Effective low-temperature thermal aeration of soils

Low-temperature thermal aeration (LTTA) is a remedial technology developed by Canonie Environmental Services Corp. (Canonie) for use on soils containing nonchlorinated hydrocarbons, chlorinated solvents, volatile organic compounds (VOCs), chlorinated pesticides, and low levels of polynuclear aromatic hydrocarbons (PAHs). The LTTA system separates these hazardous constituents from excavated soils and allows the treated soils to be redeposited on-site without restriction. This article describes the various components and operation of LTTA systems for the remediation of soils contaminated with chlorinated and nonchlorinated constituents. The article also details the results of projects completed to date, principally for soil impacted with chlorinated hydrocarbons, and discusses the general characteristics and results of systems used for soils contaminated with nonchlorinated hydrocarbons (gasoline, etc.).     

Remediation of DDT‐contaminated soil using optimized mixtures of surfactants and a mixing system

Soil contaminated with persistent pesticides, such as DDT, poses a serious risk to humans and to wildlife. A surfactant‐aided soil‐washing technique was studied as an alternative method for remediation of DDT‐contaminated soil. An ex situ soil washing method was investigated using nonionic and anionic surfactants due to the clayey structure of the contaminated soil. A mixture of 1 percent nonionic surfactant (Brij 35) and 1 percent anionic surfactant (SDBS) removed more than 50 percent of DDT from soil in a flow‐through system, whereas individual surfactants or other combinations of the surfactants had a lower removal efficiency. The soil‐washing technique was improved using a mixing system. The mixture of surfactants was optimized in the mixing system, and the combination of 2 percent Brij 35 and 0.1 percent SDBS was found to be optimum, removing 70 to 80 percent of DDT. Prewashing of the soil with tap water decreased the adsorption of surfactants to soil particles by 30 to 40 percent, and postwashing recovered 90 percent of the surfactants. © 2010 Wiley Periodicals, Inc.     

Impact of iron concentration and ph on zero‐valent iron dechlorination of DDT for brownfields

Soil contamination with persistent pesticides such as dichloro‐diphenyl‐trichloroethane (DDT) is a major issue at many brownfield sites. A technology that can be used to treat DDT‐contaminated soil using surfactants is to enhance the migration of the contaminants from the soil phase to the liquid phase, followed by the dechlorinating of the mobilized DDT in the liquid phase using zero‐valent iron (ZVI). The DDT degradation using ZVI occurs under anaerobic conditions via reductive reactions. The effect of the iron concentration on the dechlorination rate is assessed in the range of 1 to 40 percent (weight to volume) for remediation of a DDT‐contaminated site in Ontario, Canada. The optimum percentage of iron is found to be 20 percent at which the dechlorination rates of DDT and 1,1‐dichloro‐2,2‐bis(p‐chlorophenyl)ethane (DDD) were 4.5 and 0.6 mg/L/day, respectively. While mixing of the reaction solution is shown to be important in providing the iron surface available for the dechlorination reaction throughout the reaction solution, there is no significant difference between batch and fed‐batch mode of adding iron to the dechlorination process. Low pH values (pH = 3) increased the dechlorination rates of DDT and DDD to 6.03 and 0.75 mg/L/day, respectively at a 20 percent iron concentration, indicating increased dechlorination rates in acidic conditions. © 2010 Wiley Periodicals, Inc.     

土壤氰化物污染生物修复技术研究进展

综述了植物修复、微生物修复和生物联合修复等土壤氰化物污染生物修复技术的降解机理、降解途径及降解影响因素的研究进展,探讨了氰化物生物修复技术的发展趋势和应用前景。指出基于提高修复时效和针对土壤复合污染类型的多技术融合研究、基于提高微生物耐受性和降解效率的菌株固定化及菌根真菌-植物联合技术研究以及基于工程化应用为导向的现场试验研究是未来研究的重点领域,为土壤氰化物污染的综合治理和修复提出了新思路。     

The Use of Zero‐Valent Iron (ZVI) Technology to Promote DDT and Dieldrin Degradation at Point Pelee National Park

Point Pelee National Park (PPNP) is highly contaminated with dichlorodiphenyltrichloroethane (DDT) and dieldrin due to the historical use of these two persistent organochlorine pesticides. Zero‐valent iron (ZVI) technology with and without amendments has been successfully used in the past to promote organochlorine pesticides degradation in several locations in North America and Europe. In this study, the use of two commercially available ZVI products, DARAMEND^® and EHC^®, to promote DDT and dieldrin degradation in PPNP's soil and groundwater were investigated. DARAMEND^® was applied to PPNP's soil in a laboratory experiment and in an in situ pilot‐scale plot. In both cases, DARAMEND^® did not significantly increase DDT or dieldrin degradation in treated soils. The effectiveness of EHC^® was tested in a laboratory experiment that simulated the park's groundwater environment using PPNP's pesticide contaminated soil. The result was consistent with the one reported for DARAMEND^®, in that there was no significant increase in DDT or dieldrin degradation in any of the samples treated with EHC^®. These results demonstrate that both of these ZVI commercially available products are not suitable for in situ remediation at PPNP.  ©2017 Wiley Periodicals, Inc.     

Electrical resistance heating of volatile organic compounds in Sedimentary rock

Electrical resistance heating (ERH) has become a common method of remediation for volatile organic compounds (VOCs) in unconsolidated soils, both above and below the water table. Recently, use of ERH has expanded to include treatment of contaminated sedimentary bedrock. This article describes the implementation issues for rock remediation and provides case studies of three sites remediated by ERH in Maryland, New Jersey, and Indiana. With proper design, remediation of bedrock can be as effectively completed as remediation of overburden materials. © 2010 Wiley Periodicals, Inc.     

Low intervention soil remediation approaches

Traditional bioremediation approaches have been used to treat petroleum source contamination in readily accessible soils and sludges. Contamination under existing structures is a greater challenge. Options to deal with this problem have usually been in the extreme (i.e., to dismantle the facility and excavate to an acceptable regulated residual, or to pump and treat for an inordinately long period of time). The excavated material must be further remediated and cleanfill must be added to close the excavation. If site assessments were too conservative or incomplete, new contamination adulterating fill soils may result in additional excavation at some later date. Innovative, cost-efficient technologies must be developed to remove preexisting wastes under structures and to reduce future remediation episodes. An innovative soil bioremediation treatment method was developed and evaluated in petroleum hydrocarbon contaminated (PHC) soils at compressor stations of a natural gas pipeline running through Louisiana. The in-situ protocol was developed for remediating significant acreage subjected to contamination by petroleum-based lubricants and other PHC products resulting from a chronic leakage of lubricating oil used to maintain the pipeline itself. Initial total petroleum hydrocarbon (TPH) measurements revealed values of up to 12,000 mg/kg soil dry weight. The aim of the remediation project was to reduce TPH concentration in the contaminated soils to a level of <200 mg/kg soil dry weight, a level negotiated to be acceptable to state and federal regulators. After monitoring the system for 122 days, all sites showed greater than 99-percent reduction in TPH concentration.     

Electrical Resistance Heating of Volatile Organic Compounds in Sedimentary Rock

Electrical resistance heating (ERH) is a common method of remediation for volatile organic compounds in unconsolidated soils, both above and below the water table. In the past eight years, ERH has been used to successfully treat 10 or more contaminated sedimentary bedrock sites. Sedimentary bedrock treatment has recently expanded to greater depths and into karst limestone environments. This article describes the implementation issues for rock remediation and provides case studies of three sites remediated by ERH in Pennsylvania and Alabama. With proper design, the remediation of sedimentary bedrock can be completed as effectively as the remediation of overburden materials. © 2014 Wiley Periodicals, Inc.     

石油污染土壤的微生物修复技术

介绍了石油污染土壤微生物修复技术的影响因素;概述了生物刺激、生物强化、固定化微生物、植物-微生物联合修复以及电动-微生物联合修复石油污染土壤的技术原理,分析了现阶段土壤修复过程中面临的难题,预测了微生物修复技术的研究方向。指出优化微生物的环境条件、培育新型高效的基因工程菌和开发经济高效的新型修复技术等将是未来微生物修复技术的发展趋势。     

Use of a novel biomarker,botryococcane, to monitor biodegradation of two lacustrine‐sourced crude oils

Bioremediation is a proven alternative for remediating petroleum‐impacted soils at exploration and production (E&P) sites. Monitoring remediation performance can involve detection and quantification of biodegradation resistant compounds such as C₃₀17α(H),21β(H)‐hopane, which requires the use of gas chromatography with mass spectrometry detection (GC/MS). Due to the remoteness of many E&P sites, this technology is not always available, and alternative methods are needed to provide reliable quantitative measurements of petroleum remediation efficiency. This study provides a detailed chemical characterization of lacustrine‐sourced crude oils and a technical basis for measuring the effectiveness of bioremediation efforts for soil impacted by those crudes. We show that the novel isoprenoid hydrocarbon botryococcane is relatively stable in lacustrine‐sourced crude oils compared with C₃₀17α(H),21β(H)‐hopane under moderate biodegradation conditions generally observed in field samples. We have also demonstrated that, due to the stability and relatively elevated concentration of botryococcane in lacustrine oils, it can be reliably measured using the more cost‐effective and available GC/FID methodology, and thereby be used to monitor the progress of ongoing soil bioremediation activities at remote sites.     

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.     

Coupling Flow Analysis With Geochemical and Microbiological Analyses to Assess the Bioremediation Feasibility of a Contaminated Aquifer

An integrated approach combining classic and molecular microbiological methods, “in vitro” bioremediation assays and groundwater numerical modeling, has been established to identify optimized solutions for remediating aquifers contaminated with organic pollutants. Bacteria have been isolated from an aquifer contaminated with toluene and methyl tert‐butyl ether (MTBE), selected for their growth with contaminants as a sole carbon source and identified through 16S rDNA partial sequencing. Successive biodegradation laboratory tests have been performed to determine which chemical conditions were more appropriate for the isolated bacteria to more efficiently oxidize toluene and MTBE. A groundwater model was created using FEFLOW code first to determine the movement of the plume front and second to simulate the impact of the biodegradation processes along the groundwater flow directions based on the bioremediation rates obtained in the laboratory. The results show that this innovative and interdisciplinary model can be used to assist in developing monitoring and remediation plans for cleaning up complex contaminated groundwater sites. This approach successfully combines the identification of the optimum biogeochemical conditions for bacterial biodegradation to occur with the predictability of the development of the process over time, ensuring decisive support in the management of contaminated sites. ©2016 Wiley Periodicals, Inc.     

SITE Demonstration of Enhanced In-Situ Bioremediation of Chlorinated and Nonchlorinated Organic Compounds in Fractured Bedrock

A field demonstration of an enhanced in-situ bioremediation technology was conducted between March 1998 and August 1999 at the ITT Industries Night Vision (ITTNV) Division plant in Roanoke, Virginia. The bioremediation process was evaluated for its effectiveness in treating both chlorinated and nonchlorinated volatile organic compounds (VOCs) in groundwater located in fractured bedrock. Chlorinated compounds, such as trichloroethene (TCE), in fractured bedrock pose a challenging remediation problem. Not only are chlorinated compounds resistant to normal biological degradation, but the fractured bedrock presents difficulties to traditional techniques used for recovery of contaminants and for delivery of amendments or reagents for in-situ remediation. The demonstration was conducted under the U.S. Environmental Protection Agency's Superfund Innovative Technology Evaluation (SITE) program. The SITE program was established to promote the development, demonstration, and use of innovative treatment technologies for the cleanup of Superfund and other hazardous waste sites. This article presents selected results of the demonstration and focuses on understanding the data in light of the fractured bedrock formation. © 2002 Wiley Periodicals, Inc.     

Sustainable soil remediation by refrigerated condensation at sites with “high‐concentration” recalcitrant compounds and NAPL: Two case studies

Remediation of recalcitrant compounds at sites with high concentrations of volatile organic compounds (VOCs) or nonaqueous‐phase liquids (NAPLs) can present significant technical and financial (long‐term) risk for stakeholders. Until recently, however, sustainability has not been included as a significant factor to be considered in the feasibility and risk evaluation for remediation technologies. The authors present a framework for which sustainability can be incorporated into the remediation selection criteria focusing specifically on off‐gas treatment selection for soil vapor extraction (SVE) remediation technology. SVE is generally considered an old and standard approach to in situ remediation of soils at a contaminated site. The focus on off‐gas treatment technology selection in this article allows for more in‐depth analysis of the feasibility evaluation process and how sustainable practices might influence the process. SVE is more commonly employed for recovery of VOCs from soils than other technologies and generally employs granular activated carbon (GAC), catalytic, or thermal oxidation, or an emerging alternative technology known as cryogenic‐compression and condensation combined with regenerative adsorption (C3–Technology). Of particular challenge to the off‐gas treatment selection process is the potential variety of chemical constituents and concentrations changing over time. Guidance is available regarding selection of off‐gas treatment technology (Air Force Center for Environmental Excellence, 1996; U.S. Environmental Protection Agency, 2006). However, there are common shortcomings of off‐gas treatment technology guidance and applications; practitioners have rarely considered sustainability and environmental impact of off‐gas treatment technology selection. This evaluation includes consideration of environmental sustainability in the selection of off‐gas treatment technologies and a region‐specific (Los Angeles, California) cost per pound and time of remediation comparisons between GAC, thermal oxidation, and C3–Technology. © 2008 Wiley Periodicals, Inc.     

Investigation of naphtalene sulfonate compounds sorption in a soil artificially contaminated using batch and column assays

In the present work desorption tests of an artificially contaminated soil by naphatelene sulphonated compounds have been carried out by soil washing realised by water at different pH: Naphtalene-1,5-disulfonic acid (1-5 NDS), 2-naphthol-6,8 disulphonic acid (G-acid) and sodium beta-naphtalene-sulphonate (beta-salt) have been selected as more representative organic compounds present in the ex industrial site of ACNA (Cengio, SV, Italy) in which very serious contamination levels of several pollutants are present both in the soils and surface waters. Equilibrium batch tests have been carried out in order to find the best operative condition in column washing tests. The obtained results can be considered very preliminary but useful to arrange a next experimental work that will be realised on real contaminated soils.     

Recent applications of phytoremediation technologies

Although the application of microbe biotechnology has been successful with petroleum-based constituents, microbial digestion has met with limited success for widespread residual organic and metal pollutants located above the potentiometric surface. Vegetation-based remediation, on the other hand, shows potential for accumulating, immobilizing, and transforming low levels of persistent contamination from the subsurface. Agricultural bioremediation, called geobotany or phytoremediation, relies on the remediating abilities of contaminant-accumulating plants to remove contamination from soil or groundwater. In natural ecosystems, plants act to filter and metabolize substances generated by nature. Phytoremediation affirmatively applies this process to help clean up contamination created by artificial means. Plants have proven effective at remediating areas contaminated with organic chemical wastes such as petroleum products, solvents, wood preservatives, pesticides, and metals. Phytoremediation is not the best technology for every site but has shown success with lead, cadmium, zinc, and radionuclides. The phytoremediation process takes much longer than conventional methods to clean a site and is dependent upon the type and degree of contamination. Concentrations must be within a narrow range of tolerable levels and the presence of the contamination must be at the appropriate depth. Nevertheless, phytoremediation offers an effective alternative to conventional, engineered remedial plans that usually involve costly activities like excavation, treatment, and disposal of soil or pump-and-treat technologies for groundwater. Phytoremediation also seems to be a promising new technology for the treatment of stormwater, industrial wastewater, and sewage. The relative low costs of capital for start-up together with negligible operations and maintenance costs provide a strong incentive for further investigation and development of phytoremediation projects.     

A risk assessment of chlorinated aliphatics in bioremediated soils

Natural microbes living in contaminated subsurface media can be enhanced to degrade large concentrations of contaminating compounds at a faster rate than the microbes could degrade under natural conditions. A feasibility study demonstrating this principle was performed on-site in southern Louisiana to evaluate the effectiveness of two microbial degradation remediation methods used to decrease the human carcinogenic risks associated with exposure to ethylene dichloride and vinyl chloride concentrations in contaminated clay and sludge soils at the site. The results of the study are compared to an acceptable Louisiana Department of Environmental Quality closure level to evaluate in-situ microbial enhancement in chlorinated aliphatic-contaminated sludge and clay soils as a remediation/cleanup alternative in similar industrial situations.