Browsing by Author "Burgos, William David"
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- Laboratory evaluation of conditioning requirements for sludge dewatering using belt filter pressBurgos, William David (Virginia Tech, 1990-12-06)The purposes of this study were to develop a reliable bench-scale testing procedure to adequately predict polymer conditioning requirements for full-scale belt filter presses, and to determine the additional polymer demand exerted by applied pressure during the expression stage of a dewatering process. Bench-scale experiments performed with anaerobically digested, alum, and secondary sludges used a high-speed mixer to gauge mixing intensity effects, and a wedge zone tester to gauge applied pressure effects on conditioning requirements. Full-scale experiments varied Sludge throughput, belt speed, and polymer dose to evaluate polymer performance. The polymer requirements to optimize performance of a full-scale belt filter press can be predicted with a bench-scale mixing device, where the shear (Gt) of the mixer matches that of the full-scale press. An estimate of the Gt value of the full-scale belt filter presses used in this study was 10,000. Alternatively, a bench-scale wedge zone tester, operated in an applied pressure range between 5 psi and 20 psi, can predict polymer doses for optimum belt filter press performance. The range of applied pressures used to simulate the expression phase of a dewatering process did not exert a Significant additional polymer demand for optimum conditioning. The shear (Gt) associated with mixing sludge and polymer during conditioning can exert a greater polymer demand than the expression phase of the wedge zone tester.
- Reversible and irreversible adsorption of naphthalene and α-naphthol to soilBurgos, William David (Virginia Tech, 1995-05-03)Experiments were performed with naphthalene and a-naphthol to compare the processes involved in the sorption of a polycyclic aromatic hydrocarbon (PAH) and its metabolite, respectively, and to assess the bioavailability of these two compounds adsorbed to two sandy soils with different organic carbon contents. Adsorption conditions were varied to estimate the extent that biologically-mediated and chemically-induced oxidative coupling, and rate-limited diffusive processes contributed to the apparent irreversible adsorption of these compounds. The purposes of this research were to: (1) investigate the processes which cause the irreversible adsorption of organic contaminants to soil~ (2) gauge the impact that these different adsorption processes have on the bioavailability of sorbed contaminants; and, (3) evaluate the environmental significance of these processes in soils and the subsurface. This dissertation has been prepared as three separate articles for publication in peer reviewed journals. The first article serves as a literature review in evaluating the significance of oxidative coupling reactions in soil and subsurface environments. This review concludes that oxidative coupling of organic contaminants may be important in soils and could be stimulated as a viable remediation strategy. For subsurface systems oxidative coupling appears much more limited, however, engineered systems could be developed to enhance this process. The second article presents experimental results used to quantify the individual processes involved in the irreversible adsorption of naphthalene and a-naphthol. This article concludes that both biological and chemical catalysts are important in promoting irreversible adsorption reactions, and that once the partial oxidation of a PAH occurs, oxidative coupling can become a significant process affecting contaminant fate. The third and final article examines the effect of different adsorption processes on the subsequent bioavailability of sorbed naphthalene and anaphthol, and concludes that the biodegradation of naphthalene and α-naphthol adsorbed to both the soils tested was controlled by the rate of desorption and the reversibility of the adsorption process.