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Dissertations / Theses on the topic 'Recirculating'

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Published: 4 June 2021
Last updated: 19 February 2023

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1

Hall, Nicholas Martin Jerome. "Recirculating ocean gyres." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46326.

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2

Kinnear, David. "Magnetohydrodynamics of recirculating flows." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281668.

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3

Davidson, P. A. "Magnetohydrodynamics of swirling, recirculating flow." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383052.

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4

Thum, Tuck Foo. "Oxygen transfer in recirculating flow." Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45829.

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An experimental investigation was done on oxygen transfer into a laminar flow of whole blood and saline solutions downstream of an abrupt pipe expansion. This was used as the experimental model for regions of separated flow in the arterial system. The flow was fully-developed prior to the expansion with Reynolds numbers between 160 to 850. The results showed high transfer rates over most of the region downstream of the step, with maximum transfer occurring near the reattachment point. In addition, oscillations of the transfer rate were measured at the larger Reynolds numbers of 450 and 850.


Master of Science
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5

Nassiri, Masoud. "Numerical computation of shallow recirculating flow." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68046.

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The recirculating flows behind a sudden expansion in an open channel are computed using three different turbulence models: (i) a standard single-length-scale $ kappa$-$ epsilon$ model, (ii) a two-length-scale $ kappa$-$ epsilon$, and (iii) a constant-eddy-viscosity model. The performance of these models is evaluated by comparing the numerical results with the experimental data obtained from the previous investigation.
The flow simulation is characterized by two basic dimensionless parameters: a turbulent Reynolds number, $Re sb{T},$ which defines the level of eddy viscosity, and a bed-friction number, S, which represents the effect of bed friction. The study shows that in the limit of shallow water depth, that is S $>$ 0.10, the mean flow is quite successfully predicted by all employed models. However, in the limit of deep water depth, S $<$ 0.10, both $ kappa- epsilon$ models under-predict the length of the recirculating region due to the high level of computed eddy viscosity. On the other hand, the study indicates that the constant viscosity model gives quite acceptable results for most engineering applications.
Advantageously using the constant viscosity model's simple concept, an attempt is made to define a criterion for numerical stability of the computational procedure. The stability of the algorithm is assessed by varying the flow Reynolds number, the bed-friction number as well as the mesh size. The Courant number, a dimensionless parameter, is then introduced and correlated with the $Re sb{T}$ and S, thus providing the means to determine the stability of the numerical calculations.
As most of the recirculating flows observed in natural waterways are dominated by the bed-friction effect, accurate simulation of the mean flow field is possible even with an incorrect model for the lateral exchange process.
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6

Liu, Fang 1971. "Recirculating flow by video imaging method." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80124.

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The re-circulating region of the turbulent flow produced by a sudden lateral expansion in the width of an open-channel flow was study experimentally for the effect of bed friction on the flow. Dye was introduced into the recirculating region at a steady rate and the depth-averaged concentration of the dye was determined by the video imaging method. Instantaneous dye concentration images were recorded by a digital video camera. The advantage of video imaging method is its simplicity and its ability to acquire data over a large area of the turbulent flow at the condition when the lighting condition is highly non-uniform.
Experiments of the re-circulating flow were conducted over a range of water depth to study the friction effect on the transverse mixing by the horizontal turbulence. A series of four tests was carried out.
Mean concentration and root-mean-square concentration profiles were obtained at a number of cross sections along the flow in the open channel. The data were analysed for the length of the recirculating eddies, the width of the mixing layer, the width of the wake, and the dominant period of the flow oscillation. The dye concentration in the wake as an indicator of the mixing process by the horizontal turbulence, is a strong function of the bed-friction number. The results obtained from the present measurements have shown the friction effect on the horizontal turbulence to be far more significant than that was able to be detected by the previous investigation conducted in a smaller facilities using a light absorption probe.
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7

Kim, Carl Chong-Soo. "Geotechnical aspects of recirculating well design." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/44495.

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8

Tollervey, Alan. "Algal nutrient uptake in recirculating aquaculture systems." Thesis, Heriot-Watt University, 1985. http://hdl.handle.net/10399/1651.

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9

Nassiri, Masoud. "Two-dimensional simulation models of shallow recirculating flows." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0032/NQ64630.pdf.

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10

Tabatabaian, M. (Mehrzad). "Depth-averaged recirculating flow in a square depth." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65441.

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11

Bartelme, Ryan P. "Cultivating Ecosystems| Microbial Communities in Recirculating Aquaculture Systems." Thesis, The University of Wisconsin - Milwaukee, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10843723.

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Intensive cultivation of fish is necessary to meet future global market demands. Recirculating aquaculture systems (RAS) enable dense growth of fish, while occupying less space than traditional aquaculture farms. However, RAS often experience complications and high fish mortalities due to disease and improper waste management. In properly functioning systems, the microorganisms associated with fish (gut, scales) as well as those found in the system environment (water, component surfaces) remove waste and maintain fish health by discouraging growth of opportunistic pathogens. Previous RAS microbiome studies are small in scope, utilize coarse methods, and contain limited long-term spatial or temporal data. With advances in computation, microbial ecology, and RAS technology it is possible to test the relationship between RAS operational management practices and microbial community composition. Using the RAS at the UW-Milwaukee School of Freshwater Sciences, I used massively parallel DNA sequencing platforms, cutting-edge fluorescent microscopy, and classical molecular and microbiological methods to rigorously examine microbial community structures. Results from this dissertation advance our knowledge of aquaculture by analyzing RAS microbiota throughout the system over time; evaluate waste removal function, and track system condition correlations to pathogen blooms. These analyses will provide insight as to how environmental changes during rearing cycles affect system function and fish health. To investigate the connection of waste componentry failure to pathogen blooms, this dissertation uses Flavobacterium columnare as a model organism, since F. columnare infects fish across a myriad of freshwater systems. Genome sequencing of pathogenic F. columnare strains gives insight into the metabolic connections between fish waste and persistence of opportunistic pathogens. By better understanding the role of the microbiome in RAS, we can improve fish health, optimize waste removal, and increase yields and profits for aquaculturalists.

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12

Tsai, Cheng-Ying. "Investigation of Microbunching Instabilities in Modern Recirculating Accelerators." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77429.

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Particle accelerators are machines to accelerate and store charged particle beams, such as electrons or protons, to the energy levels for various scientific applications. There are three basic types of particle accelerators: linear accelerators (linac), storage-ring (or circular) accelerators, and recirculating accelerators. The third type, also the most recent one, is designed to accelerate a particle beam in a short section of linac, circulate and then continue to accelerate it for energy boost or decelerate it for energy recovery. The modern recirculating machines possess the advantages to both accelerate and preserve the beam with high beam quality, as well as efficiently reuse the accelerating components. As modern accelerators push toward the high-brightness or high-intensity frontier by demanding particles in a highly charged bunch to concentrate in an ever-decreasing beam phase space, the interaction amongst particles via their self-generated electromagnetic fields can potentially lead to coherent instabilities of the beam and thus pose significant challenges to the machine design and operation. Microbunching instability (MBI) has been one of the most challenging issues for such high-brightness or high-intensity beam transport, as it would degrade lasing performance in the fourth-generation light sources, reduce cooling efficiency in electron cooling facilities, and eventually compromise the luminosity of colliding beams in lepton or lepton-hadron colliders. The dissertation work will focus on the MBI in modern recirculating electron accelerators. The research attempts to develop a comprehensive theoretical formulation of MBI with aspects including among various degrees of freedoms the beam itself, the beamline lattice optics, and incorporation of all relevant collective effects that the beam encounters, for example the coherent synchrotron radiation (CSR) and the longitudinal space charge (LSC) effects. This dissertation includes the following seven themes: 1) Development and generalization of MBI theory to arbitrary linear lattices and coupled beams with constant and varying energies; 2) Construction of CSR impedance models from steady state to transient state and from high to low energy regime; 3) Numerical implementation of the developed theory as a fast and numerical-noise-free Vlasov solver and benchmarking with massive particle tracking simulation; 4) Exploration of multistage cascaded amplification mechanism of CSR microbunching development; 5) Control of CSR-induced MBI in multi-bend transport or recirculation arcs; 6) Study of more aspects of microbunched structures in beam phase spaces; and 7) Study of MBI for magnetized beams and confirming the suppression of MBI for a recent cooler design for Jefferson Lab Electron Ion Collider project.
Ph. D.
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13

Zhou, Xia Vivian. "A bioeconomic model of recirculating shrimp production systems." Master's thesis, Mississippi State : Mississippi State University, 2007. http://library.msstate.edu/etd/show.asp?etd=etd-07032007-161650.

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14

Le, Van Khoi. "Nutrient cycle in an integrated recirculating aquaculture system." Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/1916.

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Intensive marine aquaculture may cause negative impacts on the aquatic environment by causing water pollution, algae bloom and reduction in biodiversity of the surrounding aquatic environment. The nutrient-rich effluents from aquaculture activities contain nitrogen and phosphate which serve as a nutrient source for bivalve, algae and invertebrates. Seaweed and mussels have been integrated with marine species in culture systems to remove the waste from aquaculture farms. The research has explored the nutrient uptake capacities of green seaweed (Ulva lactuca) and blue mussel (Mytilus edulis) integrated with western king prawn (Penaeus latisulcatus) in the integrated closed recirculating aquaculture systems (IRAS) and has evaluated the nutrient retention of seaweed and animals in the system.One experimental unit of an IRAS consisted of three tanks: a mussel tank, a prawn tank and a waste-collection tank. The mussel tank and the prawn tank were set on the top and lower tiers of a metal frame; the waste-collection tank was on the floor. Water was pumped from the waste-collection tank to the reservoir tank by a submersible pump, circulated to the prawn tank and then returned to the waste collection tank through gravity.A series of experiments were conducted under laboratory conditions to investigate the water quality; survival, growth of western king prawn and nutrient budget in the IRAS. The research results proved that the recirculating culture system could maintain acceptable water quality for western king prawn at stocking densities till 16 prawn m-2 and at feeding rate of 3.0% of wet weight biomass. Increasing the stocking densities results in decreasing the water quality in the culture media, the growth and survival of western king prawn reared in the recirculating aquaculture system. In contrast, increasing feeding rate did not improved growth and survival rate of western king prawn but feed utilization efficiency decreased significantly with increasing the feeding rates. Total phosphorus (TP) and orthophosphate (PO43-) concentrations increased linearly with increasing the feeding rates of western king prawn. High percentage of nutrient inputs accumulated into tank bottom at higher stocking densities whereas over 50% of nutrient inputs were in discharged water at harvest in lower stocking densities.Inclusion green seaweed into western king prawn culture system improved the water quality in the IRAS. Concentrations of total ammonia nitrogen (TAN), nitrate (NO3-) and PO43- in the integrated culture system were lower than those in the monoculture system. Green seaweed effectively removed 24.02-99.05% TAN and 13.80-96.40% PO43- in the culture media. Feed utilization efficiency in integrated culture was significantly enhanced by 24.90 % nitrogen (N) and 19.41% phosphorus (P). Nutrient budget revealed that western king prawn and green seaweed retained 28.00-31.90% and 6.53-29.71% N of total nitrogen (TN) inputs at harvest, respectively while P retention was 13.46-14.63% and 1.62-13.50% of TP inputs, respectively. The rest of total nutrient input was in discharged water and tank sediments.Integrated culture of blue mussel and western king prawn could improve the water quality in the IRAS though effectively removing of the total bacteria (TB), total suspended solids (TSS) and total nitrogen (TN) in the cultured media. However, concentrations of NO2-, NO3- and PO43- were increased due to the mussel excretion. Growth and survival of western king prawn were not affected by adding blue mussels into western king prawn culture in IRAS at stocking rate of 250 mussel m-2 and 16.07 prawn m-2. When stocking rates exceed density of 312.5 mussel m-2 and =21.36 prawn m-2, growth and survival of both western king prawn and blue mussel in the IRAS were declined significantly due to the low water quality and crowded effects in the culture media. Inclusion of blue mussels into western king prawn culture was enhanced the feed utilization efficiency further up to 10.63 % N and 4.89 % P and reduced the nutrient discharged through draining at harvest. N and P contents accumulated in mussel tanks increased linearly with the increasing mussel stocking densities in the IRAS. The results indicate that the use of integrated aquaculture system is a step forward to achieve sustainability in aquaculture.
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15

Parker, Edward V. "Oxygen management at a commercial freshwater recirculating aquaculture system." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0032/MQ65513.pdf.

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16

McCoy, Kenneth A. "A recirculating optical loop for short-term data storage." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/14871.

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17

Gover, Marcus Paul. "Rich combustion and partial oxidation in heat recirculating burners." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47452.

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18

Montorio, Luca. "Assessment of a novel filter system for recirculating aquaculture." Thesis, University of Stirling, 2004. http://hdl.handle.net/1893/25419.

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The aim of this project was to investigate the usage of manganese dioxide ore as a bio-filter media to remove metabolites in aquaculture closed system, and to determine whether manganese toxicity would at the same time represent a risk to fish. Initial work investigated the physical properties of manganese dioxide and its chemical interaction with ammonia and nitrite in the absence of biological activity. Subsequently, two pilot-scale pressurised filters were installed in a commercial scale hatchery in order to compare the metabolite removal performance of manganese dioxide against silicate sand in the presence of biological activity commonly found in aquaculture conditions. The investigation suggests that Mn medium is more reliable in converting ammonia to nitrate without producing a residual output of nitrite. The superior performance ofMn media compared with sand appears to be mainly related to the physical structure of the manganese ore. Furthermore, the Mn medium did not appear to be soluble in the ambient conditions normally found in aquaculture-closed system. From the design point of view, due to the higher ammonia and nitrite removal rates, a shorter retention time and a lower volume of media are required in the case of manganese dioxide technology compared with sand media. As a result, it is much easier to size a biofilter with Mn media. Manganese systems have a comparable total costs to conventional sand media, but using the Mn technology provides a more reliable control of toxic nitrite, thereby reducing risks offish loss and hence with reduced expected production costs.
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19

Singh, Sahdev. "Modeling thermal environment of a recirculating aquaculture system facility." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-12302008-063343/.

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20

Newnam, Robert Pruett. "High Capacity Heat Exchangers for Recirculating 18F Radionuclide Production Targets." NCSU, 2007. http://www.lib.ncsu.edu/theses/available/etd-03212007-150136/.

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North Carolina State University in conjunction with Bruce Technologies Inc. is developing recirculating water targets for the cyclotron production of high yields of 18F fluoride for PET radiopharmaceuticals. Flourine-18 is commonly produced through proton irradiation of 18O enriched water by the 18O(p,n)18F reaction. Heat deposited in the target fluid by the proton beam is proportional to the 18F produced, thus production is often limited by the targets ability to reject heat. For power levels above 3 kW, boiling batch targets with local cooling can become impractical due to excessive 18O water volumes. One potential solution is a recirculating target system where the target water velocity is sufficient to prevent boiling. In this design the heated fluid travels through an external heat exchanger of sufficient capacity to remove the heat, and then through a pump which returns the cooled fluid to the target. A high-flow/low-volume pump and a high-capacity/low-volume heat exchanger are essential to the overall performance of the recirculating target. In this work, two different types of heat exchangers are considered. Laboratory testing was conducted on a small shell and tube heat exchanger that removed nearly 6 kW of heat at flows provided by a miniature regenerative turbine pump. Laboratory testing was also conducted on a small cross flow heat exchanger with measured performance of 7.4 kW and predicted peak performance approaching 10 kW.
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21

Torno, Johann [Verfasser]. "Innovations for nitrate removal in recirculating aquaculture systems / Johann Torno." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/117067500X/34.

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22

Yap, C. R. "Turbulent heat and momentum transfer in recirculating and impinging flows." Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384178.

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23

Guimpelson, Bronislav. "BWR coolant chemistry studies using a recirculating in-pile loop." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36949.

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24

Bst, Neil A. (Neil Andrew). "Preliminary design of a recirculating aquaculture system in Boston Harbor." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10275.

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25

Wood, Luther G. "Modeling effects of U-tube aeration in recirculating aquaculture systems." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-10312009-020150/.

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26

Emerman, Joshua David. "Establishing the optimal salinity for rearing salmon in recirculating aquaculture systems." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57067.

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Aquaculture of salmon worldwide is a 15.3 billion dollar industry and the majority of fish are produced in net-pen systems in coastal waters. Recently producers have begun investigating the feasibility of moving salmon production onto land and into recirculating aquaculture systems (RAS). The major downsides to RAS are the startup and operational costs; however the ability to optimize many environmental variables to enhance growth and feed conversion, something impossible to do in net-pen systems, may help defray these otherwise prohibitive costs. Salinity may be the most important of these variables due to the metabolic cost of osmoregulation, which has been estimated to account for 5-50% of routine metabolic rate. Decreased osmoregulatory costs could result in a greater allocation of energy toward growth, thus shortening production times and improving feed conversion efficiency. To establish an optimal salinity for growth in salmon, seven replicate, 15,000 liter RAS were constructed at the University of British Columbia’s InSEAS research facility. I conducted a preliminary study to validate that each system was able to control water quality parameters and yield similar levels of growth and feed conversion in coho salmon (Oncorhynchus kisutch). I then conducted salinity trials with Atlantic (Salmo salar) and coho salmon. Fish were grown in five salinities ranging from freshwater to seawater (0, 5, 10, 20, 30 ppt) for approximately five months. Growth rates and feed conversion ratios (FCR) were measured throughout the trial. The fastest growth rate and lowest FCR in coho salmon was at 10 ppt, which is approximately isosmotic to the blood. Growth rate of coho at intermediate salinities was almost double that at 0 or 30 ppt through the first growth period. This trend was not seen during the second coho growth period, possibly due to a size-dependent or density effect. Unexpectedly, salinity had no effect on growth rate and FCR in Atlantic salmon, although growth rates were consistent with those seen in industry. This research will help further move salmon production out of the oceans and onto land, alleviating some of the environmental costs associated with salmon grown in the oceans.
Science, Faculty of
Zoology, Department of
Graduate
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27

Pinilla, Camilo Ernesto. "Oscillation and friction effects on mass exchange in a recirculating flow." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99006.

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Experiments were conducted to study oscillation and friction effects on the mass exchange between the recirculating flow in a square basin and the main flow in an open channel. During the experiments, a turbulent mixing layer was observed to form between the recirculating flow in the basin and the main flow. Dye was introduced into the turbulent mixing layer as a tracer to observe the motion of the eddies. The concentration of the dye was measured using a video imaging method. The data were analysed for an early period shortly after the dye entered the basin, and a late period when the dye in the basin had reached a quasi-steady state. Parameters such as retention time, accumulation time and arrival time were estimated using the time series of the concentration in the core of the basin and in the region outside of the core. The circulation time and circulation flow rate were computed using the area occupied by the dye. The rate of increase in the area was equated to the circulation flow rate. The mean and root-mean-square dye-concentration profiles were obtained for a number of cross sections along the mixing layer. The flow in the mixing layer was observed to oscillate due to feedback from the impingement of the mixing layer on the downstream corner of the basin. The oscillation frequencies were determined by spectral analysis of the concentration data at a location in the mixing layer near the point of the impingement.
Tests were conducted for a range of Froude number varying from Fr = 0.09 to 0.47 and a range of bed-friction number from S = 0.023 to 0.27. Self-sustaining oscillations of the type known as "fluid-resonant feedback" were observed in the mixing layer. The onset of the oscillations in the mixing layer was detected to occur for a Froude number greater than 0.28. However, the mixing layer was not responsive to the feedback when the Froude number was less than 0.28. The dimensionless frequency of the oscillation was correlated with the Froude number. The Strouhal and Froude number relation analogously was consistent with the Rossiter's formula, which was developed for cavity oscillations in compressible flow. Beside the flow oscillations, the mixing layer and the recirculating flow in the basin were affected by the friction effect. Friction slow down the circulation in the basin. It changes the turbulence in the mixing layer. These effects of the friction were only significant when the water depth is sufficiently shallow. The dimensionless parameter for the friction effects was the bed-friction number. The demarcation of the flow between the deep and the shallow was found to occur at a bed-friction number S ≃ 0.09. The friction effect was negligible when the bed-friction number is less than the critical value of 0.09.
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Simon, John. "Using computer simulation to reduce costs at a recirculating aquaculture facility." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/42510.

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The Recirculating Aquaculture System can be considered as a dynamic system in which the system variables change instantaneously during the growing period. This effort uses a combination of discrete and continuous simulation to model this system. Changing the values of a certain set of variables (regressors) result in changes to another set of variables (responses). So the inter relationship between the regressors and responses are first defined. Then the changes to the regressors are defined as a function of time. The computer program then simulates time from the beginning to the end of the growing period. By attaching cost factors, the cost of running the system during the growing period can be obtained. In a real facility, some of the regressors can be changed by the operator, affecting the overall cost. So, in this model, different values for this subset of regressors are tried out using a proprietary heuristic called â Optquestâ to arrive at a low cost configuration. Some of the responses are also constrained while trying to minimize the cost, e.g., ammonia level. The output of the model gives a cost savings of about $10,000 over a period of 8 months for a facility with 12 tanks by suggesting optimal values for the water replenishment rate, water recirculation rate, oxygen supply rate and feeds per day.
Master of Science
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29

Martins, Marta Cecília Carvalho. "Bioremediation of phosphates in seawater: approach for recirculating marine aquaculture effluents." Master's thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/16067.

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Mestrado em Biotecnologia - Biotecnologia Industrial e Ambiental
Marine Recirculating Aquaculture Systems (RAS) produce great volume of wastewater, which may be reutilized/recirculated or reutilized after undergoing different treatment/remediation methods, or partly discharged into neighbour water-bodies (DWW). Phosphates, in particular, are usually accumulated at high concentrations in DWW, both because its monitoring is not compulsory for fish production since it is not a limiting parameter, and also because there is no specific treatment so far developed to remove them, especially in what concerns saltwater effluents. As such, this work addresses two main scientific questions. One of them regards the understanding of the actual (bio)remediation methods applied to effluents produced in marine RAS, by identifying their advantages, drawbacks and gaps concerning their exploitation in saltwater effluents. The second one is the development of a new, innovative and efficient method for the treatment of saltwater effluents that potentially fulfil the gaps identified in the conventional treatments. Thereby, the aims of this thesis are: (i) to revise the conventional treatments targeting major contaminants in marine RAS effluents, with a particular focus on the bioremediation approaches already conducted for phosphates; (ii) to characterize and evaluate the potential of oyster-shell waste collected in Ria de Aveiro as a bioremediation agent of phosphates spiked into artificial saltwater, over different influencing factors (e.g., oyster-shell pre-treatment through calcination, particle size, adsorbent concentration). Despite the use of oyster-shells for phosphorous (P) removal has already been applied in freshwater, its biosorptive potential for P in saltwater was never evaluated, as far as I am aware. The results herein generated showed that NOS is mainly composed by carbonates, which are almost completely converted into lime (CaO) after calcination (COS). Such pre-treatment allowed obtaining a more reactive material for P removal, since higher removal percentages and adsorption capacity was observed for COS. Smaller particle size fractions for both NOS and COS samples also increased P removal. Kinetic models showed that NOS adsorption followed, simultaneously, Elovich and Intraparticle Difusion kinetic models, suggesting that P removal is both a diffusional and chemically rate-controlled process. The percentage of P removal by COS was not controlled by Intraparticle Diffusion and the Elovich model was the kinetic model that best fitted phosphate removal. This work demonstrated that waste oyster-shells, either NOS or COS, could be used as an effective biosorbent for P removal from seawater. Thereby, this biomaterial can sustain a cost-effective and eco-friendly bioremediation strategy with potential application in marine RAS.
As atividades realizadas em Aquacultura Marinha de Recirculação (RAS) levam à constante produção de efluentes, sendo a maior parte reutilizados/recirculados ou reciclados depois de submetidos a diferentes métodos de tratamento/remediação, ou parcialmente lançadas em corpos de água vizinhos (DWW). Os fosfatos, em particular, são normalmente acumulados em altas concentrações em DWW, tanto porque a sua monitorização não é obrigatória para a produção de peixe, uma vez que não é um parâmetro limitante, e também porque não há nenhum tratamento específico até agora desenvolvido para removê-los, em especial no que diz respeito a efluentes de água salgada. Como tal, este trabalho aborda duas questões científicas principais. Uma delas diz respeito à compreensão dos métodos de (bio)remediação aplicados aos efluentes produzidos em RAS marinhos, identificando as suas vantagens, desvantagens e lacunas relativas à sua exploração nos efluentes de água salgada. A segunda é o desenvolvimento de um método novo, inovador e eficiente para o tratamento de efluentes de água salgada que potencialmente preenchem as lacunas identificadas nos tratamentos convencionais. Desse modo, os objetivos desta tese são: (i) rever os tratamentos convencionais aplicados para os principais contaminantes nos efluentes RAS marinhos, com especial incidência sobre as abordagens de biorremediação já realizados para fosfatos; (ii) caracterizar e avaliar o potencial de resíduos de concha de ostra colhidos na Ria de Aveiro como um agente de biorremediação de fosfatos em água salgada artificial, mediante diferentes fatores (e.g., prétratamento das conchas de ostra por calcinação, tamanho de partícula, concentração de adsorvente). Apesar das conchas de ostras já terem sido testadas na remoção de fósforo (P) em água doce, o seu potencial de biosorção de P em água salgada, tanto quanto eu estou ciente, ainda não foi avaliado. Os resultados demonstraram que as conchas naturais (NOS) são compostas principalmente por carbonatos, sendo estes praticamente convertidos em cal (CaO) após calcinação. Tal pré-tratamento permitiu a obtenção de um material mais reativo (COS) para a remoção de P, uma vez que se observou maiores percentagens de remoção e capacidade de adsorção. Frações de menor tamanho, tanto para NOS e COS, aumentaram a remoção de P. Os modelos cinéticos mostraram que NOS ajusta-se, simultaneamente, aos modelos de Elovich e de Difusão Intrapartícula, o que sugere que a remoção de P é um processo controlado tanto quimicamente como pela taxa de difusão. A percentagem de remoção de P em COS não é controlada por difusão e o modelo Elovich foi o que melhor se ajustou para a remoção de fosfato. Este trabalho demonstrou que os resíduos de conchas de ostra, quer NOS ou COS, podem ser usados como biosorventes na remoção de fosfato em água salgada. Desse modo, este biomaterial pode sustentar uma estratégia de biorremediação económica e amiga do ambiente, com potencial para aplicação em RAS de água salgada.
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30

Myers, Amanda R. ""Recirculating aquaculture system integration of bivalve culture for effluent nutrient composition reduction" /." Electronic version (PDF), 2006. http://dl.uncw.edu/etd/2006/myersa/amandamyers.pdf.

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31

Kodra, Bledar. "Risk Analysis of Tilapia Recirculating Aquaculture Systems: A Monte Carlo Simulation Approach." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/31845.

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The purpose of this study is to modify an existing static analytical model developed for a Re-circulating Aquaculture Systems through incorporation of risk considerations to evaluate the economic viability of the system. In addition the objective of this analysis is to provide a well documented risk based analytical system so that individuals (investors/lenders) can use it to tailor the analysis to their own investment decisions—that is to collect the input data, run the model, and interpret the results. The Aquaculture Economic Cost Model (AECM) was developed by Dr. Charles Coale, Jr. and others from the department of Agricultural and Applied Economics at Virginia Tech. The AECM is a spreadsheet model that was developed to help re-circulating aquaculture producers make strategic business decisions. The model can be used by potential producers interested in investing in re-circulating aquaculture through development of a financial analysis that in turn will help them obtain funding for the enterprise. The model is also useful for current producers who want to isolate inefficient aspects of their operation. AECM model consists of three major sections which include the Data Entry, Calculations and Analysis. The first section requires that the producer conducts background research about their operation to ensure accurate calculation and analysis. The calculation section provides a great deal of information about the operation's finances, while the analysis section provides information about the operation's financial stability. While the AECM is a powerful model, it is based on single, usually mean, values for prices, costs, and input and output quantities. However, market, financial and production uncertainties result in fluctuating prices, costs and yields. An individual who is making management decisions for a re-circulating aquaculture system will be faced with some or all of these uncertainties. By adding simulation to the AECM model to account for these uncertainties individuals will be able to make better management decisions. Information of the varying likelihoods or probabilities of achieving profits will be of crucial interest to individuals who plan on entering into or modifying an existing aquaculture system. Risks associated with six variables were examined in this paper: feed cost, feed conversion, mortality rate, capital interest rate, final weight, and output price. Data for the Interest Rate and output price were obtained from the Federal Reserve System and NMFS website respectively. Expert opinion was the source of data for the other variables. After probability distributions were applied to the random variables to account for the uncertainty the model was simulated for ten thousand iterations to obtain expected returns for three years in advance that the model calculates an income statement. In addition to that, sensitivity analyses were carried out in order to inform the producer which factors are contributing the most to the profitability of the operation. In this way the producer will have a better idea as to which aspects of the operation to monitor closely and consider modifying. The analysis shows that the mean income for the three years will be negative and thus the business would be losing money. The simulated mean net incomes were: -$216,905, -$53,689, -$53,111 for year1 through year3 respectively. Sensitivity analysis confirmed that output price is by far the most significant input that makes the overall bottom line to fluctuate most. Output price was on top of the list for all the three years analyzed in this study. Feed cost and Feed conversion were the next most significant inputs. The other inputs were also significant in explaining the fluctuation of the bottom line; however both their regression and correlation coefficients were small.
Master of Science
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32

Yates, J. Kevin. "Production economics of summer flounder Paralichthys dentatus aquaculture in a recirculating system /." Electronic version (PDF), 2004. http://dl.uncw.edu/etd/2004/yatesj/jkevinyates.pdf.

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33

Addasi, Deema. "Modeling of cod and bod at full-scale conventional and leachate recirculating landfills." Honors in the Major Thesis, University of Central Florida, 1995. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/136.

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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.
Bachelors
Engineering
Environmental Engineering
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34

Johnson, William P. "An investigation of the effects of ozone in a recirculating aquacultural production system." Thesis, Virginia Tech, 1991. http://hdl.handle.net/10919/41914.

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The use of ozone in a recirculating aquacultural production system on a commercial scale was investigated. ozonation was responsible for statistically significant differences in all test parameters, including: heterotrophic plate count, total coliforms, fecal coliforms, total solids, and total volatile solids. Results indicated ozone had a significantly positive effect in the recirculating aquacultural production system. Further study is recommended, however, to better understand the effects of ozone and to justify economically the use of ozone in commercial systems.
Master of Science

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35

Ardiansyah. "Efficacy of duckweed (Lemna minor Linnneus) integrated in barramundi recirculating aquaculture system (RAS)." Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/81910.

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Six experiments were conducted to evaluate nitrogen uptake capacities of duckweed in barramundi recirculating aquaculture systems (RAS). Harvesting duckweed every four days increased the abundance and diversity of both heterotrophic and phosphate-solubilising bacteria, and maximised nitrogen uptake efficiency. A stocking density of less than 18.75 kg m-3 is recommended for culturing barramundi in integrated RAS. The inclusion of fermented duckweeds up to 35% is feasible without adversely affecting growth and physiological parameters of barramundi.
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36

Flintoft, Mark John. "Optimising the use of Recirculating Well Pairs for the Determination of Aquifer Hydraulic Conductivity." Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2009. http://hdl.handle.net/10092/3453.

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Hydraulic conductivity (K) is a key parameter required for the accurate prediction of contaminant transport in an aquifer. Traditionally, pump tests, slug tests, grain size analysis and, to a lesser extent, tracer tests have been employed to estimate the K of an aquifer. These methods have disadvantages in respect to assessing the K of a contaminated aquifer, for example, pumping tests generate large quantities of potentially contaminated water, slug tests interrogate only a small portion of aquifer to generate K values, and tracer tests are costly to perform. The recirculating well pair (RWP) system, assessed in this study, attempts to minimise these disadvantages while producing accurate estimates of K. The RWP system uses two wells, each screened in two positions; one screen injects water and the other extracts water from the aquifer. One well extracts water from the lower screen and injects it into the aquifer via the upper screen, whereas the second well extracts water from the upper screen and injects it through the lower screen. When these two wells are pumped in tandem a recirculation system is created within the aquifer. No water is lost or gained from the aquifer in this system. Hydraulic conductivity can be estimated from a RWP system by either the multi dipole or the fractional flow methods. The multi dipole method estimates K by measuring steady state hydraulic heads, whereas the fractional flow method uses a tracer test to obtain steady state concentrations at the four screens to estimate K. Both methods utilise a 3D flow model to simulate the aquifer system. Inverse modelling in conjunction with a genetic algorithm simulate the hydraulic head values obtained from the multi dipole experiments or the tracer steady state values obtained from the fractional flow method. Hydraulic ii conductivity estimates are obtained by matching the simulated and observed steady state hydraulic head, or tracer steady state values. An investigation of the accuracy of the two RWP methods, when system parameters are varied, in estimating K values was undertaken. Five multi dipole experiments were undertaken with varying dipole flow rates to assess the effect of altering dipole flow rate on estimates of K. Two experiments were also undertaken to assess the effect of altering the pumping well incidence angle as compared to the regional flow on the accuracy of K estimates. Five fractional flow experiments were conducted, four to assess the effect of changing dipole pumping rates and one to assess the influence of altering the incidence angle of the pumping wells on estimation of K. All experiments were undertaken in an artificial aquifer that allowed control of hydraulic parameters and accurate measurement of aquifer K by independent methods. Experimental results were modelled with the two RWP methods. Results indicate that both the multi dipole and fractional flow methods provide accurate estimates of the K of the artificial aquifer (5 % to 57% greater than the actual K and -14% to 17% of the actual K, respectively). Altering the ratio between the pumping well and regional aquifer flow rates had no effect on the estimated K results in both methods. Although preliminary results were positive, further work needs to be undertaken to determine if changing the orientation of the well pairs affects the estimation of K.
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37

Abdel-wahab, Ahmed Ibraheem Ali. "The ultra-high lime with aluminum process for removing chloride from recirculating cooling water." Texas A&M University, 2004. http://hdl.handle.net/1969.1/446.

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Chloride is a deleterious ionic species in cooling water systems because it is important in promoting corrosion. Chloride can be removed from cooling water by precipitation as calcium chloroaluminate using ultra-high lime with aluminum process (UHLA). The research program was conducted to study equilibrium characteristics and kinetics of chloride removal by UHLA process, study interactions between chloride and sulfate or silica, and develop a model for multicomponent removal by UHLA. Kinetics of chloride removal with UHLA was investigated. Chloride removal was found to be fast and therefore, removal kinetics should not be a limitation to applying the UHLA process. Equilibrium characteristics of chloride removal with UHLA were characterized. Good chloride removal was obtained at reasonable ranges of lime and aluminum doses. However, the stoichiometry of chloride removal with UHLA deviated from the theoretical stoichiometry of calcium chloroaluminate precipitation. Equilibrium modeling of experimental data and XRD analysis of precipitated solids indicated that this deviation was due to the formation of other solid phases such as tricalcium hydroxyaluminate and tetracalcium hydroxyaluminate. Effect of pH on chloride removal was characterized. Optimum pH for maximum chloride removal was pH 12 ± 0.2. Results of equilibrium experiments at different temperatures indicated that final chloride concentrations slightly increased when water temperature increased at temperatures below 40oC. However, at temperatures above 40oC, chloride concentration substantially increased with increasing water temperature. An equilibrium model was developed to describe chemical behavior of chloride removal from recycled cooling water using UHLA. Formation of a solid solution of calcium chloroaluminate, tricalcium hydroxyaluminate, and tetracalcium hydroxyaluminate was found to be the best mechanism to describe the chemical behavior of chloride removal with UHLA. Results of experiments that studied interactions between chloride and sulfate indicated that sulfate is preferentially removed over chloride. Final chloride concentration increased with increasing initial sulfate concentration. Silica was found to have only a small effect on chloride removal. The equilibrium model was modified in order to include sulfate and silica reactions along with chloride in UHLA process and it was able to accurately predict the chemical behavior of simultaneous removal of chloride, sulfate, and silica with UHLA.
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38

Stoll, Christian Philipp [Verfasser]. "Beam dynamical behaviour of the MESA SRF structures under recirculating operation / Christian Philipp Stoll." Mainz : Universitätsbibliothek der Johannes Gutenberg-Universität Mainz, 2020. http://d-nb.info/1224896653/34.

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39

Hall, Antar Gamble. "A Comparative Analysis of Three Biofilter Types Treating Wastewater Produced in Recirculating Aquaculture Systems." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/30796.

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Nine recirculating systems at the Virginia Tech Aquaculture Center were placed on line and stocked with yellow perch, Perca flavescens, fingerlings. Fish were stocked at a density of approximately 455 fish m³. Biofilter types were the only factor differing among system designs and were an upflow pulsed bed bead filter, packed tower trickling filter and a rotating biological contactor (RBC). After stocking, systems were allowed to acclimate using ammonia excreted by the yellow perch. Following acclimation, a comparative analysis on biofilter performance began. To evaluate filter performance, water quality parameters tested were temperature (°C), pH, dissolved oxygen (DO), total ammonia-nitrogen (TAN), nitrite-nitrogen (NO₂⁻-N), nitrate-nitrogen (NO₃⁻-N), alkalinity (as CaCO₃), water hardness (as CaCO₃), carbonaceous biochemical oxygen demand (cBOD₃), dissolved organic carbon (DOC), and total suspended solids (TSS). Basic water quality analysis encompassed samples drawn at 8 AM. TAN mass removal analysis encompassed water quality samples drawn at 8 AM and over 24 hours. Higher TAN mass removal rates were achieved in trickling and RBC filters than in bead filters for 8 AM (0.037, 0.14, and 0.004 g/m²/d, respectively) and diurnal sample periods. Analysis of areas under mass removal curves depicted RBC filters as surface area limited. Trickling filters proved most effective at carbon dioxide stripping and pH maintenance and also effectively removed TSS from the culture water. The study did not show filter type as having a significant effect on median organic water quality parameter values.
Master of Science
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40

Phillips, Jennifer Brooke. "Denitrification of Recirculating Aquaculture System Waters Using an Upflow Biofilter and a Fermented Substrate." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/31068.

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The ability of an upflow, denitrifying biofilter using a fermentation generated carbon source to treat the high nitrate concentrations typically seen in recirculating aquaculture systems was studied using a synthetic nitrate wastewater supplied at two nitrate loadings, 1.13 and 2.52 kg NO3-N/m3/day. A supplemental carbon source was provided primarily through the fermentation of fish food which generated volatile fatty acids (VFA) in the form of acetic, propionic, isobutyric, n-butyric, 2-methylbutyric, 3-methylbutyric, and n-valeric acids. Acetic and propionic acids were the predominant constituents generated, while lower concentrations of the longer carbon chain butyric and valeric acids were produced. The VFAs proved to be a viable carbon source for the denitrification process as indicated by the ability of the biofilm to assimilate all of the constituents generated. Carbon limiting the system resulted in an increase in effluent nitrite and incomplete nitrate removal. During the low nitrate loading condition, influent COD to NO3-N ratios greater than 5 typically achieved high total nitrogen removals greater than 95%. This influent ratio corresponded with a COD to NOx -N consumption ratio of 4.62 ± 0.28 mg/L as COD per mg/L as N for complete nitrogen removal. Under the high nitrate loading condition, influent COD to NO3-N ratios achieving high nitrogen removals showed great variability and did not correspond to a distinct value. The COD to NOx -N consumption ratios were often below stoichiometric values, which was attributed to the hydrolysis of influent fermentation solids captured within the column to generate a COD source not measured by filtered samples. The column biofilm kinetics were modeled using a half-order reaction rate and denitrification coefficients (k) of 0.70 ± 0.02 (mg NOx-N/L)1/2 / min and 1.18 ± 0.12 (NOx-N /L)1/2 / min were determined for the low and high nitrate loading phases, respectively.
Master of Science
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41

Brazil, Brian Ligar. "Evaluation of an Effluent Treatment Strategy to Control Nitrogen From a Recirculating Aquaculture Facility." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/35413.

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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.
Master of Science
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42

Shank, Dale. "Evaluating carbon dioxide as a causative agent of otolith crystallization in recirculating aquaculture systems." Bowling Green State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1603716784275007.

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43

Stoneham, Tyler Robert Jeffery. "Development of Omega-3-Fatty Acid Enriched Finishing Feed and Value Added Tilapia Product." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/81383.

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Despite being a low fat fish and consequently a low omega-3 fish, tilapia have widespread consumer acceptability due to its mild taste, cheap price and low mercury content. However some sources claim that farmed tilapia can be detrimental to human health due to high omega-6:3 ratios and low omega-3 content specifically eicosapentaenoic acid, docosapentaenoic acid, and docosahexaenoic acid. The objective of this study was to create an omega-3 enriching feed that would increase omega-3 content in tilapia and subsequently decrease the omega-6:3 ratio. An 8 week feeding trial was conducted. Tilapia were cultured in a recirculating aquaculture system on one of eight diets (control, commercial, 1, 3, 5% fish oil or 1.75, 5.26, 8.77% ALL-G-Rich (algae). Water quality, selected fish biometrics and growth performance were recorded. Fillet and rib meat tissues were collected at weeks 4 and 8, and liver and mesenteric fat tissues were collected at week 8. Fat was extracted, trans-methylated and identified as fatty acid methyl esters using gas chromatography-mass spectrometry. Docosahexaenoic acid increased in concentration in all tissues as percent fish oil and ALL-G-Rich increased in the diets with 8.77% ALL-G-Rich resulting in significantly (P<0.0001) greater concentrations in the fillet and mesenteric fat compared to all other diets after 8 weeks. The 8.77% ALL-G-Rich diet resulted in significantly (P=0.003) greater cumulative accumulation of EPA, DPA and DHA on a mg/4oz fillet basis after 4 weeks compared to control. The results of this study suggest that an ALL-G-Rich finishing feed could be produced that would result in a value added farmed tilapia fillet.
Master of Science in Life Sciences
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44

Al-Wazzan, Yousef Jassim Easa. "The prediction of swirling recirculating flow and the fluid flow and mixing in stirred tanks." Thesis, Imperial College London, 1997. http://hdl.handle.net/10044/1/8329.

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45

Holliman, James Bret Adrian John. "An economic analysis of integrating hydroponic tomato production into an indoor recirculating aquacultural production system." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Fall/Theses/HOLLIMAN_JAMES_4.pdf.

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46

Nunley, Chad E. "Production of hybrid striped bass (Morone chrysops x Morone saxatilis) in a recirculating aquaculture system." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-08222009-040454/.

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47

Steinberg, Kathrin [Verfasser]. "Accumulating substances and their effects on pikeperch (Sander lucioperca) in recirculating aquaculture systems / Kathrin Steinberg." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1169132588/34.

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48

Marquis, Andrew James. "The application of high order convection approximations and second order turbulence closures to recirculating flows." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38095.

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49

Cabral, Paul Richard. "Development of design curves for recirculating well technology : Massachusetts Military Reservation Chemical Spill 10 plume." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43364.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1997.
Includes bibliographical references (leaves 80-83).
by Paul Richard Cabral.
M.Eng.
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50

Cloran, Christina Elizabeth. "Investigating Nickel Flux and Toxicity in Clay Sediments with Batch and Stream Recirculating Flume Experiments." Wright State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=wright1229973400.

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