Petroleum Hydrocarbons In Groundwater Research Articles

Degrading characteristics of oil‐degrading bacteria and its study of petroleum hydrocarbon metabolites

AbstractExploring the community characteristics of petroleum degrading bacteria and revealing the types of petroleum metabolites produced by degrading bacteria play an important role in solving the problem of oil pollution. In this study, the bacterial suspension was extracted from the sludge of the sewage treatment plant, and the efficient dominant bacteria were enriched and cultured by microbial screening. The optimal environmental conditions and kinetic behavior of microbial degradation of petroleum hydrocarbons in groundwater were discussed, and the metabolites of microbial degradation of petroleum hydrocarbons were analyzed. The results showed that the optimum degradation conditions of the strain were as follows: bacterial suspension inoculum: 2%, pH: 7, temperature: 30°C, initial concentration of contaminated water sample: 500 mg/L. Under these conditions, the microbial petroleum hydrocarbon degradation efficiency was 84.7% and followed the first‐order kinetics; qualitative and quantitative statistical analysis of the metabolites of the microbial degradation of petroleum hydrocarbons by gas chromatography‐time‐of‐flight mass spectrometry was performed. A total of 10 significantly upregulated products and 12 significantly downregulated products were screened, which were significantly different from the metabolites of the control group. Further microbial community analysis showed that Pseudomonas was dominant in the bacterial suspension, more than 99.5%, which was significantly different from the sludge sample, providing data support for the degradation of petroleum hydrocarbons by Pseudomonas. This study has provided a scientific basis for in situ remediation of petroleum pollution in groundwater.

Adsorption of total petroleum hydrocarbon in groundwater by KOH-activated biochar loaded double surfactant-modified nZVI

Introduction: Crude oil and petroleum hydrocarbon contamination is commonly found in the soil and groundwater during the various processes of mining, processing, and utilization due to issues such as inefficient environmental management, random wastewater discharge, and storage tank leakage.To address this issue, we will use corn stalk biochar (SBC) and surfactants to improve the stability and chemical reactivity of nZVI, thereby enhancing its ability to remove pollutants, and explore the adsorption effect and mechanism of composite materials for petroleum hydrocarbons.Methods: Modified corn stalk biochar (SBC) was synthesized through high-temperature carbonization and KOH activation. Subsequently, the iron/carbon composite PN-nZVI@SBC (PNMSBC) was prepared by loading nano zero-valent iron modified with dual surfactants, and it was adopted to adsorb total petroleum hydrocarbons(TPH) in groundwater. The physical and chemical properties, surface patterns, and elemental mapping of PNMSBC particles were analyzed using SEM, EDS, TEM,XRD, BET, and FTIR spectroscopy. Kinetics and isotherm tests were performed to evaluate the adsorption properties of the composites. TPH adsorption was dependent on ionic strength, initial TPH concentration, as well as pH. The adsorption mechanism combining XPS and EPR spectroscopy was explored.Results: The characterization results by SEM and TEM showed that the particle size of nZVI particles modified by surfactants became smaller, and the dispersibility was enhanced. The characterization results by XRD and FTIR confirmed the successful preparation of the composites. The BET results showed that MSBC and PNMSBC were mesoporous structures. The characterization results indicated that Polyvinylpyrrolidone (PVP) and Sodium oleate (NaOA) inhibited the oxidation of nZVI while effectively improving its reactivity. The result of the experiments on adsorption showed that the removal of TPH by PNMSBC followed Freundlich isotherm and pseudo-second-order kinetic models, thus suggesting that the main adsorption processes comprise chemisorption and multilayer heterogeneous adsorption. The adsorption capacity of PNMSBC was increased by the abundance of macro and microporous structures. To be specific, a maximum Langmuir adsorption capacity (qm) was achieved as 75.26 g/g. The result of batch experiments indicated that PNMSBC continuously removed considerable TPH under a wide pH range from 2 to 6. The adsorption mechanism of PNMSBC includes surface adsorption, oxidation, complexation, and electrostatic interaction.Discussion: In brief, PNMSBC has a promising application for the adsorption of TPH in groundwater remediation.

In Situ Anaerobic Bioremediation of Petroleum Hydrocarbons in Groundwater of Typical Contaminated Site in Shanghai, China: A Pilot Study

In situ anaerobic treatment is an effective and sustainable method for petroleum hydrocarbon (PHC)-contaminated groundwater remediation. In this study, application of a formerly screened microbial ...

Application of a genetic algorithm to groundwater pollution source identification

The accurate identification of groundwater pollution sources is the key to site remediation and management, which directly relates to the cost and effect of remediation during later periods. Studying the identification of some small-area site pollution sources by using a small amount of groundwater monitoring data is difficult and is currently a hot topic in the field of groundwater management. In this study, a method combining the Advection-Dispersion Equation (ADE) of contaminants in groundwater with Genetic Algorithm (GA) was proposed to identify groundwater pollution sources, that is, the location of the pollution source, the time of pollution release, and the intensity of pollution release. A sandbox experiment for the migration and transformation of deterministic petroleum hydrocarbons in groundwater is designed to verify the method. The results show that the method code program has basically the same identification parameters as the deterministic experimental pollution source parameters. The ADE-GA method was applied to an actual site polluted by a gas station in Beijing, China. The parameters of the pollution source obtained from the detailed site investigation are basically consistent with the calculated values. Therefore, the source code established in this work is a reliable tool for identifying the parameters of groundwater pollution sources in small areas.

Chemical oxidation using stabilized hydrogen peroxide in high temperature, saline groundwater impacted with hydrocarbons and MTBE

In situ chemical oxidation (ISCO) of petroleum hydrocarbons (PHCs) within groundwater is considered a proven approach to addressing PHC-impacted groundwater in nonsaline environments. One of the most common oxidants used for oxidation of PHCs in groundwater is hydrogen peroxide (H2O2). Due to its highly reactive nature, H2O2 is often stabilized to aid in increasing its reactivity lifespan. Limited research and application of ISCO has been completed in warm, saline groundwater environments. Furthermore, even fewer studies have been completed in these environments for ISCO using stabilized H2O2. In this research, stabilized H2O2 was examined to determine its effectiveness in the treatment of PHCs and the additive methyl tert-butyl ether (MTBE). Three stabilizers (citrate, phytate, silica [SiO2]) were tested to determine if the stabilizers could enhance and extend the treatment life of H2O2 within saline groundwater. To determine the effect of salinity on the three stabilizers, groundwater and aquifer samples were collected from two saline locations that had different salinity (total dissolved solids of about 7,000 mg/L and 18,000 mg/L). Specific target chemicals for treatment were water soluble, mobile components of gasoline including benzene, toluene, ethylbenzene, xylenes, (BTEX) and MTBE. Previous studies using unactivated persulfate indicated that the PHCs within the groundwater could be oxidized, however, only limited oxidation of the MTBE could be affected. The results of the laboratory tests indicated that greater than 95 percent of the target hydrocarbons were removed within 7 days of treatment. Microcosms with citrate-stabilized H2O2 demonstrated a significantly faster and greater decline with most hydrocarbon concentrations reaching 400 mg/L to 90 percent) being measured in the citrate-stabilized microcosms. Unfortunately, H2O2 oxidation in the microcosms also resulted in production of up to 40 mg/L TBA or approximately 10 percent of the MTBE oxidized.

Using intrinsic bioremediation for petroleum–hydrocarbon contaminated groundwater cleanup and migration containment: Effectiveness and mechanism evaluation

Intrinsic bioremediation (IB) is the major mechanism causing the containment of petroleum hydrocarbons in groundwater. The effectiveness and mechanisms of IB on the contaminant removal were evaluated in this study. Groundwater was analyzed for the efficiency of IB, dominant bacteria, bacterial diversity, and biodegradation rates. Concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX) and methyl tert-butyl ether (MTBE) dropped from 6.5 and 0.14 mg/L in source area to 67 and 19 µg/L at the 145 m downgradient area. The biodegradation capacities for BTEX (50.9 mg/L) and MTBE (58.5 mg/L) were higher than the BTEX (6.5 mg/L) and MTBE (0.14 mg/L) concentrations within the plume. The bacterial diversities were assessed by 16S rRNA-based denatured gradient gel electrophoresis and nucleotide sequence analyses. More than 21 petroleum–hydrocarbon biodegrading bacterial species were detected in groundwater indicating that contaminants could be biodegraded by natural-occurring bacteria. The calculated MTBE and BTEX first-order decay rates were 5.7 × 10−4 and 1.3 × 10−3 per day, respectively. The high decay rates indicate that IB mechanisms played important roles in contaminant removal. The observed evidences of IB processes in highly contaminated areas included: (1) decreased electron acceptors, (2) production of degradation byproducts, (3) increased microbial populations and alkalinity, and (4) decreased electron donors and pH.

Application of controlled nutrient release to permeable reactive barriers

The application of controlled release nutrient (CRN) materials to permeable reactive barriers to promote biodegradation of petroleum hydrocarbons in groundwater was investigated. The longevity of release, influence of flow velocity and petroleum hydrocarbon concentration on nutrient release was assessed using soluble and ion exchange CRN materials; namely Polyon™ and Zeopro™. Both CRN materials, assessed at 4 °C and 23 °C, demonstrated continuing release of nitrogen, phosphorus and potassium (N–P–K) at 3500 bed volumes passing, with longer timeframes of N–P–K release at 4 °C. Zeopro™–activated carbon mixtures demonstrated depletion of N–P–K prior to 3500 bed volumes passing. Increased flow velocity was shown to lower nutrient concentrations in Polyon™ flow cells while nutrient release from Zeopro™ was largely unchanged. The presence of petroleum hydrocarbons, at 1.08 mmol/L and 3.25 mmol/L toluene, were not shown to alter nutrient release from Polyon™ and Zeopro™ across 14 days. These findings suggest that Polyon™ and Zeopro™ may be suitable CRN materials for application to PRBs in low nutrient environments.

Exploring petroleum hydrocarbons in groundwater by double solid phase extraction coupled to gas chromatography–flame ionization detector

This work proposes an analytical procedure for measuring aliphatic and aromatic hydrocarbons fractions present in groundwater. In this method, hydrocarbons are solid phase extracted (SPE) twice from the groundwater and the resulting fractions are analyzed by gas chromatography with flame ionization detection. The first SPE disposes the hydrocarbons present in groundwater in organic solvents and the second SPE divides them into aliphatic and aromatic hydrocarbons. The validation study is carried out and its uncertainties are discussed. Identifying the main sources of uncertainty is evaluated through applying the bottom-up approach. Limits of detection for hydrocarbons ranges are below 5µgL−1, precision is not above of 30%, and acceptable recoveries are reached for aliphatic and aromatic fractions studied. The uncertainty due to volume of the sample, factor of calibration and recovery are the highest contributions. The expanded uncertainty range from 13% to 26% for the aliphatic hydrocarbons ranges and from 14% to 23% for the aromatic hydrocarbons ranges. As application, the proposed method is satisfactorily applied to a set of groundwater samples collected in a polluted area where there is evidence to present a high degree of hydrocarbons. The results have shown the range of aliphatic hydrocarbons >C21–C35 is the most abundant, with values ranging from 215µgL−1 to 354µgL−1, which it is associated to a contamination due to diesel.

Biosurfactant-producing strains in enhancing solubilization and biodegradation of petroleum hydrocarbons in groundwater

Three biosurfactant-producing strains designated as BS-1, BS-3, and BS-4 were screened out from crude oil-contaminated soil using a combination of surface tension measurement and oil spreading method. Thin layer chromatography and infrared analysis indicated that the biosurfactants produced by the three strains were lipopeptide, glycolipid, and phospholipid. The enhancement of solubilization and biodegradation of petroleum hydrocarbons in groundwater employing biosurfactant-producing strains was investigated. The three strain mixtures led to more solubilization of petroleum hydrocarbons in groundwater, and the solubilization rate was 10.5 mg l−1. The combination of biosurfactant-producing strains and petroleum-degrading strains exhibited a higher biodegradation efficiency of 85.4 % than the petroleum-degrading strains (71.2 %). Biodegradation was enhanced the greatest with biosurfactant-producing strains and petroleum-degrading strains in a ratio of 1:1. Fluorescence microscopy images illustrate that the oil dispersed into smaller droplets and emulsified in the presence of biosurfactant-producing strains, which attached to the oil. Thus, the biodegradation of petroleum hydrocarbons in groundwater was enhanced.

Bacterial community evidence for anaerobic degradation of petroleum hydrocarbons in cold climate groundwater

Abstract There is currently limited scientific data to assess whether groundwater bacterial communities in fractured rock environments can degrade petroleum hydrocarbon plumes in cold regions. The former Colomac Mine is located in the Canadian Shield in the Northwest Territories (mean annual air temperature of − 5 °C) and is currently listed on the Federal Contaminated Sites inventory. Groundwater in fractured rock beneath the former fuel tank-farm at the mine site is contaminated by petroleum hydrocarbons. The objectives of this study were to investigate the bacterial community structure in the groundwater associated with hydrocarbon contamination, and to probe for potential anaerobic microbial processes involved in intrinsic bioremediation. Groundwater monitoring wells previously installed at the site were used to collect samples for chemical, isotopic and microbial analyses. Denaturing gradient gel electrophoresis (DGGE) analysis identified a relatively high bacterial diversity in the least contaminated locations, but as the hydrocarbon contamination increased, bacterial diversity decreased. Sequence analysis of the 16S rRNA gene demonstrated that the bacteria belonged to a wide range of genera, such as Pseudomonas, Thiobacillus, and Geobacter, all of which have been associated with the anaerobic degradation of hydrocarbons. Two putative nitrate-reducing genes were detected in samples with high nitrate reducing activity. Both chemical and microbiological results indicated the presence of microbial anaerobic processes by using nitrate, manganese(IV), ferric iron and sulfate as electron acceptors and suggest that these anaerobic processes play an important role in the biodegradation of dissolved petroleum hydrocarbons in the groundwater at the Colomac site. Our results also revealed that more than one biogeochemical process linked to hydrocarbon degradation could be present in a single borehole and these processes could vary spatially at this site.

High-pressure injection of dissolved oxygen for hydrocarbon remediation in a fractured dolostone aquifer

A field experiment was completed at a fractured dolomite aquifer in southwestern Ontario, Canada, to assess the delivery of supersaturated dissolved oxygen (supersaturated with respect to ambient conditions) for enhanced bioremediation of petroleum hydrocarbons in groundwater. The injection lasted for 1.5 h using iTi's gPro® oxygen injection technology at pressures of up to 450 kPa and at concentrations of up to 34 mg O 2/L. A three-dimensional numerical model for advective–dispersive transport of dissolved oxygen within a discretely-fractured porous medium was calibrated to the observed field conditions under a conservative (no-consumption) scenario. The simulation demonstrated that oxygen rapidly filled the local intersecting fractures as well as the porous matrix surrounding the injection well. Following injection, the local fractures were rapidly flushed by the natural groundwater flow system but slow back-diffusion ensured a relatively longer residence time in the matrix. A sensitivity analysis showed significant changes in behaviour with varying fracture apertures and hydraulic gradients. Applying the calibrated model to a 7-day continuous injection scenario showed oxygen residence times (at the 3 mg/L limit), within a radius of 2–4 m from the injection well, of up to 100 days. This study has demonstrated that supersaturated dissolved oxygen can be effectively delivered to this type of a fractured and porous bedrock system at concentrations and residence times potentially sufficient for enhanced aerobic biodegradation.

Potential for bioremediation of petroleum hydrocarbons in groundwater under cold climate conditions: A review

Globally, bioremediation is a common choice for remediation of petroleum hydrocarbon-contaminated sites. For application at cold climate sites, bioremediation approaches are appealing because they have potential to be more efficient and cost-effective than alternative, more energy intensive approaches. Several bioremediation approaches have been reported to be successful for petroleum hydrocarbon-contaminated soils at cold climate sites. In contrast, there are relatively few publications on applications of bioremediation for petroleum-contaminated groundwater at cold climate sites. Most of the existing relevant groundwater studies were conducted at sites with either no permafrost, or with sporadic to discontinuous permafrost. To date, the majority of cold climate groundwater investigations were at fuel spill sites; few studies on bioremediation of dissolved hydrocarbon plumes derived from crude oil or gas condensate have been published. Some studies reported that extents of hydrocarbon plumes in groundwater were limited by natural attenuation, including intrinsic bioremediation. At other sites, oxygenation of groundwater or amendments with nitrate were reported to be successful techniques for enhancing biodegradation of petroleum hydrocarbons. Both aerobic and anaerobic processes appear to be important at these sites. Based on three case studies, bioremediation (in situ or ex situ) may be feasible for sites with extensive permafrost. Further research and field demonstrations are required to establish or confirm the applicability of bioremediation technologies to clean up hydrocarbons in groundwater in various hydrogeological settings at cold climate sites.

Total Petroleum Hydrocarbons in Groundwater—Evaluation of Nondissolved and Nonhydrocarbon Fractions

Total petroleum hydrocarbons (TPH) in groundwater samples are commonly extracted and analyzed for comparison to regulatory standards and for forensic evaluation of the source of spilled petroleum. While this procedure is normally intended to provide information on hydrocarbons dissolved in water, several complicating factors exist. In this study, the significance of reported TPH values is evaluated for a suite of surface water, interstitial, and groundwater samples by comparing analytical data obtained on unfiltered water, filtered water, and water from which nonhydrocarbons were removed by treatment with silica gel. Results indicate that standard measurements of TPH in groundwater not only include dissolved petroleum hydrocarbons, but commonly also include contributions from: (1) hydrocarbons sorbed on particulate matter; (2) droplets or micellular forms of liquid hydrocarbon contamination; (3) biogenic hydrocarbons; (4) contamination by field or laboratory equipment; and (5) dissolved polar organics (nonhydrocarbons), which may be naturally occurring or derived from spilled petroleum products. These factors complicate the regulatory and forensic interpretation of standard TPH data for groundwater samples.

The Technical Case for Eliminating the Use of the TPH Analysis in Assessing and Regulating Dissolved Petroleum Hydrocarbons in Ground Water

AbstractIn many states, the total petroleum hydrocarbons (TPH) analysis based on gas chromatography‐flame ionization detection (GC‐FID) is still being used to assess and regulate ground water quality at petroleum release sites. The soluble fraction of fresh crude oil or fresh products that could potentially be dissolved into the ground water is limited to relatively few petroleum hydrocarbon constituents (primarily the C6 to C14 aromatics). Research by numerous investigators has shown that the reported TPH concentrations of ground water samples frequently do not represent dissolved petroleum hydrocarbons but rather represent nondissolved petroleum or polar nonhydrocarbon compounds. Nondissolved petroleum is frequently entrained within a sample when sampling ground water within affected soil, and polar nonhydrocarbons are present in ground water as a result of petroleum biodegradation or other factors. These constituents are being measured because the TPH analysis does not include steps to remove nondissolved petroleum or a silica gel cleanup to remove polars.Many states have regulatory action levels for TPH in ground water that are in the 0.1 to 2 mg/L range. The technical basis for these action levels appears to be toxicity and/or organoleptic (taste and odor) properties of the dissolved petroleum hydrocarbons associated with fresh oil or fresh products. The presence of compounds measured as TPH that are not dissolved petroleum hydrocarbons has proven problematic for regulatory decision‐making because the comparison of concentration data to the regulatory criteria may not be correct. Because the TPH analysis does not reliably distinguish between dissolved petroleum hydrocarbons and other compounds, it should not be used to assess or regulate dissolved petroleum hydrocarbons, in ground water. We recommend that constituent‐specific analyses be used to assess and regulate ground water quality at petroleum hydrocarbon release sites. If TPH must be used due to regulatory requirements, samples should be cleaned up with silica gel to remove polars (and turbidity should be removed, if present) prior to analysis so that comparison to regulatory action levels that are based on properties of dissolved petroleum hydrocarbon constituents is technically appropriate.

Design, Construction and Operation of a Funnel and Gate In-Situ Permeable Reactive Barrier for Remediation of Petroleum Hydrocarbons in Groundwater

A white spirit spill at a factory site located in a residentialarea of south eastern Australia led to contamination of shallowgroundwater that fed into a nearby river. The contaminatedgroundwater contained toluene, ethyl benzene, and xylene and n-alkanes in the C6–C36 fraction range. A funnel andgate permeable reactive barrier was designed and built, based onpreliminary pilot scale tests using peat as the medium for thegate and the work conducted is presented as a case study. Thetechnical effectiveness of the funnel and gate, over the 10 monthoperating period in which data was collected, indicates that peatrepresents an effective material for use in the gate component offunnel and gate remedial systems. The application of the funneland gate technology represented a substantial saving to the client and was effective in preventing ongoing pollution of thenearby river. The construction of the funnel and gate system also incurred the minimum disturbance to the public access areasbetween the facility and the river.

Toluene induced cometabolism of cis-1,2-dichloroethylene and vinyl chloride under conditions expected downgradient of a permeable Fe(0) barrier

A new approach for groundwater treatment combines a permeable Fe(0) barrier to break down higher chlorinated solvents like PCE and TCE with a downgradient aerobic biological treatment system to biotransform less chlorinated solvents, such as DCE and vinyl chloride (VC), and petroleum hydrocarbons. The expected bacterial performance downgradient of an Fe(0) barrier was evaluated through laboratory batch experiments with a toluene-degrading mixed culture that cometabolically transforms cis-1,2-DCE and VC. The amount of cis-1,2-DCE (initially at 500 ppb) and VC (initially at 250 ppb) transformed was controlled by the initial toluene (0–12,000 ppb) and biomass (0–15 μg protein ml −1) concentrations. Cis-1,2-DCE was removed much more effectively than VC, and a higher toluene concentration in comparison to the co-substrate concentrations was needed for complete co-substrate removal. Competitive inhibition was indicated by the sequential degradation of toluene and the co-substrates. When the pH was above 8, the effectiveness of cis-1,2-DCE and VC transformation decreased rapidly for a given toluene concentration. 1,1-DCE, a product of the reduction processes within the Fe(0) barrier, hindered the transformation of toluene, cis-1,2-DCE and VC at concentrations as low as 10 ppb. Acetylene, another chemical reaction product, only marginally inhibited the transformation of the co-substrates in the studied concentration range of 0–1700 ppb. Overall, the coupling of an Fe(0) barrier and subsequent biodegradation appears feasible for remediation of complex mixtures of chlorinated solvents and petroleum hydrocarbons in groundwater. Our results suggest that supplemental toluene or other primary substrate upgradient of the biological process may be required, and that pulsing of this substrate may be advisable. Because passing through a permeable Fe(0) barrier increases the groundwater pH, neutralization with acid may be needed before entering the bioactive zone if the natural buffer capacity of the soil is insufficient. Breakthrough of 1,1-DCE from the Fe(0) barrier could prove a critical factor for the bacterial performance.

A one-dimensional reactive multi-component transport model for biodegradation of petroleum hydrocarbons in groundwater

A one-dimensional (1-D) multi-component model accounting for hydrological transport inorganic equilibrium chemistry and microbial activity during kinetically controlled biodegradation in groundwater of compounds such as benzene, toluene, ethylbenzene and xylenes (BTEX) is presented. The problem is solved numerically using an operator-splitting method to couple advective–dispersive transport of organic and inorganic solutes with a geochemical equilibrium package PHREEQC and a biodegradation module. The transport equations for inorganic solutes are solved for total aqueous component concentrations. Changes in such concentrations due to precipitation/dissolution of minerals and chemical speciation are accounted for within PHREEQC. For chemical elements occurring in multiple valence states, separate components are defined and transported. The biodegradation module simulates the sequential or parallel activity of multiple bacterial groups attached to soils and their biochemical effects. The model has been evaluated by comparison with an existing model simulation of a 1-D inorganic redox problem. An application of the model is shown for a synthetic case where BTEX compounds are degraded by sequential reduction of aqueous electron acceptors.

Case Study: Natural Attenuation of Dissolved Hydrocarbons at a Former Gas Plant

Abstract In recent years, interest has grown in biological processes that limit the migration of dissolved petroleum hydrocarbons in groundwater. While the process of biodegradation of dissolved petroleum hydrocarbons in groundwater is generally acknowledged, only a few carefully documented examples exist. Work to date at a former natural gas processing plant provides documentation of natural biodegradation of dissolved hydrocarbon in groundwater as well as insights into the microbiological processes that are most significant at this site.

Bacterial Biodegradation of Petroleum Hydrocarbons in Groundwater: In situ Augmented Bioreclamation with Enrichment Isolates in California

Bacterial Biodegradation of Petroleum Hydrocarbons in Groundwater: In situ Augmented Bioreclamation with Enrichment Isolates in California