Constraints on Energy Intake in Fish: The Link between Diet Composition, Energy Metabolism, and Energy Intake in Rainbow Trout

The hypothesis was tested that fish fed to satiation with iso-energetic diets differing in macronutrient composition will have different digestible energy intakes (DEI) but similar total heat production. Four iso-energetic diets (2×2 factorial design) were formulated having a contrast in i) the ratio of protein to energy (P/E): high (HP/E) vs. low (LP/E) and ii) the type of non-protein energy (NPE) source: fat vs. carbohydrate which were iso-energetically exchanged. Triplicate groups (35 fish/tank) of rainbow trout were hand-fed each diet twice daily to satiation for 6 weeks under non-limiting water oxygen conditions. Feed intake (FI), DEI (kJ kg−0.8 d−1) and growth (g kg−0.8 d−1) of trout were affected by the interaction between P/E ratio and NPE source of the diet (P<0.05). Regardless of dietary P/E ratio, the inclusion of carbohydrate compared to fat as main NPE source reduced DEI and growth of trout by ∼20%. The diet-induced differences in FI and DEI show that trout did not compensate for the dietary differences in digestible energy or digestible protein contents. Further, changes in body fat store and plasma glucose did not seem to exert a homeostatic feedback control on DEI. Independent of the diet composition, heat production of trout did not differ (P>0.05). Our data suggest that the control of DEI in trout might be a function of heat production, which in turn might reflect a physiological limit related with oxidative metabolism

Modélisation d'un bioréacteur à membrane vraie grandeur en utilisant le modèle ASM1 : problèmes et solutions

International audienceA full-scale membrane bioreactor (1600 m3.d-1) was monitored for modelling purposes during the summer 2006. A calibration of the ASM1 model is presented; the wastewater characterisation, the aeration and the biomass kinetics were principally investigated. Total BOD tests were not able to correctly estimate the biodegradable part of the wastewater entering the bioreactor, but by adjusting simulation results to the measured sludge production, the wastewater fractionation was identified and MLVSS accurately predicted. However, MLSS could not be correctly simulated as the consumption and production of mineral suspended solids is not considered by the model. The membranes are immerged in the aeration tank leading to several combinations of coarse bubble and fine bubbles systems, running alone or together (five different configurations). The oxygen transfer rates estimated in a previous work were inserted in the model and the comparison of the simulated oxygen concentrations with the two sensors signals were satisfying considering the very low DO concentrations (0.6mgO2.L-1 on average). The biomass kinetics were studied using maximum nitrification rates and an 8-hour calibration campaign of intensive sampling. A new set of parameters for ASM1 (heterotrophic and autotrophic biomass kinetics and half saturation coefficients) was identified and a common anoxic value for the heterotrophic growth yield (YH, anoxic) was adopted. Despite simultaneous nitrification and denitrification in the aeration tank, the results of the calibrated model showed good agreement with the measured NH4+-N and NO3--N outlets

Guide technique opérationnel : Pratiques d'échantillonnage et de conditionnement en vue de la recherche de micropolluants prioritaires et émergents en assainissement collectif et industriel

L’opération de prélèvement en rejets canalisés (assainissement collectif, rejets industriels), dans le cadre de recherche et quantification de micropolluants, est une étape qui nécessite des précautions particulières. Elle conditionne les résultats d’analyses et donc les conclusions de démarches techniques et scientifiques. Suite à un premier état des lieux fin 2008, des groupes de travail ont été créés pour proposer des protocoles adaptés, applicables sur le terrain, pour les différentes étapes d’une opération d’échantillonnage : l’homogénéisation mécanique, la nature et le nettoyage des matériaux spécifiques, les blancs de prélèvement, l’utilisation d’échantillonneurs automatiques déjà en place (ex. stations d’épuration, sites industriels). Ce document détaille les recommandations opérationnelles relatives aux précautions nécessaires lors de l’échantillonnage quand il s’agit de rechercher les micropolluants. Ce document rappelle ou précise également certaines opérations corollaires ou de préparation à ce type de prélèvement, ainsi que les précautions de sécurité les plus importantes, en vue d’une application plus systématique sur le terrain

Modélisation d'un bioréacteur à membrane vraie grandeur avec le modèle boues activées ASM1 : défis et solutions

International audienceA full-scale membrane bioreactor (1600 m3.d-1) was monitored for modelling purposes during the summer of 2006. A complete calibration of the ASM1 model is presented, in which the key points were the wastewater characterisation, the oxygen transfer and the biomass kinetics. Total BOD tests were not able to correctly estimate the biodegradable fraction of the wastewater. Therefore the wastewater fractionation was identified by adjusting the simulated sludge production rate to the measured value. MLVSS and MLSS were accurately predicted during both calibration and validation periods (20 and 30 days). Because the membranes were immerged in the aeration tank, the coarse bubble and fine bubble diffusion systems coexisted in the same tank. This allowed five different aeration combinations, depending whether the 2 systems were operating separately or simultaneously, and at low speed or high speed. The aeration control maintained low DO concentrations, allowing simultaneous nitrification and denitrification. This made it difficult to calibrate the oxygen transfer. The nitrogen removal kinetics were determined using maximum nitrification rate tests and an 8-hour intensive sampling campaign. Despite the challenges encountered, a calibrated set of parameters was identified for ASM1 that gave very satisfactory results for the calibration period. Matching simulated and measured data became more difficult during the validation period, mainly because the dominant aeration configuration had changed. However, the merit of this study is to be the first effort to simulate a full-scale MBR plant