摘要:

Potential mechanisms for stimulating anaerobic benzene degradation in methanogenic sediments from a petroleum‐contaminated aquifer were evaluated. In short‐term (<2 weeks) incubations, addition of sulfate slightly stimulated benzene degradation and caused a small decrease in the ratio of methane to carbon dioxide production from benzene. However, in longer‐term (>100 days) incubations, sulfate significantly stimulated benzene degradation with a complete shift to carbon dioxide as the end product of benzene degradation. The addition of Fe(III) and humic substances had short‐term and long‐term effects that were similar to the effects of the sulfate amendments. In studies in which anaerobic groundwater was pumped through columns of aquifer sediments, addition of sulfate to the groundwater significantly enhanced the removal of benzene from the groundwater. The stoichiometry of sulfate and benzene removal from the groundwater passing through the sediment columns was consistent with benzene oxidation to carbon dioxide with sulfate serving as the primary electron acceptor. These results demonstrate for the first time that addition of sulfate may be an effective strategy for enhancing anaerobic benzene removal in some petroleum‐contaminated aquifers.

ISSN:1088-9868    

DOI:10.1080/10889869809380374

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

An anaerobic culture reductively transformed trichloroethene (TCE) in an aqueous medium containing elemental iron as the sole electron source. The TCE disappearance rate was enhanced and the product distribution was markedly altered when the culture was present. In abiotic samples containing Fe(0) but no culture, 11 μmol TCE (equivalent to an aqueous concentration of 260 μM) disappeared over a period of 39 days, with ethene and ethane as the major reduction products. Small amounts ofcis‐dichloroethene (cis‐DCE),1,1‐DCE, and vinyl chloride (VC) also were detected. When the culture was incubated with TCE and Fe(0), the same amount of TCE was transformed in less than 2 weeks. The major products after 39 days were VC, ethene, and ethane. VC accounted for 65% of the initial TCE and appeared to be reduced further to ethene at slow rates. The significant VC production in the culture‐amended samples indicates that most TCE was transformed microbially rather than chemically. The data indicate that abiotic and biological reduction of chlorinated ethenes can be coupled to enhance treatment efficiency. The results also suggest that microbial dechlorination within and downgradient from iron walls is potentially important for evaluating the long‐term performance of permeable iron barriers.

ISSN:1088-9868    

DOI:10.1080/10889869809380375

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A bioremediation process was developed using the fungusAspergiUus nigerto produce weak organic acids for the leaching of heavy metals from contaminated soils. The fungus was cultivated on the surface of three contaminated soils (a clay loam, a loam, and a sandy clay loam) for 15 days at 30°C and at a pH <4 to favor the production of citric acid rather than oxalic acid which hinders Pb leaching. For the clay loam, Cr, Mn, Pb, and Hg were leached to levels of 37, 41, 85, and 91%, respectively. For the loam, the leaching of Cd and Pb was found to reach levels of 99.7 and 83%, respectively. For the sandy clay loam, Cd, Cu, Pb, and Zn were leached to levels of 99,94,58, and 99%, respectively. The three contaminated soils could have been remediated to the A category of the Province of Quebec standards for heavy metals after 20 to 25 days of leaching using this technique.

ISSN:1088-9868    

DOI:10.1080/10889869809380376

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

HT is a powerful vesicant produced for use as a chemical warfare agent. It is a mixture of 60 wt % 2,2'‐dichlorodiethyl sulfide ("HD”; or “sulfur mustard") and 40 wt %bis‐(2‐(2‐chloroethylthio)ethyl) ether (T). Because HT reacts with water to form primarily the alcoholic compounds thiodiglyçol (TDG) andbis‐(2‐(2‐hydroxyethylthio)ethyl) ether (T‐OH), disposal might be accomplished by combining hydrolysis with biodegradation. The half‐lives of H and T in a well‐agitated 3.8% HT/water reaction at 90°C were 1.4 and 1.6 minutes, respectively. The concentrations of both compounds were reduced to less than 1 mg/L within about 30 minutes. TDG is readily biodegradable. However, T‐OH biodegradability has not been reported previously. HBr treatment converted HT ether‐alcohol products to TDG. A comparative study of two hydrolysis/biodegradation approaches is reported here. HT was hydrolyzed (1) in water, and (2) in water then with HBr. Products were used as feed for separate aerobic sequencing batch reactors (SBRs), and bioreactor performances were compared. Although both feed solutions were detoxified in the SBRs, water hydrolysis alone yielded better overall bioreactor operation, a more favorable mass balance, and a simpler process than with the HBr step. Results indicated that although the HBr converted ether‐alcohol products to TDG, the HT products were biodegraded with greater efficiency when the HBr treatment was omitted.

ISSN:1088-9868    

DOI:10.1080/10889869809380377

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The soil bacteriumBacillus polymyxais shown to effectively remove organic flotation collectors such as dodecyl amine, diamine, sodium isopropyl xanthate, and sodium oleate from alkaline solutions. Adsorption and bacterial growth studies indicated enhanced surface affinity of the amine collectors toward the bacterial cells. All the above organic reagents could be efficiently removed from alkaline solutions through bacterial interaction. Ultraviolet (UV)‐visible and Fourier transform infrared (FTIR) spectra during biodégradation of these reagents revealed the stages in biodegradation. Possible mechanisms are outlined.

ISSN:1088-9868    

DOI:10.1080/10889869809380378

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:1088-9868    

DOI:10.1080/10889869809380379

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Since the late 1980s, more than half of all known underground storage tanks (USTs) in the United States have been closed. Many of these tanks are known to have leaked, and new releases are still being reported. Correcting the resulting soil and groundwater contamination has turned out to be an expensive undertaking. In response, regulators and other interested parties have worked together to adopt risk‐based approaches to setting cleanup goals and to promote innovative cleanup technologies such as natural attenuation. These changes have dramatically affected the way in which leaking USTs are regulated and cleaned up.

ISSN:1088-9868    

DOI:10.1080/10889869809380380

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Remediation goals for the source areas of a chlorinated ethene‐contaminated groundwater plume were identified by assessing the natural attenuation capacity of the aquifer system. The redox chemistry of the site indicates that sulfate‐reducing (H2∼ 2 nanomoles [nM]) per liter conditions near the contaminant source grade to Fe(III)‐reducing conditions (H2∼ 0.5 nM) downgradient of the source. Sulfate‐reducing conditions facilitate the initial reduction of perchloroethene (PCE) to trichloroethene (TCE),cis‐dichloroethene (cis‐DCE), and vinyl chloride (VC). Subsequently, the Fe(III)‐reducing conditions drive the oxidation ofcis‐DCE and VC to carbon dioxide and chloride. This sequence gives the aquifer a substantial capacity for biodegrading chlorinated ethenes. Natural attenuation capacity (the slope of the steady‐state contaminant concentration profile along a groundwater flowpath) is a function of biodegradation rates, aquifer dispersive characteristics, and groundwater flow velocity. The natural attenuation capacity at the Kings Bay, Georgia site was assessed by estimating groundwater flowrates (∼0.23 ± 0.12 m/d) and aquifer dispersivity (∼1 m) from hydrologic and scale considerations. Apparent biodegradation rate constants (PCE and TCE ∼ 0.01 d−1;cis‐DCE and VC ∼ 0.025 d−1) were estimated from observed contaminant concentration changes along aquifer flowpaths. A boundary‐value problem approach was used to estimate levels to which contaminant concentrations in the source areas must be lowered (by engineered removal), or groundwater flow velocities lowered (by pumping) for the natural attenuation capacity to achieve maximum concentration limits (MCLs) prior to reaching a predetermined regulatory point of compliance.

ISSN:1088-9868    

DOI:10.1080/10889869809380381

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Natural attenuation of benzene and dichloroethanes in groundwater contaminated by leachate from the West KL Avenue landfill in Kalamazoo, Michigan, was evaluated in three phases. Existing data from the previous site investigations were used to locate a series of high‐resolution vertical profile samples. By analyzing data from the discrete vertical profile samples, the rates of attenuation of benzene and dichloroethanes in the plume were forecasted. Permanent monitoring wells were installed over the depth intervals associated with high concentrations in the vertical profile sampling. These wells were monitored over time to extract independent estimates of the rates of degradation of benzene and dichloroethanes. Estimates of first‐order attenuation rate constants were obtained using two methods: a method due to Buscheck and Alcantar (1995), which is based on a one‐dimensional steady‐state analytical solution, and the tracer correction method of Wiedemeier et al. (1996). The rates of attenuation predicted from the vertical profile sampling were found to be in good agreement with the rates obtained from the permanent monitoring well data, indicating that the long‐term behavior of the contaminant plumes is consistent with the initial forecast. The results also indicated that the natural attenuation of benzene, 1,1‐dichloroethane (DCA), and 1,2‐DCA was statistically significant (at the 0.05 level).

ISSN:1088-9868    

DOI:10.1080/10889869809380382

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Based on electron acceptor abundance, Fe3+and SO2−4reduction by bacteria may play a dominant role in intrinsic bioremediation of some organic contaminants in the subsurface. Both Fe3+and SO2−4reduction processes involve mineral phases and may not be properly understood by evaluating only groundwater concentrations. Fe and S mineral analyses should be incorporated in natural attenuation studies; however, inherent problems with sample collection and analysis have discouraged such efforts. Methods are presented here for (1) sediment collection and anoxic preservation, (2) evaluation of biologically available Fe3+and biogenically produced Fe2+minerals, and (3) a simplified extended mineral sulfide analysis for ‐FeS and S°+FeS2. These techniques are demonstrated to evaluate Fe3+and SO2−4reduction at three sites where the soil or aquifer matrix had been contaminated with gasoline fuel, methane gas, or landfill leachate. It is expected that these techniques will permit Fe and S mineral analyses to become a routine part of natural attenuation assessments.

ISSN:1088-9868    

DOI:10.1080/10889869809380383

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor