Manufactured Gas Plant Research Articles

A Statistical Evaluation of Sediment Quality Triad Benthic Community Measurements in PAH-Impacted Sediments at a Manufactured Gas Plant Site along the Hudson River

The sediment quality triad (SQT) assumes that three measurements (sediment chemistry, laboratory bioassay, and benthic macroinvertebrate counts) comprise an independent assessment of impact, which when integrated using a weight-of-evidence approach provides a comprehensive assessment of risk. An SQT assessment was conducted on 41 sediment samples collected adjacent to a manufactured gas plant site on the freshwater reach of the Hudson River in New York State. The assessment shows that the benthic macroinvertebrate data did not correlate with either sediment or pore water polycyclic aromatic hydrocarbon (PAH) concentrations, nor did these data show consistent relationships to the results of laboratory bioassay testing (Hyalella azteca 28-day survival or biomass). The benthic community across the site and reference areas was comprised of few taxa, all of which were pollution-tolerant organisms with tolerance values greater than or equal to five. Only in significantly impacted sediment samples with PAH concentrations in the thousands of milligrams per kilogram, pore water concentrations above 100 toxic units, and visible non-aqueous phase liquid present in the sample did the benthic macroinvertebrate data show a response. In contrast, sediment and pore water PAH measurements and H. azteca toxicity testing provided consistent interpretation of impact. These results illustrate that benthic macroinvertebrate data may contain less information value and be a more challenging line of evidence to interpret in triad studies conducted in certain ecological settings; in this case, a large-order river with a relatively depauperate benthic community dominated by species tolerant of PAHs.

Aerobic Bioremediation of PAH Contaminated Soil Results in Increased Genotoxicity and Developmental Toxicity.

The formation of more polar and toxic polycyclic aromatic hydrocarbon (PAH) transformation products is one of the concerns associated with the bioremediation of PAH-contaminated soils. Soil contaminated with coal tar (prebioremediation) from a former manufactured gas plant (MGP) site was treated in a laboratory scale bioreactor (postbioremediation) and extracted using pressurized liquid extraction. The soil extracts were fractionated, based on polarity, and analyzed for 88 PAHs (unsubstituted, oxygenated, nitrated, and heterocyclic PAHs). The PAH concentrations in the soil tested, postbioremediation, were lower than their regulatory maximum allowable concentrations (MACs), with the exception of the higher molecular weight PAHs (BaA, BkF, BbF, BaP, and IcdP), most of which did not undergo significant biodegradation. The soil extract fractions were tested for genotoxicity using the DT40 chicken lymphocyte bioassay and developmental toxicity using the embryonic zebrafish (Danio rerio) bioassay. A statistically significant increase in genotoxicity was measured in the unfractionated soil extract, as well as in four polar soil extract fractions, postbioremediation (p < 0.05). In addition, a statistically significant increase in developmental toxicity was measured in one polar soil extract fraction, postbioremediation (p < 0.05). A series of morphological abnormalities, including peculiar caudal fin malformations and hyperpigmentation in the tail, were measured in several soil extract fractions in embryonic zebrafish, both pre- and postbioremediation. The increased toxicity measured postbioremediation is not likely due to the 88 PAHs measured in this study (including quinones), because most were not present in the toxic polar fractions and/or because their concentrations did not increase postbioremediation. However, the increased toxicity measured postbioremediation is likely due to hydroxylated and carboxylated transformation products of the 3- and 4-ring PAHs (PHE, 1MPHE, 2MPHE, PRY, BaA, and FLA) that were most degraded.

Combining in situ chemical oxidation, stabilization, and anaerobic bioremediation in a single application to reduce contaminant mass and leachability in soil

Laboratory batch reactors were maintained for 32 weeks to test the potential for an in situ remedy that combines chemical oxidation, stabilization, and anaerobic bioremediation in a single application to treat soil from a manufactured gas plant, contaminated with polycyclic aromatic hydrocarbons (PAH) and benzene, toluene, ethylbenzene, and xylenes (BTEX). Portland cement and slaked lime were used to activate the persulfate and to stabilize/encapsulate the contaminants that were not chemically oxidized. Native sulfate-reducing bacteria degraded residual contaminants using the sulfate left after persulfate activation. The ability of the combined remedy to reduce contaminant mass and leachability was compared with NaOH-activated persulfate, stabilization, and sulfate-reducing bioremediation as stand-alone technologies. The stabilization amendments increased pH and temperature sufficiently to activate the persulfate within 1 week. Activation with both stabilization amendments and NaOH removed between 55% and 70% of PAH and BTEX. However, combined persulfate and stabilization significantly reduced the leachability of residual BTEX and PAH compared with NaOH activation. Sulfide, 2-naphthoic acid, and the abundance of subunit A of the dissimilatory sulfite reductase gene (dsrA) were used to monitor native sulfate-reducing bacteria, which were negatively impacted by activated persulfate, but recovered completely within weeks.

Identification of anthraquinone-degrading bacteria in soil contaminated with polycyclic aromatic hydrocarbons.

Quinones and other oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) are toxic and/or genotoxic compounds observed to be cocontaminants at PAH-contaminated sites, but their formation and fate in contaminated environmental systems have not been well studied. Anthracene-9,10-dione (anthraquinone) has been found in most PAH-contaminated soils and sediments that have been analyzed for oxy-PAHs. However, little is known about the biodegradation of oxy-PAHs, and no bacterial isolates have been described that are capable of growing on or degrading anthraquinone. PAH-degrading Mycobacterium spp. are the only organisms that have been investigated to date for metabolism of a PAH quinone, 4,5-pyrenequinone. We utilized DNA-based stable-isotope probing (SIP) with [U-(13)C]anthraquinone to identify bacteria associated with anthraquinone degradation in PAH-contaminated soil from a former manufactured-gas plant site both before and after treatment in a laboratory-scale bioreactor. SIP with [U-(13)C]anthracene was also performed to assess whether bacteria capable of growing on anthracene are the same as those identified to grow on anthraquinone. Organisms closely related to Sphingomonas were the most predominant among the organisms associated with anthraquinone degradation in bioreactor-treated soil, while organisms in the genus Phenylobacterium comprised the majority of anthraquinone degraders in the untreated soil. Bacteria associated with anthracene degradation differed from those responsible for anthraquinone degradation. These results suggest that Sphingomonas and Phenylobacterium species are associated with anthraquinone degradation and that anthracene-degrading organisms may not possess mechanisms to grow on anthraquinone.

Retardation of iron-cyanide complexes in the soil of a former manufactured gas plant site

The soil in the vicinities of former Manufactured Gas Plant (MGP) sites is commonly contaminated with iron-cyanide complexes (ferric ferrocyanide). The phenomenon of cyanide mobility in soil, according to the literature, is mainly governed by the dissolution and precipitation of ferric ferrocyanide, which is only slightly soluble (<1 mg L−1) under acidic conditions. In this paper, retention properties of the sandy loam soil and the potential vertical movement of the solid iron-cyanide complexes, co-existing with the dissolution, sorption and precipitation reactions were investigated. Preliminary research conducted on a former MGP site implied colloidal transport of ferric ferricyanide from the initial deposition in the wastes layer towards the sandy loam material (secondary accumulation), which possibly retarded the mobility of cyanide (CN). A series of batch and column experiments were applied in order to investigate the retardation of iron-cyanide complexes by the sandy loam soil. Batch experiments revealed that in circumneutral pH conditions sandy loam material decreases the potassium ferro- and ferricyanide concentration. In column experiments a minor reduction in CN concentration was observed prior to addition of iron sulfide (FeS) layer, which induced the formation of the Prussian blue colloids in circumneutral pH conditions. Precipitated solid iron-cyanide complexes were mechanically filtered by the coherent structure of the investigated soil. Additionally, the reduction of the CN concentration of the percolation solutions by the sandy loam soil was presumably induced due to the formation of potassium manganese iron-cyanide (K2Mn[Fe(CN)6]).

Modeling of gas generation from the river adjacent to the manufactured gas plant

Ebullition of gas bubbles through sediment can enhance the migration of gases through the subsurface and potentially affect the emission of important greenhouse gases to the atmosphere.

Historical cancer incidence and mortality assessment in an Illinois community proximal to a former manufactured gas plant

ObjectivesConcern has been raised that the occurrence of cancer may be increased in neighbourhoods around a former manufactured gas plant in Champaign, Illinois, USA. Thus, we compared historical rates of...

Gowanus Canal Superfund Site. I: NAPL Mobility Testing of MGP-Impacted Sediments

The Gowanus Canal superfund site is located in Brooklyn, New York. The site is impacted by nonaqueous phase liquid (NAPL) from historic manufactured gas plant (MGP) sites and other sources. One of the primary objectives for the selected remedy included eliminating the migration of NAPL into the canal. Accordingly, the amount of NAPL present in sediment samples was quantified and physical testing was conducted to determine a threshold amount of NAPL that could be potentially mobilized into the canal as a result of upwelling groundwater. Undisturbed core samples of native sediment were collected and analyzed for NAPL, water, and air pore fluid saturation (PFS) using the Dean-Stark extraction method, and the total petroleum hydrocarbon (TPH) content. Sediment samples were found to contain NAPL saturations ranging from nondetectable (<0.12%) to 52%. A relatively good correlation (R2=0.77) was observed between the Dean-Stark and TPH results when compared on an equivalent mass basis. The NAPL mobility was evaluated for induced groundwater fluxes ranging from average existing site conditions to a factor of 10 higher (13–130 cm/day). Consistent NAPL mobility was observed when the NAPL saturation exceeded 21%. However, when the NAPL saturation results were converted to TPH on a mass basis (milligrams of NAPL per kilogram of sediment), the results were a poor indicator of NAPL mobility.

Gowanus Canal Superfund Site. II: Stabilization/Solidification of MGP-Impacted Sediments

AbstractThe Gowanus Canal Superfund site is located in Brooklyn, New York. The sediment of the 2.9-km (1.8-mi) long canal is impacted at multiple locations by nonaqueous phase liquids (NAPLs) mainly from three historic manufactured gas plant (MGP) sites with measured NAPL saturations up to 50%. A stabilization/solidification (SS) treatability study was completed using 15 mix designs in a tiered testing suite that included unconfined compressive strength, hydraulic conductivity, and contaminant leach testing by equilibrium (as per U.S. EPA standard methods) and semidynamic leach methods, where semidynamic leach testing was modified with polydimethylsiloxane liners. Mix designs containing 5–10% (by dry weight) of a cement blend paired with 0.5% bentonite, or 1–4% organoclay added to wet NAPL-impacted sediments were characterized by unconfined compressive strength values greater and hydraulic condictivity values lower than 345 kPa (50 psi) and 1×10−6 cm/s, respectively. Leaching reductions for naphthalene (...

A comparison of physicochemical methods for the remediation of porous medium systems contaminated with tar

The remediation of former manufactured gas plant (FMGP) sites contaminated with tar DNAPLs (dense non-aqueous phase liquids) presents a significant challenge. The tars are viscous mixtures of thousands of individual compounds, including known and suspected carcinogens. This work investigates the use of combinations of mobilization, solubilization, and chemical oxidation approaches to remove and degrade tars and tar components in porous medium systems. Column experiments were conducted using several flushing solutions, including an alkaline–polymer (AP) solution containing NaOH and xanthan gum (XG), a surfactant–polymer (SP) solution containing Triton X-100 surfactant (TX100) and XG, an alkaline–surfactant–polymer (ASP) solution containing NaOH, TX100, and XG, and base-activated sodium persulfate both with and without added TX100. The effectiveness of the flushing solutions was assessed based on both removal of polycyclic aromatic hydrocarbon (PAH) mass and on the reduction of dissolved-phase PAH concentrations. SP flushes of 6.6 to 20.9PV removed over 99% of residual PAH mass and reduced dissolved-phase concentrations by up to two orders of magnitude. ASP flushing efficiently removed 95–96% of residual PAH mass within about 2PV, and significantly reduced dissolved-phase concentrations of several low molar mass compounds, including naphthalene, acenaphthene, fluorene, and phenanthrene. AP flushing removed a large portion of the residual tar (77%), but was considerably less effective than SP and ASP in terms of the effect on dissolved PAH concentrations. Persulfate was shown to oxidize tar components, primarily those with low molar mass, however, the overall degradation was relatively low (30–50% in columns with low initial tar saturations), and the impact on dissolved-phase concentrations was minimal.

Volatile Organic Compounds from Coal Tar and Soil Vapor Samples at MGP Sites

This study characterized organic compounds found in New York State manufactured gas plant (MGP) coal tar vapors using controlled laboratory experiments from four separate MGP sites. In addition, a limited number of deep (0.3–1.2 m above coal tar) and shallow (1.2–2.4 m above coal tar) soil vapor samples were collected above the in situ coal tar source at three of these sites. A total of 29 compounds were consistently detected in the laboratory-generated coal tar vapors at 50°C, whereas 24 compounds were detected at 10°C. The compounds detected in the field sample results were inconsistent with the compounds found in the laboratory-generated samples. Concentrations of compounds in the shallow soil vapor sample were either non-detectable or substantially lower than those found in deeper samples, suggesting attenuation in the vadose zone. Laboratory-generated data at 50°C compared the (% non-aromatic)/(% aromatic) ratio and indicated that this ratio may provide good discrimination between coal tar vapor and common petroleum distillates.

Activated Carbon Preconditioning to Reduce Contaminant Leaching in Cement-Based Stabilization of Soils

AbstractAdding powdered activated carbon (PAC) with cement can enhance stabilization and solidification (S/S) by adsorbing organic contaminants. Simultaneous addition of PAC and cement reduces soil-handling costs, but cement-hydration reactions coat PAC with Ca(OH)2 before contaminants can be adsorbed onto PAC. Laboratory studies were done on four aged, contaminated soils from manufactured gas plant sites to compare S/S performance with simultaneous addition of PAC and cement versus cement addition after preconditioning with PAC. Ordinary (Type I) portland cement, quicklime, and class C fly ash were the cementing agents tested. Leaching of benzene, toluene, ethylbenzene, and xylenes and naphthalene was quantified using the synthetic precipitation leaching procedure, and unconfined compressive strength was measured. Allowing a 20-week PAC preconditioning time dramatically enhanced leaching and strength compared with adding cement and PAC simultaneously. Adding cement at the same time as PAC resulted in onl...

Bioavailability of (Geno)toxic Contaminants in Polycyclic Aromatic Hydrocarbon-Contaminated Soil Before and After Biological Treatment.

Contaminated soil from a former manufactured-gas plant site was treated in a laboratory-scale bioreactor. Desorbability and biodegradability of 14 polycyclic aromatic hydrocarbons (PAHs) and 4 oxygenated PAHs (oxy-PAHs) were investigated throughout a treatment cycle. Desorbability was determined using a mixed-function sorbent (Oasis® HLB) or a hydrophobic sorbent (Tenax®) in dialysis tubing suspended in the soil slurry. Toxicity and genotoxicity of the whole soil and the desorbable fractions were determined by DNA damage response analysis with the chicken DT40 B-lymphocyte isogenic cell line and its DNA repair-deficient mutant Rad54-/-. Biological treatment significantly removed both PAHs and oxy-PAHs, and their desorbability decreased throughout the bioreactor treatment cycle. Collectively, oxy-PAHs were more desorbable and biodegradable than the corresponding PAHs; for example, the oxy-PAH present at the highest concentration, 9,10-anthraquinone, was more desorbable and biodegradable than anthracene. For both PAHs and oxy-PAHs, the percentage removed in the bioreactor significantly exceeded the percentage desorbed from untreated soil, indicating that desorption did not control the extent of biodegradation. Consistent with previous results on the same soil, genotoxicity of the whole soil slightly increased after biological treatment. However, both toxicity and genotoxicity of the desorbable constituents in the soil decreased after treatment, suggesting that any genotoxic constituents that may have formed during treatment were primarily associated with less accessible domains in the soil.

Enhanced Desorption of PAHs from Manufactured Gas Plant Soils Using Different Types of Surfactants

Surfactant enhanced remediation is thought to be an effective method for the remediation of soils polluted with hydrophobic organic compounds. Desorption of polycyclic aromatic hydrocarbons (PAHs) from an abandoned manufactured gas plant (MGP) soil was evaluated using four eluting agents including Triton X-100 (TX100), sodium dodecylbenzene sulfonate (SDBS), rhamnolipid water solution (RWS) and rhamnolipid fermentation broth (RFB). The weight solubilization ratios for acenaphthene and fluorene were in the order of TX100 > SDBS > RWS > RFB. The Sm value, which indicates the maximum amounts of surfactants adsorbed in the soil, was in the order of RWS > RFB > SDBS > TX100. By using 8 g L−1 of TX100, SDBS and RWS and 100% of RFB, the T-PAHs removal for the MGP soil contaminated with 207.86 mg T-PAHs kg−1 dry soil was 48.0%, 45.7%, 1.9%, and 8.6%, respectively, while that decreased to 41.6%, 37%, 0.38%, and 1.3% for the soil contaminated with 3 494.78 mg T-PAHs kg−1 dry soil. Only 8 g L−1 TX100 could remove all types of the 16 PAHs partly in the MGP soil, and the removal efficiencies of different PAHs ranged from 13% to 77.8%. The results of this study herein provide valuable information for the selection of TX100 surfactant for remediating PAH-contaminated soils in MGP.

Stability of Prussian Blue in Soils of a Former Manufactured Gas Plant Site

Soil contamination with iron-cyanide complexes is a common problem at former manufactured gas plant (MGP) sites. Dissolution of the cyanide, from Prussian Blue (ferric ferrocyanide), creates an environmental hazard, whereas the risk of groundwater contamination depends on the stability of dissolved iron–cyanide complexes. Lack of a standard leaching method to determine the water-soluble (plant-available) cyanide fraction generates potential limitations for implementing remediation strategies like phytoremediation. Applicability of neutral solution extraction to determine the water-soluble cyanide fraction and the stability of Prussian Blue in surface and near-surface soils of an MGP site in Cottbus, undersaturated and unsaturated water conditions, was studied in column leaching and batch extraction experiments. MGP soils used in the long-term tests varied according to the pH (5.0–7.7) and the total cyanide content (40–1718 mg kg−1). Column leaching, after four months of percolation, still yielded effluent concentrations exceeding the German drinking water limit (> 50 μg L−1) and the solubility of Prussian Blue reported in the literature (< 1 mg L−1) from both alkaline and acidic soils. Long-term (1344 h) extraction of MGP soils with distilled water was sufficient to dissolve 97% of the total cyanide from the slightly alkaline soils and up to 78% from the acidic soils. Both experiments revealed that dissolution of ferric ferrocyanide under circum-neutral pH and oxic water conditions is a function of time, where the released amount is dependent on the soil pH and total cyanide content. Unexpectedly high and continuous solubility of Prussian Blue, both in acidic and slightly alkaline MGP soils, implies the need to introduce an additional cyanide fraction (“readily soluble fraction”) to improve and specify cyanide leaching methods. Long-term extraction of cyanide-contaminated soil in neutral solution seems to be a promising approach to evaluate the potential hazard of groundwater pollution at the MGP sites.

Remediation of Former Manufactured Gas Plants and Other Coal-tar SitesRemediation of Former Manufactured Gas Plants and Other Coal-tar Sites, by HathewayAllen W., CRC Press, 2011, £130, hardback, 1354 pp., ISBN 9780824791063

Winner of the 2013 Claire P. Holdredge Awardee for Remediation of Former Manufactured Gas Plants and Other Coal-Tar Sites.This award, first established in 1962 by the Association of Environmental and Engineering Geologists, is named in honor of Claire P. Holdredge, a founding member and the first President of the Association. The award is

Managing Public Health Risks Using Air Monitoring at a Former Manufactured Gas Plant Site

Monitoring emissions from a former Manufactured Gas Plant (MGP) site during remediation was used to manage risks associated with inhalation of Volatile Organic Compounds (VOCs) and contaminated particulates acting as an exposure conduit for Polycyclic Aromatic Hydrocarbons (PAHs) and heavy metals. This risk management case study presents a USEPA-approved air monitoring program implemented to manage public health risks during remediation at a former MGP site located in the southeast United States. Risk-based Acceptable Air Concentrations (AACs) were developed and a sampling regimen established to monitor potential emissions to maintain contaminant concentrations below the AACs. The exposure duration used was based on a twelve-month project duration and an exposure time of 24 hours per day; equations, toxicity values and sources were based on USEPA’s Regional Screening Levels. A total 535 twenty-four hour time weighted samples (269 VOC samples and 266 PAH samples) were collected over the project duration. Only minor levels of VOCs and PAHs were detected and no results were above the AACs. These timeweighted averages demonstrate that the real-time air monitoring and control measures implemented at the site effectively maintained concentrations below the AACs and were protective of public health.

Solvent–water extraction method for the evaluation of polycyclic aromatic hydrocarbons bioavailability in coal–tar-contaminated soils

A solvent–water extraction method was proposed as an assessment tool to estimate the bioavailability of polycyclic aromatic hydrocarbons in coal–tar-contaminated soils. The approach taken was to measure the percent of polycyclic aromatic hydrocarbons extracted by a solvent–water mixture and comparing the results with the percent of polycyclic aromatic hydrocarbons degraded in a soil slurry reactor. Five soil samples from three former manufactured gas plant sites and a coal–tar disposal site which were operated between 1880 and 1947, and 1945 and 1950, respectively, in Iowa, USA were used in this study. Extraction experiments were conducted using acetone–water or ethanol–water mixtures with solvent volume fractions ranging from 1.0 to 0.4 (v/v). The percent of polycyclic aromatic hydrocarbons extracted from the various soils decreased as the volume fraction of the solvent in the solvent–water mixture was reduced. An acetone–water mixture of 0.6 was found to be appropriate in correlating the percent of polycyclic aromatic hydrocarbons degraded to the percent of polycyclic aromatic hydrocarbons extracted. For the first correlation, the percent extracted and the percent biodegraded were modified by using the molecular weights and log K ow of polycyclic aromatic hydrocarbons, respectively. For the second correlation, the equation relating the percent extracted and the percent biodegraded was modified using soil properties such as organic carbon content and percent of clay and silt. Although the experiments were conducted for a limited number of soils, the extraction method appeared to be a good starting point in estimating the bioavailability of polycyclic aromatic hydrocarbons in coal–tar-contaminated soils.

Biostimulation Reveals Functional Redundancy of Anthracene-Degrading Bacteria in Polycyclic Aromatic Hydrocarbon-Contaminated Soil

Stable-isotope probing was previously used to identify bacterial anthracene-degraders in untreated soil from a former manufactured gas plant site. However, subsequent pyrosequence analyses of total bacterial communities and quantification of 16S rRNA genes indicated that relative abundances of the predominant anthracene-degrading bacteria (designated Anthracene Group 1) diminished as a result of biological treatment conditions in lab-scale, aerobic bioreactors. This study identified Alphaproteobacterial anthracene-degrading bacteria in bioreactor-treated soil which were dissimilar to those previously identified. The largest group of sequences was from the Alterythrobacter genus while other groups of sequences were associated with bacteria within the order Rhizobiales and the genus Bradyrhizobium. Conditions in the bioreactor enriched for organisms capable of degrading anthracene which were not the same as those identified as dominant degraders in the untreated soil. Further, these data suggest that identification of polycyclic aromatic hydrocarbon-degrading bacteria in contaminated but untreated soil may be a poor indicator of the most active degraders during biological treatment.

Desorption kinetics of PAHs from aged industrial soils for availability assessment

Persistent organic pollutants (POPs), such as polycyclic aromatic hydrocarbons (PAHs), may be found in high concentrations in soils of former industrial sites including manufactured gas plants or coking plants. Techniques using moderate solvent extraction, biological tests or solid phase extraction have proved useful for pollution availability estimation. However, more accurate and reliable measurement tools specifically adapted to low concentrations are still needed. Based on a solid–liquid extraction using a Tenax® resin, we suggest a protocol to assess the bioavailability of PAHs, dedicated to aged industrial wasteland soils. Desorption kinetics were measured on three representative contaminated industrial soils. Results were modeled using a first order two-compartment model that provided an estimate of the rapidly desorbing fraction, which was considered to be available, over a 30h extraction period. In conclusion, this method, allowing the measurement of the available fraction, might prove more relevant than the total concentration value when assessing soil contamination related risks. It may also predict achievable bioremediation performances.