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Browsing by Author "Brazil, Brian Ligar"

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    Evaluation of an Effluent Treatment Strategy to Control Nitrogen From a Recirculating Aquaculture Facility
    Brazil, Brian Ligar (Virginia Tech, 2001-10-04)
    The ability of a self-contained denitrification system, using fermentation products from waste fish solids, to maintain reliable performance was studied. Denitrification performance was described kinetically and stoichiometrically under different initial nitrate-nitrogen and soluble organic carbon to nitrate-nitrogen ratios. Characterization of soluble organic carbon (measured as soluble chemical oxygen demand, sCOD) indicated that volatile fatty acids (VFA) were generated during the fermentation of the waste fish solids. The results from batch experiments showed that over the range of initial nitrate concentrations studied, complete denitrification was achieved within 6 hrs. sCOD, nitrite, and nitrate profiles across several batch experiments showed that transient nitrite accumulations occurred, but the maximum measured concentrations never completely inhibited nitrate removal. The results suggested that the rate of denitrification was influenced by the initial sCOD to nitrate-nitrogen ratio when transient nitrite concentrations remained below 20 mg/L. However, when nitrite-nitrogen exceeded 25 mg/L, the rate of denitrification was negatively correlated with the maximum measured nitrite-nitrogen concentration. The stoichiometric carbon requirement was not correlated to any parameters believed to influence carbon consumption. After complete denitrification was achieved residual sCOD was still measured, which could not be identified as VFAs. Batch aerobic treatment of denitrified effluent resulted in a 60 to 70 % removal of the residual sCOD when allowed to react for 8 days. It was further determined that the residual sCOD exerted an oxygen of 5.81 on g COD/g C. Additional studies were conducted to maximize sCOD production during fermentation. Increasing the fermentation temperature from 28 oC to 40 oC facilitated a 36 % increase in the specific sCOD production rate (g sCOD/ g fish solids applied). In addition to sCOD production, ammonia production increased 20 % when the fermentation was conducted at the elevated temperature. An analysis comparing the cost of methanol addition to support denitrification to the cost associated with fermenting waste fish solids indicated that supplementing fermentation products with methanol resulted in the least costly strategy for promoting denitrification of an aquaculture waste stream.
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    Impact of Ozonation on System Performance and Growth Characteristics of Hybrid Striped Bass (Morone chrysops (f) x Morone saxatilis (m)) Reared in Recirculating Aquaculture Systems
    Brazil, Brian Ligar (Virginia Tech, 1997-10-04)
    This study was conducted to evaluate the impact of sustained ozone dosages rates (0, 3, 13, 25, and 45 g O₃ per kg feed delivered per day)on water quality profile, fish physiology, and growth during a production cycle of hybrid striped bass reared in pilot scale recirculating systems. Nitrogenous wastes and dissolved organic compounds increased linearly (p < 0.01) throughout the trial under both ozonated and unozonated conditions. Ozone treatments 13 and 25 g O₃ / kg feed received 170 kg more feed than the control treatment (0 g O₃ / kg feed) by the end of trial. The ozonated system received an average 1 kg more feed per day than did the unozonated system, although the unozonated system received 25% more freshwater during the trial. Ozonation increased nitrification efficiency which resulted in a 25% reduction in residual ammonia measured per kilogram of feed delivered. Biologically degradable organics (CBOD5) were lowered 45% under ozonation when adjusted for daily feed input. Microbial activity as determined by the rate of degradation of DOC was 43% higher in the ozonated environments. Increased environmental quality provided through ozonation did not result in measurable physiological improvements (p 0.05). All parameters monitored except plasma protein and hematocrit values varied significantly (p>0.05) over time. Hemoglobin, plasma protein, and hematocrit values in fish under all rearing conditions were 10.2 ± 0.4 g/dL, 7.1± 0.6 g/dL, and 52.9 ± 1.9%, respectively. Final mean serum chloride level of 115.8 ± 3.4 mE/L and mean glucose level of 186.3 ± 2.1 mg/dL were measured in fish reared at treatments 0, 13, and 25 g O3. Fish reared under ozonated conditions possessed an overall mean growth rate of 2.3 g/day and FCR of 1.58:1. Simultaneously, fish in the unozonated environment gained 1.8 g/day at an FCR of 1.90:1. At the conclusion of the trial, the final mean weight (443 ± 11.6 g) of fish reared in the unozonated environment was significantly lower (p<0.01) than fish reared in the ozone treatments 13, and 25 g O3 (combined mean of 576.6 ±16.4 g).