Pneumatic fracturing to remove VOCS

A new process for enhancing in-situ remediation of low-permeability soil and rock formations is presently under development at the Hazardous Substance Management Research Center (HSMRC). The patented process, known as ?pneumatic fracturing,”? consists of injecting high-pressure air or other gas into contaminated geologic formations at controlled flow rates and pressures. In fine-grained soils such as clay, pneumatic fracturing creates conductive channels in the formation, thereby increasing the permeability and exposed surface area of the contaminated soil. The potential benefits of pneumatic fracturing are significant, since in-situ remedial technologies are essentially limited by the pore gas exchange rate of the soil being treated. This article describes the results of a recent demonstration of pneumatic fracturing at an industrial site to enhance a volatile organic compound (VOC) extraction system. After establishing the baseline removal rate of soil gas effluent from the clay, soil surrounding the extraction system was fractured to enhance VOC with drawal. A substantial improvement in the VOC removal rate was observed, including: (1) flush effluent concentrations that increased up to 200 times; and (2) air flows in the formation that increased up to 1,000 times.     

Using pneumatic fracturing extraction to achieve regulatory compliance and enhance voc removal from low-permeability formations

The New Jersey Department of Environmental Protection and Energy (NJDEPE) has been developing cleanup regulations that focus on remediation, rather than extended delineation, and on integrating regulatory requirements with technological developments. To this end, the NJDEPE, under the regulatory aegis of the Environmental Cleanup and Responsibility Act (ECRA), is monitoring an innovative treatment technology pilot test at a TCE-contaminated ECRA site in Hillsborough, New Jersey. The purpose of the study is to determine the applicability of pneumatic fracturing extraction (PFE) as a source-removal technique for extracting volatile organic compounds (VOCs) trapped informations with low permeability. The technology being pilot tested is pneumatic fracturing extraction, a process for enhancing permeability to promote in-situ removal and treatment of VOCs. The patented process uses high-pressure air injected into an isolated subsurface zone at controlled rates and pressures. At a critical point, the geologic material ruptures, and fractures are created that radiate outward from the fracture location. At the pilot test site, formation air flow was increased from 400 percent to 700 percent. PFE is a key component of the overall remediation strategy at the Hillsborough site. Consistent with proposed NJDEPE regulations, a ground-water pump-and-treat system will be installed for plume migration control. Once the pump-and-treat system has been established and shown to be effective, a more aggressive source removal program will be implemented using PFE. This program will include construction of a vadose zone PFE system and evaluation of the use of pneumatic fracturing to remove saturated zone residual dense nonaqueous phase liquids (DNAPL). Preliminary calculations suggest that if source zone concentrations can be reduced to 10 ppm of TCE, then TCE groundwater concentrations may be reduced to background levels at the property boundary compliance points.     

Environmental sustainability comparison of a hypothetical pneumatic waste collection system and a door-to-door system

Waste collection is one of the life cycle phases that influence the environmental sustainability of waste management. Pneumatic waste collection systems represent a new way of arranging waste collection in densely populated urban areas. However, limited information is available on the environmental impacts of this system. In this study, we compare the environmental sustainability of conventional door-to-door waste collection with its hypothetical pneumatic alternative. Furthermore, we analyse whether the size of the hypothetical pneumatic system, or the number of waste fractions included, have an impact on the results. Environmental loads are calculated for a hypothetical pneumatic waste collection system modelled on an existing dense urban area in Helsinki, Finland, and the results are compared to those of the prevailing, container-based, door-to-door waste collection system. The evaluation method used is the life-cycle inventory (LCI). In this study, we report the atmospheric emissions of greenhouse gases (GHG), SO(2) and NO(x). The results indicate that replacing the prevailing system with stationary pneumatic waste collection in an existing urban infrastructure would increase total air emissions. Locally, in the waste collection area, emissions would nonetheless diminish, as collection traffic decreases. While the electricity consumption of the hypothetical pneumatic system and the origin of electricity have a significant bearing on the results, emissions due to manufacturing the system's components prove decisive.     

Pneumatic vs. door-to-door waste collection systems in existing urban areas: a comparison of economic performance

Pneumatic waste collection systems are becoming increasingly popular in new urban residential areas, and an attractive alternative to conventional vehicle-operated municipal solid waste (MSW) collection also in ready-built urban areas. How well pneumatic systems perform in ready-built areas is, however, an unexplored topic. In this paper, we analyze how a hypothetical stationary pneumatic waste collection system compares economically to a traditional vehicle-operated door-to-door collection system in an existing, densely populated urban area. Both pneumatic and door-to-door collection systems face disadvantages in such areas. While buildings and fixed city infrastructure increase the installation costs of a pneumatic system in existing residential areas, the limited space for waste transportation vehicles and containers cause problems for vehicle-operated waste collection systems. The method used for analyzing the cost effects of the compared waste collection systems in our case study takes into account also monetized environmental effects of both waste collection systems. As a result, we find that the door-to-door collection system is economically almost six times more superior. The dominant cost factor in the analysis is the large investment cost of the pneumatic system. The economic value of land is an important variable, as it is able to reverse the results, if the value of land saved with a pneumatic system is sufficiently high.     

Groundwater Remediation and Aquifer Clean-Up: A Case Study

Groundwater was being remediated with pump and treat technology at a facility where the groundwater was contaminated with commonly used degreaser solvents. Hydraulic conductivity of the heterogeneous residuum was beneficiated by applying pneumatic fracturing technology. The remedial system was controlled and monitored by a sophisticated remote telemetry system. A case history follows.     

Technical feasibility and conceptual design for using supercritical fluid to extract pesticides from aged soil

The demand for processes to clean up contaminated soils without introducing additional contaminants is increasing. One approach to solving this problem is the use of supercritical fluids like carbon dioxide, alone or with cosolvents, to extract contaminants from the soil. Carbon dioxide is readily available, inexpensive, and nonpolluting. Gases exhibit unique properties under supercritical conditions. They retain the ability to diffuse through the interstitial spaces of solid materials, plus they have the solvating power of liquids. Soil cleanup using supercritical fluid extraction (SFE) is being investigated as an alternative/complementary technology to other cleanup methods such as incineration and bioremediation. The objective of the studies included in this article was to collect and analyze data to support use of the SFE technology and to provide the conceptual design and operational processes needed for building a portable treatment unit.     

Surfactant‐Oxidant Co‐Application for Soil and Groundwater Remediation

In situ chemical oxidation (ISCO) typically delivers oxidant solutions into the subsurface for contaminant destruction. Contaminants available to the oxidants, however, are limited by the mass transfer of hydrophobic contaminants into the aqueous phase. ISCO treatments therefore often leave sites with temporarily clean groundwater which is subject to contaminant rebound when sorbed and free phase contaminants leach back into the aqueous phase. Surfactant Enhanced In situ Chemical Oxidation (S‐ISCO^®) uses a combined oxidant‐surfactant solution to provide optimized contaminant delivery to the oxidants for destruction via desorption and emulsification of the contaminants by the surfactants. This article provides an overview of S‐ISCO technology, followed by an implementation case study at a coal tar contaminated site in Queens, New York. Included are data points from the site which demonstrate how S‐ISCO delivers desorbed contaminants without uncontrolled contaminant mobilization, as desorbed and emulsified contaminants are immediately available to the simultaneously injected oxidant for reaction. ©2016 Wiley Periodicals, Inc.     

Augmenting in-situ remediation by soil vapor extraction with six-phase soil heating

The use and performance of soil vapor extraction (SVE) as an in-situ remedial technology has been limited at numerous sites because of both geologic and chemical factors. SVE systems are not well suited to sites containing low permeability soils or sites contaminated with recalcitrant compounds. Six-phase soil heating (SPSH) has been developed by the Battelle Pacific Northwest Laboratories (Battelle) to enhance SVE systems. The technology utilizes resistive soil heating to increase the vapor pressure of subsurface contaminants and to generate an in-situ source of steam. The steam strips contaminants sorbed onto soil surfaces and acts as a carrier gas, providing an enhanced mechanism by which the contaminants can reach an extraction well. Full-scale applications of SPSH have been performed at the U.S. Department of Energy's Savannah River Site in Aiken, South Carolina; at a former fire training site in Niagara Falls, New York; and at Fort Richardson near Anchorage, Alaska. At each site, chlorinated solvents were present in low permeability soils and SPSH was applied in conjunction with SVE. The results of the three applications showed that SPSH is a cost-effective technology that can reduce the time required to remediate a site using only conventional SVE.     

Chemical and Biological Reduction of PCE by Pneumatic Fracturing and Injection of ZVI in Saprolite

This article presents a case study of the source‐area treatment of tetrachloroethene (PCE) in a low‐permeability formation using zero‐valent iron (ZVI). Evidence of the stimulation of biological reduction processes within the treatment zone occurred. Pneumatic fracturing and injection of microscale ZVI slurry in the overburden and weathered bedrock zones was performed at a commercial brownfields redevelopment site in Maryland. A 20,000‐square‐foot source area impacted with PCE at concentrations greater than 15,000 µg/L was treated at depths ranging from 10 to 70 feet bgs. An average ZVI dosage of 0.0024 iron‐to‐soil mass ratio within the overburden zone led to a 75 percent decrease in PCE mass in less than one year. For the weathered bedrock zone, an average 0.0045 iron‐to‐soil mass ratio resulted in a 92 percent decrease in PCE mass during the same period. The reducing environment and hydrogen generated by the ZVI may have stimulated Dehalobacter populations, as evidenced by concentrations up to 10⁴ cells per milliliter measured within the treatment area despite a groundwater pH as high as 9. The biological reductive dechlorination of the chlorinated ethenes explains the temporary increase in trichloroethene and cis‐1,2‐dichloroethene concentrations. © 2013 Wiley Periodicals, Inc.     

Directionally drilled horizontal wells offer cost savings and technical advantages over alternative soil and groundwater remediation systems

Directionally drilled horizontal wells offer the opportunity for significant cost savings and technical advantages over alternative trenched well and vertical well soil and groundwater remediation systems in many cases. The magnitude of the cost savings is a function of the remediation technology deployed and the values placed on the reduction of site impacts, dramatic reduction in the time required to achieve site remediation goals and requirements, the ability of horizontal well remediation to easily treat normally recalcitrant contaminants such as MTBE, and the ability to drill under paved areas, operating plants, residential areas, landfills, lagoons, waterways, ponds, basins, and other areas that are normally difficult or impossible to access with conventional drilling or trenching methods. In addition to improvements in site access capabilities, horizontal wells have been found capable of addressing contaminants that vertical wells do not readily treat, even with the same remediation technology deployed, especially if air‐based remediation technologies are deployed. With biosparging, for example, greater treatment capabilities of horizontal wells over vertical wells are attributed to greater oxygen flux over a broader area, a larger treatment zone, and extremely prolonged residence of groundwater contaminants in the aerobic treatment area, typically months or years. This article describes the use of directionally drilled horizontal wells for application of a variety of treatment technologies and includes costs of various options with a detailed comparison of biosparging options. © 2002 Wiley Periodicals, Inc.     

页岩气压裂返排液处理技术的研究进展

页岩气是一种重要的天然气资源,在其水力压裂开采过程中加入了多种有机添加剂,产生了大量具有高黏度、高COD、高含盐量特性的压裂返排液,常规处理技术难以实现其达标排放或回用。分析了页岩气压裂返排液的组分和特点,归纳总结了成熟的传统处理技术和新型处理技术的特点,提出了优化压裂返排液处理工艺、加强环境信息公开、研发节能环保的新型页岩气压裂技术的未来发展方向,为页岩气压裂返排液无害化、资源化处理技术的研发提供了思路和参考。     

Applications of mulch biowalls—three case studies

Mulch biowalls are proving to be an effective means of generating reducing conditions for the in situ anaerobic reduction of contaminants in groundwater that are amenable to the reduction process. Mulch is an inexpensive and readily available substrate that provides a long‐lasting carbon and electron donor source for the stimulation of the anaerobic reduction process in groundwater. Examples of contaminants that are amenable to the biotic anaerobic reduction process include: chlorinated alkenes and alkanes, explosives, perchlorate, some metals, and petroleum hydrocarbons. The microbial degradation of cellulose fibers (mulch) is arguably the oldest reduction process known and is evident anywhere that plant material, soil, and water are present together. This article presents three case studies discussing three different uses of mulch biowalls to stimulate the anaerobic bioremediation of contaminants in shallow soils and groundwater. © 2009 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.     

A conceptual study on the bio-wall technology: Feasibility and process design

In-situ bioremediation is a process by which contaminants in subsurface environments are biologically eliminated or mineralized; however, it is often difficult to implement. Microbes sparsely distributed in deep soils are incapable of degrading a chemical rapidly; furthermore, fine-pore structures of soils tend to retard the penetration and propagation of these microbes and hinder oxygen transfer. The latter is particularly detrimental to the aerobic growth of microbes, which is often essential for bioremediation. Measures intended to promote bioremediation, such as the addition of surfactants for enhancing dissolution and the application of genetically engineered microbes for accelerating the biodegradation of contaminants, are almost impossible to adopt. This is attributable to the fact that various facets of the bioremediation process (e.g., the distribution of dissolved contaminants, nutrients, and oxygen, and the concentration of microbes) cannot be readily manipulated. This article proposes a novel technology, namely, bio-wall. This technology resorts to an in-situ constructed medium with porosity and organic content greater than those of the original soil for promoting the adsorption and retention of microbes and the biodegradation of contaminants. Moreover, oxygen and nutrients are supplied to the bio-wall to facilitate microbialgrowth. The results of conceptual design study and simulation have revealed that the technology is indeed feasible and, under certain environmental conditions, cost-effective. Particularly noteworthy is the fact that bio-wall can prevent contaminant migration through the enhancement of the biodegradation rate and reduction of the plume-distance, both by several orders of magnitude.     

Immobilization and Encapsulation of Contaminants Using Silica Treatments: A Review

The immobilization and encapsulation of contaminants using silica treatments is an emerging technology for the management of contaminated land. This article reviews the potential of silica treatments for the management of metals, hydrocarbons, and acid mine drainage at contaminated sites; and evaluates the effects of environmental conditions on silica treatment performance. The review demonstrates the potential of silica treatments for managing contaminated land; however, a paucity of research offers only a limited understanding of this technology. Further development of the technology will require additional research evaluating its long‐term performance under a range of environmental conditions. Field‐based experiments and studies investigating potential adverse effects of silica treatments are also necessary to demonstrate the safety, efficacy, and reliability of silica treatments. © 2013 Wiley Periodicals, Inc.     

Status and trends in bioremediation treatment technology

This article is a critical analysis of the treatment potential of bioremediation technology to degrade eight major environmental pollutants, polycyclic aromatic hydrocarbons, phenols, pentachlorophenols, creosote, polychlorinated biphenyls, trichloroethylene, chlorobenzoates, and chlorophenols. The discussion includes information on transformation mechanisms, identification of intermediate metabolites, elucidation of partial or complete pathways, effects of environmental parameters, as well as current and future industrial application. Results indicate that bioremediation used in conjunction with other physical and chemical treatment methodologies can effectively transform most prevalent nonchlorinated organic contaminants and some chlorinated contaminants, such as creosote and pentachlorophenol, into innocuous materials. Successful biodegradation of several other chlorinated organic compounds, notably polychlorinated biphenyls and trichloroethylene, is currently possible only under controlled laboratory conditions. Future successful field applications, however, appear promising.     

Solidification/stabilization for remediation of wood preserving sites: Treatment for dioxins,PCP, creosote,and metals

This article discusses the use of solidification/stabilization (S/S) to treat soils contaminated with organic and inorganic chemicals at wood preserving sites. Solidification is defined for this article as making a material into a freestanding solid. Stabilization is defined as making the contaminants of concern nonmobile as determined from a leaching test. S/S then combines both properties. For more information on S/S in general the reader should refer to other publications (Connors, J.R. [1990]). Chemical fixation and solidification of hazardous wastes. New York: Van Nostrand Reinhold; US Environmental Protection Agency. [1993a]. Engineering bulletin solidification/stabilization of organics and inorganics (EPA/540/S‐92/015); Wiles, C.C. [1989]. Solidification and stabilization technology. In H.M. Freeman [Ed.], Standard handbook of hazardous waste treatment and disposal. New York: McGraw Hill) as this article addresses only wood preserving sites and assumes basic knowledge of S/S processes. For a more general discussion of wood preserving sites and some other remedial options, the reader may wish to refer to a previous EPA publication (US Environmental Protection Agency. [1992a]. Contaminants and remedial options at wood preserving sites [EPA/600/R‐92/182]). This article includes data from the successful remediation of a site with mixed organic/inorganic contaminants, remediation of a site with organic contaminants, and detailed treatability study results from four sites for which successful formulations were developed. Included are pre‐ and post‐treatment soil characterization data, site vaines. ileizdot‐ names (in some cases), treatment formulas used (generic aridproprietary), costs, recommendations, and citatioiis to inore detailed refer‐ en ces. The data presen ted iiidica te that dioxins, pentachlorophepi 01 (PCP), creosote, polycyclic aromatic hydrocarbom (PAHsI, and metals can be treated at moderate cost by the use of S/S techuologp.     

Bioremediation of contaminated soil and sediment by composting

There are many well‐established bioremediation technologies applied commercially at contaminated sites. One such technology is the use of compost material. Composting matrices and composts are rich sources of microorganisms, which can degrade contaminants to innocuous compounds such as carbon dioxide and water. In this article, composting of contaminated soil and sediment was performed on a laboratory bench‐scale pile. Fertilizer was added to increase the nutrient content, and the addition of commercial compost provided a rich source of microorganisms. After maintaining proper composting conditions, the feasibility of composting was assessed by monitoring pH, total volatile solids, total microbial count, temperature, and organic contaminant concentration. The entire composting process occurred over a period of five weeks and resulted in the degradation of contaminants and production of compost with a high nutritional content that could be further used as inocula for the treatment of hazardous waste sites. © 2006 Wiley Periodicals, Inc.     

Best management practices to prevent cross-media transfers during soil cleanup

Cleanup activities often focus on the initial and final concentration levels of contaminants. What happens in-between, during implementation of treatment technologies, has raised major concerns by several environmental groups. To address this issue, the U.S. Environmental Protection Agency (EPA) has undertaken the task of developing a guidance that would identify the potential for cross-media transfer during implementation of various soil treatment technologies and recommend best management practices (BMPs) to prevent or control these cross-media transfers. The soil treatment technologies have been grouped into seven major categories in this effort. This article provides some details of the seven soil treatment technology groups and the general BMPs recommended in the draft BMP guidance document. One case history of existing control practices is also presented in this article and compared with the recommended BMPs.     

Coupling surfactants/cosolvents with oxidants for enhanced DNAPL removal: A review

Surfactants and cosolvents are useful for enhancing the apparent solubility of dense nonaqueous‐phase liquid (DNAPL) compounds during surfactant‐enhanced aquifer remediation (SEAR). In situ chemical oxidation (ISCO) with permanganate, persulfate, and catalyzed hydrogen peroxide has proven to be a cost‐effective and viable remediation technology for the treatment of a wide range of organic contaminants. Coupling compatible remedial technologies either concurrently or sequentially in a treatment train is an emerging concept for more effective cleanup of DNAPL‐contaminated sites. Surfactants are effective for DNAPL mass removal but not useful for dissolved plume treatment. ISCO is effective for plume control and treatment but can be less effective in areas where large masses of DNAPL are present. Therefore, coupling SEAR with ISCO is a logical next step for source‐zone treatment. This article provides a critical review of peer‐reviewed scientific literature, nonreviewed professional journals, and conference proceedings where surfactants/cosolvents and oxidants have been utilized, either concurrently or sequentially, for DNAPL mass removal. © 2010 Wiley Periodicals, Inc.