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1.
Methyl tert-butyl ether (MTBE) biodegradation was investigated using a continuously stirred tank reactor with biomass retention (porous pot reactor) operated under aerobic conditions. MTBE was fed to the reactor at an influent concentration of 150 mg/L (1.70 mM). An identical reactor was operated as a killed control under the same conditions. Operation of these reactors demonstrated that removal of MTBE was biological and suggests that biomass retention is critical for effective degradation. MTBE removal exceeded 99.99% when the volatile suspended solids concentration in the reactor was above 600 mg/L. Batch experiments conducted using mixed liquor from the porous pot reactor indicated that the individual rates of biodegradation of MTBE and tert-butyl alcohol (TBA) increase with increasing initial concentration. When batch tests were later repeated, the MTBE degradation rates were found to have increased while the TBA degradation rates remained constant. All batch tests confirmed that the degradation rate of TBA governed the overall degradation rate (degradation rate of both MTBE and TBA). The presence of TBA at lower concentrations did not affect the rate of MTBE degradation; however, higher concentrations of TBA did reduce the rate of MTBE biodegradation.  相似文献   

2.
The feasibility of using advanced oxidation processes (AOPs): ozone, ozone/sonification, and ozone/ultraviolet (UV) irradiation in treatment to remove heavy metals and ethylenediamine tetraacetate (EDTA) from aqueous extracts, obtained after soil extraction with EDTA, was examined. Extraction of soil contaminated with 1,243?mg?kg?1 Pb and 1,190?mg?kg?1 Zn with 40?mmol?kg?1 EDTA removed 41.8±0.9 and 7.2±.0.2% of Pb and Zn. Of the AOPs tested, only the use of ozone/UV enabled the decomposition of EDTA–heavy metals complexes in aqueous soil extracts, and recovery of released Pb and Zn by sorption on a commercial sorbent Slovakite. After treatment, the concentration of Pb, Zn, and EDTA in the extracts was fairly low (2.87±1.15?mg?L?1, 7.58±2.12?mg?L?1, and 0.012±0.002?mmol?L?1, respectively), and could presumably be reduced even further with a continuation of treatment. The treated extract was used for subsequent soil rinsing, which removed an additional 12.7±1.6 and 2.7±0.1% of soil Pb and Zn. The results of our study indicate that the use of ozone/UV is a feasible option for treatment of aqueous soil extracts from EDTA extraction. Treated extracts could be safely discharged or reused to lower requirements for process water.  相似文献   

3.
2,2,3,3-Tetra-fluoro-propanol (TFP) has been extensively used in compact disk-recordable and digital versatile disk-recordable manufacture and a large amount of wastewater containing the chemical is being discharged. This investigation evaluates the feasibility and effectiveness of the use of UV, O3, and UV/O3 to degrade aqueous TFP. TFP oxidation tests were performed with initial TFP concentrations of 772–887?mg/L with various solution pH values (acidic, alkaline, uncontrolled), solution temperatures (26, 37, 48, and 60°C), and UV wavelengths (254 and 185?nm). Experimental results demonstrated that alkaline conditions favor the TFP degradation and increase the mass of TFP decomposition per unit mass of ozone consumption, in both UV254?nm/O3 and UV185?nm/O3 processes. There was no significant difference in the rate of TFP degradation when using either UV254?nm or UV185?nm. TFP exhibited zero-order degradation kinetics when sufficient ozone was supplied. A higher oxidation temperature was found to be no help for the UV/O3 oxidation of TFP in the tested concentration and temperature ranges. The cost of the UV254?nm/O3 or UV185?nm/O3 per unit volume of wastewater with an initial TFP concentration of 3,387?mg/L is comparable to that of the Fered–Fenton process as described in the literature.  相似文献   

4.
The formation of bromate by ozone–vacuum ultraviolet (VUV) (185+254??nm) process in comparison with ozone and ozone-ultraviolet (UV) (254?nm) processes of coagulated and softened water was studied. The effects of pH (7, 9, and 11), ozone dosage (1, 2, and 4?mg O3/mg C), and VUV power (30, 60, and 120?W) were investigated. Bromate concentrations formed by the ozone-VUV process were up to four and six times less than those by the ozone and ozone-UV processes, respectively. Among the variables studied, ozone dosage had the most effect on bromate formation by the ozone-VUV process. Approximately 64 and 213% increases of bromate concentration were observed when the ozone dosage was increased from 1 to 2 and 4?mg O3/mg C with VUV power of 120?W at pH 7. The bromate formation also increased as VUV power and pH increased. Hydroxyl radical exposure had a positive relationship with ozone dosage and bromate formation. Results further indicated that it might be difficult to achieve the drinking water standard for bromate and high organic matter removal concurrently.  相似文献   

5.
A hybrid bioreactor, combining an activated sludge process (ASP) and a rotating drum biofilter (RDB), was developed and evaluated for the treatment of volatile organic compounds (VOCs) in waste gas streams. The effects of the influent VOC concentration and the organic loading rate on the VOC removal efficiency and on the pattern of biomass accumulation were investigated. Toluene was used as the model VOC, the flow rate of the waste gas stream was 0.59 L/s, and the empty-bed retention time (EBRT) in the ASP portion was 46 s with an actual retention time of about 2 s. The EBRT in the RDB portion was 38 s based on the drum volume. When the VOC feed concentration increased from 221 to 884 mg toluene/m3 (from 57.2 to 229 ppm), correspondingly the organic loading rate of the hybrid bioreactor increased from 1.58 to 6.32 kg chemical oxygen demand/m3/day (from 0.505 to 2.02kg?toluene/m3/day) based on the drum volume, both the ASP and RDB decreased, and the overall toluene removal efficiency declined from 99.8 to 74.1%. Biomass accumulation at different medium depths became more even when the organic loading rate was increased. Part of the applied VOC was biodegraded by the ASP, which suggests that this hybrid bioreactor could achieve longer runs between medium cleanings and higher VOC removal efficiencies than a single RDB bioreactor without an ASP portion at the same organic loading rate.  相似文献   

6.
The Allen Park Clay Mine Landfill, owned by Ford, produces a leachate that occasionally contains cyanide at levels marginally below the discharge limit. The form of the cyanide in the leachate was found to be iron-cyanide complexes that resist oxidation by a conventional treatment method, alkaline oxidation. Furthermore, the leachate also was found to contain a relatively large amount of organics (>1,000 mg∕L of chemical oxygen demand), which would exert additional demand for oxidizing agents (e.g., chlorine). A study was performed to determine what treatment technology could be employed in the event treatment becomes necessary because of potential changes in the leachate characteristics and∕or discharge limits. In this study, among several chemical oxidation methods, ultraviolet (UV) irradiation with or without ozone was investigated as a treatment option. The following are the primary findings: (1) UV irradiation alone was effective for removing the iron-cyanide complex in both the leachate and the clean water; (2) the demand for UV or ozone by chemical oxygen demand was relatively low for this leachate; (3) ozone alone was not effective for removing the iron-cyanide complex; and (4) UV irradiation alone and UV irradiation with ozone resulted in the same removal for total cyanide in clean-water experiments, but the UV irradiation alone left some free cyanide whereas the UV irradiation with ozone did not.  相似文献   

7.
Among petroleum-hydrocarbon pollutants, fuel-oil is more difficult to treat compared to gasoline and diesel fuel. The objectives of this bench-scale study were to: (1) develop a two-stage remedial system consisting of surfactant washing followed by Fenton-like oxidation process to remediate fuel-oil contaminated soils; (2) evaluate the effects of residual surfactant and soil organic matter (SOM) on the efficiency of Fenton-like oxidation; (3) evaluate the effect of potassium dihydrogen phosphate (KH2PO4) addition on the stability of H2O2 and oxidation efficiency; and (4) evaluate the possible oxidation products after the oxidation process. In the surfactant washing stage, biodegradable surfactant, Simple Green (SG) (50?g?L?1), was applied to flush fuel-oil contaminated soils with initial total petroleum-hydrocarbons (TPHs) concentration of 50,000?mg?kg?1. Results show that approximately 90% of TPH could be removed after washing with 45 pore volumes (PVs) of SG followed by 25 PVs of deionized water, while the soil TPH concentration dropped from 50,000 to 4,950?mg?kg?1. In the Fenton-like oxidation stage with initial soil TPH concentration was approximately 4,950?mg?kg?1, TPH removal efficiency can be significantly increased with increased H2O2 concentrations. Results also reveal that residual SG and SOM would compete with TPH for oxidants and cause the decrease in oxidation efficiency. An “oxidation-sorption-desorption-oxidation” scheme for soil TPH was observed in this experiment due to the initial sorption of TPH on SOM. Results show that an addition of 2.2 mM of KH2PO4 could increase the stability and half-life of H2O2, but caused the decrease in TPH removal efficiency. The oxidation potential of Fenton-like process was not capable of completely oxidizing fuel-oil to nontoxic end products. The observed by-products after oxidation process contained carboxyl groups with molecular weights similar to their parent compounds. Results from this study indicate that the two-stage remedial system is a promising technology for fuel-oil contaminated soil treatment.  相似文献   

8.
The increased use of ethanol as a replacement for the gasoline oxygenate, methyl tert-butyl ether (MTBE), may lead to indirect impacts related to natural attenuation of benzene, toluene, ethylbenzene, and the three isomers of xylene (BTEX compounds). Ethanol could enhance dissolved BTEX mobility by exerting a cosolvent effect that decreases sorption-related retardation. This effect, however, is concentration dependent and was not observed when ethanol was added continuously (at 1%) with BTEX to sterile aquifer columns. Nevertheless, a significant decrease in BTEX retardation was observed with 50% ethanol, suggesting that neat ethanol spills in bulk terminals could facilitate the migration of pre-existing contamination. MTBE (25 mg/L influent) was not degraded in biologically active columns, and it did not affect BTEX degradation. Ethanol (2 g/L influent), on the other hand, was degraded rapidly and exerted a high demand for nutrients and electron acceptors that could otherwise have been used for BTEX degradation. Ethanol also increased the microbial concentration near the column inlet by one order of magnitude relative to columns fed BTEX alone or with MTBE. However, 16S-ribosomal ribonucleic acid sequence analyses of dominant denaturing gradient gel electrophoresis bands identified fewer species that are known to degrade BTEX when ethanol was present. Overall, the preferential degradation of ethanol and the accompanying depletion of oxygen and other electron acceptors hindered BTEX biodegradation, which suggests that ethanol could increase the length of BTEX plumes.  相似文献   

9.
A novel application of ultraviolet (UV) light emitting diodes (LEDs) as a light source for the degradation of organic contaminant has been investigated. Photocleaving of hydrogen peroxide (H2O2) via UV LEDs photolysis resulted in the generation of hydroxyl radicals. It was found that phenol removal was insignificant in the absence of hydrogen peroxide, therefore oxidation of phenol was attributed to the formed radicals. Two criteria were selected to provide detailed information on the performance of UV LEDs in phenol oxidation: (1) the reaction quantum efficiency and (2) the energy consumption. Statistical tools such as the response surface methodology and the ANOVA were applied to estimate the influence of various process parameters such as the wavelength (255, 269, and 276 nm) and H2O2 to phenol molar ratio (5, 50, and 100) on phenol degradation reaction quantum efficiency. The decay of phenol (initial concentration of 1.06 mM) was the most pronounced at 255 nm and H2O2 to phenol molar ratio of 50. Finally, the “figure-of-merit” was used to estimate the specific energy consumption of the UV LED-based process.  相似文献   

10.
Ozone and electrochemical oxidation treatment technologies were evaluated for wastewater recycling in the textile industry. Textile wastewater was collected from eight textile mills that use different dying processes. Both ozone and electrochemical oxidation removed the color from wastewater containing acid, reactive, and natural dyes, while mixed results were achieved with pigment and disperse dyes. The variability in color removal for the pigment and disperse dyes may be related to the concentration and type of auxiliary chemicals used. Color criteria for reusing wastewater for reactive dye was determined to be ΔE ? 2. This level of treatment provided an acceptable level of residual color for reuse in dark color dyeing operations and for rinse water. Some reformulation of the dye concentration and auxiliary chemicals is necessary for wastewater reuse in light color dyeing operations. Also, multiple reuse of the treated wastewater, as would occur in a completely closed system, would require changes in salt and other auxiliary chemicals to achieve the same fabric color as clean process water.  相似文献   

11.
This study investigates the aqueous degradation of four iodinated x-ray contrast media (ICM) compounds (diatrizoate, iomeprol, iopromide, and iopamidol) by ozone and combined ozone and hydrogen peroxide. In laboratory scale experiments, second-order kinetic rate constants for the reactions of the ICM compounds with molecular ozone and hydroxyl radicals, and overall at pH 7.5, were determined. For the four ICM compounds the degradation rate constants with molecular ozone were low and in the range of 1–20?M?1?s?1, whereas the rate constants with hydroxyl radicals were in the range of 1×109–3×109?M?1?s?1. Diatrizoate had the lowest rate constant of the four compounds with respect to molecular ozone reactions. At pH 7.5, the extent of compound degradation was proportional to the applied ozone dose and inversely related to the initial compound concentration at a given ozone dose. At this pH approximately 90% of the degradation could be attributed to hydroxyl radical reactions. Enhancement of the radical mechanism by the addition of hydrogen peroxide during ozonation led to complete removal of the nonionic compounds, and >80% removal of diatrizoate, at relatively low oxidant mass ratios (H2O2/O3<0.25). A similar enhancement in compound degradation was evident with the presence of small concentrations of humic substances ( ~ 4–5?mg?L?1). Ozone oxidation led to major cleavage of the ICM compounds and the release of inorganic iodine; the proportion of iodine release was similar among the nonionic ICM compounds but much greater for diatrizoate.  相似文献   

12.
建立了烟气发生模拟试验装置,采用紫外光在较低温度下激发H2O2产生的活性基团对烟气中的NO进行氧化脱除。研究了H2O2浓度、H2O2温度、NO初始浓度、O2浓度、金属离子催化剂和烟气流量等因素对系统NO脱除效果的不同影响,并通过正交试验得出了该体系的最佳工艺条件。对该条件下的反应产物分析发现,反应后溶液中主要为NO-3,NO-2,Fe3+和过量的H2O2。正交试验证明,该体系NO最大脱除率可达到88.6%,高于其他工艺的脱除效率,具有工程应用价值。  相似文献   

13.
Although biofiltration has been used successfully to remove and biodegrade a wide variety of gas-phase organic contaminants generated by industrial facilities and environmental remediation efforts, the ability of conventional biofilters to maintain high removal efficiency during short-term, unsteady-state, elevated loading conditions is limited. A promising alternative for improving biofilter performance during transient elevated loading conditions while minimizing the disadvantages of conventional treatment technologies is utilization of adsorption packing media and implementation of sequencing batch operating strategies. In the studies described herein, a continuous-flow biofilter (CFB) and a sequencing batch biofilter (SBB) were operated for more than 300 days to treat a methyl ethyl ketone (MEK) contaminated gas stream. The packing medium for both biofilters consisted of activated carbon coated polyurethane foam cubes. Both biofilters exhibited stable long-term performance with greater than 99% removal of the influent 106?ppmv MEK concentration during “normal” loading conditions. To assess performance during transient loading conditions, on a regular basis the influent MEK concentration of each biofilter was temporarily increased by a factor of 10 to 1,060?ppmv MEK for a duration of either 45 or 60 min. Results are presented which demonstrate how the operational flexibility of SBB systems can be utilized to minimize or eliminate contaminant emissions from biofilters during unsteady-state loading conditions. The SBB was able to remove more than 99% of the influent MEK at a transient loading rate of 380?g?m?3?h?1 and 83% of the influent MEK at a transient loading rate of 760?g?m?3?h?1. In comparison, the CFB exhibited lower MEK removal efficiency.  相似文献   

14.
Intrinsic biodegradation of methyl tert-butyl ether (MTBE) in aquifer sediments under oxic conditions was investigated using laboratory microcosms. Aquifer samples were collected from three different areas (source area, upgradient, and downgradient) of a shallow gasoline-contaminated aquifer within the Atlantic Coastal Plain Province located in Virginia. Biodegradation of MTBE was observed in the source-area microcosms in which MTBE declined from a starting concentration of 2.7 to 0.28 mg/L over a 58-day period, following an initial lag period of 20 days. The same set of microcosms was respiked with MTBE to an initial concentration of 4.8 mg/L and MTBE concentrations declined to 0.20 mg/L over a 52-day period with no lag in biodegradation. First-order MTBE biodegradation rates for the first and second periods were 0.037±0.003 and 0.063±0.003 day?1, respectively. When another set of source-area microcosms was spiked with MTBE (5 mg/L), toluene and ethylbenzene (1 mg/L each), the initial lag period increased to 33 days but there was no significant change in the MTBE biodegradation rate (0.065±0.026 day?1) and MTBE was not detected after 134 days. Biodegradation of MTBE was also observed in the microcosms constructed using aquifer sediment with only limited exposure to MTBE but the degradation rate was lower and statistically different (0.022±0.005 day?1) than the source area microcosms. Biodegradation of MTBE ceased when oxygen was depleted. Methyl tert-butyl ether did not biodegrade in the uncontaminated, upgradient microcosms; however, rapid biodegradation of toluene was observed. Methyl tert-butyl ether biodegradation appears to be limited in the absence of dissolved oxygen and in aquifer sediments where petroleum hydrocarbons including MTBE were not previously observed.  相似文献   

15.
氧化锌法脱除低浓度二氧化硫过程中副产物亚硫酸锌的氧化回收利用是影响脱硫工艺发展的重要步骤,同时也是解决脱硫系统设备管道结垢堵塞问题的关键,文中提出利用臭氧强化氧化亚硫酸锌生成可溶性硫酸锌的新方法。研究了亚硫酸锌初始含量、搅拌转速、臭氧流量、溶液初始pH以及温度对臭氧氧化亚硫酸锌的影响。结果表明氧化过程中溶液的pH先升高后降低,溶液中锌离子浓度随氧化时间的增加而增加。亚硫酸锌臭氧氧化速率随初始亚硫酸锌含量的增加先增加后降低,随搅拌转速的增加而增大,随臭氧流量的增加先增加后减小,随溶液初始pH的增加而增加,温度对氧化速率的影响较小。研究结果为氧化锌法高效脱硫及副产物的回收利用提供了理论基础。   相似文献   

16.
Cell immobilized lipase-producing bacteria on three different matrices were incorporated in a fat-, oil-, and grease (FOG) trap system for restaurant wastewater treatment. During a 16-day laboratory-scale experiment for the treatment of synthetic FOG wastewater containing soybean oil, no significant difference (two-tailed t test at 95% confidence interval) in the FOG removal between two systems was observed at FOG influent ≤ 1,000?mg/L. However, the typical trap showed lower FOG removal efficiency than the matrix-based system when the influent FOG concentration was increased to ≥ 5,000?mg/L. In addition, the matrix-based trap system was able to sustain a stable high FOG removal, with <100?mg/L effluent, even at 10,000 mg/L influent FOG. Based on FOG heights measured and mass balance calculations, 97.4 and 99.5% of the total FOG load for 16 days were removed in a typical trap and matrix-based system, respectively. About 93.6% of the removal in the matrix-based was accounted to biodegradation. The 30-day full-scale operations demonstrated a distinguishably better performance in the matrix-based system (92.7±9.06% of 1,044.8±537.27?mg FOG/L) than in the typical trap system (74.6±27.13% of 463.4±296.87?mg FOG/L) for the treatment of barbeque restaurant wastewater. Similarly, matrix-based system revealed higher chemical oxygen demand removal (85.9±11.99%) than the typical trap system (60.4±31.26%). Characterizations of the influent, emulsified, adsorbed and effluent FOG indicated that straight saturated fatty acids constituted the cause of clogging problems in the FOG-trap and piping system.  相似文献   

17.
The purpose of this study is to develop a kinetic model that links O3 decomposition reactions from the TFG ozone decay model with recognized Br? oxidation reactions, secondary ?OH reactions, and H2O2 reactions in order to improve O3 decay and bromate formation prediction capabilities under multiple water quality conditions. The model was compared with experimentally measured ozone decomposition and final bromate concentration data sets provided by two researchers. The data sets included varying pH (6.5–8.5), initial hydrogen peroxide (0–1 mM), and initial bromide concentration (0.1–1 mM). Model verification was carried out by sensitivity analysis of the rate constants and then optimization of the most sensitive rate constants using the method of least squares. Model predicted ozone decay data was analyzed and compared with measured ozone decay data using R-squared statistic for linear regression model. The model predicted final bromate concentration is analyzed by comparing it with the residual Δ(%) between experimental and model results. The TFG model was effectively tested for multiple data sets and it was found that model prediction was a success both for ozone decay (regression coefficients >0.95 for all experimental conditions but one) and bromate prediction with residual of less than 100% for all experimental conditions except low peroxide dose (<20 μm).  相似文献   

18.
杨义  邱陆明  刘海霞  刘金凤 《黄金》2020,41(4):75-78
根据某金精矿冶炼厂氰化尾矿浆中氰化物质量浓度较高的特点,开展综合处理试验研究。采用3R-O法、Colt’s法和臭氧氧化法组合工艺回收处理氰化尾矿浆中的氰化物和SCN-,并对试验条件进行了优化。试验结果表明:氰化尾矿浆中的总氰化合物质量浓度降至2. 86 mg/L,去除率达99. 82%,SCN-质量浓度降至2. 04 mg/L,去除率达99. 95%,压滤液可回用到氰化浸出工艺;处理后的氰渣达到了HJ 943—2018 《黄金行业氰渣污染控制技术规范》尾矿库处置标准要求,可实现尾矿库堆存。该研究为氰化尾矿浆无害化处理工程化应用提供数据参考。  相似文献   

19.
Advanced oxidation of simazine in aqueous solution by the peroxone (hydrogen peroxide/ozone) treatment was investigated using Box-Behnken statistical experiment design and response surface methodology. Effects of pH, simazine and H2O2 concentrations on percent simazine and total organic carbon (TOC) removals were investigated. Ozone concentration was kept constant at 45?mg?L?1. The optimum conditions yielding the highest simazine and TOC removals were also determined. Both simazine and peroxide doses affected simazine removal while pH and pesticide dose had more pronounced effect on mineralization (TOC removal) of simazine. Nearly 95% removal of simazine was achieved within 5 min for simazine and peroxide concentrations of 2.0 and 75?mg?L?1, respectively at pH = 7. However, mineralization of simazine was not completed even after 60 min at simazine doses above 2?mg?L?1 indicating formation of some intermediate compounds. The optimum H2O2/pH/Simazine ratio resulting in maximum pesticide (94%) and TOC removal (82%) was found to be 75/11/0.5(mg?L?1).  相似文献   

20.
This paper deals with the removal of copper ions from aqueous solutions by using surfactant-enhanced powdered activated carbon (PAC)/microfiltration (MF) hybrid process, including the evaluation of process performance and fouling dynamics at various linear alkyl benzene sulfonate (LABS), PAC, and Cu2+ concentrations of feed solution. Although the use of surfactant as an additive material increased the adsorption efficiency in PAC/MF hybrid process, a considerable amount of the flux was lost for surfactant concentration above critical micelle concentration. The process could be employed with a performance of 74.7%, 97.2% and 87?L/m2?h for LABS rejection, Cu2+ rejection and permeate flux at the conditions of 2?g PAC/L, 5?mM LABS, 0.2?mM Cu2+, and 60-min process time. Cu2+ rejection, which increased with increasing of LABS, and PAC amounts decreased with the increase in Cu2+ concentration. It was understood that the increments in LABS, PAC, and Cu2+ concentrations being an indicator for the feed solution quality led to the occurrence of more fouling on the membrane. The analyses of dynamics concerning the fouling behaviors, which were carried out using single and combined pore blocking models, put forward that the cake formation was the main predominant mechanism in the process. It was also determined that the variation of feed contents deduced the presence of rather complex fouling behaviors as a simultaneous function of secondary membrane layer formation and clogging and narrowing of membrane pores by surfactants.  相似文献   

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