In situ thermal remediation of DNAPL and LNAPL using electrical resistance heating

Electrical resistance heating (ERH) is an in situ treatment for soil and groundwater remediation that can reduce the time to clean up volatile organic compounds (VOCs) from years to months. The technology is now mature enough to provide site owners with both performance and financial certainty in their site‐closure process. The ability of the technology to remediate soil and groundwater impacted by chlorinated solvents and petroleum hydrocarbons regardless of lithology proves to be beneficial over conventional in situ technologies that are dependent on advective flow. These conventional technologies include: soil vapor recovery, air sparging, and pumpand‐treat, or the delivery of fluids to the subsurface such as chemical oxidization and bioremediation. The technology is very tolerant of subsurface heterogeneities and actually performs as well in low‐permeability silts and clay as in higher‐ permeability sands and gravels. ERH is often implemented around and under buildings and public access areas without upsetting normal business operations. ERH may also be combined with other treatment technologies to optimize and enhance their performance. This article describes how the technology was developed, how it works, and provides two case studies where ERH was used to remediate complex lithologies. © 2005 Wiley Periodicals, Inc.     

Introduction to Therm Net Technology

The Introduction to Therm Net technology is an overview of how radio frequency (RF) beating can be implemented to enhance conventional remediation technologies. Included in the article is a case study of a project conducted in March 1996 at a gasoline release site. The project consisted of a “hot spot” application to reduce BETX concentrations to achieve site closure. The application consisted of RF heating, soil vapor extraction, and groundwater ventilation. A bench scale study was also conducted to measure the effects that RF heating and vapor extraction had on the removal of PAH constitutents from a coal tar sludge. Up to 100 percent reductions were observed for some of the constituents in the study. Also included is a graphical representation of temperature versus vapor pressure for contaminants typically encountered at remediation sites, illustrating that as temperature increases, the removal rate increases.     

Incorporating green and sustainable remediation analysis in coal combustion residuals (CCR) surface impoundment closure decision making

In response to new coal combustion residuals (CCR) disposal regulations, many coal‐fired utilities have closed existing unlined surface impoundments (SIs) that were traditionally used for disposal of CCR. The two primary closure options are closure‐in‐place (CIP), which involves dewatering and capping, and closure‐by‐removal (CBR), which includes excavation, transportation, and disposal of the CCR into a lined landfill. This article provides a methodology and a case study of how green and sustainable remediation concepts, including accounting for the life cycle environmental footprints and the physical risks to workers and community members, can be incorporated into the closure decision‐making process. The environmental impacts, occupational risks, and traffic‐related fatalities and injuries to workers and community members were calculated and compared for closure alternatives at a hypothetical site. The results demonstrated that the adverse impacts of the CBR option were significantly greater than those of the CIP option with respect to the analyzed impact pathways.     

Consensus Oriented Public Relations As A Solution To The Landfill Conflict

The siting of landfills usually meets with the disapproval of residents living in the immediate proximity of potential landfill sites and frequently arouses public protest. Also in Austria, the public's readiness to safeguard their interests has been increasing, thus such conflicts can no longer be avoided. This fact raises the question among future landfill operators, as to how to react in such cases, and how a thus sensitized public can be dealt with. Seen from the viewpoint of communication, landfill operators must direct more attention to public relations.Within a research project at the University of Vienna, we have developed a public relations model which is intended to support a consensus between the landfill operators and the residents immediately affected by the operators' activities. The results prove that the so called "consensus-oriented public relations" approach is principally right. That is, those people who, due to our survey in the communities, could envisage a landfill site being installed, broadly agreed with the landfill operator on the levels of understanding provided by the model.     

Removing gasoline from soil and groundwater through air sparging

Although a soil vapor extraction system (SVES) had effectively remediated the vadose zone soils at a gasoline spill site in Pawtucket, Rhode Island, gasoline remained in the soils below the water table. The state Department of Environmental Management (DEM) closure criteria of 10,000 parts per billion (ppb) were still not met after five years. This article describes how an air sparging system was added to the effort for $57,000, and how after three weeks, closure criteria were achieved.     

Impact: A Model for calculation of soil cleanup levels

The establishment of soil cleanup levels is a primary concern in site remediation projects. Soil cleanup levels provide targets that drive the remediation process from technology selection through closure. Several state regulatory agencies are currently in the process of developing scientifically based soil cleanup standards. The underlying premise in the derivation of such standards is to ensure that the site will not pose a threat to human health and the environment after remediation has been completed. To accomplish this, remediation project managers must consider several contaminant transport pathways. This article presents the salient features of a model named IMPACT, which was developed to assist in the derivation of soil cleanup levels. IMPACT considers the soil-to-groundwater pathway and predicts the cleanup levels in a contaminated soil layer in the vadose zone such that groundwater quality standards are met at any point in the aquifer.     

Cost estimating of the closure/post-closure phase

The U.S. Department of Energy (DOE) is beginning major environmental restoration projects of both active and inactive sites throughout the United States. The problems at the sites include contaminated soils, groundwater and surface waters, structures, and old waste disposal areas. IT Corporation, under the direction of the Office of Independent Cost Estimating (OICE) for DOE, developed a list of environmental problems at the sites and probable cleanup technologies and techniques that could be used. Estimated unit costs were then developed for these cleanup technologies, using available data and references. Some procedures developed were common to many or all cleanup projects. These included site characterization, remedial investigation (RI), feasibility studies (FS), and the closure/post-closure phase. The article will focus on cost estimating of the closure/post-closure phase of a cleanup project. The cost data provided are for budget level or check estimates. Site-specific conditions as well as items peculiar to the environmental industry, such as governmental regulations and community relations, can influence both the cost and duration of a cleanup project.     

Evolution and Innovation of Hydraulic Capture Analysis Methodology

An efficient program for assessing groundwater extraction system capture zones has been developed that can be run on any digitized potentiometric surface. The program was developed in response to the need to simulate particle capture by multiple remediation system elements (i.e., extraction wells, hydraulic barrier, etc.) at a hydrogeologically complex site in California (the Site). The method uses MODPATH software but does not otherwise require a groundwater model. The program called “CapZone FileBuilder” (Capture Zone File Builder) Version 1.0 was created to import digitized potentiometric surfaces and use them to create MODFLOW output files (using native USGS MODFLOW‐2005 codes). CapZone FileBuilder was created using the C# programming language with Visual Studio 2013 as the integrated development environment. The model was applied to a site that has a regulatory requirement for capture analysis as part of an annual remedy‐effectiveness evaluation for groundwater contamination. Previously, capture analysis was highly labor intensive and time consuming, performed using manual flow net analysis or calibration of highly discretized MODFLOW groundwater models. CapZone FileBuilder is now used to perform the capture analysis for this site and is universally applicable to any site with a groundwater potentiometric map. ©2017 Wiley Periodicals, Inc.     

Making the CERCLA Criteria Analysis of Remedial Alternatives More Objective

This article shows how decision analysis techniques assisted decision makers in the critical RI/FS task of technology selection at a specific Superfund site. Each remediation alternative's performance was quantified by creating a set of objective evaluation measures tied to the criteria mandated in the comprehensive Environmental Response, Compensation and Liability Act of 1980. The evaluation measure scores were input into a quantitative decision analysis model used to rank alternatives based on their performance relative to the CERCLA criteria, and to provide insight to the sensitivity of the results to changes in decision maker preferences or technology performance. The model is designed to reflect the site decision maker's preferences and the site-specific characteristics within the framework of the nine CERCLA criteria. This model will give Superfund site decision makers an objective and transparent framework to evaluate remedial technologies.     

A decision support system for assessing landfill performance

Designing environmentally sound landfills is a challenging engineering task due to complex interactions of numerous design variables; such as landfill size, waste characteristics, and site hydrogeology. Decision support systems (DSS) can be utilized to handle these complex interactions and to aid in a performance-based landfill design by coupling system simulation models (SSM). The aim of this paper is to present a decision support system developed for a performance-based landfill design. The developed DSS is called Landfill Design Decision Support System – LFDSS. A two-step DSS framework, composed of preliminary design and detailed design phases, is set to effectively couple and run the SSMs and calculation modules. In preliminary design phase, preliminary design alternatives are proposed using general site data. In detailed design phase, proposed design alternatives are further simulated under site-specific data using SSMs for performance evaluation. LFDSS calculates the required landfill volume, performs landfill base contour design, proposes preliminary design alternatives based on general site conditions, evaluates the performance of the proposed designs, calculates the factor of safety values for slope stability analyses, and performs major cost calculations. The DSS evaluates the results of all landfill design alternatives, and determines whether the design satisfies the predefined performance criteria. The DSS ultimately enables comparisons among different landfill designs based on their performances (i.e. leachate head stability, and groundwater contamination), constructional stability and costs. The developed DSS was applied to a real site, and the results demonstrated the strengths of the developed system on designing environmentally sound and feasible landfills.     

Decision support models for solid waste management: Review and game-theoretic approaches

This paper surveys decision support models that are commonly used in the solid waste management area. Most models are mainly developed within three decision support frameworks, which are the life-cycle assessment, the cost–benefit analysis and the multi-criteria decision-making. These frameworks are reviewed and their strengths and weaknesses as well as their critical issues are analyzed, while their possible combinations and extensions are also discussed. Furthermore, the paper presents how cooperative and non-cooperative game-theoretic approaches can be used for the purpose of modeling and analyzing decision-making in situations with multiple stakeholders. Specifically, since a waste management model is sustainable when considering not only environmental and economic but also social aspects, the waste management bargaining game is introduced as a specific decision support framework in which future models can be developed.     

Multiple system modelling of waste management

Due to increased environmental awareness, planning and performance of waste management has become more and more complex. Therefore waste management has early been subject to different types of modelling. Another field with long experience of modelling and systems perspective is energy systems. The two modelling traditions have developed side by side, but so far there are very few attempts to combine them. Waste management systems can be linked together with energy systems through incineration plants. The models for waste management can be modelled on a quite detailed level whereas surrounding systems are modelled in a more simplistic way. This is a problem, as previous studies have shown that assumptions on the surrounding system often tend to be important for the conclusions. In this paper it is shown how two models, one for the district heating system (MARTES) and another one for the waste management system (ORWARE), can be linked together. The strengths and weaknesses with model linking are discussed when compared to simplistic assumptions on effects in the energy and waste management systems. It is concluded that the linking of models will provide a more complete, correct and credible picture of the consequences of different simultaneous changes in the systems. The linking procedure is easy to perform and also leads to activation of project partners. However, the simulation procedure is a bit more complicated and calls for the ability to run both models.     

Insufficient source area remediation results in the rebound of TCE breakdown products in groundwater

In the early 1990s, a soil removal action was completed at a former disposal pit site located in southern Michigan. This action removed waste oil, cutting oil, and chlorinated solvents from the unsaturated zone. To contain groundwater contaminant migration at the site, a groundwater pump‐and‐treat system comprised of two extraction wells operating at a combined flow of 50 gallons per minute, carbon treatment, and a permitted effluent discharge was designed, installed, and operated for over 10 years. Groundwater monitoring for natural attenuation parameters and contaminant attenuation modeling demonstrated natural attenuation of the contaminant plume was adequate to attain site closure. As a result of incomplete contaminant source removal, a rebound of contaminants above the levels established in the remedial action plan (RAP) has occurred in the years following system shutdown and site closure. Groundwater concentrations have raised concerns regarding potential indoor air quality at adjacent residential properties constructed in the past 9 to 10 years. The only remedial option available in the original RAP is to resume groundwater pump‐and‐treat. To remediate the source area, an alternate remediation strategy using an ozone sparge system was developed. The ozone sparge remediation strategy addresses the residual saturated zone contaminants beneath the former disposal pit and reestablishes site closure requirements without resumption of the pump‐and‐treat system. A pilot study was completed successfully; and the final system design was subsequently approved by the Michigan Department of Environmental Quality. The system was installed and began operations in July 2010. As of the January 2011 monitoring event, the system has shown dramatic improvement in site contaminant concentrations. The system will continue to operate until monitoring results indicate that complete treatment has been obtained. The site will have achieved the RAP objectives when the system has been shut down and meets groundwater residential criteria for four consecutive quarters. © 2011 Wiley Periodicals, Inc.     

Using risk assessment to achieve cost-effective property transfers and site closures for former UST sites

Risk assessment has been increasingly applied as a tool in making risk management decisions that affect cleanup of contaminated sites, property transactions, and liability issues. As a site-specific evaluation, risk assessment takes into account the unique characteristics and intended future uses for site property in evaluating chemical concentrations which may remain in place without risk to public health and the environment. The results of a risk assessment can be used to determine reuse options for a property, facilitate site closure, and reduce liabilities (Copeland and Robles, 1994; Copeland et al., 1993a). This article describes the risk assessment process, the role of risk assessment in determining the need for remedial action and identifying site-specific cleanup goals, and the cost effectiveness of applying risk assessment in remedial decisions. Because of the prevalence of former UST sites throughout the United States, this article focuses on risk assessment and remediation of UST sites. However, the process can be applied at sites where other chemicals have been released. Three case studies are presented to illustrate the application of risk assessment in achieving cost-effective site closure at sites containing leaking underground storage tanks.     

New perspectives in the use of horizontal wells for assessment and remediation

Remediation technologies can sometimes be established, but are not prevalent, for a variety of reasons; however, they can be subject to the forces of change. In some cases, creative economics promotes new uses, but also process improvements can drive new applications and levels of acceptance. This is what is happening with the deployment of horizontal wells for site assessment and remediation. In essence, decreasing costs and a strategic shift, which can be characterized as “greater flexibility,” are two factors that have brought about a resurgence of horizontal well systems. The latter is specifically tied to moving from monolithic single well systems to segmented well systems and this article explains how this is a next‐generation advancement in site assessment and remediation. As one example, nested, discrete horizontal profiling brings additional accuracy to assessment at sites, especially those challenged by access issues and also provides more directed treatment operations with a unique flexibility in dynamic groundwater systems. Also, with horizontal nested well systems, conceptual site models can be significantly enhanced with new perspectives and, depending on the situation, may provide significant economic advantages in deployment. Finally, this technological advancement creates a new paradigm in contrast, or rather as an adjunct, to vertical profiling and high‐resolution site characterization. In fact, it opens up a new strategic approach that can be called high‐resolution contaminant distribution, because flexible horizontal segmented well systems can be used to navigate “up the spine of the plume” providing discretized data sets that illuminate contaminant distribution in new ways.     

Movement of unlined landfill under preloading surcharge

As organic solid waste is decomposed in a landfill and mass is lost due to gas and leachate formation, the landfill settles. Settlement of a landfill interferes with the rehabilitation and subsequent use of the landfill site after closure. This study examined the soil/solid waste movement at the Al-Qurain landfill in Kuwait after 15 years of closure as plans are underway for redevelopment of the landfill site that occupies about a km(2) with an average depth of 8-15m. Field experiments were conducted for 6 mo to measure soil/solid waste movement and water behavior within the landfill using two settlement plates with a level survey access, Casagrande-type piezometers, pneumatic piezometers, and magnetic probe extensometers. Previous results obtained indicated that biological decomposition of refuse continued after closure of the landfill site. The subsurface water rise enhanced the biological activities, which resulted in the production of increasing quantities of landfill gas. The refuse fill materials recorded a high movement rate under the imposed preloading as a result of an increase in the stress state. Up to 55% of the total movement was observed during the first 2 weeks of fill placement and increased to 80% within the first month of the 6-mo preloading test. Pneumatic piezometers showed an increase in water head, which is attributed to the developed pressure of gases escaping during the preloading period.     

System performance assessment of final repository for radioactive wastes using first-order reliability method

When a final option for radioactive waste is determined, it is necessary to demonstrate compliance of disposal system chosen with relevant regulations. Considering the large number of physical and chemical factors involved, the complexity of their interrelationships, and long time periods, a system approach is required. A stochastic analysis is also needed to ensure that these regulatory criteria can be met with confidence. Among a variety of models developed to treat the effect of uncertainty on system performance, the first-order reliability method is suggested as an attractive tool to stochastic problems incorporating any amount of probabilistic information. Based on the first-order approximation, the method can give a probability of failure against a preselected target value, and information concerning the sensitivity of the outcome to variations in the input random variables and their statistical moments. In this paper, for reliable prediction of the performance of repository for radioactive wastes, first-order reliability method is applied in treating the parameter uncertainties of predictive models. First, a thickness of canister corrosion and breach time of canister is calculated using a uniform corrosion model, combined with the diffusional transport modeling of radionuclides in the backfill material. Second, a fractional release rate for each radionuclide is derived from the evaluation of the performance of a waste package which consists of canister and backfill material. Third, a cumulative release rate at the accessible environment is obtained by geosphere transport modeling with the source term given as a fractional release rate. The proposed first-order reliability method can be applicable to a full range of problems occurring in radioactive waste management and beyond.     

Leachate recirculation in a landfill: some insights obtained from the development of a simple 1-D model

The re-introduction of leachate back into the waste can play an important part in landfill management. It can encourage biodegradation by raising the water content and transporting bacteria, nutrients and waste products. It also enables leachate to be stored within the body of the landfill, for example to help minimise temporal variations in the load on a leachate treatment plant. It is helpful for a landfill operator to be able to estimate the rate at which the landfill can accept leachate (the maximum infiltration or injection rate), the storage capacity of the landfill and the leachate retention time. This paper discusses some of the insights obtained from the development and application of a simple conceptual model of leachate recirculation that can be used to estimate key parameter values on the basis of the hydraulic properties of the waste. The model is described, partly validated against a more rigorous numerical analysis, and then used to interpret data obtained from field tests on a real site. The shortcomings of the model in its current form are discussed, and suggestions are made as to how these might be addressed in the context of developing the model as a design tool.     

Conceptual modeling to optimize the haul and transfer of municipal solid waste

Two conceptual mixed integer linear optimization models were developed to optimize the haul and transfer of municipal solid waste (MSW) prior to landfilling. One model is based on minimizing time (h/d), whilst the second model is based on minimizing total cost (euro/d). Both models aim to calculate the optimum pathway to haul MSW from source nodes (waste production nodes, such as urban centers or municipalities) to sink nodes (landfills) via intermediate nodes (waste transfer stations). The models are applicable provided that the locations of the source, intermediate and sink nodes are fixed. The basic input data are distances among nodes, average vehicle speeds, haul cost coefficients (in euro/ton km), equipment and facilities' operating and investment cost, labor cost and tipping fees. The time based optimization model is easier to develop, since it is based on readily available data (distances among nodes). It can be used in cases in which no transfer stations are included in the system. The cost optimization model is more reliable compared to the time model provided that accurate cost data are available. The cost optimization model can be a useful tool to optimally allocate waste transfer stations in a region and can aid a community to investigate the threshold distance to a landfill above which the construction of a transfer station becomes financially beneficial. A sensitivity analysis reveals that queue times at the landfill or at the waste transfer station are key input variables. In addition, the waste transfer station ownership and the initial cost data affect the optimum path. A case study at the Municipality of Athens is used to illustrate the presented models.