Showing papers by "Joseph R.V. Flora published in 2008"

Evaluating alkaline microcapsules for pH control and reductive dechlorination of trichloroethylene in sediment

Abstract: Near neutral pH has been reported in the literature to optimise trichloroethylene (TCE) reductive dehalogenase activity in purified enzyme solutions, cell extracts and cell suspensions. In this study, microencapsulated alkaline buffers were used to evaluate potential use in controlling pH in soil microcosms and columns containing sediment obtained from a TCE-contaminated acidic aquifer at the Department of Energy's Savannah River Site (SRS). Batch microcosm tests were performed to determine the effect of pH on TCE degradation at different set points (4.0, 5.5, 7.0, 8.5, 10.0). Maximum vinyl chloride (VC) production occurred at a pH of 4 (p < 0.001), which is approximately the groundwater pH at the site. Although more nutrient uptake occurred at all other pH levels, indicating that general microbial activity was greater under less acidic conditions, TCE metabolite production was not maximised at neutral pH. Other factors, such as a small population of active dechlorinators, may have limited reductive dechlorination in the SRS sediment.

Kinetics of Acidic Macrocapsules in Controlling the pH of Groundwater

Abstract: The effectiveness of novel acidic macroencapsulated buffers in controlling pH was evaluated in batch experiments and through detailed mathematical modeling. When exposed to a high pH solution, the macrocapsules decreased the pH to 7.5. A batch model accounting for detailed chemical equilibria was developed and used to extract the macrocapsule release kinetics within a simulated annealing algorithm. The model predicted the change in pH of the batch solutions well. The batch model was incorporated within a two-dimensional mathematical model coupling transport (convection/dispersion) and fate (including chemical reactions) of chemical species and chemical equilibrium to study the potential use of the macrocapsules in controlling pH of the groundwater in a horizontal field domain. The model was used to simulate three scenarios (reaction throughout a domain with subsequent release of base equivalents, reaction within a reactive layer with a constant release of base equivalents, and a combination of the first t...

Mercury Speciation in Coal-Fired Power Plant Flue Gas-Experimental Studies and Model Development

Abstract: The overall goal of the project was to obtain a fundamental understanding of the catalytic reactions that are promoted by solid surfaces present in coal combustion systems and develop a mathematical model that described key phenomena responsible for the fate of mercury in coal-combustion systems. This objective was achieved by carefully combining laboratory studies under realistic process conditions using simulated flue gas with mathematical modeling efforts. Laboratory-scale studies were performed to understand the fundamental aspects of chemical reactions between flue gas constituents and solid surfaces present in the fly ash and their impact on mercury speciation. Process models were developed to account for heterogeneous reactions because of the presence of fly ash as well as the deliberate addition of particles to promote Hg oxidation and adsorption. Quantum modeling was used to obtain estimates of the kinetics of heterogeneous reactions. Based on the initial findings of this study, additional work was performed to ascertain the potential of using inexpensive inorganic sorbents to control mercury emissions from coal-fired power plants without adverse impact on the salability fly ash, which is one of the major drawbacks of current control technologies based on activated carbon.