For sites contaminated with chloroethene non-aqueousphase liquids, designing a remediation system that couples in situ chemical oxidation (ISCO) with potassium permanganate (KMnO4) and microbial dechlorination may be complicated because of the potentially adverse effects of ISCO on anaerobic bioremediation processes. Therefore, one-dimensional column studies were conducted to understand the effect of permanganate oxidation on tetrachloroethene (PCE) dechlorination by the anaerobic mixed culture KB-1. Following the confirmation of PCE dechlorination, KMnO4 was applied to all columns at a range of concentrations and application velocities to simulate varied distances from oxidant injection. Immediately following oxidation, reductive dechlorination was inhibited; however, after passing several pore volumes of sterile growth medium through the columns after oxidation, a rebound of PCE dechlorination activity was observed in every inoculated column without the need to reinoculate. The volume of medium required for a rebound of dechlorination activity differed from 1.1 to 8.1 pore volumes (at a groundwater velocity of 4 cm/d), depending on the specific condition of oxidant application.

East Fork Poplar Creek (EFPC) in Oak Ridge, TN was highly contaminated with elemental mercury in the 1950 and 1960. The area is still experiencing the effects of mercury contamination, and researchers are searching for ways to remediate the EFPC. One possible mechanism for bioremediation is the use of biogenic Mn oxides to remove heavy metals from water systems. Native Pseudomonas bacteria species were isolated from EFPC in order to examine biogenic Mn oxides production and bioremediation of Oak Ridge slurries. Pseudomonas isolates did produce Mn oxides which bound to mercury, and mercury bound to organic matter significantly decreased. However, after a significant decrease of dissolved mercury, dissolved mercury was cycled back into the water system on day 10. Given a longer experimental timeline, biogenic Mn oxides have the potential to decrease mercury cycling.

No description available.

No description available.

Three major microbial subpopulations from an industrial leachate system were characterized with respect to their bioremediation potential, and particular aspects of a cometabolically active subpopulation were determined.

Remediation of weathered petroleum hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), dioxins, and polychlorinated biphenyls (PCBs) through monitored natural attenuation, in-situ biostimulation, and/or bioaugmentation was assessed using laboratory-scale microcosms. These contaminants of interest (COIs) have persisted in Santa Susana Field Laboratory (SSFL) soils for over 40 years in some cases. The objective of this United States Department of Energy (DOE)-funded study was to determine the potential of the aforementioned remediation methods to reduce COI concentrations in soil and estimate potential biodegradation rates of COIs in SSFL soils. Several types of soil microcosms were established: one set of microcosms was run without amendments to estimate natural attenuation rates at the site; biostimulation was tested by addition of nitrogen and phosphorus, rice hulls, and biosurfactant (soya lecithin), another set was augmented with the white-rot fungus Phanerochaete chrysosporium, and gamma-irradiated microcosms served as sterilized controls. Soil samples were collected and analyzed for dioxins, PCBs, PAHs, and extractable fuel hydrocarbons (EFH) after 0, 4, and 8 months of incubation. Soil contamination in the microcosms initially consisted of primarily heavily chlorinated dioxins and PCBs, longer petroleum hydrocarbons (21-40 equivalent carbon chain length), and PAHs with 4-6 aromatic rings. Small decreases in PAH, PCB, and dioxin soil concentrations were observed, but these decreases were not statistically significant. EFH concentrations were inflated at the final sampling event, but they appeared to reduce for two of three soils (Soils A and C) tested at the second sampling event. No COI concentration reductions were statistically significantly during 8 months of incubation. Because petroleum hydrocarbons were primarily longer-chain hydrocarbons in the C21 to C40 EFH range, it is likely that lighter hydrocarbons had been preferentially degraded, leaving the more recalcitrant longer-chain hydrocarbons in the soil. Dioxin concentrations appeared to decrease in some cases, but these reductions were not statistically significant at the 95% confidence level. Larger PAHs (4-6 rings) comprise the majority of residual PAH soil contamination. Given that concentrations of these PAHs have not decreased significantly during this 8-month long study, it is likely that these larger PAH contaminants are somewhat recalcitrant and will take a long time to biodegrade. Similarly, little or no PCB biodegradation was observed which is not surprising because the PCBs are heavily chlorinated, and bacterial biodegradation of these highly chlorinated compounds is reported to occur only under anaerobic conditions. The primary dioxin congener present in soils was octachlorodibenzodioxin (OCDD), which is the heaviest-chlorinated dioxin congener. Like PCBs, this compound requires anaerobic conditions for reductive dechlorination, and these are not present at the site. Total dioxin concentrations decreased in the microcosms amended with Phanerochaete chrysosporium, although this decrease was not statistically significant due to variability of dioxin concentrations measured in the soil. No decrease in tetrachlorodibenzodioxin toxicity equivalence was observed with P. chrysosporium bioaugmentation, and this parameter is important in terms of dioxin toxicity. Soil vapor analyses performed at the site indicate highly aerobic soil conditions. To mimic site conditions as closely as possible, experimental microcosms were maintained incubated in aerobic conditions. Although fungi have been reported to degrade PCBs and dioxins under aerobic conditions, the microcosms augmented with Phanerochaete chrysosporium did not show statistically significant biodegradation of PCBs. Contaminant sequestration in the soil may also have contributed to the lack of observed biodegradation because the COIs at this site are highly weathered. However, even microcosms augmented with a surfactant (soya lecithin), which would be expected to solubilize sequestered COIs, did not show significant biodegradation.

A process for disposing of pesticide rinsewater generated from the rinsing of application equipment is being developed at Virginia Polytechnic Institute and State University. This process involves the sorption of pesticides onto an organic matrix followed by degradation in a composting environment. We are now evaluating the hazards that might be associated with land-applying composted pesticide waste. Diazinon was the first pesticide selected for evaluation, which consisted of two studies. The first used the earthworm species Eisenia foetida to evaluate the toxicity of soil amended with composted diazinon waste. The second study determined the bioavailability of delta-2-14C-diazinon and its degradation products to E. foetida in soil amended with composted delta-2-14C-diazinon. Results from the first study indicate that uncomposted diazinon sorbent and 30-day composted diazinon sorbent were toxic to E. foetida at sublethal and lethal levels. However, E. foetida exposed 60-day composted diazinon sorbent did not experience mortality or demostrate sublethal effects commonly associated with acetylcholinesterase inhibition. Earthworms exposed to diazinon that was uncomposted or composted for 30 days in the radiolabelled study experienced higher mortality than in the field study. After 30 and 60 days of composting 14C-diazinon became unextractably incorporated into organic matter and very little was mineralized. Earthworms were shown to accumulate radioactivity when exposed to soil amended with 60- day composted delta-2-14C-diazinon. The majority of this radioactivity was unextractably bound to earthworm tissue and that which was extractable contained only trace levels of delta-2-14C-diazinon. Based on the absence of toxicity in the field study and the low levels of 14C-diazinon present in earthworm tissues, 60 days of composting appears to greatly reduce the hazard that diazinon rinsate poses to E. foetida. / Master of Science

This study evaluates the effectiveness of molasses injection for reducing heavy metals and chlorinated solvents in a ground water plume at the Avco-Lycoming Superfund site in Williamsport, Pennsylvania. Molasses injection stimulates the respiration of microorganisms to make a more reducing environment. As the environment?s Redox potential decreases, the rate of chemical reduction increases. The concentrations of heavy metals and chlorinated solvents were monitored to evaluate the effectiveness of the molasses injection. The statistics revealed a decrease in the Oxidation-Reduction Potential in the groundwater and a reduction in hexavalent chromium and TCE concentrations in the groundwater. The Environmental Protection Agency views molasses injection as a viable technique for site remediation. Molasses injection is a form of facilitated natural attenuation. Molasses is injected into a plume to make the environment anaerobic. An anaerobic environment facilitates the microbes that breakdown trichloroethylene (TCE), trans-dichloroethylene (DCE), vinyl chloride (VC) and hexavalent chromium.

No description available.

No description available.