Stable Isotope Probing to Confirm Field‐Scale Co‐Metabolic Biodegradation of 1,4‐Dioxane

1,4‐Dioxane, a common co‐contaminant with chlorinated solvents, is present in groundwater at Site 24 at Vandenberg Air Force Base in California. Historical use of chlorinated solvents resulted in concentrations of 1,4‐dioxane in groundwater up to approximately 2,000 μg/L. Starting in 2013, an in situ propane biosparge system operation demonstrated reductions in 1,4‐dioxane concentrations in groundwater. The work detailed herein extends the efforts of the first field demonstration to a second phase and confirms the biodegradation mechanism via use of stable isotope probing (SIP). After two months of operation, 1,4‐dioxane concentrations decreased approximately 45 to 83 percent at monitoring locations in the test area. The results of the SIP confirmed ¹³C‐enriched 1,4‐dioxane was transformed into dissolved inorganic carbon (suggesting mineralization to carbon dioxide) and incorporated into microbial biomass (likely attributed to metabolic uptake of biotransformation intermediates or of carbon dioxide).  ©2016 Wiley Periodicals, Inc.     

Characterizing In Situ Methane‐Enhanced Biostimulation Potential for 1,4‐Dioxane Biodegradation in Groundwater

This study characterizes the 1,4‐dioxane biodegradation potential for an in situ methane‐enhanced biostimulation field pilot study conducted at Air Force Plant 44, located south of the Tucson International Airport in Arizona. In this study, the use of methane as the primary substrate in aerobic cometabolic biodegradation of 1,4‐dioxane is evaluated using environmental molecular diagnostic tools. The findings are compared to an adjacent pilot study, wherein methane was generated via enhanced reductive dechlorination and where methane monooxygenase and methane‐oxidizing bacteria were also found to be abundant. This article also presents the use of ¹³C and ²H isotopic ratio enrichment, a more recent tool, to support the understanding of 1,4‐dioxane biodegradation in situ. This study is the first of its kind, although alkane gas‐enhanced biodegradation of 1,4‐dioxane has been evaluated extensively in microcosm studies and propane‐enhanced biodegradation of 1,4‐dioxane has been previously studied in the field. ©2016 Wiley Periodicals, Inc.     

In Situ Remediation of 1,4‐Dioxane Using Electrical Resistance Heating

Recent regulatory changes need more challenging treatment goals for 1,4‐dioxane. However, significant treatment limitations exist in part due to the high solubility and low Henry's law constant of 1,4‐dioxane. Two case studies are reported with substantial 1,4‐dioxane concentration reductions through in situ thermal remediation via electrical resistance heating (ERH). Concentration reductions greater than 99.8 percent of 1,4‐dioxane have been observed in the field using ERH. Concentrations of 1,4‐dioxane in air and steam extracted by an ERH vapor recovery system have also been evaluated. Laboratory studies were conducted to further understand the mechanisms that enable ERH remediation of 1,4‐dioxane. Vapor liquid equilibrium studies in water and soil were conducted and utilized to develop an ERH treatment cost model for 1,4‐dioxane. Existing field data were correlated to the 1,4‐dioxane treatment cost model. Field observations and laboratory testing indicate steam stripping that occurs through ERH remediation is an effective treatment method for 1,4‐dioxane. ©2015 Wiley Periodicals, Inc.     

Intrinsic and Stimulated In Situ Biodegradation of Hexachlorocyclohexane (HCH)

The feasibility of the biodegradation of HCH and its intermediates has been investigated. A recent characterisation of two sites in The Netherlands has shown intrinsic biodegradation of HCH. At one site, breakdown products (monochlorobenzene, benzene and chlorophenol) were found in the core of the HCH-plume, whereas the HCH-concentration decreased over time and space. Characterisation of a second, industrial site indicated less intrinsic biodegradation and the need to stimulate biodegradation. In the laboratory, enhanced HCH degradation was tested with soil and groundwater material from both sites, and the required conversion to the intermediates benzene and monochlorobenzene was demonstrated. Furthermore, the biodegradation of these intermediates could be initiated by adding low amounts of oxygen (<5%). Adding nitrate enhanced this degradation. We hypothesise that this occurs through anaerobic nitrate reducing conversion of oxidised intermediates.At the non-industrial other site, intrinsic degradation took place, as shown in the laboratory experiments. Interpretation of the field data with computer codes Modflow and RT3D was performed. As a result of the modelling study, it has been proposed to monitor natural attenuation for several years before designing the final approach.At the industrial site, the results of the batch experiments are applied. Anaerobic HCH degradation to monochlorobenzene and benzene is stimulated via the addition of an electron donor.Infiltration facilities have been installed at the site to create an anaerobic infiltration zone in which HCH will be degraded, and these facilities are combined with the redevelopment of the site.     

Spreadsheet‐Based Design Tool for In Situ Anaerobic Bioremediation Using Soluble Substrate

A Microsoft Excel spreadsheet‐based design tool has been developed to assist remediation professionals in the design of injection systems for distributing soluble substrate (SS) to enhance in situ anaerobic bioremediation. The user provides site data, design parameters, and unit‐cost information to generate estimates of remediation‐system cost and steady‐state contact efficiency (CE_SS) for various designs. CE_SS is estimated from a nonlinear regression equation that includes terms for the SS injection concentration (C_I), minimum substrate concentration (C_MIN), groundwater travel time between rows of injection wells (T_T), SS half‐life (T_H), substrate reinjection time interval (T_R), and pore volumes of substrate solution injected (PV). With this tool, users can quickly compare the relative costs and performance of different injection alternatives and identify the best design for their specific site conditions. The design process embodied in the tool includes: (1) entering injection‐well configuration and unit costs for well installation, injection, and substrate; (2) determining treatment‐zone dimension; (3) selecting trial injection‐well spacing, time period between substrate reinjection, and injection pore volume; and (4) estimating contact efficiency and capital and life‐cycle costs. This process is then repeated until a final design is selected. In most cases, injection costs increase with increasing CE_SS. However, the best (highest) ratio of CE_SS to injection cost typically occurs for CE_SS in the range of 70 to 80 percent. © 2013 Wiley Periodicals, Inc.     

In Situ treatment of PFAS‐impacted groundwater using colloidal activated Carbon

Poly‐ and perfluoroalkyl substances (PFASs) have been identified by many regulatory agencies as contaminants of concern within the environment. In recent years, regulatory authorities have established a number of health‐based regulatory and evaluation criteria with groundwater PFAS concentrations typically being less than 50 nanograms per liter (ng/L). Subsurface studies suggest that PFAS compounds are recalcitrant and widespread in the environment. Traditionally, impacted groundwater is extracted and treated on the surface using media such as activated carbon and exchange resins. These treatment technologies are generally expensive, inefficient, and can take decades to reach treatment objectives. The application of in situ remedial technologies is common for a wide variety of contaminants of concern such as petroleum hydrocarbons and volatile organic compounds; however, for PFASs, the technology is currently emerging. This study involved the application of colloidal activated carbon at a site in Canada where the PFASs perfluorooctanoate (PFOA) and perfluorooctane sulfonic acid (PFOS) were detected in groundwater at concentrations up to 3,260 ng/L and 1,450 ng/L, respectively. The shallow silty‐sand aquifer was anaerobic with an average linear groundwater velocity of approximately 2.6 meters per day. The colloidal activated carbon was applied using direct‐push technology and PFOA and PFOS concentrations below 30 ng/L were subsequently measured in groundwater samples over an 18‐month period. With the exception of perfluoroundecanoic acid, which was detected at 20 ng/L and perfluorooctanesulfonate which was detected at 40 ng/L after 18 months, all PFASs were below their respective method detection limits in all postinjection samples. Colloidal activated carbon was successfully distributed within the target zone of the impacted aquifer with the activated carbon being measured in cores up to 5 meters from the injection point. This case study suggests that colloidal activated carbon can be successfully applied to address low to moderate concentrations of PFASs within similar shallow anaerobic aquifers.     

In‐Situ and Ex‐Situ Bioremediation Options for Treating Perchlorate in Groundwater

Perchlorate has been identified as a water contaminant in 14 states, including California, Nevada, New Mexico, Arizona, Utah, and Texas, and current estimates suggest that the compound may affect the drinking water of as many as 15 million people. Biological treatment represents the most‐favorable technology for the effective and economical removal of perchlorate from water. Biological fluidized bed reactors (FBRs) have been tested successfully at the pilot scale for perchlorate treatment at several sites, and two full‐scale FBR systems are currently treating perchlorate‐contaminated groundwater in California and Texas. A third full‐scale treatment system is scheduled for start‐up in early 2002. The in‐situ treatment of perchlorate through addition of specific electron donors to groundwater also appears to hold promise as a bioremediation technology. Recent studies suggest that perchlorate‐reducing bacteria are widely occurring in nature, including in groundwater aquifers, and that these organisms can be stimulated to degrade perchlorate to below the current analytical reporting limit (< 4 μg/l) in many instances. In this article, in‐situ and ex‐situ options for biological treatment of perchlorate‐contaminated groundwater are discussed and results from laboratory and field experiments are presented. © 2002 Wiley Periodicals, Inc.     

Spatial Distribution of Geobacteraceae and Sulfate‐Reducing Bacteria During In Situ Bioremediation of Uranium‐Contaminated Groundwater

Analysis of the physiological status of subsurface microbial communities generally relies on the study of unattached microorganisms in the groundwater. These approaches have been employed in studies on bioremediation of uranium‐contaminated groundwater at a study site in Rifle, Colorado, in which Geobacter species typically account for over 90 percent of the microbial community in the groundwater during active uranium reduction. However, to develop efficient in situ bioremediation strategies it is necessary to know the status of sediment‐associated microorganisms as well. In order to evaluate the distribution of the natural community of Geobacter during bioremediation of uranium, subsurface sediments were packed into either passive flux meters (PFMs) or sediment columns deployed in groundwater monitoring wells prior to acetate injection during in situ biostimulation field trials. The trials were performed at the Department of Energy's (DOE's) Rifle Integrated Field Research Challenge site. Sediment samples were removed either during the peak of Fe(III) reduction or the peak of sulfate reduction over the course of two separate field experiments and preserved for microscopy. Direct cell counts using fluorescence in situ hybridization (FISH) probes targeting Geobacter species indicated that the majority of Geobacter cells were unattached during Fe(III) reduction, which typically tracks with elevated rates of uranium reduction. Similar measurements conducted during the sulfate‐reducing phase revealed the majority of Geobacter to be attached following exhaustion of more readily bioavailable forms of iron minerals. Laboratory sediment column studies confirmed observations made with sediment samples collected during field trials and indicated that during Fe(III) reduction, Geobacter species are primarily unattached (90 percent), whereas the majority of sulfate‐reducing bacteria and Geobacter species are attached to sediment surfaces when sulfate reduction is the predominant form of metabolism (75 percent and 77 percent, respectively). In addition, artificial sediment experiments showed that pure cultures of Geobacter uraniireducens, isolated from the Rifle site, were primarily unattached once Fe(III) became scarce. These results demonstrate that, although Geobacter species must directly contact Fe(III) oxides in order to reduce them, cells do not firmly attach to the sediments, which is likely an adaptive response to sparsely and heterogeneously dispersed Fe(III) minerals in the subsurface. © 2013 Wiley Periodicals, Inc.     

Combined thermal and zero‐valent iron In Situ soil mixing remediation technology

Thermal remediation of contaminated soils and groundwater by injection of hot air and steam using large‐diameter auger in situ soil mixing effectively remediates volatile and semivolatile organic compounds. This technology removes large amounts of contamination during the early treatment stages, but extended treatment times are needed to achieve high removal percentages. Combining thermal treatment with another technology that can be injected and mixed into the soil, and that continues to operate after removal of the drilling equipment, improves removal efficiency, and reduces cost. Using field‐determined pseudo first‐order removal rates, the cost of the combined remediation of chlorinated volatile organic compounds (CVOCs) by thermal treatment followed by reductive dechlorination by iron powder has been estimated as 57 percent of the cost of thermal treatment alone. This analysis was applied to a case‐study remediation of 48,455 cubic yards, which confirmed the cost estimate of the combined approach and showed over 99.8 percent removal of trichloroethene and other chlorinated VOCs. © 2010 Wiley Periodicals, Inc.     

固定化Acinetobacter sp. XA05和Sphingomonas sp. FG03降解苯酚

从活性污泥和受苯酚污染的土壤中分离出的菌株XA05和FG03均具有很强的苯酚生物降解能力。16srDNA序列分析表明,XA05和FG03菌株分别属于不动杆菌属(Acinetobacter sp.)和鞘氨醇单胞菌属(Sphin-gomonas sp.)。实验结果表明,在苯酚初始质量浓度为800.0mg/L、培养时间为35h的条件下,自由悬浮细胞和固定化细胞的苯酚降解率均高于95.0%。     

Lead in soil by field‐portable x‐ray fluorescence spectrometry—an examination of paired In Situ and laboratory ICP‐AES results

A major aspect of lead hazard control is the evaluation of soil lead hazards around housing coated with lead‐based paint. The use of field‐portable X‐ray fluorescence (FPXRF) to do detailed surveying, with limited laboratory confirmation, can provide lead measurements in soil (especially for planning abatement activities) in a far more cost‐efficient and timely manner than laboratory analysis. To date, one obstacle to the acceptance of FPXRF as an approved method of measuring lead in soil has been a lack of correspondence between field and laboratory results. In order to minimize the differences between field and laboratory results, RTI International (RTI) has developed a new protocol for field drying and sieving soil samples for field measurement by FPXRF. To evaluate this new protocol, composite samples were collected in the field following both U.S. Department of Housing and Urban Development (HUD) guidelines and ASTM International (ASTM) protocols, measured after drying by FPXRF, and returned to the laboratory for confirmatory inductively coupled plasma atomic emission spectroscopy (ICP‐AES) analysis. Evaluation of study data from several diverse sites revealed no statistical difference between paired FPXRF and ICP‐AES measurements using the new method. © 2008 Wiley Periodicals, Inc.     

In‐Situ Plasma Remediation of Contaminated Soils

Plasma‐torch technology has excellent potential for cost‐effective treatment of contaminated soils and other types of buried waste material. This article describes the evolution and basic features of this technology, with emphasis on the non‐transferred plasma arc torch. In addition, selected results from both laboratory experiments and field demonstrations will show how this technology can successfully destroy hazardous/toxic materials and/or stabilize contaminants in situ so they are no longer a threat to human health and the environment. © 2001 John Wiley & Sons, Inc.     

选择性吸附-高效生物降解法处理含硝基苯与苯酚混合废水

结合NDA-150型树脂（简称树脂）选择性吸附和生物降解的优点,对含硝基苯和苯酚的模拟混合废水（简称混合废水）进行处理。通过树脂的选择性吸附,使混合废水中的硝基苯和苯酚分离,随后用高效菌对树脂所吸附的硝基苯进行生物降解,同时实现树脂的再生。实验结果表明：通过调节混合废水的pH,树脂可有效地将混合废水中的硝基苯和苯酚进行选择性吸附分离;树脂对硝基苯的吸附是可逆的;树脂的再生程度受微生物对可利用硝基苯质量浓度的下限（1．2mg／L）限制;吸附-生物再生循环实验结果表明,该树脂可有效抵抗微生物的生物降解与破坏。     

Exploring the Biodegradation Potential of Polyethylene Through a Simple Chemical Test Method

Oxidatively degradable polyethylene is finding widespread use, particularly in applications such as single use packaging and agriculture. However, the key question which still remains unanswered is the ultimate fate and biodegradability of these polymers. During a short-time frame only the oxidized low molecular weight fraction will be amenable to significant biodegradation. The short-time frame biodegradation potential of different LDPE-transition metal formulations was, thus, explored through a simple chemical extraction of oxidized fraction. In addition the effectiveness of different transitions metals was evaluated by comparing the extractable fractions. Blown LDPE films modified with different transition metal based pro-oxidants were thermo-oxidized at 60 °C over extended periods. The structural changes occurring in the polymer were monitored and the oxidized degradation products formed as a result of the aging process were estimated by extractions with water and acetone. The extractable fraction first increased to approximately 22 % as a result of thermo-oxidative aging and then leveled off. The extractable fraction was approximately two times higher after acetone extraction compared to extraction with water and as expected, it was higher for the samples containing pro-oxidants. Based on our results in combination with existing literature we propose that acetone extractable fraction gives an estimation of the maximum short-term biodegradation potential of the material, while water extractable fraction indicates the part that is easily accessible to microorganisms and rapidly assimilated. The final level of biodegradation under real environmental conditions will of course be highly dependent on the specific environment, material history and degradation time.     

An In Situ Bioreactor for the Treatment of Petroleum Hydrocarbons in Groundwater

Two pilot tests of an aerobic in situ bioreactor (ISBR) have been conducted at field sites contaminated with petroleum hydrocarbons. The two sites differed with respect to hydrocarbon concentrations. At one site, concentrations were low but persistent, and at the other site concentrations were high enough to be inhibitory to biodegradation. The ISBR unit is designed to enhance biodegradation of hydrocarbons by stimulating indigenous microorganisms. This approach builds on existing Bio‐Sep^® bead technology, which provides a matrix that can be rapidly colonized by the active members of the microbial community and serves to concentrate indigenous degraders. Oxygen and nutrients are delivered to the bioreactor to maintain conditions favorable for growth and reproduction, and contaminated groundwater is treated as it is circulated through the bed of Bio‐Sep^® beads. Groundwater moving through the system also transports degraders released from Bio‐Sep^® beads away from the bioreactor, potentially increasing biodegradation rates throughout the aquifer. Groundwater sampling, Bio‐Traps, and molecular biological tools were used to assess ISBR performance during the two pilot tests. Groundwater monitoring indicated that contaminant concentrations decreased at both sites, and the microbial data suggested that these decreases were due to degradation by indigenous microorganisms rather than dilution or dispersion mechanisms. Taken together, these lines of evidence showed that the ISBR system effectively increased the number and activity of indigenous microbial degraders and enhanced bioremediation at the test sites. © 2013 Wiley Periodicals, Inc.     

Polymer Mineralization in Soils: Effects of Cold Storage on Microbial Populations and Biodegradation Potential

Soil retrieval, processing and storage procedures can have a profound effect on soil microorganisms. In particular, changes in soil microbial populations may adversely affect the biological activity of a soil and drastically alter the soil's potential to mineralize added substrates. The effects of cold storage on the biodegradation of a series of test polymers was investigated using two soils—a synthetic soil mix (SM-L8) and a field soil (Bridgehampton silt loam) from Rhode Island (RI-1). Biodegradation tests were conducted using freshly prepared/collected soil and again following storage at 4°C for 3 to 8 months. Prior to each biodegradation test, the soils were incubated at 60% water-holding capacity (WHC) and 25°C to rejuvenate the microbial populations; the soils were incubated for periods of 48 h (freshly collected soil) or 25 days (soils stored at 4°C). Soil microbial populations were assessed by enumerating different segments of the population on agar plates containing different selective media. Mineralization of the test polymers (cellulose, poly-3-hydroxybutyrate, and starch acetate, d.s. 1.5) was monitored using standard respirometric techniques. Our results demonstrated that cold storage had a generally negative effect on the soil microbial populations themselves but that its effect on the capacity of the soil microorganisms to degrade the test polymers varied between soils and polymer type. Whereas cold storage resulted in dramatic shifts in the community structure of the soil microbial populations, substantial restoration of these populations was possible by first conditioning the soils at 60% WHC and ambient temperatures for 25 days. Likewise, although the effects of cold storage on polymer mineralization varied with the test polymer and soil, these effects could be largely offset by including an initial 25-day stabilization period in the test.     

A Multiple Lines of Evidence Framework to Evaluate Intrinsic Biodegradation of 1,4‐Dioxane

Development of a multiple lines of evidence (MLOE) framework to evaluate the intrinsic biodegradation potential of 1,4‐dioxane is vital to implementing management strategies at groundwater sites impacted by 1,4‐dioxane. A comprehensive MLOE approach was formed to provide significant evidence of natural degradation of 1,4‐dioxane comingled with tetrahydrofuran (THF) within a large, diffuse plume. State‐of‐the art molecular biological analyses and compound‐specific isotope analysis (CSIA) were employed to support more traditional approaches for data analysis (concentration trend analyses, spatial distribution, temporal changes, geochemical biodegradation attenuation indicators, plume mass estimates, and fate and transport modeling). The molecular analyses demonstrated that microorganisms capable of both metabolic and cometabolic degradation of 1,4‐dioxane were present throughout the groundwater plume, whereas the CSIA data provided supporting evidence of biodegradation. 1,4‐Dioxane biomarkers were present and abundant throughout the 1,4‐dioxane plume, and our biomarkers tracked the plume with reasonable accuracy. Evidence also suggests that THF‐driven cometabolic biodegradation as well as catabolic 1,4‐dioxane biodegradation were active at this site. These data supplemented the traditional lines of evidence approaches, which demonstrated that 1,4‐dioxane attenuation was occurring across the groundwater plume and that nondestructive physical processes alone did not account for the observed 1,4‐dioxane attenuation. This MLOE framework combining new and traditional analyses demonstrates that this site has a significant capacity for intrinsic biodegradation of 1,4‐dioxane. ©2016 Wiley Periodicals, Inc.     

Remediation of PCB‐Contaminated Soil Using Extraction and Destruction: Bench‐Scale Test

Polychlorinated biphenyls (PCBs) are a persistent environmental issue worldwide. This study summarizes the results obtained from a bench‐scale test of remediating PCB‐impacted soil. The research aimed to evaluate the effectiveness of extracting the PCB Aroclor 1260 from soil, transferring it to a liquid matrix, and then treating the PCB‐containing liquid using an Activated Metal Treatment System, a technology developed by NASA based on zero valent magnesium (ZVMg). The soil was from a former electrical plant area impacted by PCBs. The initial concentration of untreated soil contained an average of 4.7 ± 0.15 mg/kg of Aroclor 1260. The results showed that the mass transfer phenomena is possible using ethanol as a liquid matrix, reaching transfer results up to 93 percent. The ZVMg enabled the destruction of the Aroclor 1260, which reached 20 percent without any buildup of undesirable by‐products, such as less chlorinated PCBs.  ©2016 Wiley Periodicals, Inc.