Le couplage d’un traitement électrochimique avec un procédé biologique est une alternative prometteuse pour la dégradation de composés organo-halogénés biorécalcitrants dans l’environnement. Les procédés d’électroréduction, connus pour couper sélectivement la liaison carbone-halogène, ont été mis en oeuvre afin de réduire la toxicité des molécules cibles et augmenter leur biodégradabilité avant une minéralisation totale des polluants par un traitement biologique. Pour améliorer le rendement de déchloration, la cathode préalablement nickelée a été modifiée par des nanoparticules d’argent car l’argent est considéré comme l’un des meilleurs catalyseurs pour couper sélectivement la liaison carbonehalogène. Le feutre de graphite a été choisi comme support d’électrode pour sa grande surface spécifique. Le principal produit de déchloration de l’alachlor s’est révélé être biorécalcitrant. Pour surmonter ce problème, un traitement par procédé électro-Fenton a été mis en oeuvre pour dégrader les polluants cibles. Une amélioration significative de la biodégradabilité de la solution d’alachlor a pu être observée après le traitement électro- Fenton, et qui est renforcée quand l’atome de chlore a été préalablement éliminé de la structure de l’alachlor par électroréduction. Le bismuth a été également utilisé comme support d’électrode du fait de sa grande surtension visà- vis de la réduction de l’eau. Une grande sélectivité a pu être obtenue sur cathode de bismuth lors de la réduction d’herbicides du type chloracétamide. La réduction électrochimique du dioxyde de carbone a également été réalisée sur électrode de bismuth modifiée par des nanoparticules d’argent comme autre application de cette nouvelle électrode. / Electrochemical process coupling with a biological treatment is a promising alternative for the degradation of biorecalcitrant organo-halogenated compounds in the environment. The electroreduction treatment, known to cut selectively carbon-halogen bonds, was first implemented to decrease the toxicity of the target molecules and increase their biodegradability before a complete mineralization of the pollutants by a biological treatment. To improve the dechlorination efficiency, the cathode was modified by silver nanoparticles after a previous nickelisation, since silver is considered as one of the best electrocatalysts to selectively cleave the carbonhalogen bond. The graphite felt was chosen as the electrode support due to its high specific surface area. For alachlor herbicide, deschloroalachlor, the main by-product after dechlorination, was still biorecalcitrant. To overcome this issue, electro-Fenton treatment, in which hydroxyl radicals were generated to degrade the target pollutants, was implemented. Significant improvement of biodegradability of the alachlor solution was observed after electro-Fenton treatment, which was further improved when the chlorine atom was beforehand removed from the alachlor structure by the electroreduction process. Bismuth was also used as electrode support due to its high overpotential for hydrogen evolution. A high selectivity of chloroacetamide herbicides reduction was observed on the bismuth based cathode. As an extended application of the bismuth based cathode, the electrochemical reduction of carbon dioxide was performed on Bi electrode modified by silver nanoparticles.

Arsenic (As), a known carcinogen, is a groundwater contaminant in many parts of the world. Arsenic contamination is enhanced through carbon addition, such as biostimulation, a remediation process, which has been used to remove trichloroethylene (TCE) from sediment and groundwater. Two studies were designed to evaluate the effect of different carbon sources on the removal of TCE through dechlorination and on As solubilization and mobilization in response to carbon addition. The first set of columns (15.2 cm diameter, 183 cm long) used whey, Newman Zone® standard surfactant emulsified oil, Newman Zone® nonionic surfactant emulsified oil, and no carbon controls as carbon and energy sources and were fed for 7.5 years. The second set (7.62 cm diameter and length) used whey, lactate, and no carbon control as carbon sources with columns being dismantled and analyzed over a 5-month time period. These studies showed that reducing conditions, caused by the carbon sources, was the driving force for As mobilization as As(V) was reduced to the more mobile As(III). Total As mass in the sediment was lost with all carbon treatments within the first study with whey having a greater loss; however, within the second study, both whey and lactate treatments had the same extent of As mass loss over time. The results also indicated that some As could be attenuating with carbonates or other highly soluble minerals.

No description available.

Microcosms were constructed from aquifer sediment samples taken from an actively degrading chlorinated solvent contaminated site located in Virginia Beach, Virginia. The objective of this study was to determine if and how the addition of cyclodextrin (CD) affects reductive dechlorination of chlorinated ethenes. After chlorinated solvent degradation rates were established in anaerobic and aerobic microcosms, 100 mg/L of CD solution was added for a period of 21 days. CD was then removed after 26 days to simulate the degradation response of the aquifer in a post CD injection environment. Degradation rates were determined by analyzing PCE, TCE, and cis-DCE concentration data over the various phases of the experiment. Results from this study indicated that chlorinated solvent degradation could be either impaired or facilitated by the addition of CD. CD appeared to stimulate one anaerobic microcosm (IY-2c) where daughter production had not previously occurred. The activity of this microcosm was greatly enhanced by the addition of CD (0 uM/day to 13.89 uM/day). However, biotransformation of PCE in another anaerobic microcosm in which reductive dechlorination was occurring, ceased after the addition of CD (IY-1a). In a third group of microcosms the rate and extent of reductive dechlorination was greatly enhanced by the addition of CD. The effect of adding CD was also found to be highly dependent on the redox conditions in the microcosm, specifically if the conditions were strongly reducing. The most active microcosms, found in the Aerobic Group, also had the lowest ferrous iron concentrations (3.57 mg/L for BY-1a, 2.25 mg/L for BY-1b, and 0.41 mg/L for BY-1c). The microcosm (IY-2b) that showed no daughter production had the highest level of ferrous iron (44.22 mg/L). This study presents a qualitative approach to the affect of CD on MNA. / Master of Science

Laboratory microcosm experiments were conducted to assess the potential for biostimulation and bioaugmentation as source reduction measures in support of a monitored natural attenuation remedial strategy at Naval Amphibious Base (NAB) Little Creek. Previous work with laboratory microcosms conducted under simulated natural (unamended) conditions has demonstrated that indigenous dehalorespirators were capable of partial dechlorination of tetrachloroethene (PCE) to cis-dichloroethene (cis-DCE). This study attempts to achieve complete reductive dechlorination with amendments to static microcosms to test the hypotheses that nutrient-limited or microorganism-limited conditions exist in aquifer sediments obtained from the site. The enhanced bioremediation experiments were comprised of nutrient-amended microcosms receiving additions of electron donors, mineral medium, or anaerobic digester supernatant, and dechlorinating culture-amended microcosms were inoculated with a culture capable of transforming PCE to ethene. Reductive dechlorination in the nutrient-amended microcosms proceeded to cis-DCE over a 260-day study period, at slightly higher rates than in experiments conducted with aquifer sediments from the same location under natural conditions. Inoculation of aquifer sediments with a small amount of dechlorinating culture initiated rapid transformation of PCE to vinyl chloride (VC) by day 18 of the study. Zero-order rates of PCE dechlorination in unamended, propionate-, formate-, mineral medium-, digester supernatant-, and dechlorinating culture-amended microcosms were 0.24, 0.750, 1.30, 0.339, 0.177, and 1.75 µM/day, respectively. The results of this study suggest that an engineered biostimulation approach alone may not be as beneficial for PCE source reduction at NAB Little Creek, than bioaugmentation with competent dehalorespirators, along with the inclusion of supplemental nutrients which would be available to stimulate dechlorination activity of both indigenous and introduced microorganisms. / Master of Science

No description available.

The entire stretch of the Ohio River is under fish consumption advisories due to contamination with polychlorinated biphenyls (PCBs). In this study, natural attenuation and biostimulation of PCBs and microbial communities responsible for PCB transformations were investigated in Ohio River sediments. Natural attenuation of PCBs was negligible in sediments, which was likely attributed to low temperature conditions during most of the year, as well as low amounts of available nitrogen, phosphorus, and organic carbon. Moreover, surface sediments were relatively oxidized, as indicated by the prevalence of aerobic bacteria such as beta- Proteobacteria, alpha-Proteobacteria, Sphingobacteria, and Nitrospira in 16S rRNA sediment clone libraries. On the other hand, several reductive dechlorinators were detected in sediments, including Dehalococcoides, Desulfitobacterium spp. which suggested that reductive dechlorination might be possible in sediments under certain biogeochemical conditions. Considerable amounts of PCBs were transformed by reductive dechlorination (80% in 177 days by pattern N) when sediments were maintained under anaerobic conditions, amended with nutrients and organic carbon, and incubated at 25 ºC in lab microcosms. Analysis of 16S rRNA clone libraries from these treatments revealed that Bacteroidetes, Chloroflexi and Firmicutes were enriched and Proteobacteria were depleted compared to clone libraries from treatment without organic amendments. Reductive dechlorination was decreased in sediments incubated at 10 and 40 ºC, and was not affected by FeSO4 amendments compared to unamended sediments incubated at 25 ºC. Transformations of PCB-153 were investigated in sediments under anaerobic, aerobic and sequential anaerobic and aerobic conditions. Transformations were only observed in treatments with an anaerobic phase, which occurred by reductive dechlorination by pattern N. Neither PCB-153 nor dechlorination products PCB-99 or PCB-47 were transformed under aerobic conditions. Analysis of 16S rRNA clone libraries revealed that Bacteoridetes, Chloroflexi, and Firmicutes were enriched under anaerobic conditions and Proteobacteria were enriched under aerobic conditions. Results from this study revealed that natural attenuation and biostimulation were not effective at removing PCBs from Ohio River sediments. Hence, other remediation methods will need to be employed to decrease PCB levels in this ecosystem.

For this study, we revisited whether the common iron Fe mineral, magnetite Fe3O4 (s), can reduce tetrachloroethylene (PCE) and trichloroethylene (TCE) as discrepancies exist in the literature regarding rates and extent of reduction. We measured PCE and TCE reduction in batch reactors as a function of magnetite stoichiometry (x = Fe2+/Fe3+ ratio), solids loading, pH, and Fe(II) concentration. Our results show that magnetite reacts only slowly with TCE (t1/2 = 7.6 years) and is not reactive with PCE over 150 days. The addition of aqueous Fe(II) to magnetite suspensions, however, results in slow, but measurable PCE and TCE reduction under some conditions. The solubility of ferrous hydroxide, Fe(OH)2(s), appears to play an important role in whether magnetite reduces PCE and TCE. In addition, we found that Fe(OH)2(s) reduces PCE and TCE at high Fe(II) concentrations as well. At certain conditions degradation of the PCE and TCE is enhanced by an unexplored synergistic response from magnetite and ferrous hydroxide iron phases. Our work suggests that measuring dissolved Fe(II) concentration and pH may be used as indicators to predict whether PCE and TCE will be abiotically degraded by groundwater aquifer solids containing magnetite.

Providing access to clean drinking water will continue to be a challenge for civil engineers for generations to come. Since many communities around the world rely on groundwater as a source of drinking water, remediation technologies must be implemented at sites where groundwater contamination exists due to years of mismanagement of hazardous waste. Using nanosized zero-valent metals such as iron and zinc embedded within and on the surface of functionalized (PAA) membrane filters has shown to be an effective dechlorination technique for contaminated groundwater. Introducing a noble metal such as Pd or Ni increases reaction rates by acting a catalyst for the dechlorination reaction. This study focuses on the treatment of contaminated groundwater at a hazardous waste site in Louisville, Kentucky. Once a chlorinated organic chemical manufacturing plant, the site now operates a treatment system for the contaminated groundwater to prevent migration into the nearby Ohio River. A portable membrane treatment system, built at the University of Kentucky, incorporates this functionalized bimetallic membrane technology for treatment of the groundwater found at the former manufacturing plant. Three bench scale tests were performed with membrane treatment system using DI water spiked with the chemical trichloroethylene (TCE). Results showed that using the functionalized Fe/Pd membranes significant decreased TCE concentrations over time. While further tests should be conducted to verify the results of the preliminary bench-scale tests, the membrane treatment system shows potential for use at the hazardous waste site in Kentucky.

<p>The disposal of combustible wastes by incineration is a controversial issue that is strongly debated by both scientists and environmental activists due to the resulting emissions of noxious compounds, including (<i>inter alia</i>) polychlorinated dibenzo-<i>p</i>-dioxins (PCDDs), dibenzofurans (PCDFs), heavy metals and acid gases like sulfur dioxide. Currently available air pollution control devices are capable of effectively cleaning flue gases, and PCDD/F emissions to air from modern municipal solid waste (MSW) incinerators are low. However, the PCDD and PCDF end up in ash fractions that, in Sweden, are usually deposited in landfills.</p><p>The European Union has recently set a maximum permitted total concentration of 15 µg TEQ/kg for PCDD/F species in waste. Fly ash from municipal solid waste (MSW) incineration containing PCDD/Fs at concentrations above this limit will have to be remediated to avoid disposing of them in landfills; an expensive and environmentally unfriendly option. Therefore, effective, reliable and cost-effective methods for degrading PCDD/F in fly ash are required, and a better understanding of the behavior of PCDDs and PCDFs during thermal treatment will be needed to develop them.</p><p>In the studies this thesis is based upon both the formation and degradation of PCDDs and PCDFs in ashes from MSW incineration were studied.</p><p>The main findings of the investigations regarding PCCD/F formation were:</p><p>- The concentrations of PCDD and PCDF in fly ash increased with reductions in the temperature in the post-combustion zone.</p><p>- The homologue profile in the ash changed when the temperature in the post-combustion zone changed.</p><p>- The final amounts of PCDD and PCDF present were affected by their rates of both formation and degradation, and the mechanisms involved differ between PCDDs and PCDFs.</p><p>The main findings from the degradation studies were:</p><p>- The chemical composition of ash has a major impact on the degradation potential of PCDD and PCDF.</p><p>- The presence of oxygen during thermal treatment can enhance the degradation of PCDD and PCDF.</p><p>- Thermal treatment is a viable option for degrading PCDD and PCDF in ashes from MSW.</p><p>- Shifts in chlorination degree occur during thermal treatment.</p><p>- Rapid heat transfer into the ash is a key factor for ensuring fast degradation of PCDD and PCDF.</p><p>- Degradation of other chlorinated organic compounds, e.g. PCB and HCB, also occurs during thermal treatment of ash.</p><p>- Reductions in levels of PCDD and PCDF were not solely due to their desorption to the gas phase.</p><p>- Differences between the behavior of 2378-substituted congeners of PCDD and PCDF and the other congeners during thermal treatment were observed.</p><p>- Differences in isomer patterns of both PCDD and PCDF were observed between the ash and gas phases after thermal treatment at both 300 and 500 oC.</p><p>Overall, the results show that the formation and degradation mechanisms of PCDDs differ substantially from those of PCDFs. Thus these groups of compounds should be separately considered in attempts to identify ways to reduce their concentrations.</p>