Preparation and Biodegradation of Starch/Polycaprolactone Films

Starch granules were modified with trisodium trimetaphosphate (TSTP) and characterized by P³¹-NMR, FTIR and DSC. Seventy-micron films were prepared from modified starch and polycaprolactone blends by solvent casting technique. Three different types of films—PCL (100% polycaprolactone), MOD-ST/PCL (50% modified starch and 50% polycaprolactone blend) and NONMOD-ST/PCL (50% nonmodified starch and 50% polycaprolactone blends)—were prepared, and their thermal, mechanical, and morphologic properties were investigated to show the increased performance of PCL with the addition of starch and also the effect of modification. It was observed that with the addition of starch the Young's modulus of polycaprolactone was increased and became less ductile, whereas tensile strength and elongation at break values decreased. Biodegradation of these films was inspected under different aerobic environments with the presence of Pseudomonas putida, activated sludge, and compost. It was observed that whereas P. putida had almost no effect on degradation during 90 days, with the presence of activated sludge, considerable deformation of films was observed even in the first 7 days of degradation. In a compost environment, degradation was even faster, and all polymer films were broken into pieces within first 7 days of degradation and no film remained after 15 days.     

Kinetic Study of Naphthalene Biodegradation in Aerobic Slurry Phase Microcosms for the Optimisation of the Process

The research was focused on the slurry-phase biodegradation of naphthalene. The biodegradation process was optimised with preliminary experiments in slurry aerobic microcosms. From soil samples collected on a contaminated site, a Pseudomonas putida strain, called M8, capable to degrade naphthalene was selected. Microcosms were prepared with M8 strain by mixing non-contaminated soil and mineral M9 medium. Different experimental conditions were tested varying naphthalene concentration, soil:water ratio and inoculum density. The disappearance of hydrocarbon, the production of carbon dioxide, and the ratio of total heterotrophic and naphthalene-degrading bacteria were monitored at different incubation times. The kinetic equation that best fitted the disappearance of contaminant with time was determined. The results showed that the isolated strain enhanced the biodegradation rate with respect to the natural biodegradation.     

The Effect of Interaction Between White-rot Fungi and Indigenous Microorganisms on Degradation of Polycyclic Aromatic Hydrocarbons in Soil

White-rot fungi applied for soil bioremediation have to compete with indigenous soil microorganisms. The effect of competition on both indigenous soil microflora and white-rot fungi was evaluated with regard to degradation of polycyclic aromatic hydrocarbons (PAH) with different persistence in soil. Sterile and non-sterile soil was artificially contaminated with ¹⁴C-labeled PAH consisting of three (anthracene), four (pyrene, benz[a]anthracene) and five fused aromatic rings (benzo[a]pyrene, dibenz[a,h]anthracene). The two fungi tested,Dichomitus squalens and Pleurotus ostreatus, produced similar amounts of ligninolytic enzymes in soil, but PAH mineralization by P. ostreatus was significantly higher. Compared to the indigenous soil microflora, P.ostreatus mineralized 5-ring PAH to a larger extent, while the indigenous microflora was superior in mineralizing 3-ring and 4-ring PAH. In coculture the special capabilities of both soil microflora and P. ostreatus were partly restricted due to antagonistic interactions, but essentially preserved. Thus, soil inoculation with P. ostreatus significantly increased the mineralization of high-molecular-weight PAH, and at the same time reduced the mineralization of anthracene and pyrene. Regarding the mineralization of low-molecular-weight PAH, the stimulation of indigenous soil microorganisms by straw amendment was more efficient than application of white-rot fungi.     

Degradation of L- and DL-lactic acid oligomers in the presence ofFusarium moniliforme andPseudomonas putida

Poly(-alkanoates) derived from lactic acid enantiomers are known to degrade easily hydrolytically in aqueous media. The ability of two microorganisms, a filamentous fungus,Fusarium moniliforme, and a bacterium,Pseudomonas putida, to assimilate the degradation by-products of poly(lactic acid) (PLA), namely, lactic acid, lactyllactic acid dimers, and higher oligomers, was investigated in liquid culture. To distinguish the influence of chirality on bioassimilation, two series of substrates were considered which derived from the racemic and the L-form of lactic acid, respectively. The fate of these compounds was monitored by HPLC. Under the selected conditions,DL- andL-lactic acids were totally used by the two microorganisms regardless of the enantiomeric composition. Both microorganisms degraded the LL-dimer rather rapidly. However,F. moniliforme acted more rapidly thanP. putida. It is likely that the DD-dimer also biodegraded but at a slower rate, especially in the case of the fungi. Higher racemic oligomers were slowly assimilated by the two microorganisms, whereas higher L-oligomers appeared biostable probably because of their crystallinity. A synergistic effect was observed when both microorganisms were present in the same culture medium containing racemic oligomers.Presented at the 4th International Workshop on Biodegradable Plastics and Polymers, October 11–14, 1995. Durham, New Hampshire.     

Assessment of Population Dynamics of Specific Strains in Groundwater Bioaugmentation Experiments by Two Different Molecular Techniques

A set of microcosm experiments was performed to understand the behaviour of special degraders in bioaugmentation experiments. In the experiments the following chlorobenzene degraders were used: the genetically modified Pseudomonas putida F1CC, and the two wild-type strains Pseudomonas putida GJ31 and Pseudomonas aeruginosa RHO1. These strains were used at an initial cell density of 10⁵ cells mL^–1 groundwater which had been spiked with 1,2-dichlorobenzene (1,2-DCB), 1,4-dichlorobenzene (1,4-DCB) and, as main contaminant, chlorobenzene (CB). The population dynamics and behaviour of the three special degraders within the groundwater microcosms were studied by single-strand conformation polymorphism (SSCP) analysis of 16S rDNA fragments amplified from directly extracted community DNA and fluorescent in situ hybridization (FISH) with species-specific probes. RHO1 disappeared after 4 days as detected by FISH in contrast to SSCP-detection where RHO1 could be found during the whole incubation time. Whereas GEM F1CC and wild-type strain GJ31 survived the whole incubation for 20 days. With both methods we were able to detect all strains with high specificity among the indigenous microbial community. The data sets obtained from SSCP analysis and FISH were highly correlated. Specific band intensity within the SSCPfingerprints and the cell counts determined by FISH gave a quantitative overview about the introduced strains.     

Changes in Extractability of Cr and Pb in a Polycontaminated Soil After Bioaugmentation With Microbial Producers of Biosurfactants, Organic Acids and Siderophores

Partly because of the low bioavailability of metals, the soil cleaning-up using phytoremediation is usually time-consuming. In order to enhance the amount of metals at the plant's disposal, the soil bioaugmentation coupled together with phytoextraction is an emerging technology. In this preliminary work, two agricultural soils which mainly differed in their Cr, Hg and Pb contents (LC, low-contaminated soil; HC, high-contaminated soil) were bioaugmented in laboratory conditions by either bacterial (Bacillus subtilis, Pseudomonas aeruginosa, Pseudomonas fluorescens or Ralstonia metallidurans) or fungal inocula (Aspergillus niger or Penicillium simplicissimum) and incubated during three weeks. The LC soil pots bioaugmented with A. niger and P. aeruginosa contained higher concentrations of Cr (0.08 and 0.25 mg.kg⁻¹ dw soil) and Pb (0.25 and 0.3 mg.kg⁻¹ dw soil) in the exchangeable fraction F1 (extraction with MgCl₂) by comparison with the non-bioaugmented soil where neither Cr nor Pb was detected. Conversely, immobilization of Cr and Pb in the soil were observed with the other microorganisms. The soil bioaugmentation not only modified the metal speciation for the most easily extractable fractions but also modified the distribution of metals in the other fractions, to a lesser extent nevertheless. The difference in microbial concentrations between the bioaugmented or not HC soils reached up to 1.8 log units. Thus the microorganisms that we chose for the soil bioaugmentation were competitive towards the indigenous microflora. The PCA analysis showed close positive relationships between the microorganisms which potentially produced siderophores in the soil and the amount of Cr and Pb in the fraction F1.     

Pseudomonas sp. (Strain 10–1B): A potential inoculum candidate for green and sustainable remediation

Soil pollution caused by polycyclic aromatic hydrocarbons (PAHs) is a consequence of various industrial processes which destabilizes the ecosystem. Bioremediation by bacteria is a cost‐effective and environmentally safe solution for reducing or eliminating pollutants in soils. In the present study, we artificially polluted agricultural soil with used automobile engine oil with a high PAH content and then isolated bacteria from the soil after 10 weeks. Pseudomonas sp. strain 10–1B was isolated from the bacterial community that endured this artificial pollution. We sequenced its genomic DNA on Illumina MiSeq sequencer and evaluated its ability to solubilize phosphate, fix atmospheric nitrogen, and produce indoleacetic acid, in vitro, to ascertain its potential for contribution to soil fertility. Its genome annotation predicted several dioxygenases, reductases, ferredoxin, and Rieske proteins important in the ring hydroxylation initiating PAH degradation. The strain was positive for the soil fertility attributes evaluated. Such combination of attributes is important for any potential bacterium partaking in sustainable bioremediation of PAH‐polluted soil.     

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.     

Synthesis of poly(hydroxyalkanoate) from hydrolyzed linseed oil

Pseudomonas putida was grown on a mixture of long-chain fatty acids obtained by hydrolysis of linseed oil. A poly(3-hydroxyalkanoate) containing 51.2% of unsaturated monomers was obtained. A considerable percentage (13.6%) was constituted by C₁₄ and C₁₆ monomers containing three double-bonds in the side chains. The polymer showed a high tendency to crosslink when it was kept in presence of air. In the crosslinked polymer no polyunsaturated monomers could be detected.     

Assessing detoxification and degradation of wood preserving and petroleum wastes in contaminated soil

This study was undertaken to evaluate in-situ soil bioremediation processes, including degradation and detoxification, for two types of wood preserving wastes and two types of petroleum refining wastes at high concentrations in an unacclimated soil. The soil solid phase, water soluble fractions of the soil, and column leachates were evaluated. Two bioassays, a mutagenic potential asay (Ames assay) and an aqueous toxicity assay (Microtox^™ assay) were used to evaluate detoxification; high performance liquid chromatography was used to evaluate chemical concentration and degradation for eight polynuclear aromatic hydrocarbons (PAHs). The group of non-carcinogenic PAHs studied demonstrated greater degradation, ranging from 54–90% of mass added for the four wastes; the carcinogenic group of PAHs studied exhibited degradation ranging from 24–53% of mass added. Although no mutagenicity was observed in waste/soil mixtures after one year of treatment, Microtox^™ toxicity was observed in water soluble fractions and in leachate samples. An integration of information concerning degradation of hazardous constituents with bioassay information represents an approach for designing treatability studies and for evaluating the effectiveness of in-situ bioremediation of contaminated soil/waste systems. When combined with information from waste, site and soil characterization studies, the data generated in treatability studies may be used in predictive mathematical models to: (1) evaluate the effectiveness of use of on-site bioremediation for treatment of wastes in soil systems; (2) develop appropriate containment structures to prevent unacceptable waste transport from the treatment zone; and (3) design performance monitoring strategies.     

Biosorption study of potential fungi for copper remediation from Peninsular Malaysia

The ability to grow in heavy metal contaminated areas and absorb heavy metals from the environment make fungi a potentially viable biological‐based technology for remediating hazardous heavy metals in soil. In this study, 10 fungi from a copper (Cu)‐polluted area in Malaysia were isolated, with the four highest growth fungi identified as Simplicillium subtropicum, Fusarium solani, Aspergillus tamari, and Aspergillus niger. Results from toxicity and biosorption testing showed that A. niger and F. solani grew the fastest in the presence of Cu, but exhibited lower Cu uptake per unit of biomoass. In contrast, A. tamarii and S. subtropicum had lower growth rates, but showed better uptake of Cu per unit of biomass. S. subtropicum was identified as the best species for bioremediation because it had the highest Cu uptake and positive growth measured in the presence of Cu at concentrations below 100 mg/L. A niger proved to be most suitable for bioremediation if the concentration of Cu exceeds 100 mg/L.     

Natural and Artificial Functionalized Biopolyesters. II. Medium-Chain Length Polyhydroxyoctanoates from Pseudomonas Strains

Sixteen Pseudomonas strains have been tested with a view to developing medium-chain length polyhydroxyalkanoates. Four strains were selected and it is shown that their ability for producing three different polyesters with variable properties was dependent on the strains and substrates. Otherwise, Pseudomonas oleovorans was grown on a mixture of sodium octanoate and undecenoate salts at a 90/10 mol/mol ratio. The corresponding copolymer, bearing lateral double bonds, was chemically modified in the carboxy group. Finally, the ability to tailor-make functional bacterial polyesters aimed at temporary therapeutic applications is demonstrated.     

Production of Poly(3-hydroxyalkanoate)s by Pseudomonas putida Cultivated in a Glycerol/Nonanoic Acid-Containing Medium

The biosynthesis of poly(3-hydroxyalkanoate) (PHA) by Pseudomonas putida (JCM6160) cultivated in a medium containing glycerol, nonanoic acid, or a glycerol/nonanoic acid mixture as the sole carbon sources was investigated. The PHA content was ~20 % when glycerol was the carbon source. This relatively low content can be attributed to the glycerol end-cap effect and the absence of enzymes that can directly synthesize PHA from acetyl CoA, which is the major metabolite of glycerol. Fatty acids, containing even numbered carbons, are synthesized from acetyl CoA, and they can be used as substrates for PHA synthesis. However, this process also results in decreasing PHA content as fatty acids are siphoned off into other pathways. However, addition of 5 mM nonanoic acid into a 20 mM glycerol-containing medium dramatically increased the PHA content in P. putida, which was 1.3 times larger than the sum of the values found when glycerol and nonanoic acid were each used as the sole carbon source. The PHA, synthesized in the glycerol/nonanoic acid medium, contains 3-hydroxy alkanoate units that have 5, 6, 7, 8, 9, or 10 carbons. The units that contain the even numbered carbons are derived from fatty acids that were produced from glycerol; whereas, the PHA units with the odd numbered carbons are derived from nonanoic acid. Pentanoate units were also found in the polyester derived from glycerol and nonanoic acid, and must have been synthesized indirectly via β-oxidation of nonanoic acid with the assistance of glycerol because pentanoate units were not found in PHA when P. putida was cultivated in the presence of only nonanoic acid.     

Landfill Leachate Ecotoxicity Experiments using Lemna minor

The effects of varying concentrations of landfill leachate on the growth, frond area, chlorophyll content and fluorescence of four strains of Lemna minor were assessed. Growth fluorescence and frond chlorophyll content decreased after seven days exposure to leachate, although responses differed between the strains and end parameters. A L. minor bioassay was used to assess leachate toxicity and the effectiveness of a constructed wetland treatment system and pre-treatment aeration and settlement in reducing toxicity. Pre-treatments were found to significantly reduce toxicity, so their incorporation in any treatment system may increase pollutant stripping.     

Biodegradability of chitin- and chitosan-containing films in soil environment

The biodegradation of polyethylene-chitin (PE-chitin) and polyethylene-chitosan (PE-chitosan) films, containing 10% by weight chitin or chitosan, by pure microbial cultures and in a soil environment was studied. Three soil-inhabited organsims,Serratia marcescens, Pseudomonas aeruginosa, andBeauveria bassiana were able to utilize chitin and chitosan in prepared PE-chitin and PE-chitosan films after eight weeks of incubation at 25°C in a basal medium containing no source of carbon or nitrogen. In a soil environment, the biodegradation of those films was studied and compared with a commercial biodegradable film containing 6% by the weight of corn starch. In soil placed in the lab, 73.4% of the chitosan and 84.7% of the chitin in the films were degraded, while 46.5% of the starch in the commercial film was degraded after six months of incubation. In an open field, 100% of the chitin and 100% of the chitosan in the films were degraded, but only 85% of the starch in the commercial film was degraded after six months of incubation. The weight of controls, (polyethylene films), remained mainly stable during the incubation period. Both PE-chitin and PE-chitosan films degraded at a higher rate than the commercial starch-based film in a soil environment indicating the potential use of chitin-based films for the manufacturing of biodegradable packaging materials.     

Use of bio‐traps with multiple substrates and electron acceptors to optimize remediation

Bio‐Traps® were used to investigate biodegradation of benzene, methyl tertiary butyl ether (MTBE), and tertiary butyl alcohol (TBA) under different conditions at a fractured rock site to aid the selection of a bioremediation approach. The Bio‐Traps were amended with the ¹³C‐labeled constituent of interest and sampled sequentially at 15‐, 30‐, 60‐, and 90‐day intervals. The conditions tested were biodegradation during operation of an air sparge system, amendment with nitrate during the air sparge operation, anaerobic biodegradation with the system turned off, and anaerobic biodegradation with nitrate amendment. There was increased biomass with nitrate amendment whether the air sparge system was on or off for all the constituents of interest. The diversity of the microbial community, determined by phospholipid fatty acid analysis, decreased with nitrate amendment as more specialized degraders were selected. The most negative indicators of potential biodegradation performance were observed with the anaerobic control. There was less biomass overall, less incorporation of ¹³C into biomass, and decreased membrane permeability. As testing with additional amendments continues at the site, it is not yet certain which treatment might be selected for bioremediation, but the Bio‐Trap tests thus far have identified that the in situ, natural attenuation condition is least favorable for biodegradation. © 2009 Wiley Periodicals, Inc.     

A universal design approach for in situ bioremediation developed from multiple project sites

This article describes a design approach that has been developed for bioremediation of chlorinated volatile organic compound–impacted groundwater that is based upon experience gained during the past 17 years. The projects described in the article generally involve large‐scale enhanced anaerobic dechlorination (EAD) and combined aerobic/anaerobic bioremediation techniques. Our design approach is based on three primary objectives: (1) selecting and distributing the proper additives (including bioaugmentation) within the targeted treatment zone; (2) maintaining a neutral pH (and adding alkalinity when needed); and (3) sustaining the desired conditions for a sufficient period of time for the bioremediation process to be fully completed. This design approach can be applied to both anaerobic and aerobic bioremediation systems. Site‐specific conditions of hydraulic permeability, groundwater velocity, contaminant type and concentrations, and regulatory constraints will dictate the best remedial approach and design parameters for in situ bioremediation at each site. The biggest challenges to implementing anaerobic bioremediation processes are generally the selection and delivery of a suitable electron donor and the proper distribution of the donor throughout the targeted treatment zone. For aerobic bioremediation processes, complete distribution of adequate concentrations of a suitable electron acceptor, typically oxygen or oxygen‐yielding compounds such as hydrogen peroxide, is critical. These design approaches were developed based on understanding the biological processes involved and the mechanics of groundwater flow. They have evolved based on actual applications and results from numerous sites. An EAD treatment system, based on our current design approach, typically uses alcohol as a substrate, employs groundwater recirculation to distribute additives, and has an operational period of two to four years. An aerobic in situ treatment system based on our current design approach typically uses pure oxygen or hydrogen peroxide as an electron acceptor, may involve enhancements to groundwater flow for better distribution, and generally has an operational period of one to four years. These design concepts and specific project examples are presented for 17 sites. © 2012 Wiley Periodicals, Inc.     

Potential and Limitations of Microbial Reductive Dechlorination for Bioremediation Applications

Current knowledge and recent advances in the area of microbial reductive dechlorination of polychlorinated organic compounds are summarized. Factors which may limit the efficacy of the dechlorination process for the in situ bioremediation of contaminated soil and sediment systems are identified. Results of recent studies on the anaerobic biotransformation of soil-sorbed chlorinated ethenes and sediment-sorbed chlorinated benzenes are provided to illustrate how low contaminant bioavailability may control the rate and extent of dechlorination in subsurface systems, especially those with long-term contamination. Use of nonionic, polysorbate surfactants as the sole electron donors of a mixed, methanogenic culture supported the microbial sequential reductive dechlorination of either free or sediment-bound hexachlorobenzene (HCB) to primarily 1,3-dichlorobenzene, but did not enhance the bioavailability of sediment-bound HCB as compared to microcosms, which used glucose. Because current knowledge on the interactions of dechlorinating populations with other microbial populations in the presence of alternative terminal electron acceptors (e.g., nitrate, Fe³⁺ , Mn⁴⁺) is limited, such interactions and their effect on the dechlorination process in subsurface systems need to be further explored to improve our understanding of the reductive dechlorination process in complex environmental systems and lead to the development of more efficient in situ bioremediation technologies and strategies.     

Bacterial Poly(Hydroxyalkanoate) Polymer Production from the Biodiesel Co-product Stream

A co-product stream from soy-based biodiesel production (CSBP) containing glycerol, fatty acid soaps, and residual fatty acid methyl esters (FAME) was utilized as a fermentation feedstock for the bacterial synthesis of poly(3-hydroxybutyrate) (PHB) and medium-chain-length poly(hydroxyalkanoate) (mcl-PHA) polymers. Pseudomonas oleovorans NRRL B-14682 and P. corrugata 388 grew and synthesized PHB and mcl-PHA, respectively, when cultivated in up to 5% (w/v) CSBP. In shake flask culture, P. oleovorans grew to 1.3 ± 0.1 g/L (PHA cellular productivity = 13–27% of the bacterial cell dry weight; CDW) regardless of the initial CSBP concentration, whereas P. corrugata reached maximum cell yields of 2.1 g/L at 1% CSBP, which tapered off to 1.7 g/L as the CSBP media concentration was increased to 5% (maximum PHA cellular productivity = 42% of the CDW at 3% CSBP). While P. oleovorans synthesized PHB from CSBP, P. corrugata produced mcl-PHA consisting primarily of 3-hydroxyoctanoic acid (C_8:0; 39 ± 2 mol%), 3-hydroxydecanoic acid (C_10:0; 26 ± 2 mol%) and 3-hydroxytetradecadienoic acid (C_14:2; 15 ± 1 mol%). The molar mass (M_n) of the PHB polymer decreased by 53% as the initial CSBP culture concentration was increased from 1% to 5% (w/v). In contrast, the M_n of the mcl-PHA polymer produced by P. corrugata remained constant over the range of CSBP concentrations used.     

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.