Protozoa in Subsurface Sediments from Sites Contaminated with Aviation Gasoline or Jet Fuel

Numbers of protozoa in the subsurface of aviation gasoline and jet fuel spill areas at a Coast Guard base at Traverse City, Mich., were determined. Boreholes were drilled in an uncontaminated location, in contaminated but untreated parts of the fuel plumes, and in the aviation gasoline source area undergoing H₂O₂ biotreatment. Samples were taken from the unsaturated zone to depths slightly below the floating free product in the saturated zone. Protozoa were found to occur in elevated numbers in the unsaturated zone, where fuel vapors mixed with atmospheric oxygen, and below the layer of floating fuel, where uncontaminated groundwater came into contact with fuel. The same trends were noted in the biotreatment area, except that numbers of protozoa were higher. Numbers of protozoa in some contaminated areas equalled or exceeded those found in surface soil. The abundance of protozoa in the biotreatment area was high enough that it would be expected to significantly reduce the bacterial community that was degrading the fuel. Little reduction in hydraulic conductivity was observed, and no bacterial fouling of the aquifer was observed during biotreatment.     

Methodology for using contaminated soil leachability testing to determine soil cleanup levels at contaminated petroleum underground storage tank (UST) sites

The costs of environmental remediation at leaking petroleum underground storage tank (UST) sites are influenced significantly by soil cleanup levels. The use of conservative generic soil cleanup levels may be inappropriate at some sites contaminated by leaking petroleum USTs. At many contaminated sites, a primary objective of site remediation is long‐term protection of water resources (e.g., groundwater) from pollution. Leaching of pollutants from residual soil contamination to groundwater is a primary consideration in establishing site‐specific soil cleanup levels at fuel‐contaminated sites. The use of laboratory soil leachability testing methods may be useful in objectively evaluating the leaching potential of contaminants from residual soil contamination and estimating potential groundwater impacts. Developing soil cleanup levels that are protective of water resources must include a technically sound integration of site‐specific soil leachability data and contaminant attenuation factors. Evaluation of the leaching potentials of soil contaminants may also provide essential supplementary information for other site characterization methods that may be used to evaluate risks to human health. Contaminant leachability testing of soils may provide a cost‐effective and technically based method for determining soil cleanup levels that are protective of groundwater resources at contaminated petroleum UST sites.     

Fractional Fuzzy Simulation–Based Health Risk Assessment for Toluene Contaminated Aquifers

This article integrates a fractional fuzzy health risk approach with multi-objective analysis in consideration of multiple exposure pathways in order to assess human health risk in petroleum hydrocarbon (PH)–contaminated aquifers. A PH-contaminated groundwater aquifer located in the Pinggu District of Beijing, China, is then studied for demonstrating the applicability of the proposed approach. The results show that with more fuzzy parameters considered in the risk assessment procedure, the multi-parameter fuzzy (MPF) result is more accurate than that from the single-parameter fuzzy (SPF) model. The comparison results also indicate the advantage of the proposed fractional fuzzy approach in assessing parameter uncertainty. The non-carcinogenic risk assessment results imply that the contaminated groundwater in the study area is in the medium risk level, and remediation plans for soil and groundwater should be considered to ensure safe groundwater utilization.     

Petroleum-contaminated water treatment in a fluidized-bed bioreactor with immobilized Rhodococcus cells

Biotreatment of petroleum-contaminated water in a fluidized-bed bioreactor (FBB) is a relatively new and promising technology, which efficiency is strongly affected by the biocatalyst used. Our laboratory experiments involved biotreatment of the water contaminated with a synthetic petroleum mixture consisting of aliphatic and polyaromatic hydrocarbons (PAHs) using a continuous column bioreactor with recycle. Different type biocatalysts were tested, including Rhodococcus bacteria immobilized in hydrophobized carriers such as sawdust, poly(vinyl alcohol) cryogel (cryoPVA) and poly(acrylamide) cryogel (cryoPAAG). Biocatalyst abilities to oxidize petroleum hydrocarbons were evaluated using the Columbus Micro-Oxymax^® respirometer. The hydrophobized sawdust-supported biocatalyst demonstrated substantially higher metabolic activity than C₁₂-cryoPAAG-based biocatalyst due to larger number of immobilized Rhodococcus cells and, therefore, had benefits for application in FBBs. The obtained results showed that designed FBB process is successful, providing 70–100% removal of n-alkanes (C₁₀–C₁₉) and 66–70% removal of 2–3-ring PAHs from contaminated water after 2–3 weeks.     

Treatment of Groundwater Contaminated with PAHs, Gasoline Hydrocarbons, and Methyl tert-butyl Ether in a Laboratory Biomass-Retaining Bioreactor

In this study, we investigated the treatability of co-mingled groundwater contaminated with polycyclic aromatic hydrocarbons (PAHs), gasoline hydrocarbons, and methyl tert-butyl ether (MtBE) using an ex-situ aerobic biotreatment system. The PAHs of interest were naphthalene, methyl-naphthalene, acenaphthene, acenaphthylene, and carbazole. The gasoline hydrocarbons included benzene, toluene, ethyl benzene, and p-xylene (BTEX). Two porous pot reactors were operated for a period of 10 months under the same influent contaminant concentrations. The contaminated groundwater was introduced into the reactors at a flow rate of 4 and 9 l/day, resulting in a hydraulic retention time (HRT) of 32 and 15 h, respectively. In both reactors, high removal efficiencies were achieved for the PAHs (>99%), BTEX and MtBE (>99.7%). All the PAHs of interest and the four BTEX compounds were detected at concentrations less than 1 μg/l throughout the study duration. Effluent MtBE from both reactors was observed at higher levels; nevertheless, its concentration was lower than the 5 μg/l Drinking Water Advisory for MtBE implemented in California.     

Assessment of in-situ bioremediation at a refinery waste-contaminated site and an aviation gasoline contaminated site

A combination of geochemical, microbiological and isotopic methods were used to evaluate in-situ bioremediation of petroleum hydrocarbons at one site contaminated with refinery waste and a second site contaminated with aviation gasoline at Alameda Point, California. At each site, geochemical and microbiological characteristics from four locations in the contaminated zone were compared to those from two uncontaminated background locations. At both sites, the geochemical indicators of in-situbiodegradation includeddepleted soil gas and groundwater oxygen, elevated groundwater alkalinity, and elevated soil gas carbon dioxide and methane in the contaminated zone relative to the background. Radiocarbon content of methane and carbon dioxide measured in soil gas at both sites indicated that they were derived from hydrocarbon contaminant degradation. Direct microscopy of soil core samples using cell wall stains and activity stains, revealed elevated microbial numbers and enhanced microbial activities in contaminated areas relative to background areas, corroborating geochemical findings. While microbial plate counts and microcosm studies using soil core samples provided laboratory evidence for the presence of some microbial activity and contaminant degradation abilities, they did not correlate well with either contaminant location, geochemical, isotopic, or direct microscopy data.     

Monitoring the Effect of Poplar Trees on Petroleum-Hydrocarbon and Chlorinated-Solvent Contaminated Ground Water

At contaminated groundwater sites, poplar trees can be used to affect ground-water levels, flow directions, and ultimately total groundwater and contaminant flux to areas downgradient of the trees. The magnitude of the hydrologic changes can be monitored using fundamental concepts of groundwater hydrology, in addition to plant physiology-based approaches, and can be viewed as being almost independent of the contaminant released. The affect of poplar trees on the fate of groundwater contaminants, however, is contaminant dependent. Some petroleum hydrocarbons or chlorinated solvents may be mineralized or transformed to innocuous compounds by rhizospheric bacteria associated with the tree roots, mineralized or transformed by plant tissues in the transpiration stream or leaves after uptake, or passively volatilized and rapidly dispersed or oxidized in the atmosphere. These processes also can be monitored using a combination of physiological- or geochemical-based field or laboratory approaches. When combined, such hydrologic and contaminant monitoring approaches can result in a more accurate assessment of the use of poplar trees to meet regulatory goals at contaminated groundwater sites, verify that these goals continue to be met in the future, and ultimately lead to a consensus on how the performance of plant-based remedial strategies (phytoremediation) is to be assessed.     

Biotechnological Potential of Bacillus salmalaya 139SI: A Novel Strain for Remediating Water Polluted with Crude Oil Waste

Environmental contamination by petroleum hydrocarbons, mainly crude oil waste from refineries, is becoming prevalent worldwide. This study investigates the bioremediation of water contaminated with crude oil waste. Bacillus salamalaya 139SI, a bacterium isolated from a private farm soil in the Kuala Selangor in Malaysia, was found to be a potential degrader of crude oil waste. When a microbial population of 10⁸ CFU ml^-1 was used, the 139SI strain degraded 79% and 88% of the total petroleum hydrocarbons after 42 days of incubation in mineral salt media containing 2% and 1% of crude oil waste, respectively, under optimum conditions. In the uninoculated medium containing 1% crude oil waste, 6% was degraded. Relative to the control, the degradation was significantly greater when a bacteria count of 99 × 10⁸ CFU ml^-1 was added to the treatments polluted with 1% oil. Thus, this isolated strain is useful for enhancing the biotreatment of oil in wastewater.     

Emerging high-throughput approaches to analyze bioremediation of sites contaminated with hazardous and/or recalcitrant wastes

Sustainable development requires the promotion of environmental management and a constant search for new technologies to treat a wide range of aquatic and terrestrial habitats contaminated by increasing anthropogenic activities. Bioremediation, i.e. the elimination of natural or xenobiotic pollutants by living organisms, is an environmentally friendly and cost-effective alternative to physico-chemical cleanup options. However, the strategy and outcome of bioremediation in open systems or confined environments depend on a variety of physico-chemical and biological factors that need to be assessed and monitored. In particular, microorganisms are key players in bioremediation applications, yet their catabolic potential and their dynamics in situ remain poorly characterized. To perform a comprehensive assessment of the biodegradative potential of a contaminated site and efficiently monitor changes in the structure and activities of microbial communities involved in bioremediation processes, sensitive, fast and large-scale methods are needed. Over the last few years, the scientific literature has revealed the progressive emergence of genomic high-throughput technologies in environmental microbiology and biotechnology. In this review, we discuss various high--throughput techniques and their possible--or already demonstrated-application to assess biotreatment of contaminated environments.     

Biodegradation of creosote and pentachlorophenol in contaminated groundwater: chemical and biological assessment

Shake flask studies examined the rate and extent of biodegradation of pentachlorophenol (PCP) and 42 components of coal-tar creosote present in contaminated groundwater recovered from the American Creosote Works Superfund site, Pensacola, Fla. The ability of indigenous soil microorganisms to remove these contaminants from aqueous solutions was determined by gas chromatographic analysis of organic extracts of biotreated groundwater. Changes in potential environmental and human health hazards associated with the biodegradation of this material were determined at intervals by Microtox assays and fish toxicity and teratogenicity tests. After 14 days of incubation at 30 degrees C, indigenous microorganisms effectively removed 100, 99, 94, 88, and 87% of measured phenolic and lower-molecular-weight polycyclic aromatic hydrocarbons (PAHs) and S-heterocyclic, N-heterocyclic, and O-heterocyclic constituents of creosote, respectively. However, only 53% of the higher-molecular-weight PAHs were degraded; PCP was not removed. Despite the removal of a majority of the organic contaminants through biotreatment, only a slight decrease in the toxicity and teratogenicity of biotreated groundwater was observed. Data suggest that toxicity and teratogenicity are associated with compounds difficult to treat biologically and that one may not necessarily rely on indigenous microorganisms to effectively remove these compounds in a reasonable time span; to this end, alternative or supplemental approaches may be necessary. Similar measures of the toxicity and teratogenicity of treated material may offer a simple, yet important, guide to bioremediation effectiveness.     

Biodegradation of creosote and pentachlorophenol in contaminated groundwater: chemical and biological assessment.

Shake flask studies examined the rate and extent of biodegradation of pentachlorophenol (PCP) and 42 components of coal-tar creosote present in contaminated groundwater recovered from the American Creosote Works Superfund site, Pensacola, Fla. The ability of indigenous soil microorganisms to remove these contaminants from aqueous solutions was determined by gas chromatographic analysis of organic extracts of biotreated groundwater. Changes in potential environmental and human health hazards associated with the biodegradation of this material were determined at intervals by Microtox assays and fish toxicity and teratogenicity tests. After 14 days of incubation at 30 degrees C, indigenous microorganisms effectively removed 100, 99, 94, 88, and 87% of measured phenolic and lower-molecular-weight polycyclic aromatic hydrocarbons (PAHs) and S-heterocyclic, N-heterocyclic, and O-heterocyclic constituents of creosote, respectively. However, only 53% of the higher-molecular-weight PAHs were degraded; PCP was not removed. Despite the removal of a majority of the organic contaminants through biotreatment, only a slight decrease in the toxicity and teratogenicity of biotreated groundwater was observed. Data suggest that toxicity and teratogenicity are associated with compounds difficult to treat biologically and that one may not necessarily rely on indigenous microorganisms to effectively remove these compounds in a reasonable time span; to this end, alternative or supplemental approaches may be necessary. Similar measures of the toxicity and teratogenicity of treated material may offer a simple, yet important, guide to bioremediation effectiveness.     

Measurement of Oxygen Demand of Petroleum Hydrocarbon-Contaminated Groundwater

The standard biological oxygen demand (BOD) test was modified for application to petroleum hydrocarbon-contaminated groundwater. The goal was to assess the potential oxygen demand of plume constituents as part of a field trial investigating oxygen-enhanced in situ bioremediation. Modifications to standard BOD protocol included the use of an adapted microbial population developed from site groundwater and methods to minimize both the loss of volatile compounds and the exposure of samples to air. Results from this study indicated that the measured oxygen demand was significantly greater than the oxygen demand estimated solely by stoichiometric calculations from the concentrations of the analytes of typical regulatory concern, that is, benzene, toluene, ethylbenzene, and xylenes (BTEX). This is not surprising, because the petroleum hydrocarbon sources typically contain many organic contaminants other than BTEX, as well as potentially oxidizable natural dissolved organic matter and inorganic species typically present in hydrocarbon plumes. However, in practice, estimation of the total oxygen demand of a contaminated groundwater by exhaustive analyses of all oxidizable or aerobically degradable species typically will be infeasible. The modified BOD test may be a simple, low-cost, useful tool when assessing the potential for natural attenuation by aerobic biodegradation or designing methods to supply oxygen for enhanced aerobic bioremediation.     

Enhancing Degradation of Total Petroleum Hydrocarbons and Uptake of Heavy Metals in a Wetland Microcosm Planted with Phragmites Communis by Humic Acids Addition

The effects of humic acid (HA) on heavy-metal uptake by plants and degradation of total petroleum hydrocarbons (TPHs) in a wetland microcosm planted with Phragmites communis were evaluated by comparing waterlogged soils and water-drained upland soils. Experiments were conducted on soils artificially contaminated with heavy metals (Pb, Cu, Cd, Ni) and diesel fuel. HA showed a positive influence on biomass increase for all conditions, but more for belowground than aboveground biomass, and lower in contaminated than uncontaminated soil. The bioavailability and leachability factor (BLF) for all heavy metals except Ni increased with HA addition in both the control and the P. communis planted microcosms, suggesting that more heavy metals could be potentially phytoavailable for plant uptake. Microbial activities were not affected by both heavy metals and TPH contamination, and HA effects on stimulating microbial activities were much greater in the contaminated soil than under uncontaminated conditions. HA addition enhanced the degradation of TPH and n-alkane in waterlogged conditions. The results show that HA can increase the remedial performance in P. communis dominated wetlands simultaneously contaminated with heavy metals and petroleum hydrocarbons and thus prevent contamination of groundwater or other adjacent ecosystems.     

Comparative Mesocosm Study of Biostimulation Efficiency in Two Different Oil-Amended Sub-Antarctic Soils

Biological treatment has become increasingly popular as a remediation method for soils and groundwater contaminated with petroleum hydrocarbon, chlorinated solvents, and pesticides. Bioremediation has been considered for application in cold regions such as Arctic and sub-Arctic climates and Antarctica. Studies to date suggest that indigenous microbes suitable for bioremediation exist in soils in these regions. This paper reports on two case studies at the sub-Antarctic Kerguelen Island in which indigenous bacteria were found that were capable of mineralizing petroleum hydrocarbons in soil contaminated with crude oil and diesel fuel. All results demonstrate a serious influence of the soil properties on the biostimulation efficiency. Both temperature elevation and fertilizer addition have a more significant impact on the microbial assemblages in the mineral soil than in the organic one. Analysis of the hydrocarbons remaining at the end of the experiments confirmed the bacterial observations. Optimum temperature seems to be around 10 degrees C in organic soil, whereas it was higher in mineral soil. The benefit of adding nutrients was much stronger in mineral than in the organic soil. Overall, this study suggests that biostimulation treatments were driven by soil properties and that ex situ bioremediation for treatment of cold contaminated soils will allow greater control over soil temperature, a limiting factor in cold climates.     

Performance of Deep-Rooted Phreatophytic Trees at a Site Containing Total Petroleum Hydrocarbons

Poplar and willow tree stands were installed in 2003 at a site in Raleigh, North Carolina containing total petroleum hydrocarbon – contaminated groundwater. The objective was groundwater uptake and plume control. The water table was 5 to 6 m below ground surface (bgs) and therefore methods were used to encourage deep root development. Growth rates, rooting depth and sap flow were measured for trees in Plot A located in the center of the plume and in Plot B peripheral to the plume. The trees were initially sub-irrigated with vertically installed drip-lines and by 2005 had roots 4 to 5 m bgs. Water balance calculations suggested groundwater uptake. In 2007, the average sap flow was higher for Plot B (～59 L per day per tree) than for Plot A (～23 L per day per tree), probably as a result of TPH-induced stress in Plot A. Nevertheless, the estimated rate of groundwater uptake for Plot A was sufficient, relative to the calculated rate of groundwater flux beneath the stand, that a high level of plume control was achieved based on MODFLOW modeling results. Down-gradient groundwater monitoring wells installed in late 2011 should provide quantitative data for plume control.     

Bioremediation of Crude Oil-Contaminated Soil Using Slurry-Phase Biological Treatment and Land Farming Techniques

Field-scale experiments on bioremediation of soil heavily contaminated with crude oil were undertaken on the territory of the Kokuyskoye oil field (Perm region, West Urals, Russia) owned by the LUKOIL Company. The pollution consisted of the contents of a oil waste storage pit, which mostly received soils contaminated after accidental oil spills and also the solid n-alkane (paraffin) wastes removed from the surface of drilling equipment. Laboratory analyses of soil samples indicated contamination levels up to 200?g/kg of total recoverable petroleum hydrocarbons (TRPH). Average oil composition consisted of 64% aliphatics, 25% aromatics, 8% heterocyclics, and 3% of tars/asphaltenes. Ex situ bioremediation techniques involved the successive treatment of contaminated soil using a bioslurry reactor and land farming cells. An oleophilic biofertilizer based on Rhodococcus surfactant complexes was used in both treatment systems. An aerobic slurry bioreactor was designed, and the biofertilizer applied weekly. Slurry-phase biotreatment of the contaminated soil resulted in an 88% reduction in oil concentration after 2 months. The resulting reactor product, containing approximately 25?g/kg of TRPH, was then loaded into land farming cells for further decontamination. To enhance bioremediation, different treatments (e.g., soil tilling, bulking with woodchips, watering, and biofertilizer addition) were used. The rates of oil biodegradation were 300 to 600?ppm/day. As a result, contamination levels dropped to 1.0 to 1.5?g/kg of TRPH after 5 to 7 weeks. Tertiary soil management involved phytoremediation where land farming cells were seeded with a mixture of three species of perennial grass. The effect of phytoremediation on the residual decontamination and rehabilitation of soil fertility is being evaluated.     

Isolation and characterisation of polychlorinated biphenyl (PCB) degrading fungi from a historically contaminated soil

Background  

Polychlorinated biphenyls (PCBs) are widespread toxic pollutants. Bioremediation might be an effective, cost competitive and environment-friendly solution for remediating environmental matrices contaminated by PCBs but it is still unsatisfactory, mostly for the limited biodegradation potential of bacteria involved in the processes. Very little is known about mitosporic fungi potential in PCB bioremediation and their occurrence in actual site historically contaminated soils. In the present study, we characterised the native mycoflora of an aged dump site soil contaminated by about 0.9 g kg^-1 of Aroclor 1260 PCBs and its changing after aerobic biotreatment with a commercial complex source of bacteria and fungi. Fungi isolated from the soil resulting from 120 days of treatment were screened for their ability to adsorb or metabolise 3 target PCBs.     

Intensification of the aerobic bioremediation of an actual site soil historically contaminated by polychlorinated biphenyls (PCBs) through bioaugmentation with a non acclimated, complex source of microorganisms

Background  

The biotreatability of actual-site polychlorinated biphenyl (PCB)-contaminated soils is often limited by their poor content of autochthonous pollutant-degrading microorganisms. In such cases, inoculation might be the solution for a successful bioremediation. Some pure and mixed cultures of characterized PCB degrading bacteria have been tested to this purpose. However, several failures have been recorded mostly due to the inability of inoculated microbes to compete with autochthonous microflora and to face the toxicity and the scarcity of nutrients occurring in the contaminated biotope. Complex microbial systems, such as compost or sludge, normally consisting of a large variety of robust microorganisms and essential nutrients, would have better chances to succeed in colonizing degraded contaminated soils. However, such sources of microorganisms have been poorly applied in soil bioremediation and in particular in the biotreatment of soil with PCBs. Thus, in this study the effects of Enzyveba, i.e. a consortium of non-adapted microorganisms developed from composted material, on the slurry- and solid-phase aerobic bioremediation of an actual-site, aged PCB-contaminated soil were studied.     

Fluorescence in situ hybridization (CARD-FISH) of microorganisms in hydrocarbon contaminated aquifer sediment samples

Groundwater ecosystems are the most important sources of drinking water worldwide but they are threatened by contamination and overexploitation. Petroleum spills account for the most common source of contamination and the high carbon load results in anoxia and steep geochemical gradients. Microbes play a major role in the transformation of petroleum hydrocarbons into less toxic substances. To investigate microbial populations at the single cell level, fluorescence in situ hybridization (FISH) is now a well-established technique. Recently, however, catalyzed reporter deposition (CARD)-FISH has been introduced for the detection of microbes from oligotrophic environments. Nevertheless, petroleum contaminated aquifers present a worst case scenario for FISH techniques due to the combination of high background fluorescence of hydrocarbons and the presence of small microbial cells caused by the low turnover rates characteristic of groundwater ecosystems. It is therefore not surprising that studies of microorganisms from such sites are mostly based on cultivation techniques, fingerprinting, and amplicon sequencing. However, to reveal the population dynamics and interspecies relationships of the key participants of contaminant degradation, FISH is an indispensable tool. In this study, a protocol for FISH was developed in combination with cell quantification using an automated counting microscope. The protocol includes the separation and purification of microbial cells from sediment particles, cell permeabilization and, finally, CARD-FISH in a microwave oven. As a proof of principle, the distribution of Archaea and Bacteria was shown in 60 sediment samples taken across the contaminant plume of an aquifer (Leuna, Germany), which has been heavily contaminated with several ten-thousand tonnes of petroleum hydrocarbons since World War II.     

Review of chemical,physical, and toxicologic properties of components of total petroleum hydrocarbons

Risk is a function of exposure and hazard, and both aspects must be incorporated into sound risk assessment efforts. However, risk assessment for sites contaminated with petroleum products is complicated by a general lack of information relevant to exposure to and toxicity of petroleum mixtures (especially total petroleum hydrocarbons, or TPH). Specifically, there is often inadequate information about the components of the TPH present at the site and the physical and chemical properties and toxicities of these components. Such information is crucial to developing a strong conceptual model of exposure to and risk from petroleum hydrocarbons at contaminated sites. This article presents information that can be incorporated into risk assessments for sites contaminated with petroleum hydrocarbons.