Removal Of TCE Research Articles

Fabrication and Characterization of Bimetal Sulfide Hybrid Ag/S-ZVI for Dechlorination of Trichloroethylene

Sulfidated and bimetal modification can improve the reactivity and selectivity of zero-valent iron in contaminant removal. However, previous studies were focused on unilateral material approaches. In this article, a new hybrid composite Ag/S-ZVI was prepared by doping elemental silver on surface of sulfidated nanoscale zerovalent iron (S-nZVI). The results of X-Ray Diffraction (XRD), energy dispersive spectrometer (EDS) and X-ray Photoelectron Spectroscopy (XPS) indicated Ag was dispersed on the surface of S-nZVI. Scanning electron microscope (SEM) images displayed Ag/S-ZVI was irregular clusters with rough surfaces, small agglomeration, and quasi-spherical in shape. The removal of TCE by Ag/S-ZVI was 90.4% within 20 min. The reaction rate constant <i>K<sub>obs</sub></i> of Ag/S-ZVI was 2.59 times or 1.85 times of nZVI or S-nZVI, respectively. Cycling experiments showed that Ag/S-ZVI had good recycling ability, and the removal rate of TCE reached 72.6% at the third cycle. The addition of Ag<sup>+</sup> makes S-nZVI as an abundant and efficient source of reducing electrons. The Fe<sup>0</sup> core can break C-Cl bonds by releasing electrons and the surface layer of Ag favors the transfer efficiency of electrons. Such study provides an efficient and robust ternary system for the remediation of TCE in groundwater.

Synthesis of nZVI-Ni@BC composite as a stable catalyst to activate persulfate: Trichloroethylene degradation and insight mechanism

In Fenton-like oxidation processes, the use of biochar (BC) as support material for the nanoscale zero valent iron-nickel (nZVI-Ni) bimetallic particles attained much attention to activate persulfate (PS) for TCE degradation in aqueous medium. In present work, nZVI-Ni@BC particles with nZVI-Ni to BC mass ratio of 1:5 exhibited excellent results (> 99 % ± 0.24) for TCE degradation. The physico-chemical characteristics, surface morphologies, and elemental mapping of the synthesized nZVI-Ni@BC particles investigated through SEM, EDX, TEM, XPS, XRD, BET and FTIR spectroscopy. For the nZVI-Ni@BC-persulfate system, the effects of PS concentration, initial pH, inorganic ions and natural organic matter (NOM) on TCE degradation were evaluated. Batch experiments revealed that complete removal of TCE (> 99 % ± 0.25) was attained at 250 mg L−1 of nZVI-Ni@BC and 4.0 mM PS dosages at pH 3.49 ± 0.55. Scavenging and electron paramagnetic resonance (EPR) verified the dominant role of both SO4ˉ and OH radicals in acidic environment for degradation of TCE. Moreover, high level of carbonate, bicarbonates and NOM inhibited the overall TCE oxidation reaction. In summary, these results suggested that nZVI-NI@BC composite was an alternative, economic and promising catalyst for the activation of PS to degrade chlorinated contaminants in aqueous medium.

Remediation of Trichloroethylene-Contaminated Groundwater by Sulfide-Modified Nanoscale Zero-Valent Iron Supported on Biochar: Investigation of Critical Factors

This study investigated the feasibility and mechanism of sulfide-modified nanoscale zero-valent iron supported on biochar (S-nZVI@BC) for the removal of TCE in the scenario of groundwater remediation. The effects of some critical factors, including pyrolysis temperature of biochar, mass ratio of S-nZVI to BC, initial pH, typical groundwater compositions, co-contaminants, and particle aging time, on the TCE removal were examined. The results revealed that the different pyrolysis temperatures could change physicochemical properties of BC, which influenced the TCE adsorption and degradation by S-nZVI@BC. The mass ratio of S-nZVI to BC could determine the extent of adsorption and degradation of TCE. The total removal of TCE was not significantly influenced by the initial pH (3.0–9.0), but the degradation of TCE was enhanced at higher pH. Notably, the typical anions (SO42−, HCO3−, and HPO42−), humic acid, and co-contaminants (Cr(VI) and NO3−) in groundwater all slightly influenced the total removal of TCE, but markedly inhibited its degradation. Additionally, after exposure to air over different times (5 days, 10 days, 20 days, and 30 days), the reactivity of S-nZVI@BC composites was apparently decreased due to surface passivation. Nevertheless, the aged S-nZVI@BC composites still maintained relative high removal and degradation of TCE when the reaction time prolonged. Overall, the results showed that the S-nZVI@BC, combining the high adsorption capacity of BC and the high reductive capacity of S-nZVI, had a much better performance than the single S-nZVI or BC, suggesting that S-nZVI@BC is one promising material for the remediation of TCE-contaminated groundwater.

Insights into enhanced removal of TCE utilizing sulfide-modified nanoscale zero-valent iron activated persulfate

Sulfide-modified nanoscale zero-valent iron (NZVI-S) has been considered as a promising material for in-situ chemical reduction processes (ISCRPs) for groundwater remediation. However, studies utilizing NZVI-S for in-situ chemical oxidation processes (ISCOPs) were relative rare. In this study, NZVI-S was synthesized and utilized to activate persulfate (PS) for the degradation of TCE. The effects of Fe/S molar ratio, initial pH on TCE removal and dechlorination by NZVI-S activated PS were studied. The results showed that, compared with bare NZVI, NZVI-S showed better properties in activating PS which included better pH adaptiveness, higher TCE removal and mineralization efficiency, and faster removal rate. The Fe/S molar ratio significantly influenced the TCE degradation, and the highest TCE degradation was observed at Fe/S molar ratio of 25–30. The underlying mechanisms of NZVI-S exceling NZVI in activating PS were elucidated through spectroscopic analyses that accounted for the higher iron dissolution rates and iron sulfides (e.g., FeS and FeSx) generated on its surface, which elevated the quantity and accelerated the transfer rate of electrons for activating PS. Besides, hydroxyl radical was observed as a dominant reactive radical in degrading TCE at various pH conditions, but sulfate radical also played an important part especially under acidic condition. Finally, the degradation products of TCE were analyzed and the possible pathways of TCE degradation were illustrated. And the slight influence of natural substances in groundwater on the degradation process suggests NZVI-S activated PS would be a promising approach for groundwater remediation.

Nickel loaded zeolites FAU and MFI: Characterization and activity in water-phase hydrodehalogenation of TCE

This work was aimed to investigate the catalytic properties of nickel loaded zeolites Y and ZSM-5 as the catalysts in hydrodechlorination of trichloroethylene (TCE HDC) in the aqueous phase. Both acidic forms of the zeolites and Ni loaded zeolites were thoroughly characterized with respect to their structural (XRD), textural (low-temperature nitrogen sorption, STEM) and acidic/redox properties (IR, XPS, EPR spectroscopies). The studies showed the significant impact of acidic properties of the zeolitic support used as well as the framework geometry and the pore distribution within zeolite grains on the catalytic behaviour of zeolitic materials in the removal of TCE. IR studies of hydrodechlorination of trichloroethylene clearly showed the concurrent participation of both nickel and acid active sites in TCE HDC reaction. The activity of the Ni loaded catalysts increased when reducing the number of acid sites in zeolite catalysts, the centres responsible for carbonaceous deposits formation and finally leading to the catalysts deactivation. Nickel in the form of small (∼ 1–8 nm) and uniformly dispersed nanoparticles was found to be very active in the purification of water from TCE in batch conditions.

Development of hybrid processes for the removal of volatile organic compounds, plasticizer, and pharmaceutically active compound using sewage sludge, waste scrap tires, and wood chips as sorbents and microbial immobilization matrices.

This study evaluated the reutilization of waste materials (scrap tires, sewage sludge, and wood chips) to remove volatile organic compounds (VOCs) benzene/toluene/ethylbenzene/xylenes/trichloroethylene/cis-1,2-dichloroethylene (BTEX/TCE/cis-DCE), plasticizer di(2-ethylhexyl) phthalate (DEHP), and pharmaceutically active compound carbamazepine from artificially contaminated water. Different hybrid removal processes were developed: (1) 300mg/L BTEX + 20mg/L TCE + 10mg/L cis-DCE + tires + Pseudomonas sp.; (2) 250mg/L toluene + sewage sludge biochar + Pseudomonas sp.; (3) 100mg/L DEHP + tires + Acinetobacter sp.; and (4) 20mg/L carbamazepine + wood chips + Phanerochaete chrysosporium. For the hybrid process (1), the removal of xylenes, TCE, and cis-DCE was enhanced, resulted from the contribution of both physical adsorption and biological immobilization removal. The hybrid process (2) was also superior for the removal of DEHP and required a shorter time (2days) for the bioremoval. For the process (3), the biochar promoted the microbial immobilization on its surface and substantially enhanced/speed up the bioremoval of toluene. The fungal immobilization on wood chips in the hybrid process (4) also improved the carbamazepine removal considerably (removal efficiencies of 61.3 ± 0.6%) compared to the suspended system without wood chips (removal efficiencies of 34.4 ± 1.8%). These hybrid processes would not only be promising for the bioremediation of environmentally concerned contaminants but also reutilize waste materials as sorbents without any further treatment.

Enhancing bioregeneration of TCE-sorbed Biological Powdered Activated Carbon by dosing toluene as primary substrate and competitive adsorbate

Removal of TCE by Biological Powdered Activated Carbon (BPAC), inoculated with Burkholderia vietnamiensis G4 and fed with toluene as the growth substrate, was investigated in fed-batch mode reactors, focusing on the regeneration of Powdered Activated Carbon (PAC). Cell-only and PAC-only reactors were operated in parallel for comparison. BPAC, once acclimated, removed toluene and TCE faster than cell-only or PAC-only reactors, leaving the lowest residuals in the liquid. This was amplified when the substrate dose was elevated. Toluene competitively adsorbed into the BPAC, resulting in TCE desorption, which accelerated bioregeneration of the TCE-sorbed BPAC. The regenerated BPAC exerted a similar adsorption capacity to PAC and a similar biodegradation capability to virgin BPAC under the experimental conditions. An acclimation of cells on TCE was necessary before its degradation, which indicated that TCE cometabolism may not be a fortuitous reaction. When a bioactive zone is constructed with BPAC, it is expected that TCE in the groundwater will be adsorbed to the BPAC; then, the adsorbed TCE will be desorbed and cometabolized upon pulse injections of toluene. A portion of left-over toluene will be stored in the BPAC and utilized for later TCE cometabolization.

Degradation of TCE by TEOS Coated nZVI in the Presence of Cu(II) for Groundwater Remediation

The removal of TCE by nanofer zero valent iron (nanofer ZVI) coated with tetraethyl orthosilicate (TEOS) in the presence of Cu(II) at different environmental conditions was studied. The kinetics of TCE degradation by nanofer ZVI was determined. At a dosage of 10 mg of nanofer ZVI, almost 63% of TCE was removed, when Cu(II) and TCE were present. It contrasts with 42% degradation of TCE in the absence of Cu(II). SEM/EDS images indicated that Cu(II) is reduced to form Cu0 and Cu2O. These formations are considered to be responsible for enhancing TCE degradation. Direct reduction involves hydrogenolysis and β‐elimination in the transformation of TCE, while indirect reduction involves atomic hydrogen and no direct electron transfer from the metal to reactants. The reduction of activation energy was also noted indicating that the rate limiting step for TCE degradation in the presence of Cu(II) is surface chemical reaction rather than diffusion. Most of iron present in nanofer ZVI get dissolved causing the generation of localized positive charge regions and form metal chlorides. Local accumulation of hydrochloric acid inside the pits regenerates new reactive surfaces to serve as sources of continuous electron generation. No significant effect of TCE was noticed for Cu(II) sequestration.

Coupling of zero valent iron and biobarriers for remediation of trichloroethylene in groundwater

This study attempted to construct a three series barrier system to treat high concentrations of trichloroethylene (TCE; 500 mg/L) in synthetic groundwater. The system consisted of three reactive barriers using iron fillings as an iron-based barrier in the first column, sugarcane bagasse mixed with anaerobic sludge as an anaerobic barrier in the second column, and a biofilm coated on oxygen carbon inducer releasing material as an aerobic barrier in the third column. In order to evaluate the extent of removal of TCE and its metabolites in the aquifer down gradient of the barrier system, a fourth column filled with sand was applied. Residence time of the system was investigated by a bromide tracer test. The results showed that residence time in the column system of the control set and experimental set were 23.62 and 29.99 days, respectively. The efficiency of the three series barrier system in removing TCE was approximately 84% in which the removal efficiency of TCE by the iron filling barrier, anaerobic barrier and aerobic barrier were 42%, 16% and 25%, respectively. cis-Dichloroethylene ( cis-DCE), vinyl chloride (VC), ethylene and chloride ions were observed as metabolites following TCE degradation. The presence of chloride ions in the effluent from the column system indicated the degradation of TCE. However, cis-DCE and VC were not fully degraded by the proposed barrier system which suggested that another remediation technology after the barrier treatment such as air sparging and adsorption by activated carbon should be conducted.

Complete Removal of Chloro-Based Volatile Organic Compounds by Thermally Activated Oxide Semiconductors

Chloro-based volatile organic compounds (VOCs) are known to exert noxious effects on the environment, and their destruction by catalytic combustion, for example, accompanies a production of hydrochloric acid (HCl) that damages the catalyst. We have been interested in complete removal of VOCs by our system based on thermally activated oxide semiconductors (i.e., catalysts) such as Cr2O3, TiO2, NiO, � -Fe2O3. In the present investigation, we have fundamentally studied the decomposition process of dichloromethane (CH2Cl2: DCM) and trichloroethylene (CHCCl3; TCE) on the basis of the mass- and Raman spectra in an attempt to identify the formation temperature of HCl. Then, we found that the decomposition of DCM and TCE starts at about 100 and 200 � C, respectively; whereas HCl is abruptly formed at a critical temperature of about 350 � C in both compounds. Based on this result, we have optimized the operation temperature below 300 � C for Cr2O3-impregnated honeycomb systems and achieved the complete removal of DCM and TCE that accompanies no formation of HCl. [doi:10.2320/matertrans.M2011028]

Experimental investigation of pneumatic soil vapor extraction

Soil Vapor Extraction (SVE) is a common remediation technique for removing volatile organic compounds from unsaturated contaminated soils. Soil heterogeneities can however cause serious limitations to the applicability of SVE due to air bypassing low permeable areas of the soil, leading to diffusion limitation of the remediation. To enhance removal from areas subject to diffusion limitation a new remediation technique, pneumatic soil vapor extraction, is proposed. In contrast to traditional SVE, in which soil vapor is extracted continuously by a vacuum pump, pneumatic SVE is based on enforcing a sequence of large pressure drops on the system to enhance the recovery from the low-permeable areas. The pneumatic SVE technique was investigated in the laboratory using TCE as a model contaminant. 2D-laboratory tank experiments were performed on homogeneous and heterogeneous sand packs. The heterogeneous packs consisted of a fine sand lens surrounded by a coarser sand matrix. As expected when using traditional SVE, the removal of TCE from the low permeable lens was extremely slow and subject to diffusion limitation. In contrast when pneumatic venting was used removal rates increased by up to 77%. The enhanced removal was hypothesized to be attributed to mixing of the contaminated air inside the lens and generation of net advective transport out of the lens due to air expansion.

Pilot studies for in-situ aerobic cometabolism of trichloroethylene using toluene-vapor as the primary substrate

In-situ pilot studies of aerobic cometabolism were conducted to evaluate the injection of toluene-vapor and air into TCE-contaminated aquifer. Delivery of primary substrate (toluene) in a vapor state with air enhanced the growth of indigenous toluene-utilizing bacteria that would degrade TCE by aerobic cometabolism. Meanwhile, delivering toluene in a vapor state effectively reduced potential clogging near the injection points due to excessive microbial growth, which was observed in the field when the injection of neat toluene was employed. Over 90% removal of TCE was achieved with primary substrate (toluene) degraded to a concentration below 10 microg/L.

Removal of trichloroethylene and trichloroethane using a novel hollow-fibre gas-permeable membrane

In order to evaluate effects of operational parameters on the removal efficiency of trichloroethylene and 1,1,1-trichloroethene from water, lab-scale experiments were conducted using a novel hollow-fibre gaspermeable membrane system, which has a very thin gas-permeable membrane held between microporous support membranes. The permeation rate of chlorinated hydrocarbons increased at higher temperature and water flow rate. On the other hand, the effects of the operational conditions in the permeate side were complex. When the permeate side was kept at low pressure without sweeping air (pervaporation), the removal efficiency of chlorinated hydrocarbon, as well as water permeation rate, was low probably due to lower level of membrane swelling on the permeate side. But when a very small amount of air was swept on the membrane (air perstripping) under a low pressure, it showed a higher efficiency than in any other conditions. Three factors affecting the permeation rate are: 1) reduction of diffusional boundary layer within the microporous support membrane, 2) air/vapour flow regime and short cutting, and 3) the extent of membrane swelling on the permeate side. A higher air flow, in general, reduces the diffusional boundary layer, but at the same time disrupts the flow regime, causes short cutting, and makes the membrane dryer. Due to these multiple effects on gas permeation, there is an optimum operational condition concerning the vacuum pressure and the air flow rate. Under the optimum operational condition, the residence time within the hollow-fibre membrane to achieve 99% removal of TCE was 5.25 minutes. The log (removal rate) was linearly correlated with the average hydraulic residence time within the membrane, and 1 mg/L of TCE can be reduced to 1 μg/L (99.9% removal).

Kinetic modeling and simulation of PCE and TCE removal in aqueous solutions by electron-beam irradiation

The irradiation of aqueous solutions of TCE and PCE using a high-energy electron-beam results in the rapid decomposition of both chemicals. It is known that both TCE and PCE react with the aqueous electron and the hydroxyl radical with bimolecular rate constants greater than 10 9 M −1 s −1 for each reaction. The fact that high-energy electrons produce significant concentrations of both e aq − and OH radicals in water makes it an effective process for the removal of TCE and PCE from aqueous solution. We have employed steady state and computer-based chemical kinetic models to simulate and better understand the chemistry and kinetics of e-beam irradiation when applied to natural water systems. Model results were benchmarked to experimental data, allowing for the optimization of the reaction of DOC with the OH radical. Values for the associated second-order reaction rate constant were found to be 2.5×10 8 and 4.0×10 8 M −1 s −1, consistent with reported values for k OH,DOC. The models were also used to investigate the possibility of incomplete irradiation during treatment and the presence of proposed chemical reactions of by-products. The reactions involve radicals and radical-adduct species formed by the reaction of TCE and PCE with the hydroxyl radical.

Adsorption/Reduction Reactions of Trichloroethylene by Elemental Iron in the Gas Phase: The Role of Water

The interactions of TCE with “clean” and “partially oxidized” Fe0 were investigated in the gas phase. The removal of TCE from the gas phase proceeded by adsorption onto the Fe0 surface or by dechlorination reactions with Fe0 depending on the moisture content of the reaction medium. Unlike the aqueous phase, water was a critical variable competing with TCE for adsorption sites and, above a critical limit, serving as a proton donor for the hydrogenolysis of TCE. The adsorption of water (relative humidity, RH = 6−97%) was fit to a multilayer BET isotherm. The extent of water adsorption was nearly identical for both forms of Fe0 on a surface area basis, i.e., mol/m2. The adsorption of TCE decreased by more than 1 order of magnitude from 6% to 10% RH, after which a more stable region (<50% decrease between 20% and 97% RH) appeared above monolayer water coverage (∼26% RH). The removal of TCE from the gas phase was strictly by adsorption up to a “critical” RH, i.e., 72% for acid-washed and 92% for the partially oxidized surfaces, above which dechlorination occurred and the hydrogenolysis byproducts appeared.

Effect of Nonionic Surfactant on the Removal of TCE and PCE

Effect of Nonionic Surfactant on the Removal of TCE and PCE

The comparison of trichloroethylene removal rates by methane- and aromatic-utilizing microorganisms

The comparison of TCE cometabolic removal by methane, toluene, and phenol utilizers was conducted with a series of batch reactors. Methane, toluene, or phenol enriched microorganisms were used as cell source. The initial cell concentration was about 107 cfu/mL. Methane, toluene, and phenol could be readily biodegraded resulting in the cometabolic removal of TCE. Among the three primary carbon sources studied, the presence of phenol provided the best cometabolic removal of TCE. When the concentration of carbon source was 3 mg-C/L, the initial TCE removal rates initiated by methane, toluene, and phenol utilizers were 1.5, 30, and 100 μg/L-hr, respectively. During the incubation period of 80 hours, TCE removal efficiencies were 26% and 96% with the presence of methane and toluene, respectively. However, it was 100% within 20 hours with the presence of phenol. For phenol utilizers, the initial TCE removal rates were about the same, when the phenol concentrations were 1.35, 2.7, and 4.5 mg/L. However, TCE removal was not proportional to the concentrations of phenol. TCE removal was hindered when the phenol concentration was higher than 4.5 mg/L because of the rapid depletion of dissolved oxygen. The presence of toluene also initiated cometabolic removal of TCE. The presence of toluene at 3 and 5 mg/L resulted in similar TCE removal. The initial TCE removal rate was about 95 μg/L-hr at toluene concentrations of 3 and 5 mg/L compared to 20 μg/L-hr at toluene concentration of 1 mg/L.

The comparison of trichloroethylene removal rates by methane- and aromatic-utilizing microorganisms

The comparison of TCE cometabolic removal by methane, toluene, and phenol utilizers was conducted with a series of batch reactors. Methane, toluene, or phenol enriched microorganisms were used as cell source. The initial cell concentration was about 107 cfu/mL. Methane, toluene, and phenol could be readily biodegraded resulting in the cometabolic removal of TCE. Among the three primary carbon sources studied, the presence of phenol provided the best cometabolic removal of TCE. When the concentration of carbon source was 3 mg-C/L, the initial TCE removal rates initiated by methane, toluene, and phenol utilizers were 1.5, 30, and 100 µg/L-hr, respectively. During the incubation period of 80 hours, TCE removal efficiencies were 26% and 96% with the presence of methane and toluene, respectively. However, it was 100% within 20 hours with the presence of phenol. For phenol utilizers, the initial TCE removal rates were about the same, when the phenol concentrations were 1.35, 2.7, and 4.5 mg/L. However, TCE removal was not proportional to the concentrations of phenol. TCE removal was hindered when the phenol concentration was higher than 4.5 mg/L because of the rapid depletion of dissolved oxygen. The presence of toluene also initiated cometabolic removal of TCE. The presence of toluene at 3 and 5 mg/L resulted in similar TCE removal. The initial TCE removal rate was about 95µg/L-hr at toluene concentrations of 3 and 5 mg/L compared to 20 µg/L-hr at toluene concentration of 1 mg/L.

Cometabolism in biofilm reactors

Aerobic cometabolism of chlorinated aliphatic solvents in biofilm reactors is a potential treatment technology for contaminated water and air streams. This research investigated cometabolism by pure and mixed cultures of methanotrophs and mixed cultures of phenol-degrading bacteria. Initial experiments with continuous-flow, packed-bed bioreactors proved unsuccessful; therefore, the major focus of the work was on sequencing biofilm reactors, which cycle between two modes of operation, degradation of chlorinated solvents and rejuvenation of the microbial population. Particular success was obtained with a mixed culture of phenol degraders in the treatment of chlorinated ethenes (e.g., trichloroethylene - TCE). Under the best operating conditions, 90% removal of TCE occurred at a 14-minute packed-bed hydraulic residence time. The bioreactors required only two, 1.5 h biomass rejuvenation periods per day to sustain this removal. Experiments with Methylosinus trichosporium OB3b were less successful because of the organism's slow growth rate, relatively poor ability to attach to surfaces, and its inability to successfully compete with other methanotrophs in the bioreactor environment Overall, however, the research demonstrated the potential attractiveness of sequencing biofilm reactors in treating water contaminated with chlorinated solvents.

Cometabolism in biofilm reactors

Aerobic cometabolism of chlorinated aliphatic solvents in biofilm reactors is a potential treatment technology for contaminated water and air streams. This research investigated cometabolism by pure and mixed cultures of methanotrophs and mixed cultures of phenol-degrading bacteria. Initial experiments with continuous-flow, packed-bed bioreactors proved unsuccessful; therefore, the major focus of the work was on sequencing biofilm reactors, which cycle between two modes of operation, degradation of chlorinated solvents and rejuvenation of the microbial population. Particular success was obtained with a mixed culture of phenol degraders in the treatment of chlorinated ethenes (e.g., trichloroethylene - TCE). Under the best operating conditions, 90% removal of TCE occurred at a 14-minute packed-bed hydraulic residence time. The bioreactors required only two, 1.5 h biomass rejuvenation periods per day to sustain this removal. Experiments with Methylosinus trichosporium OB3b were less successful because of the organism's slow growth rate, relatively poor ability to attach to surfaces, and its inability to successfully compete with other methanotrophs in the bioreactor environment. Overall, however, the research demonstrated the potential attractiveness of sequencing biofilm reactors in treating water contaminated with chlorinated solvents.