Methyl Tertiary Butyl Ether Concentrations Research Articles

Eco-friendly removal of methyl tert-butyl ether from contaminated water using steam and CO2-activated carbons

AbstractPetrol frequently contains the additive methyl tertiary butyl ether (MTBE). Because of its significant health risks, MTBE pollution of surface and ground water is a severe concern for the environment. Highly porous physically activated carbons, particularly CO2-activated carbon (CO2-AC) and steam-activated carbon (Steam-AC), were obtained from date stones as potential eco-friendly adsorbents for MTBE from contaminated water. The chemical composition, microstructure, textural, and structural characteristics of adsorbents were characterised by elemental analysis, SEM, N2 sorption, XRD, and FTIR. The adsorption process evaluation based on the initial MTBE concentration, liquid-to-solid ratio, and equilibrium contact time. CO2-AC and steam-AC adsorbents have high surface areas of 819.5 m2/g, and 567.7 m2/g, respectively. At 40 °C, CO2-AC has an adsorption capability of 181.36 mg/g. The adsorption result was best fitted by the Freundlich model. The two-step intraparticle diffusion process prevailed the adsorption process, and the pseudo-second-order model presented an optimal fit for the adsorption kinetics models. Spontaneous physical adsorption was endothermic when CO2-AC adsorbs at 40 °C because ∆G was − 6.34 kJ/mol. Finally, the water quality improved and the salt content, the alkalinity, and the hardness decreased with the use of CO2-AC as an environmentally friendly adsorbent for removing MTBE from the polluted water.

The efficiency of the microbial fuel cell reactor in biodegradation of methyl tertiary butyl ether and electricity generation from wastewater: Effects of co-substrate, surfactant, and membrane changes

This study highlights the promising potential of utilizing an MFC reactor equipped with Nafion 117 and PVA/GA membranes. This innovative and cost-effective approach has proven to be highly effective in addressing the challenge of treating methyl tertiary butyl ether (MTBE) in wastewater, while also offering the added benefit of electricity generation. Biodegradation efficiency and electricity generation were assessed in this study using co-substrates such as glucose (GLS) and sodium acetate (SAC), in addition to surfactants like sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB). The MTBE concentration ranged from 10 to 200 mg/L, and it was quantified in the samples through gas chromatography with a flame ionization detector (GC–FID). To explore the structural characteristics of Nafion 117 and PVA/GA membranes, we conducted field emission scanning electron microscopy (FESEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analyses. The maximum biodegradation efficiency of MTBE (%) in MFC reactors with Nafion 117 and PVA/GA membranes was found to be 93.3% and 89.8%, accompanied by maximum production voltages (mV) of 895 mV and 853 mV, respectively. This was achieved with the addition of SAC co-substrate and SDS surfactant. Notably, the addition of co-substrate had a more significant impact compared to the surfactant. Simultaneously adding both the co-substrate and surfactant had a substantial effect on both the biodegradation efficiency (%) of MTBE and the generated voltage. Based on these findings, it can be concluded that the MFC reactor equipped with Nafion 117 and PVA/GA membranes is capable of effectively breaking down MTBE. However, due to its lower cost, the PVA/GA membrane may be considered a more economical choice. Therefore, the utilization of an MFC reactor featuring Nafion 117 and PVA/GA membranes holds great promise as an efficient approach for treating MTBE in wastewater, while concurrently generating electricity.

Changes in geotechnical properties of soil contaminated by methyl tertiary butyl ether (MTBE)

As an extensively used gasoline additive, methyl tertiary butyl ether (MTBE) can leak into the subsurface, and this not only damages the ecological environment but also affects the geotechnical characteristics of the soil. In this study, the geotechnical properties of MTBE-contaminated soil, such as the basic physical properties of strength, compressibility, hydraulic conductivity, leachability, electrical resistivity and microstructural characteristics, are comprehensively investigated. The results show that the Atterberg limits consistently decrease with increasing MTBE content in the soil. As the MTBE content increases from 0 to 10%, the specific surface area of the soil decreases by 28%, the sand content increases by 22%, and the clay and silt contents decrease by 3 and 18%, respectively. The soil compression index, hydraulic conductivity, leached MTBE concentration and electrical resistivity increase, while the unconfined compressive strength (UCS) decreases, with increasing MTBE content. Microstructural analysis shows that increasing the MTBE content results in mineralogical alterations that decrease the illite and kaolinite content of the soil. The aggregation and flocculated structures can be detected by an increase in the number and size of inter-aggregate pores. In addition, the electrical resistivity of the contaminated soil is used to assess the geotechnical properties of the MTBE-contaminated soil based on well-established empirical relations.

Oxidative stress and DNA damage in earthworms induced by methyl tertiary-butyl ether in natural soils.

Adverse effects of methyl tertiary-butyl ether (MTBE) have been noticed at different trophic levels by international researchers. However, there was unclear evidence about its effects on oxidative stress and DNA damage in earthworms. In this study, earthworms were cultivated in various doses of MTBE (0.0mg/kg, 10.0mg/kg, 30.0mg/kg, and 60.0mg/kg) contaminated agricultural soil for 7days, 14days, 21days, and 28days, respectively. The result showed that the reactive oxygen species (ROS) content of earthworms significantly increased in MTBE treatment groups compared to the control group. In MTBE treatment groups, the activities of superoxide dismutase, catalase, peroxidase, and glutathione S-transferase were significantly activated at the exposure of 7days, which increased by 36.3-78.9%, 51.8-97.3%, 36.5-61.9%, and 12.0-54.8%, respectively. Then, the activities of these defense enzymes showed various changes following the changes in exposure times and MTBE concentrations. Especially in the 60.0mgkg-1 group, both antioxidant enzymes and GST were still significantly activated at the exposure of 14days and then significantly inhibited at the exposure of 28days. The analysis of olive tail moment showed significant DNA damage in the 10.0mgkg-1 group at the exposure of 28days, and this damage in 30.0mg/kg and 60.0mg/kg groups was found at the exposure of 7days. This result was consistent with the malondialdehyde accumulation in earthworms. Additionally, the analysis of IBRv2 showed the effects of MTBE treatments on earthworms in dose- and time-dependent manners. This study helps better to understand the effects of MTBE on soil invertebrate animals and provide theoretical support for soil protection in governing MTBE application.

Fabrication and photocatalytic activity of Fe3O4/SiO2/TiO2 magnetic nanoparticles removing MTBE from simulated water

ABSTRACT The removal of methyl tertiary butyl ether (MTBE) from simulated water is going to be a critical environmental issue. The aims of the present study are to synthesise the Fe3O4/SiO2/TiO2 magnetic nanoparticles (MNPs) and evaluate its efficiency for the removal of MTBE by UV/O3/Fe3O4/SiO2/TiO2 combined process (CP) from water. The MNPs were synthesised via modified method and characterised using XRD, SEM and EDS. Then, the effects of initial ozone concentration, pH, MNP concentration, initial MTBE concentration (C0) and irradiation time were evaluated. The findings depicted that the performance of CP is better than separate processes. The optimum condition with initial ozone concentration of 150 mg/L, pH of 8, MNP concentration of 0.1 g/L and C0 of 10 mg/L at 60 min irradiation time results in maximum degradation of MTBE up to 91.65%. Also, the mineralisation rate of MTBE was achieved 68% removal at the same condition. Kinetic profile presented that the reduction of MTBE was fitted into second-order kinetics model for all the runs. The findings illustrate the capabilities of CP as a reliable technology to remove MTBE contained in water.

Impact Effect of Methyl Tertiary-Butyl Ether "Twelve Months Vapor Inhalation Study in Rats".

Simple SummaryThe detection of major blood-based markers for cancer requires expensive blood tests. Therefore, finding simple and effective blood-based markers is of great interest. The present results suggested that CA II, CA I, and peroxiredoxin2 could be utilized as potential biomarkers for the early detection of tracheal and lung cancer.We investigated the early risk of developing cancer by inhalation of low doses (60 µL/day) of methyl tertiary butyl ether (MTBE) vapors using protein SDS-PAGE and LC-MS/MS analysis of rat sera. Furthermore, histological alterations were assessed in the trachea and lungs of 60 adult male Wistar rats. SDS-PAGE of blood sera showed three protein bands corresponding to 29, 28, and 21 kDa. Mass spectroscopy was used to identify these three bands. The upper and middle protein bands showed homology to carbonic anhydrase 2 (CA II), whereas the lower protein band showed homology with peroxiredoxin 2. We found that exposure to MTBE resulted in histopathological alterations in the trachea and the lungs. The histological anomalies of trachea and lung showed that the lumen of trachea, bronchi, and air alveoli packed with free and necrotic epithelial cells (epithelialization). The tracheal lamina propria of lung demonstrated aggregation of lymphoid cells, lymphoid hyperplasia, hemorrhage, adenomas, fibroid degeneration, steatosis, foam cells, severe inflammatory cells with monocytic infiltration, edema, hemorrhage. Occluded, congested, and hypertrophied lung arteries in addition, degenerated thyroid follicles, were observed. The hyaline cartilage displayed degeneration, deformation, and abnormal protrusion. In conclusion, our results suggest that inhalation of very low concentrations of the gasoline additive MTBE could induce an increase in protein levels and resulted in histopathological alterations of the trachea and the lungs.

Methyl Tertiary-Butyl Ether Exposure from Gasoline in the U.S. Population, NHANES 2001-2012.

Background:Methyl tertiary-butyl ether (MTBE) was used as a gasoline additive in the United States during 1995–2006. Because of concerns about potential exposure and health effects, some U.S. states began banning MTBE use in 2002, leading to a nationwide phaseout in 2006.Objectives:We investigated the change in blood MTBE that occurred during the years in which MTBE was being phased out of gasoline.Methods:We used data from the National Health and Nutrition Examination Survey (NHANES) from 2001–2012 to assess the change in blood MTBE over this period. We fit sample-weighted multivariate linear regression models to 12,597 human blood MTBE concentrations from the NHANES 2001–2002 to 2011–2012 survey cycles.Results:The unweighted proportion of the individuals with MTBE blood levels above the limit of detection (LOD) of was 93.9% for 2001–2002. This portion dropped to 25.4% for the period 2011–2012. Weighted blood MTBE median levels (ng/L) (25th and 75th percentiles) decreased from for the period from 2001–2002 to for the period from 2005–2006. For the entire postban period (2007–2012), MTBE median levels were below the detection limit of .Discussion:These decreases in blood MTBE coincided with multiple statewide bans that began in 2002 and a nationwide ban in 2006. The multivariate log-linear regression model for the NHANES 2003–2004 data showed significantly higher blood MTBE concentrations in the group who pumped gasoline less than 7 h before questionnaire administration compared to those who pumped gasoline more than 12 h before questionnaire administration (). This study is the first large-scale, national-level confirmation of substantial decrease in blood MTBE levels in the general population following the phaseout of the use of MTBE as a fuel additive. https://doi.org/10.1289/EHP5572

Remediation of MTBE-contaminated groundwater by integrated circulation wells and advanced oxidation technologies

Abstract The proximity of shallow groundwater systems to sources of contamination usually exposes them to severe environmental threats. Hazardous pollutants that leak from gas stations, landfills, and industrial facilities may eventually reach the underneath shallow groundwater aquifers, posing risks to human health and the environment. Cleaning contaminated groundwater sources has always been a challenge to the local authorities. This is even more challenging when dealing with difficult pollutants such as methyl tertiary butyl ether (MTBE) due its high solubility in water, poor biodegradability, and poor adsorption onto solids. This study aims to assess the efficiency of a pilot groundwater remediation system to treat a shallow aquifer contaminated with MTBE. The in-house designed and fabricated pilot system combines the technology of circulation wells and UV-based advanced oxidation technology for the breakdown and removal of MTBE from water. An ultraviolet/hydrogen peroxide (UV/H2O2) process was used in this study to remove MTBE from water. The concentration of MTBE was reduced from approximately 1,400 μg/L to as low as 34 μg/L within 30 minutes, with a treatment efficiency of about 98%. The study also assesses the effects of the UV intensity and the treatment time needed to remove the target pollutant.

Employing response surface analysis using for photocatalytic degradation of MTBE by nanoparticles

Since groundwaters are a major source of drinking water, their pollution with organic contaminants such as methyl tertiary-butyl ether (MTBE) is a very significant issue. Hence, this research investigated the photocatalytic degradation of MTBE in an aqueous solution of TiO2-ZnO-CoO nanoparticle under UV irradiation. In order to optimize photocatalytic degradation, response surface methodology was applied to assess the effects of experimental variables such as catalyst loading, initial concentration of MTBE and pH on the dye removal efficiency. The optimal condition to achieve the best degradation for the initial concentration of 30.58 mg/L of MTBE was found at a pH of 7.68 and a catalyst concentration of 1.68 g/L after 60 min.

Exposure to hazardous air pollutants in underground car parks in Guangzhou, China

Volatile organic compounds (VOCs), carbon monoxide (CO), and PM10 were studied by field sampling in six underground car parks beneath multi-level buildings in Guangzhou, China. CO and PM10 in the car parks range from 3.0 to 69.0 ppm and 0.087 to 0.698 mg m−3, with mean concentrations of 10.8 ppm and 0.228 mg m−3, respectively. Overall mean concentrations of methyl tertiary-butyl ether (MTBE), benzene, toluene, ethyl-benzene, and xylene (BTEX) are 90.5, 54.8, 239.9, 47.7, and 189.3 μg m−3, respectively. Indoor air pollutants in the car parks show an obvious seasonal variation and are higher in winter than in summer. The total estimated cancer risks of occupational exposure for car park staff and casual exposure for parking users are 3.73 × 10−4 and 5.60 × 10−6, indicating definite and possible risks, respectively. The hazard quotient of target VOCs is 4.33, implying a definite risk for people using underground car parks. Indoor/outdoor (I/O) ratios for MTBE and BTEX are significantly higher than one, reflecting strong emission sources in underground car parks. The BTEX to MTBE ratios in the car parks are almost the same as those in tunnel air, indicating that indoor aromatic hydrocarbons were mainly from engine emissions and gasoline evaporation. With increasing urbanization in China, more attention should be paid to the exposure of staff and users to hazardous air pollutants in underground car parks.

Relationship between Methyl Tertiary Butyl Ether Exposure and Non-Alcoholic Fatty Liver Disease: A Cross-Sectional Study among Petrol Station Attendants in Southern China.

Methyl tertiary butyl ether (MTBE)—A well known gasoline additive substituting for lead alkyls—causes lipid disorders and liver dysfunctions in animal models. However, whether MTBE exposure is a risk factor for non-alcoholic fatty liver disease (NAFLD) remains uncertain. We evaluate the possible relationship between MTBE exposure and the prevalence of NAFLD among 71 petrol station attendants in southern China. The personal exposure concentrations of MTBE were analyzed by Head Space Solid Phase Microextraction GC/MS. NAFLD was diagnosed by using abdominal ultrasonography according to the guidelines for the diagnosis and treatment of NAFLD suggested by the Chinese Hepatology Association. Demographic and clinical characteristics potentially associated with NAFLD were investigated. Mutivariate logistic regression analysis was applied to measure odds ratios and 95% confidence intervals (CI). The result showed that the total prevalence of NAFLD was 15.49% (11/71) among the study subjects. The average exposure concentrations of MTBE were 292.98 ± 154.90 μg/m3 and 286.64 ± 122.28 μg/m3 in NAFLD and non-NAFLD groups, respectively, and there was no statistically significant difference between them (p > 0.05). After adjusting for age, gender, physical exercise, body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP), alanine aminotransferase (ALT), white blood cell (WBC), total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL), and high-density lipoprotein (HDL), the odds ratios were 1.31 (95% CI: 0.85–1.54; p > 0.05), 1.14 (95% CI: 0.81–1.32; p > 0.05), 1.52 (95% CI: 0.93–1.61; p > 0.05) in the groups (including men and women) with exposure concentrations of MTBE of 100–200 μg/m3, 200–300 μg/m3, and ≥300 μg/m3, respectively, as compared to the group (including men and women) ≤100 μg/m3. Our investigation indicates that exposure to MTBE does not seem to be a significant risk factor for the prevalence of NAFLD among petrol station attendants in southern China.

Catalyzed hydrogen peroxide combined with CO2 sparging for the treatment of contaminated groundwater

In this work we propose and investigate an innovative groundwater remediation option based on the combination of catalyzed hydrogen peroxide (H2O2) with CO2 sparging. The effectiveness of this new process was evaluated by carrying out lab-scale tests on a soil–water system spiked with Methyl Tertiary Butyl Ether (MtBE). The results achieved with the combined process, evaluated in terms of H2O2 lifetime and MtBE residual concentration in the liquid phase, were then compared with those obtained using H2O2 only or amended with KH2PO4 as stabilizing agent. The experimental results showed that the combined H2O2–CO2 process has basically two beneficial effects. On the one hand, fluxing CO2 into the oxidizing solution can lead to a pH decrease to acidic values that enhance the H2O2 stability. Indeed, from the results obtained in the stability tests carried out, it was observed that the hydrogen peroxide lifetime in the combined H2O2–CO2 process proved to be longer than the one achieved in the tests carried out with H2O2 only, although slightly lower than the one achieved using KH2PO4 as stabilizing agent. On the other hand, it was observed that with respect to a traditional chemical oxidation application, the CO2 sparging can further enhance the overall effectiveness of the process as a result of contaminant stripping by CO2. Indeed, the residual MtBE concentration observed after application of the combined H2O2–CO2 process was slightly lower than the ones obtained using H2O2 only or comparable to the one achieved using H2O2 amended with KH2PO4. Overall, these results showed that the combined H2O2–CO2 process could represent a promising alternative to traditional formulations, avoiding the use of chemical amendments, while leading to comparable residual contaminant’s concentration.

Application of first order kinetics to characterize MTBE natural attenuation in groundwater

Methyl tertiary butyl ether (MTBE) was a gasoline oxygenate that became widely used in reformulated gasoline as a means to reduce air pollution in the 1990s. Unfortunately, many of the underground storage tanks containing reformulated gasoline experienced subsurface releases which soon became a health concern given the increase in public and private water supplies containing MTBE. Many states responded to this by banning the use of MTBE as an additive, including Connecticut. Although MTBE dissipates by natural attenuation, it continues to be prevalent in groundwater long after the Connecticut ban in 2004. This study estimated the rate of the natural attenuation in groundwater following the Connecticut ban by evaluating the MTBE concentration two years prior to and two years after the MTBE ban at eighty-three monitoring wells from twenty-two retail gasoline stations where MTBE contamination was observed. Sites chosen for this study had not undergone active remediation ensuring no artificial influence to the natural attenuation processes that controls the migration and dissipation of MTBE. Results indicate that MTBE has dissipated in the natural environment, at more than 80% of the sites and at approximately 82% of the individual monitoring wells. In general, dissipation approximated first order kinetics. Dissipation half-lives, calculated using concentration data from the two year period after the ban, ranged from approximately three weeks to just over seven years with an average half-life of 7.3months with little variability in estimates for different site characteristics. The accuracy of first order estimates to predict further MTBE dissipation were tested by comparing predicted concentrations with those observed after the two year post-ban period; the predicted concentrations closely match the observed concentrations which supports the use of first order kinetics for predictions of this nature.

Toxicity of methyl tertiary-butyl ether on human blood lymphocytes.

Methyl tertiary-butyl ether (MTBE) is a synthetic solvent widely used as oxygenate in unleaded gasoline. Few studies have addressed the cellular toxicity of MTBE on some cell lines, and so far, no comprehensive study has been conducted to investigate the probable immunotoxicity of this compound. In this study, the toxicity of MTBE on human blood lymphocytes was evaluated. Blood lymphocytes were isolated from healthy male volunteers' blood, using Ficoll polysaccharide followed by gradient centrifugation. Cell viability, reactive oxygen species (ROS) formation, lipid peroxidation, glutathione levels, and damage to mitochondria and lysosome were determined in blood lymphocytes after 6-h incubation with different concentrations of MTBE (0.1, 0.5, 1, and 2mM). Our results showed that MTBE, in particular, decreased cell viability, which was associated with significant increase at intracellular ROS level and toxic alterations in mitochondria and lysosomes in human blood lymphocytes. Moreover, it was shown that MTBE strongly provoked lipid peroxidation and also depleted glutathione level at higher concentrations. Interestingly, MTBE exhibited its cytotoxic effects at low concentrations that may resemble to its concentrations in human blood following occupational and environmental exposure. It is therefore concluded that MTBE was capable of inducing oxidative stress and damage to mitochondria and lysosomes in human lymphocytes at concentrations ranging from 5 to 40μg/L, which may be present in human blood as a result of environmental exposure.

A comparative study of removal of methyl tertiary-butyl ether (MTBE) from aquatic environments through advanced oxidation methods of H2O2/nZVI, H2O2/nZVI/ultrasound, and H2O2/nZVI/UV

AbstractThis study compares the efficiency of oxidation with H2O2 and nanoscale zero-valent iron (nZVI)in the presence of ultrasound and that of oxidation with ultraviolet radiation and H2O2/nZVI in the removal of MTBE from aqueous solutions. The effects of some parameters, such as ultrasound, contact time (2–60 min), concentration of hydrogen peroxide (5–20 ml/L), concentrations of nZVI (0.15–0.45 g/L), pH (2–9), and concentration of MTBE (50–750 mg/L) were investigated. In this study, the best MTBE removal efficiency was obtained at a rate of 89.56% in a concentration of 50 mg/Lat pH 3.5 with optimal H2O2 concentration of 10 ml/L, nZVI concentration of 0.25 g/L, and oxidation time of 15 min. Comparison of the effects of ultrasound with those of ultraviolet radiation, in similar conditions, showed no significant difference in efficiency between the ultrasound and UV (p ˃ 0.05). However, comparing the efficiency of oxidation in the presence of ultrasound and without ultrasound in similar oxidation conditi...

Concentrations and potential health risks of methyl tertiary-butyl ether (MTBE) in air and drinking water from Nanning, South China

Levels of methyl tertiary-butyl ether (MTBE) in occupational air, ambient air, and drinking water in Nanning, South China, were investigated, and then their potential health risks to occupational workers and the general public were evaluated. Results show that the MTBE concentration in occupational air from 13 service stations was significantly higher than that in ambient air from residential areas (p<0.0001); both are far lower than the threshold limit value-time weighted average of MTBE regulated in the United States (US). The drinking water samples from household taps yielded detectable MTBE in the range of 0.04–0.33μg/L, which is below the US drinking water standard of 20–40μg/L. The non-carcinogenic risk of MTBE from air inhalation may be negligible because the calculated hazard quotient was less than 1. The mean MTBE lifetime cancer risk was within the acceptable limit of 1×10−6 to 1×10−4, but the lifetime cancer risk of refueling workers in the urban service station at the 95th percentile slightly exceeded the maximum acceptable carcinogen risk (1×10−4), indicating the potential carcinogenic health effects on the population highly exposed to MTBE in this region. The hazard index and carcinogenic risk of MTBE in drinking water were significantly lower than the safe limit of US Environmental Protection Agency, suggesting that drinking water unlikely poses significant health risks to the residents in Nanning.

Effects of pH on the Kinetics of Methyl Tertiary Butyl Ether Degradation by Oxidation Process (H2O2/Nano Zero-Valent Iron/Ultrasonic)

Background: In advanced oxidation processes, pH has a significant effect on the removal efficiency of organic compounds. This study examined the effect of pH changes on the removal efficiency and kinetics of methyl tertiary butyl ether (MTBE) concentration in aquatic environment. Objectives: The primary objective of this study was to evaluate the effect of pH changes on removal kinetics of the mentioned compound, using H2O2/nZVI (nano zero-valent iron)/ultrasonic process, and its impact on the reaction rate. Materials and Methods: In order to create the right conditions for oxidation, first of all iron nanoparticles combined with H2O2 oxidizer were synthesized, and then they were subjected to ultrasound waves and used in MTBE oxidation. In MTBE removal via H2O2/nZVI/Ultrasonic process, the effects of some parameters such as contact time (2 to 60 minutes), concentration of hydrogen peroxide (5 to 20 mL/L), concentrations of nZVI (0.15 to 0.45 g/L), MTBE concentrations (50 to 750 mg/L), and pH (2 to 9) were investigated. MTBE concentration analysis was performed using gas chromatography (GC). Results: According to this study, the best removal efficiency of 50 mg/L MTBE concentration in 89.56% under oxidation condition occurred when H2O2 level equals to 10 mL/L, nZVI is 0.25 g/L at pH 3.5. The results showed that the increase or decrease of pH from 3.5 results in a loss of oxidation efficiency as well as reduction in the amount of kap. In addition, the logarithmic changes curve of MTBE concentration showed that MTBE oxidation in H2O2/nZVI/ultrasonic method follows pseudo first order reactions. Conclusions: Changes of pH could remarkably affect the efficiency and oxidation rate of MTBE. In particular, the amount of kap in terms of oxidation declines substantially by moving away from the optimum pH range. In this study, pH 3.5 was considered as the optimal pH in H2O2/nZVI/ultrasonic oxidation process, with the elimination of about 89.56% of the high MTBE concentration. In general, we can say that by adjusting pH in this range, the rate and efficiency of MTBE oxidation can be enhanced in H2O2/nZVI/ultrasonic method.

Chemical Oxidation Performance in High Temperature, Saline Groundwater Impacted With Hydrocarbons

A series of laboratory microcosm experiments and a field pilot test were performed to evaluate the potential for in situ chemical oxidation (ISCO) of aromatic hydrocarbons and methyl tertiary butyl ether (MTBE), a common oxygenate additive in gasoline, in saline, high temperature (more than 30 °C) groundwater. Groundwater samples from a site in Saudi Arabia were amended in the laboratory portion of the study with the chemical oxidants, sodium persulfate (Na2S2O8) and sodium percarbonate (Na2(CO3)2), to evaluate the changes in select hydrocarbon and MTBE concentrations with time. Almost complete degradation of the aromatic hydrocarbons, naphthalene and trimethylbenzenes (TMBs), was found in the groundwater sample amended with persulfate, whereas the percarbonate‐amended sample showed little to no degradation of the target hydrocarbon compounds in the laboratory. Isotopic analyses of the persulfate‐amended samples suggested that C‐isotope fractionation for xylenes occurred after approximately 30 percent reduction in concentration with a decline of about 1 percent in the δ13C values of xylenes. Based on the laboratory results, pilot‐scale testing at the Saudi Arabian field site was carried out to evaluate the effectiveness of chemical oxidation using nonactivated persulfate on a high temperature, saline petroleum hydrocarbon plume. Approximately 1,750 kg of Na2S2O8 was delivered to the subsurface using a series of injection wells over three injection events. Results obtained from the pilot test indicated that all the target compounds decreased with removal percentages varying between 86 percent for naphthalene and more than 99 percent for the MTBE and TMBs. The benzene, toluene, ethylbenzene, and xylene compounds decreased to 98 percent on average. Examination of the microbial population upgradient and downgradient of the ISCO reactive zone suggested that a bacteria population was present following the ISCO injections with sulfate‐reducing bacteria (SRB) being the dominant bacteria present. Measurements of inorganic parameters during injection and postinjection indicated that the pH of the groundwater remained neutral following injections, whereas the oxidation–reduction potential remained anaerobic throughout the injection zone with time. Nitrate concentrations decreased within the injection zone, suggesting that the nitrate may have been consumed by denitrification reactions, whereas sulfate concentrations increased as expected within the reactive zone, suggesting that the persulfate produced sulfate. Overall, the injection of the oxidant persulfate was shown to be an effective approach to treat dissolved aromatic and associated hydrocarbons within the groundwater. In addition, the generation of sulfate as a byproduct was an added benefit, as the sulfate could be utilized by SRBs present within the subsurface to further biodegrade any remaining hydrocarbons. ©2015 Wiley Periodicals, Inc.

Site characterization and risk assessment in support of the design of groundwater remediation well near a hazardous landfill

This study was undertaken to support a remediation technique that will be applied to contaminated groundwater in the vicinity of Ghonan landfill, eastern Saudi Arabia. Preliminary field investigations involved hydrogeological characterization of the entire area. The improved understanding of the underlying geology and groundwater movement gained from the preliminary studies helped in determining a test site within the proximity of the landfill. One remediation well and five monitoring wells were constructed at the test site. Optimum pumping rate for the remediation well was determined to range from 2.642 through 7.926 gallons per minute (gpm) (0.01 m3/min through 0.03 m3/min) based on site-specific hydrogeological investigations and mathematical simulation. A concentration of 0.05 mg/L of methyl tertiary-butyl ether (MTBE) contaminated the aquifer in the test site. The simulated concentration of MTBE at the point of exposure after a period of 2 years was found to be higher than the maximum contaminant level of 0.005 mg/L set by the United States Environmental Protection Agency (U.S. EPA). The results of risk assessment conducted revealed that domestic use of groundwater in the study area through any of the exposure pathways (ingestion, dermal contact, and inhalation in the shower) may lead to development of health risks to human receptors. The landfill, which is being operated as a hazardous landfill and a dump site, may become a source of groundwater pollution in its vicinity in the near future. As a potential health risk, it should be controlled properly by remediating the aquifer and implementing environmental measures to the landfill users.

Removal of Methyl Tertiary-Butyl Ether (MTBE) from Aqueous Solution Using Sunlight and Nano TiO2

Methyl tertiary-butyl ether is a synthetic compound that was developed as a technological solution to a technology-derived problem created by air pollution from vehicle emissions. Methyl tertiary-butyl ether was added to gasoline with the intent to reduce air emissions, making the fuel burn cleaner. Unfortunately, use of this air-saving gasoline additive has created one of the most threatening and widespread environmental problems for the nation's drinking water supply. In this work, degradation of methyl tertiary-butyl ether in aqueous solution using the solar ultraviolet and TiO2 nano particles was investigated. Factors that affect photocatalytic removal of methyl tertiary-butyl ether, such as pH, TiO2, and methyl tertiary-butyl ether concentrations, were studied and optimum conditions were determined using the Taguchi method for designing the experiments. Results showed that the best conditions for the removing of methyl tertiary-butyl ether in the ultraviolet/TiO2 process are 2 g/l nano TiO2 and 50 ppm methyl tertiary-butyl ether, which leads to more than 88% removal of methyl tertiary-butyl ether in 120 min.