The technical and economical problems associated with sludge handling and disposal have significantly increased in the past years due to: (1) the introduction of more stringent water and air pollution regulations, often requiring the use of processes that produce large quantities of sludge as by-products; and (2) the development of regulations stipulating the means of ultimate disposal of sludge residues. These problems have resulted in a need for producing sludges with both good dewatering characteristics and low water content so as to minimize the ultimate volume of solids which must be disposed of. Recognizing the need for further work in this area of research, the objectives of this study were to examine the fundamental parameters which affect sludge dewatering characteristics. Included in this investigation were an analysis of both sludge dewatering and sludge handling characteristics. Parameters of interest were floe size, shape, and density, sludge viscosity and shear strength, and floc compressibility. The experimental investigation involved the collection of both water and wastewater sludge samples from full-scale treatment plants in the Commonwealth of Virginia. These samples were analyzed for each of the parameters previously mentioned; in addition, each was subjected to dewatering studies using laboratory-scale vacuum filtration, sanbed, and filter press equipment. The experimental results showed clearly that particle size distribution was a key parameter for describing the response of sludges to each of the dewatering methods utilized. For biological sludges, other factors such as biopolymer content were felt to have a major effect on dewatering characteristics. Sludge floc density was shown to have a direct correlation to the ultimate solids concentration obtained by vacuum filtration. Sludge handleability was conveniently evaluated through the use of the standard Atterburg liquid limit test procedure. Finally, the use of high-pressure filtration was found to provide much more appropriate information regarding water content than the centrifugation method proposed by Vesilind (1979). / Master of Science

An analysis of outdoor collector performance data collected as part of the NBS Durability/Reliability Test Program is presented. The data is analyzed for consistent patterns of performance degradation resulting from prolonged outdoor exposure at low flow rate and stagnation conditions. The analysis includes examination of the effects of pyranometer sensitivity changes with time and sensitivity dependence on temperature. Performance results are compensated for differences in test environments by use of an analytic correction routine. A statistical examination of the implementation of the testing procedure is made to identify interlaboratory differences. / Master of Science

This thesis contends that equipment replacement analysis should consider the implications of technological change since a like for like replacement is unrealistic with the current state of technological change. The major effects of improvements are a decrease in salvage value and opportunity expense of not implementing the latest innovations. The improvements appear as gradual changes and as major breakthroughs. Technological forecasting may be accomplished by several different methods including the Delphi method, analogy, and trend interpolation. A discussion of these methods and sources of information are given. The replacement model uses a future worth analysis, continuous discounting, discrete cash flows, a range of planning horizons, and incorporation of tax effects. The model was implemented using a BASIC program with graphics capability. The inputs are current year, initial cost of the equipment, the first years operating cost, regular tax rate, capital gains tax rate, depreciable life (as defined by the ERTA), rates of gradual change, number, dates and effect of major breakthroughs. A discussion of the sensitivity of the model to the various inputs is also given. / Master of Science

A mechanistic model was developed. to simulate apple orchard populations of the pine vole (Microtus pinetorum) in southwest Virginia. Population. size and demographic parameters were modeled on a weekly basis as functions of bioenerqetic status. Forage gross energy availability, digestibility, palatability, and preference were functions of Julian day. Daily energy budget (DEB) was a function of age, reproductive status, body weight, ambient temperature, and daily activity level. Energy acquisition was simulated assuming that consumption exceeded neither dietary energy demand nor a known maximum ingestion rate, and using linear programming to allocate forage class gross energy among competing vole classes. The 5 forage classes were queued by preference and consumed until all voles had fed maximally or forage was exhausted. Body weight and fat change were functions of age and energy restriction. Survivorship was a function of body fat balance, and probabilities of reproduction were functions of body fat balance and photoperiod. Animals were graduated between age and reproductive classes in a modified. Leslie algorithm by independent Bernoulli trial to avoid simulating fractional animals. Validation simulations suggested that dietary energy availability may limit pine vole populations in abandoned apple orchards, but not in maintained orchards. Simulation experiments suggested that pest populations of the pine vole in commercially maintained orchards may be controlled by a single control application in the fall achieving 80% mortality, or by 2 applications in the fall and spring achieving 50% mortality each. / Master of Science

Functional level modeling techniques for modeling digital devices that vary in complexity from SSI to LSI are described in this thesis. The vehicle used for modeling is GSP, a general simulation program developed under Dr. J. R. Armstrong at Virginia Tech. These techniques have been used extensively for modeling various devices which include counters, RAMs, ROMs, microprocessor peripheral chips and CPUs. Processors modeled include the Intel 8080, the Zilog Z80 (single chip CPUs) and the Bendix BDX930 (MSI). / Master of Science

A balance study was conducted for twenty-eight days on pregnant women consuming self-selected diets. Subjects were divided into the following groups: low zinc (9.98 ± 2.90, no supplement), high zinc (23.36 ± 2.59, on supplement), low nitrogen (below 10 gm/day) or high nitrogen (above 10 gm/day). Zinc and nitrogen data were determined from food, beverage and supplement intakes and urine and fecal excretions. Zinc retentions were 3.32 ± 6.33 in the supplemented group, 4.94 ± 10.91 in the non-supplemented group. Zinc retention in the nitrogen divided groups was -1.88 ± 9.43 for the group with intake above 10 gm/day, 4.26 ± 6.49 for the group with intake below 10 gm/day. No significant difference was found between the zinc supplemented group and the non-zinc supplemented group for either zinc or nitrogen retention. Nitrogen retentions were 2.42 ±. 2.17 mg/day for the zinc supplemented group and 3.53 ±. 3.29 mg/day for the non-zinc supplemented group. Nitrogen retention for the group with intake above 10 gm/day was 3.99 ±. 2.50 mg/day for the group with intake below 10 gm/day was 1.10 ±. 1.45 mg/day. Significant differences were found for nitrogen retention in the groups based on nitrogen intake. Higher nitrogen intake was associated with higher nitrogen retentions (p<.01). Significant differences were also found in zinc retention based on nitrogen consumption. Higher nitrogen intake was associated with lower zinc retention (p<.001). Plasma zinc was also measured. The mean plasma zinc was 70.46 ± 12.78 micrograms of zinc per 100 ml. The subject with the lowest zinc plasma level in the group also had a premature infant. / Master of Science

An improved formulation for radar backscatter from a volume of oblate spheroidal raindrops is developed, taking account of the beam elevation angle and the raindrop canting angle. The formulation is in terms of scattering coefficients in a matrix, and can be applied to systems using linear, circular, or elliptical polarization. The general formulation reduces to results previously published in the literature for linear polarization differential reflectivity (Z_DR) and for circular polarization depolarization ratio ( CDR). Analysis of the linear polarization case for a dual-polarization radar which can transmit and receive orthogonal linear polarizations in the horizontal-vertical (HV) planes, and the (±45) degree planes are considered. Results are presented showing the effect raindrop parameters have on Z , and linear polarization ratio (LDR) measured in (HV) and (±45°) planes. Analysis of the circular polarization case for a dual polarization radar which can transmit and receive circular polarizations is also considered. Results show that LDR measured in the (±45°) planes is similar to CDR. The dual-polarized radar development program at VPI&SU was discussed and a detailed design of a new radar data collection system is given. With the theory of dual-polarization radar measurement and the practical implementation of such a radar described within this thesis, a more accurate characterization of the propagation effects along a satellite to earth path can be carried out. / M.S.

The effect of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tertiary-butyl hydroquinone (TBHQ) and 8- hydroxyquinoline (8-0HQ) upon cell growth and spore germination of Clostridium botulinum type 62A was studied using a complex liquid medium. The inhibition of spore germination was further investigated using a defined liquid medium containing L-alanine, L-lactic acid and NaHC0₃. Cell growth was monitored by optical density (600 nm) increase and germination was monitored either by optical density (600 nm) decrease or by increase in percent phase dark spores viewed under phase contrast microscopy. Strict anaerobic conditions were maintained throughout the study. As the concentration of each chemical was increased the rate of germination or growth decreased. This occurred for each pH tested. GHA, BHT, TBHQ and 8-0HQ were more effective inhibitors of growth and germination as the pH was lowered from 7.2 to 5.7. At pH 7.2 50 µg/ml BHA, 200 µg/ml TBHQ and 200 µg/ml 8-0HQ were the minimum concentrations necessary for 90% inhibition of germination. BHT (400 µg/ml) inhibited germination by 65% at pH 7.2. Minimum concentrations at which growth at. pH 7.2 was inhibited by 95% were 60 µg/ml BHA, 20 µg/ml BHT, 250 µg/ml TBHQ and 20 µg/ml 8-0HQ. Inhibition of growth and germination by each chemical was found to be reversible with the exception of the inhibition of growth by BHT. / M.S.

Laboratory-scale settling units were used to determine the degree of treatment that could be achieved by sedimentation of stormwater runoff. Seven runoff samples were collected from shopping centers, which were selected because of their large impermeable surfaces resulting in high pollutant concentrations. The sampling sites were also representative of locations where detention basins would be constructed to control runoff flows and/or sediment loads. Approximately twenty liters of stormwater runoff were placed in each of four Plexiglas columns, and samples were withdrawn from column sampling ports immediately following sample addition, and after two, six, twelve, twenty-four, and forty-eight hours. The settling of the first runoff sample collected was terminated after only twenty-four hours. Sampling depths along the column, were either at one, two, and three feet, or at one, two, and four feet. Each sample was analyzed for total and volatile suspended solids, total and soluble Kjeldahl nitrogen, total and soluble phosphorus, orthophosphate, ammonia, oxidized nitrogen fonns (nitrites and nitrates), the particle-size distribution, and six heavy metals. Organic matter and total and fecal coliform bacteria were also measured but with less frequency. Dissolved oxygen measurements were made during settling of two of the seven experiments. Sedimentation reduced the concentration of most pollutants significantly, although pollutant concentrations composed mainly of soluble forms were not readily removed. Also examined was the use of settling data for determining particle removals in basin design criteria by the relationship between the reduction of particle surface area and various pollutants. The greatest majority of surface area in the runoff samples was associated with particles that were between 15 to 35 microns in diameter. / M.S.

The mechanisms controlling pillar load transfer from an overlying seam to subadjacent workings is investigated. Mine geometry and geology are researched as major variables affecting interaction between contiguously placed seams. The thesis includes photoelastic experimentation, finite element modeling, and analysis of multi-seam room and pillar mine case studies from the Appalachian region. A structured approach first establishes theoretically based trends, confirms their existence in the field, and finally results in invaluable multi-seam mine design guidelines. Stratification, lithology, and size of the interval between seams, and the extraction ratios of the seams are parameters found responsible for defining the stability of a lower seam overlain by either past or present mine operations. / Master of Science