Field and laboratory evaluation of the treatment of DNAPL source zones using emulsified zero‐valent iron

Emulsified zero‐valent iron (EZVI) is a surfactant‐stabilized, biodegradable emulsion that forms droplets consisting of a liquid‐oil membrane surrounding zero‐valent iron (ZVI) particles in water. This article summarizes the results obtained during the first field‐scale deployment of EZVI at NASA's Launch Complex 34 (LC34) located on Cape Canaveral Air Force Station, Florida, in August 2002 and presents the results of recent follow‐on laboratory tests evaluating the mechanisms, which contribute to the performance of the technology. The field‐scale demonstration evaluated the performance of EZVI containing nanoscale zero‐valent iron (NZVI) when applied to dense, nonaqueous phase liquid (DNAPL) trichloroethylene (TCE) in the saturated zone. Results of the field demonstration indicate substantial reductions in TCE soil concentrations (greater than 80 percent) at all but two soil boring locations and significant reductions in TCE groundwater concentrations (e.g., 60 percent to 100 percent) at all depths targeted with EZVI. Laboratory tests conducted in 2005 suggest that both NZVI particles and EZVI containing NZVI can provide significant reductions in TCE mass when used to treat TCE DNAPL in small test reactors. However, EZVI was able to reduce TCE concentrations to lower levels than were obtained with NZVI alone, likely as a result of the combined impact of sequestration of the TCE into the oil phase and degradation of the TCE with the NZVI. © 2006 Wiley Periodicals, Inc.     

ERD of Residual TCE DNAPL Achieving Nondetect from a Single Injection of Food‐Grade Waste

Residual dense nonaqueous phase liquid (DNAPL) composed of trichloroethene (TCE) was identified in a deeper interval of an overburden groundwater system at a manufacturing facility located in northern New England. Site hydrostratigraphy is characterized by two laterally continuous and transmissive zones consisting of fully‐saturated fine sand with silt and clay. The primary DNAPL source was identified as a former dry well with secondary contributions from a proximal aboveground TCE storage tank. A single additive‐injection mobilization in 2001 utilizing a food‐grade injectate formulated with waste dairy product and inactive yeast enhanced residual TCE DNAPL destruction in situ by stimulating biotic reductive dechlorination. The baseline TCE concentration was detected up to 97,400 μg/L in the deeper interval of the overburden groundwater system, and enhanced reductive dechlorination (ERD) achieved >99 percent reduction in TCE concentrations in groundwater over nine years with no evidence of sustained rebound. TCE concentrations have remained nondetect below 2.0 μg/L for the last five consecutive sampling rounds between 2013 and 2015. ERD utilizing a food‐grade injectate is a green remediation technology that has destroyed residual DNAPL at the site and achieved similar results at other residual DNAPL sites during both pilot‐ and full‐scale applications. ©2016 Wiley Periodicals, Inc.     

Assessment of in situ thermal treatment for chlorinated organic source zones

The East Gate Disposal Yard (EGDY) at Fort Lewis is the source of a large trichloroethene (TCE) plume at this military installation. Source reduction using thermal treatment was applied using electrical resistance heating. A total of about 5,800 kg of TCE‐equivalent volatile organic compounds (VOCs; TCE and dichloroethene) was extracted during thermal treatment of the three zones selected for source reduction. Pretreatment groundwater TCE concentrations were measured up to 100 ppm. Posttreatment groundwater TCE concentrations within the treatment zones averaged less than 100 ppb. Posttreatment soil TCE concentrations decreased by over 96 percent compared to pretreatment soil concentrations. The overall contaminant flux from EGDY was reduced by an estimated 60 to 90 percent by the source reduction effort. The traditional and new techniques for site characterization and remediation performance monitoring applied at EGDY provide insight for installing, operating, monitoring, and assessing thermal treatment. © 2009 Wiley Periodicals, Inc.     

MULTI INCREMENT® TCE vadose‐zone investigation

MULTI INCREMENT® and discrete sampling strategies were used to estimate the average concentration and the three‐dimensional distribution of TCE in a 3,300‐m³ zone composed of two decision units (e.g., area of concern, population, exposure unit). Authors of this article and a private contractor (Stanley Consultants Inc.), respectively, implemented these two sampling strategies independently. Compared to discrete sampling, the MULTI INCREMENT sampling strategy identified more locations where percent‐level concentrations of TCE have migrated, is more economical, and provided greater data quality. © 2008 Wiley Periodicals, Inc.     

Field Evidence of Dissolution and Degradation Rates Enhancement During ISCR and ENA Treatments of Chlorinated Solvents

This article presents field tests comparing two methods of treatment of chlorinated solvents undertaken at the same site. The site is an automobile factory where two chlorinated solvents (CS) plumes were identified. At the first source, in situ chemical reduction (ISCR) was applied, while at the second one, enhanced natural attenuation (ENA) was used. A set of specific multilevel sampling wells were installed approximately 20 m downgradient of the sources to estimate the efficiency of the treatments. The presence of a low‐permeability layer (source 1) or a thick oil lens (source 2) in the top part of the aquifer prevented the CS from reaching the bottom of the aquifer. These layers led to difficulties treating the contamination. At the ISCR and ENA treatment zones, the concentrations of tetrachloroethene (PCE) and trichloroethene (TCE) did not change significantly, while the concentration of metabolites (cis‐1,2‐DCE, vinyl chloride, and ethene) significantly increased 50 to 150 days after treatment. Due to high concentration of CS in the source zone, a mass balance calculation, including chlorine, was possible. It showed that around 1 to 2 percent of the injected products were used to reduce the CS. A detailed analysis and 1D analytical modeling of CS concentrations showed that the treatment led to a large (two to three times) increase in dissolution of the organic phase. This explains why, despite an efficient treatment, the PCE and TCE concentrations remained virtually unchanged. Degradation rates also increased due to the treatment. Due to some differences in the source‐zone chemistry, it was not possible to differentiate between the ISCR and ENA efficiencies. © 2013 Wiley Periodicals, Inc.     

Remediating TCE‐contaminated groundwater in low‐permeability media using hydraulic fracturing to emplace zero‐valent iron/organic carbon amendment

A field pilot test in which hydraulic fracturing was used to emplace granular remediation amendment (a mixture of zero‐valent iron [ZVI] and organic carbon) into fine‐grained sandstone to remediate dissolved trichloroethene (TCE)‐contaminated groundwater was performed at a former intercontinental ballistic missile site in Colorado. Hydraulic fracturing was used to enhance the permeability of the aquifer with concurrent emplacement of amendment that facilitates TCE degradation. Geophysical monitoring and inverse modeling show that the network of amendment‐filled fractures extends throughout the aquifer volume targeted in the pilot test zone. Two years of subsequent groundwater monitoring demonstrate that amendment addition resulted in development of geochemical conditions favorable to both abiotic and biological TCE degradation, that TCE concentrations were substantially reduced (i.e., greater than 90 percent reduction in TCE mass), and that the primary degradation processes are likely abiotic. The pilot‐test data aided in re‐evaluating the conceptual site model and in designing the full‐scale remedy to address a larger portion of the TCE‐contaminated groundwater plume. © 2012 Wiley Periodicals, Inc.     

Reductive dechlorination of a chlorinated solvent plume in Houston,Texas

Chlorinated solvents such as tetrachloroethene (perchloroethene, PCE) and trichloroethene (TCE) have been extensively used in various industrial applications for many years. Because neither are typically consumed through their various uses, they are often released to the environment through industrial application or disposal. Once released, PCE and TCE tend to migrate downward into groundwater, where they persist. In the current case study, cheese whey was used as a groundwater amendment to facilitate the reductive dechlorination of a chlorinated solvent plume underlying an auto dealer/repair shop in Harris County, Texas. From September 2010 to January 2014, over 32,000 gallons of cheese whey were injected into the subsurface resulting in a marked reduction in oxidation–reduction potential (ORP) and nitrate concentrations, coupled with an increase in ferrous iron concentrations. Statistical trend analyses indicate the primary contaminants, PCE and TCE, as well as the daughter product cis‐1,2‐dichloroethene (cDCE), all exhibited a positive response, as evidenced by statistically decreasing trends, and/or reversal in concentration trends, subsequent to cheese whey injections. Maximum concentrations of PCE and TCE in key test wells decreased by as much as 98.97 percent and 99.17 percent, respectively. In addition, the bacterial genus Dehalococcoides, capable of complete reduction of PCE to non‐toxic ethene, was found to be more abundant in the treatment area, as compared to background concentrations. Because cheese whey is a by‐product of the cheese making process, the cost of the product is essentially limited to transport. This study demonstrates cheese whey to be an effective groundwater amendment at a cost which is orders of magnitude lower than popular industry alternatives.     

Pilot scale testing composite swellable organosilica nanoscale zero‐valent iron—Iron‐Osorb®—for in situ remediation of trichloroethylene

Iron‐Osorb^® is a solid composite material of swellable organosilica with embedded nanoscale zero‐valent iron that was formulated to extract and dechlorinate solvents in groundwater. The unique feature of the highly porous organosilica is its strong affinity for chlorinated solvents, such as trichloroethylene (TCE), while being impervious to dissolved solids. The swellable matrix is able to release ethane after dechlorination and return to the initial state. Iron‐Osorb^® was determined to be highly effective in reducing TCE concentrations in bench‐scale experiments. The material was tested in a series of three pilot scale tests for in situ remediation of TCE in conjunction with the Ohio Environmental Protection Agency at a site in central Ohio. Results of these tests indicate that TCE levels were reduced for a period of time after injection, then leveled out or bounced back, presumably due to depletion of zero‐valent iron. Use of tracer materials and soil corings indicate that Iron‐Osorb^® traveled distances of at least 20 feet from the injection point during soil augmentation. The material appears to remain in place once the injection fluid is diluted into the surrounding groundwater. Overall, the technology is promising as a remediation method to treat dilute plumes or create diffuse permeable reactive barriers. Keys to future implementation include developing injection mechanisms that optimize soil distribution of the material and making the system long‐lasting to allow for continual treatment of contaminants emanating from the soil matrix. © 2011 Wiley Periodicals, Inc.     

Matrix Diffusion Modeling Applied to Long‐Term Pump‐and‐Treat Data: 1. Method Development

Despite the installation in the 1980s and 1990s of hydraulic containment systems around known source zones (four slurry walls and ten pump‐and‐treat systems), trichloroethene (TCE) plumes persist in the three uppermost groundwater‐bearing units at the Middlefield‐Ellis‐Whisman (MEW) Superfund Study Area in Mountain View, California. In analyzing TCE data from 15 recovery wells, the observed TCE mass discharge decreased less than an order of magnitude over a 10‐year period despite the removal of an average of 11 pore volumes of affected groundwater. Two groundwater models were applied to long‐term groundwater pump‐and‐treat data from 15 recovery wells to determine if matrix diffusion could explain the long‐term persistence of a TCE plume. The first model assumed that TCE concentrations in the plume are controlled only by advection, dispersion, and retardation (ADR model). The second model used a one‐dimensional diffusion equation in contact with two low‐permeability zones (i.e., upper and lower aquitard) to estimate the potential effects of matrix diffusion of TCE into and out of low‐permeability media in the plume. In all 15 wells, the matrix diffusion model fit the data much better than the ADR model (normalized root mean square error of 0.17 vs. 0.29; r² of 0.99 vs. 0.19), indicating that matrix diffusion is a likely contributing factor to the persistence of the TCE plume in the non‐source‐capture zones of the MEW Study Area's groundwater‐extraction wells. © 2013 Wiley Periodicals, Inc.     

Remediation of a Diffuse Trichloroethene Plume in an Urban Setting

During an environmental assessment of a former fleet vehicle maintenance facility located in Jacksonville, Florida, dissolved trichloroethene (TCE) concentrations exceeding the Florida groundwater standard (3 micrograms per liter) were detected at a depth of 40 feet (12 meters) below land surface (bls). A plume was delineated that measured approximately 600 feet (183 meters) by 150 feet (46 meters), extending across a major road and onto adjacent properties. Shaw Environmental, Inc., which was acquired by CB&I in February 2012, performed pilot tests with in situ oxygen curtain (iSOC), and the injection of Anaerobic Biochem Plus (ABC+), a mixture of lactates, a phosphate buffer, fatty acids, and zero‐valent iron. Based on the pilot‐test results, ABC+ appeared the more effective of the two methods and was selected for full‐scale implementation. In February 2011, Shaw Environmental, Inc. and a subcontractor used direct‐push technology to inject ABC+ in 120 borings. By September 2011, the treatment succeeded in lowering the concentrations of TCE to below the Florida standard in all impacted wells. Subsequent sampling events indicate that TCE concentrations have remained below the standard, but sampling continues for iron, which is decreasing but remains slightly elevated. © 2013 Wiley Periodicals, Inc.     

Treatment of mixed contamination in water using cyclodextrin‐based materials

This study investigated the effectiveness of a cyclodextrin‐based solid material for the removal of mixed dissolved contaminants. The solid material was prepared by condensation of α‐cyclodextrin. The removal efficiency was found to be 70 percent for total heavy metals (cadmium, lead, chromium, iron, nickel, cobalt, and mercury) to 98 percent for polychlorinated biphenyls (PCBs). The optimum pH for heavy metal removal was approximately 5 and for PCBs it was in the range of 5–7. All of these heavy metals were successfully recovered from the spent cyclodextrin‐based material using nitric acid, allowing the material to be reused for further passes. The results also showed that the presence of alkaline and alkaline earth metals did not have a significant effect on the removal efficiency, indicating that the cyclodextrin‐based material could selectively remove the heavy metals of concern without being consumed by alkaline and alkaline‐earth metals. © 2006 Government of Canada.     

Treatment of mercury‐contaminated soils with activated carbon: A laboratory,field, and modeling study

A series of laboratory batch leaching tests was conducted to evaluate the performance of different activated carbons in stabilizing mercury in soils. Based on the results of these experiments, an amendment application rate of 5 percent powdered activated carbon (PAC) was selected for in situ field application at a former industrial facility. A geochemical model was also developed to simulate the interactions between mercury and activated carbon in vadose‐zone soils. Modeling was used to (1) better understand possible mercury sequestration mechanisms and (2) predict the in situ performance of PAC. Model results indicate dissolved mercury concentrations observed in batch tests are consistent with equilibrium partitioning of mercury between dissolved organic matter, soil organic matter, and PAC. Activated carbon is predicted to reduce dissolved mercury concentrations via two mechanisms: (1) the formation of stable mercury complexes on PAC surfaces and (2) the direct adsorption of dissolved organic matter that would otherwise be available for mercury dissolution. Study results demonstrate PAC effectiveness for site soils with mercury concentrations below 200 mg/kg. © 2010 Wiley Periodicals, Inc.     

CSIA of TCE and Daughter Products With Multiple Sources,Multiple Attenuation Mechanisms,and Low Ethene

One of the most often asked questions from regulators considering monitored natural attenuation (MNA) for a site is if there are mechanisms in situ that can completely detoxify the contaminant of concern. This article describes a method that uses data derived from compound‐specific isotope analysis (CSIA) to investigate if complete in situ degradation of trichloroethene (TCE) has occurred. MNA was the selected remediation strategy at the former England Air Force Base (fEAFB) in Louisiana. Previously declining concentrations of TCE, 1,2‐cis‐dichloroethene, and vinyl chloride had increased in selected wells, and less ethene was observed than expected on the basis of mass balance. Reductive dechlorination, partial or otherwise, could not explain observed trends, so the question at fEAFB had become: Was there an in situ mechanism for complete TCE detoxification (i.e., complete degradation to innocuous end products) at the site? CSIA was used for investigating this question at fEAFB. A previously developed formalism was adapted to interpret the CSIA data to answer the question. Standard interpretation assuming only reductive dechlorination demonstrated detoxification in 9 of the 15 contaminated wells, whereas the interpretation developed here did so in 14. © 2014 Wiley Periodicals, Inc.     

Enhanced anaerobic bioremediation of a TCE source at the Tarheel Army Missile Plant using EOS

EOS, or emulsified oil substrate, was used to stimulate anaerobic biodegradation of trichloroethene (TCE) and tetrachloroethene (PCE) at a former Army‐owned manufacturing facility located in the Piedmont area of North Carolina. Previous use of chlorinated solvents at the facility resulted in soil and groundwater impacts. Ten years of active remediation utilizing soil vacuum extraction and air sparging (SVE/AS) were largely ineffective in reducing the TCE/PCE plume. In 2002, the Army authorized preparation of an amended Remedial Action Plan (RAP) to evaluate in situ bioremediation methods to remediate TCE in groundwater. The RAP evaluated eight groundwater remediation technologies and recommended EOS as the preferred bioremediation alternative for the site. Eight wells were drilled within the 100 × 100 feet area believed to be the primary source area for the TCE plume. In a first injection phase, dilute EOS emulsion was injected into half of the wells. Distribution of the carbon substrate through the treatment zone was enhanced by pumping the four wells that were not injected and recirculating the extracted water through the injection wells. The process was repeated in a second phase that reversed the injection/extraction well pairs. Overall, 18,480 pounds of EOS were injected and 163,000 gallons of water were recirculated through the source area. Anaerobic groundwater conditions were observed shortly after injection with a corresponding decrease in both PCE and TCE concentrations. Dissolved oxygen, oxidation‐reduction potential, and sulfate concentrations also decreased after injection, while TCE‐degradation products, ferrous iron, and methane concentrations increased. The reduction in TCE allowed the Army to meet the groundwater remediation goals for the site. Approximately 18 months after injection, eight wells were innoculated with a commercially prepared dechlorinating culture (KB‐1) in an attempt to address lingering cis‐1,2‐dichloroethene (cis‐DCE) and vinyl chloride (VC) that continued to be observed in some wells. Dehalococcoides populations increased slightly post‐bioaugmentation. Both cis‐DCE and VC continue to slowly decrease. © 2007 Wiley Periodicals, Inc.     

Chlorinated Solvent Treatment Wetland

A first‐of‐its‐kind wetland restoration project was completed in October 2000 to treat trichloroethene‐(TCE‐)impacted groundwater from a former manufacturing facility prior to discharge into a highly valued recreational surface water body in the upper Midwest. This article summarizes the design, construction, operation, and effectiveness of the restored wetland. The groundwater‐surface water discharge zone at the site was restored as a wetland to improve the natural degradation of TCE and subsequent degradation by‐products. For the past 11 years, the treatment wetland performance was evaluated by monitoring the wetland vegetation, wetland hydraulics, and water chemistry. Water quality data have been used to assess the wetland geochemistry, TCE and TCE‐degradation by‐product concentrations within the wetland, and the surface water quality immediately downgradient of the wetland. The treatment wetland has been performing according to design, with TCE and TCE‐degradation by‐products not exceeding surface water criteria. The monitoring results show that TCE and TCE‐degradation by‐products are entering the treatment wetland via natural hydraulic gradients and that the geochemistry of the wetland supports both reductive dechlorination (anaerobic degradation) and cometabolic degradation (aerobic degradation) of TCE and TCE‐degradation by‐products: cis‐ and trans‐1,2‐dichloroethene and vinyl chloride. © 2013 Wiley Periodicals, Inc.     

表面活性剂强化超滤法处理亚甲基蓝废水

采用无机陶瓷超滤膜和低浓度阴离子表面活性剂十二烷基苯磺酸钠(SDBS)处理亚甲基蓝(MB)模拟废水,考察了废水中SDBS、MB浓度及废水pH对超滤过程的影响.实验结果表明:SDBS浓度影响MB在最大吸收波长处的吸光度值;当废水中SDBS浓度为1.20 mmol/L(即25℃时的临界胶束浓度)、废水中MB浓度为1.00 mmol/L、废水pH为9.0时,超滤效果最好;在此条件下,透过液中SDBS浓度和MB浓度分别为0.06 mmoL/L和0.01 mmol/L,MB的截留率为99.2%,膜通量为309.6 L/(m~2·h).SDBS对MB超滤过程的强化机理主要为MB与SDBS形成结合体析出及SDBS胶束的增溶作用.     

Optimised product and water recovery from batch-production rinsing waters

Product concentrate can be recovered from rinsing waters [cleaning in place (CIP)] of surfactant and detergent batch production processes by using ultrafiltration and nanofiltration membranes. The problem in designing a separation process for the rinsing water is that the different compositions of the CIP-batches result in different treatment characteristics. The product formulations considered in this study are based on anionic and non-ionic surfactants. Detergents additionally contain salts, dyes, perfumes and solvents. Product solution enrichment by means of ultrafiltration membranes was investigated. Flux behaviour and selectivity are modelled on the basis of the experimental results as a basis for economic optimisation of the recovery process. The model is validated with the experimental data. The simulation model is used to calculate optimal design and operation parameters for a multi-stage UF concentration plant. An optimal number of feed-and-bleed-stages can be found under economic constraints. For water purification, a nanofiltration step has to be implemented for some of the surfactant CIP-batches. Depending on the separation characteristics, the batches are treated with a single (UF) or two-step membrane process (NF/ UF).     

An evaluation of the performance of multiple passive diffusion devices for indoor air sampling of VOCs

The United States Environmental Protection Agency is considering recommending longer‐term sampling to achieve more accurate time‐weighted‐average detections for indoor air monitoring of volatile organic chemicals. The purpose of the research presented herein was to compare longer sampling times using passive diffusion samplers to the results from shorter‐term testing periods using sorbent tubes and low‐flow pumps (US EPA Method TO‐17) at great frequency for trichloroethene (TCE) in indoor air. A controlled release of TCE in a large room allowed for over two‐orders‐of‐magnitude daily concentration variability over the course of the two‐week monitoring event. The daily concentration measurements by US EPA Method TO‐17 and the passive diffusion samplers were performed in triplicate and had excellent reproducibility. The results of daily tests were averaged and compared with four passive diffusion devices exposed to indoor air for three, seven, ten, and fourteen days in accordance with ASTM D6196‐02. A specific uptake rate for each of the passive devices at the four different time intervals and the statistical significance of the time‐varying uptake rates were evaluated. The performance of each passive diffusion device was determined using a statistical performance criterion. The average concentration for all of the exposure periods could be reliably predicted using the established uptake rates for two of the four passive devices. © 2009 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.     

Treatment of tar pond sludge in a circulating fluidized bed combustor

A series of tests to burn mixtures of tar pond sludge and coal was carried out using a mini‐circulating fluidized bed combustor (mini‐CFBC). During the tests, carbon dioxide, oxygen, carbon monoxide, sulfur dioxide, and nitrogen oxides in the flue gas were monitored continuously. Stack gas sampling was carried out for hydrochloric acid, metals, particulate matter, volatile organic compounds (VOCs), total hydrocarbons, semivolatile organic compounds (SVOCs), dioxins and furans (PCDD/Fs), and polychlorinated biphenyls (PCBs). Results showed that hydrochloric acid, mercury, particulate matter, PCDD/F, and metal concentrations were all below both the current limits and the gas‐release limits to be implemented in 2008 in Canada. The new 2008 emissions limits will reduce the maximum allowable concentrations of most pollutants by half. Thus, the maximum concentration for particulate matter will be 5 mg/m³ (from the current maximum concentration of 10 mg/m³);the maximum concentration for hydrochloric acid will be 5 mg/m³ (from 10 mg/m³); and the‐maximum concentration for dioxins and furans will be 0.032 ng/m toxic equivalent (from 0.08 ng/mcurrently). Sulfur capture efficiency was 89–91 percent. The percentage of fuel nitrogen converted to nitrogen oxides was of the order of 4.7 to 6.1, which is significantly lower than that of conventional pulverized coal‐fired boilers and well within the normal range for fluidized bed combustors (FBCs). PCB and polycyclic aromatic hydrocarbon (PAH) emissions levels were comparable or lower than levels reported in the literature for industrial‐scale FBCs. VOC concentrations were low except for benzene, for which the concentration was higher than that reported for pulverized coal‐fired utility boilers. In addition, carbon monoxide concentration was high at 1,200 to 2,200 parts per million. However, these carbon monoxide concentrations are typical of the mini‐CFBC firing coal. The trials showed that for 10 percent by weight tar pond sludge mixed with 90 percent by weight coal, the combustion was both stable and efficient. The tests demonstrated that CFBC technology is an environmentally sound option for eliminating tar pond waste sludge. © 2005 Wiley Periodicals, Inc.