Phytoremediation is an emerging green technology for the restoration of contaminated sites with various organic and inorganic contaminants. However, phytoremediation efficiency is limited by factors such as contaminant concentration, toxicity and bioavailability, plant choice and stress tolerance, and competence of indigenous microorganisms. A number of possible solutions have been proposed to overcome these limitations. The use of tolerant plant candidates, mixed plant communities and bioaugmentation with microbes and/or plant growth promoting bacteria (PGPB) have been proposed to suppress plant growth inhibition/phytotoxicity and enhance contaminant degradation through the rhizosphere effect but there is need for more research to understand their impact. This research assessed the impact of contaminant stress (diesel fuel, PAH; phenanthrene, fluoranthene and benzo[a]pyrene, and heavy metal) on selected plant species and microbial community structure, contribution of abiotic processes and rhizoremediation to PAH dissipation, and the impact of PGPB on plant growth and PAH dissipation. These objectives were achieved through greenhouse experiments with M. sativa, F. arundinacea and L. perenne on diesel fuel- and PAH-spiked soils. Diesel-fuel treatments had a negative impact on plant biomass yields while the single and mixed PAH treatments had stimulatory and inhibitory effects on plant biomass yields relative to the control.

acase@tulane.edu

No description available.

Spatial and temporal variation in inorganic contaminant concentration and distribution in a landfill leachate plume is examined to determine the mechanisms responsible for the observed variation, and to provide an assessment of the implications of this variation with respect to the interpretation of monitoring data, specifically with regards to its application to geochemical modelling. An integrated approach to field investigation was utilised in this study, including sample collection from a network of standard and bundled piezometers, surface and borehole geophysical investigation techniques, and a manometer board for the measurement of hydraulic head in bundled piezometers. Nine groundwater sampling events were conducted over a 12 month period, with sample analyses comprising field measurement of water quality parameters and redox sensitive elements, and laboratory analysis for major and trace elements and stable isotopes (??18O, ??2H, ??13C-DIC, ??15N). The vertical position of the centre of mass of the leachate plume was observed to vary up to 2 metres between monitoring events, and concentrations of key indicator parameters were observed to fluctuate by as much as 160%. The electrical images created by surface resistivity transects along a groundwater flow path between the landfill and a groundwater-fed pond a short distance downgradient suggest a plume configuration characterised by discrete pulses of concentrated leachate migrating in a conservative manner between the landfill and the pond. It is hypothesized that these leachate slugs are flushed into the aquifer during sustained periods of rainfall, presumed to be a significant driver of leachate mobilisation into the underlying aquifer. The most significant hydrogeochemical processes affecting contaminant mobilisation, transport and attenuation in the leachate-impacted shallow aquifer included microbial degradation of organic waste, dissolution of inorganic waste, ion exchange, precipitation of sulfide and carbonate minerals, mixing with rainfall recharge along flow path, and redox transformations along the plume fringe. These processes are supported by hydrogeochemical data analysis, and generally agree with the results of inverse geochemical modelling. While analysis of detailed groundwater monitoring appears to provide a plausible description of the plume dynamics, the results of the electrical resistivity transects indicates a more varied and complex plume configuration than is suggested by the borehole data alone. This integration of investigation techniques underscores the inherent inadequacy of even a high-resolution monitoring well network to accurately describe the full extent of variation in time and space within a contaminant plume, even in a relatively simple aquifer environment, and accentuates the potentially significant limitations of site-scale hydrogeochemical interpretation based solely on borehole monitoring data.

Thesis (M.Sc.)--University of Hong Kong, 1998. / Includes bibliographical references (leaf 71-73) Also available in print.

Arsenic in drinking water affects millions globally causing skin disease and cancers of the liver, stomach, and bladder. Large-scale treatment removes arsenic effectively; however, community- and home-scale treatments are typically less effective, more costly, or labor intensive. Nanomagnetite would enable effective, economical arsenic removal in low maintenance, household sand filters. Adsorption isotherms were used to display the As(V) capacity of nanomagnetite in a variety of natural waters and pH conditions. Column design and operating conditions were assessed for optimal removal. Breakthrough was most affected by nanomagnetite percentage, residence time, inlet concentration, and nanomagnetite aggregate size. NH4OH regenerated the nanomagnetite, allowing for repeated use. No detectable nanomagnetite escaped the column; however, permanent magnets were shown to capture >98% of nanomagnetite aggregates from a fluid stream. A case study proposes the use of nanomagnetite to treat arsenic contaminated groundwater in Guanajuato, Mexico to below the Mexican EPA drinking water standard for $0.23/m3.

Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. Tarek Abichou, Florida State University, College of Engineering, Dept. of Civil and Environmental Engineering. Title and description from dissertation home page (viewed June 21, 2004). Includes bibliographical references.

The key question this thesis aims to address is to what extent can micro-generation sources contribute to the carbon emission reduction targets set by the UK government. The operational emissions of micro-CHP capable micro-generators were examined against the UK grid electricity and gas boiler heat. Fossil and biomass fuels were considered. The life-cycle emissions associated with the manufacturing, transport and disposal of micro-generators were calculated. Case studies were constructed, based on the literature. It was found that emissions associated with domestic electrical and thermal demand would be reduced significantly. A Virtual Power Plant (VPP) was defined for aggregating micro-generators, using micro-generation penetration projections for the year 2030 from the literature. An optimisation problem was described, where the goal was to minimise the VPP carbon emissions. The results show the amount of emissions that would potentially be reduced by managing an existing micro-generation portfolio in a VPP. An Environmental Virtual Power Plant (EVPP) was defined, for controlling micro-generator carbon emissions. A multi-agent system was designed. The principle of operation resembles an Emissions Trading Scheme. Emission allowances are traded by the micro-generators, in order to meet their emissions needs. Three EVPP control policies were identified. Fuzzy logic was utilised for the decision making processes. Simulations were performed to test the EVPP operation. The main benefit for the micro-generators is the ability to participate in markets from which they would normally be excluded due to their small size. The multi-agent system was verified experimentally using micro-generation sources installed in two laboratories, in Athens, Greece. Two days of experiments were performed. Results show that system emissions have been successfully controlled, since only small deviations between desired and actual emissions output were observed. It was found that Environmental Virtual Power Plant controllability increases significantly by increasing the number of participating micro-generators.

This thesis reports on work carried out in the development of ultraviolet fibre-optic based absorption sensor systems, including those with the newly available ultraviolet improved silica fibres having low attenuation in the 200 nm to 250 nm wavelength region. Several approaches to optimize the optical design of such sensor systems, their sensitivity and stability are discussed. These fibre-optic sensor systems may be used for remote on-line and real-time analysis of process and water quality, enabling a separation of monitoring equipment from the sensor cell, which thus may be situated in a potentially hazardous environment. The effect of temperature variations on wavelength stability and dark output of inexpensive spectrometer modules, potentially useful for field applications, and the subsequent effect on the accuracy of absorption measurements, as well as the sensitivity of such spectrometer modules at wavelength below 250 nm, is investigated. Further, the performance of a remote fibre-optic sensor system, based on a reflectance cell with an optical pathlength of 1 cm, to measure nitrate concentrations in the wavelength region between 200 nm and 250 nm, is reported. Finally, to improve the sensitivity of such ultraviolet sensor systems, the performance of two fibre-coupled sensor cells with increased optical pathlengths has been investigated. The first sensor cell, based on an aluminium coated fused silica capillary cell, having an optical pathlength of 43 em, is demonstrated in the construction of a residual chlorine sensor. The second sensor cell, a capillary cell with an inner coating of Teflon AF, uses the low refractive index and the high transparency of Teflon AF in the ultraviolet to form a liquid-core waveguide (LeW). This sensor cell has an optical pathlength of 203 mm, extending the use of long pathlength cells to the 200 nm to 250 nm wavelength region. Its performance is illustrated when applied to monitoring low concentrations of nitrates, chlorine and acetylsalicylic acid.

In this work, an electrochemical method was developed to destroy liquid chlorinated solvents, and a thermochemical technique was invented to reduce gas-phase chlorinated solvents to hydrocarbons. The developed electrochemical method belongs to the most potential technique for wastewater treatment--only electrochemical method is possible to simultaneously destroy all water contaminants; the invented thermochemical method is the fastest way to destroy chlorinated solvents. In the first part of this work, the anodic oxidation of trichloroethylene (TCE) on an Ebonex ceramic electrode was investigated. TCE could be oxidized to CO₂, CO, Cl⁻, and ClO₃⁻. The disappearance of TCE was first-order, independent of pH, and initial TCE concentrations. TCE oxidation occurred only on the anodic surface and was limited by mass transport at Ea > 4.3 V vs SSCE ( i > 5 mA cm⁻²). Hydroxyl radicals generated on anode surface were detected using a spin trap. A kinetic model was successfully correlated with experimental results. In the second part of this work, TCE and CF were rapidly dechlorinated to hydrocarbons on the Ebonex ceramic cathode using Pt or Pd as catalyst. Pt was found to possess great resistance to sulfur and chlorine poisoning. Pd was quickly deactivated in sulfate solution. TCE and CF cathodic transformation were strongly dependent of pH. The reaction rate was limited by mass transport at Ec<-1.6 V (i > 5 mA cm⁻²). The mass transfer to cathode surface was found to be three times faster than to anode surface. The main products of TCE reduction were ethane, ethylene, and chloride, and for CF were methane and chloride. The proposed reaction mechanism and kinetic model were consistent with experimental results. In the third part of this work, a new hydrodechlorination method was invented for gas-phase chlorinated solvent destruction. Gas-phase chlorinated solvents, such as PCE, TCE, 1,1-DCE, VC, and CF were rapidly reduced to ethane, ethylene, and methane in a continuous-flow column reactor at ambient temperature and pressure. This is the fastest way to destroy chlorinated solvents. The catalyst could be easily regenerated and had a long-life time (over one and half year). The reaction mechanism and kinetics were studied. In the forth part of this work, the first three parts of work were combined together to invent a new destruction method for chlorinated solvents in real wastewater. Ebonex ceramic materials served as electrodes and Pt was plated on cathode used as catalyst in the electrolytic cell. The headspace of the electrolytic cell was connected to the Pd/Ni catalyst column. Liquid chlorinated solvents were destroyed on electrode surface, and gas-phase chlorinated solvents were reduced to hydrocarbons in the Pd/Ni catalyst surface in the presence of hydrogen. Water scale or other deposited materials on Pt coated Ebonex cathode could be removed, and the catalyst could be regenerated by reversing electrode polarity.