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Étang-sur-Arroux, France

Barrut B.,ARDA | Blancheton J.-P.,French Research Institute for Exploitation of the Sea | Champagne J.-Y.,Ecole Centrale Lyon | Grasmick A.,Montpellier University
Aquacultural Engineering | Year: 2012

A study was undertaken to measure the water flow (Q w) delivered by a vacuum airlift designed for recirculating aquaculture systems (RAS) in fresh (<1‰ of salinity) and sea water (35‰ of salinity). The vacuum airlift consists of two concentric tubes connected at their top to a depression chamber. The water rises in the inner tube as a result of air being injected in its lower section and flows back through the external downcomer tube. The vacuum airlift was adjusted at three different lengths: 2, 4 or 6m and water discharge could be lifted from 0 to 30cm. Air flow rate (Q g) varied from 0 to 80Lmin -1. Different types of air injectors were tested, delivering different bubble sizes (0.1-5mm) depending on porosity and functioning at low or high injection pressure. Results show an increase in water flow when pipe length and air flow were increased and lift height reduced. Water flow also depended on the type of water and ranged from 0 to 35 m 3h -1 (0-580Lmin -1) for fresh water and only from 0 to 20 m 3h -1 (0-330Lmin -1) for sea water (for a 6m high vacuum airlift). This difference was attributed to the smaller bubble diameter and higher gas holdup (e{open} g) observed in sea water (0-20%) compared to fresh water (0-10%). When bubbles were present in the downcomer tube, they created a resistance to flow (counter-current airlift) that slowed down liquid velocity and thus water flow. Increasing the vacuum made it possible to use low air injection pressures and high injection depths. Vacuum also increased bubble size and airflow (20Lmin -1 at atmospheric pressure to 60Lmin -1 at 0.3barA) and thus water flow rates. With RAS, the presence of fish feed in water rapidly increased water flow delivered by the airlift because of changes of water quality and gas holdup. When working with low head RAS (under 0.3m), vacuum airlift could save up to 50% of the energy required for centrifugal pumps. An empirical predictive model was developed and calibrated. Simulation shows a good correlation between predicted values and measurements (R 2=0.96). © 2011 Elsevier B.V. Source


Barrut B.,ARDA | Blancheton J.-P.,French Research Institute for Exploitation of the Sea | Champagne J.-Y.,Ecole Centrale Lyon | Grasmick A.,Montpellier University
Aquacultural Engineering | Year: 2012

In aquaculture, oxygen transfer and carbon dioxide stripping are the first limiting factors to fish rearing intensification. In this study we measured the O 2 and CO 2 mass transfer coefficient (K La) for a vacuum airlift in fresh (<1‰ salinity) and sea water (35‰ salinity) recirculating aquaculture systems (RAS). The airlift was composed of two concentric tubes: an inner riser tube and an external downcomer tube and can be adjusted at three different heights: 2, 4 or 6m. Several types of air injectors were tested, delivering different sizes of bubble swarms depending on their porosity and functioning conditions (low or high injection pressure), with air flows varying from 0 to 80Lmin -1. Experiments were also carried out at different water circulation velocities and with cold (7°C) and warm water (22°C). The best transfer coefficient (K La) value was obtained at a high air flow rate, a high temperature and with reduced bubble size. Results showed that K La was not affected by water salinity, but it was slightly affected by water flow (Q w), airlift inner pipe length and vacuum. The presence of vacuum reduces gas solubility in water and facilitates CO 2 stripping. The comparison between O 2 and CO 2 transfers showed that higher K La values were obtained for O 2 than for CO 2 in fresh and sea water, probably due to chemical reactions between the CO 2 and water. For RAS, the vacuum airlift provides a Standard Aeration Efficiency (SAE) of 1.13kgO 2kWh -1 and a Standard Stripping Efficiency (SSE) of 1.8kgO 2kWh -1 or 0.023kgCO 2kWh -1. In rearing water, CO 2 and O 2 transfers were negatively affected when feed was added. An empirical model for CO 2 mass transfer coefficient prediction was developed and calibrated. Simulation shows a good correlation between predicted and measured values (R 2=0.87). © 2011 Elsevier B.V. Source


Barrut B.,ARDA | Blancheton J.-P.,French Research Institute for Exploitation of the Sea | Muller-Feuga A.,Microphyt | Rene F.,French Research Institute for Exploitation of the Sea | And 4 more authors.
Bioresource Technology | Year: 2013

Low-energy and low-cost separation of microalgae from water is important to the economics of microalgae harvesting and processing. Flotation under vacuum using a vacuum gas lift for microalgae harvesting was investigated for different airflow rates, bubble sizes, salinities and harvest volumes. Harvesting efficiency (HE) and concentration factor (CF) of the vacuum gas lift increased by around 50% when the airflow rate was reduced from 20 to 10Lmin-1. Reduced bubble size multiplied HE and CF 10times when specific microbubble diffusers were used or when the salinity of the water was increased from 0‰ to 40‰. The reduction in harvest volume from 100 to 1L increased the CF from 10 to 130. An optimized vacuum gas lift could allow partial microalgae harvesting using less than 0.2kWhkg-1DW, thus reducing energy costs 10-100 times compared to complete harvesting processes, albeit at the expense of a less concentrated biomass harvest. © 2012 Elsevier Ltd. Source


Taillebois L.,French Natural History Museum | Keith P.,French Natural History Museum | Valade P.,ARDA | Torres P.,French Natural History Museum | And 3 more authors.
General and Comparative Endocrinology | Year: 2011

After oceanic migration, post-larvae of the amphidromous Sicyopterus lagocephalus recruit to rivers in Reunion Island. As they enter the river mouth, post-larvae undergo many morphological, physiological and behavioural changes. These drastic changes, which allow them to change feeding regime and to colonise the juvenile and adult freshwater habitat, are defined as metamorphosis. The endocrine control of these changes has never been investigated in Gobioid fish. Here, we investigated whether thyroid hormones (TH) influence metamorphosis in recruiting S.lagocephalus. An analytical study was first performed on a cohort of 2400 fish caught at post-larval stage 1 and maintained for 37days after capture in a flume tank (fluvarium), which replicates as closely as possible the natural conditions. Biometrical parameters (total and standard lengths, corner of mouth angle, body mass and condition factor) and whole-body thyroxine (T 4) and triiodothyronine (T 3) contents were measured on fish, sampled at regular intervals during these 37days (192 fish). TH levels, measured by radioimmunoassays, were highest when morphological changes, such as the change in the position of the mouth, were most important. An experimental approach was then used to test the effect of the hormonal treatment (T 4 or thiourea, TU, a TH inhibitor) on biometrical parameters of 576 post-larvae. The change in the position of the mouth was significantly accelerated in the T 4-treated post-larvae, while it was significantly delayed in the TU-treated post-larvae, compared to controls. Our study suggests that S.lagocephalus post-larva undergoes a true metamorphic event under the control of thyroid hormones at the time of its recruitment into the river. © 2011 Elsevier Inc. Source


Barrut B.,ARDA | Blancheton J.-P.,French Research Institute for Exploitation of the Sea | Callier M.,French Research Institute for Exploitation of the Sea | Champagne J.-Y.,Ecole Centrale Lyon | Grasmick A.,Montpellier University
Aquacultural Engineering | Year: 2013

The accumulation of particulate organic matter (POM) in recirculating aquaculture systems (RAS) has become an important issue with the intensification of finfish production. The objective of this study was to assess the foam fractionation efficiency of a vacuum airlift in different conditions (POM concentrations, airflow rates, bubble sizes, water renewal rates and feed addition). In sea water, the vacuum airlift allowed removing 20% of the initial POM concentration per hour (foam fractionation efficiency), corresponding to a 20.7-fold concentration factor between the tank and the foam. In rearing conditions, efficiency increased with decreasing water renewal rate or increasing POM concentration. An increase in airflow rate from 10 to 80Lmin-1 in the vacuum airlift significantly decreased foam fractionation efficiency when feed was added to the water. The impact of feeding was only observed with high airflow rates where bubble coalescence occurred. Calculated POM production by fish ranged between 15.9 and 23.5gh-1 and was equivalent to estimations based on feed conversion ratio (FCR). This indicated that all the POM produced was extracted by the vacuum airlift. © 2012 Elsevier B.V.. Source

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