Browsing by Author "Degen, Marcia J."
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- Denitrification in low pressure distribution onsite wastewater disposal systemsDegen, Marcia J. (Virginia Tech, 1992-12-05)The effects of effluent type, effluent loading rate, dosing interval, and temperature on denitrification in low pressure distribution, on-site wastewater treatment and disposal systems (OSWTDS) were evaluated in this study. The treatments were surface and subsurface soil horizons; nitrified and non-nitrified wastewaters; 0.5, 1.0, and 1.5 times the Virginia Department of Health (VDH 1989) recommended wastewater loading rate; 24 and 48 hour dosing intervals; and summer and winter temperatures. Surface and subsurface soil cores were collected from a Groseclose silt loam soil (clayey, mixed, mesic Typic Hapludult) and subjected to the various treatments. The effects of the treatments on denitrification were evaluated based on analyses of leachate from the cores, soil chemical analyses, and microcosm studies to estimate actual denitrification activity. A model was developed from the study that estimated the mean N₂O production for each combination of experimental treatments. The results of the study and the model indicate that denitrification can be enhanced in OSWTDS by the application of non-nitrified wastewater at one-half the VDH recommended loading rate, or 1.25 cm/day, for surface soil horizons (30 min inch⁻¹ percolation rate) using a 48 hour dosing interval. A field study was conducted on a Lowell silt loam soil (fine, mixed, mesic Typic Hapludalf). Denitrification was measured at this site using acetylene blocking and the results compared to those predicted by the denitrification model developed from the laboratory data. The field measurements of denitrification based on N₂O concentration in the soil atmosphere were three orders of magnitude higher than that predicted by the model. It was concluded that the laboratory techniques can be used to determine optimum method of operation for denitrification in a low pressure distribution system, but it cannot be used to determine the field design loading rates.
- Evaluation of the potential environmental toxic effects of a nylon fibers additiveDegen, Marcia J. (Virginia Tech, 1985-01-15)New chemical substances being considered for use today are required by law to be evaluated for potential toxic effects upon disposal to the environment. A thorough evaluation, however, is complex, time-consuming, expensive, and impossible to perform on each new substance. In this study the potential toxic effects of a new carpet additive with antimicrobial properties and the associated process waste stream from a textile facility were considered. The wastewater from the rest of the plant was currently being treated in a land application disposal system. An assessment of the toxicity of the antimicrobial additive was made using conventional greenhouse studies. This assessment was compared to the results obtained from three short-term toxicity tests performed on the same set of solutions. The short-term tests used were a corn seedling bioassay, adenosine triphosphate measurements, and bacterial bioluminescence. These short-term tests were evaluated as to their utility as screening tools and as monitoring devices for toxic substances.