Methyl Tert-butyl Ether Concentrations Research Articles

The toxicity effects of the individual and combined exposure of methyl tert-butyl ether (MTBE) and tire rubber powder (RP) on Nile tilapia fish (Oreochromis niloticus)

Methyl tert-butyl ether (MTBE) is soluble in water and can contaminate water sources when it spills during transportation or leaks from underground storage tanks. Incomplete combustion releases MTBE as exhaust fumes that can be deposited on urban surfaces. Meanwhile, car tires erosion emits of large amounts of rubber dust (RP), easily transported to water bodies. Therefore, this study has the objective of assessing the toxicity of varying concentrations of MTBE (0, 2.5, 5.0 μL L−1) and RP (0, 5.0, 10.0 mg L−1 RP), both individually and in combination, over a period of 28 days on Nile tilapia (Oreochromis niloticus). MTBE and PR decreased fish growth performance. Blood biochemical analytes indicated that MTBE and RP led to increasing Aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and creatinine phosphokinase (CPK), alkaline phosphatase and gamma-glutamyl transferase (GGT) activities. Alterations related to glucose, triglycerides, cholesterol, and creatinine, plasma contents, were also observed. Increased antioxidant biomarkers, including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), glutathione reductase (GR), and malondialdehyde (MDA), was observed. Exposure fish to MTBE and PR changed metabolic profile of muscle tissue. Moreover, results showed that MTBE, its metabolites, and PR could accumulate in the muscle tissue of fish. Results suggest that MTBE and RP can impact fish health, both individually and when combined. The presence of MTBE enhances the toxicity of RP, indicating a synergistic effect. Nevertheless, further studies are needed to understand the impact of toxic compounds on aquatic environments and organisms' health.

A Survey of Gasoline Ameliorator, Methyl-Tert-Butyl Ether (MTBE) on Bovine Serum Albumin: A Spectroscopy and Molecular Dynamic Simulation Study.

Methyl-Tert-Butyl Ether (MTBE) as a gasoline modifier is frequently added to fuels and used in plenty of worldwide applications. MTBE biodegradation in groundwater occurs slowly and produces water miscibility; therefore, it causes diverse environmental and human health concerns. The interaction of MTBE with bovine serum albumin (BSA) as a model protein at physiological conditions is investigated to illustrate the possible interactions of MTBE with the body's proteins. Uv-visible, fluorescence, circular dichroism (CD) spectroscopy methods, and molecular modeling were used to analyze the MTBE's effect on BSA structure and dynamics. The constant protein concentration and various MTBE contents were used for possible interactions. The protein structural analysis shows that MTBE binds to BSA via positive enthalpy and entropy via hydrophobic interactions. Molecular docking shows the participation of several amino acids in the MTBE-BSA interaction. The CD spectroscopy results show that the BSA structure was not changed in the MTBE concentrations utilized in the study. Molecular dynamics (MD) simulation results suggest that MTBE can slightly change protein structure in the last 50ns. Comparing experimental and MD simulation results demonstrated that the BSA secondary structure was maintained in the low concentration of the MTBE. The entropy and enthalpy parameters asserted the hydrophobic interaction was the major force in the interaction between the BSA and MTBE.

Photocatalytic Removal of Methyl Tert-Butyl Ether by C-N-TiO2 Nanoparticles from Aqueous Solution

BackgroundThe elimination of methyl tert-butyl ether (MTBE) from water resources remains a main environmental concern. In the present study, photo-assissted process for removal of MTBE was examined in the solutions containing C-N-TiO2 nanoparticles under UV irradiation in the batch mode.MethodsThe effects of operational factors such as pH, initial catalyst concentration, and initial MTBE concentration on MTBE removal was investigated.ResultsThe optimum degradation condition for MTBE was obtained at pH 7, catalyst load of 100 mg/L, air flow rate = 0.1 L/min and C0 = 5 mg/L with 73 percent degradation of MTBE at 60 min. In addition, Analytical profiles on MTBE removal were based on the first-order kinetics model. However, the removal rate decreased by increasing initial concentration of MTBE.ConclusionThe findings showed that UV/C-N-TiO2 system is an efficient method for MTBE degradation from aqueous solution.

Treatment of petroleum hydrocarbon-polluted groundwater with innovative in situ sulfate-releasing biobarrier

Petroleum hydrocarbons are commonly found pollutants in groundwater at industrial and gas station sites. Enhanced bioremediation is a cost-effective approach to cleanup petroleum hydrocarbon-polluted groundwater. The applicability of using sulfate-reducing biobarrier on the containment and control of petroleum-hydrocarbon plumes were assessed by batch and column studies. The innovative in situ biobarrier contained sulfate-releasing materials (SRMs) for a long-term sulfate release to enhance anaerobic petroleum hydrocarbons biodegradation with sulfate reduction mechanisms. SRMs were developed by blending rice husk powder (or starch) (used as permeability increment materials), magnesium sulfate (used as a source of sulfate), and polylactic acid (PLA) (used as a binder) together using a kneader. The mixed components were smelted to form pasty liquid at 190 °C, and it was transferred to a cylinder container to form SRMs. A column study was used to investigate the effectiveness of developed SRMs on the treatment of a methyl tert-butyl ether (MTBE) and toluene contaminated groundwater. The optimal sulfate release rate was achieved when the mass ratio of sulfate/starch/PLA was 0.5/0.5/2 [sulfate release rate (mg.d−1.g−1) = −0.009 × release period (d) + 3.4 (mg). Approximately 70% of MTBE and 92% of toluene could be remediated via sulfate reduction processes because the released sulfate from SRMs were served as electron acceptors, which promoted the growth of sulfate reducers. The next generation sequencing data suggest that bacterial strains with sulfate reduction and petroleum hydrocarbon biodegradation functions were detected after SRM supplement. Evidences of sulfate reduction of toluene and MTBE included (1) increased concentrations of sulfate and sulfide, (2) decreased concentrations of toluene and MTBE, (3) production of tert-butyl alcohol (degradation byproduct of MTBE), and (4) increased sulfate-reducing and petroleum-hydrocarbon bacteria. The biobarrier system containing the SRMs can be developed into a pragmatic technology for in situ remediation of petroleum-hydrocarbon plumes.

Kinetic modeling of Methyl Tert-Butyl Ether (MTBE) removal by bacterial isolated from contaminated soils

ABSTRACT Methyl Tert-Butyl Ether(MTBE) is among oxygenised additives to gasoline, which has high solubility and leads to pollution of water resources. So far, the microbial species affecting the of high MTBEconcentrationsremoval have been less investigated. This study aimed to remove high concentrations of MTBEusing isolated bacteriafrom contaminatedsoil with petroleum compounds in southern regions of Iran and determine their kinetics. After isolating the bacteria and determining their growth in different concentrations, the effects of the following parameters on the removal percentage were examined: incubation time = 1–7 days, pH = 5.0–7.0, and 9.0, initial MTBE concentration = 1000–5000 mg/L, and C: N:P. Then, the four strains with high efficiency were selected, and their kinetic were analysed by zero-order, first-order, and second-order models. The results showed that the highest growth in MTBE concentration (50,000 mg/L) was observed for Acinetobacter sp, Bacillus sp, Ochrobactrum sp, and Sphingomonas sp. after four days. Then, Ochrobactrum sp.was used as a pure strain as well as a microbial consortium for the next steps, including the effects of nutrient ratio and initial MTBE concentration. In this study, the optimal conditions for incubation time and the initial MTBE concentration were 72 hours and 5000 mg/L, respectively. The kinetic modeling indicated that the second-order model (R2 = 0.95, Root Mean Squared Error = 0.012) and the Micheal-Menten model (R2 = 0.99) were the best modelfor MTBE biodegradation. Overall, the results indicated that pure Ochrobactrum sp. and a microbial consortium consisting of resistant bacteria at high MTBEconcentrations could remove MTBE> 90%.

Mesoporous Silica Membranes Silylated by Fluorinated and Non-Fluorinated Alkylsilanes for the Separation of Methyl Tert-Butyl Ether from Water.

It is of great significance to separate hazardous methyl tert-butyl ether (MTBE) from water in terms of environmental protection and human health. In the present work, α-Al2O3-suppotred silica membranes were prepared by the sol-gel and dip-coating technique. Two fluorinated alkylsilanes (1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) and trifluoropropyltriethoxysilane (TFPTES)) and two non-fluorinated alkylsilanes (octyltriethoxysilane (OTES) and propyltriethoxysilane (PTES)) were adopted to silylate the silica membrane by the post-grafting method which is used for the separation of MTBE from water by pervaporation. The results show that silylation enhances the hydrophobicity of silica membranes. The silylated silica membranes are selective towards MTBE, and the MTBE/water separation factor varies with grafting agents in the order: PFOTES > TFPTES > OTES > PTES. Membranes silylated with fluorinated carbon chains seem to be more selective towards MTBE than those with non-fluorinated carbon chains. The total flux is proportional to the pore volume of silica membranes, which depends on grafting agents in the order: PTES > PFOTES > OTES > TFPTES. Considering both total flux and selectivity, the PFOTES-SiO2 membrane is most effective in separation, with a MTBE/water separation factor of 24.6 and a total flux of 0.35 kg m−2 h−1 under a MTBE concentration of 3.0% and a feed temperature of 30 °C.

Photocatalytic Oxidation of Methyl Tert-Butyl Ether in Presence of Various Phase Compositions of TiO2

MTBE (methyl tert-butyl ether) represents a rising threat to the environment, especially drinking water, and its effective removal (with all by-products) is necessary. Even a very low concentration of MTBE makes the water undrinkable; therefore, an effective treatment has to be developed. This work is focused on MTBE photocatalytic oxidation in presence of various TiO2 photocatalysts with different phase composition prepared by different methods. It was confirmed the phase composition of TiO2 had the most significant influence on the photocatalytic degradation of MTBE. The rutile phase more easily reduces adsorbed oxygen by photogenerated electrons to superoxide radical, supporting separation of charge carriers. The presence and concentrations of by-products have to be taken into account as well. The conversion of total organic carbon (TOC) was used for the comparison, 40% of TOC was removed after 1 h of irradiation in presence of TiO2–ISOP–C/800 photocatalyst composed of anatase and rutile phase.

The in situ treatment of BTEX, MTBE, and TBA in saline groundwater

AbstractA pilot‐scale test was conducted in a saline aquifer to determine if a petroleum hydrocarbon (PHC) plume containing benzene (B), toluene (T), ethylbenzene (E), xylenes (X), methyl tert‐butyl ether (MTBE), and tert‐butyl alcohol (TBA) could be treated effectively using a sequential treatment approach that employed in situ chemical oxidation (ISCO) and enhanced bioremediation (EBR). Chemical oxidants, such as persulfate, have been shown to be effective in reducing dissolved concentrations of BTEX (B + T + E + X) and additives such as MTBE and TBA in a variety of geochemical environments including saline aquifers. However, the lifespan of the oxidants in saline environments tends to be short‐lived (i.e., hours to days) with their effectiveness being limited by poor delivery, inefficient consumption by nontargeted species, and back‐diffusion processes. Similarly, the addition of electron acceptors has also been shown to be effective at reducing BTEX and associated additives in saline groundwater through EBR, however EBR can be limited by various factors similar to ISCO. To minimize the limitations of both approaches, a pilot test was carried out in a saline unconfined PHC‐impacted aquifer to evaluate the performance of an engineered, combined remedy that employed both approaches in a sequence. The PHC plume had total BTEX, MTBE, and TBA concentrations of up to 4,584; 55,182; and 1,880 μg/L, respectively. The pilot test involved injecting 13,826 L of unactivated persulfate solution (19.4 weight percent (wt.%) sodium persulfate (Na2S2O8) solution into a series of injection wells installed within the PHC plume. Parameters monitored over a 700‐day period included BTEX, MTBE, TBA, sulfate, and sulfate isotope concentrations in the groundwater, and carbon and hydrogen isotopes in benzene and MTBE in the groundwater. The pilot test data indicated that the BTEX, MTBE, and TBA within the PHC plume were treated over time by both chemical oxidation and sulfate reduction. The injection of the unactivated persulfate resulted in short‐term decreases in the concentrations of the BTEX compounds, MTBE, and TBA. The mean total BTEX concentration from the three monitoring wells within the pilot‐test area decreased by up to 91%, whereas MTBE and TBA mean concentrations decreased by up to 39 and 58%, respectively, over the first 50 days postinjection in which detectable concentrations of persulfate remained in groundwater. Concentrations of the BTEX compounds, MTBE, and TBA rebounded at the Day 61 marker, which corresponded to no persulfate being detected in the groundwater. Subsequent monitoring of the groundwater revealed that the concentrations of BTEX continued to decrease with time suggesting that EBR was occurring within the plume. Between Days 51 and 487, BTEX concentrations decreased an additional 84% from the concentration measured on Day 61. Mean concentrations of MTBE showed a reduction during the EBR phase of remediation of 33% while the TBA concentration appeared to decrease initially but then increased as the sulfate concentration decreased as a result of MTBE degradation. Isotope analyses of dissolved sulfate (34S and 18O), and compound‐specific isotope analysis (CSIA) of benzene and MTBE (13C and 2H) supported the conclusions that ISCO and EBR processes were occurring at different stages and locations within the plume over time.

Use of omic tools to assess methyl tert-butyl ether (MTBE) degradation in groundwater.

This study employed innovative technologies to evaluate multiple lines of evidence for natural attenuation (NA) of methyl tertiary-butyl ether (MTBE) in groundwater at the 22 Area of Marine Corps Base (MCB) Camp Pendleton after decommissioning of a biobarrier system. For comparison, data from the 13 Area Gas Station where active treatment of MTBE is occurring was used to evaluate the effectiveness of omic techniques in assessing biodegradation. Overall, the 22 Area Gas Station appeared to be anoxic. MTBE was detected in large portion of the plume. In comparison, concentrations of MTBE at the 13 Area Gas Station were much higher (42,000 μg/L to 2800 μg/L); however, none of the oxygenates were detected. Metagenomic analysis of the indigenous groundwater microbial community revealed the presence of bacterial strains known to aerobically and anaerobically degrade MTBE at both sites. While proteomic analysis at the 22 Area Gas Station showed the presence of proteins of MTBE degrading microorganisms, the MTBE degradative proteins were only found at the 13 Area Gas Station. Taken together, these results provide evidence for previous NA of MTBE in the groundwater at 22 Area Gas Station and demonstrate the effectiveness of innovative-omic technologies to assist monitored NA assessments.

Modeling the efficiency of TiO2 photocatalytic degradation of MTBE in contaminated water: a support vector regression approach

Methyl tert-Butyl Ether (MTBE) is one of the common environmental contaminants that pose severe risks to human health and the environment. Due to the detrimental effects of MTBE, many efforts have been devoted towards decontamination of wastewater containing MTBE. Most of the reports on the treatment of MTBE are experimental based, which requires studying the effect of several factors such as dosage of the photocatalyst, pH of the medium, the initial concentration of contaminant and the contact time on degradation efficiency in MTBE contaminated waters. Although, this approach is highly dependable and often leads to new insights. However, because the degradation efficiency is influenced by multiple factors, performing experiments to investigate the effect of these factors often increases the experimental burden, thus requiring more time and materials consumption to achieve desirable results. Herein, we propose a computational intelligent strategy to mitigate these challenges. In this contribution, the degradation efficiencies of MTBE in the presence of TiO2/UV were modeled under various experimental conditions using the support vector regression model. The model was built using experimental data comprising of inputs such as TiO2 dose, initial MTBE concentration, UV wavelength and contact time. Remarkably, the developed model exhibits significant accuracy as determined from the values of correlation coefficient (98.27%) and root means square error (5.53). In addition, it was determined that the achievable optimum conditions for degradation of 0.5–100 ppm MTBE-contaminated water were 2.4 g/L of TiO2 dose with UV radiation, a solution pH of 3 and treatment time of 2 h. This study will be useful in the experimental design of treatment for MTBE, consequently reducing the time spent on running experiments and at the same time ensuring efficient use of resources for treatment of MTBE contaminated water.

Effect of Methyl Tert-Butyl Ether (MTBE) at in vitro conditions on antioxidant enzyme activities of superoxide dismutase and catalase in Rutilus caspicus (Yakovlev, 1870)

Methyl Tert-Butyl Ether(MTBE) increases oxygen consumption and reduces carbon monoxide and also air pollution. It is very active in soil, and its motility in water is a function of water movement in soil. MTBE is resistant to biodegradation, with high half-life and solubility in water and weak absorption in soil particles. The activities of SOD and CAT enzymes were examined in Rutilus caspicus in concentrations of 50, 100 and 150 mg L-1 MTBE for 7, 14 and 21 days. The mean water temperature and oxygen were 191°C and 7.60.2 respectively and salinity was maintained zero. 156 R. caspicus were stocked in aquariums, 3 specimens were randomly selected from aquarium in the first, second and third weeks. Blood serum was separated to assay the SOD and CAT activities. A strong significant positive relationship was found between MTBE concentration and SOD as well as CAT: [r(108)=0.73, P < 0.01]. Elevated MTBE increased the activity of SOD and CAT. In addition, there was a mean significant positive relationship between exposure time and SOD: [r(108)=0.41, P < 0.01]. SOD activity increased over time, and there was a negative weak significant relationship between exposure time and CAT [r(108)=-0.20, P < 0.05]. CAT activity decreased by prolonged exposure time. Moreover, there was a mean positive significant relationship between SOD and CAT [r(108)=0.41, P < 0.01].

Adsorption of methyl tert-butyl ether (MTBE) onto ZSM-5 zeolite: Fixed-bed column tests, breakthrough curve modelling and regeneration

ZSM-5, as a hydrophobic zeolite, has a good adsorption capacity for methyl tert-butyl ether (MTBE) in batch adsorption studies. This study explores the applicability of ZSM-5 as a reactive material in permeable reactive barriers (PRBs) to decontaminate the MTBE-containing groundwater. A series of laboratory scale fixed-bed column tests were carried out to determine the breakthrough curves and evaluate the adsorption performance of ZSM-5 towards MTBE under different operational conditions, including bed length, flow rate, initial MTBE concentration and ZSM-5 dosage, and regeneration tests were carried out at 80, 150 and 300 °C for 24 h. Dose-Response model was found to best describe the breakthrough curves. MTBE was effectively removed by the fixed-bed column packed with a ZSM-5/sand mixture with an adsorption capacity of 31.85 mg g−1 at 6 cm bed length, 1 mL min−1 flow rate, 300 mg L−1 initial MTBE concentration and 5% ZSM-5 dosage. The maximum adsorption capacity increased with the increase of bed length and the decrease of flow rate and MTBE concentration. The estimated kinetic parameters can be used to predict the dynamic behaviour of column systems. In addition, regeneration study shows that the adsorption capacity of ZSM-5 remains satisfactory (>85%) after up to four regeneration cycles.

Stabilized hydrogen peroxide for the remediation of hydrocarbons and MTBE in high temperature and saline groundwater

AbstractA field pilot‐scale test was conducted to determine if the use of citric acid‐stabilized hydrogen peroxide (H2O2) is effective in reducing dissolved concentrations of petroleum hydrocarbon compounds (PHCs) and the additive methyl tert‐butyl ether (MTBE) in impacted high salinity groundwater. The test was carried out adjacent to an operational hydrocarbon fuel facility in Western Saudi Arabia. The pilot test was based on the results of laboratory tests, which suggested that hydrogen peroxide stabilized with citric acid (C6H8O7) would enhance the degradation of the dissolved PHCs and associated MTBE within a saline groundwater. A 7.5 weight percent hydrogen peroxide solution was injected into a series of injection wells positioned to target a PHC‐impacted plume within an unconfined aquifer. The plume contains total benzene, toluene, ethylbenzene, and xylenes (BTEX) at concentrations up to 6,890 micrograms per liter (μg/L). The MTBE concentration within the groundwater was detected at concentrations of up to 55,182 μg/L, whereas the groundwater salinity was approximately 7,000 milligrams per liter (mg/L). A total of 9,012 liters of citric acid‐stabilized hydrogen peroxide solution was injected over three events spaced over a 1‐month period. The results of the pilot test indicated that injection of stabilized hydrogen peroxide was effective in reducing the concentration of dissolved PHCs within the plume, including BTEX and other aromatic hydrocarbons. The average concentration decrease for total BTEX was 72% with up to 97.4% reduction being measured in a sample collected from one key monitoring well during the treatment period. MTBE was also effectively treated during the pilot test with an average MTBE degradation of 50% being realized during the test and up to 86% concentration decrease being measured in some groundwater samples. While reductions in MTBE concentrations were noted, no increase in tertiary butyl alcohol was measured, which is a promising finding. The general water quality did not fluctuate significantly between pre‐ and postinjection with the pH, oxidation–reduction potential, and dissolved oxygen remaining relatively constant. The dissolved iron, nitrate, and sulfate concentrations vary during the injection period with nitrate decreasing to below detection limits following the final injection, whereas sulfate decreased in two of the three monitoring wells following the injection. Dissolved iron concentrations remained relatively constant in two of the three monitoring wells (NJBP45 and NJBP46) during the injection events, whereas dissolved iron in monitoring well NJBP44 decreased from a baseline concentration of 1.03 μg/L to 0.09 μg/L, suggesting that the ferrous iron in solution was being oxidized to ferric iron. Measurements of the preinjection microbiological community indicated that the community is diverse within the injection area based on deoxyribonucleic acid extraction by polymerase chain reaction as well as sequencing and clustering. Subsequent analyses of the microbiological community postinjection indicated that the community diversity and biomass was reduced with a shift to a more aerobic population, at least over the short term. Results of compound specific isotope analyses are consistent with the concentration data and show petroleum hydrocarbon and MTBE was degraded by the citric acid‐stabilized hydrogen peroxide treatment.

Treating MTBE-contaminated water using sewage sludge-derived activated carbon.

In this study, sewage sludge-derived activated carbon (SDAC) was synthesized, characterized, and tested for its potential as an adsorbent of methyl tert-butyl ether (MTBE). The SDAC was produced by activating the sludge with zinc chloride and subsequently subjected to various ranges of pyrolytic temperatures. It was then characterized using SEM/EDX, BET, and TGA. The SEM-EDX analyses showed that impurities like Fe, Al, Mg, Mn, Ca, and Na of the raw sludge were removed by the higher pyrolytic temperature and acid-washing procedures. TGA showed the thermal stability of the produced material. Results of the BET revealed a significant increase in surface area of the sludge from 1.5m2/g to 385m2/g after acid washing. The MTBE removal efficiency of 70% was achieved after 60min with 2g/L of SDAC at pH6, and initial MTBE concentration of 1ppm. The adsorption kinetics of SDAC fitted into pseudo-second-order reactions. This work demonstrated a beneficial use of a bio-waste material (sewage sludge) in water treatment technologies.

ELIMINACIÓN MEJORADA DE METIL TERC-BUTIL ÉTER POR UN CONSORCIO BACTERIANO SUPLEMENTADO CON EXTRACTO DE LEVADURA

Methyl tert-butyl ether (MTBE) is highly soluble in water and considered a contaminant. Although MTBE can be removed by microbial consortia its removal efficiency is low due to its toxic effect on microbial growth. An alternative to enhance the MTBE degradation efficiency is by cometabolism. Yeast extract (cometabolite) was studied in the EB-MTBE-24 consortium to enhance the MTBE degradation efficiency in cultures at 110 mg L-1 of MTBE and in cultures at 110 mg L-1 of MTBE supplemented with 100 and 500 mg L-1 of yeast extract (100YE and 500YE, respectively). The 100YE culture presented higher values of​ mmax= 0.07±0.02 h-1, degradation efficiency 77.63 ± 1.16 % and a global degradation rate 0.90 ± 0.05 h-1 than the culture without YE addition. The 500YE culture presented the lowest MTBE degradation efficiency. The kinetics of MTBE degradation for the 100YE culture is described by first-order and pseudo-first-order reaction models. The cultivable fraction of the EB-MTBE-24 consortium is constituted by Sphingobium barthaii C1, Gordonia polyisoprenivorans C2, and Ochrobactrum anthropi C3. The 100YE culture of the EB-MTBE-24 consortium possess a greater potential to degrade high MTBE concentrations at a high rate suggesting that the YE minimizes the MTBE inhibitory effect on microbial growth.

Mycobacterial Response to Organic Solvents and Possible Implications on Cross-Resistance With Antimicrobial Agents.

Mycobacterium vaccae, a bacterium found in soil, has been receiving attention as adjuvant to antituberculosis treatment, vaccines and immunotherapies and even as antidepressant. This bacterium is also able to degrade several pollutants, including aromatic compounds. The increasing presence of organic solvents in the environment may lead to M. vaccae adapted populations. A possible relationship between solvent tolerance and decreased susceptibility to other types of chemicals, including antibiotics, may pose a problem during opportunistic infections. The present study thus aimed at assessing if solvent adapted cells presented higher tolerance to antibiotics and efflux pump inhibitors (EPIs). M. vaccae cells were able to thrive and grow in the presence of up 20% (v/v) glycerol, 5% (v/v) ethanol, 1% (v/v) methyl tert-butyl ether (MTBE) and 0.1% (v/v) toluene. During adaptation to increasing concentration of ethanol and MTBE, the cells changed their fatty acid profile, zeta potential and morphology. Adapted cells acquired an improved tolerance toward the EPIs thioridazine and omeprazole, but became more susceptible to the antibiotics levofloxacin and teicoplanin when compared with non-adapted cells.

Treatment of the Waste Gas Containing Methyl tert-Butyl Ether via a Biotrickling Filter

The performance and microbial communities of methyl tert-butyl ether (MTBE) treatment using a biotrickling filter (BTF) that was inoculated with activated sewage sludge were investigated. The BTF successfully started up within 23 days when the inlet concentration of MTBE was 100 mg·m-3 and empty bed retention time was 60 s, with 70% removal efficiency (RE). Under steady-state conditions, an elimination capacity (EC) and a mineralization ratio of 13.47 g·(m3·h)-1 and 68% were achieved, respectively. The ECmax was 21.03 g·(m3·h)-1 according to the Haldane model, and a KS of 0.16 g·m-3 and KI of 0.99 g·m-3 were obtained. High-throughput sequencing was used to identify the community structure of the mixed microbial consortium in the BTF. The results indicated that Methylibium sp. (11.33%) and Blastocatella sp. (9.95%) were the dominant bacteria.

Kinetic and equilibrium modelling of MTBE (methyl tert-butyl ether) adsorption on ZSM-5 zeolite: Batch and column studies

The intensive use of methyl tert-butyl ether (MTBE) as a gasoline additive has resulted in serious environmental problems due to its high solubility, volatility and recalcitrance. The feasibility of permeable reactive barriers (PRBs) with ZSM-5 type zeolite as a reactive medium was explored for MTBE contaminated groundwater remediation. Batch adsorption studies showed that the MTBE adsorption onto ZSM-5 follows the Langmuir model and obeys the pseudo-second-order model with an adsorption capacity of 53.55 mg g−1. The adsorption process reached equilibrium within 24 h, and MTBE was barely desorbed with initial MTBE concentration of 300 mg L−1. The mass transfer process is found to be primarily controlled by pore diffusion for MTBE concentrations from 100 to 600 mg L−1. pH has little effect on the maximum adsorption capacity in the pH range of 2–10, while the presence of nickel reduces the capacity with Ni concentrations of 2.5–25 mg L−1. In fixed-bed column tests, the Dose-Response model fits the breakthrough curve well, showing a saturation time of ∼320 min and a removal capacity of ∼18.71 mg g−1 under the conditions of this study. Therefore, ZSM-5 is an extremely effective adsorbent for MTBE removal and has a huge potential to be used as a reactive medium in PRBs.

Polypyrrole-Grafted Coconut Shell Biological Carbon as a Potential Adsorbent for Methyl Tert-Butyl Ether Removal: Characterization and Adsorption Capability.

Methyl tert-butyl ether (MTBE) has been used as a common gasoline additive worldwide since the late twentieth century, and it has become the most frequently detected groundwater pollutant in many countries. This study aimed to synthesize a novel microbial carrier to improve its adsorptive capacity for MTBE and biofilm formation, compared to the traditional granular activated carbon (GAC). A polypyrrole (PPy)-modified GAC composite (PPy/GAC) was synthesized, and characterized by Fourier transform infrared spectroscopy (FT-IR) and Brunauer-Emmett-Teller (BET) surface area analysis. The adsorption behaviors of MTBE were well described by the pseudo-second-order and Langmuir isotherm models. Furthermore, three biofilm reactors were established with PPy/GAC, PPy, and GAC as the carriers, respectively, and the degradation of MTBE under continuous flow was investigated. Compared to the biofilm reactors with PPy or GAC (which both broke after a period of operation), the PPy/GAC biofilm column produced stable effluents under variable treatment conditions with a long-term effluent MTBE concentration <20 μg/L. Pseudomonas aeruginosa and Acinetobacter pittii may be the predominant bacteria responsible for MTBE degradation in these biofilm reactors.

Using intrinsic bioremediation for petroleum–hydrocarbon contaminated groundwater cleanup and migration containment: Effectiveness and mechanism evaluation

Intrinsic bioremediation (IB) is the major mechanism causing the containment of petroleum hydrocarbons in groundwater. The effectiveness and mechanisms of IB on the contaminant removal were evaluated in this study. Groundwater was analyzed for the efficiency of IB, dominant bacteria, bacterial diversity, and biodegradation rates. Concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX) and methyl tert-butyl ether (MTBE) dropped from 6.5 and 0.14 mg/L in source area to 67 and 19 µg/L at the 145 m downgradient area. The biodegradation capacities for BTEX (50.9 mg/L) and MTBE (58.5 mg/L) were higher than the BTEX (6.5 mg/L) and MTBE (0.14 mg/L) concentrations within the plume. The bacterial diversities were assessed by 16S rRNA-based denatured gradient gel electrophoresis and nucleotide sequence analyses. More than 21 petroleum–hydrocarbon biodegrading bacterial species were detected in groundwater indicating that contaminants could be biodegraded by natural-occurring bacteria. The calculated MTBE and BTEX first-order decay rates were 5.7 × 10−4 and 1.3 × 10−3 per day, respectively. The high decay rates indicate that IB mechanisms played important roles in contaminant removal. The observed evidences of IB processes in highly contaminated areas included: (1) decreased electron acceptors, (2) production of degradation byproducts, (3) increased microbial populations and alkalinity, and (4) decreased electron donors and pH.