Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 98-102). Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 129-131). Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 107-118). Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 123-137). Also available via the Internet.

The process wastewater from three blue crab processing plants in Virginia was characterized. Most of these effluent streams were highly concentrated. For example, the retort water from the cookers exhibited the following concentrations: BOD₅ = 14,000-29,000 mg/L, TSS = 650-6,200 mg/L, TKN-N = 2,500-4,000 mg/L, NH3-N = 70-160 mg/L and Total Phosphorus= 100-185 mg/L. One process effluent contained chloride concentrations exceeding 100,000 mg/L. Analysis of production and effluent characterization data from two mechanized plants revealed that wastewater volumes and concentrations varied significantly between the two plants. Both plants exhibited highly variable daily and seasonal production. Treatability studies were completed on the process wastewater because discharge limits exist for TSS, Oil and Grease and in some cases BODs and ammonia. Settling and filtration studies were performed on these effluents. The organics and nutrients in the wastes were highly soluble and limited reduction of COD (18-65% reduction), BOD₅ (9-49% reduction), TKN-N (9-62% reduction), and TP (10-66%) was achieved by filtration. Acidification of the concentrated effluents caused some coagulation of the contents. Coagulation by pH adjustment was most effective between pH 3.0-4.0. TSS removals of 76- 93%, and BOD5 removals of 6-30% were achieved by pH adjustment, thereby showing promise as a pretreatment method. Anaerobic biological treatment systems appear promising for the treatment of wastewater from blue crab processing plants (effluent BOD₅s ranged from 150-420 mg/L), especially for cooker effluent. However, there is concern that salt from the Harris Claw operation will decrease anaerobic treatment performance and that effluent NH3 and TSS levels will need to be further reduced to meet permit limits. Pretreatment of process wastewater by means of pH adjustment did not improve anaerobic treatability. / Master of Science

Wastewater from the pressure cooking of blue crabs presents a difficult treatment challenge. COD concentrations in the range of 15,000 to 30,000 mg/L are found in this wastewater, with TKN concentrations above 2,000 mg/L. Direct discharge of the wastewater, which is currently allowed, adds nutrients to the Chesapeake Bay, and potentially creates local DO depletion in receiving waters. Anaerobic treatment of this wastewater was studied for the reduction of COD. Nitrification was studied for the conversion of ammonia, present at levels above 1,000 mg/L NH3/NHA4-N, to nitrate for possible denitrification. COD reductions averaging above 11,000 mg/L were found to occur in an upflow anaerobic filter operating with less than a 4 day HRT. Further COD reduction in the aerobic reactor resulted in a final effluent averaging 2,400 to 3,100 mg/L soluble COD with a corresponding BOD₅ of 110 to 340 mg/L. Nitrification proved to be inhibited, perhaps by the high levels of NH₃/NH₄-N in the effluent from the anaerobic stage. Nitrification did occur in a batch study, but only after extended aeration, and depletion of BOD. Non-degradable COD was estimated to be 2,900 mg/L in the anaerobic effluent. Monod model kinetic coefficients for the anaerobic stage were determined on a degradable COD basis to be: k = 0.68 day⁻¹, Ks = 3,500 mg/L (degradable portion), Y = 0.19, and Kd = 0.028 day⁻¹. The effect of the addition of certain trace metals (Fe, Ni, Co, Mo) to the feed was investigated. There was no improvement in COD removal performance, and slight inhibition may have occurred. / Master of Science

The dehydration rates of crabs during low temperature storage and various cooking processes were determined. Season, cooking time, and cooking method significantly affected the weight loss of crabs. The thermal energy (F250 ) crabs received during a commercial cooking process was evaluated by season, cooking method and time, and crab type. The effects of sex, size, and type (sexual maturity) of crab and season on the yields of lump, top flake, bottom flake, and claw and total meat were examined. The effects of cooking time and method and storage time on meat yield was also determined. During summer, male crabs yielded more lump, claw, and total meat than female crabs, and clean female crabs yielded more lump, top flake, and total meat than sponge female crabs when retort cooked for 10 minutes. / Ph. D.

Master of Science

In recent years, the blue crab fishery has become the main source of income for Virginia's watermen. This fact, along with growing concerns of overharvesting and uncertainty about the amount of effort in the fishery, has led to calls for more complete data on the fishery. This study examined the characteristics of Virginia's blue crab fishery, through an extensive survey of crab pot license holders conducted on a monthly basis from March to November of 1992. Along with a description of the people in the fishery, this study also modeled prices, harvest levels, and income levels for the blue crab industry. Because the models were interactive in nature, the effects of various fishery management strategies were also analyzed. The main emphasis of the policy simulations was to discover what impacts the different strategies had on harvest and income levels. The results of the simulations showed that many of the policies currently under consideration will have only a small impact on overall harvest and income levels, but there are some larger distributional effects among different firm classes. The findings of this study suggest that in order to gather accurate and useful data on the fishery, the random surveying techniques of this study should be continued over a period of years. / Master of Science