in marsh frogs from Sumgayit, Azerbaijan. Marsh frogs inhabiting wetlands in Sumgayit are exposed to complex mixtures of chemical contaminants, including petroleum products, pesticides, heavy metals, and many other industrial chemicals. Previous results documented elevated estimates of genetic damage in marsh frogs from the two most heavily contaminated sites. Based on mitochondrial DNA (mtDNA) control region sequence data, the Sumgayit region has reduced levels of genetic diversity, likely due to environmental degradation. The Sumgayit region also acts as an ecological sink, with levels of gene flow into the region exceeding gene flow out of the region. Additionally, localized mtDNA heteroplasmy and diversity patterns suggest that one of the most severely contaminated sites in Sumgayit is acting as a source of new mutations resulting from an increased mutation rate. This study provides an integrated method for assessing the cumulative population impacts of chronic contaminant exposure by studying both population genetic and evolutionary effects.

Behavior of a chemically-dispersed oil and a whole oil on a near-shore environment

Abstract To investigate the use of dispersants as an oil spill chemical countermeasure in the surf-zone, a simulated oil spill was conducted at the Shoreline Environmental Research Facility (SERF), formerly known as the Coastal OilSpill Simulation System (COSS), a wave tank facility in Corpus Christi, Texas. Sand was added to each tank to establish a beach with a prescribed slope of 10 degrees. Natural seawater flowed continually through the system to emulate alongshore currents. The replicated experimental treatments included pre-mixed oil plus dispersant (three tanks), oil only (three tanks), and unoiled controls (two tanks). Known amounts of either whole oil or dispersed oil were added to the respective tanks. Both the sediment and water column were periodically sampled during the 10-day experiment, and a materials balance on the oil was determined for both oil treatments. The environmental compartments where oil accumulated were sediments, water column, and non-aqueous-phase layer. The discharge from the tanks was presumed to be the primary sink, as water was drawn from the tanks at a known and constant flow rate. Tidal cycles were simulated by varying the computer-controlled influent rate. The oil mass (measured as total petroleum hydrocarbons) for each compartment/sink was calculated using data from four time points. At the experiment’s conclusion, approximately 49% of the applied oil for the oiled treatment remained in the tanks sorbed to sediments or other surfaces. The rest of the oil was removed via the effluent. In the chemically-dispersed oil treatment, all of the oil was flushed from the tanks; no oil (≪1%) remained on the sediments. These studies indicate that a timely dispersant application to spilled oil can reduce residual oil accumulation on beach substrates.

Modeling coagulation kinetics incorporating fractal theories: comparison with observed data

There are currently four possible approaches in modeling coagulation kinetics: the traditional Euclidean rectilinear; the Euclidean curvilinear; the fractal rectilinear; and the fractal curvilinear. The fractal model includes the Euclidean case as a subset. The primary purpose of this research is to investigate which of the rectilinear models among these best predicts the evolution of experimental observed particle size distribution (PSD). Using a fractal rectilinear model previously developed by the authors, model predictions were compared with a series of observed PSD data obtained from estuarine sediment particles in a 2m settling column, where the average velocity gradient (G) was 20 or 40s(-1). Nonlinear parameter estimation was performed to estimate two free parameters for the fractal model (the fractal dimension, DF, and the collision efficiency factor, a), and one free parameter (the collision efficiency factor, alpha) for the Euclidean model. Compared with the observed PSD, the simulation showed that the fractal rectilinear model was best, and that this model fit better for the larger size particles. The estimated DF was between 2.6 and 3.0. The research demonstrated that the alphas have multiple values for the same observed data, depending on the coagulation model used. This finding is significant because a is currently used as a single value based on the conventional Euclidean rectilinear model.